Need >very< small linear slide advice

[Stepper Monkey]

I am designing a single-purpose machine well outside the normal scope of things here, small to the point of almost silly. It needs x and y movements only as far as the CNC motions.

I need high accuracy, but only require a 2" or so travel on either axis. No significant load or speed will be ever be required of it. It's only real demand will be for small size and light weight, being capable of being driven by very small steppers to minimize power needs. I am thinking ground ballscrew for efficiency to lower motor power requirements more if possible. Hopefully even to use USB!
It has to be portable, maybe the size of a hardcover book.

Though there are some micro slides and xy tables that small, I cannot find anything motor driven.
Does anyone have any idea where to start? Everything I find is gigantic in comparison. What gets that small for motion components?

[thkoutsidthebox]

I dont know if this is practical, because I wouldn't associate them with 'high accuracy' in a regular sized machine, but in one 2"x2"....hmmmm.....threaded rod comes in small diameters and in about 3mm diameter or for ridgidity a larger diameter would probably work quite well when its only a few inches long. Also, 12" of threaded rod will cost you about....$0.50c !! And it can be coupled direct to your stepper motor. A lot cheaper than ground ballscrews....in fact I dont know if you can get ground ballscrews in a few mm diameter. But then Im not very experienced with this yet. Im sure someone else will shed light on this for you.

[Stepper Monkey]

I don't know about the avaliability of small diameter ballscrews either. 1/4" or 3/8" would be massive overkill, but If I have to go with them I might anyway as repeatability and backlash are really the ONLY important aspects of this device. Otherwise I would just cut a few inches of thread myself....
With as little mass is at issue here, and as short as the travel, I wonder about simply pre-loading each axis with a compression spring or similar. I really don't want to get into that for the same reason I am trying to avoid AB nuts, as that drops the efficiency even further and raises my motor and power requirements. It will be a balance, and one I am not looking forward to through empirical testing....


Anyone able to verify the rumor that tiny high precision components are available for alignment of optics in some repro and copy equipment? Would these work for this project?

[widgitmaster]

Stepper Monkey,
Can you be a little more specific! Small rails are available, but not with ball bushings! For that you must use bearing bronze! Like the ones used in older Floppy Drives!
Small ball screws might be available but I doubt the selection would be large! I would suggest a standard high quality stainless screw thread with delrin nut to eliminate the endplay and backlash!
A small footprint x-y table is not so hard to make, but dors require very close tollerance machining to get the overall unit to exibit the precision you are looking for!

https://www.smallparts.com/

The link above has an excellent selection of parts for miniature widgets!

Eric

[Stepper Monkey]

I am probably trying to overcomplicate things with all the high-tech components. Perhaps a delrin nut and standard thread with simple slides would do fine here after all.
No matter what the system, I guess I really just don't want to have to fabricate one from scratch in any case. I just don't have the equipment or time to create an xy table completely from scratch. If there was some xy or linear slides that are small and motor driven, I would probably just use them even if portability went down a bit.
I am just having trouble finding slides with that little travel, unless they are built for taking huge loads.

[Willbird]

What about the slides screws, and steppers in inkjet printers ?? I would imagine they could be shortened ? They are of low power, high precision, and low backlash ?? Heck some of the cheap printers are like $50 and you could sell the ink ctg. that came with it on evilbay.

Bill

[mxpro32]

hey, there is a guy on ebay that sells thk linear slides in 2 really small sizes. I have purchased the 9mm rails and carriages from him and they are pretty stout for their size and they always sell for cheap. He also sells some 3mm rails which are probably way too tiny. on mcmastercar they sell tiny precision acme leadscrews and nuts which also might work for your application. Speaking of which, you really have my curiosity in high gear now.

[erase42]

cd players have a really nice tiny linear rail and screw setup, if im not mistaken the tiny driive motors must be steppers since they must be positioned so precisely. the drawback is, the travel needed to read a cd is only 1.5 inches so it may be too short. Maybe you could find some old video disk players at goodwill, or on ebay those disks are much larger.

Ed

[CountZero]

The ones I have played with have been normal motors with an optical encoder.

[GEOFF]

Hi,I purchased two transition stages(complete slide assemblies with limit switches, small ballscrews and stepper motors) which were intended for some optical equipment.The travel is about 55mm,and the units have never been installed.My intention was to use them as Z axis for a small twin head router that I intend to cobble up, but I do not know if that will ever happen.These units are of a very high quality and were originally very expensive. I bought them after the company had ceased trading Staples Coombe),but they were still not cheap.If you think that they are what you are looking for, please contact me.Regards,GEOFF.

[erase42]

countzero, that shouldnt be a problem, arent they in effect servos?

[2muchstuff]

The machines that are used to wire and repair silicon chips to the chip pins move in small incraments. The table for the machines that repair the chips are about 2" in diameter and use a 17 sized stepper.