MMU Spool Buffer

Working with multiple filaments, as conceived in Pruša MMU assumes the exchange of filaments from multiple spools. The work mode consists of extruding the filament of one color and inserting a different color. The length of the extruded filament is quite large. Because the filament is stiff it creates loops of extruded parts interlaced, which paralyzes the function.
The solution uses a filament spool as a buffer. When the filament is pulled into the printer, it is unwound from the spool. When the filament is ejected, the spool is driven in reverse direction using the weights. The length of the filament that the MMU returns is constant, but the spools are of different sizes and the radius from which the unwinding is currently occurring differs. Weights, causing reverse movement associated with the spool by means of a gear transmission.

Print instructions

• For printed parts use PLA. Printlayer thickness 0.2 mm. Nib printed at a layer 0.15 mm.
• The spools of the print filaments have different internal diameters. Use suitable insert (50/52). A strip of cardboard can be used to fill in larger clearance