Minimal Magnetic Filament Wiper

Once you start wiping your filament as it is drawn in by the extruder you'll be surprised how much dirt it collects from the ‘fresh & clean’ spool. While I already had a holder to wipe and guide the filament on the way from the ender's top spool to the extruder there was nothing in place for filament served by a standalone spool holder. It would need to hold on to the filament and stay put in front of the extruder.

I designed this for flexible filament, TPU with a shore value of D58 and since it deals with very fine structures the slicer (cura 4) got confused unless I set it to very fine resolution (0,1 mm layer height, initial layer height 0,2 mm). Important!

Another thing is that the magnets are sealed in by the printer. To make this easy I added a post processing script in cura, pause at height, selected layer number and made it pause at the very last layer before the top of the magnet containers is printed. This came out to be layer 17 on my setup but you better check it in cura's preview before you slice it.

When you put in the magnets check the polarity, North is up for one and South up for the other side. 

The magnets I used have a diameter of 8mm and a height of 3mm, cylindric shape.

Except the magnet containers the strip is just one or two layers thick. 7 segments with 2 layers are less flexible than the connecting 6 segments with 1 layer, and this gives the strip a tendency to fold itself int a rectangle shape when the magnets come together. Space enough for a 20 x 10 x 5 mm sponge cube which I cut from a kitchen sponge. With a sharp knife I cut that sponge cube deeply so that the filament can go through with sponge tissue at all sides.

It is a fast print, even with the pause for inserting the magnets it will be done in less than 10 minutes. Cura computes it needs 0,37m filament, ~1g.

Putting it all together takes a bit longer than the print. The last step, before actually using it is to cut the ends of the sponge so nothing hangs out and could get caught by the extruder or something.

Oh, some people recommend to put lube on the sponge (oil) while others warn to not do this. Search for it first.