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I got the same Bomber Jacket Brown and Glow in my grab bag. The glow does glow…but needs to be very well charged with a bright light or UV light first.

I originally printed my MPCNC in PLA – but one of the rolls I used was some really bad esun that turned out to be horribly brittle and parts were cracking in half just sitting on my desk untouched.

Plus I live in the desert and will be keeping my MPCNC in a detached office that doesn’t have A/C running most of the time. So I worried about PLA deforming and reprinted everything in PETG.

I started with a roll of “B Grade” PETG from Atomic which was the first PETG I had. I had a horrible time printing with it at first, but once I leaned how to do single wall calibration prints to really dial in my extrusion multiplier (explained well in this blog: my results got much better. My first PETG prints were stringy messes with little dingleberries all over them. The strings and berries were easy to remove…but annoying. Once I dialed back my extrusion I was able to lower my temp a bit and things got much better. This was with the stock extruder/hotend on my FolgerTech 2020 i3 which is very similar to the hotend/extruder vicious1 sells. The next big improvement for me was swapping to a metal extruder for $15 on ebay that had an adjustable tensioner – once I turned the tension up my print quality got MUCH better with all materials and my PETG prints were coming out as good or better than my PLA and ABS prints. But I’d still occasionally get little zits or gaps in layers.

I messed around with retraction settings a lot trying to solve that, and upgraded to a e3d V6 all metal hot end so I could run higher temps (I’ve gotten a few grab bags from MG and their PLA likes higher temps than I’d expected and eventually damaged the PTFE liner in my hot end.) I found that shorter retractions but at higher speed solved some of my PETG issues. The final key was enabling “Avoid Crossing Perimeters” in slic3r which got rid of the last of the minor defects I was seeing with PETG where it would build up on the nozzle then eventually all the junk on the nozzle would come loose and sometimes cause the printer to have major issues. With avoid crossing perimeters that problem went away entirely and I no longer get any PETG building up on the nozzle with all other settings the same.

It took a long time but I now get GREAT PETG prints with both Atomics PETG and MakerGeeks PETG. Attached is a photo of an extruder I printed with the first roll of Atomic I started with. And some MPCNC parts in MK PETG (turquoise) and Atomic PETG (Gunmetal Grey and Navy Blue)

My advice is to do a lot of small calibration prints with PETG to get everything dialed in perfectly. I obsessed over doing the negative space test from Make Magazine’s set of evaluation prints and can now print it in any material and remove all of the pegs. But I have piles of little single wall test prints ( I use this with a 0.4mm nozzle: Oh yeah, I also no longer let slic3r set the extrusion width automatically, I set it explicitly to 0.48mm (120% of 0.4mm) – that helped a LOT with getting consistent single wall prints. That, higher tension on my extruder, and then adjusting my extrusion multiplier based on test prints from each roll of filament got me finally fully dialed in.