Corner Glob

Hey,
I recently setup my Taz5 and am trying to get it really dialed in. I have noticed that there is a small glob where the extruder turns around when it reaches the perimeter. It seems to leave a little more plastic there than necessary. I was wondering if anyone knew of a setting to change or some way of reducing this. I am using MatterControl, Hatchbox PLA, and a .5mm nozzle. I have tried printing at several different extruder temps and have not seen any different results so I dont think it is a temperature problem. I have attached a picture to help describe the problem.

It’s really a mechanical issue with the way printers work. Your nozzle is effectivly stationary while it is making the turn about twice as long as it is when moving through a point. Some slicers try to compensate for that motion, but most of them don’t do it well.

If it’s not over extruding, then it’s the unavoidable problem due to nozzle pressure. For the turn around, the nozzle has to decelerate, stop, and accelerate again. The pressure inside the nozzle is a little bit behind this actions, there is a delay. It’s like it’s still extruding during the short stop.
You can minimize the effect by printing realy slow, turn down the acceleration values or increase the jerk value. But all those things have side effects of course.
A real fix can only be done inside the firmware, with some kind of an advanced pressure regulation calculation. At the moment, this is not done in Marlin.

Sometimes it helps to rotate the part a little so both x and y axes move on both sides of the corner. That prevents a full stop of one axis and can lessen corner artifacts.

Edit…
That’s good advice if you are having problems at a corner…

You might be over extruding a little in this case.

Thanks for the help and the responses,
I dont think I am over extruding as I am currently running a lot of test prints running a 200x200mm square and looking for bubbling, fill, etc. I have figured out the bubbling is due to nozzle height off the bed, but that would cause issues at the corners where I have measured the bed to be lower than in the middle. I am currently experimenting with temperatures to see if I can “squish” the filament into those pockets a little better. Any tips to know if I am over extruding?