CoreXY X axis wobble (no replies)

A while back I noticed the X axis wobbling a bit in my corexy sand table as the magnet carriage moved back and forth on the X axis (Y position fixed). I decided to check my printer, UMMD, to see if it had the same issue. It did. The data indicated that the period of the wobble was 40 mm which corresponded to the distance the carriage moves with each rev of the drive pulleys (20 teeth, 2mm pitch). I surmised that the problem was probably a poorly drilled drive pulley.

I just got some Gates pulleys from Filastruder to replace the Ali-Express specials that were originally used in the printer and the X axis wobble is gone. The Gates pulleys fit the motor shafts closely- I had to smooth one of the shafts with fine sandpaper to get the pulley to fit (some lock-tite or galling was interfering). The wobble problem was definitely due to a poorly drilled pulley. The Gates pulleys cost about $4.50 each vs the $2 each for the Ali-express crap. I'd say it's well worth the extra couple $ to use well-made pulleys.

The Gates pulleys from Filastruder are not marked in any way and the packaging is plain, so you'd never know they are Gates pulleys, but Filastruder is an officially licensed Gates distributor.

I wrote a blog post on the original problem and will be updating it with new data shortly. See: [drmrehorst.blogspot.com]