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Which step setting to use...
« on: August 20, 2012, 01:39:14 PM »
Hello again everyone,

Well, I have my cnc router working pretty good except for a few minor issues..

I have a ‘homebuilt’ 3 axis flatbed CNC router.  The stepper motor chopper boards can be set for 1 step, ½ step, ¼ step, 1/8 step and 1/16 step.  What are the differences between these setting and which one should I use??  Right now, I have all three motor choppers set for 1/8 step ( ...just picked it out-of-the-blue).  The ‘X’ axis motor is on a 2:1 ratio, the ‘Y’ axis is on a 1:1 ratio and the ‘Z’ axis is on a ½” per turn lead screw.  Should I change the step setting on any one or all of the motors?

Also, occasionally I have experienced a few motor stalls both during operation and during jogging and the ‘Y’ axis has a ‘jerky’ ramping motion.  Could this caused by a motor tuning issue?

Thanks a lot for your help,

Re: Which step setting to use...
« Reply #1 on: August 20, 2012, 11:10:47 PM »
Any jerky motion is an indication of skipping steps.  You could go into motor tuning and set the acceleration as low as you can stand and test the machine.  My machine is 50 x 120 inches with all the electronics/steppers/power supplies mounted in the gantry.  The only cords that are running from the gantry are a 120VAC power cord and the Parallel cable.  I found that no matter what I did with the gear ratios and microsteps I could not get the motors to quit skipping steps.  I replaced the 420 oz-in motor on the x-axis with a 650 and problem solved.  I am running at 36 volts on the drives but have on hand a 48 volt power supply that I will install with the other 2 motors.  Awaiting drivers as we speak.  If you have 8 wire motors you will get the most torque if you wire them in bipolar parallel. 

You may also have a mechanical problem that is causing the jerky motion.  So many times we overlook the obvious.

Offline RICH

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Re: Which step setting to use...
« Reply #2 on: August 21, 2012, 06:31:42 AM »
What are the differences between these setting and which one should I use??

They determine the minimum resolution ( 1/steps per unit) which you can achieve and is just one consideration. Gecko site has additional comments about microsteping which is worth a read. The motor will run more smoothly when microstepping.