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.

What is the point of this post ?

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.

Slicer settings:

• Disable fully the cooling parameters: set minimum print layer time to 0, you can keep fan at full speed if you are doing PLA.
• 2 Perimeters/Insets, 10% Infill, 0.2mm layer height (or lower if you have a tiny nozzle).
• Set the temperature of your filament at least at the temperature you are used too, or you can increase it a bit it will magnify the ghosting issue.
• The part orientation is correct in the STL, no need to change it.
• Create a file for each print speed you want to try, on my old printer : 20mm/s to 50mm/s by 10mm/s increment.

Interpreting Results

It is relatively straightforward, when you pickup the part:

• You will check on the surface the amount of vibrations you have on the surface of each face. I like to use the light mode on my smartphone, you put it at an angle and you use the nails of your fingers to feel the surface.
• For the extrusion part, you can check also if the sharp corners are not too round. Also, check if there is no over extrusion before taking the small round corner.
• Inspect the letters, it will give you an hint of how fast you can go if you have such difficult overhangs.

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.

How to improve this ?

• Slicer: reduce the speed of the most external perimeter. Reduce the speed of top and bottom. Printing time will be bit longer.
• Firmware: reduce the acceleration a bit, change the jerk setting. Do not reduce too much otherwise you can have over extrusion issues especially on sharp corners. Setup the linear advance feature if the firmware have it, it will help over extrusion when reaching sharp angles and also under extrusion when leaving such corners.
• Hardware: lighter and/or stiffer motion components.

Happy printing !