Dual motors on y axis create noise and oscillation

[Quinn the eskimo]

I have an acorn rev3 connected to dmm dyn4 1kw drives and motors .

It’s for a 5x10 router table with two drives on y axis.

My auto tune of z and x performed great.

Y axis I cannot auto tune because you can’t tune both motors at once.

I think my gantry and z axis weigh about 600lbs total. Its got 18” of gantry clearance and it made of cast iron and steel and aluminum 1/2” plates.

When I jog the axis in cnc12, it moans and groans as it moves and eventually both motors will go into fault.

My gantry is square, I moved it 5 feet from side to side and it never moved a millimeter.

What’s odd is that if I disconnect either one of the motors, the single motor runs smooth without feedback. It will go into fault when asked to fast jog at 100 Ipm but that’s to be expected of one motor doing 2 motors work.

Why do the pair of motors together create such feedback and resistance to one another even though the gantry is square and smooth moving, and the y axis is certainly reversed for the second motor in the Cnc wizard.

I’ve been trying these values on my motor tuning :

Main gain 40, speed gain 40, integral gain 1 - creates noise, oscillation, then fault
Main gain 48, speed gain 43, integral gain 1 - creates more noise, more oscillations and sooner fault
Main gain 40, speed gain 40, integral gain 5 - same noise and oscillation, might have faulted soone
Main gain 55, speed gain 55,integral gain 1 - tremendous noise and oscillation. Fast fault time

My x values are 48,43,1 and that was what the auto tune feature came up with. It’s smooth but has some slight noise. I figured my x axis weighs about half of the gantry total weight, so each of the y axis motors should be a bit stronger in gains than the x?

Also , I’ve had cnc12 set to 200,000 steps per and by switching to 100,0000 I get half as much noise, and switching to 400,000 steps makes it impossible to operate

[cnckeith]

sounds like the two motors are fighting each other.

use 100,000 step freq when debugging... its the last thing you increase after everything else is running good.

[Quinn the eskimo]

I switched to 100,000 steps per and that attenuated some of the noise for all different settings. It added a bit of jog time as well before fault, but none the less I’m still doesn’t like those gain settings.

Fault will happen after 10-15 seconds of fast jog at 100ipm.

I just tried main gain 44 speed gain 48 integral 1 and it seemed happier but then failed.

Do just keep moving up? If I’m throwing more gain so the fault doesn’t happen, how to I settle down the chatter and noise?

[Mkelcy]

Contact DMM. They are very helpful and reply pretty quickly.

[Quinn the eskimo]

Yeah, it’s a holiday here so they are closed. Was looking for some forum support until then

[cnckeith]

yeah, i wasn't suggesting that 200k was the issue. so no surprise there.. i was suggesting leave the step freq at 100k while figuring out the drive tuning. and yep good advice to call DMM on how to tune thier drives. post photos of the machine to an album and place link here ..this may shed some light on the subject as well.

[ack11]

Im running a 2x3 meter router with dual 1kw DMMs on the Y. When i autotuned them it was scary and unpleasant but i only had 1 bolt into 1 truck and stood on the other side trying to keep up. Wich i couldnt but point was to let the tuning side feel the weight that it should and have the gantry slide/rotate whatever i couldnt compensate if that makes sense. It doesnt travel very far when auto tuning. Cant really recommend this way but thought id share what i did atleast.

And i agree, more pics or video!

[martyscncgarage]

DMM says they can help with tuning a slaved gantry. Give them a call....and report back.
I have not been able to reach them in a week. Tell them Marty isn't happy.

[marks3465]

Quinn,
Your gains are set way too high, they should be around 15 to 20. That should make them less noisy. Also you can toon Y axis no problem. Just make sure one drive is not on. The motor tuning will move the gantry back and forth using one motor to tune it. After one is done do the other slave or master the same way. When you have the gains that high it makes the servos way too rigid and they fight each other.

[slodat]

When I tried doing this my gantry racked severely and I stopped before it caused damage. What do you have for gear reduction on the Y axis?