Cut to Length Application

Hi..
For cut length application, how to define accuracy of cutting length (we need +/- 1mm)? I used compactlogix with 2048 ppr encoder and measuring wheel diameter is 127mm. The drive unit is using ControlTech Unidrive SP2402 c/w dynamic braking resistor and vector motor. Maximum speed is 30 MPM, maximum cut length is 1800 mm. How to convert pulse to length?
Compactlogix will generate speed ref to unidrive and if actual length reached 90% and motor speed will slowdown and stop if actual length reached setpoint.
Any idea or suggestion?
Thank you.
James

You count the pulses per unit of measure. IE 200 pulses per 10 MM. Then have the control count the pulses. You will need to put cut values into memory locations and use compare functions of desired length. when you achieve the 90% you initiate a decel and creep into the stop point. You may need to have a back into position if excessive over shoot occurs.

BTW, you may get better results using a 4096 count encoder. More counts can provide better resolution/accuracy.