MK4 MMU3 Purge Volume Calibration

Found a way to get the calibration tests to print sequentially. Each successive purge volume is offset vertically by layer height in the editor view. That way each purge volume is classified into its own layer when sliced. After the first purge volume, the slicer thinks each layer will be printed over an air gap as bridge infill. A gcode substitution moves the nozzle down to the first layer just prior to printing bridge infill. With this method, all purge volume tests are printed sequentially on the first layer. With the purge tower we also get the magic of the MK4+MMU3 “cold pull” ramming that significantly reduces required purge volumes.

In fact there is so little color bleed with the MK4+MMU3 that the calibration might not even be necessary at all. Virtually every filament I have tried has required <50mm purge and for most 0mm purge seems to do perfectly fine. Even when switching between PLA and PETG no purge seems to be needed. Not sure how much I personally trust operating the MK4+MMU3 at 0mm purge yet, I need more hours on the printer to see if variance might cause color bleed on random layers if the “cold pull” fails or strings more than expected. But the calibration tests seem to indicate that MK4+MMU3 can work with 0mm purge for almost all filaments, which is insane.

Attached are the .3mf files with the purge permutations of 2, 3, 4, or 5 filaments.