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karl

extruder shifts during the print

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hello

I have been struggling with a shifting printer head over the past day.

Im looking for some fresh views where to find the problem.

The print starts fine then the head jumps mostly along the y axis some times along the x a little.

while trouble shooting i have printed a different test print perfectly ( granted it was a smaller print).

things I have tried following other posts.

Tightening cables

drop oil on slide bars

removing oil on slide bars.

slowing print speed from 100. to 50 mms.

any suggested fixes would be greatly as Im scratching my head not knowing where to look.

thanks karl

 

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two more things to check:

- are the belts tightened?

- are the belts too tight? You would hear a quite loud noise from the stepper motors when they skip steps.

What size are the shifts? cm? mm? tenths? A picture of the shifted print might help to find the source...

 

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Is this a UM1 or a UM2? Is this a new printer?

As Dim3nsioneer said, photos would help. Oiling the rods is definitely good. With the power off, you should be able to slide the head along one axis at a time by using light fingertip pressure on both blocks for that axis at the same time. Compare the movement of the two axis, and look for any tight spots.

Could well be due to pulleys slipping, so if possible, mark the pulleys and the rods next to them with a permanent marker pen, and see if the marks move relative to one another. Don't forget to include the motor pulleys too.

 

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Photo of "bad" object please.

If it's a sudden jump it's almost certainly the pulleys - tighten all the set screws (aka grub screws) on each of the pulleys for the axis that skips. Note that each axis has 6 pulleys (SIX!). Not 4. In fact the most important ones are the 2 hardest to get to - the one on the stepper motor and the other that the short belt connects to. Tighten the hell out of these. The screwdriver should twist so hard that the shaft spirals some.

If you don't believe me you can mark all your pulleys and shafts with a permanent marker.

If the shift is more gradual then something is rubbing - usually a belt against the outer wall. Or a pulley. Or endcap.

 

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IMAG0738.jpg

hi here's a photo as you can see the print head shifted a few times on this print.

some times happens at different heights.

the shifts in this are 17mm ,17mm then 25mm .

the machine is a U1 , ok gona go through the new check list :

Mark pulleys (6)

Tighten pulleys - loosen pulleys

tighten nuts

on viewing the Layer viewer every thing looks ok, now is the layer viewer a direct image of g code (excuse my ignorance).

thanks for all the help guys ill let you know how i get on probably be tomorrow (resolved hopefully)

Thanks Karl

 

 

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The head isn't moving when it should on some of the fast moves when it goes from the end of one layer, back to the start of the next.

There are two possible causes:

1) There's a loose pulley - most likely on the short belts - that is just spinning in place when the motor moves quickly, rather than moving the belt and hence head, as it should, or

2) There's too much friction somewhere in the gantry, that's preventing fast long moves. Check that everything is lubricated; belts are seated properly and not rubbing, and that the end caps aren't too tight on the rods, preventing them from spinning freely.

Moving the head around by hand and feeling for resistance will probably help a lot in identifying any issues in the case of #2.

 

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Hi all .

First . Im very sorry for the extremely late reply.

Second . Thank for all the reply's.

so finally got time to follow a posses of elimination.

I think i have got to the root of the problem. The x axis slide blocks were not aligned properly and so far i have 2 good prints.

Armature hour :-| :-| :-|

Thanks every one for the pointers

Thanks Karl

 

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