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torch vibrates when moving slow

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cruz
Posts: 21
Joined: Wed Apr 18, 2018 2:14 pm

Re: torch vibrates when moving slow

Postby cruz » Mon Jul 09, 2018 10:05 am

asuratman wrote:I had the same experience as you had. I adjust microstep on driver with higher microstep. Before was 6400 microstep, now have 12800 microstep. The motor have more torque so that no vibration.

after you changed the microsteps, did you also had to change the steps per settings in mach3?

tcaudle
Posts: 1025
Joined: Tue Feb 28, 2012 6:47 pm

Re: torch vibrates when moving slow

Postby tcaudle » Mon Jul 09, 2018 10:38 am

Increasing micro stepping does not increase torque. Most drivers use step morphing that switches to full step over a certain RPM. That is to reverse the effects of microsteeping robbing power (torque) at higher RPM where is not needed. Microstepping is not free. It circulates opposing current in the windings that help smooth out the motion. That burns power that reduces rotation torque. Some drives also employ anti-resonance that can be set to cancel out low frequency resonance.

Black Forest
Posts: 132
Joined: Thu Jan 31, 2013 11:40 am

Re: torch vibrates when moving slow

Postby Black Forest » Tue Jul 10, 2018 11:14 am

I think you should post a picture of the components in your control box. Showing what exactly you have for electronics controlling your motors.

cruz
Posts: 21
Joined: Wed Apr 18, 2018 2:14 pm

Re: torch vibrates when moving slow

Postby cruz » Wed Jul 11, 2018 3:50 pm

here are some pics,
let me know if you need more or specific pictures.

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asuratman
Posts: 4
Joined: Tue Apr 17, 2018 11:17 am

Re: torch vibrates when moving slow

Postby asuratman » Fri Jul 13, 2018 11:17 am

I read from Gecko and Lin Engineering, also I got feedback from cnczone guys, that increasing micro step will increase torque. I increased micro step from 6400 to 12800, then re-calibrate ea axis, my gantry not shaking anymore. Also I can run my motor very slow, I have tried to 200 mm/m. Before at 1000 mm/min was vibrate. I will try step by step much lower than 200 mm/m, maybe to 25 mm/m. Also Gerry from CNCZONE recommend to increase kernel freq but limited only by UCC300ETH-5LPT to 200 khz.

tcaudle
Posts: 1025
Joined: Tue Feb 28, 2012 6:47 pm

Re: torch vibrates when moving slow

Postby tcaudle » Sat Jul 14, 2018 5:16 pm

Gecko max microstep is X10. (2000 ppr) not sure how increasing micostep increases torque since the current waveform more closely approximates a sine wave that at lower steps where its closer to a modified squarewave (stepped wave) . That would indicate that the average (RMS) current is LESS at higher mircosteps.
There are formulas to calculate the loss of torque with increasing micro steps.

At 64 microsteps you need 12800 steps for one rev. of a 200 pole stepper To hit 1000 RPM you need 12800 X 1000 or 12800000 steps per minute or 213,333 steps per second, past you upper pulse limit of the driver and perhaps the software. The 1000 RPM translates to mm/min by doing the ratio math on the final drive mechanics. You need to know the linear travel per motor rev. 800 RPM is about tops for that pulse rate You may not be able to get that if the motors are underpowered for the load. . With a 3:1 reduction drive to a 25mm dia pinion you end up with about 20,000 mm/min top speed
The DM860 drivers appear to have anto resonance but I don't see a way to tune it and it does not mention step "morphing" to increase upper RPM torque (turns off microstepping

Another factor of smoothness of motion is the stability of the pulse train. Pulses generated by a parallel port are less stable meaning the pulse frequncy has "jitter" Modern step pulse cards that do not use the PC processor to generate the pulse create smoother motion and less tendncy to get mechanical resonance. Parallel Port based systems are limited on their pulse rate (pulses per second) .

cruz
Posts: 21
Joined: Wed Apr 18, 2018 2:14 pm

Re: torch vibrates when moving slow

Postby cruz » Sat Jul 14, 2018 5:21 pm

tcaudle wrote:Gecko max microstep is X10. (2000 ppr) not sure how increasing micostep increases torque since the current waveform more closely approximates a sine wave that at lower steps where its closer to a modified squarewave (stepped wave) . That would indicate that the average (RMS) current is LESS at higher mircosteps.
There are formulas to calculate the loss of torque with increasing micro steps.

At 64 microsteps you need 12800 steps for one rev. of a 200 pole stepper To hit 1000 RPM you need 12800 X 1000 or 12800000 steps per minute or 213,333 steps per second, past you upper pulse limit of the driver and perhaps the software. The 1000 RPM translates to mm/min by doing the ratio math on the final drive mechanics. You need to know the linear travel per motor rev. 800 RPM is about tops for that pulse rate You may not be able to get that if the motors are underpowered for the load. . With a 3:1 reduction drive to a 25mm dia pinion you end up with about 20,000 mm/min top speed
The DM860 drivers appear to have anto resonance but I don't see a way to tune it and it does not mention step "morphing" to increase upper RPM torque (turns off microstepping

Another factor of smoothness of motion is the stability of the pulse train. Pulses generated by a parallel port are less stable meaning the pulse frequncy has "jitter" Modern step pulse cards that do not use the PC processor to generate the pulse create smoother motion and less tendncy to get mechanical resonance. Parallel Port based systems are limited on their pulse rate (pulses per second) .


yeah i'm thinking that it's something that can't be fixed unless you change the whole setup (no Parallel Port, other motors,...).


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