Problem with Inconsistent Extrusion
So, I've had my mk3s for a few months now, and have had no issues up until last week. I ended up with a bad roll of PLA, which completely clogged my extruder. I cleaned it out (with a fair bit of effort), and I also changed out the nozzle.
However, now my prints are suffering from inconsistent extrusion. Specifically, I'm getting some fairly extreme stringing (where there was none before), and I've also noticed that I'm having problems with layer adhesion. The stringing isn't a big deal, as I do have a heat gun I can use to blast them if need be, but the layer adhesion is pretty bad. It's to the point that if I print with a brim, the bottom layer peels off when I try to take off the brim.
I've checked the alignment of the extruder gears, and I double-checked to make sure the new nozzle is in tight. I also went back and tried some other PLA that had printed perfectly before, and I'm getting the same problems.
Any suggestions on other things I could try would be very welcome 🙂
RE: Problem with Inconsistent Extrusion
If you've done a lot of mechanical work that might have moved things, recalibrating XYZ is a good idea. Re-calibrating your Live-Z is also recommended (try Jeff Jordan's "Life Adjust" method). As for extrusion:
- Raise Z to max.
- Heat to printing temp.
- Extrude material and observe.
If the filament flows evenly and coils neatly on the bed, your nozzle and hotend are clear. If it leans to one side or comes out irregularly, you may have a partial clog. (Especially if you used the blasted needle to try to clear it.) Try some cold pulls. I recommend cleaning filament. If those don't work, you may have a damaged PTFE tube which will require a bit more of a tear-down. A new nozzle is a quick and easy test.
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RE: Problem with Inconsistent Extrusion
Cool, thanks, I'll give that a try tonight when I get home 🙂
I know that I had to do a fair bit of tugging/prodding with pliers to get the stuck filament out, so I wouldn't be surprised if it's the PTFE. Here's hoping re-calibrating and some cold pulls do the trick though!
RE: Problem with Inconsistent Extrusion
Tried recalibrating and a few cold pulls last night. Didn't seem to have an effect. Maybe tonight I'll try another nozzle, and if it's still the same I'll swap the PTFE. Fingers crossed that it's just the nozzle 😛
RE: Problem with Inconsistent Extrusion
Another place you "might" have unintentionally changed something is the heat break to heat sink interface. When changing nozzles, Prusa recommends you twist the heater block 30 degrees ... this has the ability to loosen the heat break from the heat sink. E3D's procedure doesn't mention doing this. You might want to check that the heat break is firmly threaded into the heat sink. If this is loose the melt transition zone move upwards in the heat break and in theory will affect retraction efficiency.
The up side is if you are changing the PTFE, great time to ensure the heat break is tight to the heat sink.
RE: Problem with Inconsistent Extrusion
Thanks, I'll check that out too 🙂
I did change the nozzle last night, and started printing a benchy before leaving for work. If I'm still seeing the same issues, I'll do the breakdown, replace the PTFE and check the heatbreak.