So I’m running into an issue with my prints. Hoping someone can point me in the right direction as I have tried for days to figure this out.
Printer is a P1s bambu printer (I have two of them)
Ams-ht and a Sunlu dryer.
Designed and saved as an stl in solid works
Using Bambu slicer.
The defect happens at different severity based on material bit is always there. The image is abs but it will do it with abs-gf / petg-cf and pla also. ABS is the worst but of course that’s what I need to print them with.
I have modeled the holes with and without different size fillets. I also tried tier drops instead of round holes.
I have dialed in the abs to also perfect kpressure and flow rate. I used a microscope to pick the perfect k pressure.
I have moved the seams to different locations
With or without supports.
With and without chamber heater on.
Outside of this issue the prints are some of the best looking I have ever done.
As mentioned above I have two p1s printers. Both have bambu hardened gears and run hardened nozzles. One at .4 and the other at .6. The .4 is way worse than the .6 but you can still see it on the .6
You have problem with retraction mostly. Like, after retraction it primes the pressure before new loop, but somehow fail to prime the pressure or doesn’t prime correctly. For a few mm there, it wasn’t enough pressure to push filament out. It is particularly worse at seam at well.
This could be anything: retract speed was too fast, too much resistance due to worn PTFE tube and it messed up retraction…
@simon14 I appreciate you taking the time to respond. I had someone else say something similar in a FB group. I can rule out the bowden tubes because I just replaced them all and the problem was there before and after the replacement.
I am running one of those string tests now so we will see if that give me anything to work with.
So one thing I have never really done was change the slicing parameters. I switched it to a slower speed higher quality preset and the defect does almost go away. I attached some test cubes I did.
A note on the PTFE replacement.
Was the PTFE tubing BL tubing or the correct spec? BL notes that…
The PTFE tubes we recommend have an internal diameter of 2.5 mm and an external diameter of 4mm. It is not recommended to use PTFE tubes with a different size, as this can cause additional problems when loading and unloading due to increased friction (for lower ID PTFE tubes) or feeding problems (when larger ID PTFE tubes are used).
Retraction problems if there are, only or usually at seams.
If those defects are not at seams. Then it could be moisture. As water comes down to the nozzle and suddenly expands by overwhelming heat and explodes. These mini explosions create back pressure and disrupt the flow, hence those voids
For some extreme cases, drying filament in an oven could take days to completely eliminate moisture
So I did alot of tests and research.
To get rid of the little blemishes was changes to retraction ssettings. I changed to length 5mm and 40mm speed. That cleared the blemishes up.
The problem of the defect around the the hole was still an issue.
The fix for this turned out to be a check box setting under speed - slow down for overhangs.
I started noticing that everwhere that I have this issue is when the printer reduces speed. So I let it go full blast the whole time and its perfect. No more issue.
Something I see that maybe other folks more knowledgeable than me in the subject can talk about but it looks like there is maybe some ringing going on.
You see what look like waves running across surface? Scroll down a little and there is a block about Ringing Troubleshooting
I basically lowered from .8 down. I thought I was pushing the limit based on what the spec sheet was saying but I could totally be wrong as usual. What type of #'s are you running for retraction?
I actually was looking at that. I had come across some videos and models about how to center your belts and make sure your printer is square. I printed the models to do it and ordered the triangles they used in the videos. I also ordered a belt tension gauge that I will use before and during the belt tension calibration. All that for the ringing.
Here is the video
I pretty much use vanilla setting for retraction for most of filament types, i.e 0.8mm for everything except TPU for 0.4mm
Around the hole is ringing, yes. That is understandable when you don’t slow down at corner. But the vertical banding is result of extra tension when each tooth bites into the pulley. We call it VFA instead.
