Gaps with ABS

colin · Post by **colin** » Sun Jul 06, 2014 1:01 am

I'm still new to working with ABS and am encountering some issues. My prints often have gaps between the perimeter and infill lines. Also, when I have small holes in my file, the print ends up going over and covering part of the hole. When I view the print preview, none of these issues appear. I'm using jimc's ABS profile - https://groups.google.com/forum/#!msg/m ... EId-LqyBsJ. Anyone have any idea how to fix this? I also included the factory file for one of my issue prints.

As always, I really appreciate this groups help!

ednisley · Post by **ednisley** » Sun Jul 06, 2014 2:04 am

colin wrote:gaps between the perimeter and infill lines

In this situation, geometry is not on your side: there's no way to fit a 0.4 mm thread (or whatever width the slicer is using) into the acute angle where those holes don't quite meet the perimeter. The slicer must end the infill thread where it touches the threads on either side, because it can't make the thread any narrower.

A similar situation occurs in the thinwall section of the second picture, where the infill threads become tangent to the perimeter wall. Because the slicer can't make the threads wider, it can't fill the slivers between the infill threads and the perimeter threads; if it moved the thread over to touch the wall, the thread would become thinner (and shorter), with a similar sliver near the other wall.

It looks as though the extruder isn't squirting out quite enough plastic: the tops of the walls look a bit sunken and the top infill of the lower plate is slightly ragged. Bump the extrusion multiplier up a bit and see how that affects the results. It still can't fill the tips of acute angles and parallel slivers, but they may become less noticeable.

jimc · Post by **jimc** » Sun Jul 06, 2014 4:33 am

ed is right. your underextruding. check you filament dia with a pair of calipers then make sure thats set right in the profile. also, as ed said you can bump up the multiplier a bit.

colin · Post by **colin** » Sun Jul 06, 2014 8:05 pm

I'll give those both a try. Thanks!

Dale Reed · Post by **Dale Reed** » Mon Jul 07, 2014 9:00 pm

Okay, so all that raises a question in my mind: Is there a slicer that can change the angle of infill as it negotiates those curves? In other words, make the infill angle be "with respect to perimeter" instead of "with respect to absolute coordinates" in such shells... I'm sure figuring out when to use one versus the other would be a nightmare of logic and trig. But perhaps some warning that a significant length of the infill is parallel to some significant length of perimeter would be in order.

Just a first-blush idea that needs some huge amount of fleshing out to make it practical.

For the OP, maybe tweaking the angle(s) of the infill to avoid "problem" angles in critical areas of the part might help. But if it's a full circular shell, you're going to hit portions where the infill is parallel to the perimeters.....

Dale

colin · Post by **colin** » Tue Jul 08, 2014 12:20 am

Dale, that sounds like a great idea but would be far over my head. Can you manually change the angles of the infill through S3D or other slicers? Or do you simply mean rotating the model slightly before I slice it?

I was able to get a much better looking print when I changed my layer height from .25-.2 and bumbling my extrusion multiplier from 0.94-0.96

I had one other question for everyone here. I have not been able to print at a layer height thicker than 0.25mm. In S3D when you change the layer height, with extrusion width on auto, I get an error as soon as I go as high as .3mm. What is the trick to get thicker layers and much quicker prints if you don't need the high resolution?

jimc · Post by **jimc** » Tue Jul 08, 2014 12:59 am

Yes you can change the infill angles in s3d. In the infill tab there is a box with the angles listed. You can change, add or subtract entries in the field box. You cant print too high a layer height because you wont get great layer adhesion. Imagine taking a couple hard round rods, this is the plastic extruded out of the nozzle. Sit one on top of the other lengthwise. They only contact in a small spot on the length of the rod. Now imagine squishing those rods together. The more they are squished the larger the contact area. This is the same as lowering your layer height OR increasing your extrusion width. Even at .25 layer height the adhesion isnt too hot. I try and not go over .2mm. If i do a .25 height i do bump up the width to maybe .55mm this helps a little. Usually like .15 or .2. If you want to go larger than .25 then you can do that but not with the .35 nozzle. You will need a .5

colin · Post by **colin** » Tue Jul 08, 2014 5:40 pm

Thanks jimc! You are always a huge help. I have mine at 45degrees, is that normal? Any recommendations for what angles I should use?

ednisley · Post by **ednisley** » Tue Jul 08, 2014 6:11 pm

Dale Reed wrote:a slicer that can change the angle of infill as it negotiates those curves

The newer versions of Slic3r have a "linear gap fill" mode that lays the fill parallel to the walls of narrow regions, with adaptive extrusion width thrown in as a bonus to soak up the small gaps. For larger areas, straight-line fill will work, because the ends of the lines should bond properly to the perimeters.

jimc · Post by **jimc** » Tue Jul 08, 2014 6:15 pm

thanks, there should be 2 angles listed. by default the angles should be 45 and -45. you can add more if you want but prob not necessary.

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