[Pysiek]

Hi folks
I need help with picking a motor to do the task I need. Motor will rotate a 5/8-11 screw which will move adapters to compress material with about 300lbs force. I will use timing belt and pulleys to rotate the screw. How do I find right size motor to do the job?

[Jim Dawson]

While you could use a motor and a screw to accomplish what you want, the control system would be rather complicated and expensive.

It sounds like you are just building a press, so a linear system would be more appropriate for the task. Since you only need about 300 lbs, a 2 inch bore air cylinder would give 314 lbs of force at 100 PSI. The advantage to an air cylinder is that the force is easily adjustable with a regulator.

[Pysiek]

Jim thank you for the reply. The thing is this will be an addition to a product that is already made. I need to take that route. The press is already made and it is powered by turning the handle by hand to compress. Now I want to add the motor so it will be run with switch instead of a crank handle

[Jim Dawson]

OK, I understand. In that case the inexpensive method would be to use a stepper motor, at least this will give you some control over the motor torque. You can over size the motor to insure that it has enough torque, then reduce the torque by adjusting the output from the drive. That way when you reach the desired pressure, the motor will just magnetically decouple and slip.

A 1200 oz/in NEMA 34 stepper should be enough if geared down about 3:1. You can check this by using a spring scale on your existing setup to calculate the needed torque on the screw. Then get a cheap stepper speed controller (about $10 from ebay) and you will be in business.

[Pysiek]

Jim I was thinking about stepper motor also. Just was not sure what size. What kind of stepper controller do I need? I need the motor to be able with press of a button to spin forward and reverse. Can you list what I need?
- 1200oz/in stepper motor
- power supply
- stepper motor driver
- stepper controller
Is the list above correct? Will it be possible that you can post links to some samples of the parts I need? I would greatly appreciate it.

Kris

[Pysiek]

Something like this should work DC Stepper Motor CCM2 Generador Controller Module Reversible Control for DIY Project-6.45 Online Shopping| GearBest.com

[Jim Dawson]

Either of these kits should work

USA free ship!CNC Wantai 1 Axis Nema 34 Stepper Motor 1232oz-in 5.6A +Driver 80V

Single Shaft] Wantai 1Axis Nema34 Stepper Motor 85BYGH450C 1700oz 151mm 6A CNC | eBay

Here are the stepper speed controller listings, any of them would work. The one you listed above would be fine also.

stepper speed control | eBay

[Pysiek]

Okay. So to control everything without PC. I need one of the kits above and the stepper speed control?

[Jim Dawson]

Yes, that's all you need. I think the speed controllers require a small power supply also, maybe 5V or 12V, you'll have to look at the specs. I use a small wall wart power supply to run my speed controller for testing systems.

[Pysiek]

Is there a tool I can use to measure the torque required to turn the screw under pressure? Something like a torque wrench?

[Jim Dawson]

Is there a tool I can use to measure the torque required to turn the screw under pressure? Something like a torque wrench?

I would use a lever and a spring scale. The lever arm could be anything you can attach to the screw. And yes, a scale type torque wrench would work also.

[Pysiek]

Do you think it will put me in the ballpark with the torque required to compress? So I can get right motor and not overpay?

[Jim Dawson]

It will be pretty close to the correct torque. Stepper motors are rated at holding torque, the running torque drops off quickly as the RPM increases. I would want a stepper motor that is rated at least 3 times the needed torque, after factoring in the gear ratio. The output torque of the stepper can be adjusted down by setting the current output of the drive, but there is no way to increase the torque of the motor if it's needed. So buy a motor that is rated higher than you need.