When printing circular objects or those that have circular corners, I have noticed that there is a large amount of stuttering as the printer moves around the circle.
Let’s take this example of travel moves between printing 3 different supports with “avoid crossing perimeters” turned on:
As you can see, the A1 clearly stutters when travelling around the circle. If we look at the print preview, you can see that these travel moves are made up of a load of short line segments (G1 moves) that have a relatively small angle between them.
This same stuttering effect occurs when using several consecutive arc moves (G2 and G3) or linear moves (G1) to extrude a circle, such as in this second example:
Now for a normal printer that uses junction deviation (JD) in Marlin, or square corner velocity (SCV) in Klipper, the printer would smoothly glide round these slightly angled straight lines without changing speed much. However for the A1, it seems that what it is doing is rapidly decelerating and then accelerating again at the junction of each small line segment, which causes a lot of rapid stuttering and noise as well as making the printer much slower than it needs to be.
This leads me to believe that the printer is using classic/simple jerk, which is where the printer doesn’t take into account the shallow angle of the following linear move, and instead decelerates to the jerk speed and then accelerates again at the junction of every single linear move. It seems odd that a printer released in late 2023 would be using such an outdated technique when other modern printers have already moved to JD or SCV.
Is this true, and if so is there a way to switch to something similar to junction deviation or square corner velocity in the firmware?