Gripper disk slips through occassionally during OPEN

[nlimpert]

In many cases the opening of the gripper fails possibly due to a certain mechanical resistance in moving the disk against the force applied by the fingers towards it.

A possible solution might be to increase the radius of the belt component of the disk to increase the leverage effect. This change would also require a new position of the stepper motor of the gripper fingers closer to the disk. This would also require the firmware of the Arduino to be re-adjusted.

[Kofferkulli]

It might be possible to squeeze in 1 or 2 more teeth on the positioningdisk. However then we would need new timing belts as it is not possible to move the stepper closer to the fingers, especially if we want to go back to using NEMA 17 motors.

The backfinger would collide with the motor.

One of the bigger factors concerning friction are the tolerances of the center bore in either positioningdisk or contact. For the positioningdisk the critical bore is the one with the needle bearing sitting inside. It might be beneficial to increase the bore by 0.1mm. But I would check first if there is a seam present inside of the bore. The seam is a result of 3D printing, and will reduce the diameter in one position. One might need to scratch or file the seam away.

3D print seam inside a bore:

(Not my picture, credit)

[nlimpert]

Thanks for the detailed explanation!

Do you believe it's feasible to change to the NEMA 17 without the need to change the belt?
And would the NEMA17 not collide with the backfinger when they'd replace the NEMA14?
If not it would be great to create a branch in this repo implementing the NEMA17 mount.