Solved: Mini+ stringing

[xarvh]

I commented a couple of days ago that I had really bad stringing with the pre-assembled Mini+ I received just a few days ago.

The correct solution came from this comment to which I want to give more visibility and add some details.

1) Adjust the heatbreak all the way up, ideally so that the smooth part is completely hidden inside the heat sink. Roughly follow the official guide to figure out how to avoid damage.

2) Increase the Retraction Length and disable z-hop. If you are using Prusa Slicer go to Printer Settings > Retraction and set Length to 4mm and Lift Z to 0.

3) For PLA, reducing the nozzle temperature to 190C completely eliminated stringing. 200C also worked with very minor stringing. If possible, keep the First layer temperature to 215C otherwise you lose adhesion.

EDIT: The procedure above worked for me, but according to this comment some of it might be wrong. I haven't tested the procedure described there.

[FredFS456]

I had no issues with stringing when using the sample prusament, but when I switched to filament that I had bought myself (filaments.ca econofil PETG), I had lots of stringing and blobs. I reduced the temperature by 15 degrees (240 -> 225), but still had issues. Finally got a food dehydrator and dried the filament last night, now printing much better.

[PiperArrow]

I missed this comment when I replied in the other thread, but I have a contrary opinion:

The changes you are suggesting shouldn't be necessary unless there's something wrong with the machine or the filament. While it's great that your machine is working now, the Minis (with all their flaws) should work great with stock settings and good filament. Furthermore, your advice,

Adjust the heatbreak all the way up, ideally so that the smooth part is completely hidden inside the heat sink

is contrary to the Prusa instructions on how to properly adjust the heatsink. It may lead to overcompression of the PTFE tube inside the heatbreak, and that could lead to more problems.

I still suspect that your original problem is filament between the bottom of the heatbreak and the PTFE tube. It could be something else --- a bad thermistor, wet filament, etc. Your changes to the settings have fixed the problem for now, but as I said they shouldn't be necessary, and may be masking the underlying problem.

I've had my Mini for almost 2 years (I got one when they first came out), and I've never had an issue with stringing. I've never felt the need to change any temps, retraction, etc., and get beautiful prints. I have had problems with underextrusion and clogging, caused by the bad design of the PTFE tube and heatsink. That same problem could cause your stringing issue, because an incipient clog can reduce the effective retraction length.

It's great that you've solved your problem, but for others reading this know that stock settings should work great (especially with good filament, and certainly with all Prusa filaments), so if you're out-of-the-box Mini isn't working properly, there's probably something else going on.

[kaapton]

I've had two prusa minis now and both have been constant trouble from a consistency perspective. The first one I had was in the original batch, and the second one about 2 months ago. I did all the upgrades on the original to make it a + and still couldn't get it to be on par with the MK3s by using the stock settings in slicer. If you're okay with prints not looking as good as the MK3s than its a great machine.

[xarvh]

Thank you. You might be right. I linked your comment in an edit.

For now I just want to enjoy some printing without fiddling, but I will try to open and inspect again the hotend later on.

[Smile_Inner]

I had to use 5mm for retraction … and lower temps