Skip to content

Tip Shaping: Toolhead Cutting

What it does

An alternative to filament-movement tip forming: a toolhead-mounted cutter trims the tip cleanly instead, skipping the forming step (and its per-filament tuning) entirely. See Feature: Tip Forming and Purging for the concept, trade-offs, and the cut routine itself - this page covers the variables behind it. For worked toolhead-parking examples around a cutter specifically, see Toolchange Movement: Tip Cutting Options.

Where it's applied

_MMU_CUT_TIP, defined in mmu_cut_tip.cfg. Active once form_tip_macro: _MMU_CUT_TIP in mmu.cfg, which itself only becomes an available choice once a toolhead cutter is enabled (Toolhead sensors/settings → Has toolhead cutter? in menuconfig) - that's a separate capability from the choice of tip-forming method itself.

Selecting toolhead cutting

First enable Has toolhead cutter? under menuconfig's Toolhead sensors/settings ---> screen. Then open Tip Forming / Cutting --->, open Select standalone tip shaping option, and choose Tip cutting using toolhead cutter. This writes form_tip_macro: _MMU_CUT_TIP to mmu.cfg.

menuconfig Tip Forming and Cutting screen with toolhead cutting selected

Leave Happy Hare controlled in-print tip forming/cutting enabled when using the cutter, and disable the slicer's own tip forming. The optional Have servo operated gantry bumper? setting appears with this method; enable it and enter the servo pin only when the cutter is pressed against a deployable gantry-mounted bumper. Extruder tip forming current can temporarily boost the extruder from 100 to 150 percent during the cut sequence; 100 disables the boost.

Have servo cutter at MMU? is a different, additive cutter at the MMU end of the bowden. It is covered under Tip Shaping: MMU Cutting.

Configuration

menuconfig: Toolhead tip cutting (_MMU_CUT_TIP) screen, showing blade/pin geometry, cut speeds, and gantry servo settings

_MMU_CUT_TIP_VARS in mmu_macro_vars.cfg, reachable from menuconfig's Macro Variables → Toolhead tip cutting (_MMU_CUT_TIP) screen shown above, once the capability flag above is on. Full variable table: Macro Variables: Toolhead tip cutting. Tune the same one-variable-at-a-time way as tip forming (see Feature: Tip Forming and Purging) - the variables themselves just live in this different section.

A few settings are worth knowing about specifically:

  • pin_loc_xy/pin_loc_compressed_xy are the depressor pin's real and fully-compressed X,Y coordinates - both toolhead-specific and not something to copy from another build.
  • cutting_axis (x or y) and cut_axis_steppers/ cut_stepper_current choose which axis the cut motion happens on, and an optional temporary current boost (up to ~150%) on the steppers doing the cutting move.
  • cut_iterations repeats the cut - raise it if your cutter struggles with a particular filament.
  • pushback_length pushes the cut fragment back into the hotend so it can't cause a future clog - a PTFE-tube-length-plus-a-few-mm starting point, not the couple of millimeters that might look sufficient at first glance.

See also