As shown in the pictures, the print appears to be pristine all the way up until the last few layers where they get really wavy and the tool head starts to tear a bit at the print. I’ve watched closely and the print is literally perfect for 63/64 layers. As soon as the top surface line starts, it goes awry.
All tests I’ve done have been in basic PETG that I’ve calibrated for K value as well as flow and max flow. I’ve also sliced the same profiles in both BS and Orca with identical results.
I tried cutting the file to just the top few layers so I could troubleshoot and interestingly enough, the print surface came out great. It only seems to happen when its the full 8+ hour print file and only once it gets to the top.
This issue only really seems to be occurring on the left and right side of the bed, the middle doesn’t suffer the same. I’ve checked my bed and its not warped (straight as an arrow), and I’ve manually levelled it as well.
I’ve tried by slowing print speeds way down (sub 100), turning off cooling, and improved the z offset by 0.05.
Please let me know what details I’ve left out, but would appreciate any genius troubleshooting tips/queries!!!
My guess is that the top layers get thicker they are shrinking and pulling the part edges up. Can you visually see either the part pull away from the bed or the bed pulling away from the magnetic surface?
That was definitely not the case in my instance. There was no warping off the plate (Biqu Frostbite plate) and I had identical warping on two separate prints. Printing on a different P1 and it came out perfect so not a model issue either.
I retensioned my belts and that helped dramatically, but one spot still shows waves. Also theres a rattling sound now after auto-tensioning so I’m troubleshooting that.
Spherical infills tend to warp a bit in the rounded areas, causing the weird noise when the solid layer is added.
Infill shining through the top layer is often the result of several factors coming together.
In the above pics the infill density is so high that no bridging is considered by the slicer.
Great for being strong but usually requiring additional top layers, which can be a problem if the filament than starts to build up in the wrong places while failing fill those voids.
Adhesion adds another nightmare and the frustration is complete.
Reducing the speed for the solid layers by quite a bit can help.
Far better though is using a more suitable infill pattern and/or spacing.
By adjusting the bridging and (sparse) infill setting you can basically force a bridging layer between sparse and solid to infill.
This allow you to tweak the bridging to result in the smoothest possible outcome.
Either by making the bridging dense enough to flatten most of the sparse infill out or even by making it more spiderweb like in order to provide a rather flexible base that gives the first solid layer enough room to squeeze through where needed while having enough support to not sag.
If in doubt always check first how a reduction or increase of speed affects things.
Often a slower approach fixes more things than you think
PETG wants to be a bit underextruded for better looking print.
I can’t see the full reflection of the top surface, but I feel that in the middle it’s shinier than wavier outter edge. That shows kind of heat gradient there.
PETG sticks to itself better when it’s hotter or print speed slower.
I assume you already calibrate flow ratio for this PETG. Try to reduce the flow a bit more and see what happen. Say go down to 0.88 or 0.86 instead of default 0.95
I am printing nonamed PETG now, with flow ratio 0.90 and still seeing a bit of over extruded
I use two, sometimes three different calibrations - depending on my needs.
The first is obvious, a proper flow calibration for vase mode prints.
Here I want the wall width to exactly match what I set it to as this give me the best results.
Second is my general calibration.
Here I adjust the flow rate to give the best average results.
Depending on the filament this might mean having to accept a bit of over extrusion in tight corners of top surfaces or on the other end some tiny gaps between the lines of the top surface.
But it also means I have no artefacts on the prints, no adhesion problems and no failed prints because of extrusion related issues.
Last is my high quality profile.
Here everything has to be a perfect match.
Print settings, print speeds, acceleration, flow ratio, max flow rate (to limit speeds if need be),…
The goal here is to end with top surfaces good enough to not require bogus like ironing.
No gaps between the line, no ridges where the lines meet, no saw teeth along the outer wall.
For matte PLA this results in prints with basically invisible layer lines and a print quality that requires little to no addition work before being painted.
Why all this hassle?
I use a E3D hotend and it has no issues maxing out the printer.
My default speed for basic PLA or PETG prints is around 400 to 450mm/s with max flow rates between 35 and 45…
With a max flow rate set to 40 and otherwise sticking to the default 0.2mm profile it prints a Benchy in good quality in just under 30min - without all the cheating in the G-code file for the 16min Bambu record LOL
In still acceptable quality I do it in about 25min but then the chimney looks a bit melted unless I change some of the default values…
