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Author Topic: MOTOR LOCK-UP ON RAPID MOVEMENT  (Read 15109 times)

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MOTOR LOCK-UP ON RAPID MOVEMENT
« on: April 23, 2006, 11:50:53 PM »
I am using the Low Cost CNC 4 axis stepper system from the guys in Australia to run a CNC router and I am having trouble sorting out an issue with my motor calibration in Mach 2.  Or at least I think it's a calibration issue. It seams that my stepper motors sometime (unpredictably) lock up when a rapid movement command is initiated.  It will run fine for long periods but then all of a sudden a motor freezes and makes awful sounds.  I have had it happen individually on all three axis on separate occasions. Can anyone provide suggestions or offer advice on how to trouble shoot this?

Steve
Regards,
Steve

"Caution: Cape does not enable user to fly."

- Batman costume warning label, Wal-Mart, 1995
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #1 on: April 24, 2006, 07:03:35 AM »
Could you please run a driver test and tell me what you see?
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #2 on: April 24, 2006, 01:09:28 PM »
Hi Champion,

Thanks for your reply.  Here is what I found during the OCX Driver Test

Interupt Used = 0
Pulse per Second = varying between 24394 to 24389
CPU Speed = 1694
time between pulses = mean is at about 40 but fluctuates between 20 and 60.

Is this what you were looking for?

Steve
Regards,
Steve

"Caution: Cape does not enable user to fly."

- Batman costume warning label, Wal-Mart, 1995
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #3 on: April 24, 2006, 01:10:52 PM »
sorry I meant to adress my last post to Barker806
Regards,
Steve

"Caution: Cape does not enable user to fly."

- Batman costume warning label, Wal-Mart, 1995
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #4 on: April 24, 2006, 01:57:44 PM »
That looks good...
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #5 on: April 24, 2006, 03:18:14 PM »
Barker806,

When you say it looks good do you mean that the CPU and Mach 2 are working properly? Are there any other ways for me to trouble shoot this problem?

Do you think it might be an issue with the motor tuning settings? The setup I used for each axis is as follows:

Velocity 0.5
Units / sec^2 = 4
Steps per unit = 20000
Kernel speed set at 35000 Hz

Theorectically, with the system flat out the maximum Velocity should be 1.75 inches/second or 105 inches per minute.  To be conservative I limit the rapid movements to 30 IPM.  Do you have any thoughts on this?

Steve
Regards,
Steve

"Caution: Cape does not enable user to fly."

- Batman costume warning label, Wal-Mart, 1995
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #6 on: April 24, 2006, 06:41:37 PM »
OKay try running the system at 25KHz and set you step to 5us under the motor tuning. If you have trouble with this please post you your XML and I can do it for you.
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com

Offline fdos

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Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #7 on: April 24, 2006, 07:02:30 PM »
It will run fine for long periods but then all of a sudden a motor freezes and makes awful sounds.  I have had it happen individually on all three axis on separate occasions. Can anyone provide suggestions or offer advice on how to trouble shoot this?


Steve

That is a classic step motor Stall.   You are probably trying to run them faster than they are able to.

Tell us about your setup.   Are the motors on the machine and driving a load?   Steppers on the bench unloaded will nearly always stall at a lower rpm than when under load.

Also steppers prefer to have some damping between them and the load.   Never use rigid couplings.   I tend to use fenner couplings with a nitrile insert acting as a damper.

Wayne....
« Last Edit: April 24, 2006, 07:04:53 PM by fdos »
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #8 on: April 24, 2006, 10:29:51 PM »
Bryan, I will give your suggestion a try in the morning.  Can you explain how kernel speed cause a motor to stall?  I appreciate all your input.

Wayne, The motors are attached to the CNC router and dirve ballscrews using timing belts with pulleys and a 2:1 ratio.

Steve

Regards,
Steve

"Caution: Cape does not enable user to fly."

- Batman costume warning label, Wal-Mart, 1995
Re: MOTOR LOCK-UP ON RAPID MOVEMENT
« Reply #9 on: April 24, 2006, 10:40:50 PM »
Wayne,

I attached the specs on the stepper motors. I have size 34 P/N PF4913A-05 on all three axis.

Steve
Regards,
Steve

"Caution: Cape does not enable user to fly."

- Batman costume warning label, Wal-Mart, 1995