My CNC DREAM/NIGHTMARE!

[Kobra000]

also ive been looking at something like this,but i dont know if it could be converted into a cnc system or have as much functionality as a gantry style or rack and pinion style....does anyone have any experience with Jet milling machines?









also if anyone is interested or curious..here is the link to where i bought those monster ball screws.
thanks

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT

Keith.

[Walky]

I think you really need to decide what you want and what you need before anything, since this topic has gone from big to small to medium, wood to metal, spindles to how-wire foam cutters.

So, I'll ask six simple questions:

1.- What working volume do you need? (X-Y-Z)

2.- How precise do you need your parts to be? (e.g.: can you live with +- 0.1mm?)

3.- What materials are you going to machine?

4.- What's your current budget?

5.- How much time are you willing to spend designing and building a machine?

6.- Do you have access to milling machines and lathes (and the knowledge to use them), and/or have people that can make parts for you?

That'll probably help to put the ideas in order and help us give you better advice.

There's is a lot, and I really mean a lot of variables involved in the decision, as you already learned with the "bigger motors are not always better" matter. It's very easy to spend twice as much in something half as useful, so research is very important before anything.

Metal milling machines often don't have high enough RPM to be good to work with woods.

[Kobra000]

Walky

thanks for your post i appreciate it,ill try to answer your questions as best as i can.


1.- What working volume do you need? (X-Y-Z).....
A: right now im going with 18x18 with between 4"-12" of vertical spindle/router travel,(i believe this is the z axis)

2.- How precise do you need your parts to be? (e.g.: can you live with +- 0.1mm?) i would like them to within at least a thousandth of an inch,im not sure how to write that out i think its .0001....im not very familiar with mm..roughly 25mm equals 1 inch is the extent of my knowledge of metric.

3.- What materials are you going to machine?..
A: polycarbonate,aluminum,perhaps a small amount of steel,perhaps some hardwoods,if in a laser etching/egraving setup,truthfully whatever i can.metals,woods,plastics,foams,s
(i was going to use a either a rotozip,dremel,or a 20k rpm craftsman spiral cut saw,had plans of using a 3/4hp craftsman router but i think it will be too big for the machine.

4.- What's your current budget?
A: right now,roughly 100-150 every 2 weeks with a total budget not to exceed 900 bucks.

5.- How much time are you willing to spend designing and building a machine?
A:however long it takes,im really in no hurry,the ball screws i mentioned are the only pieces i have bought so far. i have been researching the concept of DIY cnc since 2007. and im pretty experienced with cad and have several personal designs.

6.- Do you have access to milling machines and lathes (and the knowledge to use them), and/or have people that can make parts for you?
Yes i have a modified Unimat SL1000 Mill/Lathe, also a Delta Drill press with cross slide table, i also have a nack/talent for doing what i call "poor mans milling" by using sand paper/grinding disks attached to table saw blades that have been de-toothed, not super super accurate but it gets the job done i also have a varity of sanders and grinders.

Yes i have been using my Unimat for the last 10 years to create pieces and parts,R/c car and airplane parts like suspension, steering and brake parts. i also have made rc airplanes using the templates that come in balsa wood airplane kits then make them out of aluminum
I also scratch make knives with it in my spare time as a hobby,like lock back,fix blade,im even attempting to make a sword. I may not know all there is to know about milling and machining but i get the basics and some of the intermediate ideas and what i dont know,i read all i can get my eyes on.
Yes i have a friend who has a Bridgeport milling machine and is a retired machinist for the oilfield/mechanical industry....but he tires quickly of my questions sometimes and wont let me touch his baby unless i buy my own end mills, face-mills and materials.


i hope this helps.


thanks

Keith.

[Kobra000]

hey guys..


in my searches i found these guys Glacern Machine Tools,man their crash course in machining videos alone were amazing..they also carry supported linear rail,but its all measured in millimeters,hate having to go to a converter page on google.

Glacern Machine Tools - Linear Rails and Bearings

i just wondered if anyone thought their prices were fair, Their linear rail kits come with 2 fully supported rails each with 2 blocks. 4 blocks total per kit
and they give a full load of specs on each component.

now my newest question is this,where will i need supported linear rail the most?
on the x y or z axis or all three? (in all the pictures ive looked at i havnt seen much being used on the z/vertical/up&down axis. and only a few pics showing it used on the y/lateral/away from you and hardly any on the z/bottom/length axis.
(man i swear these xyz axis things can confuse you more than a muppet in a blender. i keep forgetting what is what.)


just thought id toss this in the pot and see if it melts.


thanks guys

Keith.

[Walky]

- Z axis is going up (to the ceiling).

- X and Y axis is usually machine-dependent; usually the longest axis is configured as the X axis (since usually most works are landscape oriented), but I think it's really a personal choice depending on what you'll do. That's why in gantry stile machines the X axis goes towards you, and the Y axis is the gantry. In a metal milling machine, the Y axis might as well be going towards you instead, depending on the design.

- If you're aiming for 0.001" (0.0254mm, since 1" = 25.4mm), which is quite high considering your budget, you'll need ballscrews (hopefully 2 nuts on each axis, but it might be overkill depending on the single nut backlash) or maybe a nice ACME setup with a couple AB (anti-backlash) nuts, but I'm not sure about this one. I'm not sure if the ballscrews you got are good or not, so we'll just have to wait until you get them and see how much backlash is there.

- You're not going to get 18" of travel with the ballscrews you bought, since you must consider the way you're going to mount them, coupling, nut width, etc... Depending on the design you might even have to consider the z-axis width (which you must consider when getting rails, too).

- 16mm supported rails are probably enough for your needs, and they are not so expensive if you get them from china; search for linearmotionbearings2008 on Ebay, his name is Chai and I've never had a problem with him (I have bought quite a few rails from him in the past, and even have some ballscrews on the way). I'll be cheaper than Glacern, even more considering you're in a budget. Unsupported rails on Z are usually used because of the shorter lenght, but I wouldn't use them for aluminum machining. Supported rails are sometimes easier to install, but that's relative.

- Go for a fixed gantry, moving table design if you're mainly going to work with aluminum and other hard materials, it will add rigidity. I'm not sure you'll be able to build a reliable steel working machine with your budget, that takes quite some bucks.

Check this machine out, it might be a good reference to what you want to do: Rocket Sparrow

- The router is an important factor; for some materials you'll want to reduce RPM; the problem is that most adjustable speed routers lose torque at lower speeds (www.SuperPID.com - Super-PID Closed-loop Router Speed Controller is a good solution, but it's probably out of your budget). Forget about the Dremel and other low-end tools, they're just not up to the task. Another factor to consider is the runout of the spindle axis, since it will affect the cutting diameter. A precision spindle is expensive, but some quality routers are nice and might be enough for you (but might still have a runout larger then the ballscrews's backlash). Cheap routers are usually no good and have horrible runout.

I suggest that, once you get your ballscrews and check they're good to go, make a cad drawing of your design including them with the mounting method you choose, and with that data it'll be easier to figure out the rails' lenght (linearmotionbearings2008 has tech drawings on ebay, so it's easier to have the measurements figured out beforehand). I always do that and it saves me a lot of trouble and time, so I just have to assemble once I get my parts. Beware that the chinese rail supports' holes are made by hand and might be off by a milimeter or so (not a big deal in most cases), so it's a good idea to leave the mounting holes for the last, when you actually have the rails.

[Kobra000]

- Z axis is going up (to the ceiling).

- X and Y axis is usually machine-dependent; usually the longest axis is configured as the X axis (since usually most works are landscape oriented), but I think it's really a personal choice depending on what you'll do. That's why in gantry stile machines the X axis goes towards you, and the Y axis is the gantry. In a metal milling machine, the Y axis might as well be going towards you instead, depending on the design.

- If you're aiming for 0.001" (0.0254mm, since 1" = 25.4mm), which is quite high considering your budget, you'll need ballscrews (hopefully 2 nuts on each axis, but it might be overkill depending on the single nut backlash) or maybe a nice ACME setup with a couple AB (anti-backlash) nuts, but I'm not sure about this one. I'm not sure if the ballscrews you got are good or not, so we'll just have to wait until you get them and see how much backlash is there.

- You're not going to get 18" of travel with the ballscrews you bought, since you must consider the way you're going to mount them, coupling, nut width, etc... Depending on the design you might even have to consider the z-axis width (which you must consider when getting rails, too).

- 16mm supported rails are probably enough for your needs, and they are not so expensive if you get them from china; search for linearmotionbearings2008 on Ebay, his name is Chai and I've never had a problem with him (I have bought quite a few rails from him in the past, and even have some ballscrews on the way). I'll be cheaper than Glacern, even more considering you're in a budget. Unsupported rails on Z are usually used because of the shorter lenght, but I wouldn't use them for aluminum machining. Supported rails are sometimes easier to install, but that's relative.

- Go for a fixed gantry, moving table design if you're mainly going to work with aluminum and other hard materials, it will add rigidity. I'm not sure you'll be able to build a reliable steel working machine with your budget, that takes quite some bucks.

Check this machine out, it might be a good reference to what you want to do: Rocket Sparrow

- The router is an important factor; for some materials you'll want to reduce RPM; the problem is that most adjustable speed routers lose torque at lower speeds (www.SuperPID.com - Super-PID Closed-loop Router Speed Controller is a good solution, but it's probably out of your budget). Forget about the Dremel and other low-end tools, they're just not up to the task. Another factor to consider is the runout of the spindle axis, since it will affect the cutting diameter. A precision spindle is expensive, but some quality routers are nice and might be enough for you (but might still have a runout larger then the ballscrews's backlash). Cheap routers are usually no good and have horrible runout.

I suggest that, once you get your ballscrews and check they're good to go, make a cad drawing of your design including them with the mounting method you choose, and with that data it'll be easier to figure out the rails' lenght (linearmotionbearings2008 has tech drawings on ebay, so it's easier to have the measurements figured out beforehand). I always do that and it saves me a lot of trouble and time, so I just have to assemble once I get my parts. Beware that the chinese rail supports' holes are made by hand and might be off by a milimeter or so (not a big deal in most cases), so it's a good idea to leave the mounting holes for the last, when you actually have the rails.

Walky,

i printed out what you wrote,,thank you very much i found it very informative.

the ball screws i bought ..well those things are massive,i just got them the other day. the specs are as follows they were used in some kind of linear motion setup but i have no clue what.

Thread Size 1"-4 TPI
Threaded Length 17-1/2"
Travel Block 1-1/2" x 1-1/2" x 1-58"
End 1: 1/4" cross-hole
End 2: 3/4" dia. x 1/2" long, 1/4" crosshole
Overall size 1" dia. x 18"

they weight between 4.5-5lbs....these things are stout. but their motion is silky smooth...im not really sure how to check for backlash.
They are not as highly/heavily machined as other ballscrews Ive seen but still very very precise and their "raceway" or threads are a lot different from other ball screws,but they operate just as smooth as can be,,like greased snot on lard on ice.

here is a link to an ebay auction that has a great pictures of what i got.

http://cgi.ebay.com/CNC-Linear-Acme-...item2c5bdd8aa8

the only thing about these is that one end is not machined like others ive seen,its just goes fully threaded then has a hole drilled through it.,but the other end has a 3/8" end that appears to be machined for coupling i think..ive noticed alot of other ball screws that say like 10 inches long but only have like 5 5/8ths travel...i dont know,im thinking about just going to acme thread all the way until i get a better understanding of ball screws and their implementation and the physics of how they work.......im also seriously considering the rack and pinion thing....but again i gotta read more about it as it stands i dont know which is the best way to go ..acme thread,rack and pinion,ballscews...im starting to get headaches thinking about all this stuff.

.......the last picture i posted down below a few posts of the K2 CNC picture thing..is pretty much it...in fact im just trying to copy it,but with my own dimensions. ill try to whip up a cad drawing of what im aiming for tonight.


so all my ideas for a "spindle" wont work the dremel,the rotozip,the spiral cut saw,...hmmm guess ill have to come up with something else.....anyone got some cheap suggestions for a "spindle".


i need a break from CNC research ..all these numbers and factors and variables and this and that and the other.....starting to wear me out i tell ya. ...i think im going to go fishing here soon,drink a beer and chill.


thanks guys

Keith.

[Kobra000]

Hola mi Amigos.. Viva La CNC! LOL


Well here and update so far.......not much lol......I did find a very informative sight that finally got the idea of backlash into my thick head...I never figured it was the wobble room between the threads of the screw and the nuts,or the balls and the raceway in ballscrews,or the mesh between the teeth in Rack and pinion.......this clears so much up for me and makes things so much clearer now.

What is backlash? Detail of CNC machine tool backlash in ballscrews, bearings, gibs, and servo backlash.

Now its becoming alittle more clear to me,I have no way to check the backlash of the monster ball screws i purchased ,but when i do the "push pull" check on it,i dont feel any slop,it seems pretty tight..of course i dont think a human could tactile detect a variation of .0001 or less.

After looking at it most of the night im very intrigued by Rack and Pinion systems.im sure they aren't as tight of tolerance as ball screws,but they seem to have alot more tolerance than acme thread,which seems rough to me for some reason. and thank god the rack and pinion systems are so much cheaper than ballscrews (1 screw on ebay went for $10,000 not to be rude but WTF????)

Now im just trying to see how i can incorporate it into my design. I drew up some things lastnight,but i dont know how to post them,
i used Turbocad 3D modeler,been using it since 99 and its the only one i know really well,lots of file formats but i dont know how to upload a picture or other file type from my hard drive to the forum......only "copy link location" and the photo button at the top of this posting box.

Now with new materials comes new questions..im sorry.
With Rack and pinion systems can all the axis be confined to one particular piece? like with the gantry traversing the table instead of the table moving toward the gantry? or is this needed?...
also how do you affix the "rack"? bolt? or weld?
(i would think welding would throw things out of square/spec)

Im very interested in this rack and pinion and am thinking about getting some from ebay,even if i cant use it on my CNC system,i got 100 other projects ive been dieing to find some for.

I came across some really interesting designs/pics...some almost spot on what im trying to build.

here is one that i like very very very much,


This design is virtually what i have sitting in my brain bugging me all night except that i would like to have the "base plate" open instead of boxed.
I believe it uses supported linear rail,not sure what size,for the x axis on the left and right hand side,i dont have the eye for it,but i cant see a failure/bad spot/design flaw in it,other than the base being boxed,for some reason i just dont like that.

This one is one of a very very clean looking system,except im not sure what the "slot car track" or "t slot" looking stuff is or its function, But i still like it very much.



My only question about this one is .at the bottom of the picture,where the gantry connects to the linear rail,could a motor be mounted there and Rack and pinion be used vertically,while the motor lays horizontally...would this provide a much stronger system,instead of unsupported linear shaft as in the picture. the only draw back i see to that idea is the wires to the motor would be traversing along with the gantry....which over time im sure would pop them.



This one here is of a much larger system,but still a clean simple looking system.

the only design flaw i can see here,and this is just using my common sense,i know i dont have anywhere near the eye you guys have for noticing design flaws...is that the gantry tower peices and y axis backing... just looks like its weak,seems the designer used flimsy metal pieces bent up in a metal brake and then bolted/riveted them together,with a system like this built with that type of material i can very well see how backlash could play holy hell with it!

Basically guys id like to build either the first system pictured or the last.
Seriously that first pic is like someone built what was exactly in my head.
and that last one is just so clean and so simple looking,but does look flimsy as heck....for the last pic i would of chose...1/2 6061 T6 aluminum. It almost looks like flashing material in the photo,i love the layout and design,just not the materials used.


I hope this enlightens and clarifies a lot for you guys...i apologize if my posts recently have been vague,cryptic,or just plain mis-understandable.


as always your time,advice,and insights are greatly greatly appreciated.

thanks

Keith.


Ps...could Rack and Pinion be incorporated into any of these designs easily? what kind of gains would i get,and on the other side of the coin....what kind of losses?


oh and i wanted to show you something,as you know ive been considering prebuilt things for the z axis..trying to save some construction time and just a few bucks here and there.

This is a motorized linear tower (with DB9 com cable already wired into it)..it was taking from and inspection table,what it inspected i have no idea,
if it was only alittle cheaper i would of bought it,but i think i offended the seller buy only offering $50 for it. I thought it would of worked beautifully as a z axis,the one that holds the spindle and plunges it.
here is a pic.








I figured this thing was meant for very high precision perhaps even ultra high precision ...so a lot of hard work was already done for me in its construction. i also figured i figured even if it was underpowered with whatever stepper is in it....it possibly could be easily swapped out with one of the motors of the 380oz-in stepper motors modelcnc has to offer...and beefed up a bit...then all id of had to to do was bolt it to the Y axis via a big block o'aluminum and viola a fully functional Z axis..just mount spindle and go!...

But alas the seller wants just too much for it as it stands,and im only gambling on it being compatible with the G540.

[Walky]

1 screw on ebay went for $10,000 not to be rude but WTF????

There are different kinds of ballscrews, some of them quite expensive. Those you saw are probably ground ballscrews, which are top-notch (most of us just use rolled ballscrews).

i dont know how to upload a picture or other file type from my hard drive to the forum......only "copy link location" and the photo button at the top of this posting box.

Click "Manage attachments" to add images, it's below the writing space.

Now with new materials comes new questions..im sorry.
With Rack and pinion systems can all the axis be confined to one particular piece? like with the gantry traversing the table instead of the table moving toward the gantry? or is this needed?...

It all depends on your design, but sure.

also how do you affix the "rack"? bolt? or weld?

I've seen some racks use some kind of part designed to mount them (CNCRouterParts). Don't know much more about it, since I've never used rack and pinion.

I believe it uses supported linear rail,not sure what size,for the x axis on the left and right hand side

Those rails are unsupported.

This one is one of a very very clean looking system,except im not sure what the "slot car track" or "t slot" looking stuff is or its function, But i still like it very much.

That's 8020 extrusion, its shape makes it very rigid, and very nice to prevent flex. (80/20® Inc. - The Industrial Erector Set�)
Some of them fit the SBR supported rails nicely.

My only question about this one is .at the bottom of the picture,where the gantry connects to the linear rail,could a motor be mounted there and Rack and pinion be used vertically,while the motor lays horizontally...would this provide a much stronger system,instead of unsupported linear shaft as in the picture. the only draw back i see to that idea is the wires to the motor would be traversing along with the gantry....which over time im sure would pop them.

Sure, but I'd go with supported rails if using rack and pinion. I'm no expert, but it seems the force of the pinion on the rack under heavy load could flex the rails a little (I could be wrong).

About the cables... that's why we have cable carriers (e-chain)!

This one here is of a much larger system,but still a clean simple looking system.
the only design flaw i can see here,and this is just using my common sense,i know i dont have anywhere near the eye you guys have for noticing design flaws...is that the gantry tower peices and y axis backing... just looks like its weak,seems the designer used flimsy metal pieces bent up in a metal brake and then bolted/riveted them together,with a system like this built with that type of material i can very well see how backlash could play holy hell with it!

Of all the machines you posted, this is the one I like the least. The gantry sides are too thin, and the gantry itself is too high considering the separation between the bearings on the X axis is very small (maybe it's just one bearing, which would be worse). The Y backplate looks too thin (can't tell for sure with just that one image), and I think it should be wider, at least from the top Y rail to the botton one. The Y rails diameter seems too small, but maybe it's an illusion caused by the shadows. The "lever" effect when cutting would be pretty bad, I think. The Z axis screw seems to be 1/4" all thread?, it's very small, not very strong and has a very small lead, so axis movement will be slow. To be fair with it, it seems to be a "fisrt diy build" of sorts, so it really can't compete like the previous two machines you posted, which seem nice. The second machine seems to be one of the XZero's, which IMHO have very nice engineering (there's a topic about them in the forum).

Basically guys id like to build either the first system pictured or the last.
Seriously that first pic is like someone built what was exactly in my head.
and that last one is just so clean and so simple looking,but does look flimsy as heck....

As you can imagine from my previous answer, forget the last machine and only take the first two as a reference.

Ps...could Rack and Pinion be incorporated into any of these designs easily? what kind of gains would i get,and on the other side of the coin....what kind of losses?

Rack and Pinion can be very, VERY fast, but you'll sacrifice resolution. Same happens with timing belts. Let's take this as an example:
TIMING BELT OPEN ENDED 3/8" WIDE 0.20XL CNC | eBay
CNC SERVO or STEPPER MOTOR DRIVE PULLEY 15T 1/4B AL | eBay

That's 0.2" per tooth; if you connect the 15 teeth pulley directly to a 200 steps/rev motor, you'll get 3" of travel per revolution. Divide it by 200 and you get 0,015" per step (you can divide by 400 if using half-step and get 0,0075", just don't go and divide by 800 or 1600, since microstepping is not exact). I still think it's a nice resolution for a hobby machine, and in fact I'm tempted to get those and try them in a medium machine. You can use pulleys to reduce the ratio, so you can sacrifice some speed for resolution (don't get me wrong, even at a 1:3 ratio the thing would still be insanely fast at 1" per revolution).

oh and i wanted to show you something,as you know ive been considering prebuilt things for the z axis..trying to save some construction time and just a few bucks here and there.

Believe me, that thing's worth waaaay more than $50, probably only the motor's worth much more than that (by comparing with the size of the connector, that thing looks HUGE!). Most hobby-level z-axis are in the $200 range. Ask microcarve, he makes some nice z-axis for his machines and maybe he'll be willing to sell it as a separate product: http://www.cnczone.com/forums/diy-cn...p_machine.html

Hell, maybe you'll be better off getting the whole machine from him!, it seems very nice.

[Kobra000]

Walky


thanks for the help man,ill try to get by drawings uploaded to night.

Yeah the first one and second one i like a lot,in fact the first what im going to try to copy,providing a few design changes here and there..supported linear rail and whatnot, I sent a message to Microcarve asking about his Z axis and price list. Well see what he says and go from there.

Yeah if i can get a pre-made z axis,that would help out a lot,then i dont gotta cut my linear rail setup and i can just buy it and keep it at its advertised dimensions,perhaps even get a smaller kit and save some $$$
i was going to get two 55" kits with 2 blocks/2 supports per set for $82.80 each with free shipping and hack it up to where i can get 6 pieces at 18" (thus my settling for a 18x18x? sized machine)
...with a pre-made z axis i can get a 24"-30"-37-40" kit and keep it at that for around 50 on ebay so that works out great. The only thing left is seeing if i can build around the pre-made axis.

As for that z axis tower i was going to buy,that auction is probably going to go way above the 99.99 that the auction starts at,would of been cool to get it but,just another one that got away.

Well im off to read more about that 80/20 stuff.....Industrial erector set,I like that i loved my erector sets as a kid

Hope everyone has a great and productive day.

thanks guys


Keith

[Kobra000]

Walky


thanks for the help man,ill try to get by drawings uploaded to night.

Yeah the first one and second one i like a lot,in fact the first what im going to try to copy,providing a few design changes here and there..supported linear rail and whatnot, I sent a message to Microcarve asking about his Z axis and price list. Well see what he says and go from there.

Yeah if i can get a pre-made z axis,that would help out a lot,then i dont gotta cut my linear rail setup and i can just buy it and keep it at its advertised dimensions,perhaps even get a smaller kit and save some $$$
i was going to get two 55" kits with 2 blocks/2 supports per set for $82.80 each with free shipping and hack it up to where i can get 6 pieces at 18" (thus my settling for a 18x18x? sized machine)
...with a pre-made z axis i can get a 24"-30"-37-40" kit and keep it at that for around 50 on ebay so that works out great. The only thing left is seeing if i can build around the pre-made axis.

As for that z axis tower i was going to buy,that auction is probably going to go way above the 99.99 that the auction starts at,would of been cool to get it but,just another one that got away.

Well im off to read more about that 80/20 stuff.....Industrial erector set,I like that i loved my erector sets as a kid

Hope everyone has a great and productive day.

thanks guys


Keith

[Kobra000]

For some reason that posted twice....hmmm dont know why.

[Walky]

There's no use in buying a large rail to cut it into smaller pieces, since those are extremely hard and might not be cheap to get cut unless you have the proper equipment, and the rail can get damaged or scratched in the process. Linearmotionbearings2008 (the chinese guy from Ebay) can cut and even machine pieces to your specifications, that's a better idea I think.

I think you might be getting the wrong idea about what a supported rail is:

These are supported rails:
linear bearing slide SBR16 (6 supported rails+12blocks) | eBay

They are supported over all their lenght (screws are inserted under the support unto threaded holes of the rail, fixing both together). The bearing blocks are open in the lower side to allow for the support to go through (those are the "SBR" kind of linear rails and bearings, like Glacern's and Chai's).


On the other hand, these are unsupported rails (the ones on top of the picture):
3 ballscrews RM2005 4 couplings 2 SC16 slide rail set | eBay

They are supported (which might have confused you), but only at the ends, so they're just called unsupported rails. The bearing block is closed (no opening); some people don't use the block and just make their own and insert the linear bearing in it (like the first machine you posted, or the Y axis in the second machine; btw, before you get any wrong ideas, the Y axis in the second machine you posted seems to be missing two bearings in the Y axis in the photo, I'm pretty sure it must have been added later, maybe it wasn't ready at the moment; never go with less than 2 bearing for each rail).

Those unsupported bearings from Ebay have different ways of mounting them (the supports are usually clamped at the ends); some just drill and thread the rails at their ends ans screw them into the gantry side plates, but it's not an easy job for most people unless you have a lathe that's up to the task, considering how hard the rail is, and the risk of breaking a tap inside the rail. If you want something like the first machine you posted, check for at least 20mm unsupported rails (SK20 supports are close to what's used in that machine's x axis: 6pcs SK20 SH20A Linear Rail Shaft Support XYZ Table CNC | eBay).

Oh, there's something I forgot about the pack/pinion or timing belt/pulley stuff: if you're using them at the sides, you'll NEED to use one on each side of the gantry, so you'll need a 4 axis driver (e.g. Gecko g540) and clone the X axis to a second motor.

[Kobra000]

There's no use in buying a large rail to cut it into smaller pieces, since those are extremely hard and might not be cheap to get cut unless you have the proper equipment, and the rail can get damaged or scratched in the process. Linearmotionbearings2008 (the chinese guy from Ebay) can cut and even machine pieces to your specifications, that's a better idea I think.

I think you might be getting the wrong idea about what a supported rail is:

These are supported rails:
linear bearing slide SBR16 (6 supported rails+12blocks) | eBay

They are supported over all their lenght (screws are inserted under the support unto threaded holes of the rail, fixing both together). The bearing blocks are open in the lower side to allow for the support to go through (those are the "SBR" kind of linear rails and bearings, like Glacern's and Chai's).


On the other hand, these are unsupported rails (the ones on top of the picture):
3 ballscrews RM2005 4 couplings 2 SC16 slide rail set | eBay

They are supported (which might have confused you), but only at the ends, so they're just called unsupported rails. The bearing block is closed (no opening); some people don't use the block and just make their own and insert the linear bearing in it (like the first machine you posted, or the Y axis in the second machine; btw, before you get any wrong ideas, the Y axis in the second machine you posted seems to be missing two bearings in the Y axis in the photo, I'm pretty sure it must have been added later, maybe it wasn't ready at the moment; never go with less than 2 bearing for each rail).

Those unsupported bearings from Ebay have different ways of mounting them (the supports are usually clamped at the ends); some just drill and thread the rails at their ends ans screw them into the gantry side plates, but it's not an easy job for most people unless you have a lathe that's up to the task, considering how hard the rail is, and the risk of breaking a tap inside the rail. If you want something like the first machine you posted, check for at least 20mm unsupported rails (SK20 supports are close to what's used in that machine's x axis: 6pcs SK20 SH20A Linear Rail Shaft Support XYZ Table CNC | eBay).

Oh, there's something I forgot about the pack/pinion or timing belt/pulley stuff: if you're using them at the sides, you'll NEED to use one on each side of the gantry, so you'll need a 4 axis driver (e.g. Gecko g540) and clone the X axis to a second motor.

Walky

i understand completely,yesterday i had to clean out my ebay favorites cause i had over 120 listings for supported and unsupported linear rail,though only from America,..i was very surprised at the price for the listing you posted of the 6 supported rails plus blocks....blew me away when i saw $84 with only $66 shipping....everything from American sellers ive seen for this has been well over 400,500,600+ bucks.......
Hmmm you really think cutting some 55" to 18" is a bad idea? cause i got all kinds of cutting stuff,chop saw,oxy-ace torch,Milwaukee band-saw,was wondering if i can trim it down in my Unimat.though ive never talked anything beyond a few 5"er pieces of key-stock in my unimat..
i also live just a few blocks from a machine shop...How much do you think they will charge to cut it? thats the only way i can see about being cost effective with the parts cause i can get 6 pieces at 18" out of two 55" rods ( also to mach the ballscrews @18") and then everything comes to 27.60 each. its unsupported ( no bottom rail) but i was thinking of getting those later on and having the rods tapped for them.
linear bearing slide SBR16 (6 supported rails+12blocks) | eBay


Only thing is i have a lot of trepidation when ordering from Chinese sellers.I've only ordered 1 item from Chinese sellers,some LED's for a DIY projector project,and the dude burned me bad even though the tracking number for the Money order showed it going to the address he provided me and even showed it being signed for...it was only 25 bucks but he still gave me a non payment strike...that and im very afraid of my order being seized by Customs...as was the case when i ordered a PC game from France,took me 2 months to get it back from what ever American agency thought might be a threat...and even then it was scratched and they didnt return the manual with it........Does paypal protect against these sort of things?
Ive been looking at Linearmotionbearings2008 ebay store a lot since he was referred to me the other day,im very impressed with the prices,its just what i outlined above that keeps me form making the purchase.
His prices on ball screws alone are amazing...$62+36 for a 18" and in the proper size so roughly a bill,but that's still a lot more tolerable than 700 bucks for something that's not even 10" long...and doesn't even have 7" of travel


I had been wondering how,on some of the 2 motor system for the y axis,they got the motors to move in unison...i would of never thought of cloning an axis..I checked that listing and had to convert the 450mm to inches..comes out to 17.7165 inches. ill have to keep looking in his listings for something just a bit longer.


I've been going at this research for almost 6 weeks now,trying to find the right prices,trying to find the right parts,,,,i dont know guys perhaps i should just save up for one of John's micro carve kits (although its a rigid gantry system,ideally id like a traversing gantry system to be honest.) or perhaps i should just buy that Zen ToolWorks Carver system for 329(7x7x3 kit not sure what i could do with it) and a g540 kit with motors and familiarize myself a little bit more with CNC,then try to duplicate the Carver in a bigger footprint.
i dont know its easy to get discouraged with all the numbers and formulas and i just thought it was going to be alot easier than this...But im tenacious,ill keep trying.



thanks Walky,and everyone else...you know its appreciated.


Keith.

[Walky]

Well, it seems I was wrong, cutting a hardened rod doesn't seems as hard as I thought it was:
http://www.cnczone.com/forums/mechan...eel_shaft.html

Just try to keep the heat controlled to avoid bending the rod, and file the ends to prevent damage to the linear bearings then inserting them.

Maybe putting it in the lathe will be another story, since I've read that hardened leadscrews (which I guess must be of a similar material) are a PITA to machine.

Anyway, I still think the cheaper option it to get those from China; Chai's machining fees are almost negligible, and can cut to any lenght you need. I understand how you feel about getting stuff from China: I haven't lost a package, but I received a defective machine which made me spend about $300 extra just to get a new controller (the seller wouldn't help, and made promises he wouldn't keep making me lose even more time and money).

Even with that in mind, I've had a great experience buying linear components from Chai, and so has a lot of people from this forum (actually, I googled and searched for info about him in this forum before placing my first order, since I was as scared as you); If you want an extra layer of safety you can ask him to send your stuff by DHL, but of course it will cost more. Actually, what I'm more afraid of is China Post, considering how long the package travels and how many places it visits before reaching its destination (even though all of my rails got home, but it took them quite long to my country).

I trust Chai, but the final decision is up to you, and it's perfectly undestandable is you want to buy your rails locally.


Check is these prices are ok for you, at least the company is ok (I get my drivers from them) and have nice customer support:

Linear Bearings & Rails

[Kobra000]

Well, it seems I was wrong, cutting a hardened rod doesn't seems as hard as I thought it was:
http://www.cnczone.com/forums/mechan...eel_shaft.html

Just try to keep the heat controlled to avoid bending the rod, and file the ends to prevent damage to the linear bearings then inserting them.

Maybe putting it in the lathe will be another story, since I've read that hardened leadscrews (which I guess must be of a similar material) are a PITA to machine.

Anyway, I still think the cheaper option it to get those from China; Chai's machining fees are almost negligible, and can cut to any lenght you need. I understand how you feel about getting stuff from China: I haven't lost a package, but I received a defective machine which made me spend about $300 extra just to get a new controller (the seller wouldn't help, and made promises he wouldn't keep making me lose even more time and money).

Even with that in mind, I've had a great experience buying linear components from Chai, and so has a lot of people from this forum (actually, I googled and searched for info about him in this forum before placing my first order, since I was as scared as you); If you want an extra layer of safety you can ask him to send your stuff by DHL, but of course it will cost more. Actually, what I'm more afraid of is China Post, considering how long the package travels and how many places it visits before reaching its destination (even though all of my rails got home, but it took them quite long to my country).

I trust Chai, but the final decision is up to you, and it's perfectly undestandable is you want to buy your rails locally.


Check is these prices are ok for you, at least the company is ok (I get my drivers from them) and have nice customer support:

Linear Bearings & Rails

Walky

i wonder where i can go to get a quote from DHL,cause like you Chinese post scares me as well,the package might go through a 100 set of hands before getting to me (china is what 14,000 miles away or so).....i mean i dont mind paying 100 perhaps a 140 tops for the rail kit,then another 80 maybe 100 to get it here,but as long as i have some kinda protection,ill have to read up on ebays/paypals policies regarding lost or stolen purchases.

Providing that the rail isnt has hard as say a crankshaft bolt for a chevy 350 engine,my Milwaukee bandsaw can cut a lot.(lol except for the crank shaft bolt for a GM 350 engine i learned that the hard way one pull off the trigger for 10 seconds and poof no more teeth on the blade) it would be my first choice cause since you mentioned the heat factor bending the rod,that would eliminate using the chop saw and oxy torch.

I sent Chai a email tonight asking how much a 18x18x8 or 24x24x12 linear rail kit with carriages would cost with shipping...hopefully it will be below 200,and that's including shipping otherwise im going to have to try my hand at milling up my own carriage blocks,i know that's not advisable but i gotta save money where and as much as i can.



I was wondering something,i was going to use Aluminum block for the corners rail "support",but seeing as i need to save money here and there i was wondering if Nylon Block would suffice? My reason being is i can get a 2"x117/8" x 18" block of Nylon for 99.99 plus 15.00 Shipping . the best i can get with aluminum is like 1.5x5x10 for 80 plus shipping...it comes out to roughly the same price but i just see myself getting more parts done with the Nylon, I would imagine its easier to cut and shape than the aluminum and i heard it has excellent strength.
I was hoping to make a lot of the parts out of nylon really... ideally everywhere you see aluminum in the picture above,lol but i dont have alot of experience with it think ill run into flex or some other kinda problem?.....
if they only sold 2" thick lexan or some other kinda polycarbonate....and i didn't have to sell my kidney to get it.

The only deviation out of the above picture is that right now is i cant afford the 80/20 erector set stuff..so where you see the corner blocks mounted to it,i was going to use 1/4" aluminum plate as the base/floor and directly bolt the corner blocks to it from underneath but also try to make the bolts do double duty by also serving as a retaining bolt for the linear rail whilst inside the corner block be it aluminum or Nylon..Did you say threading the rail and inserting it into the blocks was a bad idea?

One thing that also just came to mind is ...should i factor in how much the blocks are going to take away from the linear rail,and that will determine my total axis travel? like if the rails are 18"...and 1 block at one end is say 1.5 thick and another at the other end is 1.5...then 3 inches is effectively removed from the rod resulting in 15" total axis travel? so that would mean if i want 18 inches exact of axis travel id have to buy 20" rails? correct?
its always the little things that eat ya up hu lol.

Yeah i think Ive pretty much decided on duplicating the above pictured machine..or at least 95% percent of it..less the 80/20 erector stuff..id like to use it but its just not in the budget.......im gonna have to go on junk selling spree on eBay to get the scratch made up for this build.

well im off to bed to dream of all the stuff i can hopefully one day build with this.hope everyone has a good night.

thanks Walky,its appreciated.


Keith.

[Kobra000]

Well Chai from linearmotionbearings2008, got back to me wiht a quote that follows

Dear Keith,
The best price to you:
SBR20mm supported linear shaft....24" for X axis.....Quantity 2
SBR20mm supported linear shaft....24" for Y axis.....Quantity 2
SBR20mm unsupported linear shaft 12" for Z axis... Quantity 2
With 2 carriages per shaft.(12pcs total)
218 usd
Air shipping cost is included.
We ship the items to you by DhL.
If you accept this best price to you.please let me know your Paypal Email and your Phone Number. I will send the paypal invoice to you
Thanks!
Chai

218.00 us!...i dont think this is a bad price at all and i get a bit bigger of a system than what i initially planned.
yes im going from a china seller,but a lot of people here have highly recommended him.

what do you guys think?

its appreciated


thanks

Keith.

[tskguy]

Why are you going with unsupported on the Z axis? My experience has found that even with 20mm rods a 12 inch span will flex enough for some chatter. Just go with supported for the z as well. It really shouldnt change the design to much. You will be much happier in the long run.

Just my 2 cents....

Eric

[Kobra000]

Well i was going by what i saw in the picture below that Post,the pic is my guid of what i want to create,i might not keep it at 12,might trim it down to 8" .

i was just wanting to see if some of the guys that have been diligent and helpful by commenting in this post thought about $218 total for 6 pieces with 12 trucks at the stated measurements.

You really think i should use supported for the z axis? are we talking the 2 rods behind the spindle holder? going horizontally? or the rods going vertically on the spindle holder itself? i didnt know it could be used there..all the Machines ive seen this has always been unsupported rod,just plain shaft.... what i was wanting was 12" of vertical plunge with 8" being my absolute minimum.
thanks

Keith.

[Kobra000]

Here is a modified picture detailing what i want. though i didnt want it to be a thumbnail...i wanted it to be larger so you could see the text.....still getting the hang of the functions of the forum,sorry.

[tskguy]

Supported rails for sure!!! Let me explain the way I understand it. And let me be clear I’m no engineer.
I like to think that unsupported rail is very close to a guitar string, a much larger one!! But the principle is the same. The unsupported rod will resonate at some frequency and cause chatter. Basically bouncing against the metal. The supported rail won’t allow for as much flex, it will essentially mute the guitar string. Make sense?

Eric