@Luke-sLaboratory I use stacked F608 bearings for idlers in my printer- they turn very smoothly and their concentricity seems to be very good. Their 22mm diameter means I can let the toothed side of the belt ride on them without generating any artifacts in the prints. The bearings and the 8mm bolts that serve as axles are quite heavy. I expect them to last many years.

I used some cheapo 3D printer pulleys (3mm bore) in my first sand table build and found them to be junk. They wore out very quickly. A more recent version of the table uses stacked F625 bearings (5mm bore)- much better than the 3D printer pulleys.

@sinned6915 No, I am not certain the motor shafts aren't bent- I'll have to check them. One of the cheapo servomotors I used in the sand table has a bent shaft, so I suppose a stepper could, too. I originally designed the servomotor mounts with bearings and found that with that motor, the extra bearing made it run noisy, so I took the bearings out of the motor mounts.

@theruttmeister No, no preload in the linear guides.

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