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wjbzone
05-25-2003, 12:05 PM
I am still adding to it. Need to get a better table top. Travel is 24 X 13 X 7. The Kress router is great. 6000 to 26000 rpm - very quiet.

Hobbycnc driver with 125 oz. in. steppers. Turbocnc. travel speed at 40 ipm with no problems.

Just wanted to show off one of my first programs...

Bill.

my web page (http://members.aol.com/wjbzone/index.html )

http://members.aol.com/wjbzone/images/barrows344.jpg

JOE65
05-25-2003, 12:23 PM
Wow looks really great Bill

How did you machine your alum. plate?

balsaman
05-25-2003, 02:41 PM
Very nice machine. Looks great and looks like it works great too!

Eric

wjbzone
05-25-2003, 03:07 PM
Thanks Joe,
I did most of it on a Haas VF1.

I have access to the machine shop (where I work) on weekends for personal projects.

Bill

boxwood
05-25-2003, 07:52 PM
Looks great Bill, I have a hobbycnc board and getting 22 ipm with 24v supply and 8 tpi screw, curious what you are using for power supply and lead screw
Ray

wjbzone
05-25-2003, 09:11 PM
Ray,
I am using a 35VDC power supply.

The ballscrew is a 5/8 OD x 0.201 lead. McMaster Carr PN 5966K26. (cost $1.07/inch)

The ballscrews nuts MMC PN 5966K16 (cost $20.63 each)

Bill

wjbzone
06-11-2003, 11:02 AM
I've seen some posts of the costs in different machinines.

Here is my break down:

Aluminum ($1.00/ pound at scrap yard) $105
motors / driver / wires $180
ballscrew $77
ballscrew nuts $62
drill rod (guides) $55
igus bearings $68
misc bolts $20
transformer $36
case $45
turbocnc software $20
kress router $437

TOTAL $1105

Plus the computer (that I already had. )

I don't know yet what I will spend on a table top. The lamanited insert for a kitchen table is working so far. Any suggestions?

I estimated about 200 hours work. (very rough estimate)

Bill

anoel
06-11-2003, 12:15 PM
Have you measured your accuracy yet? That ballscrew+nut combo produces a really funky inch per step number (0.001015625) I think turboCNC only supports 7 decimal places. So over 120 revolutions you'll be off .0006". Simple contouring should not be a problem but I wonder if a part that requires a "lot" of back and forth movement across each axis (like a large 3D part) would end up being a little goofy with the error being additive over the course of the run. (Again not a problem for something like sign/decorative work but might pose a problem when trying to do precision machining.)

I just wondered because that particular screw and nut are so much cheaper than the rest of the ballscrews in that category. I'm just wondering if the accuracy trade off is signifigant over time to not consider it.

wjbzone
06-11-2003, 03:36 PM
I thought the same thing about that screw when I first priced it. Why so cheap? I assumed it was rolled vs ground?

It does have an odd lead value (about 0.201 inch/rev), but If my thinking is right, any inaccuracy caused by a difference in actual lead vs the lead that Turbocnc is given, would not be cumulative. Parts would be scaled up or down by a constant factor.

I have only checked the repeatablility of multiple movements over a 2" distance. It repeats within .001. I think I will check my accuracy by boring holes near each limit and checking hole locations on a CMM at work.

If my accuracy is off 0.0006 over (0.201x120) 24" I would be very happy. I probably have more inaccuracy due to the drill rod I am using for guides.

That screw vs an acme thread seems to me to be a good choice.

Bill

wjbzone
06-13-2003, 08:24 AM
I checked out my accuracy by boring holes in a piece of wood and checking location.

Hole 1 at 0,0 - origin
Hole 2 at 10,0 checked 9.996,0
Hole 3 at 14,0 checked 13.995,.0012
Hole 4 at 0,-1 checked .0008,-.9999
Hole 5 at 0,+1 checked -.0016,.9990


Looks like I am out about 0.004" over a 10" distance.

These holes were bored in a 1 x 4 piece of pine side clamped in a vice then checked next day held down by one strap clamp. Some of the error could be due to clamping and some due to humidity (a lot of that around here lately)

It would probably be a better check in a piece of plywood, but I am OK with these results.

Bill

anoel
06-13-2003, 09:01 AM
4 thousandth's of an inch certainly does not suck. I'm running at about 8 thousandths tolerance right now. (I've not really dug into finding out where the error lies, but I'm pretty sure that the fact that my machine is not as rigid as it could be has a lot to do with it.

8 thousandths is enough for press fit parts to not fit together. (so therefore I've been avoiding dong them.) :D

wjbzone
06-14-2003, 12:14 PM
I just got my router on/off hooked up to the computer M3/M5. I used a Crydom solid state relay (model D2440-10) that switches up to a 240Vac 40Amp output based on a 5vdc input. Cost about $24 at a local electronics store.

It works great. I have several programs that I have been watching the time so I could go switch the router off. Now I just progam a M5!!!

Thanks to Jeff (homecnc) for the inspiration in getting it working.

Bill

pminmo
06-14-2003, 03:16 PM
Looks nice, what could I expect to pay for 6061 aluminum?

wjbzone
06-15-2003, 01:45 PM
Buying 6061 depends on where you get it, what size you get and how much you get.

I got mine at a scrap yard for $1.00 per pound. I bought 105 pounds and had some left over. (you can see my parts list on my web site - components list (http://hometown.aol.com/wjbzone/page2.html) ) I had to modify my design a little based on what material I could actually find. I still havn't got the table top (labeled base on my component list)

If you buy it new, It can cost around $4 to $6 per pound (last I checked).

Bill

cbcnc
06-15-2003, 03:26 PM
pminmo,

Check out Online Metals. They have an advertisement on this site. That will give you an idea of what the retail costs are. The only other way is to visit some surplus yards and suppliers to see what they have around. Also look for recyclers that deal in scrap. It all depends on where you live and what is around.

Chris

wjbzone
06-16-2003, 07:16 AM
I need to backup a step on that M2/M5 switch. That Crydom solid state relay operates the power to the router, but when I get in a heavy cut, the power is limited.

I am thinking of using the relay to operate a solenoid to open/close a relay that will not limit the power. I can get 120Vac solenoid for about $4 and make the linkage to a switch.

If anyone knows a better method, I would like to hear from you.

Bill

balsaman
06-16-2003, 07:24 AM
If it's a regular solid state relay I don't see how the power is limited. It should be close to zero resistance when closed... Are you sure the relay is the problem? You could put a volt meter across it while the router runs and see what sort of loss you are getting. It should be close to zero volts.

Eric

balsaman
06-16-2003, 11:03 AM
A tip as quoted by a smarter guy than me:

"If the LED inside the Solid State Relay is not fully on, one half of
the TRIAC will not fire. The noise from the motor can also cause
problems. If the motor tool has a built in controller you need to put a light bulb across the motor tool . This allows current to flow.
A resistor will also work. Turn the relay on using an external
battery. Parallel ports don't always have enough output to run a
Solid State Relay."

Eric

wjbzone
06-17-2003, 08:10 AM
Thanks for the info Eric.

I checked the voltage across the relay while the motor was running and am getting about 12Vac. I want to try it again using a battary as the power to the 5Vdc side (instead of the computer parallel port).

The relay is encased in plastic so I don't know if there is any way to see the LED.

Bill

balsaman
06-17-2003, 12:29 PM
Nope, you won't see the LED. A battery will let you know if it's the parallel port or something with the relay itself.

Eric

wjbzone
06-17-2003, 09:50 PM
Eric,
I used a battery to power the 5vdc side of the relay and the router ran fine in a heavy cut. The voltage checked around 1.5Vac (prev measured 12vac using parallel port).

I then hooked the computer parallel port back up to the relay and put a light bulb in on the AC side along with the router.

Running with the light bulb I measured 1.5Vac and the router ran good in a heavy cut (switched by the computer parallel port).

I hope this is the solution: Supply 5Vdc from the parallel port and use a light bulb to keep the current flow on the AC side of the relay.

Thanks for the help.
Bill

balsaman
06-18-2003, 12:29 AM
A resistor may be a better solution. Looks better and won't burn out. I have no idea what value. Try a 10 K.

Eric

wjbzone
06-19-2003, 01:38 PM
Here is my relay for the motor M3/M5. I agree a resistor would be better then the light bulb (even though it is kind of cool when the light comes on)

wjbzone
06-19-2003, 02:02 PM
Next on my to do list was the home switches. I already have the switches. I have been zeroing the machine with a dial depth gage going through the hole I milled for the switch. This works so good, I don't know if I want to mount the switches.

I ran a program for about an hour and the machine returned to home position with 0.001. The switch might be faster, but I don't know if it would be as accurate.

Bill

balsaman
06-19-2003, 02:42 PM
Bill,

You should be switching the black wire on your plug. Not the white wire.

Eric

TRC1
06-20-2003, 12:31 AM
Good point! And you have the hot wire(black) going to the neutral side of the plug. Just switch the black and white wires around.
Don

wjbzone
06-20-2003, 07:00 AM
Ok guys, thanks.

Thats why I post stuff here, I don't have anyone local to help me out. I bet by blind luck, I have the plug on the other end wired backwards also.

Bill

wjbzone
07-07-2003, 10:19 PM
I built a table for my cnc router. Very sturdy table, and I can roll it over to the garage door to blow out the dust.

The center board of the table top slides out to allow access to the X ballscrew. I had the workmate bench vice so I threw it on there too.

Bill

buckie555
07-08-2003, 08:47 AM
Bill

Your machine looks great. I was interested to see the McMaster ballscrews and nuts that you've used as I'm planning on using them on a machine that I'm in the process of building at the moment. Are you using the ballnuts as is or have you preloaded them? I was thinking of using two of the square nuts back to back on each axis with a spacer plate in-between to apply a preload. Also, how easy did you find it to turn down the ends of the screws. You mentioned how pleased you are with the Kress router, in particular with the quietness. Volume (or lack of it) is a big issue for me as well - what model is the router? Do you think that it would be capable of cutting 10mm aluminium plate (providing I turned the spindle speed and the feedrate down)? Sorry about the 20 questions but I'd be grateful for you opinions.

I've been folowing this forum for a while now although this is my first post and I'm very impressed with both the machines that people have built and their appetite in sharing their successes and pitfalls along the way

Buckie

wjbzone
07-08-2003, 09:42 AM
Thanks Buckie,
This forum is a great place for info. I wish it was around when I started my project.

The ballscrews are made by Thompson Saginaw. I was concerned with the quality of these screws because the price was so low. An engineer at the company told me the quality was the same as other ballscrews they make, but their production on this size was high enough to keep the price low.

I tried to turn down the screw in a 5/8 collet, but the OD of the screw is around .610. It kept slipping when I tried to make a cut. It is hard. I 3-jaw chucked the OD and turned it with no problem, but I was worried about runout, so I left grind stock. I finished it in a collet on a grinder.

I am using them without preloading. I checked backlash (when new) and it was less then 0.001 inch between the ballscrew and nut. I have more than that from in my thrust bearing setup (0.006). The software compensates for this with no problem.

The router is a Kress 6990 E. I have not used it for cutting aluminum, but based on what I read here, I think I can. I dont know how fast you could cut through 10mm. It would take several passes. Others in this group could answer that better, but I believe the router has the power.

Bill

WOODKNACK
07-08-2003, 01:09 PM
wjbzone,
are you using a xylotex board? if so I would be very interested to know how you hooked your relay to you board and spindle!

wjbzone
07-08-2003, 05:41 PM
Woodknack,
I am using a Hobby CNC board.

The way I have the spindle relay hooked up does not have anything to do with the board.

I am suppling the +5vdc to the relay directly from pin 17 from the parallel port on the computer. I ground that side of the relay to pin 25.

The other side of the relay switches the 120 volt ac current on and off to the router.

Bill.

buckie555
07-08-2003, 08:10 PM
Bill

Thanks for that. You've convinced me about the screws and nuts - You're absolutely right - with only .001" backlash there's really no need to preload them - guess that's saved me the extra 3 nuts.

Cheers

Buckie

wjbzone
08-07-2003, 01:50 PM
I've had a problem with a loose connection that was keeping me from finishing any of my projects. Turned out the it was in the 6 pin connectors that hook my motors to the electronics box. I replaced the connectors with a terminal block. Been running great ever since.

Here is a pic of a project I just finished. Made from 1" x 12" cedar. The raised letters were based on Autocad scripts.shx font. I did the middle row letters at 2" high with a 1/4" ball nose cutter. I scaled up the same type letters for the top row to 3" high letters with a 3/8" ball nose cutter. The bottom row is 1" high with a 1/8" ball.

I have almost all the letters programmed now so I can paste them on a drawing and have most of the work done.

wjbzone
08-07-2003, 01:57 PM
The last letter had a knot and chipped out on me. I mixed some wood glue with some saw dust from the project and repaired it.

After I re-milled the last letter I think it looks good. A little darker color, but looks like a knot.

dkowalcz
08-07-2003, 04:02 PM
Originally posted by anoel
Have you measured your accuracy yet? That ballscrew+nut combo produces a really funky inch per step number (0.001015625) I think turboCNC only supports 7 decimal places. So over 120 revolutions you'll be off .0006".

Just thought I'd clarify this a little.

TurboCNC stores 12 sig figs internally for computation, so for example .001015625 is stored as 1.015625e-03 (7 figs) and .000000001 would be 1e-09 (1 fig).

Since each extra decimal is one tenth the amount of the last, the issues of remainder accumulation and approximation errors should only become significant on a machine the size of a stadium or so.

Dave K.

balsaman
08-08-2003, 11:32 AM
Oh man, that's gonna be a problem on my next machine then...:)

Eric

ezland00
08-26-2003, 07:27 PM
Where did you get the lead screws from?

wjbzone
08-28-2003, 09:17 AM
Leadscrew from McMaster Carr
http://www.mcmaster.com/

Ballscrew Partnumber 5966K26. (cost $1.07/inch)
Nuts Partnumber 5966K16 (cost $20.63 each)

I just finished making a bookcase. The router made the job super easy with some MDI commands.

I cut the dado grooves in the 1 X 12 side boards. Just enough travel in my Y axis to cut the shelf slots all the way across.
I fed the length-wise cuts under the router in the X direction by hand.

Everything fit together tight. Glued up with no nails.

Bill.

HomeCNC
08-28-2003, 10:48 AM
Yes, the 5/8 .200 pitch rolled ball screw is a good deal. I use it in all my CNC toys from the Enco Drill/mill conversion to my router. You can get it also from Reid tool co.

ezland00
08-28-2003, 05:21 PM
Thaks guys

wjbzone
10-01-2003, 11:26 AM
I finally got my table top fixed up.

I used a 3/4" MDF (18" x 32"). I routed grooves into it and mounted aluminum channels flush to the top. The channels will accept a 1/4" hex head bolt.

The picture here shows the table top. It also shows my Z-axis carriage partially disassembled.

The router is shown in my new optional horizontal position. It is not mounted there yet, but I just need to drill and tap some holes in a new block to make the change.

I will have about 3.5" of Z travel with it mounted here and I can use it to cut dovetail type joints on the end of a board.

wjbzone
10-01-2003, 11:31 AM
Here is a drawing of my horizontal setup. I plan to make the jig shown on the right to mount my boards to hold them square while cutting the joint.

The green block is all I need to add/remove to switch from a horizontal to vertical mill.

Ken_Shea
10-01-2003, 08:33 PM
Bill,
Did a quick search for the Kress and did not find any distributors, where did you locate yours?

thanks
Ken

wjbzone
10-02-2003, 09:22 AM
Ken,
I got mine from
http://www.techno-isel.com/CNC_Routers/Spindles/variable.htm

Bill

wjbzone
10-06-2003, 04:25 PM
I have started having trouble with my Kress router. The 900w (1.25hp) model I bought has some speed control problems.
I was told that this model has been discontinued. The more reliable 600watt (3/4 hp) version is now all that I can get.

I am still under warrenty, so I have the choice now of going to the lower power version or returning the one I have for my money back.

On one hand, I really like the quite operation these routers have and my machine is already setup to mount either Kress router.

Then again, I don't know if a 3/4 hp version will be enough. I see most people here are using at least 2 to 3 hp routers.

I intend to cut mostly wood, but don't want to be limited to light cuts.

Does anyone have a feel for the minimum power requirement a router should have?


Bill

wjbzone
11-11-2003, 03:00 PM
I'm finally back up and running again. Got a full refund for the Kress router. Bought the Porter Cable 1.75 HP variable speed.
I went with the Porter Cable because there is an authorized service center nearby.

Just finish making the clamp to mount the new router:

anoel
11-11-2003, 06:17 PM
BTW Sears/Crafstman makes a Quick Change collet for the Porter-Cable routers. I Bought the collet and a set of 1/4" adapters and a set of 1/4" to 1/8" reducers. I've not done anything with them yet but it works pretty slick and runs true. Plus I can preset my tool length. and do changes without a wrench.

marvinstov
11-11-2003, 09:18 PM
anoel,

Do you have a part number for the Quick Change collet and reducers?

Marv

anoel
11-11-2003, 09:44 PM
Nah, I threw the packaging away. You'll have to make a trip.

ger21
11-11-2003, 09:55 PM
The Porter Cable connector is #26696, the 1/4" holders are #26695. You can search those numbers @ sears.com


Gerry

marvinstov
11-11-2003, 10:13 PM
Thanks everybody.

wjbzone
01-15-2004, 08:18 AM
I bought the Sears Quickrout (quick connect bit changer):

Sears item #00926691000 $29.99
http://www.sears.com/sr/javasr/prod...pid=00926691000

It is designed to fit the Craftsman router shaft and will not fit my Porter Cable as is. I made a simple adapter to get from

my PC 1/2" collet to the Quickrout tool (it mounts to the Craftsman shaft with a built in collet).

I used a 2" long X 1/2" steel dowel pin, and turned one end down to fit the Quickrout (12mm). It was too easy. It extends

the length of my tools about 2", but I like the visibility. I already have extra holes in my cnc machine to slide the router

clamps up high enough to adjust for this extra length.

The Quickrout taper adapters hold 1/4" shank bits using set screws. I can change a bit/adapter in a few seconds with one

hand. I can now pre-set all my tool lengths. Extra taper adapters are $10 for qty of 3.

Mr.Chips
01-15-2004, 08:38 AM
Good idea, this will make bit changing a "snap"

A question about your table. Is that alum "T" slot between MDF?

Thanks
Hager

ger21
01-15-2004, 09:02 AM
They do make one for Porter Cable routers. It's listed on their website, but kind of hard to find there.

Gerry

wjbzone
01-15-2004, 09:38 AM
Hager,
That is T-slot Alum. I have a better picture of it on page 2 this thread. Got it from Woodcrafters. I was concerned the screws in the MDF would not hold, but with the pressure I use to hold things down, it works great.


Gerry,
I could not find the Quickrout for the Porter Cable. How does it mount to the router?

I went to a Porter Cable service center to find out how to remove the collet retainer nut from the end of the shaft. They told me you have to take the router apart and use a special tool to clamp the armature in order to unscrew the nut.

Bill

keithorr
01-15-2004, 02:29 PM
Taking the nut off the first time is a hassle. You do need to take the top off of the motor to expose the armature. I made a clamp from a 2x4 (drill hole and cut in half) and use the pieces like vise jaws to squeeze the armature. The nut is threaded to the end of the shaft. I have four PC routers that get new bearings as neccesary. Just guessing about every 100 hours or so of continuous running. The lower bearing gets clogged with dust.
To extend the tool, I use a collet extension made by Command. About halfway down the page at this URL: http://www.commandtool.com/products_services/cnctoolholding.cfm

They're too long to use at high speed. Too much whip. You can cut them down on a band saw to a couple of inches long. I still use speed control so they don't go wacky.

andybuch
04-12-2004, 11:17 PM
Originally posted by wjbzone

Gerry,
I could not find the Quickrout for the Porter Cable. How does it mount to the router?

Bill

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=SEARS&pid=00926696000

wjbzone
04-13-2004, 07:27 PM
I just got my cnc machine design into a new Cad program (Inventor). Now that it is in, it's easy to make the detail drawings. I posted the ones I've finished on my website. You need Autodesk DWF Viewer (free) to view the drawings. There is a link on my site to get the viewer. wjbzone.com

Bill

cbcnc
04-13-2004, 10:59 PM
Bill,

I've been reading this thread for a while and just tonight looked at your website. I think that your machine is really looking good. It is the style that I would like to make for my second machine.
My first started out as plywood and aluminum but as I got to my Y and Z axes I used mostly aluminum for strength and compactness. You can see it in the "Photos" section.

Chris

wjbzone
04-14-2004, 10:57 AM
Chris,
I've got a few things I want to do still. I need to add some thrust bearings, and like you, I want more torque.
The 120 oz-in steppers do OK, but I think I might upgrade to some servo's when I can.
Bill

wjbzone
06-15-2004, 02:11 PM
I just finished a big job in my kitchen. I made 11 cabinets to fit the soffit space above my existing cabinets. It worked out great.

I find more uses for my cnc router. Things that don't require cnc, but the ability to move the router incrementally by typing a number is great. Cutting grooves to exact width/depth. Boring holes. Biscuit joints.

My favorite is the great miter joints I can cut. I just give a manual line with an incremental move (ie G1X-3y-3F15 cuts a 45).

Pictured below are (Top left) cutting a joint and (top right) how well it fits together. (Bottom) Finished cabinets installed.

They have glass front doors, and light-strips to display the contents.

Bill

buscht
06-15-2004, 03:25 PM
Bill, pretty impressive all the way around. I checked out your website and its nicely done also.

Enough buttering you up. I have a question.

How did you connect the ball nut to the machine? I had to buy a special nut and am looking for a cheaper/ better alternative.

Thanks
Trent

wjbzone
06-15-2004, 04:04 PM
Trent,
I made an adapter on a cnc-lathe at work.

I made 3 extra's, but I think the 15/16-16 thread might be messed up on one of the spare's.

Bill

wjbzone
06-27-2004, 01:25 AM
I'm making a box that fits together with a jigsaw puzzle type of joint on all the corners. Almost done and it looks pretty neat. I'll post a pic of the finished box later.

I had to mount my router in a horizontal position to work on the ends of the boards. Here's a pic of milling the slots on the end of a board. I only have about 1.5" of Z travel with it mounted like this but that's enough to work on the end of 1" thick board.

I did not change my XYZ directions so it plunges in the X direction.

It would be nice if I could easily re-define my axis for this setup so I can plunge in the Z. Anyone know if I can do that with Turbocnc?
Bill

Cold Fusion
06-27-2004, 01:43 AM
Bill, you just did exactly what I had in mind for a project for mine. Just swap the pins on the X and Z in turbocnc.

balsaman
06-27-2004, 09:04 AM
You can have multiple ini files in tcnc.... I *think* you type turbocnc /option1.ini to execute turbocnc with the ini file named option1.ini, for example...

Could be wrong.

Eric

andyew
08-03-2004, 11:02 AM
Hi i'm new to this forum, but eyes are really tired viewing tonnes of useful threads here including this one... i'm kinda addicted oredi!

WJBzone, i'm interested like others do with your "cheap" ballscrews/ballnuts... As i'm going to build mine soon, definitely for a starter, i'm facing a hell lot of decisions to be made! So, would you suggest a 5-TPI ballscrew/nut from McMaster (you've bought) OR a 12-TPI ACME screw/nut of Nook Industrial OR even a 16-TPI ACME screw/nut of Keystone????

My "current" concern is if the 5TPI and 12TPI/16TPI really will show up alot on "normal" jobs like PCB, text engraving, small robot parts milling and other light chores???

Just for lead accuracy comparison:
- Ballscrew you've bought has 0.004"/ft
- Nook Ind has 0.003"/ft
- Keystone has 0.009"/ft

Thanks for your reply!
Andy

wjbzone
08-03-2004, 03:19 PM
Andy,
The 5-tpi ballscrew/nut combination I am using is good for the parts you mentioned. (I don't know the tolerance on small robot parts)

If you minimize the backlash, I think any of these screws would work.

What do you mean by "show up alot"?
Bill

andyew
08-03-2004, 04:13 PM
Thanks for your quick reply Bill...

What i meant was, if the difference in "resolution" of 12/16TPI compared with 5TPI (of your ballscrew) will be significant in milled/engraved object??? But since you've mentioned all of the 3 screws will work fine for light simple jobs, then i have less worries... :))

But still do u use 1 nut per axis? or u use 2 nuts for backlash compensation? I'm not sure if accuracy of 0.004"/ft will b good enuff..... how do u determine the accuracy you need??

By using Keystone's ACME screw of 12TPI with double-nut each axis (for eliminating backlash using spring) and the nut is Gray Iron (not bronze since it's cheaper), it'll be sth around 80 bucks..... If i use the ballscrew you're using with 1 nut each axis, it'll be sth around 140 bucks (but with less resolution and PROBABLY also less accuracy - no antibacklash with only 1 nut)!! Quite a difference in price/spec, which do u suggest??

Thanks man!
Andy

wjbzone
08-03-2004, 08:55 PM
With a 200 step/rev motor on a 5tpi screw, (0.200 pitch), each step moves the nut 0.2/200 = 0.001 inch/step. ( a 12 tpi will give 0.0004"/step and a 16 is about 0.0003).
The 0.001" resolution good for me. I think deflection in my ways and my machine alignment can be more of a problem.

I could not measure any backlash between the screw and the nut when it was new. I don't think this is a problem. The software can compensate for a small amount of backlash without a noticeable dwell.

I have not tried the other screws so I cannot say what problems they might have. The biggest problem with mine is mounting the nuts. I had to make an adapter (shown a few posts up) for the 15/16-16 nut. I do like the fluid movement these have. I would like to know if the double-nut combination causes a lot of resistance to movement.

Bill

DSL PWR
08-03-2004, 09:05 PM
In a double nut, resistance only depends on the preload.

High Seas
08-03-2004, 11:11 PM
With a 200 step/rev motor on a 5tpi screw, (0.200 pitch), each step moves the nut 0.2/200 = 0.001 inch/step. ( a 12 tpi will give 0.0004"/step and a 16 is about 0.0003).
The 0.001" resolution good for me. I think deflection in my ways and my machine alignment can be more of a problem.
Right-oo! Then factor in Full, Half, Quarter Step or smaller microsteps from your controller/driver to get to the rest of the resolution.
[Just as you mentioned - ball screw vs the other choices and the deviation in machining the bits all contribute too]

BTW wbjzone/Bill's right - the deflection in the system and other things like surface unevenness (not flat) of your table all push you further away from "perfection." Just know how close you think you need to be and then make it a bit tighter. Should be alright mate!
:cheers: - Jim

andyew
08-04-2004, 12:47 AM
Thanks guys.... u r really helpful!

As for my 1st CNC, i'll use a cheaper solution with Keystone (0.009"/ft lead accuracy) and leave that attractively priced ballscrew/nut for my 2nd version.... the 1st 1 is probably paid by university and it belongs to them.... :) and i'll pay for the 2nd version which belongs to me....

Andy

DSL PWR
08-04-2004, 02:20 AM
Good to learn on money other than your own!