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It is a new part - actually a mount for a QR extruder from Bondtech.

Nothing out of the ordinary on the part. I printed one on my Kossel 250 at the same speed and it was fine. At 1/2 speed on the Max it was fine. I know what you are talking about Brian, I run into odd issues like that occasionally too with my milling machines. I have occasionally had issues with printed parts with machine gun fire infill moves but not anything like this. I'm doing a 90° rotation and try again.

Ok, the darnedest thing. I rotated the part 90° and ran at the normal speed. This time the shift occurred on the exact same layer BUT it was in the opposite direction on the Y axis and on the X axis, it shifted over and then back to create what looks like a groove along that dimension.
The arrow is the X (cartesian) axis. You can see the groove along the right side pretty clearly. You can also see the Y (cartesian) dislocation clearly on the left side.

I ordered new belts as that's the only thing that's stock on the drive train of this machine. The Max is 3 years old so I got my money's worth from those belts.

I tightened up all the belts and made sure the pulleys were tight. It's still happening but the translation is much less. I think this might be related to belt wear. I have new belts coming and once they have arrived I will mark these belts and scrutinize them under a scope.

Rotating part made layer shift opposite way, that seems to me a .stl file weirdness.
Did you run the .stl through netfabb before slicing?
Sometimes that fixes odd slicing behaviors for me.
Run netfabb's repair function and save it back out as .stl
Even if it looks like nothing changed, sometimes it helps.

Brian,

I tried this also during my layer shift craziness, this is also one of my gotos for strange .stl behaviors that falls under the broad heading "It Couldn't Hurt". In my case it also didn't help with the shift.

My shift was always in the Cartesian Y- direction only and always negitive, never positive nor a shift back and forth. The shift would vary from just perceptible to .5mm or so. After flipping the Z column belt end for end the problem went back into the shadows. Staying this now guarantees that it will come back.

I have looked at the belt thoroughly and I am no stranger to toothed belts with different tooth profiles and have used them in application of several hundred horsepower. I did not see anything inconsistent with the belt or teeth even when flexed 180deg back to back.

I also installed DodgeDerek's Belt Tensioners at the same time (excellent piece of work BTW) so there were several things in flux, disturbed and modified but at the end of this and flipping the belt the layer shift went away.

gary

I know the STL is clean. No weirdness on 2 other printers. I've seen shifts that go one way and then the other depending on orientation but this one is very odd. It seems to be a combination of the Z tower and one of the others or maybe both just one at a time though.

Those tensioners look like they would work on a V1 too. I'm going to print one and see. If not, a slight mod and it should work. The design principle is good.

mhackney wrote:Those tensioners look like they would work on a V1 too. I'm going to print one and see. If not, a slight mod and it should work. The design principle is good.

By far the best I have tried or looked at. The adjustment wrench really amps up the cool factor also.

I like Gary's tobacco worm fix. Not sure where to obtain the worm.

An update - no worms involved.

I replaced the Y belt as that was my prime suspect. I discovered that one of the two screws that holds the arm axel to the carriage was missing. "Ah Ha!" I thought, that might cause this weird problem. I cleaned the pulley and bearings, tensioned the belt and all was ready to test. FAIL - the shift happened again.

Next I turned to the Z belt. Same routine - clean, adjust and test print. Print came out fine. This is the first print I've done since discovering this issue that has been good. The belt is "soft" around the lower section where it would engage the pulley but no obvious defects. I wonder if these things just stretch a bit, soften up and that can cause problems. More testing required. I'll make 4 more prints and make sure things are ok. Then I'll change the X belt so they are all new. I got 3 good years out of these belts.

mhackney wrote:An update - no worms involved.

I replaced the Y belt as that was my prime suspect. I discovered that one of the two screws that holds the arm axel to the carriage was missing. "Ah Ha!" I thought, that might cause this weird problem. I cleaned the pulley and bearings, tensioned the belt and all was ready to test. FAIL - the shift happened again.

Next I turned to the Z belt. Same routine - clean, adjust and test print. Print came out fine. This is the first print I've done since discovering this issue that has been good. The belt is "soft" around the lower section where it would engage the pulley but no obvious defects. I wonder if these things just stretch a bit, soften up and that can cause problems. More testing required. I'll make 4 more prints and make sure things are ok. Then I'll change the X belt so they are all new. I got 3 good years out of these belts.

I am surprised! never thought the belts would wear out in a delta application.
We should start calling the fix "nitewatchman belt flip trick"

Now this makes me want to try 9 MM wide belts, something I have been wanting to do for a long time. I was thinking better accuracy with wide belts, but maybe they would last longer also?
I would go even wider if I could find it, but 9 is widest I found so far. (ebay or robotdigg.com IIRC)
Wide pulleys are hard to find also.

Either that or twin 6 MM belts on each tower?
http://www.robotdigg.com/product/343/Tw ... h+8mm+Bore
drive pulley not directly on stepper, but an intermediate jack shaft with another set of pulleys and short belt drive to motor.
probably have pulley on shaft larger than motor pulley to gain some additional mechanical resolution.

Eaglezsoar wrote:I like Gary's tobacco worm fix. Not sure where to obtain the worm.

Tabaccy patch for sure.

Spend my young bare foot days in East Tennessee suckeren tabaccy and pulling tabaccy worms. Do not look fondly upon those years or the little cabin back in the woods

bvandiepenbos wrote:

mhackney wrote:An update - no worms involved.

I replaced the Y belt as that was my prime suspect. I discovered that one of the two screws that holds the arm axel to the carriage was missing. "Ah Ha!" I thought, that might cause this weird problem. I cleaned the pulley and bearings, tensioned the belt and all was ready to test. FAIL - the shift happened again.

Next I turned to the Z belt. Same routine - clean, adjust and test print. Print came out fine. This is the first print I've done since discovering this issue that has been good. The belt is "soft" around the lower section where it would engage the pulley but no obvious defects. I wonder if these things just stretch a bit, soften up and that can cause problems. More testing required. I'll make 4 more prints and make sure things are ok. Then I'll change the X belt so they are all new. I got 3 good years out of these belts.

I am surprised! never thought the belts would wear out in a delta application.
We should start calling the fix "nitewatchman belt flip trick"

Now this makes me want to try 9 MM wide belts, something I have been wanting to do for a long time. I was thinking better accuracy with wide belts, but maybe they would last longer also?
I would go even wider if I could find it, but 9 is widest I found so far. (ebay or robotdigg.com IIRC)
Wide pulleys are hard to find also.

Either that or twin 6 MM belts on each tower?
http://www.robotdigg.com/product/343/Tw ... h+8mm+Bore
drive pulley not directly on stepper, but an intermediate jack shaft with another set of pulleys and short belt drive to motor.
probably have pulley on shaft larger than motor pulley to gain some additional mechanical resolution.

Brian,

Twin 6's might make a lot of sense. Years ago and in another galaxy I had a problems with a 200mm wide timing belt running on a 150 horsepower milling spindle. At high speed the air being squeezed between the belt and gears would shoot out between the teeth on both sides of the belt and go supersonic in the process, the result was a siren that would rival the run up of a jet turbine. Gates got involved in the problem and suggested running 2 100mm's or four 50mm's instead. Running 4 -50's gave a noise noise reduction was dramatic! Apparently the siren effect is canceled by merging air streams between adjacent belts.

We settled on running 4 -50's and after about year - year and a half we noticed that the wear on the quad belts was much less than expected or was consistent with past wide belts. Additionally, since contrary to popular opinion timing belts do not stretch, (these belts ran on hard centers just like meshing gears) any wear is apparent by a loosening or slack in the belt and we just did see it as early. Since quality belt lengths are controlled by holding very close tolerances on tooth pitch, variation in belts lengths is very small eliminating the need for "matched" belts.

I think that this would be a good and economical solution to running wide belts and I think the services life of the belts would potentially be longer. Should be cheaper also.

mhackney wrote:An update - no worms involved.

I got 3 good years out of these belts.

Got 18 months out of mine but I also will tend to run belts tight.

Any recommendations for a confirmed source of quality belts?

I'm seeing some strange artifacts on my original v1 belts and need more for the next build. It may be best to order enough for both machines and be done with it...

I could just order from SeeMeCNC, but didn't know if others had found a source they liked better.

I don't know of anyone having issues with bad belts. These things do wear. I got 12M from tridprinting but I've also bought belts from https://www.sdp-si.com/eStore/Catalog

I run my belts a bit tight too. In fact, there is always a little black dust in the bay by the stepper.

I scrutinized the belt with a magnifying headset. It really just looks like simple wear in the high usage area near the bottom of the belt. The rubber teeth are slightly rounded over and pitted and the belt between the teeth is visible - where as on a fresh area it is covered by rubber. I am also running 15 tooth pulleys so they would wear the belt more than a 20 tooth too.

At the # of hours I've printed on these belts in 3 years, it's amazing they've lasted that long.

Thanks for the pointer to tridprinting. 12M of belt adds up and their price looks reasonable.

Anyone ever check their pulleys for wear?

I was reading another post in a forum I've since forgotten, but the discussion was how the GT2 belt profile is proprietary to Gates, but there are knock-offs that are close but not quite the same. The claim was that Gates pulleys with Gates belts or clone belts with clone pulleys were good, but it was not good to mix the different sources for ideal mate and positional accuracy.

You only need 6 for 1 rostock. I'm building a metal max and needed 2 sets! No wear on pulleys.

mhackney wrote:You only need 6 for 1 rostock. I'm building a metal max and needed 2 sets! No wear on pulleys.

6M for my first Max Metal and the other 6 for the 2nd Max Metal... twins!

Also, found these.... 20 tooth pulleys with 5mm bearings
http://www.robotdigg.com/product/637/2G ... /+Bearings

Good to know that pulley wear is not an issue. Thanks!

There you go!

I found the actual problem, not a belt problem at all. I had incrementally replaced the Y and Z belts and the problem seemingly went away. It actually hasn't reappeared. But, today I decided to replace the X belt so they are all new. When I removed the belt and started cleaning around the stepper bay I discovered this:
See the problem? The stepper mount (an AstroSyn) is missing one of the two screws holding it to the Rostock base! The stepper can actually rotate around the existing screw without a lot of force. Very interesting and a good argument for loctite!

Now if you'd just followed the manual.... *grins, ducks & runs*



g.

My rostock was assembled BEFORE there was a manual... *ducks and runs*

mhackney wrote:My rostock was assembled BEFORE there was a manual... *ducks and runs*

Sounds awful old and you should be buying some V2 printers. (My suit of armor is on)
Don't forget to download, read and understand the manual!