PM-25MV Spindle control with acorn

[TCandee]

I am trying to get acorn to control the spindle on my mill. the mill has an AC motor with an unknown controller. It has a mechanical F-N-R switch, separate on/off pushbuttons, POT (I have identified the wiring here but haven’t hooked it up until I get further advice). The mill is 110V but the motor runs on 220 it appears. My initial thought was to wire in the acorn speed control directly where the POT is. This brings into question the common. Not sure if it needs to be isolated and with what. did some browsing on the forum but most discussions are in reference to DC Motors it appears. Maybe I am reading it wrong. Will the KBIC setup work in my case? Back to the POT. the current POT is 0-5V so I have a voltage divider to cut the acorn output in half. Still unsure about isolation.

Can the acorn control the spindle from code during a mill run? i.e.: adjust the spindle RPMs and turn off and on. Obviously, this would also require a spindle encoder that I already have but not installed. any help you can give would be appreciated.

[Centroid_Tech]

The COM terminal for the analog speed request is the same COM as your inputs which is 24V GND. I am assuming that there are 3 connections to your pot, +V, GND, and wiper. If so, you should be able to connect the GND to COM and the wiper to AOUT. Unfortunately, I do not know what the common is for the other inputs. The ON/OFF switch will be an issue because we only have a SpinFWD and SpinREV terminals. That just means that it will always have to be on, which shouldn’t be an issue because until the controller sees either the SpinFWD or the SpinREV signals, the spindle motor shouldn’t spin. Unfortunately, without a manual from that controller, I have no idea whether or not you will have an isolation issue like with the DC spindle motor controller.

The ACORN will supply a 0-10VDC analog speed voltage based on the speed that is requested. For example, let's say that you have the Maximum Spindle Speed set to 3000 rpm. When you command a speed of 1500rpm in your program, the ACORN will put out 5VDC and turn the SpinFWD output on. If you command a speed of -750rpm, the ACORN will put out 2.5VDC and turn the SpinREV output on. The spindle isn't a requirement unless you are trying to rigid tap or thread. If you install a spindle encoder, it will be setup so that the spindle speed that is displayed on the main page of the CNC12 software is the actual spindle speed from that spindle encoder.

[DICKEYBIRD]

According to the info on their website, the PM-25MV has a brushless DC motor & controller. I feel sure plenty of folks have CNC controlled that popular machine's spindle speed control. Google should help you with more info.

I took a quick look & came across this but I don't know if it's what you'd need for Acorn's analog speed control output. https://procutcnc.com/product/pm-25mv-b ... rol-board/

[DICKEYBIRD]

Another search turned up this post: https://www.cnczone.com/forums/benchtop ... 2-cnc.html Post #12 has a pic of the basic circuit. Good luck & please post you solution.

[TCandee]

Thanks for the replies. Much appreciated. I did see the pro cut/servotec board but I am not convinced that the motor is DC. Voltage readings to the motor seem to be AC. Would be nice if there was a spec plate on it. I will have to do a little more investigation. Not sure if the procut board is just doing what acorn already does or not. Haven’t found a more in-depth description of its function yet. Thanks again. I will post any findings.