Cord cutting machine with rotary encoder problem of accuracy.Help required

[dani]

Hi,

We have a motorbike clutch and break cord roll wich is basically a hollow spring coated by pvc cover. We need to cut it at fixed length for which we have formed a The mechanical setup consist of mechanism of pulling the cord using motor bike chain coupled with an AC motor and a rotary cutter again coupled with a motor to cut the cord. The cord length is required to vary, however the cord length should be within +/- 0.5mm max. The encoder is driven by a wheel (rubberized) mounted on a common shaft with the encoder, contact between the wheel and the cord is good. We have found the accuracy problem that every time the length varies few mm. PIC microcontroller is used to interface the encoder. The encoder has 500 pulses per rev.

I want to know is cutting cord this way is a good idea or just a blunder. Or if there is any other good mechanism or we can refine the mechanism to get more accuracy.

Best Regards
Dani

 

[nandhu015]

AC Motor's dont stop instantly as the power goes off. I think the problem may be with ac motor.

My suggestion is to use some DC or better stepper motor to pull the cable.

 

[dani]

Thanks for quick reply,

The ac motor is with in-built breaks which is applied by microcontroller using a relay output as soon as desired number of pulses received. Do you still think it may be the cause of problem. What can be the solution stepper motor?.

Best Regards
Dani