Centroid Community CNC Support Forum

Hello,

I have a custom built CNC with (4) DMM DYN4 drives. 3 are for XYZ and they been working fine for about a year. I added a DYN4 1.8kW motor as a spindle. I can get 1750 RPM, which is a little better than the rated of 1500RPM. My issue is at power up, even without Acorn being started, the drive is getting -1V and its making the spindle turn very slowly. This makes it imposing to change tools without powering down.

I did reach out to DMM and they showed me to adjust the dead zone. I was able to modifying slightly, not enough to stop the spindle from turning. From what I read, this may be a grounding issue or my panel is too small, which makes the components very tight next to each other.

I am running 12.14 version of acorn. Attached is my report and some pictures of my panel, which I'm not very proud of the congestion. I've considered getting a new panel, so I can lay out everything nicely, however time factor to rewire is something I don't have right now.

If all else fails, I've considered getting a line filter or a conditioner.

Any suggestions how to trouble shoot my issue would be greatly appreciated.

Thanks,

Nick

Not to hijack your thread, just wondering if you could talk through how you communicate with a servo for providing your spindle a speed reference and how you interface with your encoder / feedback loop as per my question here - viewtopic.php?f=60&t=2437&start=40#p22901.

In terms of the issue you have, would keeping some of your cables away from each other help? In my case I try and keep high, medium and low voltage applications away from each other and try not cross if possible.

Where does your -1V come from, the Acorn 0-10V connector or on the drive itself, even if disconnected from Acorn? I had a similar problem with a VFD that I was trying to connect to, found some voltage variance depending on shielding and earthing of the shield. In the end the only way I could fix it was by using a VFD that seemed happier with the environment.

It's impossible for the ACORN to put out -1V. There must be some external bias or incorrect measurement going on.

Thanks for the reply. Forget about the -1V. I had the leads on my voltmeter reversed. My background is mechanical, learning controls the hard way.

Now back to the issue, I am simply seeing 1V output when the panel is powered on.
The 2nd strange behavior, after the panel is turned on, upon launching Acorn, this is a little burst run to the spindle motor, it winds ups for a second, still very slow rpm, but can hear it.

Therefore this is what I'm getting, see attached pictures:
0 RPM = 1V
1/2 Full RPM = 6V
Full RPM = 11V

It seems it off one volt.

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Chaz, as for your question, here is a little outline:
- In DMM its set at Analog, in speed mode.
- Gear_Num is set to 3000 rpm (theoretical max motor speed, I can only get 1750)
- Encoder is not set-up yet, doing a stepped approach to get thing going. Don't need it right now, it may be a while till I set it up. I'll check out your thread later tonight and see If can assist with anything.

Thanks,

Nick

Spindle controllers use an enable FWD and enable REV signal from the Acorn
these simple contact closure signals tell the spindle controller drive to RUN in FWD or REV and don't move the spindle motor even if there is a voltage on the analog output if there is no signal from FWD or REV.
Analog outputs will never be exactly 0. Even if they were, the analog input on the drive side will have an offset. The offset will change with temperature, supply voltage, and time so, analog outputs will have some voltage on them even when there is no command to move the spindle motor (like M3 CW and M4 CCW) the FWD and REV enable signals let the spindle drive know that it is time to move! and when the spindle drive doesn't see either of those signals..then DONT move.

i heard the DMM is updating there firmware so the DYN4 can be used as a spindle drive by Acorn, but i'm not sure on the details.. contact DMM.

maybe as a work around you could wire the spindle drive power into a contactor so you can automatically shut down the spindle drive power with M5

Thanks for the information Keith.

I've been in contact with DMM. They told me the Acorn can produce up to .6V of drift. The max I can tune a dead zone in DMM is .506V, just enough to supply low voltage to move the spindle, bummer. They are having their engineers review my case for any suggestions.

I know I asked this before, is there a filter or conditioner I can purchase to limit the low voltage?

Thanks,

Nick

the drive needs an enable/disable signal to function.
i'd consider using a typical AC induction motor and VFD and stop trying to reinvent the wheel.

Yeah, for my case what I know now vs. what I bought last year, I would not gone the route having a Servo motor for a spindle. I was trying to keep all the components the same and also told DMM with my intention of the motors.

At this point I have made the investment and need to make it work. If not, I will need to change to an induction motor. I don't believe I'm the 1st person to use a DMM DYN4 as a spindle.

Therefore, if I do go with the induction motor route with a VFD, the acorn board will still give off ~.6 Volts approx. Will I have the same issue? Or are the VFDs less sensitive and can be adjusted to ignore the voltage drift?

Thanks,

Nick

nick,
hello. please re read my post and look a the VFD hook up schematic.
as i said before spindle drives only move the motor when the enable signal (meaning it is OK to move) is active.
so for example you could have 10 volts on the analog input on the VFD and it won't move until is sees the FWD or REV signal telling it that it is time to rotate the motor.

Sounds good Keith, I will review it closely.

Thanks, Nick