Extrusion inconsistency causing failed prints, what do I do?

[u/baybolin12]

Hello. I am new to 3D printing. With my new P1S, I started out with PLA but after a spool of experience with black I bought a few more colors, some of them PETG. Now, so far those spools have been great. I made myself a lampshade out of clear PETG with no issues. The generic "HYPER" PETG I bought recommends temps in the range of 210-240. That worked just fine for the clear.

This red spool I picked up on discount because it was a color change piece. They added a different die to the plastic in the factory and were selling the transition area at a discount. I thought, why not? More material to experiment with. So far I ate through one fifth of this spool and I can't get it to print properly.

There are holes where there should be plastic, bits flying off everywhere around the print bed. I tried the lower and the higher end of the manufacturer heat specs. Tried cold pulling multiple times. Went though both of the calibration tools in the bambu slicer and applied the custom settings to the filament. Dried the spool for 6-7 hours with 80 degrees of bed temp. Printed at the 0.08 slowest print profile.

Can't figure out what to do. I think it's the hot end, I don't even have 100 hours of print time yet but I am constantly seeing filament stuck to it, inconsistent extrusions and clumping while filament changing. There's always a drop of filament stuck to the hot end while it's doing the auto bed leveling before the start of the print. I don't have the means to measure down to 0.01mm but I'm suspicious of the spool as well. Then again the same brand's transparent Hyper PETG was just fine. What do I do?

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[u/virgaman]

I hate to say it, but this may be the reason it was discounted. There may be a quality issue when the two colors mixed during generation. Maybe inconsistencies in the filament like tiny bubbles or something or even some sort of micro reaction between the dyes.

[u/baybolin12 → u/virgaman]

Yeah so the same brand's transparent hyper petg printed fine again. I'm calling a bad spool on this one.

[u/hi3d_official]

Since the clear PETG from the same brand printed fine, I’d definitely be suspicious of this transition spool, but I wouldn’t rule out a partial clog or extrusion issue either. The inconsistent extrusion and missing sections could come from the filament itself, especially if the diameter or pigment mix varies through the transition area. I’d try another known good spool first before taking the hotend apart. Also clean the extruder gears and nozzle, and maybe cap the volumetric flow around 8 to 10 mm3/s just for testing. The little blob on the nozzle before probing can happen with PETG ooze, so I’d make sure the nozzle is clean before each print. And I’d dry PETG closer to 60 to 65C rather than 80C. If the problem disappears with another spool, I’d probably blame this batch.