newbie w/linear motion question


Thread Starter


i'm not a control engineer and have little experience in this field. i've been studying a way to move a light object in a line for a distance of 32 inches or less with accuracy of 1/4 of an inch. i've looked at acme screws and stepper motor driven slides. i just had a slide quoted to me for around $2800. well that is way above my budget and was hoping somebody could recommend a cheap alternative that isn't as precise as a slide but meets my 1/4 inch requirement. thanks in advance.

Curt Wuollet

A stepper motor kit driving a piece of hardware store thread rod will give you accuracy much better than that very inexpensively. I've seen an assembly made from 4 pieces of thread rod and two end plates with bearings that worked for years. The carriage was a block of nylon with three holes, two clearance for the guide rods and the other threaded for the driven screw, The plates were drilled for three rods on top with the driven screw being the middle one, and one rod on the bottom which is just a strut. the bearings were retained to the plate with three machine screws on the outer race and the inner race was simply secured to the thread rod with a nut on each side. The motor drove it through a flex coupler. The whole thing could be made on a drill press with a couple common taps and the bearings were ots item at an auto parts store. A most impressive piece of homebrew and it really worked well. Many places offer stepper motors with the drive electronics in kit form or assembled. As long as you don't need microstepping or the highest possible speeds they work fine. Sounds like just the thing for your application. Positioning was better than .050 over the length of the rod.


Need more information.

Please define "Light load" - depending on the scope of customers I have, light can mean a few grams to a few thousand pounds.

Please define the move trajectory with which you want to cover this 32 inches. i.e. do you want to go slowly (define speed) do you want to accel/decel during the entire move for a triangular velocity profile? How long can it take to get from point A to point B.

Finally, what kind of duty cycle do you expect to need? Is this going to move constantly from target to target all day 24 x 7? Or is it going to move to a position once an hour for 8 hours a week?

If all you need is to get within 1/4 inch of target, you should be able to do this with an inexpensive stepper motor connected to a timing belt drive system or if duty cycle is extremely light, even a stepper motor with a length of all-thread. Your cost is going to depend on how much you are willing to construct yourself. . .

Fill in the missing information and you will get a better scope of answers.

Ken Brown Applied Motion Systems, Inc.
You may also consider a pneumatic cylinder or rodless pnuematic actuator if you have compressed air readily available.

Another thing you might want to mention is how fast to you want to move (32 inches in what time) and how light is light? <1lb to me is light, some customers I work with, 100 lbs is light to them.

You could also buy some bushings, belt & pulleys, relays, and dc brush motor. Fix the load to the belt and move back and forth the relays.

Cameron Anderson
Aerotech, Inc -
"Dedicated to the Science of Motion"
You can go to this wedsite that made Quality & precision linear slides with ball screw price range from US$300 - US$1500 depend on stroke & screw. They also have cleanroom version class 100.

Thank You.
Best regards,


You can use a timing belt and glue it to a linear surface and then use a pully on a motor either servo or stepper. If using stepper you can get inexpensive software from ability systems that uses the printer port for step and direction to a stepping motor drive.

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Now, that's ingenious!
Why didn't I think of that?
An excellent low cost rack and pinion.
And very available.