[happytriger2000]

Hello all,
I have a question regarding sevo motor and drivers. When using servo motor and drivers for cnc machine, Do I need to connect the encoder pin of the servo drivers' CN1: PA+, PA-, PB+, PB- to mach3's Encoder's input (config.--->Ports & Pins--->Encoder/MPGs--->Encoder 1,2,3)?

The reason I ask is because Im having problem milling circular shapes, and Im wondering if is because there's no feedback signal from CN1 to Mach3 encoder inputs which cause the milling loosing counts leading to non-circular shape?.....need help....

happytriger2000

[ger21]

No. Although Mach can read encoder signals, it can't do anything with them unless you write your own plugin or macros. Even then, all it would be able to do is stop the machine when an error occurs. It can not operate closed loop at all.

[CarbideBob]

Mach is an open loop system. It is the job of the amplifier to keep the motor encoder synced to the pulses it is receiving from the computer.
If the machine ends in the correct spot you are not losing counts.
The problem maybe that the servos are just getting behind while moving (servo lag).
You cure this by increasing the gain (and damping if needed) in the servo amp.
Note that a servo will always lag somewhat. This is one reason you need higher resolutions with a servo than you do with a stepper.
Bob

[happytriger2000]

:rainfro: Thank you both for the reply, I will contact the supplier to solve this problem. Im currently converting a RF25 to cnc with ballscrew for X and Y, cnc machined parts for motor mounts. Just last week Servo motor supplier's staff did come to my workplace to see the problem, but no solution...Will contact him again and if with no results, then refund the item will be my last choice.

thanks

happytriger2000