OrcaSlicer purge tower replacement for Klipper-based off-bed purging

This is an OrcaSlicer post-processing script & companion klipper cfg file to allow passing customized purge values to klipper-based off-bed purging systems such as Blobifier, Goose Belt Purger, or the stand-alone purge function within Happy Hare.  

Why? Two main issues arise when disabling OrcaSlicer's purge tower to use any of these systems, as purge values rely on a fixed table of purge lengths between each filament, which is typically passed in gcode at the beginning of the file.

1) Enabling wipe-to-object-infill can reduce filament waste substantially, but is not compatible with normal off-bed purging methods because it relies on OrcaSlicer calculating the amount purged to infill and adjusting the remaining purge necessary at every single filament change.  As a result, this feature can only be enabled when OrcaSlicer is directly building each layer of the purge tower.

2) Displaying estimated filament usage in OrcaSlicer is only calculated for purge amounts when using an OrcaSlicer generated purge tower. Presumably this is because OrcaSlicer has no way of knowing what amount an off-bed purge method is actually using.  For example, some systems like Happy Hare have functions to accommodate for things like residual filament left in the nozzle during changes and can add an extra purge amount to compensate. Other systems, like Blobifier, have a provision for applying an overall ratio to modify the purge table values passed from the slicer. Enabling OrcaSlicer's purge tower at least gives us a starting estimate for filament used for purging, but of course the accuracy of this value depends on how your other Klipper scripts are configured.

3) Mid-print purge volume adjustments are possible as an added bonus. Ever wish you could add a touch more purge without restarting your print? With the included klipper macro, you can now change the ratio applied to purge volume calculations, or add/subtract a fixed amount to all future purges instantly, without interrupting your print.
 

What the post-processing script does:

1) At each filament change, all purge tower extrusion movements are tallied and the final total extrusion amount is passed to a custom klipper toolchange macro. 
2) Removes all purge tower movements from the gcode
3) Retains any temperature change commands within the toolchange section, with temperature increases left in place before the toolchange and temperature decrease commands moved to after the toolchange/purge is complete, to insure proper purging of residual filament even between filaments with substantially different print temps.
4) Removes any other extraneous X/Y movement commands found before the actual resumption of printing (yes, OrcaSlicer does this sometimes).

 

Instructions:

1) extract zip file to desired location. For windows users, OrcaSlicer post-processing script field should point to tower_replace.bat (and .py file should be located in the same folder).  Something like:

C:\OrcaSlicer_Scripts\tower_replace.bat;

2) upload tower_replace.cfg to your klipper config files and add an include line in your printer.cfg to point to it. Something like:

[include tower_replace.cfg]

3) Edit the config variables within tower_replace.cfg as necessary.  At a minimum, you will need to specify the macro name which should be called for the purge method which you are using, and the parameter name the macro uses to specify the purge volume.  For example, for a macro which might be called in the form of GOOSE_PURGE PURGE_VOLUME=XXX, then you would enter:

variable_purge_macro_name: ‘GOOSE_PURGE’
variable_purge_parameter_name: 'PURGE_VOLUME'

4) Optionally, you may also apply a modification to the purge values passed from OrcaSlicer with a scaling factor (1.0 = 100%, 0.7 = 70%, 1.3 = 130%, etc.) and/or add or subtract a fixed volume to account for excessive residual filament left in a high-flow nozzle or to otherwise modify purge values as desired.  This mirrors similar functionality found in Happy Hare and Blobifier. Please remember that modifying purge volumes in this way will reduce the accuracy of OrcaSlicer's total filament usage calculations.

5) Additional Klipper macros available for testing/tuning include:

TOWER_REPLACE_SET_MANUAL_PURGE 
(manually set the purge volume to a specific value)

TOWER_REPLACE_GET_NEXT_PURGE
(returns the currently saved purge volume)

TOWER_REPLACE_CONFIG
(returns the current values for scaling factor and fixed addition/subtraction amount)

TOWER_REPLACE_SET_CONFIG
(allows manually specifying scaling factor and fixed addition/subtraction amount - make sure to hardcode any changes in the config file afterwards, to preserve across reboots)

Usage Tips:

1. If using adaptive bed mesh, place the purge tower in the middle of your model. This will prevent probing of unnecessary areas of your bed where the deleted purge tower used to be. You may safely disregard any warnings of conflicting g-code paths related to the purge tower.

I've tested this extensively with my own setup (Happy Hare + Goose Belt Purger) and all works well, but please let me know if you experience any trouble with other setups.

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