01-18-2020, 10:14 AM
Hello everyone,
just wanted to report that one of the solutions found by a user and described on his blog (using a pair of F8-19G axial bearings) does not work. I tried to exchange the bearings but even, if they fit, the rotor will not turn because of friction. Even if you try to use just one F8-19G at the bottom the rotor still will not turn. However I would like to confirm that the problem is mechanical because the spring washer allows for some axial play. Since the plate goes up and down each cycle the spring will relieved and compressed continuously yielding (slightly) different result at each re-positioning. The error may be attenuated by using a stronger spring but this will increase load on the radial bearings.
The only way to resolve this completely (and achieve accuracy around +/- 0.02) is to redesign the Z axis linear actuator using separate bearings for the lead screw, an elastic coupling for the stepper AND a linear encoder. This way the axis will not rely on motor bearings (there is an increasing trend nowadays on using motor bearings as load bearings...
), the elastic coupling will accommodate for any motor misalignment (so the motor bearing will not suffer) and the linear encoder will ensure accurate positioning.
I realize this would be a completely different printer with a much higher price tag and it would still be uncertainty about the behavior of the FEP film (an elastic build surface on a rigid machine...).
just wanted to report that one of the solutions found by a user and described on his blog (using a pair of F8-19G axial bearings) does not work. I tried to exchange the bearings but even, if they fit, the rotor will not turn because of friction. Even if you try to use just one F8-19G at the bottom the rotor still will not turn. However I would like to confirm that the problem is mechanical because the spring washer allows for some axial play. Since the plate goes up and down each cycle the spring will relieved and compressed continuously yielding (slightly) different result at each re-positioning. The error may be attenuated by using a stronger spring but this will increase load on the radial bearings.
The only way to resolve this completely (and achieve accuracy around +/- 0.02) is to redesign the Z axis linear actuator using separate bearings for the lead screw, an elastic coupling for the stepper AND a linear encoder. This way the axis will not rely on motor bearings (there is an increasing trend nowadays on using motor bearings as load bearings...
), the elastic coupling will accommodate for any motor misalignment (so the motor bearing will not suffer) and the linear encoder will ensure accurate positioning.I realize this would be a completely different printer with a much higher price tag and it would still be uncertainty about the behavior of the FEP film (an elastic build surface on a rigid machine...).