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Toolhead Variable Calculation

This document describes how to calculate the toolhead variable in the AFC Klipper add-on. These variables are crucial for ensuring that the toolhead operates correctly with the AFC system.

Note

The following documentation pertains to the use of a toolhead cutter primarily. While some of the information may be applicable if you are using tip-forming, our official recommendation is to use a toolhead cutter.

These primarily consist of 2 variables:

  • tool_stn: The distance from the toolhead sensor (typically the pre-extruder sensor) or extruder gears (if using ramming) to the top of any filament remaining in the hotend.
  • tool_stn_unload: The distance the toolhead needs to move to unload the filament.

tool_stn Calculation

The tool_stn variable is the distance from the toolhead sensor/top of extruder gears(ramming) to the top of any filament remaining in the hotend. This takes into account the amount of filament that is left in the hotend after the pushback and retract operations of the cut macro have been performed.

The easiest way to calculate this value is to start with a recommended value based on your toolhead/extruder combination. A table of common values is provided here.

Note

It may be easier to temporarily disable the AFC_POOP macro while you are adjusting the tool_stn value, as this will provide an easier way to observe the filament extruding from the hotend. Run AFC_TOGGLE_MACRO TOOL_CUT=0 to disable the macro, and AFC_TOGGLE_MACRO TOOL_CUT=1 to re-enable it after you have finished adjusting the value.

Once you have a recommended value, fine-tune it by performing the following steps:

  1. Unload the filament completely from the toolhead. This can be done by using the TOOL_UNLOAD LANE=<lane> command in the Klipper console.
  2. Load the filament into the toolhead using a toolchange command, such as T1.
  3. Observe the filament to see if it is extruding out of the hotend. If an excessive amount of filament extrudes out, you will need to decrease the tool_stn value. If no filament extrudes, you will need to increase the tool_stn value.
  4. Repeat steps 1, 2 and 3 until you find a value that works for your toolhead/extruder combination.

Use the following command to adjust the tool_stn value without having to restart the system:

UPDATE_TOOLHEAD_SENSORS EXTRUDER=<extruder> TOOL_STN=<length>

Once you have found a value that works, save it to the configuration with the following command:

SAVE_EXTRUDER_VALUES EXTRUDER=<extruder>

Note

Don't forget to re-enable the AFC_POOP macro by running AFC_TOGGLE_MACRO TOOL_CUT=1 after you have finished adjusting the tool_stn value if you disabled it earlier.

tool_stn_unload Calculation

The tool_stn_unload variable is the distance that the filament moves when the toolhead is unloaded, after the cut macro is executed and any pushback and retract operations have been performed.

Like adjusting the tool_stn value, start with a recommended value based on your toolhead/extruder combination and use the following steps to fine-tune it:

  1. Completely load the filament into the toolhead using a toolchange command, such as T1.
  2. Manually extrude filament until observe it coming out of the hotend. This will help reduce the changes of a jam occurring during the unload operation.
  3. Manually execute the AFC_CUT macro to perform a cut operation.

  4. Using a manual extrude command, retract the filament by a set amount, until the toolhead sensor is no longer triggered.

    For example, if your estimated tool_stn_unload value is 62mm, start by issuing a manual retraction for 55mm and then manually retracting 1mm at a time until the toolhead sensor is no longer triggered. If using ramming retract until filament is out of toolhead extruders gears.

  5. Once you have found the value that works, save it to the configuration with the following command:

UPDATE_TOOLHEAD_SENSORS EXTRUDER=<extruder> TOOL_STN_UNLOAD=<length>
SAVE_EXTRUDER_VALUES EXTRUDER=<extruder>