Adventures with PETG

I knew that I was eventually going to try out PETG filament and it only took me a couple of weeks to decide to order some from MatterHackers. I picked black just because it seemed like the right color to pick and I wouldn't mix it up with any of my other filaments.

First rule of PETG is it is hygroscopic - You MUST keep it in a sealed bag when you're not printing with it to keep moisture out.

Switching filaments to PETG is easy since PETG likes a warmer nozzle temperature - just switch and you're good to go. Switch back to PLA is a little different. You need to warm up the nozzle to PETG temperature (240 should be good) and then feed your PLA in. Cool it back down after you get a good flow of the PLA through the nozzle. I shouldn't have to say this but make sure you use a distinctive color change so you KNOW when all of the PETG is pushed out. White works perfectly after using the black PETG.

My first experiments came about the middle of January and I had been doing a lot of research on how to do it right. Bed adhesion was an issue to address because I was not going to print directly on the bed - a potential disaster because PETG has a reputation for BONDING with various build surfaces. Time for painter's tape. I bought some inexpensive blue stuff and covered the bed with it.

Before the PETG I printed a test figure (MatterHacker's Astronaut Phil-A-Ment at 50%) in white PLA. I switched over the PETG filament (and re-sliced the model for PETG), laid down the tape, and printed at 235/55 temperatures. All went well and I thought I was home free.

Alas it was not to be. I printed off a snap strength test piece and was rewarded with massive curl. The blue tape would NOT stay stuck to the bed when it was heated. Phil-A-Ment didn't have this problem since only his feet were on the bed which was a much smaller area and length.

I tried lowering the bed temperature to 40 but that didn't really help. I tried no bed heat and glue stick and that kind of worked but still got curl. I decided that the tape just wasn't going to stick and decided to look for a better tape.

I found GREEN painter's tape that is made for sticking on concrete and block and decided to give that a try. What an odd smell it has! Not too obnoxious and I figure it won't really be a problem to use. This stuff really sticks good - even when heated to 50C for the fist layer and off for the rest. I used the glue stick too and had no adhesion problems. This stuff REALLY sticks good and you can expect to remove the tape where the part lies to recover your part. Not really a bad thing though.

Although I've solved the secrets of printing PETG I think I'll be reserving it's use to those parts that really need it.

See 'More Adventures with PETG' below for the continuing saga.