We have been having trouble with our UM3 and printing TPU. We print a ton of large TPU parts (right up to the top of the build area in some cases) on our UM2+, and almost never have a failure. On the flip side, almost every TPU part we print on the UM3 fails.
What happens is the material gets curled up in the feeder as it is so flexible and causes under extrusion. I have adjusted the material drive tension and nozzle temperatures up and down to no effect thinking that this was the issue. I have used default Cura and printer settings, tweaked Cura and printer settings, used comparable settings to the UM2+ (that is working just fine), and yet the UM3 fails every time.
I have noticed that there is a major difference in how the UM3 prints the infill that I believe is gooping up the nozzle as it is putting down too much material.
You can see this by changing to layer view and changing the settings:
The UM2+ looks like this:
This looks quite good to me - no issues.
And this is what the UM3 looks like:
This looks like a problem waiting to happen:
1. It is printing an internal shell rather than just connecting to the existing shell
2. The next portion weaves back and forth and overlaps itself far too much. It also overlaps the 'infill shell'.
3. There is a third portion that is a 'bridge' to the infill.
4. Finally get to the infill, the part that I am expecting.
Here are our last 5 prints all lined up:
I believe this is why too much material is being put down. With no where to go, the part gets lumpy above the surface of the current layer, the extruder drags the nozzle back and forth through this, and eventually clogs the nozzle, causing the under extrusion that we get every time we print.
I have tried various different infill patterns, but they all have the above features to varying extents.
Any thoughts on what we need to change? We are printing 24/7 with our UM2+, and barely touch our brand new UM3.