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spalm
11-29-2005, 11:50 PM
Well I am starting the build of my machine #3. I have always been intrigued with V-bearings, so I bought a couple of sets and plan to give them a go. I will give ply/MDF one more try. I am itching to mill aluminum, so am hoping that this machine will give me the strength to do it.

I kind of started this log (http://www.cnczone.com/forums/showthread.php?t=14702&page=1&pp=15) before, but it digressed into epoxy and suchnot. This project will probably take a little while as I want to test and change as it goes along. I have been thinking about it for months now, and I have decided on a 24” x 40” with about 4” of Z.

I am going to try to get rid of the support of the gantry under the bed. This means that the gantry will have to be stiff. It will probably take a couple of tries to get it acceptable. It will be stiffer than the drawing suggests. This also means running the X leadscrew on the side. This in turn may lead to dual leadscrews, which will be a new adventure for me.

Comments always welcome,
Steve

spalm
11-29-2005, 11:51 PM
I built the Y beam and test fitted it with a piece of scrap for the Z carriage. It is really stiff yet slides with ease. All 4 bearings have eccentrics installed for adjustment.

I used some old pieces for the internal support web, just to add some memories to the evolution of this build.

There are holes drilled though for threaded rod to attach to the gantry walls. I also plan to add dowels after final placement.

Steve

ViperTX
11-30-2005, 01:57 AM
So, why do you need dual scews for the x-axis.....go down the center and save yourself some headaches...

tobytorkn
11-30-2005, 04:26 AM
steve, where did you get the bearings, and slides? how much? i built my cnc using the rollers for sliding screen doors. it has very little slop, but your rollers look better made. thanks for the help. toby....

Rance
11-30-2005, 06:43 AM
Viper, The pivot point of any axis is the lead screw by which that axis is driven, so if you're only gonna have one, then by having it closer to your router bit should give you better accuracy. Interesting diversion Steve, I like it.

spalm
11-30-2005, 01:16 PM
Tobytorkin, I bought the bearings from the Zone’s own imserv at
http://www.cadcamcadcam.com but they are really from SuperiorBearing.

They are not the cheapest way to go, but I am really impressed with them. They are built for taking this kind of abuse. There is an eccentric collar that slips into the bearing and then a 1/4” bolt passes through this collar for mounting. As you twist the collar you can change the bearing pressure against the rail. I can not think of an easier adjustment scheme.

The X axis to me is the long axis. I think Viper is referring to the X while Rance is referring to the Y. (?)

Viper, I hear ya. I could just float the bed in the air and send a cross beam under the gantry to get to a center leadscrew mount ala JGRO. Since I am kind of playing here, I guess I want to try to push it and get rid of that box. My plan is to try the short gantry first and see what kind of racking I get, and then make a decision on going under the bed, adding a second leadscrew, or leaving it as is (preferred).

Rance, I hope I can take advantage of the space under the Y beam for it’s leadscrew since the rail and bearing already hang down about 2”. I think this is a good mechanical connection to the router as well.

The Y rails are 3/4” and the X rails are 2” angle iron.

Steve

ger21
11-30-2005, 01:46 PM
Well I am starting the build of my machine #3.

Did you finish #2? :)

spalm
11-30-2005, 03:24 PM
(I hope you are not talking baby potty talk to me :D )

Hmmm…. Finish? It runs and cuts well, just looks kind of crude. Rather than prettying it up, I wanted to try this. I still get to steal a few parts from #2.

Attached pics from #2.

BTW, have you finished yours? :stickpoke

Steve

spalm
12-01-2005, 11:43 PM
Started making the X axis. Got the MDF beams cut and holes marked for support for the angle iron. Yea for sawsall, it cut the 2” angle like butter.

Made a test piece out of scrap to prove the hole locations for the bearings. I was really disappointed at first. I am cheating and using skate bearings on the bottom of the angle. When I first ran the assembly back and forth, it wanted to tilt in at the middle and then tilt out at the edges of the rail. I just went back into the shop to take pics to show you the problem, but I seemed to be able to fix it by running it back and forth a bunch of times and by loosening the bearing pressure a bit. Not sure if it will be a future problem or not.

What is angle iron coated with? I constantly get black dust every time I touch it. I guess the bearings are wearing it down. Is it some kind of cheap paint or maybe anodized? Can I paint over it without completely removing it?

Steve

2muchstuff
12-01-2005, 11:52 PM
That coating is from the manufacturing process. It is a slag type (black) oxide from the metal being hot rolled or formed. Unless you grind it off it will continue to flake off. If you leave it on you might have to roll those bearings over it a million times or so to wear it down.

Rance
12-02-2005, 07:05 AM
Yep, I was referring to the 'Y' axis.

Steve, one thing to keep in mind is that the taller angle you use, the less stable it will be. Have you considered going down to maybe 1" or less? Actually, you still need the 2" side to bolt it to the table so do they make 'L' iron (2"x1")?

ger21
12-02-2005, 09:17 AM
BTW, have you finished yours? :stickpoke

Steve

I wasn't sure you had actually finished it. :)

I can see the light at the end of the tunnel. Another coat of paint on the gantry parts tonight, and I'll start final assembling next week.

whateg01
12-02-2005, 09:42 AM
...so do they make 'L' iron (2"x1")?

You can have any color you want as long as it's black. ;)

I don't know about 1x2, but I know I have some 1.5x2x.25 angle at home, so it is likely somebody makes it. It's probably just a matter of how much do you want to pay to find it. Actually, 1x2 seems a bit odd, but then again, you never know what you might find.

Good luck.

Dave

spalm
12-02-2005, 10:28 AM
Rance, I have been having the size of rail debate with myself for quite a while. (I hate debating myself, but I do it way too much.) Yes, it seems like a 2” x 1” (or .5”) rail would be the best. 2” for mounting and 1” for rail. I actually had convinced myself that a taller rail would be more stable because the bearings were more spread apart. Now I don’t think so, and I see you agree. I think this will still work, but I really need to control the C shaped gantry from any parallelogram’ing.

On another note, I was talking to some coworkers about how strong angle iron was. Anyway, we googled angle iron bending and got the following pics. I had no idea that you could do such things. Then again, there is a lot that I have no idea about.

Steve

whateg01
12-02-2005, 01:36 PM
Anyway, we googled angle iron bending and got the following pics. I had no idea that you could do such things. Then again, there is a lot that I have no idea about.

Steve

Steve,
Angle is malleable just like most other steel. It just takes the right tooling. Angle iron's main weakness (IMHO) is its lack of torsional rigidity. However, if one leg is held fixed, it should be well suited for low-tech applications like this. (THK gods would probably strike me down if I didn't include the low-tech blurb. :cool: )

You are correct with the thought that spacing the two bearing surfaces farther apart will decrease the effect that any play has on the system. That is simple physics. Doing so should also reduce the stress on the bearings. You can spread the bearing surfaces simply by filling in the space between the, in this case, angle iron with a slab of MDF or otherwise providing externally the necessary rigidity.

Something else worth mentioning is that while I do not know how widely available 1x2x? is, and I would suspect that you would want at least 3/16" thickness, I do know that 1.5x2x.25 is pretty easy to get, and in that thickness should be plenty rigid when mounted to something else.

Dave

spalm
12-05-2005, 12:03 AM
Well, good news and bad news.

Good news: I finished the X beams and mounted the angle iron. I clamped the beams to a table and drove my test gantry over it by hand. Looking real good. Thanks for the help Dave, I sanded the angle iron and the black dust has disappeared. Plan to paint the rails later for show. It slides right nicely. I really like the way the Y travels. All initial testing has shown that this is superior to the wrap-around Y carriage that I came up with for machine #2. There is no front/back tilt and it should be much simpler to construct a carriage for the Z. The adjustments are simpler than the bearing plate thingy. I am sticking with this.

Now for the bad news. Did a lot of testing. The gantry racks terrible. I was concerned with parallelogram’ing or that the gantry could tilt left to right. Not a problem, the combination of the bearings and the Y torsion box seemed to take care of this. The problem I have is the gantry twisting. If I lock the left side, the right side can be moved front to back +/- .25”. I removed the gantry to the bench and repeated this test. It is defiantly caused from the 3/4” ply not having sufficient torsion strength. It is amazing (to me) how much it can twist. I clamped (not as good as gluing) a second sheet of ply for a total of 1.5” and got virtually the same result.

So now what to do. The gantry walls need help. Lengthening them while floating the bed and having a box underneath would help, but I really don’t want to do this. So strengthening them is my first choice. I guess it comes down to three things: torsion box sides, aluminum, or a better choice of wood.

Steve

whateg01
12-05-2005, 01:42 AM
Steve,

I'm glad the angle iron will work for you. Regarding the sides of the gantry, you're right that clamping is not as good as gluing. When you clamp, you essentially have two thinner pieces side by side. When glued, you effectively have a single thick piece. A torsion box does the same thing as adding thickness but without the weight of a single piece the same thickness. The quick fix, glue a couple of pieces of plywood together. This should stiffen it up quite a bit, if that is, in fact, where the flexing is at. I don't know whether MDF or particleboard would be stiffer or not. I'm sure it would be heavier.

One thing that might help is a piece of 1/4" aluminum plate bolted/screwed to the side. I think aluminum cutoffs that I buy run about $1.50/#, so that would be a little over $5/sq. ft.

Just my 2.5 cents.

Dave

paulC
12-05-2005, 03:00 AM
Would it be possible to add a glue block in each corner of the torsion box?
Adds a lot of strength when used on wooden joints.
Paul

Rance
12-05-2005, 08:03 AM
Steve, are the V bearings rated for both axial AND radial loads? You are using both on them from what I can determine.

ger21
12-05-2005, 09:11 AM
Steve, would the problem be solved by dual lead screws, or is it moving side to side?
With any luck, I'll be putting assembling my gantry this weekend, and I'll let you know if I get similar results. But I'm using dual screws to keep mine from moving.

spalm
12-05-2005, 10:09 AM
Rance, yup they are built for this kind of stress, radial and axial. They are termed double row angular contact bearings meaning they have two rows of bearings.

Dave and Gerry. I am sure that what I am seeing is the twist of the gantry side. I originally was hoping that the bearings would stop this. Not so. I am pretty sure that dual leadscrews would mask the problem, but I would like to do what I can before I go that route.

My testing went something like this. I removed the bearings from the three piece gantry and clamped one side down low to my table saw fence. I then pushed the far side back and forth and noted the amount of movement. In order to find out where it was coming from, I clamped long sticks to the top and bottom of the side and also the box. These acted like pointers on a dial. I could tell that the gantry side to box joint was not failing, and that the gantry side was twisting. It was kind of neat.

Since I have some kind of repeatable testing jig now, I am thinking that I will repeat this with several thicknesses of ply, MDF, etc. and actually note the amount of movement. Maybe with a fish scale to note applied force. Kind of a flex-o-meter.

I wish I could find a local source of scrap aluminum.

Steve

whateg01
12-05-2005, 10:49 AM
Dave and Gerry. I am sure that what I am seeing is the twist of the gantry side. I originally was hoping that the bearings would stop this. Not so.
You know what they say about the weakest link.



I am pretty sure that dual leadscrews would mask the problem, but I would like to do what I can before I go that route.
Sometimes the best thing you can do is to design an entire system. Knowing each area's deficiencies, you can design other parts to counter them, so that as a whole it works. I have read other posts that indicate the center leadscrew is very susceptible to this type of problem. The only ways that I know of to eliminate the problem is to make everything very rigid or to use 2 leadscrews.



My testing went something like this. I removed the bearings from the three piece gantry and clamped one side down low to my table saw fence. I then pushed the far side back and forth and noted the amount of movement. In order to find out where it was coming from, I clamped long sticks to the top and bottom of the side and also the box. These acted like pointers on a dial. I could tell that the gantry side to box joint was not failing, and that the gantry side was twisting. It was kind of neat.

Since I have some kind of repeatable testing jig now, I am thinking that I will repeat this with several thicknesses of ply, MDF, etc. and actually note the amount of movement. Maybe with a fish scale to note applied force. Kind of a flex-o-meter.
Sounds like a very logical and repeatable way to test for torsional rigidity.



I wish I could find a local source of scrap aluminum.


Steve
Having 5 aircraft manufacturers in town sure has its benefits!

Dave

spalm
12-07-2005, 04:10 PM
Well, one thought that I had to reduce the flexing of the gantry is to make it shorter. This would require flipping the X angle iron to the outside of the gantry walls and raising it. I end up with a slightly larger footprint of about 4. On the bright side, it should be a more stable base and I think I kind of like the walls to keep chips in. I am toying with mounting the X leadscrew(s) to this angle iron.

Thoughts?

I need to get actual numbers written down, but my flex testing showed me that MDF had less flex the Baltic Birch ply which had less flex than Home Depot Birch ply. I guess no surprises here. Although I thought that BB ply would flex less than it did.

Steve

ger21
12-07-2005, 06:52 PM
I haven't actually assembled my gantry yet, so maybe I don't know what I'm talking about, :) but I don't see how you can drive one side only and build the gantry stiff enough to not have play in the other side. Unless you made the driven side wider and used a triangular shaped (when viewed from the top) gantry. But this would take up a lot more X-axis length.

Not the cheapest way, but how about building the gantry sides from 3/4" BB, and route away most of it, leaving material where needed for mounting points. Then, skin it with 1/4" BB both sides. A 1" core from 2 layers of 1/2" ply would be even better I think. The strength comes from the laminations, though. A single piece is just way too flimsy, imo.

whateg01
12-07-2005, 10:48 PM
Steve,

I didn't realize that you were driving this from one side. Not that it matters that much, as any system driven from a single point will be subject to racking when there is a load on one end, or in this case, the opposite end of the gantry. Driving from a single end does make this much more apparent. Much like spacing the bearings out on each end will increase the stability, making one end of the gantry longer will space the bearings out linearly more, thus increasing the stability that way. However, if the end of the gantry is actually twisting, I would think that that will only help some. I believe the answer is in fact to stiffen the end up.

Gerry,

I'd like to add to what you said. A torsion box gets its strength from the two skins being separated by a distance and connected physically along the edges. Assuming the same material is used for both construction methods, a solid piece the same thickness as a given torsion box will have greater rigidity. The tradeoff is the weight. Gluing two pieces of BB plywood together will give a greater strength than a single piece of BB plywood. Routing out the middle reduces the weight, but does not increase the strength of the structure.

As an example, if you grab the ends of an aluminum can and twist, the can will deform fairly easily. If that was a solid piece of aluminum, you certainly would not be able to twist it. That is a very simple example, but illustrates my point.


Regardless of how it is done, I think that if you intend to drive the gantry from one end, you will have to do something to stiffen it up.

Though more complex, a system of cables can be put together to make one end track the other. Much like some of the car lifts that use double-roller chain to keep the rack level, a cable woven under the table can be made to force the far end to move identically to the driven side. I think I saw a post mentioning something about it awhile ago, but I don't remember where it was. Maybe I'll throw a sketch together to illustrate.

Dave

whateg01
12-07-2005, 11:00 PM
Steve,

Here is a diagram of the method using cables to keep everything square.

http://www.d-hanson.com/images/cable_square.jpg

Dave

whateg01
12-07-2005, 11:01 PM
Doesn't really make it simpler though.

Dave

gmfoster
12-07-2005, 11:02 PM
[QUOTE=whateg01]


I'd like to add to what you said. A torsion box gets its strength from the two skins being separated by a distance and connected physically along the edges. Assuming the same material is used for both construction methods, a solid piece the same thickness as a given torsion box will have greater rigidity. The tradeoff is the weight. Gluing two pieces of BB plywood together will give a greater strength than a single piece of BB plywood. Routing out the middle reduces the weight, but does not increase the strength of the structure.

As an example, if you grab the ends of an aluminum can and twist, the can will deform fairly easily. If that was a solid piece of aluminum, you certainly would not be able to twist it. That is a very simple example, but illustrates my point.

Your example is not a torsion box as I understand one. A torsion box in mot only connected along the edges but also in both directions thru the middle. And from the samples I have seen a torsion box is indeed stiffer than a solid board.

Garry

whateg01
12-07-2005, 11:07 PM
Your example is not a torsion box as I understand one. A torsion box in mot only connected along the edges but also in both directions thru the middle. And from the samples I have seen a torsion box is indeed stiffer than a solid board.

Garry

I think a lot of the stiffness comes from the selection of materials used. Since a torsion box has a lot of empty space, it can often be constructed of more dense materials and still be lighter.

Dave

spalm
12-07-2005, 11:23 PM
Garry, Gerry, Dave; interesting stuff. I found that MDF was less susceptible to twist that ply. What I have been told, this is because the alternating layers in ply actually hinder its torsion strength (half the layers don’t count).

Anyway, about torsion boxes and skinning, I have been told that the outer skin is transmitted throughout the box. Therefore a piece of MDF skinned with plastic laminate (with good glue) would actually become a solid piece (minus losses) of laminate. Is this kind of thinking accurate?

I believe that the gods are telling me to go to dual lead screws.

Steve

whateg01
12-08-2005, 12:35 AM
Steve,

Something that occurred to me is that if your ends are twisting, dual lead screws will pretty much eliminate the possibility of the gantry racking and is probably going to be the surest, easiest way to eliminate that problem. However, if there is flex in the ends of the gantry, the tool forces acting on them will probably cause some flexing, allowing the gantry to "lean" toward one end or the other. I don't know how much, and it may be insignificant or the tool forces may not be as great as I would expect, but it's something to think about.


I probably shouldn't do this, but I'm a-gluttin' for punishment.

I know this is way more in depth than it should be but...

It is true that the material used for the "skins" is going to have the largest impact on the ultimate rigidity of a torsion box. This material should ideally have high tensile and compressive strength. This is because as you try to flex a torsion box (or any solid body of material), you will be trying to stretch the outer surface and compress the inner surface. Twisting will try to do both to both surfaces. However, the skeleton of the torsion box should also be somewhat stiff along its axes or else the torsion box will still twist or bend through the deformation of the skeletal material.

Probably the main advantage of using a torsion box is the rigidity-to-weight ratio. I still maintain that using a single material, a solid piece is stronger, as well as more rigid than a torsion box of the same dimensions. However, the ultimate rigidity as well as strength of a torsion box is dependent on the materials used. So, if you used styrofoam as the skeleton of a torsion box, it would still flex more than a "solid" piece of plywood. So when comparing torsion boxes to solid materials, apples must be compared to apples.

Dave

ger21
12-08-2005, 08:11 AM
I just cut up a bunch of 4x8 1/2"MDF last night. Next time your at home depot, pick up one end of a sheet of 1/2" MDF, and then do the same with 1/2" birch plywood. The MDF flexes a LOT more. Same with 3/4", but it's not as noticeable.

A plastic laminated piece of MDF is very stiff, but use a rigid glue, not contact cement. I'm surprised nobody here has used laminate. It's cheap, easy to work with, and can add a lot of stiffness. And you won't have to paint. :banana:

ger21
12-08-2005, 08:44 AM
It is true that the material used for the "skins" is going to have the largest impact on the ultimate rigidity of a torsion box. This material should ideally have high tensile and compressive strength. This is because as you try to flex a torsion box (or any solid body of material), you will be trying to stretch the outer surface and compress the inner surface. Twisting will try to do both to both surfaces. However, the skeleton of the torsion box should also be somewhat stiff along its axes or else the torsion box will still twist or bend through the deformation of the skeletal material.

I disagree about the twisting. Twisting is just bending along a different axis. Corner to corner vs end to end. I don't think a different skeleton would be more resistant to twisting than another. The skins make the skeleton stronger, by not alowing it to move. I would say that a more "dense" skeleton, with more ribs in each direction, should make the box stiffer, as it would effectively make the skins a group of smaller skins, and the smaller any given material is, the harder it is to flex that material.



Probably the main advantage of using a torsion box is the rigidity-to-weight ratio. I still maintain that using a single material, a solid piece is stronger, as well as more rigid than a torsion box of the same dimensions. However, the ultimate rigidity as well as strength of a torsion box is dependent on the materials used. So, if you used styrofoam as the skeleton of a torsion box, it would still flex more than a "solid" piece of plywood. So when comparing torsion boxes to solid materials, apples must be compared to apples.

A styrofoam core would flex because the material itself would be able to move. Bad example. :) Weight is a huge consideration. My gantry box is about 4" x 12" x 40". I estimate it would take a 250lb load in the center to see any flex. It weighs 22lbs. I could have cut the weight in half probable without sacrificing any strength. Next time. :) When talking about MDF, I have a hard time believing a solid piece of MDF would be as stiff, but at 4" thick, maybe it would. But I want light weight and strength, so the torsion box is the way to go for me.


Steve, if you'd like me to delete any of these posts to keep the focus on your project, let me know.

whateg01
12-08-2005, 10:02 AM
Gerry,

Thank you for your thoughts on this. Maybe I'll start another thread to discuss the merits of different construction methods.

Dave

spalm
12-08-2005, 10:11 AM
Dave, I really like the concept of taking an idea to its extremes to see if it still makes sense. But it can be taken too far and then other factors come into play. I think the Styrofoam (it has no elasticity and will crush and not return) and the aluminum can (no internal support) don’t fit here. Don’t worry about trashing this thread, but I also think that a thread dedicated to construction methods would be good. But I really think some building and testing must follow up on the discussion.

Gerry, Something still must be wrong in my testing and I need to go repeat it, but I found that BB flexed more than MDF. Blew me away. I think your example of picking up a sheet and seeing it bend is more because of the weight of the MDF. If you apply that same weight to BB, it may flex more. Try clamping the bottom of a board (I used 8” x 15” standing vertically) and then attaching a pipe clamp to the outside upper corner (simulating my gantry walls). I also clamped a long stick horizontally to the test piece to visually exaggerate the twist. Using an un-calibrated force, grab the end of the pipe clamp and pull it.

I kind of like the plastic laminated MDF concept, which is why I threw it out there to see what reaction it got.

Leave the posts please. I always work in a prototype – test – redesign mode anyway.

Steve

whateg01
12-08-2005, 10:35 AM
[QUOTE=ger21]I just cut up a bunch of 4x8 1/2"MDF last night. Next time your at home depot, pick up one end of a sheet of 1/2" MDF, and then do the same with 1/2" birch plywood. The MDF flexes a LOT more. Same with 3/4", but it's not as noticeable.[QUOTE]

I was wondering about the plywood you were comparing the MDF to. At the HD here, the birch plywood is not really birch plywood. It is only veneered in birch. The plies do seem to be about the same thickness as the baltic birch that I purchase, except for the veneer which is only a thin veneer. I am not sure what the core of the HD plywood is. Does anybody know? Is it even a hardwood? I would hazard a guess, like Steve, that the plywood is lighter, which would naturally create less drooping.

Dave

whateg01
12-08-2005, 11:11 AM
Steve,

I would like to do some destructive and non-destructive testing to better quantify the merits of different construction methods. It will have to wait until it warms up a little though. (At 08:00 it was officially -1F at Wichita Mid-Continent airport.)

Dave

ger21
12-08-2005, 11:51 AM
Gerry, Something still must be wrong in my testing and I need to go repeat it, but I found that BB flexed more than MDF. Blew me away. I think your example of picking up a sheet and seeing it bend is more because of the weight of the MDF.

You're probably right about the weight. I've got some 1/2" BB and 1/2" MDF, so I'll see if I can tell the difference in stiffness tonight.

fyffe555
12-08-2005, 12:01 PM
It might be worth considering too, that a torsion box carries a great part of its load as tension in the skin and the remainder as compression in the skin seperator. BB is definitely better in compression and tension than MDF, even if one is stiffer in flex than another.

spalm
12-08-2005, 10:18 PM
Well, I repeated my little test mentioned in post #35. 3/4” MDF won again hands down. My indicator stick only moved 1/2” at ten inches out, as compared to BBirch 12 ply which moved almost 1”. I also tried HDepot birch 5 ply and HDepot pine handi-panel and got the same result of about an inch and a quarter.

Remember that this whole foo-fa-ra started with me watching the gantry wall twisting. There was no torsion box involved. I had talked myself into the assumption that the Vbearings would solve all these problems. Not so.

fyffe55, are you talking about the ‘tall’ direction? Such that a 4” strip of BB standing on its edge will not flex up and down as much as MDF. Seems like this would be true. I hope so because right now the way I feel about BB is “It may not work as well, but at least it’s more expensive.”

So if I want to gear up for dual leadscrews, do I go with two motors or one motor and a belt? I’ve been to SDP-SI and see their little calculator for belt length but have no idea of the pulley or belt size. Anyone done this at the hobby level? Will they sell to little old me? Are they expensive?

Steve

whateg01
12-08-2005, 10:36 PM
I am going to try two motors on my machine, but I have heard that I may have problems. It seems like it would be less expensive, but I haven't priced belts and pulleys, and I am using an inexpensive driver board. I am also going to try driving 2 motors off of a single driver board, as nobody seems to know what the effect would be, and I figure it's worth a try.

You are also probably after a lot more precision than I am.

Dave

ViperTX
12-08-2005, 11:17 PM
Yes, SDP-SI will sell to anyone. Well since you've got a wooden system....I would select the cheapest....well.....rather then that...select the GT2 (5mm) metal pulleys. The belt calculator is just that it helps you select the minimum belt length based on the pulleys used....I always add about 10 grooves or teeth to whatever they recommend.

ger21
12-11-2005, 09:39 AM
Now for the bad news. Did a lot of testing. The gantry racks terrible. I was concerned with parallelogram’ing or that the gantry could tilt left to right. Not a problem, the combination of the bearings and the Y torsion box seemed to take care of this. The problem I have is the gantry twisting. If I lock the left side, the right side can be moved front to back +/- .25”. I removed the gantry to the bench and repeated this test. It is defiantly caused from the 3/4” ply not having sufficient torsion strength. It is amazing (to me) how much it can twist. I clamped (not as good as gluing) a second sheet of ply for a total of 1.5” and got virtually the same result.

So now what to do. The gantry walls need help. Lengthening them while floating the bed and having a box underneath would help, but I really don’t want to do this. So strengthening them is my first choice. I guess it comes down to three things: torsion box sides, aluminum, or a better choice of wood.

Steve

Steve, I put my gantry together this weekend. I see basically the same thing as you. I can clamp one side in place, and the other side will easily slide 1/2", and I know I could push it at least 1" if I wanted to. I think that even if the sides were 1" aluminum, you'd get similar results. I think the problem lies in the connection between the torsion box and the gantry sides. Because the box is so long, it acts like a large lever and can exert a lot of force on the joint and/or side, in your case probably the sides flexing, in mine a little more the joint.

spalm
12-11-2005, 08:22 PM
Made some progress.

2” angle iron mounted to 3” double MDF beams. I drilled through the beams from the top with a standard bit and from the bottom with a larger bit that would allow a deep throated socket to tighten the rail. That way the nut is hidden inside the beam out of site. I also drilled holes through the bottom plate to allow access. I need to buy some 3/4” MDF to finish the top. It will also have holes to allow access to the rail bolts incase I ever need to adjust them. The rails have oversized holes that allow adjustment. I asked Santa for some aluminum T-track.

The gantry sides are out of scrap 3/4” MDF right now. They will probably stay scrap until I get the Y motor mounting figured out.

Gerry, the MDF really helped the racking, I would say that it is twice as good as when I used BB. But it is still there. I added another set of bolts to the Y box side mounts before I sealed it up. Every little bit helped. The plan is to use double 1/2” MDF gantry sides and two leadscrews.

It seems like it is about half the cost to do one motor and a belt, as compared to two motors. Hope I have the power.

Steve

spalm
12-11-2005, 11:28 PM
Did a little testing. I clamped a small stick to one of the rails so I could balance/align my rafter square. The gantry was twisted. The right gantry wall was about a quarter of an inch behind the left side. After much ado, I found out that it was from uneven bearing pressure. I backed off each bearing, and carefully tightened the pressure while feeling the resistance of the bottom skate bearing to being held still while the gantry was moved. I increased pressure just until the bottom bearing could not be stopped with finger pressure. Bingo, the gantry is now square with the rails. Don’t know if I can explain this but it is pretty cool (or scary).

The second to the last pic shows why I prototype. On the 2” angle it seems like the bearings like to be placed 2 & 29/32” and not 2 & 28/32” apart. The original holes did not allow the gantry to be mounted. My life saving tool is shown in the last pic. I love it.

Steve

Jason Marsha
12-12-2005, 09:29 PM
Looking good Steve. I am jealous of your clean woodwork on the torsion box. :D

Jason

whateg01
12-13-2005, 10:29 AM
...
The second to the last pic shows why I prototype....

I call everything I build a prototype. That way, when somebody asks why I did something screwy, I can say, "Oh, this is just a prototype. That'll be fixed on the next build." ;)

Dave

spalm
12-15-2005, 11:38 PM
Jason, woodworking is the easy part to me. Figuring out the rest is the challenge.

Dave, I am the king of 95% done. I love starting projects, hate finishing them.

I think I want to try dual leadscrews with one motor. Looking at www.sdp-si.com, I picked Metal Pulleys, 1/2” bore (‘cause I don’t have a lathe), 2 Flanges with hub, GT2(5mm), 9mm belt size, and 28 grooves. I get A 6A55-028DF0916 (pic #1). Does this look OK? I am planning to attach this directly to my 1/2” in screws.

While bopping around on their site, I came across these nylon Vbearings (pic #2 on the left). Is this a cheap find? I guess you get what you pay for, but $3.80 for ball bearing Vgrooves seems interesting. One would need a pressure plate for adjustment, but Hmmm. Even the ones on the right could work and they are Acetal for a little over $4. If I order some pulleys, I’ll get some and try them out.

On a completely different subject, I have become enamored with spinning nuts. I know I don’t need them for this small machine, but so many people want to build larger machines, I just can’t stop thinking about them. It seems like a fun challenge. Here (http://www.cnczone.com/forums/showpost.php?p=40623&postcount=30) is a post from a home built one posted over a year ago. Anybody else try these at the hobby level?

Steve

ger21
12-16-2005, 09:28 AM
My original design for my machine had spinning nuts. But the voice of reason reared it's ugly head. I think it can be done pretty easily if you have a lathe. Have you thought about belt drive (rack and pinion style)? I think that's probably a better way to go, but perhaps a bit more costly. (More pulleys needed).

spalm
12-17-2005, 12:18 AM
I know, spinning nuts get no air time. Probably for a good reason. It seems so logical at first, and then I guess the real world comes in to action. Then again, torsion boxes lay dormant for a while also.

OK, let’s examine belt drive. Did you consider a loop belt attaching the motor to the gantry with a hub at each end, or a split belt with the motor at one end and the belt permanently attached to the gantry with an idler pulley at the far end?

Any thoughts on the plastic Vwheels that I posted? Anyone think these are a loser out of the chute?

Hopefully I can do some gantry glue ups tomorrow.

Steve

ger21
12-17-2005, 07:52 AM
Our router at worlk uses a spinning nut, on a 12ft x1-1/2" ballscrew. If you could build them easily, I think they are a great option, especially for longer screws. You can use bigger diameter screws, and not have to have extra power to spin the heavy screws, and they should cut down on whipping.

As for the belt, neither. :) Belt fixed at each end, motor mounted to gantry with idler pulleys to loop the belt around the drive pulley. You also need probably a 2 stage reduction to get around 10:1 I think. I don't know the exact numbers off hand, though.

The plastic wheels would probably work OK. THey would probably run good on cheap aluminum angle, like 1/2" x 1/2".

andy_ck87028
12-17-2005, 07:12 PM
Quote : "As for the belt, neither. Belt fixed at each end, motor mounted to gantry with idler pulleys to loop the belt around the drive pulley. You also need probably a 2 stage reduction to get around 10:1 I think. I don't know the exact numbers off hand, though."

Would that be 10:1 specifically for servo?

From what I have made out, it would likely be different for stepper. (I'm hoping you will say around 3:1 for stepper but I accept answer could be .... it all depends but unlikely as much as 10:1......)

Andy

ger21
12-17-2005, 10:54 PM
Would that be 10:1 specifically for servo?

From what I have made out, it would likely be different for stepper. (I'm hoping you will say around 3:1 for stepper but I accept answer could be .... it all depends but unlikely as much as 10:1......)

Andy

It depends. On the diameter (pitch diameter?) of the pulley, resolution your looking for, speed your looking for.... Would be higher for a servo, yes.


I'm going to delete these two posts tomorrow and give Steve his thread back. ;)

spalm
12-18-2005, 12:12 AM
Jerry, leave the posts. I like the discussion.

I posted in the HobbyCNC section about torque curves. No replies. All I really want to know is when using their motors and their controllers, what is the max RPMs before the power drops off. Seems like an easy answer. Guess Dave doesn’t want to release this info. Sad.

Jerry, so your thought on belts seems to mimic a rack and pinion. Seems simple enough, but without the motor specs, someone such as Andy or I would not be able to come up with the right gearing ration. (?)

As far as build progress goes, I did manage to find some time to do up the gantry walls. I used 3/4” MDF and skinned both sides with laminate from HDeopt. I used Titebond glue. Boy is this easier than contact cement. It allowed adjustments before drying and no smell. I tried some flex testing, and could not bend it at all. We will see if it makes a difference on the machine. I used a black with a pebble finish. Probably not a good choice (like a car) as it shows every finger print and spec of dust. I edged banded them with maple.

Steve

sdantonio
12-18-2005, 12:31 AM
Hi Gerry,

A slightly off topic question. Someone alluded to the fact (I think it may have been you) that it would be nice to use iron or steel angle stock when making up the skate bearing assemblies for JGRO type machines instead of aluminum. But for some reason it was implied that iron or steel would not work, but no explaination was goven as to why it would not work. So, why won't iron or steel work as well as Al in this application?

Steven

ger21
12-18-2005, 02:04 AM
Jerry, so your thought on belts seems to mimic a rack and pinion. Seems simple enough, but without the motor specs, someone such as Andy or I would not be able to come up with the right gearing ratio. (?)


Depending on the size of the machine, I'd want to go bigger than 200 oz motors. But, yes, the torque curves make things easier, although high voltages can straighten out curves a bit. :)
I tend to look at resolution first. To get .001 (full steps, not counting microstepping), a 16 tooth GT2 (5mmpitch) is about 1" per rev. That's .005, so You'd need 5:1 to get .001 resolution. 100ipm at 5:1 would be about 500rpm. I would think you'd be OK with most motors at 500rpm, but, like I said, I'd go a bit bigger than 200 oz. I'm probably going to build a little smaller belt drive machine next year to get a feel for how it works, because I'm leaning that way for the Brushless servo speedster I'll eventually get around to building some day. :)


Steven, steel angle would work fine, but is a lot more difficult to work with. I used 1/4" thick aluminum, and it has no flex at all, unlike the 1/8" you commonly see. It's still pretty cheap, too.

spalm
12-18-2005, 11:17 PM
First try of the new gantry walls. The plastic laminate stiffened up the walls quite a bit, there is still some racking, but it tracks well. I applied a few coats of tung oil on the exposed birch. Looking right smart. I have enough laminate left over to cover the sides of the base. Now I need to take it all apart and drill the Y screw axis holes and apply the laminate to the base.

Steve

ger21
12-19-2005, 09:05 AM
When you say racking, you mean side to side, right? because the bottom of the gantry sides can move, the only thing keeping it straight from racking is the stiffness of the sides. The Y beam is hoding the sides in position. Having the bottom of the sides locked into place would effectively make the sides seem stiffer, as they would only be able to flex between the box and above the top bearings. Right now they can flex from the bottom of the beam to the bottom of the side. Does that make sense?

spalm
12-19-2005, 12:37 PM
Jerry, the racking that I was referring to was as you saw on your design. If you stand at the front of the machine and hold the left side still, you can move the right side towards you or away from you. The laminate made the sides quite strong, and there are now four bolts and two threaded rods connecting the sides to the Y box, so I am not sure where it is coming from. I guess just a lot of leverage. The movement is now down to about an eighth of an inch. Really not that bad.

I can not detect any up or down movement of the gantry or any parallelograming.

Steve

ger21
12-19-2005, 12:55 PM
Nevermind then :)

Yeah, you basically have a very large lever that doesn't take much force to twist the other side. If you go the dual screw route, it shouldn't be an issue at all.

ynneb
12-19-2005, 04:04 PM
The movement is now down to about an eighth of an inch. Really not that bad. Actually that is bad. It will only increase too when you start using your machine. I made the same mistake on my first machine. Athough you probably cant be bothered, I would do as Gerry suggested and go to the effort of dual screw drive. This will make a very tight machine. I guess this is one down side of using V bearings, while they slide nicely, they dont hold the gantry as square as a THK bearing would. Even then, it would be bad practice to rely on a THK bearing to hold the gantry square.
Dual sided drive is definately the way to go. Sorry for sounding like a psuedo expert, but personal experience has shown me this.

spalm
12-19-2005, 04:24 PM
Gotcha Benny.

I live to be bothered.

I tried, but I agree that dual screws here are a must, and that an 1/8” is way too much. I guess I have been planning on them for a while. I was just trying to take care of some of this racking problem before counting on the screws to hold it square.

Steve

ger21
12-19-2005, 07:58 PM
I guess this is one down side of using V bearings, while they slide nicely, they dont hold the gantry as square as a THK bearing would.

I disagree. If the gantry moves with V rollers, it'll move just as much with THK's. It's only able to move because the gantry isn't ridgid. If my gantry was 100% rigid, it wouldn't move with my rollerblade bearings. If you think about it, if the gantry was rigid, moving one side in front of the other would result in a rotated gantry, which would in theory move the bearings out of line with the rails. Since the bearings can't leave the rails, the sides are twisting to llow the bearings to stay on the rails. I would think even 1/2" aluminum sides and an all metal or aluminum gantry would give you the same flexing sides, although to a much lesser degree.

imserv
12-20-2005, 04:42 AM
V-bearings will hold squarely if you use precision rails and retain them from the top and bottom. They can substantially improve the stiffness of an axis. Each end of the gantry should be a stand alone trolley with dual rails, to which the gantry is attached.

If you don't maintain a preload, if you just roll them across a rail that is thrown in place, they will ride up on the v's, to accomodate the variations in rail spacing or geometry. This can permit racking of a too flexible gantry.

Fred Smith - IMService
http://www.cadcamcadcam.com/hobby

spalm
12-20-2005, 01:12 PM
Hey Fred, I can only imagine what you must think when you see what I am doing with your wonderful product. I apologize. But right now I have more time than money and want to try to make this work. The bearings that I bought from you will last a lot longer than this machine will, so I will probably return someday and buy the correct rails for the next generation.

That said, the preload that I am supplying with the bottom skate bearings is rearing its head. When I initially started tinkering with these bearings, I had a concern with the axels running through MDF. I then got distracted with gantry flex and pushed aside this problem. Well it’s back. Not a killer right now, but the skate bearings are tilting downward, and I can imagine them continuing to do so over time. This may well be a source of my racking. Dang, it’s always something. So I need to address this with inserts or plates or somesuch someday.

Steve

ger21
12-20-2005, 01:30 PM
Get some cheap 1/8" x 1" aluminum at Home Depot, and epoxy it into a dado wherever the bolts go through. The aluminum will then carry all the load of the bolts.

Deviant
12-20-2005, 09:35 PM
How much do the vbearings run? Sorry if this is posted somewhere else.

I tried looking on the source website, but didn't see a price tag.

Thanks.

spalm
12-20-2005, 10:13 PM
Hey Deviant, no problem.

Bearings $15
Bushings $3
Single Rail $14 a foot.

http://www.cadcamcadcam.com/index.asp?PageAction=VIEWCATS&Category=16

Deviant
12-20-2005, 10:58 PM
Your using angle iron instead of the rail correct?

((2nd post has angle iron in the picture, I believe))

I was thinking about using rectangle tubing, with flat iron/steel etc clamped to that. Would allow me to run bearings on either side.

Albeit, all of my machining dreams are on hold atm.

Wifey wants a new house.

spalm
12-21-2005, 10:10 AM
Yes, cheap and dirty 1/4” angle iron for both X and Y. The Y uses two 3/4” pieces, one pointing up and one pointing down, bolted to each other with threaded rod. I really like this so far. It is simple and strong and adjustable.

The X is 2” angle iron. It is cantilevered out from the bed to allow the bottom skate bearing access to iron. I used skate bearings to try to save the $75 for four more bearings. I will find out if I can pull it off to my liking. Other people have, but they had the option of welding and better metal working skills than I have.

(Go with the wifey, sounds like she has more sense than the rest of us.)

Steve

spalm
03-02-2006, 10:05 PM
Well after months of personal and work stuff, I got some time to work on the machine. It is really looking nice; the picture does not do it justice. The work table is now birch with T-tracks. The end caps are also birch. I am set up to run two motors. We will see.

I had just enough left over plastic laminate from the gantry to use under the X rails and cover up the sides of the MDF base. A might prettier than my last router.

Steve

Jason Marsha
03-03-2006, 07:00 AM
Its looking really good Steve. I may have to use two motors on the long axis for my next project as well so I will be observing how your dual motor setup works out.

Jason

ger21
03-03-2006, 07:58 AM
Steve, aren't you going to get a little flex in those 3/4" endplates where the screws mount. I'f you push on 1 side of the gantry, I'd think those plates would flex at least a little. Or will they be stiffened up somehow?

Deviant
03-03-2006, 09:04 AM
It's looking pretty.... curious to see how well it performs.

I got a tire kicker coming to look at my house today, hopefully they will make and offer so I can make one of my own on another house.

Seems like life is always trying to slow down all the toy gathering. *grins*

G'luck and keep up the good work.

spalm
03-03-2006, 10:15 AM
Yup, possible flex on the endplates where the screws attach. There is room under the gantry for some corner bracing. I just want to keep it simple right now.

Thanks for watching,
Steve

ballendo
03-15-2006, 11:48 PM
Steve,

I've seen several folks do as you've done; use a torsion box for the BEAM ACROSSS the gantry, whilst leaving the equally needy UPRIGHTS as single layer (flexible!) construction...

Using torsion box gantry UPRIGHTS will increase the rigidity of your gantry immensely. Been there, done that...

A chain is only as strong as its weakest link...

Ballendo

P.S. The maker of the v-bearings is bishop-wisecarver in pittsberg, CA.

P.P.S. Use of THREE eccentrics and one fixed bearing mount will make it easier to get--and keep--things aligned. (This also makes for less variables in th elocation of the parts of the machine relating TO the linear bearings. Like leadscrews, etc. I.E. with at least one fixed position--around which the other three "rotate", you can be assured of at least a minimal amount of variation to deal with.




Yup, possible flex on the endplates where the screws attach. There is room under the gantry for some corner bracing. I just want to keep it simple right now.

Thanks for watching,
Steve

spalm
03-16-2006, 09:16 AM
Hey Ballendo, thanks for the input. I understand your concern with the strength of the gantry upright walls. Like I mentioned I am trying to keep it simple so I went with two design decisions as far as the walls: no support under the table and a composite build up. The walls have Formica yellow glued on both sides. They are really quite strong. In my mind this kind of makes a torsion type thingy with strong skins applied over a weaker substrate. If I remove the gantry and then try to press together the bottom of the unsupported walls, they barely move. I will report back on how it all works in the end.

My bearings were bought at CadCamCadCam. They are really from Superior Bearing (http://www.superiorbearing.com/docs/guidewheels.html) (not BW). "SuperiorBearing" is stamped on them.

I hear ya about using one fixed bearing and allowing the other three to rotate about it. For the gantry, the bottom skate bearings are fixed, so adjustment is pretty easy once I got my rails adjusted and parallel. But this is a good suggestion for my Y carriage, thanks.

Steve

spalm
03-16-2006, 10:54 PM
Well, I have a little progress to report. I added horizontal stiffeners to the end plates. I used biscuits to attach them. Problem solved I believe. I also took apart the old machine and moved this one to the table of honor. Always a sad moment, but only so much room available.

I now have the dual X leadscrews installed and the single Y screw. I used 1/2” ply plates for the motor mounts, in keeping with the design of this machine. They work amazingly well as compared to the aluminum tube standoffs that I used last time. They seem much more rigid. I used a round over bit to soften their edges and applied a couple coats of tung oil.

Next step is to attach the lead nuts to the gantry walls, and then come up with a Z.

Steve

spalm
03-23-2006, 11:54 PM
Hey,

Well I literally raised the blade on my table saw and cut my old wrap around Z from my gas pipe/torsion box machine in half and installed it on this one. I added internal and external supports to stiffen it up, sanded it, routed the edges, and applied a couple coats of Tung oil. It’s OK, but kind of clunky. I changed the screw to 3/8” 12 tpi because I had a bit of trouble before lifting the router in some situations (I think this was mostly caused from my bearings). I am not really proud of it, but it will get me started. I want to re-design this someday (soon). I am using 3/4“ Thomson shafts with bonze bushings. I am thinking I would like to shift to a different bearing. Maybe pillow blocks bolted to the router plate? Like these (http://cgi.ebay.com/Thomson-PBO-8-OPN-Ball-Bushing-Linear-Bearings-w-Pillow_W0QQitemZ7602792116QQcategoryZ67033QQssPageNameZWDVWQQrdZ1QQcmdZViewItem) ? Is $12.50 X 4 a good price?

I am waiting for another driver chip from HobbyCNC so I can drive all four motors at once.

Anyone have a good way of controlling (hiding) the cables from the router and motors? I guess cable chains from Ingus or cable wrap from Staples?

Initial testing has shown me that the V-bearings are working alright. I was disappointed when I first built this, but the more I play with it, the more I like it. It took a bit of adjusting and mucking around to get the rails square and level. And just like Yenneb promised, the rails have conformed to the bearings and now ride right nicely.

Steve

Madclicker
03-24-2006, 02:05 AM
Is that wood panelling? Tell me you are not gonna run this in the family room!

spalm
03-24-2006, 09:37 AM
Yes that is wood paneling; it’s in a corner of the basement that I walled off for a shop about twenty years ago. The white wall in the background is the wall that did the walling off. I find the paneling really ugly, but no one ever saw it until I started taking pics. I have not taken a picture of the floor with bright green indoor-outdoor carpeting. Where did people in the 70’s get their taste?

Thanks for noticing. :)
Steve

keyne
03-24-2006, 10:09 AM
Steve,
thanks for the pictures, really an inspiration. Do you have metal reinforcement where the wheels are mounted?

I will build a router with vee bearings too, but i have the W4 size. Not sure if i want to go with unground angle iron, it seems a little crude. the machine will have a larger envelope (800x2500mm) and use belt drive.
K

spalm
03-24-2006, 11:42 AM
Hey Keyne,

No I don’t have metal reinforcement where the bearings attach. I have considered it. I got scared a few weeks ago that the bearings where shifting, but after I took it apart, it was caused by a hole that was not drilled square with the gantry wall. Not sure how that had happened. They have not really moved. I will keep watching them.

Gerry had recommended that I mortise in strips of aluminum. Good idea. I bought the aluminum, but I really don’t want to mortise through the formica, as this would interrupt the skin effect that I think it is adding. If I had it to do over again, I would mortise in the aluminum strips and then apply the skin.

The machine seems easily scalable to a larger footprint, but then you get into other problems of leadscrews/belts etc. This size is all the room that I’ve got in my basement shop.

The angle iron is crude, but seems to have conformed. Any suggestions on something better? The correct rail is about $1 an inch at cadcamcadcam.

Steve

keyne
03-24-2006, 02:57 PM
Sounds like a couple hundred bucks for my rails...
I have a lot of ideas for v-shaped rail, perhaps it would be better to discuss their merits and shortcomings in a new thread. Angle iron is definitely an option, but perhaps we can come up with a good way to grind the tops like shopbot does. The wear-in scares me a bit because uneven wear can lead to slack or binding in certain areas of the machine.

spalm
03-28-2006, 10:21 PM
Well a lot more hours were spent than shows. The most visible things are the lead screw holders. Pics show the X and Y. I tried to keep with the theme of the machine using ply and bracing. They are really quiet solid. Working under the Y beam was a bit of a challenge. I had to enlarge the upper holes in the gantry walls to allow more adjustment of Y beam. Must say though, it is coming together right nicely.

Should I make the jump to Mach3 from Mach2? I am currently using a P3 850. I’ll be driving four motors now, so maybe I need a bit more CPU horsepower?

I must admit, I am a bit apprehensive about the dual leadscrews and motors. Hope it goes OK.

Steve

Madclicker
03-29-2006, 06:51 PM
Sure like that avatar! Wanna sell it?

ynneb
03-29-2006, 08:35 PM
Steve, It,s been some time since I looked into this thread. You have done very well Indeed. I should have mentioned earlier that you could save some bucks by not using V bearings on the underside of the gantry. I used just one flat bearing in the middle of the two v bearings above it. You really only need this bearing to stop the top v bearings de-railing. Something I didnt do but would have been good was to make the bottom bearing fit onto a spring loaded arm, so that there was universal tension across the whole length of the run. ( Probably not important, but just a small improvment)

spalm
03-29-2006, 11:03 PM
Benny, appreciate the point. A million ways of doing these things. What we really need it to tap into YiTong and their inexpensive bearings. They are a hard nut to crack.

Steve, I stole the avatar. Not something I like doing, but I couldn’t resist. So I thought I would run with is for a while, and then maybe come up with something of my own. It is a dozen frames from the attached gif file. Someone sent it to me and the guys at work and I thought it was so gal dang funny. I used a trial version of Ulead Gif Animator to shrink it to the Zones requirements. I’ll also attach the avatar also as I will probably delete it soon.

Steve

keyne
03-30-2006, 03:42 AM
Ynneb,

a spring loaded hold down bearing will also auto-compensate for wear on the angle iron. I will definitely do this on my machine.
Thank you very much for showing your machine, it has given me alot of ideas and basically confirms my machine concept.
K

spalm
03-30-2006, 11:34 PM
I received my driver chip. I installed it along with the other necessary components to be able to drive a 4th motor (my second X). Fired up Mach2 and slaved the X with A. It worked like a charm. I was so worried about this part, it was a breeze. I started jogging and testing, while increasing the speed. They worked seamlessly together. At one point, I had rolled the machine out in the open and the Y motor bashed into my toolbox and knocked the gantry out of square. This is what I was worried about. But a couple of seconds later, I found a nice workaround. By mistake I drove the gantry into the back motor/bearing plate. The first motor hit and stalled, the second motor kept going until it stalled: result was the gantry was now square again. (I love steppers, you just can’t hurt them).

I cranked up the speed to see what happened. The final result was very reliable rapids at 210 ipm (3.5ips) and I could not stop it with hand pressure. Dancing bananas for this accomplishment. I guess it pays to make everything as strong as possible. I don’t know if I want to run it this hard, but it is much more fun to watch. The right leadscrew is whipping a little at this speed while the left one is very happy (need to investigate).

Steve

spalm
04-09-2006, 09:48 PM
I did my first real cutting this weekend. Tried several little test files that I had developed before, and aligned and leveled every thing. Man, the hours can slip by. I bought some cable wrap at the Depot and cleaned things up a bit. Not the most professional, but hey.

I am fighting a lead screw problem. My right side lead screw locks up solid every now and then, and then totally disappears. Driving me crazy. I just spent an hour trying to combat it. I slowed the ipm way down, no help. I disconnected the other motors to see if it was a power supply issue. It’s not. I have the stepper ramp set to 30 in Mach2, is this a reasonable value? It seems to happen in the middle of the machine. If it was a bearing/leadscrew alignment problem, I would think it would happen at the ends. Just before I gave up for the night, I noticed that the lead screw was quite warm in the middle. So I think it is some kind of alignment or a bent screw.

I showed the wife-unit Vcarve and she was blown away. She made me buy it. Shucks. So I carved a new avatar with it. I love the square ends.

Steve

Tony Mac
04-10-2006, 07:15 PM
Hi Steve,

Glad to hear your wife has a good eye for software - pls pass on our thanks.

Your new vcarved avatar looks great!

What is it cut into?

Tony

spalm
04-10-2006, 08:37 PM
She has better taste in husbands. Tsk tsk.

It’s just old MDF scrap, painted first with the only spray paint I had, flat black. I cut about a dozen different fonts, but I really kind of liked this one because it was so simple, yet unique.

I fuddled around and I think I have fixed my binding problem. Seems like the leadscrews were not parallel to the rails. I loosed the mounting bolts on the endplates and tapped them sideways into alignment. Also did some adjusting of the leadscrew nut mounting. The right leadscrew does have some bend to it, so I believe it was the first thing to pick up this non-alignment. I guess I will order a new one sometime. I settled on 150ipm rapids, respectable but really nice and smooth.

I am building a vacuum attachment right now. Ordered brushes today. This will be a relief to have most of the dust removed. That Bosch really causes a downdraft and creates a lot of airborne dust.

Steve

Htthanh
04-12-2006, 07:04 AM
Spalm
What do you think about 2 lead screw for Z, it is a good I dea??

spalm
04-16-2006, 09:57 PM
Hello Htthanh,

I was hoping someone else would answer your question, as I have no idea. I used 2 leadscrews on the sides of my machine to help keep the gantry from racking (one side moving back while the other moves forward). I don’t have that problem on my Z. The Z axis also gets pretty small and tight, and it seems to me to be hard place to mount 2 screws.

On other news,
I am working on my vacuum attachment. Right now I have it riding up and down with the router. It seems like this is how others are doing it. But doesn’t it make more sense to have it just attached (adjustable) to the Y carriage and therefore having the brushes constantly making contact with the material as the Z moves up and down? :confused:

Steve

ger21
04-16-2006, 10:35 PM
But doesn’t it make more sense to have it just attached (adjustable) to the Y carriage and therefore having the brushes constantly making contact with the material as the Z moves up and down? :confused:

Steve
Depends if your cutting out parts from sheets, or doing thick carvings. If the height is fixed, it would probably need to be adjustable to accomodate thicker material if the need arises.

spalm
04-16-2006, 10:49 PM
I guess I can see either working. And yes, either way needs some way of adjusting the height. I plan to cut sheet goods and signs/designs, more than deep carving.

Do most attachments ride up and down with the Z? It seems like it, and I guess the brushes just kind of smush out of the way when the router enters the wood?

Right now I have the router mount bolts extended out and this assembly mounts to them.

Steve

ger21
04-17-2006, 09:13 AM
All the ones I've seen are fixed to the Z. The best way to do it, imo, is to use long (3" or so) brushes so the when you use a long bit, the brushes are about even with the end of the bit. That way your clearance will be the length of the brushes, or 2-1/2" to 3".

bigz1
04-17-2006, 04:05 PM
Splam did you find any problems by offsetting your x leadscew to one side on machine No2?

Liam

spalm
04-17-2006, 04:14 PM
Hey BigZ,

I only had it over there to prototype some things, mainly fixing the screws using double bearings, 2 start screws using locking collars, and to see what speed I could drive it at. I would not recommend it for continued use. I actually cut stuff with that configuration, but I could get the gantry to rack more than I was comfortable with. Go with a single screw in the center, or duals on the sides.

Steve

bigz1
04-19-2006, 07:14 PM
Splam your machine is looking fantastic. I too hope to use twin screws for the y axis. This may sound like a dumb question but how do you slave the steppers?(I am good with a panel saw but my skills with electronics dont go much further than wiring a plug)

ger21
04-19-2006, 08:41 PM
This may sound like a dumb question but how do you slave the steppers?(I am good with a panel saw but my skills with electronics dont go much further than wiring a plug)

If you're using Mach3 to control your machine, it's as simple as checking a box in the software. :) Maybe a little more to it, but not much.

spalm
04-19-2006, 10:12 PM
Hey bigz1,

As Gerry says, slaving the motors is the easy part. Getting it all aligned, straight, and square can be a bit of a tussle. I used a 4 axis HobbyCNC board for the motor controller. It is just the matter of connecting up to motors (just like wiring a plug), telling Mach3 that there is a forth drive out there, and then clicking on a box to slave the forth motor to the Y. Make sure that you have the directions, steps, and ramp speeds set the same.

Others have used one motor and a pulley to drive the two screws. Seems like a lot of pro machines do this, but that is in a different class. In Some ways this seems better, but in practice I don’t know if it is (using steppers). The cost of the belts and pulleys came out to about the same cost as a second motor (eBay) when I looked at it. I was already use to mounting motors, and belts were and unknown. Also, with two motors, it seems like I get more torque. To align the two lead nuts for parallel, I just drive the gantry into the end until both motors stall. With a modern controller, it will do no damage. Crude, but it works (don’t try this with servos).

Steve

ger21
04-19-2006, 10:16 PM
To align the two lead nuts for parallel, I just drive the gantry into the end until both motors stall. With a modern controller, it will do no damage. Crude, but it works (don’t try this with servos).

Steve

You can also mount 2 home switches, 1 on each side, and mach3 will automatically square it. (provided the home switches are aligned correctly)

spalm
04-19-2006, 10:36 PM
I got a vacuum attachment built. It is basically a shelf with a front support, a hole for the router, a hole for the vacuum and groves in the bottom that the brushes mount in. I bought a three foot section of 2 inch brush for about $9 and cut it into four pieces. These are glued into the grooves. This all mounts to the bolts used to mount the router. I made sure to make the assembly was small enough so that the side with the vacuum hose does not bonk into the gantry wall. It is easy to remove when setting the XYZ home position.

Love those T-slots for hold downs.

I tried it out by routing a bunch of MDF and it worked quite well. I am thinking of re-making it in Plexiglas, because I really like to watch it cut. For now, just not having the dust is good enough, and I can see how it holds up.

Just got some Corian sink cutouts that I want to have a whack at. Any last minute cautions on routing this stuff? I have never worked with it.

Steve

ger21
04-19-2006, 10:38 PM
Just got some Corian sink cutouts that I want to have a whack at. Any last minute cautions on routing this stuff? I have never worked with it.

Steve

Use very sharp bits. And be prepared for a somewhat unpleasant smell :)

txcowdog
04-20-2006, 01:02 AM
Beautiful machine. I love the t-track and the laminate was a stroke of genius.

spalm
07-16-2007, 09:27 AM
Well, it’s been a while. I got my new Z up and running. It is so smooth. Originally I had used rods with various brass bushings. Either they stuck or were too sloppy. It drove me crazy.

A couple of things that I did:

Since I had it apart, I turned the Y rails 45 degrees so that the V-bearings would run on the angle, not on the edge. Much better result. I also split the Y rails so that they could be individually adjusted and leveled. I like it.

I went with official rails for the Z. The cost was not that much and I just had to try them. Boy, it glides up and down on these puppies nice. I mounted the rails on the Y plate and the V-bearings on the Z carriage. I also got rid of the top bearings for the leadscrew. I had noticed this on some other designs and found that still it holds solid for this short of a screw. I went with a 3/8 12tpi screw for added strength in lifting. I used my old Z carriage, adding a standoff and the leadnut to the back. When I have time, I might re-make this, but I needed the CNC running to do so. Kind of a chicken and egg thing. It also let me instantly use my old vacuum attachment.

One little hint that helped me with the V-bearings. I drilled small dimples on the eccentrics so I could keep track of where they were in their rotation. I put one dimple on the thin side and two on the thick side. It is not at all needed, but it can be frustrating adjusting these, and anything helps.

Steve

CNC-Joe
08-10-2007, 04:42 PM
Very nice machine. Nice compromise of purchased and made components.
Now that you've had it running for a while - how is it holding up and how are the results?

harryn
08-10-2007, 05:21 PM
. After much ado, My life saving tool is shown in the last pic. I love it.

Steve

Hi, can you tell me what this tool in post 45 is called? I would like to buy one. Looks great for precision marking.

Thanks

Harry

acondit
08-10-2007, 06:38 PM
Hi, can you tell me what this tool in post 45 is called? I would like to buy one. Looks great for precision marking.

Thanks

Harry

Harry,

It is an Incra T-Rule. I found one on Amazon.

Alan

harryn
08-10-2007, 06:45 PM
Thanks

spalm
08-11-2007, 01:03 PM
Hey all,

Yup, Incra T-Rule. It comes in different lengths. Kind’a yuppie, but I really like it. Put it on your Christmas list.

The machine is holding its own quite well. The new Z is giving me a bit of a fit. Or something is. I have been trying to cut some signs and there is backlash (?) coming from somewhere. I am a lot pickier than I was a few years ago. I can never find the time to work on it.

I plan to post a little note about lessons learned in building this thing. Maybe soon.

Steve

Bakerwood
08-12-2007, 12:26 AM
Steve,

I am new and just read through this entire thread...that's good stuff!

I wondered about rolling the Angle over to use the apex as I was reading. With "V's" top and bottom it looks great. My thoughtnow is can you do a similar mod on the "X's" with the roller bearings at the bottom?

Thanks for the Posts...This is Ichi Ban!!!

Ed

spalm
08-12-2007, 05:42 PM
Arigato Ed-san. :)

Yeah, the Vbearings roll a lot better on the apex than on the edge. I wished I had done that for the X axis. I also really like the split rail. Being able to adjust for parallelism and backlash is a real plus on an experimental machine like this.

Another thing that I wish I had allowed for is adjustment of the motors and leadscrew mounting. Having the motor and bearings mount to plates that would then be attached to oversive holes to allow alignment would have been a real headache saver. Getting tight rails with tight dual leadscrews all going in exactly the same axis so it would not be loose on one end and tight on the other was a PITA.

Applying Formica skins on MDF is a real winner for strength and finish.

Steve

Bakerwood
08-12-2007, 07:21 PM
Some years ago I was working for a millwork company that did custom and semi custom window grilles. In order to maintain profitability we tried to keep parts at about +/-0.002" so that joints would be tight but go together easily everytime.

We built a lot of our own machines and tools due to the semi-custom nature of our work. One thing that the boss (a brilliant farmer-cum-engineer) always said was, "Make every part of the machine adjustable...especially the parts that you don't think you'll ever need to adjust.

I have tried to live by those words ever since. It saves a lot of PITA.

Ed

spalm
09-11-2007, 10:47 PM
This is way cool. The accuracy and repeatability is top notch.

I cut the front plate of my machine into three pieces and threw the middle away. I then re-attached the bearing holders with new standoffs to allow me a little more reach over the end before the gantry wall hit them. I now have almost 2.5 inches of reach and 36 inches to the floor. This will be enough for several setups including mortise and tenons, dovetails, and finger joints. The center section has 4 T-nuts for bolt-ons.

I then built a jig that bolts to the center section. It is basically a clamp and two towers. These two replaceable towers are milled from above to the same height. The height doesn't matter as long as they are the same height. I then place a straight edge across them, line up the work piece to be level with the straight edge, and then tighten the clamp with the two black levers. The towers also allow easy clamping of a temporary backing board.

The next problem is finding 0,0,0. It is absolutely critical to get this lined up correctly (twice). I am using an aluminum touch plate that is wired to my emergency stop input and a separate alligator clip with a wire to ground the router bit. I am using spacers to hold the hold the touch plate 1/2 of the width of the router bit away from 0,0. I jog the bit over to the touch plate; it automatically stops, and I reset each of the DROs, one axis at a time. I am finding it very accurate. My 0,0 is the upper right corner of the work piece.

I am using the bottom of the dovetail as Z0, so I don't have to create new G-code for different thicknesses, and just use the touch plate to set the depth. The three different thicknesses of boards in the pictures were all cut with only one set of G-code. To set this depth, I use a scrap of the board that will mate with the one being routed as the touch plate spacer. This is referenced under the straight edge that is laid across the towers.

I am using Vcarve to do the CAD and CAM. I had a bit of a go, getting it to do what I wanted, but it did it.

Steve

paulC
09-12-2007, 06:05 PM
Nice work Steve,
I was thinking about doing this myself.
Have you tried cutting a tenon yet? the other think I thought this would be useful for.
Thought you could cut one with rounded corners that matches the router bit used for a mortise.
Paul

badbubba
09-13-2007, 12:47 PM
SPLam,

"I am using an aluminum touch plate that is wired to my emergency stop input and a separate alligator clip with a wire to ground the router bit."

I had tried this with TurboCNC, but could not get repeatable results. What controller software are you using?

Bubba

spalm
09-13-2007, 01:21 PM
Hey Paul thanks for the kind words. As you might be able to tell, I am really excited about this. Being able to route on the ends of boards opens up some real possibilities to me. (BTW how is your machine running?)

Bubba, welcome to the Zone. I am using Mach3. Not sure about TurboCNC. All I can say is that is really works well. I am mad at myself that I did not use it much before. I am using a flat aluminum plate for Z and 1/8 inch thick angle aluminum for XY. I have 3 pieces of angle, two at about 1/2 inch, and one at about 3/4 inch long. To get 0,0 for a half inch bit, I stack all three together with the longer one sticking up a little higher. This gives me a 1/4 inch offset. I then put a rubber band around the whole work piece holding them to the corner. Now I jog over until it touches and stops and then reset the appropriate DRO.

Tenons. I have done a lot of thinking about these. Cutting them is no problem. Even two stepped ones like in the simulation below. The problem is that they are supposed to be centered on work piece (in the Y axis). I need to figure out a way to get a touch plate to align itself with the center of the board. Anyone have any ideas on this? Also I need to be able to add the appropriate spacer to get to the center of the bit.

Also does anyone have ideas on a pendant? I would like to be able to jog, clear the emergency stop, and reset each of the DROs. I know a lot of people have them, but not necessarily with these features (and I am cheap).

Steve

ger21
09-13-2007, 01:40 PM
For a pendant, look into the shuttle. Under $100 on Ebay, plugin available from the Machsupport website.

As for locating the tenon. Do you have home switches setup? Use offsets to have a second "home" to locate the tenon (stops?) with the location defined by the offsets. Then just measure your stock accurately (calipers) before writing the g-code.

I think I'll have to incorporate all this stuff into my second router (distant future ;) )

wshelley
09-13-2007, 04:22 PM
Steve wrote "I need to figure out a way to get a touch plate to align itself with the center of the board. Anyone have any ideas on this? Also I need to be able to add the appropriate spacer to get to the center of the bit."

Just a thought. How about a variation on a dowel jig? The kind I'm referring to has two pins set in a beam with a hole in the center (all three are on the center line of the beam). In use, the pins are placed on either side of the board you wish to center the tenon on and turned until the pins are snug against the side. Then the hole would be drilled through the center hole. In your case, add a third pin of a known diameter where the hole would have been but with the pin facing up. Touch off the pin and subtract half the diameter.

Ward

spalm
09-13-2007, 04:38 PM
Gerry, for a pendant do you mean either the ShuttlePro or the ShuttleExpress? They look pretty nice. Easy to program? Looks like a go on that one.

Ward, interesting idea. I have one of those. Never could get dowels to reliability line up with it, but I may be able to steal some hardware for this. Thank goodness for biscuits. This is a much better idea that Ger’s idea with a caliper and rewriting the Gcode. Sheeez. :)

I had a thought about a gizzy that would look like a square (the kind that you measure right angles with) only the two inside faces would have V grooves in them that are somewhat larger than the thickness of the work piece. Maybe made out of 1.5 inch aluminum angle glued to grooved wood. Then add a little tab at the top for the touch plate.

Steve

wshelley
09-13-2007, 04:45 PM
I have a plastic drill guide that works on a similar principle to your aluminum angle idea but it isn't very accurate either. The center guide I described only relies on your ability to drill three holes in a straight line accurately. Hmm, I think your machine can handle that ;-)

I was trying to think of a way to have a tab that would always rotate to stay co-planer with the workpiece so you wouldn't have to subtract half the diameter (one less place for a brain fade) but it was starting to make my head hurt...

Ward

ger21
09-13-2007, 07:44 PM
This is a much better idea that Ger’s idea with a caliper and rewriting the Gcode. Sheeez. :)



:mad:

OK, so I guess you want to use the same code for different sized stock.

Do you have one known side location based on your stop? Then clamp a small aluminum plate to the other side and write a macro to find the other edge, and then automaticaly set Y=0 to the center. Although I think you'd probably need to put some type of edgefinder in the collet.

How about this? Again assuming you have a known side location from homing. Write a macro which includes a DRO on the screen for the stock thickness. Measure the stock, type in the size, and click a button to set the Y to zero. Far quicker than any automated method that required additional hardware to use. Only takes a few seconds to measure a part with a caliper. And if you use offsets to reset the Y, it's easy to switch back to G54 and you wouldn't need to re-home the machine.

If you're not using home switches for your X-Y reference locations, it's a bit trickier.

As for the pendant, yes, the Shuttle Pro. It get's rave reviews from Mach users. If you install the plugin, you can see how easy it is to set up. Ther's a screen with a pic of it, and each button has a drop down list of functions you can assign to them.

spalm
09-14-2007, 08:55 AM
Gerry, sorry about the dig. :) But yes, I think I want to have a set of tenon Gcode. Using standard widths (1/4, 3/8, 1/2) and standard lengths incrementing by 1/2 inches from 1 to 5 inches. If I set Z0 to be the shoulder, I can just use spacers to set the depth and X offset. Maybe a pipe dream, but my CAM is on a different computer, in a different room……

And as usual, you are probably right about using some macros to solve some of these problems. I like your second solution. I didn’t know I could have a numeric entry in a macro. When I first started using the endvise, I thought about having macros to find this corner and that corner etc. and the variety seemed endless. The method I am using required no macros, and got me cutting quickly. And frankly customizing Mach3 is a bit intimidating to me. I guess I need to spend some time learning it. I am still using the default screen with spindle speed, tool changer, and stuff that I never use. So much to learn, so little time.

And no, I never installed home switches, or set up my ‘table’. I guess I should, and treat the endvise as a fixture. (?)

I just ordered a ShuttlePro. Maybe this will change things.

I still haven't totally given up on a mechanical center finder. ;)

Steve

spalm
09-17-2007, 08:44 AM
I guess I have convinced myself to go with home switches and treat the vise as a jig with an offset. I watched the Mach3 video on table setup twice and I finally get it. I always thought home switches were not that accurate, but just used as a safety device. After playing around with them, they are much more accurate than anticipated. This really uncomplicates all the edge finding jig things. I now know that I trust my machine, and I can jog and route all over the place and return with confidence.

I was just playing around and started to make the earlier mentioned right angle V center finder. I don’t think I will really take it to completion, but it was a good practice mortise and tenon joint. It was out of maple scrap, which is why one side is varnished and the other is not.

I realize that a lot of people don’t think much about these things, but I am just plain thrilled. I spent hours Googling woodworking joints. As a woodworker, this is one heck of a jig.

Hey Ward, even though I have dropped the requirement, I made a center finder out of Legos that uses pivoting bars. :rainfro:

Steve

paulC
09-17-2007, 03:51 PM
I'm impressed and jealous. I realise there is no way I can modify my machines to do this. Oh well looks like I'll have to build another. Or maybe a specialised mortising machine.
Paul

spalm
09-17-2007, 09:27 PM
Hey Paul, I am having a blast. Can you cut a slot in the center of your table?

Here is a through tenon with a Celtic weave. Just 'cause I can.

Steve

paulC
09-18-2007, 03:54 PM
Hey Paul, I am having a blast. Can you cut a slot in the center of your table?

Here is a through tenon with a Celtic weave. Just 'cause I can.

Steve

Now that really is different. Not sure what you would use it for.:)
The slot idea wouldn't work as the gantry wraps right around the table with the x screw running through it. I could do it if i extended the router mount forward by 100mm or more but I think things would become unstable. Oh well, i'ts a good excuse for the next machine.
Paul

WayneHill
12-01-2007, 12:36 PM
SPalm (Steve),

I have been surfing through your build log and was wondering about your comment about using the v-bearings on the edge of the angle iron. What problems developed as a result? Maybe a redesign to use the apex of the angle iron for the v-bearing to roll on?

Thank you for your build log. The end clamp idea was great.

Wayne

spalm
12-03-2007, 08:40 AM
Hey Wayne,

The Vbearings kind of dig into the edge of the angle iron, as it is pretty soft. I was worried about developing flat splots. It seems to roll much better on the apex and this is a much stronger (harder) part of the angle iron. I did switch the Y axis to run on the apex, and the Z is on official rails. The X is still running on the edge, as this would require quite a redesign. Maybe someday.

I also really like the ability to individually spread the rails, as I did on the new Y. This allows a lot of adjustment to compensate for parallelism, alignment, etc.

Steve

ger21
12-03-2007, 09:13 AM
It's hard to tell in the pics, but are you just using clamps to hold the boards vertically, or is it like a vise setup? I want to add that ability to the new machine I'm designing, and am trying to figure out the best way to go about it, either a vise, or maybe toggle clamps. Any ideas?

spalm
12-03-2007, 09:35 AM
Hey Gerry,

In my mind, I modeled the endvise after a dovetail jig. It is an adjustable vise. I stole the quick turn lock knobs and hardware from my Leigh jig. The front wooden bar is removable (actually the whole vise is removable). I wanted to be able to add different types of jaws for doing things like angle mortising, like for the splay needed on chair stretchers.

The two towers are like where the dovetail finger board goes. I lay a bar across them and slide the work piece up to meet the bar, lock the vise, and then remove the bar. This allows easy repeatability.

For half blind dovetails, I don’t use the bar, but reference the vertical work piece to be in alignment with the horizontal work piece.

Using backer boards for dovetails is needed.

Steve