How to improve density and eliminate gaps in a print?

Help with printing with specific plastic filaments.
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ndpmcintosh
Posts: 8
Joined: Fri Oct 11, 2013 4:45 pm

How to improve density and eliminate gaps in a print?

Post by ndpmcintosh » Fri Nov 01, 2013 12:17 pm

Hey all;

I am working on my first actual design-and-print project which is a cabinet replacement knob in ABS designed to take a #8 screw. The plan is to tap the hole but I may also just try a sheet metal screw directly. The basic shape is correct but the print always comes out with a gap somewhere in the exterior surface. I've attached a photo.

Also, what SLIC3R settings are best for trying to get as dense an infill as possible for the screw to be securely fastened?

Thanks,

Phil...
Attachments
Knob_with_hole_prototype.JPG
How to prevent gaps like shown in the photo? Is that a slicer setting problem? A z-axis home position problem? A z-axis mechanical problem? Or...?

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gannon
Posts: 47
Joined: Wed Jul 10, 2013 11:42 am

Re: How to improve density and eliminate gaps in a print?

Post by gannon » Fri Nov 01, 2013 12:32 pm

What size nozzle do you have an what is your layer height? Looks like the filament didn't stick on a layer and got dragged by the nozzle.
I would try decreasing the layer height and trying again.

ndpmcintosh
Posts: 8
Joined: Fri Oct 11, 2013 4:45 pm

Re: How to improve density and eliminate gaps in a print?

Post by ndpmcintosh » Fri Nov 01, 2013 2:04 pm

Thanks. Yes I decreased it and it improved. Nozzle size is .35. A little more tweaking there will probably get it. But, I am worried about the support around the hole. Is there a strategy for making the inside of an object fill in as fully as possible? 100% fill?

Phil...

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gannon
Posts: 47
Joined: Wed Jul 10, 2013 11:42 am

Re: How to improve density and eliminate gaps in a print?

Post by gannon » Fri Nov 01, 2013 2:31 pm

I would adjust the overlap between infill and perimeter, but this isn't an option in slic3r as far as I know.
You may be able to adjust the extrusion multiplier to fix the issue though.

bam
Posts: 117
Joined: Thu Sep 19, 2013 11:37 pm

Re: How to improve density and eliminate gaps in a print?

Post by bam » Fri Nov 01, 2013 3:42 pm

ndpmcintosh wrote:Thanks. Yes I decreased it and it improved. Nozzle size is .35. A little more tweaking there will probably get it. But, I am worried about the support around the hole. Is there a strategy for making the inside of an object fill in as fully as possible? 100% fill?

Phil...
You can adjust the infill density in slicer, 90% is sufficient for most parts.

It looks like the problem is that not enough plastic is being extruded; the most common cause of this is bits of filament clogging a few of the teeth on the hobbed bolt. The clogged teeth won't be able to grab the filament, so the extrusion gets thrown off by quite a bit.

I'd check and clean the teeth of the hobbed bolt in the extruder, and decrease your print speeds a bit if the problem comes back. That should keep the filament from stripping.

You can also print at higher speeds without stripping if you go up to a .5mm nozzle. You'll lose a bit of resolution, but the increase in speed and reliability makes it our nozzle size of choice here at AOHQ

Hope this helps!
-bam

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