G540 Trim... when do we adjust and how

[dex918]

I have my G540 installed and it is running now..

WHen do we adjust the trim and how? (I know we use the small driver to turn the preset inside).

[Fastest1]

I believe this was prior to running it. How did you calculate your current resistors? Seems like that is when I set the voltages for each stepper. Get confirmation though.

[dex918]

I am using Nema 23 KL23H-276-30-8B motor wired in parallel.
I set the current at 3A with 3k resistor. The power supply is 48VDC.

Today, I ran the G540 to cut a 6mm polycarbonate to make a bracket for the fan to cool the G540. To my surprise, it only draw up to 1.5A... why?
Is adjusting the trim affect the current draw?

[Fastest1]

Though I think it does transfer from volts to amps. I believe the setting you vary changes the voltage output to that stepper. I also wouldnt think it would draw maximum amperage unless you stalled or put maximum load on the stepper. How well did it work? Mariss?

[Dylwad]

From the G251 manual: http://www.geckodrive.com/upload/G251%20MANUAL.pdf

ADJUSTING THE TRIMPOT
This trimpot adjusts the motor for the smoothest possible low-speed operation. Set the motor speed to about 1/4 revolution per
second, and then turn the trimpot until a distinct null is noted in the motor’s vibration. This will result in the most even microstep
placement for a given motor and power supply voltage.

It shouldnt effect the current drawn. Its hard to measure actual current drawn with a PWM drive like the gecko's unless you use a scope with a very fast sampling rate. They should pull around the same current if they are stopped or running, unless they have been stopped for long enough for the auto stand by to kick in.

Lots of good info http://www.geckodrive.com/support.aspx?q=10003

[dex918]

Dylwad,

Thanks for the links.. greatly appreciated. I will try tuning it tonight and hopefully it helps...

Regards,

Dexter

[MrWild]

Originally Posted by Dylwad From the G251 manual: http://www.geckodrive.com/upload/G251%20MANUAL.pdf ADJUSTING THE TRIMPOT This trimpot adjusts the motor for the smoothest possible low-speed operation. Set the motor speed to about 1/4 revolution per second, and then turn the trimpot until a distinct null is noted in the motor’s vibration. This will result in the most even microstep placement for a given motor and power supply voltage. Lots of good info http://www.geckodrive.com/support.aspx?q=10003

This really needs to be included with the G540 instruction sheet. I was having problems with lost steps with a Rev 2 mb G540, and looked everywhere for tuning. Thanks for posting this as I hadn't thought to look at the G251 data sheet figuring if it wasn't with the G540, it wasn't with anything else.

[CoAMarcus]

MrWild,

I hear you. I am making a new manual for the G540 right now. It will be available online tomorrow or Friday and it covers the most common questions and problems with the G540. Is there anything you would like to see added to the manual? I am including a troubleshooting section, and if there are any common problems you would like addressed just let me know. I will post here once the manual is completed and up on the website.

Marcus

[kinetiq]

Originally Posted by MrWild This really needs to be included with the G540 instruction sheet. I was having problems with lost steps with a Rev 2 mb G540, and looked everywhere for tuning. Thanks for posting this as I hadn't thought to look at the G251 data sheet figuring if it wasn't with the G540, it wasn't with anything else.

I think this is my problem too. I don't seem to get any missed steps when I make a rectangular pocket at 5 IPM, but when I try and do a circular pocket, I'm getting irregular shapes due to lost steps as the axis slows to zero and then changes direction. I have backlash compensation in place. The problem seems to be directly related to low feed rates as you can hear the stepper motor smoothness degrade.

Currently the G540 manual says to run the motor at 2 revolutions per second, but on the common 0.200" pitch ball screws, that equates to (0.200" per rev * 2 revs * 60sec) 24 IPM which is no where near where this problem is occuring.

I'm going to try the 1/4 rev per second (0.200" per rev * 0.25 revs * 60 sec) 3 IPM adjustment tomorrow. Hopefully this works!

[Mariss Freimanis]

The trimpot setting does not affect taking or missing steps. It only affects motor smoothness at low speeds by adjusting the angular size of the 10th microstep to make it the same as the other 9 microsteps.

Mariss

[BanduraMaker]

Realizing that this is an old thread, I thought it was still appropriate to ask this question here.

I've got a few days before my machine arrives. I've already got my 540 and motors, but not the power supply I'll be using. Can I do the tuning process without the motors installed on my machine and with a different power supply, 20v instead of 42v? Sounds like it should work fine since it's just tuning the last step but I wanted to make sure that the mass of the gantry and the different power supply wouldn't affect the process.

Thanks

[ger21]

I'm not 100% sure, but I'd wait to do it on the machine, with the correct power supply. Steppers can act differently when mounted to the machine, especially with regards to resonance issues.

Is the machine coming this week?