I have a Taig CNC mill with steppers and a home-made driver box using Gecko drives.
Steppers with encoders for feedback are not necessary for this mill in my opinion, and only complicate and add expense to your system. First of all, shaft encoders will not improve the accuracy of your mill. Becuase the encoder is on the motor shaft, it has no way to compensate for lost motion due to backlash. What the encoder can do is tell the controller the motor did not move as far as commanded, due to load or friction or poor "tuning" of the motor. This generally tells the controller to "fault" and stop the system in mid-program.
If your stepper accelleration and max speed are set up correctly, your tables and backlash set correctly, and you don't overload the mill by taking too heavy a cut, then you should not loose steps and therefore would not benefit from encoders.
My Omniturn CNC lathe has ballscrews and servo motors with encoders. Whole different issue on this type of machine.
Ed |