Help on distortion and incomplete fill

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Help on distortion and incomplete fill

Postby oldrayj » Tue Apr 08, 2014 8:39 pm

While most of my large scale prints are good, I’m having difficulty with distortion and incomplete fill on small parts. In the examples shown, the problem areas are about 18mm (square and round). As you can see, the hole (6mm in diameter) and the rectangular slot are grossly distorted and the fill is incomplete near the holes.

FillProblem 1.png

FillProblem 2.png


I am printing with 3mm ABS. Some of the key parameters are:

Layer height .25
Extrusion multi[per 1.0
Extrusion width .35 (1.4 times layer height)
Print temperature (Normally 230, tried 220 with same results)
Fill Density 1.0 (Tried values from .4 and up)
Print speeds are slow (perimeters 30 mm/sec, infill 60mm/sec).

I am wondering if I need a fan? All suggestions will be appreciated. Thanks.
oldrayj
 
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Re: Help on distortion and incomplete fill

Postby evil2002usna » Wed Apr 09, 2014 12:58 am

Typically circle distortions are usually indicative of a loose belt, but your bottom circles look ok. Too me this looks like an adhesion issue. When your extruder is printing the top circles, does the plastic stick to the previous layer well. If it is doing that, I would then check the voltage on your steppers to make sure they are not skipping steps.
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Re: Help on distortion and incomplete fill

Postby oldrayj » Wed Apr 09, 2014 1:14 pm

Thanks for the input. The layers, except in close proximity to the holes, are rock solid. Also, belts and voltages are OK. If I have an adhesion problem, what is a potential solution? Thanks again.
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Re: Help on distortion and incomplete fill

Postby fma » Wed Apr 09, 2014 1:30 pm

I think you definitly need a fan! On a small part, the hotend stays longer above, and keeps it very hot. Then, each new layer tends to twist the part, and you can get such mess...

As you print in ABS, use very little airflow; using following design is best:

http://www.thingiverse.com/thing:292663
Frédéric
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Re: Help on distortion and incomplete fill

Postby oldrayj » Wed Apr 09, 2014 6:25 pm

Looks like a fan arrangement is the solution. I tried to print a 6mm hollow cylinder. It was a gooey mess. I could observe the molten plastic being distorted. Thanks much.
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Re: Help on distortion and incomplete fill

Postby evil2002usna » Wed Apr 09, 2014 10:13 pm

In addition to a fan you may need to print slower. If you are using Reptier Host, try to enable auto cooling.
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Re: Help on distortion and incomplete fill

Postby butterfingers » Thu Apr 10, 2014 4:11 am

+1 on the fan. Looks like your extruder is dragging the soft plastic off before it sticks fully.
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Re: Help on distortion and incomplete fill

Postby oldrayj » Thu Apr 10, 2014 12:51 pm

Thanks all. I have ordered some fans.
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