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Calibration Overview

StealthChanger calibration consists of three primary stages: Probe Offset, Dock Positions, and G-code Offsets.

Important Notes

  • Only home/QGL/bedmesh with tool 0. — Homing with other tools should only be done in order to switch to tool 0 which then can be used to home (again)/QGL/bedmesh.
  • The gcode_z_offset, gcode_x_offset and gcode_y_offset variables for tool 0 must always be zero. — The offset values are relative to tool 0.

Before You Start

  • Because all G-code calibrations are relative to tool 0, it is essential that the printer has perfect first layer bed adhesion with tool 0 first.
  • It is recommended that you run a test print with tool 0 before calibrating any G-code offsets.
  • Home/QGL/bedmesh is possible with any tool — Requires the scanner to be mounted on the shuttle.
  • gcode_z_offset variable must be set for every tool — Homing with the scanner on the shuttle requires each nozzle to have a z offset relative to the scanner.
  • gcode_x_offset and gcode_y_offset variables for tool 0 must always be zero. — The offset values are relative to tool 0.

Before You Start

  • It is essential that the printer has perfect first layer bed adhesion with tool 0 first.
  • It is recommended that you run a test print with tool 0 before calibrating any G-code offsets.

Probe Offset

Probe offset refers to the [tool_probe] parameter z_offset which is applied whenever the printer homes or performs bed leveling. This value represents the vertical distance between the probe’s trigger point and the nozzle tip, allowing Klipper to accurately determine the true Z=0 position for a given tool. A z_offset must be calibrated for T0, and for any additional tool that will be used for homing.

I'm building all my tools from the same hardware

Even when using identical hardware, each tool may require a unique z_offset due to:

  • Variations in hardware components.
  • Differences resulting from printing or assembly tolerances.
  • Slight deviations between the nozzle’s physical zero point and the probe’s trigger point.

Accurate z_offset values ensure consistent and reliable first-layer performance across all tools.

Dock Positions

Dock Positions refers to the [tool Tn] parameters params_park_x, params_park_y, and params_park_z. These values tell the printer the precise coordinates required to pick up or return a tool to its designated dock. In essence, a dock position defines the exact X/Y/Z point where the shuttle aligns with a tool so that the mechanical coupling can occur reliably. You can think of it as the tool’s pickup location for its specific dock.

Each tool requires its own dock position because the docks are mounted at different locations along the front of the printer. Even small variations in mounting or alignment can cause the shuttle to miss the tool or collide with the dock.

When dock positions are accurately calibrated, tool changes are consistent, repeatable, and free from collisions.

Calibrate you printer first

Before setting dock positions, it is strongly recommended to calibrate your printer’s zero point.

Dock positions are defined relative to absolute zero—if the printer’s zero point changes, the dock positions will shift accordingly.

G-code Offsets

G-code offsets refers to the [tool Tn] parameters gcode_z_offset, gcode_x_offset and gcode_y_offset. These values determine the difference in the nozzle's position for each tool when it is on the shuttle, relative to T0.

Why G-code offsets matter

When the slicer generates G1 X100 Y100, every tool should deposit filament at exactly the same physical location on the bed. G-code offsets make this possible by telling Klipper "this tool is 0.2mm left and 0.1mm forward off the reference tool, so adjust accordingly."

G-code Offset Calibration Methods

There are multiple methods of calibrating the G-code offsets,

  • Manual – Measuring the physical distance between nozzle offsets with a printed tool. This is the most time consuming method, but requires no additional hardware.

  • SexBall Probe – A modified Sexbolt Z Endstop that provides automated nozzle calibration. The hardware components for the SexBall Probe are included as a part of LDO's StealthChanger Base Kit.

  • Axiscope – Semi-automatic camera-based visual alignment. Gives you the ability to visually see and calibrate the XY offsets through a magnified lens. Z offset is handled by use of a Z endstop/probe.

  • Nudge – A DIY multi axis probe where the shaft is suspended in a wobbler that provides automated nozzle calibration.

  • KTAMV – Klipper Tool Alignment (using) Machine Vision. Uses machine vision to determine the XY nozzle calibration. Results may vary depending on camera choice, lighting and nozzles used.

  • NozzleAlign – A DIY multi axis probe.