Centroid Community CNC Support Forum

Hello,
I need some help with my DMM servo I have installed as a spindle motor. To be fair I bought this servo a couple years ago thinking it would be a good spindle motor for this mill. Why I thought it would be good was the weight to HP ratio was good. As some may know the Chinese made 45 mills tend to not do well with a lot of mill head weight. So instead of building a counter balance I thought this would be a decent way to go. If I had to do it over I wouldn't go with the DMM servo for the spindle motor. Its been a pain in the rear end. I would've gone with 3 phase motor and VFD. Then built a counter balance. But with that said I would like to get it working with the servo. Any help is greatly appreciated.

Problems:

1) Centroid error code 455 Spindle Axis (5) encoder quadrature error. I have built a new encoder cable using the recommended Centroid DC Servo Encoder Cable #1754. It didn't fix the error code. I've checked both DB9 pin shields are reading continuity like Marty suggested in another post. I've tried it at different speeds and it doesn't appear to be throwing an error any certain speed. Spindle reads when rotated.

2) The spindle rotates CCW when it should rotate CW. I feel like its a DC polarity issue, but I'm not sure where to swap it at? I'm afraid to burn up the drive if I don't get it right. I used the drawing DMM provided #500863 revision 3 to wire up the servo. When I contacted them they said it was the latest drawing update. The spindle is wired up to Output 5 VFDDirection, Output 7 VFDEnable, Input 5 DriveOk & Input4 SpindleOk.

3) I don't know how or where to replace the PLC code needed to keep the servo drive from faulting on shut down. I found it here (viewtopic.php?f=60&t=4981&hilit=acorn+plc+programming) in these forum.

4) Has anyone had any lucky using the DMM servo tuning program? It was pretty awful, just horrible sounding. I let it go for a little while thinking maybe that's normal. I ended up following DMM tech supports really basic manual tuning guide (see below). Seems really crude compared to other servo tuning methods or software found online.

History:
I purchased this mill that was CNC'd by Precision Mathews from a guy off of craigslist. After I got home I realized it was really slow and lost steps frequently. I purchased it and a manual lathe at about 20% of the original price. He had it for 2-3 years before I bought it. I bought 4 DMM Dyn4 servos & drives to upgrade the mill with. I bought the Acorn board early on to install on my other mill. After purchasing this mill I decided I would focus on installing the Acorn board on this mill. The X, Y & Z axis are wired up and working with Centroid CNC12/Acorn. I have a touch screen monitor and Centroid WMPG pendant working. I built a PDB and belt drive that works well so far. I haven't been able to test it in material yet. If all goes well with this mill I'll be upgrading my PM25 mill to Centroid soon.

Added information.

I've heard this story time and again....you can't use autotune on the motor with basically no load.
Have you consulted with DMM on potential settings?

Do not connect the 5V supply in your encoder cable. DMM handles power to the encoder.
Did you try connecting the DB9 shells at BOTH ends of the cable?

I *think* you can reverse the servo motor rotation in the DMMDRV software

Just some ideas. I had very limited luck trying to do what you are doing so I'm not an expert, there seems to be a few others that did have some luck. Hopefully they will chime in (Did you search the forum for DMM Spindle?)

Marty

I use the DMM autotune on my X and Y axes and the results were awful. The final values I got after manual tuning were miles different and much better.

VFDs are designed for speed control, servos for position control (primarily). The difficulty setting servos up for driving spindles seems to be mainly because they are not expected to be used for that application.

Thanks for the response guys. Marty, yes I’ve have both ends of the shield wire connected to the DB9 connectors. The are connected, I checked with my meter. Low ohmic value was metered. I did check the forums and found what you suggested, buy encoder cable, connect shields to both ends, check continuity between both DB9 shields. I did that, now I’m asking for help. I posted to see if anyone has any ideas. I seen you and others have had issues with the DMM servos used as a spindle motor. I seen this after I purchased it. I’ll connect to the driver and check if there’s a switch I missed to change rotation.

Muzzer, I agree the DMM servo tuning software is only useful for testing the wiring. Other than that you’re on your own. I won’t be purchasing any more DMM products. On my other mill I’ll be purchasing Technic.

Thanks for your help.

Marty,
For clarification I didn't use the DMM software to tune the spindle. I only used it on the Y & X and gave up on it because it sounded bad. I went through the manual tuning email I got for DMM posted above. I still get a z axis fault out every so often, after homing at 30 IPM. Its weird, it never faults while moving, just setting there? I'll tweak the tuning manually & see if that helps. I don't have the encoder 5v from Acorn connected as per the drawing above.

Muzzer,
I got sold by DMM that their servo we be a perfect spindle motor. That many people are using their servo as a spindle with great results. I would not recommend DMM to anyone else looking into servos. To many hurdles, questions & problems to get their equipment to work.

Respectfully,
D. Autry

I'm curious to hear if you resolved the fault error? Did you confirm as Marty suggested that the 5V was not hooked up on the encoder? I have a 1.8kW motor and intend to use as a spindle motor as well. Just wondering where you are at with this.

Problem 1 : hasn't been fixed. Centroid error code 455 Spindle Axis (5) encoder quadrature error is still a issue. Is still don't knowing where to replace the PLC Code. I have a friend that is PLC code savvy hopefully he can install the fix. If not I may have to pay. (viewtopic.php?f=60&t=4981&hilit=acorn+plc+programming)

Problem 2 : Spindle rotation is still wrong direction. Must be a wiring issue with the DMM drawing? Tried to flip CCW setting in the DMM driver software, no change.

Problem 3 : That has showed up with the z axis DMM servo is overcurrent fault. I'm presently working on fabricating a counter balance to install on the z axis. The overcurrent fault comes it when the z axis is lugging the mill head up to the z axis zero. I think once the counter balance is installed out on the mill head centerline it will make the servo work easier in the lifting up direction. Also by connecting the counter balance on the mill head and not the dovetail slide it will remove the drag and wear on the z axis dovetail ways. DMM support emailed me and they recommended I purchase a 30a reactor to fix. I'll look into this option if the counter balance doesn't work.

Both the x axis & y axis have no overcurrent issue and work flawless. They don't have the amp load the z axis sees lugging the mill head up.

I now have time again to work on the above problems. I will try to update what worked and what didn't.

D. Autry

vtcnc, no the 5v isn’t hooked up to the encoder cable per the drawing from DMM. That’s not the issue.

Problem 3, has been fixed. The counter balance took the load of lifting the mill head up and made it easier. No over current faults on the z axis drive. So one problem down now 2 to go.

Just completed the mechanical conversion for a 1.8kW DMM + DYN4 drive for a spindle motor. Having the same Centroid error code 455 Spindle Axis (5) encoder quadrature error. Did this ever get resolved? If so, how?