View Full Version : Getting into servo motors

06-01-2003, 11:26 PM
Now that I have built a couple CNC machines using steppers I'm curious about getting into servo motors. What do I need in the way of software and hardware.

06-02-2003, 11:39 AM
Jim, Your same software for step and direction control with work fine for a servo system. I have had very good luck using the Gecko G320 drives with my servo motors to run a drill/mill and now a new router. You will find with servo's a world of power and speed over stepper motors.

One other added bonus of using a G320. You will get a closed loop system back to the driver. No more worry about loosing steps and not knowing about it.

06-02-2003, 01:28 PM
Hi Jeff;

What kind of servo ,motor should I be looking for. Probably want to stay with DC motors, right?

Turbocnc will recognize encoder feedback from a servo motor? That would be amazing.

I emailed you about the servo motors you have for sale this morning.

Sounds like I'm following your foot steps Jeff.


06-02-2003, 01:36 PM
You said "closed loop back to the driver". What about the software? Does the control program need to know about a difference between commanded and actual position?
Or does the driver handle the error and the program doesn't need to know?

Having asked the question and mulled over possiblilities it occurs to me that the control program not only doesn't know about tool slippage, in most (stepper) cases it doesn't care either. It just spits out commands and assumes that they are obeyed :) . It is on the operator to make sure the work piece is not a scrap piece.

Does software designed specifically for servo systems act differently?

robotic regards,


06-02-2003, 04:36 PM
Jim, If you are going to use the G320/G340 drive then you will need a DC BRUSHED motor with a 5V encoder on it like the E2 from USdigital. This is the encoder I use on my servo motors.

Tom, The servo system is closed loop back to the drive because the drive has a buffer built into it and will keep the step commands processing. If you are pushing the limits of the machine and the step command fill the buffer and the computer is still sending more the drive will fault and stop. The PC will not know this has happened so you will then need to stop the controller software. The benifit to me is the fact that if you do overload the system and the drive faults you will know about it. If you do this with a stepper system and you skip a few steps you my not know about it until your job is done and then find out your part is wrong!