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ABS print bends and creates cracks (not at bed level)

Posted by barakori 
ABS print bends and creates cracks (not at bed level)
June 09, 2014 11:57PM
Hi,

Trying to print the Hinged Treasure Chest with Latch from [www.thingiverse.com]

I'm printing with ABS @ 225c / 110c with hairspray and (at least in this time), have no issue with curling
at the bed level.

The problem is that curling happens above (e.g. at z = 1cm), which causes layers split. This looks like
cracks in the final print. Here's how it looks like:

Front view:


Side view:


How do I prevent this from happening? Any suggestions on what might be wrong? Settings?

Thanks.
Re: ABS print bends and creates cracks (not at bed level)
June 10, 2014 04:41AM
That is the typical height at which ABS is vulnerable to cracking and splitting. Often caused by cool draughts around the printer and is the result of the upper layers cooling quicker than the bottom layers which are bathed in heat from the heat bed. My solution was to build a cabinet to enclose the printer and keep the heat in and the cold out. You could try putting a large cardboard box over the entire machine and see if that helps.


_______________________________________
Waitaki 3D Printer
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Re: ABS print bends and creates cracks (not at bed level)
June 10, 2014 01:38PM
It is interesting, because 1 cm above a bed is so little. It could be also caused by bad filament or bad layer height! I thing it is a bad quality of filament and I think it could be solved by box.
Re: ABS print bends and creates cracks (not at bed level)
June 11, 2014 05:34PM
This is due to uneven shrinkage. The top is hot because of hotend, the bottom is hot due to heated bed but the middle is cooling and causes shrinkage and thus cracking. This is a well known issue. You need an enclosure around your machine to prevent this so hot air stays inside. I use an enclosure made of PVC pipe and thick (but cheap) plastic sheets used by painters to cover floors and furniture to protect from paint. I also use a small heater inside when printing important or tall items.

So either you control the temperatures around the print with some method or you switch to something like PLA that does not have these issues.
Re: ABS print bends and creates cracks (not at bed level)
June 14, 2014 11:48AM
i dont have an enclosure either and can print abs at least smaller objects(6 inches or less). i had some abs that needed alot of heat i went as high as 250c and it fixed the problem. it depends on color of filament and what brand i use.

also make sure you dont use a fan to cool print
Re: ABS print bends and creates cracks (not at bed level)
June 14, 2014 12:30PM
I print at 270C, just throwing that out there for comparison's sake.


Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus
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