I would appreciate some help controlling a lathe spindle

[PhillyArt]

Hello all,

I had a conversation with Karl of Sherline and he told me that he has some customers that want to replace the DC motor with a stepping motor. Karl is now proving the parts to bolt a NEMA 23 motor to their chucker lathe. I have no idea where to go from here. Is so simple that I am overlooking it or am I going to need another piece of hardware to connect to the Acorn?

Regards,
Art

[cnckeith]

right now there is no direct way to control a stepping motor as a spindle motor using Acorn Axis command output.
we have this feature on the list of things to add.
i could see how you could possibly build something to take the Acorn 0-10vdc analog spindle control output and tie that to a stepper drive thru some electronic and have that vary the steps to change the speed. but, i've never done that. maybe others have?
also, Marty worked with DMM and got a DYN4 drive running as a spindle drive.

[Richards]

Using a stepper to position the spindle is simple, but to use a stepper to spin the spindle isn't so simple, at least if you would do it the same way that I would. I have a VFD connected to the 0-10v analog output on my Acorn. The VFD is connected to a 1/2hp 3-phase motor. The speed and the direction of the motor are controlled by the Acorn. All of the stepper drives that I have require step/direction signals. On Gecko drives, I have to send 2,000 step pulses per revolution. On Leadshine drivers, the number of steps per revolution depends on the switch settings selected. As an example, if I wanted to spin a motor connected to a Gecko Drive 1,000 RPM, I would have to send 33,333 pulses per second ((1,000 X 2,000 ) / 60) = 33,333. Since the Acorn uses an analog signal to control a spindle, you would have to convert the 0-10VDC from the Acorn to 0 to max steps using an analog to digital converter and a method to map the output of the AD converted to the desired steps per second. A 5V Arduino allows analog inputs up to 5VDC. A 3.3V Arduino allows analog inputs up to 3.3VDC. The Acorn provides 0-10 volts, so you would need to use an op amp to condense the 0-10VDC to 0-5VDC or a zener diode to chop off the analog signal at 5VDC. The analog input on an Arduino converts the analog 0-5VDC to digital 0-1023. You would have to multiply the digital conversion by a constant such that 1023 = the maximum steps per second desired. If you're familiar with Arduinos, it is easy and not too costly.

I've been thinking of using my DMM DYN4 750W servo as a spindle motor, but the DMM motor requires -10 to +10 volts. The speed is proportional to the voltage. The motor spins one direction if the analog voltage is positive and the opposite direction if the analog voltage is negative. Unfortunately, the Acorn only provides positive voltages. After thinking about your problem, it would be fairly simple to use an Arduino to drive the DMM servo using step/direction signals. The Acorn could output Forward or Reverse. The Arduino could use those Acorn signals to control a direction output signal and it could convert the analog voltage to steps per second and then generate the step pulse train.

An Arduino, using C++, is fairly slow, but if you insert machine code into the C++ code, the Arduino should be able to output step pulses much faster than even a servo can use.


Example:
while (1) {
digitalWrite(3, 1);
digitalWrite(3, 0);
}

[martyscncgarage]

DMM has a DYN4 that will take the 0-10VDC analog output from Acorn along with a REV signal and allow it to be used as a spindle motor.
I'm lukewarm about it. Attached is the latest info/wiring diagram I have on it.

You do need to make sure that you tell DMM you intend to use DYN4 as a spindle motor. They can be had to run on 120VAC as well.
It is a costly option however.

There is nothing wrong with the DC spindle motor on Sherline. Use a KB Electronics DC motor controller with an SI-5 signal isolator to control it using Acorn's 0-10VDC analog output. See attached Centroid Schematic on KB Electronics drive.
Marty

[Richards]

Marty,

Thanks for posting that schematic showing how to use a DYN4 controller as a spindle motor.

Since I already have a DYN4 driver and a DMM 750W servo using step and direction signals from the Acorn for use as an Axis motor, would I only need to order a modified DYN4 driver to use my 750W servo as a spindle motor? Also, I'm assuming that if I run that motor on 120VAC, that its speed would be limited to about 3,000 RPM. Is that correct? Finally, with an Acorn relay output controlling the DYN4's ENA pin, will the motor stop completely without creep? I have my eye on a CNC-ready Taig mill to make some small parts from Delrin that require tapping. The DMM 750W servo as a spindle motor could finally be put to use instead of just sitting on my test bench.

[martyscncgarage]

Marty,

Thanks for posting that schematic showing how to use a DYN4 controller as a spindle motor.

Since I already have a DYN4 driver and a DMM 750W servo using step and direction signals from the Acorn for use as an Axis motor, would I only need to order a modified DYN4 driver to use my 750W servo as a spindle motor? Also, I'm assuming that if I run that motor on 120VAC, that its speed would be limited to about 3,000 RPM. Is that correct? Finally, with an Acorn relay output controlling the DYN4's ENA pin, will the motor stop completely without creep? I have my eye on a CNC-ready Taig mill to make some small parts from Delrin that require tapping. The DMM 750W servo as a spindle motor could finally be put to use instead of just sitting on my test bench.

Call DMM with the firmware information off your drive. What you have may work. Also ask for suggested PIC settings for the DMMDRV software. Yes, 120v will limit your top motor rpm. Also discuss with DMM
Report back if you try it.
.