I had reprinted part of my printhead in white. Whenever I've opened the extrusion idler, I've seen a pile of black dust. I actually had already cleaned it off before it dawned on me that I should take a picture, so here it is, which shows a wideshot and then a closeup with some of the traces still left:
Since the original kit is all black, you might not even notice this black dust against a black background. So, maybe no one is aware of it. As you can see in the last photo, I am now going to try to mitigate against it by using some sparing amounts of white lithium grease. It's not a good solution, but it will have to do until someone comes up with a better fix (like maybe a redesign with washers on either side or perhaps something better still).
I'm pretty sure it's ground black plastic from the idler (from the original kit):
That gear piece has nothing to prevent it from grinding against the sides (nylon washers would maybe help if the part were redesigned to make room for them), and so it grinds off the black plastic. Well, why is that a problem, you ask? There are fans moving air around. All it takes is for those plastic bits to land on the filament, or go in the hole which leads to the hotend. Those are PETG bits of plastic. If you're printing PLA, they won't necessarily melt, possibly leading to... a clog. There, I said it.
As I now have spare nylon washers I felt safe enough in removing the idler from my MK3 for a close look.
As well as the expected brown of rust in the lithium grease small amounts of near black plastic can also be seen matching the colour of the printed part. All though it turns freely when not under load I suspect it grinds lightly when under the tension from the springs.
As a result I have added some tolerancing clearance to the part under the gear.
STL of Extruder Idler W2
Autodesk DWG of Extruder Idler W2
GO TO FULL POST ➙