Centroid Community CNC Support Forum

I don't have any experience with AC servos and I'm a bit confused when it comes to whats needed to make these run, attached is the manual and a screenshot of the speed mode wiring diagram. It has a analog 0-10v for speed and direction so from what I gathered AI1 and Gnd (pin44 & 43) will go to H8 on the acorn Rev4 board for speed control. I'm guessing a external 24vdc power supply positive to the com+ (pin8) and Gnd to com- (pin23)? For the forward and reverse analog 0-10v would I be wiring them to 2 of the relay board outputs like a VFD and if so do I need a 2k resistor? If so what wattage would I need? Would I need to wire the servo on input (pin7) to the external power supply or one of the relay board outputs? Do I need any of the other inputs or outputs wired like the alarm clearance input? One last question if I do a 2:1 pulley drive to double the speed is there a way to use the motors encoder for rigid tapping or do I need a separate encoder on the spindle? Thanks for your help!

First what you need to know. Acorn only has a 0 to PLUS 10VDC analog output. It does not have a 0 to NEGATIVE output. When you use most servo drive in analog mode, they need a +/- 0-10VDC analog input. 0 to PLUS 10VDC runs the motor forward, 0 to NEGATIVE 10VDC runs the motor in reverse.
You will have to see if you can use a digital input to reverse the servo.

You don't tell us the machine type, no details about your build. I assume, like many, you are trying to take the easy way out and use a servo motor and its encoder output to do threading/CSS/Rigid tapping or possibly a "C" axis? So besides being able to reverse the servo motor, you really need to belt it to the spindle at 1:1 with a timing belt. Marc Leonard (cncsnw) I believe mentioned the caveats of using a ratio like 2:1 and want you wouldn't be able to do. (Search for cncsnw as the author. Marc is one sharp cookie and has A LOT of experience with CNC controls. We are fortunate to have him participating on our forums)

Lastly, in my limited experience using a servo motor as a spindle motor, it was challenging to tune the servo.

I'm not saying it can't be done, I just haven't seen it done successfully or properly.

Marty

Thanks Marty that will help me get going I’ve contacted the manufacturer about the direction and should get back to me tomorrow with a answer. The servo is for my G0704 mill that Im just about finished converting to cnc. Using a ac servo seemed like a good way to get more power in a small package but now that I have it I’m beginning to see your point it definitely has its challenges but I’m going to give it a go. I’ll search for Cncsnw thanks for the info.

I have the 1.8 servo spindle hooked to the g0704 with 1:1 and I am trying to wire in the encoder in the servo to the acorn. I have the direction figured out I think. I will use 4 relays controlled by 2 of the acorn relays to reverse polarity of the analog signal. what I am having problems with is where to hook the servo encoder wires to the acorn. the servo encoder has no 5+VDC only a GND A+ A- B+ B- Z+ Z- and Z open collector output seen on page 2.3.2 in the manual for the 110_06030 driver that the servo motor kit came with. what I have seen so far is that you dont hook up the 5+VDC from the driver to the acorn, but I still am not entirely sure. can anyone please help me get acorn to read the encoder?

You don't need to connect the +5V from the Acorn DE9 connector. The Drive is providing the power to your encoder, you are just connecting the data lines between the drive and the Acorn.

Yep I got the motor tuned perfectly and rigid tapping is working great

James Yother wrote: ↑Sat Dec 11, 2021 5:31 am Yep I got the motor tuned perfectly and rigid tapping is working great

Please post a video up on YouTube, share a link in the Success Stories forum.
Share the make and model of the drive you used.
Share the wiring connections used.
Share the parameter settings you entered in the drive
Post a fresh report
Post a few pictures of your machine, control cabinet and spindle motor.

Its a great way to give back for the help you received and to help the next guy wanting to do the same thing and only takes a little bit of time.
Marty