CoreXY X axis wobble

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]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Here's the new post on this topic: [drmrehorst.blogspot.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Interesting.

Now that I have found how sensitive a CoreXY can be, this sounds like an explanation for why vertical walls would have ridges like Ruffles potato chips.
Filastruder, for source of good pulleys.

Thanks for the tip!

be well,
DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.

No, that would be a precision problem. The error is one of accuracy, not precision. A long, flat surface parallel to the printer's X axis would have waves corresponding to the displacement caused by the out of round drive pulley(s). I have never actually seen such a wave.

The stacked potato chip Z surface is more likely caused by using a geared extruder with two drive gears. See [youtu.be]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Quote
the_digital_dentist
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The stacked potato chip Z surface is more likely caused by using a geared extruder with two drive gears. See [youtu.be]

Damn, having only received a dual-gear extruder today to replace a failing 10-year-old home-printed unit I now have a woodgrain effect to look forward to. CHEE!!

It's not that my prints have never had faults - some have had the mange and maybe smallpox; but never the weathered oak effect. Maybe I will find an artistic use for it.

Mike

Quote
the_digital_dentist
No, that would be a precision problem. The error is one of accuracy, not precision. A long, flat surface parallel to the printer's X axis would have waves corresponding to the displacement caused by the out of round drive pulley(s). I have never actually seen such a wave.

The stacked potato chip Z surface is more likely caused by using a geared extruder with two drive gears. See [youtu.be]

Like an E3D Hemera?

be well,
DLC

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Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3DHemera).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.