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Slicing.md

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Slicing

This document explains how to get your slicer set up for multimaterial printing with Trad Rack. These instructions are mainly geared towards PrusaSlicer and SuperSlicer, but some parts may be relevant to other slicers (such as OrcaSlicer) that are based on Slic3r and PrusaSlicer.

Table of Contents

Provided slicer profiles

Example slicer profiles are provided for PrusaSlicer and SuperSlicer. These profiles are meant for use with a K3 running a Sherpa Micro extruder and Mosquito Magnum hotend, but they can be modified to fit other setups.

Prerequisites

These profiles assume you have included trad_rack_optional.cfg in your Klipper config and that you have a Print_Start g-code macro that takes the following parameters:

  • EXTRUDER: Hotend temperature
  • BED: Bed temperature

Setup

See the PrusaSlicer_Setup or SuperSlicer_Setup document for information on adding the provided profiles to your slicer, as well as any setup tips that pertain to that slicer specifically. In addition, if you are using a different printer or toolhead setup, you may need to change values in the "Single extruder multimaterial parameters" and "Toolchange parameters with single extruder MM printers" sections in the slicer. See toolhead-specific settings and filament settings for more details on these settings.

Experimental options

Experimental profiles are included that eliminate the ramming and/or unload gcode generated by the slicer in favor of using gcode or macros called by the toolchange command: print profiles with "No Unload" and filament profiles with "No Ramming" in their name. You must select a printer profile with "Experimental" in its name to allow these print and/or filament profiles to be selected.

In addition, if you use a "No Unload" print profile, you must modify post_process depending on where you have Python installed and where remove_unload.py is located on your computer. You can do this either in the slicer or by directly editing the Annex_K3_TR.ini file in a text editor. If you choose to edit Annex_K3_TR.ini, keep in mind that special characters such as " and \ must be escaped with a backslash. For example, here is the setting I use, shown in the slicer:

Plater: select profiles

And in the .ini file:

[print:*No Unload*]
post_process = "\"C:\\Users\\Ryan\\AppData\\Local\\Programs\\Python\\Python310\\python.exe\" \"C:\\Users\\Ryan\\Documents\\3d printing stuff\\TradRack_Beta\\Slicer_Scripts\\remove_unload.py\""

If you don't know where you have Python installed, you can use the following command in the terminal to get the path:

python -c "import sys; print(sys.executable)"

If the above command doesn't work, try using python3 instead of python.

The script requires the following slicer settings in your filament profile(s) to work:

  • set filament_unloading_speed_start to 100
  • make sure your end_filament_gcode starts with the comment ; Filament-specific end gcode

With the ramming and/or unload gcode removed, you will need to have some sort of replacement run in the pre_unload_gcode in the [trad_rack] section of your Klipper config. The simplest way to do this (assuming you have included trad_rack_optional.cfg) is to set variable_shape_tip to True in the [gcode_macro TR_Variables] section. Keep in mind that the provided Shape_Tip macro includes both ramming and unloading.

Changes to make to existing profiles

This section explains changes to make to an existing single-tool slicer profile. Setting names used here follow the "parameter names" that are used in the slicer config files; you can use the search function to see which settings these correspond to in the GUI.

Printer settings

The following changes should be made to the printer config file in the Printer Settings tab:

Common settings

  • extruders_count: Set this to the number of lanes.
  • single_extruder_multi_material: Set to true (1 in the config).
  • start_gcode:

    • Add the following lines to the beginning of the Start G-code section:

      CLEAR_PAUSE
TR_LOCATE_SELECTOR
T{initial_tool} MIN_TEMP={first_layer_temperature[initial_tool]}

      Explanation:

      • CLEAR_PAUSE: Clears the paused state.
      • TR_LOCATE_SELECTOR: See the G-Codes document for more details.
      • T{initial_tool} MIN_TEMP={...}: Loads the first filament into the toolhead.

    • Usually not required: if any g-code command or macro that gets called within your Start G-code section contains the M18 or M84 command, add the following to the end of the Start G-code section:

      TR_SET_ACTIVE_LANE LANE={initial_tool}

      [!NOTE] This includes commands that are called indirectly. For example, if the Start G-code section contains Print_Start and your Print_Start macro calls G28, and your config includes a [homing_override] section that causes G28 to call M18 or M84, this would still count.

      Explanation:

      • The M18 or M84 command disables all motors on the printer, including Trad Rack's motors. This will cause problems the next time Trad Rack tries to move its selector. Normally it is a bad idea to disable the motors inside your start g-code. However, it is sometimes used as a workaround in the [homing_override] section in order to allow the printer to move an axis without marking that axis as homed. For example, you may want to lift the z axis before homing x and y to ensure the nozzle does not scrape on the bed. If you do not want to remove M18 or M84 from the command or macro that is being called in your Start G-code section, the TR_SET_ACTIVE_LANE command can be used as shown above to force Trad Rack to set the selector's position without homing it again.
  • retract_length_toolchange: Set to 0 for all extruders.

Toolhead-specific settings

  • cooling_tube_retraction: Distance between the nozzle tip and the center of the "cooling tube." The cooling tube should start somewhere above the heatbreak throat and end somewhere below the extruder gears. I recommend having the top end below the top of the heatsink, but it can extend further if you wish (more experimentation needed). Note that the slicer recommends using the extruder/nozzle tip as the starting point, but the filament tip will likely break away from the molten filament above that point when unloading.

  • cooling_tube_length: See the above explanation for cooling_tube_retraction.

    See the drawing below for a visualization of the cooling tube settings. Colorful labels are slicer settings, and black labels in parentheses are references that are used to determine the starting or ending points of the slicer settings.

  • parking_pos_retraction: Set this to cooling_tube_retraction + cooling_tube_length / 2.

  • extra_loading_move: Set this to a negative number with an absolute value slightly less than that of parking_pos_retraction. For example, if parking_pos_retraction is 37, set this to -36.99.

  • Advanced wipe tower purge volume calculs:

    • In SuperSlicer, one of the options for purge volume calculations is to have the slicer calculate volumes based on each filament's pigment percentage. See the tooltips1 for more details on these settings:
      • wipe_advanced
      • wipe_advanced_nozzle_melted_volume
      • wipe_advanced_multiplier
      • wipe_advanced_algo

Print settings

The following changes should be made to the print config file in the Print Settings tab:

  • wipe_tower: set to true (1 in the config) unless you are using an alternative way of purging material.
  • single_extruder_multi_material_priming: set to false (0 in the config).
  • only_retract_when_crossing_perimeters: set to false (0 in the config) to avoid colors bleeding into each other when the nozzle moves over the print.
  • gcode_substitutions2:

    • PrusaSlicer:

      • in the config file:

        gcode_substitutions = "(SET_PRESSURE_ADVANCE ADVANCE=[0.]+)\\n";"Save_Pressure_Advance\\n${1}\\n";r;"Save PA before ramming"

      • or in the GUI:

        PrusaSlicer gcode_substitutions

        • Find: (SET_PRESSURE_ADVANCE ADVANCE=[0.]+)\n
        • Replace with: Save_Pressure_Advance\n${1}\n
        • Notes: Save PA before ramming
        • Make sure "Regular expression" is checked!

    • SuperSlicer:

      • in the config file:

        gcode_substitutions = "(SET_PRESSURE_ADVANCE ADVANCE=[0.]+)(?: EXTRUDER=extruder[0-9]*)?\\n";"Save_Pressure_Advance\\n${1}\\n";r;"See: https://github.com/supermerill/SuperSlicer/issues/2934 (3073 too)"

      • or in the GUI:

        SuperSlicer gcode_substitutions

        • Find: (SET_PRESSURE_ADVANCE ADVANCE=[0.]+)(?: EXTRUDER=extruder[0-9]*)?\n
        • Replace with: Save_Pressure_Advance\n${1}\n
        • Notes: See: https://github.com/supermerill/SuperSlicer/issues/2934 (3073 too)
        • Make sure "Regular expression" is checked!

Filament settings

The following filament parameters are relevant to multimaterial printing. See the tooltips1 for more details on these settings:

  • filament_loading_speed_start
  • filament_loading_speed
  • filament_unloading_speed_start
  • filament_unloading_speed
  • filament_load_time
  • filament_unload_time
  • filament_toolchange_delay
  • filament_cooling_moves
  • filament_cooling_initial_speed
  • filament_cooling_final_speed
  • filament_ramming_parameters

With the toolhead-specific printer parameters set as described in toolhead-specific settings, filament_loading_speed has no effect and filament_loading_speed_start has almost no effect since it is only used for a move with close to 0 length. For the rest of the settings, I recommend starting either with values from the provided slicer profiles or with values from Prusa's MMU filament profiles. The optimal values for each of these parameters may depend on your hotend and/or filament.

Footnotes

  1. In the slicer GUI, hover the mouse cursor over a parameter's textbox/checkbox to make the tooltip appear. ↩ ↩2

  2. These substitutions are required if you only set the pressure advance value at the start of the print. If you set the pressure advance value in your start_filament_gcode for each filament, then the substitutions are unnecessary (but there is no harm in having both). ↩