CoreXY print distortion?

3dmntbighker

Over the past couple of weeks I have discovered my coreXY has a pretty large offset between the motor axis. In fact when I print a 145mm test square to isolate the motors (45 degrees), the difference left to right is pretty much exactly 10mm. I just measured the installed length of the two belts at full tension and they are under half a mm difference. As far as I can see my geometry is correct and things are parallel or perpendicular. In fact the only change I made lately is Duet firmware version and some adjustments in settings to max print area. Is there someplace there could be a setting that I'm missing that could cause this? Has anything changed in Duet "corexy mode" that could be a problem in the just released firmware? When I pulled the belts my XY mechanism moves like a dream. My entire printer runs on linear rails. I have never seen this distortion in past prints. Although I have mostly printed smaller models.

dc42

Are you by any chance using steel-cored belts?

3dmntbighker

Yes, since they were called out in the BOM. But I have been on the hunt for genuine Gates since the E3D guy swears by them for their coreXY dream build. So far no luck finding them.

DjDemonD

These are genuine gates power grip 2gt betls I have them on my kossel XL. https://www.ebay.co.uk/itm/2M-GATES-6mm-2GT-GT2-RF-Fiber-Glass-Reinforced-Rubber-Timing-Belt-for-3D-Printer/141938661911?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

3dmntbighker

Hong Kong I saw those. I'll place an order. Meanwhile I put two brand new steel core belts on and I'm about to test.

Thanks

3dmntbighker

Looks like it was the belts. That's pretty shocking, but I have read plenty of stories so it should be no surprise.

Thanks

Phaedrux

@3dmntbighker I just got some Gates belts as well and the difference was subtle but noticeable compared to run of the mill belts. Steel core belts on small radius bends are a ticking time bomb.

3dmntbighker

So far I can't find any Gates belt longer than 2 meters, and that is not quite long enough. I need 7ft to have a margin . A 5 meter belt would give me two.

Monster Delta

E3d sell the gates belts on there website now they aren't advertised as gates they are just advertised as upgrade gt2 belts. I recently contacted gates about there polychain gt2 belts and they advised me that they have been replaced by polychain carbon gt2 that use carbon fibres in the core.

Phaedrux

I've used these. Might be able to get the length you need.

https://m.ebay.com/itm/2M-GATES-6mm-2GT-GT2-RF-Fiber-Glass-Reinforced-Rubber-Timing-Belt-for-3D-Printer/141938661911?_mwBanner=1&_rdt=1

3dmntbighker

@monster-delta Damn, I want those, but looking at the catalog they start at 8mm so that a means a total re-work of my drive system.

Monster Delta

@3dmntbighker I've been trying to get some but its pretty hard to find somwhere that stocks them at the moment, i was planning to run the 8mm and just change out the pulleys

dragonn

@3dmntbighker Ask them if you order more 2m if it will be one pice. As far I know it should be.

Monster Delta

@djdemond are the deffinately genuine?

DjDemonD

Well this is what they look like up close:

alt text

They look nice and they feel nice although I'd echo what Mark Rehorst (Digital_Dentist) on reprap says they don't seem to make much difference to print quality. I am running 3 lengths on my delta at around 2 meters per belt, so it's a distance over which stretch/elasticity should be apparent in substandard belts, but they seem to work about as well as chinese no-name fibre reinforced belts. I was able to discern a difference with steel-cored belts until they progressively failed resulting in weird, hard to diagnose skew.

I doubt this helps...

Phaedrux

They look just like mine.

I found that my cheap Chinese belts had a bit of a curve to the edges and would ride up and down the pulleys a bit. The gates belts are dead flat and don't travel at all. They seem more flexible and don't feel like they have as much give.

I might have just had really crappy belts.

kuhnikuehnast

Anyone already found Gates Belts longer than 2m? Would really like to give them a try but I'd need at least 2,4m each...

Monster Delta

@kuhnikuehnast just order 4 of them and they'll send you an 8m length