Editing a G-code file for different material

Question

I had a model I had originally printed in PLA, and then lost the STL... but I still have the G-code. Now I want to print it in PET-G. Do I need to do anything other than update the numbers on the M104 and M90 instructions near the top of the file to set for new hot end and bed temperatures to get it to print properly?

I know some materials I might also need to adjust speeds, but it seems like with PLA<=>PET-G those two items ought to be enough. Is there anything else I should check?

Answer 1

Tired of waiting, the print is now 40% done and seems to be just fine.

Thinking through my own problem more, there are three other things I might want to check (other than base speeds, as mentioned in the question) if I do this in the future:

1. Cooling. Some materials need the cooling fan set differently. This should also be a single line edit near the top of the file.
2. Retraction. Some materials need different retraction settings to control stringing, and in fact I do find I often need retraction to be a little more aggressive for PET-G vs PLA, even if this one print came out okay. This change is needed for every retraction instruction, instead of just once at the top of the file, but I could probably adjust it via a simple find/replace in the file.
3. Travel Speed. Some materials need faster travel moves, also for stringing. This manages a trade-off between speed and quality. One could just always set for the fastest travel speed, which both improves print times and stringing, but faster travel moves sometimes result in ringing/ghosting at the corners, and so there's a balance that can be different per material type. This might be adjustable with a find/replace, but I would want to read through the file some to be sure we don't use similar gcode/speed numbers for anything else. It may also be possible to use strong accelleration/jerk controls to compensate for consistently faster travel moves, in which case I could set my slicer to use fast speeds that still always work, regardless of material.