@hurzhurz @T3P3Tony

Thanks for you help guys, we have a winner!

My new tough metal core belt turns out to be not so tough and must have softened (probably from friction/heat) at some point and has actually stretched in the area over the toothed pulley.

I checked the movement as @T3P3Tony suggested and it was elongated near the centre of the bed's Y axis but not towards the edges. After @hurzhurz mentioned his issue with his Anet belts I then went and checked the belt and found this:

You can actually see where the rubber has stretched and increased distance between the belt's teeth!

Thanks again for everyone's help - turned out to not be a duet related issue at all but you guys got me looking in the right place.

That looks like it’s done the trick, thanks!

Left cylinder printed with default bang bang for the heated bed and then with the Pid tuned values for M307 (and voltage compensation) on the right

I was printing a TPU Tyre for an OpenRC build and suddenly it started printing longer in the Y Axis. I let it finish as at the time it looked like a minor layer shift but it actually started printing very consistently larger and slightly offset in the Y axis.

After checking the mechanics over I have it another shot only to find the 2nd wheel was entirely longer in the Y axis with no signs of layer shifting!

I figure if it was just layer shifting or slipping belts then it should actually shift in one direction and/or get smaller, not longer? But this seems to be a very consistent increase of about 2-3% size in the Y Axis alone. So now I’m wondering if it’s a possible software or electronics issue.

I’ll keep looking for mechanical faults as I still think it’s most likely that but has anyone experienced something like this before?

Using a DuetWifi on firmware 1.21

I've added some pictures for reference

@phaedrux Thanks for the link Phaedrux. Just ordered some myself.

Judging from the images you've posted, even if they're "fake Gates" they look pretty good quality.

Also, an fyi for everyone/anyone - i've gone and edited the reprap wiki page on choosing belts to include a wee warning about steel core polyurethane belts and small pulley diameters for others to find.

Link here: https://reprap.org/wiki/Choosing_Belts_and_Pulleys

@phaedrux Thanks for the link Phaedrux. Just ordered some myself.

Judging from the images you've posted, even if they're "fake Gates" they look pretty good quality.

Also, an fyi for everyone/anyone - i've gone and edited the reprap wiki page on choosing belts to include a wee warning about steel core polyurethane belts and small pulley diameters for others to find.

Link here: https://reprap.org/wiki/Choosing_Belts_and_Pulleys

@plasticmetal had I seen that advice before I might have been able to avoid this whole thing!

I suspect that’s what has happened, pulling the belt apart in my hands it snapped pretty easily at the point where it was engaging with the pulley while the rest of it was still pretty solid.

I had some spare rubber belts so I’ve gone back to those and all seems to work well again.

@hurzhurz @T3P3Tony

Thanks for you help guys, we have a winner!

My new tough metal core belt turns out to be not so tough and must have softened (probably from friction/heat) at some point and has actually stretched in the area over the toothed pulley.

I checked the movement as @T3P3Tony suggested and it was elongated near the centre of the bed's Y axis but not towards the edges. After @hurzhurz mentioned his issue with his Anet belts I then went and checked the belt and found this:

You can actually see where the rubber has stretched and increased distance between the belt's teeth!

Thanks again for everyone's help - turned out to not be a duet related issue at all but you guys got me looking in the right place.

Looks like my post last night didn't go through before the forum went down for a bit?

Anyway I tried another print after changing the steps per mm in the Y from 100 to 100/104 (~96) and got a perfect 100x100mm test print - I suppose that's a working solution.

@hurzhurz I did change my belts to a metal core GT2 a few weeks ago but have done maybe a dozen prints without issue and the heated bed was actually off for the print when things went wrong (since I'd never get the TPU print off of my PEI if it was on!) - but that's a good place for me to check. I did notice a bit of dirt on the belt where it engages with the pulley (it's a white belt so it's easy to spot) so who knows, maybe the teeth on the belt have slipped?!

In the office atm so i'll check again tonight.

Thanks for everyone's input so far.

Alright first calibration print done.

Ignore the horrible over extrusion on the lower layers!

100x100mm square came out as

100.00mm in the X and 104.02mm in the Y which roughly matches up with the measurements I took of the wheels.

XAxis

YAxis

I'm going to clean the printer up a bit and try Prusa's Slic3r (prints so far have been sliced with Cura) to rule that out as well.

Edit (23:04): Same result with Slic3r (although it did a much better job with flow control on the bottom layer solid infills) 100X by 104Y mm.

@t3p3tony cheers for the response - Yeah I should have probably mention that I do have a cartesian setup (P3SteelXL, basically a very heavy Prusa i3) finally got the kids to bed so I'm going to try some calibration prints. Not seeing M556 or M92 in the code file itself and steps/mm for both X/Y are the same value of 100 for M92 in the config.g (GT2 Belts, 16 tooth pulleys, 1.8 degree motors and the default 16 microstep)

I've taken some calliper measurements of the tyres since I realised I didn't actually know how elongated in the YAxis the model became.

• 1st wheel I printed (which came out perfectly) I get ~56.5mm diameter
• 2nd wheel (which shifted to the elongated Y about 2/3 of the way through the print) I get ~56.5mm diameter for the first 2/3 and then ~56.5mm in the X and ~58.5 in the Y
• 3rd wheel (which is elongated in Y for the entire wheel) I get the same measurements as the last third of the 2nd wheel (i.e. 56.5X 58.5Y)

I'll let you know how my calibration prints come out!

@dc42 The correct size is the lower part (circular) rather then the upper part (oval) which is why I'm confused by the issue - every mechanical issue I've had in the past, like loose belts has resulted in smaller prints or shifted prints, not consistently larger (in one axis)?

I have checked the belts though and they're pretty tight - will try run some test prints tonight.

@Catalin_RO Did you start responded in the wrong post?

I was printing a TPU Tyre for an OpenRC build and suddenly it started printing longer in the Y Axis. I let it finish as at the time it looked like a minor layer shift but it actually started printing very consistently larger and slightly offset in the Y axis.

After checking the mechanics over I have it another shot only to find the 2nd wheel was entirely longer in the Y axis with no signs of layer shifting!

I figure if it was just layer shifting or slipping belts then it should actually shift in one direction and/or get smaller, not longer? But this seems to be a very consistent increase of about 2-3% size in the Y Axis alone. So now I’m wondering if it’s a possible software or electronics issue.

I’ll keep looking for mechanical faults as I still think it’s most likely that but has anyone experienced something like this before?

Using a DuetWifi on firmware 1.21

I've added some pictures for reference

M501 /facepalm.

Yeah that was missing, and had it been there this whole time the OP issue wouldn't have happened

Massive thanks, pid tuned values loading up from config-override.g correctly now and both H0 and H1 have voltage values in there now as well!

Thanks for the follow up. I’ve run tuning again for the hotend and M307 H1 is showing a value for V now (24.2) - presumably that’ll improve things even further after ensuring the bed was running with pwm?

And I guess M307 H0 being ignored in the config override must be potential a bug?