Tuning stepper drivers on 3 digit SN machines.

[btu44]

The other day I was over at Geckodrives website and noticed the similarities between Geckodrives G202 and the drives in my machine.
I saw this in the G202s manual.

"ADJUST: 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."

I adjusted mine at a feed of 5 IPM and was suprised by the improvement in smoothness. All thats needed is a small stubby plastic screw driver (tweeker)

[zephyr9900]

Thanks for that tip, Barry. If you're the original owner of the 3-digit you'll probably remember the early discussion of the Tordrive 2000, an admitted OEM of the Protobyte Prodrive 2000, which was allegedly an unauthorized clone of the Geckodrive G201. So it makes sense that the same adjustment might apply. I haven't had any trouble from my Tordrives (my machine is serial 128) so I'll try the phase balancing and see if it makes an appreciable difference. I'd think that Tormach would have made the adjustment on the machine before it left the factory, but electroncs do age...

Randy

[bevinp]

[QUOTE=btu44;996647]The other day I was over at Geckodrives website and noticed the similarities between Geckodrives G202 and the drives in my machine.
I saw this in the G202s manual.

"ADJUST: 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." /QUOTE]

This might be a silly question.
How does the controller know what the micro step setting is? I assume that the controller does need to know since there is no feedback from the stepper or axis to confirm actual movement (such as that occuring with a servo drive).
Am I talking rubbish? (It's late at night here and I am too tired to google for an answer).
Thanks.

[rowbare]

This might be a silly question.
How does the controller know what the micro step setting is? I assume that the controller does need to know since there is no feedback from the stepper or axis to confirm actual movement (such as that occuring with a servo drive).
Am I talking rubbish? (It's late at night here and I am too tired to google for an answer).

This adjustment is strictly an electrical thing to get a better match between the motor and drive. Microsteps aren't necessarily linear. For example going from 0 to 1 with 10 microsteps you would expect the positions to be 0, .1, .2 ... 1. However that isn't the case, you get variations so in practice the positions might be 0, .08, .18, .31, .4 ... 1. This allows you to minimise the variation between microsteps. In practice these positioning errors are minute but tuning them out can lead to smoother operation.

bob

[zephyr9900]

Yes, the adjustment is strictly analog, to even the torque being produced by the two motor phases.

Randy

[zephyr9900]

I adjusted mine at a feed of 5 IPM and was suprised by the improvement in smoothness. All thats needed is a small stubby plastic screw driver (tweeker)

Barry, I did the phase balancing last night and there is a marked improvement in smoothness, especially on the intermediate speeds. My X was already pretty close to optimum, but Y was way off and Z was not too far off. On the jog dial, none of the intermediate speeds resonate the sheet metal at all now.

I had to cut my tweeker down--took a big section out of the middle so the ends are now only about 2" long each. The adjustment pot has a recessed shaft, so it was a little tricky aligning the tweeker with the shaft slot since I had to do it mainly by feel. (Obligatory safety notice--working in an active electrical cabinet with potentially lethal exposed voltages, don't wear bling on your wrists, make sure you know what you're doing, etc. etc.)

It was easy to arrive at the "null" by ear--typical adjustment of go in one direction until it gets noisy/vibrating, reverse past null in the other direction, go back and split the difference. It is a fairly sharp null in the vibration but easy to settle into.

Thank you very much for this tip, Barry. I'll be doing a major 3D contouring job soon, and I really look forward to seeing what the surface finish looks like now.

Randy

[btu44]

Randy, Glad to hear adjusting the drives worked well for you.
I figure the drive adjustment either drifted or was never done.
But an easy fix anyways.

Barry

[flick]

Can this be done on 4 digit machines? How? (couldnt find a pot on my drives)

[btu44]

The 4 digit machines have digital drives, thats why you see only configuration switches. So it should never drift and go out of adjustment.

You could look at this drive.

Stepper Driver C460-125D(0~80VDC) - Stepper Driver - Stepper Driver C460-125D(0~80VDC) - I.CH MOTION

I think this is a Series 2 drive based only on visuals and the specs look right, but totally unconfirmed...proceed carefully. Plus I don't see anything in the PDf that suggested any tuning is required, just initial configuration settings (assuming this is the correct drive).


Barry

[mayhugh1]

I did this to mine also a few nights ago, and the difference in smoothness is night and day. Thanks -this is a really great tip that belongs in a Tormach service bulletin. - Terry

[tbaker2500]

This is intriguing to me, and I think I'll try it.
Not fully understanding how this controller works, couldn't you lose (or gain) steps if it's incorrectly adjusted?

[bevinp]

I have serial number 109, and carried out the tuning today. The X and Y drives were in tune but the Z drive was creating noise that now is removed.

For those 3 digit guys who may be concerned about attempting the tuning, don't worry, it is quick to do and the only hard part is locating the small screwdriver into the trimpot slot.

The trimpot is the plastic component (about .2 thick x .5" wide x .4" tall) mounted on the top edge of each of the axies driver boards in the Electrical Cabinet. The User Manual has the location of the boards in one of its diagrams.

The screw driver slot (actually a Phillips head slot) is located on the side of the component facing the top of the Cabinet which is only about 2" from the board. You can use a small mirror to see the slot. I filed a single blade "screwdriver" out of a 3/8" wooden dowel. I didn't want to have a metal driver falling into any of the other components.

The actual tuning is easy as the null is very definite.

Yes I repeat the warnings about working on live boards. Just watch that your other fingers don't stray near the other boards, particularly the DC Bus board as it has VAC input (don't know the voltage).