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blobs on perimeter seams  

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Dinther
(@dinther)
New Member
blobs on perimeter seams

Proud new owner of a MK3S+ and as such, I don't know much about how slicers go about their business. The print is a circular shape with a layer height of 0.2mm and a 0.4mm nozzle using PLA standard Prusa slicer settings. From what I have read so far this is not a new problem but the solutions offered are so varied that I decided that I want to understand the problem better.

I have taken an extreme closeup of a close to vertical print surface. Note that the printer head moved from left to right. When the perimeter layer is drawn, I imagine the head accelerates to a nominal speed and the extruder is expected to match pace. Same when the head decelerates towards the seam. But molten plastic doesn't stop just like that due to back pressure. So yes, I learned about the retract settings which relieve the back pressure but I suspect retraction only kicks in when the head is moved such as a layer change.

The picture shows a sudden apparent increase in plastic extrusion just as the head comes to the seam. I am pretty sure the extruder is not made to pump more plastic but the deceleration of the head would have the effect of excess plastic because of the back pressure effect.

Rather then blindly change parameters and maybe make it go away, I would like to learn about the underlying reasons and dynamics that cause all these parameters to exist in the first place. All this to better understand the tool I am working with.

I would love to hear the input from the experts, links to more information or possibly a solution and why it works.

This topic was modified 3 years ago by Dinther
Posted : 18/02/2021 6:03 pm
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