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Steppers have no torque.
« on: October 05, 2007, 03:06:35 AM »
Hello all;
  I have a Taig cnc mill , and have been running the demo of Mach 3 for a while.  I use a Xylotec board and have Oreintal motor steppers.  The motors are 200 steps per rev, and on the Taig 20tpi leadscrew. I have the board set for full step and when I do a calibrate test Mach tills me 32,000 pulses for 1" of movement. Is this right ?  It seems way to fast. I have the motors tuned for 14 inch per min and mid settig for accel. I f I run them faster they stall and hum.  I can grab the coupling on the stepper and stall it with very light force.  I have had the motors for years in a box , cuold  they be bad ? I got some specs years ago and they were 180 in/oz motors.  Is this to weak for mill ?  I love to make stuff on the cnc , but its not realiable, it stalls to much.   I have noticed it runs better withstock code from the Mach software ( wizards ) But is actting up with Mastercam G-code.   It always stalls at start of program. If I bypass some start settings and get to the meat of the code it works better. I have a 1ghz amd desktop with 512 meg ram, running Windows 2000.

                                 Thanks   Mitch .........................

Offline moxy

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Re: Steppers have no torque.
« Reply #1 on: October 05, 2007, 04:29:49 AM »
Hi Mitch, What stepper drivers are you using?
Regards
Les

Offline moxy

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Re: Steppers have no torque.
« Reply #2 on: October 05, 2007, 04:39:08 AM »
Hi Mitch, orry, didn't see the mention of the Xylotec board. You should be running the motors  at anything up to 20 times the voltage on thier labels (6v will run really well on about 75 volts without any problems) and the amps at spec . Don't run them above the recommended amps or you will get smoke! They will run quite hot at specified amps but don't seem to have any problems.
Regards
Les

Offline stirling

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Re: Steppers have no torque.
« Reply #3 on: October 05, 2007, 05:16:26 AM »
Hello all;
 I have a Taig cnc mill , and have been running the demo of Mach 3 for a while. I use a Xylotec board and have Oreintal motor steppers. The motors are 200 steps per rev, and on the Taig 20tpi leadscrew. I have the board set for full step and when I do a calibrate test Mach tills me 32,000 pulses for 1" of movement. Is this right ? It seems way to fast.

200 steps per rev * 20 threads or revs per inch = 4000 pulses per inch at full step.

I have the motors tuned for 14 inch per min

14 * 4000 / 60 pulses per sec = 933.33 pulses/sec. call it around 1KHz which is around 5 revs per sec - which isn't hugely fast. The faster you want to drive them the more the overdrive ratio of the drive voltage you need. what ratio are you using (supply voltage to motor voltage)?

and mid settig for accel.
whatever that means... until you get your speeds worked out and whether your motors can cut it power wise - turn you accel down pretty low - once you have motors that can run at the speeds you want then you can figure out what accel your motors/rig can handle.

If I run them faster they stall and hum. I can grab the coupling on the stepper and stall it with very light force.

Two (of many) possibilities are a) too low drive voltage ratio b) resonance.

I have had the motors for years in a box , cuold they be bad ?
motors are neither like wine nor milk, they don't get better or worse with age :-)

I got some specs years ago and they were 180 in/oz motors. Is this to weak for mill ?

Well that depends. Of more interest to you at the moment is: Their Amps/phase, Voltage, inductance, PS voltage, whether they're resonating etc. as above.

If I bypass some start settings and get to the meat of the code it works better.
What settings are you bipassing?
Re: Steppers have no torque.
« Reply #4 on: February 02, 2018, 11:01:44 PM »
Hi,
    My name is Anthony, I am new to the forum and new to the CNC world. I acquired a taig 2027 CNC micro mill to serve as a learning tool for me to gradually lead into the CNC and machining trade. After buying the Mach 3 software and the necessary adapter board to finally get this older mps 2000 controller running and communicating with the computer, I was finally able to get my machine running. After a few test programs, I noticed that my stepper motors were stalling while in jog mode. I tried motor tuning, loosening the gibs on all axes, and adjusting the motor couplers but nothing seemed to work. After doing some research, I realized that resonance is a possible issue, so I decided to completely take the motors off the machine to see if this was the case. When I removed the motors and tried to jog them, they instantly stalled. It seems to me that there is absolutely no torque given out by the motors and all they do is hum. I know for a fact that the motors are not bad because I ran a few programs before and everything seemed to work out fine.

 Basically, I have been at this now for the last couple weeks and I am not sure exactly what I should do. I would really appreciate if someone could steer me in the right direction as to what my next move should be. If my issue is truelly a resonance problem, I would appreciate if someone could tell me where I need to measure the current and voltage from so that it is set correctly. Any suggestions would be greatly appreciated as my frustration with this machine has reached its highest point. I hope to see some chips flying soon! Thanks.
Re: Steppers have no torque.
« Reply #5 on: February 03, 2018, 02:37:19 PM »
Hi,
it sounds to me like your drivers have lost the plot.

Testing a stepper driver is not straight forward, you really need an oscilloscope ideally with a high bandwidth current clamp. Do you have acess to
that sort of gear?

Can you tell me a little more about the steppers and the drivers, a few pics would help.

In absence of some good test gear you might be advised to beg/steal/borrow  or buy one good driver like a Gecko and hook up your stepper. If the stepper
performs it rather tells you the original drivers are faulty or just plain crap.

Craig
My wife left with my best friend...
     and I miss him!
Re: Steppers have no torque.
« Reply #6 on: February 03, 2018, 07:29:27 PM »
Hello Craig,
           I appreciate your suggestions about the stepper drivers. I will attach some pictures of the stepper motors and drivers below. I'm sorry if the pictures arnt exactly clear, but i hope they can give you some idea of what I am running. Also, I do have access to an oscilloscope and someone who knows how to use it. If you think that my issue can be troubleshooted through testing the drivers, It would be helpful if you could provide some information on how I would go about testing the drivers. To be honest with you, I didn't even know what the drivers were until I did a quick Google search, so any details on how I would test the drivers would be greatly appreciated. Thanks again!
Re: Steppers have no torque.
« Reply #7 on: February 03, 2018, 07:42:38 PM »
something I've seen with my setup of a new cnc build, the stepper motors don't like 1/8 excitation. 1/4 or 1/16 work well. I'm trying to find out exactly why.
When the motors stall using 1/8, they turn during the acceleration phase, then stop and hum, and run again during the deceleration ramp.
Re: Steppers have no torque.
« Reply #8 on: February 03, 2018, 08:13:31 PM »
Try reducing the velocity and the especially the acceleration to a very low setting and then see if it works. I would suggest a velocity of 5 ipm and an accel of 3.

Mike
We never have the time or money to do it right the first time, but we somehow manage to do it twice and then spend the money to get it right.

Offline rcaffin

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Re: Steppers have no torque.
« Reply #9 on: February 05, 2018, 03:21:34 AM »
motors are neither like wine nor milk, they don't get better or worse with age :-)
Sadly, very much NOT true.
The old round stepper motors relied on ferrite magnets for their power. After 5 -10 years the ferrites lose their magnetisation and the stepper motor loses its torque. I have a large box of old round stepper motors of all sizes ...

But the square ones shown by OP should be OK. Me, I would guess that the voltage to the drivers is way too low. Well, that, or the drivers are cactus.

On the other hand, if that PCB in the front under a smaller one at the back, is the driver, I would have a lot of doubts about it. It looks like a really crude antique from 30+ years ago. IF I am right, it is bound to be fairly gutless anyhow. Yeah, I have some like that too.

Cheers
Roger
« Last Edit: February 05, 2018, 03:26:30 AM by rcaffin »