Top surface bulging near perimeters

I have some quality issues that I hope to resolve. It only happens within about 10mm of a perimeter. The surface seems to bulge up some. In other spots where there is a wide open space, it is messy just by the perimeter and then it is pretty smooth for the rest of the distance. Someone suggested that I slow down. The top/bottom surface is 40mm/s. The infill is 80mm/s. I do not think speed is the problem. Does anyone have any idea as to what to do about this?

Looks like an extrusion problem to me like in some cases the extruder is skipping - maybe tighten it or inconsistent filament width or a poorly wound spool so it gives too much resistance at some points

Hi Nathan,

That’s you nozzle scraping the top layers. How is the adhesion at the first layer? If it pulls up just a bit at the edge, you will change the gap between the extruder and the print. Also, recheck your level and z-offset. Is this happening all around the perimeter or just one side?

I am positive that the part was nicely secured all the way around. It was not under-extruding. The raised areas are around all perimeters regardless of where on the print they may be.

I did realize that I did not have the bed clip supports printed and inserted, so I did that last night. The printer is unusual in that the bed can tilt as part of the bed leveling process. The clips that were supposed to keep the bed leveling consistent sometimes give way a little. I will do more testing another time. I hope my print quality has improved.

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I measured a single walled print and found it to be about 0.5mm thick almost all the way around. The nozzle is supposed to be 0.4mm. I imagine that may have something to do with it.

Maybe do a calibration cube to get a more accurate assessment of line thickness? I wouldn’t depend on one layer.

To be clear, it was a 100mm diameter and 100mm diameter cylinder with a bottom and a single wall thickness. I can try to download a calibration cube too to make sure though.

You can reasonably make a .8 or even 1mm wall with a .4 nozzle by accident or on purpose. On purpose by setting the layer width in a slicer like Prusa Slicer or Slic3R or by accident by getting the extrusion multiplier wrong. I print mostly with a .8 nozzle and have my outside perimeters set to .9 and all the others to somewhere between 1 and 1.8 depending on how the math of the part works out. Make sure though you dont exceed the max volumetric extrusion your hotend/extruder/nozzletemp/filament combo allows or you will get inconsistent extrusion

This is a testprint I do for my .8 nozzles the first wall is .9 the 2nd one 1.25 the 3rd one is 1.5 the 4th one is 2mm and the one tying it all togehter is 3mm It was printed in “Crappy PLA” that came with my last printer (filament thickness varies greatly) the one on the right with the X-acto knife stuck in it was sliced with a .9 wall thickness you can see that walls 1,2 and 3 are just one layer thick wall 4 is 2 layers but as they are .9 wide and Prusa Slicer calculates the outside position you wind up with a .2 gap in between (PS should increase outside layer thickness here but doesn’t as it does on the 3mm wall) on the 3mm wall you can see 2 outside perimeters of .9 and one inside or 1.2. On the left I increased the layer width to 1mm so the first one is 1mm slightly thicker than the one on the right but the others are the same and the 2mm one cannot be separated now I use this pic as an example for the kids to teach them how to consider slicing parameters when making a design and printing it and how to tune in a filament as after one selects a layer width one can fine tune the extrusion multiplier by measuring this test print with a caliper

this is important when one prints gears like this


To get the center distances correct and make a nice snug fit on other parts like the metal shaft in the 2nd pic is 10mm and there goes a 4mm square key way and the other gear takes a 1/2in shaft so the clearance hex hole of the 1/2 in shaft is 13.2mm and the hole for the 10mm shaft is 10.4mm. you can see the top surface is slightly rough as it was printed with a slightly enlarged extrusion multiplyer to have better layer adhesion. This was printed with a .8 nozzle .4 layer height .9 outside layer width 1.3 inside layer width 8 perimeters - so the gears are solid pieces of plastic and as the HIPS that it is printed out of has a specific weight of 1.04 they will sink when placed in water so there is no empty air pocket inside its as close as one can get (i believe) with FDM to molded parts I call it printing solid. Yet the center distance will be accurate to within less than 1/10 of a mm The gears are double helical involute with a modulus of 1.5 mm and addendum of 1.2 a pressure angle of 14.5 deg and a helix angle of 30 deg. The material is HIPS printed on an Anycubic Chiron with 255 nozzle and 105 bed Chiron is all stock with 1 mod namely the PTFE tube was replaced with a capricorn High temp one to better handle the 255 in the V5 clone hotend. The print was governed at 16.5 mm3/sec max Volumetric E.

I adjusted the delta_radius, delta_length and the steps/mm and things are now much better. Things print slightly bigger and the balance between extra material on the outside and on the inside are pretty well balanced now. I decided that I need to increase my skin vs wall overlap since there were some gaps. Things look nice and smooth for a top surface.

I had determined that the single wall cylinder that I was printing had a wall bigger than 0.4mm. When I made my own design file, I still get 0.45mm walls instead of 0.4mm. That is thinner than I was getting before with the single wall cylinder which I determined that I must have simply scaled it up to 100mm tall by 100mm diameter.

That’s why I prefer forums to social networks because the forums are serious.

Post approved / And welcome to the forum.

I reinforced with screws so that my bed does not collapse. Besides, he’s already a bit old.