My original Z18 extruder brush was seriously compromised by a bad print, trying to clean the brush was attempted but the brush had seen better days. I tried locating a replacement but was unable to find one available on the MakerBot support site. The brush had some inherent design problems, quite often the metal wires would be pulled back when the extruder parked and would impede the flow of plastic after exchanging filament. When the molten filament would flow around the wires it occasionally trapped the wires and pulled them out of the brush. It got so bad that the middle of the brush had lost half of the wires and was providing less than satisfactory cleaning action.
I found a silicone basting brush head online that is rated for 240°C, they were selling 3 for $5.99 so I ordered them and designed a replacement holder. Attempting to use the brush head unmodified was a disaster so I cut it down to fit within the space available.
I cut the brush in half along the narrow dimension and then across the second row of 'fingers' to leave two rows of alternating of fingers. This provided 2 parts per brush that were equally sized and had the same number of fingers. The print is designed to lock the base of the silicone brush in place with a little force. After I had the brush assembled I snapped it back into place and pushed the extruder through it. I trimmed the brush where it would miss the block but intersect the nozzle, approximately 15mm.
The brush works great, it cleans the softened filament as the extruder glides through and the filament does not stick to the silicone. The silicone is resilient enough to snap back after the extruder passes so it does not block filament extrusions during loading.
If you have suggestions please let me know!
Trimming the silicone brush
Makes sure to trim the silicone fingers after assembly, I cut them to intersect the nozzle but miss the extruder block.