Uneven top layer

Taz 6, standard head .5 nozzle, E3D V6 hotend, matter hackers petg, 255 temp based on temp tower, .25 later height, e steps calibrated at temp. Using a slightly modified version of the standard petg profile.

I’ve been playing with settings trying to dial in this top layer and I’m at the point I’m missing something and need ideas of where to look. Both plates in the pictures were printed at the same time yet the “off” plate has gaps by the walls that aren’t in the other at both surfaces. I am using ironing after some experiments as it presented the best finish but changes in it’s settings in cura don’t make big differences. The problem I’m having now on several different test runs is what looks like an inner wall either missing causing a gap or inner layer not running up to the wall. In cura layer view there are no gaps anywhere near the areas they show up. I’ve tried 2 and 3 walls with no difference, changed infill, fill gaps, top line width, font styles, and about 10 other things I’m forgetting. What gets me is the letters can cause a difference but why the gap on the base plate during the same print? It looks and measures like it’s after the first wall in the top layer but before the inner layer perimeter line, so between outer perimeter line 1 and 3.

Then on the “o” the inner wall in the center is a layer short of the top and clearly visible. Again in cura it looks great and even. Is it possible this is some bug like ironing and infill pattern is and I just have a magic combo activated?

Thanks for any thoughts or directions to look.

One more pic

After slicing, you can go into the “Layer View” (upper-right corner of the build-plate window). You can choose a “Color Scheme” and I find setting that to “Line Type” is often the most useful.

Below that you’ll see sliders that let you set the layer you want to inspect. The vertical slider has two controls … you can down from the top or up from the bottom (this means you can effectively inspect just a single layer at a time if you want). Usually I pull the top slider all the way to the bottom … click my curser into the box that shows the current layer number and then use the up-arrow on the keyboard to tap up one layer at a time.

From time to time I discover geometry problems with slicer settings (e.g. setting top-bottom layer pattern to ‘zig zag’ instead of ‘lines’ for example will occasionally yield wonky results.

But this lets you determine if the code generated by the slicer is responsible … vs. something else.

“Something else” could be a lot of things … for example was the nozzle getting clogged and not flowing properly?? It’s hard to pin down to just one thing that causes this.

I’ve seen excessive retractions gnaw a chunk out of the side of the filament and results in a hard time extruding. In the “material” properties I usually limit the “Maximum retraction count” to maybe 10 … sometimes less depending on the material. (This isn’t the max retractions for the part … it’s the max retractions it is allowed to do over the same section of filament. There’s another property called “Minimum extrusion distance window”. Suppose that’s set to 3mm (I’m making that up) it means it can only do 10 retractions within that 3mm… once it advances at least 3mm of fresh filament it can do up to another 10. These two settings work together to keep the slicer from chewing up filament.

What material type are you using and what is your printing temp and speed?

Thanks for the thoughts on this. One of the interesting ideas you put out there about the filament getting chewed up and then under extruding is making me question a random problem I was having with some pla prints that would occasionally fail when I was printing a little too cold. However with this petg I have yet to find anything more then the standard teeth marks when I pull filament out.

I was playing with settings and going back and forth with the layer view and line type trying to find any “odd” spots in the areas where there were issues and everything looked great in them except for maybe infil overlap where on the skin layer there was none.

I did another test print but eliminated the “skin wall”, changed ironing to go closer to the edge, and put 5% overlap on skin. That print didnt have gaps in the base plate of “off” or the outer ring of the “O” but the inner wall of the center of the “O” still printed like it was a half layer low which is better then looking a whole layer low. However, the layer preview in Cura looked great. The other letters look great… its like the issue now is specific to an object having an inner and outer wall.
Interesting note is that specific feature and its 3 inner walls are the starting point after a 2 inch travel on every layer, but the lines should come out thin not short if there is a pressure drop right and be built back up by the final lap around the inner “o”?

Next test is same settings but no ironing and see what happens. Open to any random thoughts others have.

Clearly there is something I am missing with ironing. With all settings the same and ironing off, the “O” has no gaps or uneven layers like before…but now all 3 letters have a slight line between the infill and walls but only on the side that was to the back of the printer, the front directions all overlap great. This makes it seem like travel backlash or e-steps are off but that wouldnt explain heights being right once I turned ironing off

Finally a bit of closure on this issue. I played over and over with fill, wall, and ironing settings but in the end the settings that made the biggest difference and made my test prints in a range I was happy with were line width and print speed.
I ended up going to a .55 line width with my .5 nozzle instead of the default. 5 and this made an amazing difference in surface finish. I did calibrate line width at both .5 and. 55 and adjust flow rate accordingly to get almost perfect 1.0 and 1.1 walls. I think with. 5 line equaling the nozzle there just is no error room in extrusion.
The other key change that showed up instantly was matching inner and outer wall speeds at 25 and then slowing skin speed to 10. Anything faster then that and quality issues show up.

1 Like