# Fill doesn't reach perimeters on supports (Simplify3D)

My Tevo Flash works well. Right now, I'm trying to print a thin, disc-like part on supports. The 3 perimeters at the edge of the disc are OK. The dense fill zigzag pattern makes many U-turns near the perimeter. It all looks OK in Simplify3D. But in the printed part, in several spots, the zigzag pattern doesn't reach the perimeters, leaving a ~1 mm gap.

My guess: in those spots, the filament has nothing to grab onto underneath, so the U-turn region is dragged back by the nozzle a bit (away from the perimeters) and/or it droops. I'm using the smallest support res in Simplify 3D: 1 mm. Any options I can try?

• I think you are right, not enough support. I'm not using the Simplify3D slicer so I cannot answer for this specific software, but in Cura you can create a top layer over the support creating a platform, this helps me much with hot printed filament and support structures, maybe Simplify3D has a similar option. You possibly can also increase the overlap of the infill over the perimeters.
– 0scar
Jun 14 '21 at 13:36
• Cura calls this layer an "interface" and offers it for both top and bottom of supports. Jun 14 '21 at 15:38
• Nice sketch, by the way -- not many people have the skill and expend the effort to draw clearly with pen and paper any more. Jun 14 '21 at 18:12
• OK, thanks. What I did: I added a layer of ONLY perimeters, UNDER the ones in the sketch, wider (6 instead of 3), same radius on the outside, but extending more INWARD towards the center. They don't interfere with the function. Now it works, the fill "catches " on the lower perimeters Jun 15 '21 at 2:57

Posted as a wiki answer from a comment from the OP to a different answer.

The Zig Zag vs Lines patterns was only a part of the problem. The 2nd part was that this layer rested on supports only, so the fill, whatever its pattern, didn't have enough surface to "grab on" near the perimeters. If I had switched from Zig Zag to Lines, the air gap would've diminished a bit, but I would've gotten drooping. I solved it with wider, underlying perimeters.

The zig-zag pattern are known for this kind of fluke...

I will use Cura to demonstrate, but it's gonna happen on the majority of slicers.

See this example:

Because nothing is really a circle on a cartesian plane and there's resolution limitations on the real world, the slicer has to account for these and, assuming you are using zig-zag to save time, they are doing what is expected. The Zig-zag pattern is a continuous, fast way to fill the top/bottom layers.

Now, see this lines pattern top layer:

It has much smaller air gaps. Every time the nozzle finishes a line, it has the chance to reposition itself to make a much smaller gap, just because isn't continuous.

So yeah, the air-gaps are a "feature" for zig-zag patterns, but you can mitigate this effect reducing the line width on top/botton layers.

It seems that increasing "Skin Overlap Percentage" on cura mitigates this effect too, but i really haven't seen the effects of this setting on a real life object

• Thanks. The zigzag vs line patterns was only a part of the problem. The 2nd part was that this layer rested on supports only, so the fill, whatever its pattern, didn't have enough surface to "grab on" near the perimeters. If I had switched from zigzag to lines, the air gap would've diminished a bit, but I would've gotten drooping. I solved it with wider, underlying perimeters. I'll keep the line fill in mind as an option. Thanks. Jun 22 '21 at 9:55
• @MrSparkly please post that as an answer! You can even accept it after 48 hours!
– 0scar
Jul 22 '21 at 5:22