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Stepper Motor Question
« on: January 25, 2010, 08:39:42 PM »
 ??? Do stepper motors react to different temperature changes?

I have a Vortech Router with a 5'x 10' table and a 6hp motor.  The X & Y axis are controlled by stepper motors that run on rack and pinion. The Z axis is controlled with a stepper motor on a ballscrew.  Mach 3 controls the machine and I use V-Carve software for creating my G-codes.

Currently my machine is set-up in my garage awaiting the new shop to be completed.  I am heating the garage with a space heater (50 to 60 degrees) so that the water cooled spindle does not freeze.  The stepper motors on the Y axis seem to stall and lose their postion.  I have already lowered the acceleration/velocity as suggested by a friend who has the same machine.  This seemed to work fine for a while.

Then the other night I cut out some parts for a hobby cradle I designed.  Everything was going fine then it did it again.  3/4 the way through the program the Y axis stalled for a split second and ruined 3 of my parts.  When the program ended it returned to home, but of course the Y axis was out of position.

I'm not sure what is happening.  Can anyone help.

Thank Chuck  

Offline RICH

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Re: Stepper Motor Question
« Reply #1 on: January 25, 2010, 11:22:32 PM »
Chuck,
The only temperature change that i have found to make them act funny is if they get hot. My ambient temp here is 70 deg so no experince on running them cold.

You reduced the velocity and acceleration and it helped. I am rather conservative and leave a lot of head room. By that I mean, if the steppers start to skip at say 120 IPM i run them at 60 IPM. The problem with all this is that
without a motor curve you just don't know where you will get the max power. Over time and doing machining you just kind of find the acceleration, velocity, and depth of cut that works for all that you do. Part of that
"head room" is power used up to do machining.

Are you using backlash compensation?

Not sure what else to say......

RICH
Re: Stepper Motor Question
« Reply #2 on: January 25, 2010, 11:38:46 PM »
Rich,
I'm not sure what you mean by setting the backlash.

I've been machining for a long time, but I have been away from actually running a machine for a few years.  Unfortunately it seems as soon as your router is out of "Warranty" with Vortect Routers it becomes very hard to get any support.  After several e-mails and phone calls I decided to try this site for answers.

Some of this may just be getting more familiar with Mach3.  I'm trying to spend more time on this site and Vectric's site to learn more tricks.

Thanks, Chuck

Offline RICH

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Re: Stepper Motor Question
« Reply #3 on: January 26, 2010, 12:26:04 AM »
Backlash is non-movement of the axis during change of direction. You can go to config>backlash and see if it is even being used. Don't think that is your problem.

The problem is, if you can duplicate it or it's repetative then you can hone in on the problem, if not the
then it's a PITA and the guessing or suggestions start flowing driving you bonkers.

Try running running the same program cutting air.
Try running the part of the program, where the Y stalled  and  cutting some scrap.
Were the motors hot? Have you moved any wires around? Anything different than what is was like before?
Different material that you were cutting?

See if you can duplicate the problem.

In the mean time,  take a real close look at all the mechanical things and make sure there is no binding, etc and be able to convince yourself that there is no mechanical problem. At least that eliminates one part as a possible cause.

RICH



  
Re: Stepper Motor Question
« Reply #4 on: January 30, 2010, 10:29:04 AM »
The other problem I've encountered is that the processor load exceeds the processor's ability to deliver signals. When this happens all hell can break loose. Go to the diagnostics page, watch the processor load bar go up and down as the program executes. If it breaches 100% at any time you're on course for a program crash. The only cure for this is to reduce the pulse rate to the steppers.