Graphite Sheet Cutting Machine

Is there any backlash in your gearing (between the motor and the conveyor)?

Who set up the servo system?

Thanks. We have used timing belt between output of Servo motor and conveyor shaft. No backlash is there. Servo system set up by the vendor we procured the system from.

Are you sure that it's the conveyor that's moving the wrong distance (i.e. is there any slippage between the conveyor and the sheet)?

If the conveyor is not moving the correct distance, it sounds like the vendor didn't know what he was doing. Have you contacted him/them and complained that the system doesn't work?

You have a servo motor in your system but is the system a servo system with something reading the position of your product to be cut? This digital encoder or potentiometer can easily be the root of your precision problem. Regardless of this being an analog or digital feedback system a 1mm variation of a 200mm maximum is a 0.5% variation. This is a relatively coarse level of precision but not an unreasonable level of precision for many systems.

Assuming that the system design is capable of your desired precision, I'd investigate if there is any slippage or backlash between the servo measuring instrument and the sheet.

Is there any play on blade shaft? Backlash must be checked with many times the expected load, including acc/dec and friction. Because that repeatability is more like a tractor on a field on NC context. Also did you contact the one that did the servo-amp tuning? S.M.

Another question - is the positioning error always in the same sense? i.e. are the strips always too narrow, or too wide, or does it vary?

Is the conveyor belt also a timing belt? If not you have some slippage between the conveyor shaft and conveyor belt every time it starts, possibly every stop as well. You could try varying the acceleration and deceleration of your servo motor to attempt some control of that.Same thing with slippage between your sheet and the conveyor belt. This may affect your cycle times though.

Another thought is to use an analog sensor to track the leading edge of your sheet as feedback to the servo. keyence is a good source for that type of device.