I've never done anything with motion control, but I need to find a cheap (under $50 in qty of less than 50 units) stepper motor or linear actuator to compress a small spring. What I need is something that can exert a max of 2lbs of force on a spring and I would like between 0.5 and 0.75 inches of travel. I need to set it in very small increments (maybe 0.025 inch increments or less). Repeatability is not an issue, it will be mostly a set and forget type of deal with some (rare) manual adjustments based on a persons whim and a pressure gauge that measures spring pressure.

Thanks in advance for any help.
Linkz

 

Linkz:

Cheap is easy, especially when repeatability isn't important.

Just couple a piece of all-thread to a small Stepper and controller (there are several out there, use Google, it is your friend). Use limit switches (little ones like leaf switches by Cherry) to control start & stop points. Use a standard threaded nut as your coupler to the device you want to control/move.

Note that while cheap, it WILL wear out rather quickly, depending on load, speeds, and duty cycle.

--
Ron Gage - Saginaw, Michigan
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The cheapest way to go is to use pneumatic cylinders. You can easily set up adjustable hard travel stops and get precise repeatability and very fine increment settings using screws and locking nuts. They are cheap to control and very reliable. There are a variety of manufacturers of miniature air cylinders, but one of the most common is Bimba. A simple air pressure gage can be used to determine force by pressure*cylinder area.

 

Linkz,
You should look at www.mpja.com. Pick the category to the left "Fans & Motors" then stepper motors. They usually have good deals on a wide variety of products that an engineer would be interested in. You can get their magazine-sized catalog on a regular basis too if you want it.

Eric Moore