TomHeij

Hi @tisimst, this bulging on corners versus ringing is an annoying issue that we are often dealing with as well. The major issue is that the extrusion is not starting and stopping in the same timescale as the motion does. This basically means that, even with a direct drive extruder, your flow will not slow down enough in comparison to the movement of the printhead. This leads to blobs on corners: material is still coming out on roughly the same flowrate, while the printhead almost ('jerk' = 8mm/s) stops. I'm writing 'jerk' as marlin jerk is not the derivative of the acceleration. This problem can be overcome by setting the 'jerk' closer to your print speed, this way your extrusion and motion stay synchronized -> both will stay constant. The problem then is that you are taking corners at a constant (printing) speed, this leads to ringing even at moderate speeds (25mm/s+). So if you want no bulges and no ringing, productivity will take a significant hit. An other setting that reduces bulging is reducing the layer height (less room for material to creep out in the corners), but again this is a productivity hit. A third thing that does not necessarily hurt productivity is to print the outer walls first: this way the bulges formed on the inner walls do not propagate to the outer wall. This will reduce bulging but bulging on the outer wall still happens. Ideally you would want to use a control feature that synchronizes flowrate with your motion movement, this is unfortunately not possible with Cura. I think newer Marlin versions do support these kind of control features. I always chose which hit I take: If I want dimensional accuracy I will print with a high jerk and have ringing (ringing does not lead to large dimensional errors). If I want a nice looking print I will find a balance between bulging and productivity loss.