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chrisr

Print has holes ?

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Hi,

My first print:

Robot

Quick question, what is causing the holes or bubbles?

(The print is with PLA on all the default settings of the Ultimaker2)

I've noticed that the underside of the front belt is very loose and there doesn't appear to be any means to tighten it.

Loose belt

Has anyone any ideas on the holes and also the belt ? :???:

 

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The holes are caused by "underextrusion" meaning less filament is coming out the nozzle than desired. You can probably hear the extruder stepper skipping backwards - if you watch it on these "bad" layers you can see and hear it skip suddenly backwards about 1/8 turn (but not forwards again).

The extruder stepper current is low enough so that it will slip backwards rather than grind the filament to dust. This is desirable as grinding to dust would have ruined your print.

The solution is to either slow down the print or raise the temperature. Raising the temperature of the nozzle makes the PLA flow more like honey instead of toothpaste.

For PLA I suggest temperatures from 210C to 240C. For speeds - it depends on layer thickness. 35mm/sec is nice and slow and a safe speed.

 

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Yes, that belt is very loose, and likely to cause problems. Is the top section of that belt very tight, compared to the other belts? I fear that something may have broken in the sliding block to leave that much slack, but maybe it's just not very well positioned on the pulleys.

Use one of the little allen keys that came with the printer to loosen the grub screw in the front right pulley that the belt goes around. Then rotate the pulley a little to even up the tension between the two halves of the belt, then retighten the pulley.

 

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illuminarti, on 03 Mar 2014 - 6:24 PM, said:illuminarti, on 03 Mar 2014 - 6:24 PM, said:

Yes, that belt is very loose, and likely to cause problems. Is the top section of that belt very tight, compared to the other belts? I fear that something may have broken in the sliding block to leave that much slack, but maybe it's just not very well positioned on the pulleys.

Use one of the little allen keys that came with the printer to loosen the grub screw in the front right pulley that the belt goes around. Then rotate the pulley a little to even up the tension between the two halves of the belt, then retighten the pulley.

 

The belt has almost an inch or so of play in it and looks perilously close to skipping on the teeth. The top section is about as tight as the other belts are.

Following a nice chat with HAC, I've actually now rejected the printer and as agreed with them, it's being returned to be swapped out with another Ultimaker2.

As, I discovered that when the printer sits on a flat surface it will rock on two legs so something somewhere isn't good! The shipping box has signs of impact damage on one corner (which I didn't spot) so it would appear it may have become damaged in transit.

Shame, these things happen I guess, but I reckon in the meantime I'll just spend more time getting to grips with OpenSCAD, as I have several more projects in mind now! :)

 

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Skint, on 03 Mar 2014 - 7:54 PM, said:

Chris, that`s rubbish news, sorry to hear that! Hopefully your next one will be perfect and you`ll be up & running in no time.

 

Thanks Skint! :)

 

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