Layershift headaches

Hi,

so i tried building a 3d printer, and ive gotten some prints with it. But its got a lot of flaws, so im gonna build a new one with a lighter carriage etc.

But for the new one, i need to get the current one to print me the parts i need :p

So i can print a 30x30x20mm cube with 1 outline fine. No layshift, and everything straight as possibly can be. But as soon as i start printing the more complex stuff with infill etc etc, i get layershift, And its always in positive Y direction.

Its currently a belt system on my Y-axis, with a 24 tooth GT2 pulley and 9mm wide belt. Running on a nema 23 motor, with a external driver, connected into a RADDS 1.5.
And its running repetier.


It was a leadscrew system, but it stalled very easy with fast direction change due to high rpm needed, so i swapped to a belt. But it seems thats also giving me a headache.

So my question is this, do i need the same diameter on pulley and idle wheel?

Anyone have any suggestions on what can be the problem?

Check the tension on your Y axis belt or the drive pulley itself. You may have some slop in the belt so it's not driving the Y axis accurately at higher speeds.

Edited 1 time(s). Last edit at 10/22/2016 01:59AM by Rlewisrlou666.

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Out of the box thinking is easier when you never fitted in the box to begin with.

Ive tried printing it at very slow speeds tho, like 20mm/s but there is still a layshift.

But its proberly the million dollar question, but how tight should the belt be? If i squeeze the belts together, should the belts be so tight i cant touch the belts?

Try reducing acceleration and jerk.

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

I think i actually found out what it was, im using on of these eye bolts as my method of tightening the belt. And in doing so, i just superglued the belt in a loop in the eye bolt. But in doing so, i created room for the bolt to be loose. So i used a zip tie, and got it all tight and nice.

But while lvling my heatbed, i managed to short circuit something, and i need to swap out a circuit on my udoo quad. So yay.... cant test my fix for a good week

I have not been 100% accurate in creating this axis. And the motor drive pully and the idler pulley is not 100% aligned. Is this enough to create layer shift?

No, the belts should not be so tight that you can't deflect them. Pulleys should be aligned to prevent belt wear.

Post pictures of the prints and the printer.

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

beltwear im not really worried about, seeing i got 10m of 9mm gt2 belt laying around, and i am swapping to 6mm when i actually get the parts printed for the new printer

im almost embarrassed to show my printer, it is such a mess with the carriage atm, ive been trying lots of things, and in doing so, its a propper mix of aluminium, plastic, and plywood :p





the layershift has always been that direction, in positive Y. Except once, where i had my belt very tight, then it was in negative-Y.

This is really annoying, i only need it to print out 25 parts or so, and i can dismantly my monster of a printer :p

Get rid of the spring-type belt tensioners on the left side of the extruder. Belt stretching is a problem because it makes the belt act like a spring. Adding springs to the belt makes it act like a spring, too. For any given amount of force, 6mm belt will stretch more than 9 mm belt.

The belt appears to be twisted in some sections. That suggests that there is interference on the belt path. Fix that. The belt should not touch anything but the pulleys and extruder carriage. If a pulley flange is causing the twisting, reposition the pulley so that the belt doesn't rub on the flange. Make sure the pulley axes are parallel.

In the picture it looks like the two variable length belt segments at the bottom (the two that attach to the extruder carriage) are not parallel to the X axis guide rails. Fix that. They must be parallel at all positions along the X axis or your prints will be distorted.

The Y axis moving mass (X axis, belt, pulleys, Y axis bearing blocks) is much higher than the X axis moving mass (belts, pulleys, and extruder carriage), so it is no surprise that layer shifting occurs in the Y axis. Make sure motor current is adequate (typically about 80% of rated motor current). If current is good, slow down print speed and/or reduce acceleration and/or reduce jerk and/or some combo of the three.

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

wowsa, thats an awesome reply. I cant believe all the info you can see in that picture


I think i have to try to redesign the whole belt system, if i use larger pulley and idler wheel i will have larger room between whatever method i will use for tightening and the belt itself.


Greatly appreciate all your help!

Suffice to say, recreating the y axis made all the difference, its now 98% straight and parallel and the prints are comming out good enough. Some problems but nothing that has to be remade.

Thanks for the help