I ordered a spool of PETG to begin experimenting with on my 3D Printer. A few of the benefits of using this material vs. PLA are the better temperature resistance and strength properties. ABS works as well, but PETG is less brittle than ABS. This mix of properties is great for building some mechanical prototypes. I was excited to get started!
My first problem:
I began a small test print and had to dial in the bed level for PETG to even begin sticking. This was the first challenge, but nothing I hadn’t done before. I set up a 4 hour print using the recommended Cura settings for PETG and after hour 2 a huge problem occured. Blobs!!!
Walking away even though the first layer went down well was a mistake. The PETG built up around the nozzle and encapsulated the thermocouple. After some surgery, I got the thermocouple loose, but the wires had separated. I’d have to wait a week for a new one to install.
Cura Settings:
I did some research after experiencing a thumping noise when extruding. This was a problem with my layer height and the speed I was trying to print at. I corrected this issue by lowering the print speeds and making the layer height smaller. These two changes got rid of the noise and the under extrusion issues I was having.
I also was getting a large number of blobs appearing on my prints. I had previously raised the retraction distance to get rid of stringing, but someone had recommended reducing this distance and just increase the speed. This proved to be the right combination and I was able to reduce the blobs and limit the stringing.
Mechanical Issues:
Something was not right with the leveling. Despite my efforts, the prints were uneven and the nozzle/fan was scraping the PETG if there was a small zit or string stuck somewhere. This caused my x-axis to jump time. A print that jumps turns out like the picture shown. The layers all became offset.
I noticed my bed screws were maxing out on the right side to get the bed level. I eyeballed the z-axis and it seemed to have a tilt. After some research. I found a tutorial for leveling the z-axis. It involved manually running the ball screws up to the top. This is where I found the right and left side slightly off. Running them all the way up, I was able to get them aligned again. I also centered the y-axis rail at that time. A good procedure for this can be found here Carriage Adjustment Procedure
One more mechanical issue I had was the spool having trouble feeding the filament through the extruder. Underextrusion resulted again. The extrusion end was not getting enough filament to print. It was weird this only occurred after the first few layers though. I believe part of this was due to the speed I was printing at. The other part of this was my spool having a different inner diameter than the Hatchbox brand I normally used. This dropped the spool and it was rubbing on the frame providing more resistance to turning. I used a piece of PLA I had laying around to raise the holder up and it functioned much better. This is shown below.
