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3D Printing
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TIL that that 200% is not relative to the extrusion width on other layers. I finally read the hovertext and discovered that it is percent of first layer height — so when I tried to make it 100% I made a real mistake. A 0.8mm nozzle doesn’t do a good job of printing a 0.3mm wide by 0.3mm tall line. So I went to 0.4mm thick first layer and 200% first layer extrusion width setting for 0.8mm first layer extrusion width, and it looks much better. Going to 0.6mm for all layers looked better yet.

Next, I tuned linear advance.

Now, the frames I’m printing are structurally sound; they bend well without delaminating. But I’m still getting significant stringing. I tried printing a temperature tower, and the entire range I tested, from 245⁰ to 285⁰, I kept seeing stringing. But that doesn’t test printing at speed, and with the 0.8mm nozzle that’s where a lot of the challenge lies. The tower, which since it was all small moves was only slow movements, looked better around 255⁰, but when I tried to print the visor with the hotend at 255⁰ the plastic didn’t get hot enough to stick to the 75⁰ bed even at 60% of 60mm/s (36mm/s) so that didn’t help.

Other than some stringing, the visors are looking good and printing quickly with the 0.8mm nozzles, and I was having to clean them up anyway before, so I think I’ll stick with the 280⁰ first layer and 290⁰ other layers, with 60mm/s speeds and 0.6mm layer thickness for all layers, and just clean the strings off afterward.

So going from 85mm/s with 0.4mm nozzle to 60mm/s with 0.8mm nozzle, but twice the extrusion width and twice the layer height, works out to a speed win, even though I still have to clean strings off the edges.

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Have you tried drying the filament, I’ve had stuff fresh out of the mfg package with desiccant that strings and then I ran it and my food dehydrator and reprinted and strings went away. But I agree sometimes small wispy strings just happen and cleaning them up with a razor knife and a heat gun at the end is faster than trying to figure out those last few slicer tweaks.

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I have not tried drying it. I probably wrongly assumed OK because fresh out of bag. I did notice some spitting when I was severely underextruding the first layer due to misunderstanding the relative size in prusa-slicer, so I think you are :dart:

My dehydrator is a round tray style that wouldn’t obviously have room for a roll of filament. I should then move faster on my intent to turn the old heated bed from my awful tronxy x5s into a heater in a drying oven and start drying all my PETG in it. Thank you for the suggestion!

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I can’t seem to change only one thing at a time. :frowning:

I switched back to 0.4mm nozzle for printing other parts.

Then I made a drying oven from discarded parts from the tronxy x5s and a sheet of polyisocyanurate insulation, re-sliced at .5mm extrusion width, increased retraction from 1mm to 2mm, and slowed down max speed to 80mm/s and external perimeters to 60%.

After a few hours in the oven, it still weighed in at example the same weight. I had wondered whether it would weigh less after drying; since it didn’t and it was a nearly full roll, I must have removed less than 0.1% by weight of water.

I saw less stringing than I did before on 0.4mm, and I don’t have any layer adhesion problems. Since I changed lots of variables, I don’t know which was most important. But now I can work on changing one variable at once and slowly work my way back up for speed.

Edit: I lied. The first batch were projections that don’t have the “elephant foot compensation” and using spring clips to hold glass to my cast bed isn’t as flat as actual cast bed (I’ll probably be waiting a long time for my new sheet to arrive from China), so I had some “elephant foot” in places that I had to trim (yay deburring tool!) so I switched back to the standard STL with the compensating chamfer. But the only other change I made was external perimeters to 90% speed instead of 60% speed, for the next test.

90% speed had stringing. Went to 3mm of retraction, no change in stringing from 2mm. Back to 2mm of retraction and trying 75% external perimeter speed next.

Next update: That still had strings, so I baked the filament overnight.

My oven is a 3D printer controller, bed, and two thermistors. One thermistor is the bed thermistor, and the other I had in the air. I had to set a bed temperatures of 130⁰ to get a (very stable) air temperature of 65⁰ which was what I saw recommended for PETG. I put the reel on its side on top of a box I set on the bed to avoid direct contact with the bed. I left it overnight. In the morning, I pointed my IR thermometer at the (black) PETG filament and the readings were around 85⁰. :grimacing:

It printed with almost no stringing. A few wisps here and there. But the filament had slightly fused in places, and it broke sometimes while printing, so I only got a few sets. Mostly I printed trash. And the inside of the reel was clearly worse than the outside. I tried to rewind the filament but it kept breaking when it got to what had been the bottom side of the reel when it was in the oven, where it really fused together. I feel bad about destroying over half a kilogram of filament with that mistake.

So now I’m drying another reel, but this time I’m sandwiching a thermistor between the reel and the box it’s sitting on, and will set a bed temperature that keeps the reel temperature around 65⁰. … Drying it overnight immediately after taking it out of the plastic wrapper took 2g of water out of it, and this time I kept it below the glass transition temperature, it seems.

Next update: By the end of the day, it’s starting to string again, so I put it in the oven overnight and on the printer again in the morning. Until I make a dry box to print out of, I could maybe occasionally swap two rolls between being dried and being printed.

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