Offbrand filament not extruding - Mini 2

I have three Mini 1 printers as part of a university makerspace. Recently one of our print heads broke and we had to purchase a replacement head. We chose to get a SL toolhead and adapter for a Mini 2 because there are no Mini 1 print heads available anymore and we wanted to try the finer line quality of the SL. However, with the change from a Mini 1 to Mini 2, apparently Lulzbot introduced a " filament guide path", which, according to my call with the lovely tech support people at Lulzbot has an inner diameter of almost exactly 3mm. This means that if your filament is slightly lower quality and has more variation in the diameter, it’s incredibly likely to get stuck in the guide path. We have barely gotten anything to print out because of this and have already had to disassemble the toolhead once after only a week. I was wondering if anyone else had experience with this and had solutions to it that aren’t just throwing away all of our offbrand filament and purchasing new Lulzbot approved filament.


The e3d Titan Aero hot end does have a filament opening of ~3.2mm.
The filament guide is roughtly the same, maybe a little less.

It is recommended that filaments not be over 3.05mm in diameter as this can definitely cause some feeding issues.

Note that the smaller diameter nozzles do make the SL tool head much more prone to clogging due to possible foreign objects in the filament.

As you have taken the tool head apart, when reassembling, be sure that the square heatsink fan is installed correctly with the label facing inwards. If that fan gets reversed, it is almost a guarantee that you will get heat creep and it will clog or jam.

The SL printhead with a nozzle diameter of .25mm extrudes merely 1/4 of the filament volume compared to a standard .5mm nozzle. You have to feed it very slowly. I modified my start g-code to prime the nozzle at 1/4 of the feed-rate.

The SL printhead is great for tiny parts … especially tiny parts with high-detail needs. It can take an eternity to print larger parts.

The filament guide-path constrains the filament and makes it possible to print with flexible filaments (typically TPU) such as those made by NinjaTek or Polymaker. It’s a nice feature and an advantage for direct-drive printers.

As previously noted, the tiny nozzle is also easier to jam … it doesn’t take much to block that tiny opening.

The toolhead has definitely been put back together properly, and we haven’t had any issues with the nozzle itself clogging (although I definitely believe you that it’s more likely with the SL nozzle than with the SE). The issue we had was that the filament literally got stuck in the filament guide tube. Thanks for the advice, I’ll keep an eye on the fan in the future, especially if we have to take it apart again.

Feeding it more slowly is a great tip! What speed did you find worked best for you?
Also, we are only using PLA filament (because students who use our makerspace are often very inexperienced we’ve found it’s best to standardize and not allow more interesting filaments). Because we’re only using PLA, is it possible to remove the guide path, or would you advise against that in your experience?

I decreased the feed rate used when priming from F75 to F20 (20mm/min instead of 75mm/min) … roughly 1/4 the speed (fractionally faster) and the extruder is no longer fighting and clicking.