Hi ! Just a short post about the print quality.
When there are sharp angles you have vibrations that are generated given the weight of the moving parts, the quality of the chassis as a whole and other components (motor, belt, stepper drivers, firmware...). If you try to print too "fast" you have such vibrations artefacts that propagates to the surface of your printed object. It is less obvious on organic parts but on flat surfaces followed by sharp angles, you will see such surface defects.
Follows a photo of the Makerbot Replicator clone out of the box printing at 40mm/s you can see that vibrations are very long.
Find the maximum print speed without any such issue.
You need to download the following part: https://www.thingiverse.com/thing:277394
This is a nice small benchmark able to show such vibration issues. Also you can use it to tune your settings for the linear advance for the extrusion.
It is relatively straightforward, when you pickup the part:
Example at 50mm/s, there are 2 big waves on the Y axis.
Example at 40mm/s, there is a big wave on the Y axis.
Example at 30mm/s, there is no big wave but very tiny ones on the same Y axis (very difficult to see already).
Example at 20mm/s, there is not any wave, not even a tiny one.
For my old Makerbot Replicator clone, the highest speed for the best print quality is between 20mm/s and 30mm/s with PETG at 240C. You will say it is quiet slow, I would say it is not bad. My old printer has been already modified with a bowden to reduce slightly this issue. I removed both stepper motors of extruders from the gantry (more than 500g) and I do not use any spring tensioner on belts (they can oscillate too).
As said previously, this test is also able to show you some extrusion artefacts.
From 30mm/s, there is an issue on the Linear Advanced parameter on my printer that needs to be tuned for this filament, follows a close up of the issues.
Circle in Yellow seems to be retractions but I do not have any retraction in those places, this is due to the too fast slow down while there is still some pressure in the hotend, so we over extrude when arriving to the corner.
Similarly, in the Circle in Yellow the sharp 90 degrees corner are not clean enough and there are a bit too round, so we over extrude also. PETG filament is more elastic than PLA so it needs different tuning parameters for the Linear Advance at the firmware level.
Happy printing !
