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LinuxCNC Axis GUI – Operator Guide (PROBOTIX Version)

This guide explains how homing, work offsets, and touch-offs work together using the PROBOTIX-customized Axis interface.

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Axis Interface Overview

Key Areas:

1. Manual Control Panel (Left)
   • Axis selection (X / Y / Z)
   • Jog controls
   • Set Selected Axis Origin
   • Origin X/Y
   • Origin Z
2. Preview Window (Right)
   • Displays toolpath and machine position
   • Shows X, Y, Z coordinates
3. DRO (Digital Readout)
   • Shows current position in active coordinate system (typically G54)
4. Status Bar (Bottom)
   • Active coordinate system (G54)
   • Tool status
   • Machine state

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Machine Coordinates vs Work Coordinates

Machine Coordinates (HOME)

• Set by homing the machine
• Fixed reference point
• Does not change unless re-homed
• Represented by the G53 coordinate system

Work Coordinates (G54 - G59.3)

• Nine possible coordinate systems (G54, G55, G56, G57, G58, G59, G59.1, G59.2, G59.3)
• Set by the operator
• Defines where the part is located
• Changes for every setup
• Can be used for repeatable fixture placement for production parts to make setup easier

Concept:

     Machine Zero (HOME)
         ↓
     Work Offset (G54)
         ↓
     Current Position

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Homing (Required Before Operation)

What Homing Does:

• Moves each axis to its switch
• Establishes Machine Zero (HOME)
• Enables accurate motion and limits

Important:

• Required before running any G-code program
• Required before executing MDI commands
  • (Many UI buttons execute MDI commands internally)
• Homing only needs to be done once per software session

Re-home whenever:

• The machine has been powered off and turned back on
• The machine crashes or loses position
• The control software is restarted
• You are unsure of machine position

Important:

• Stepper motors do not retain exact position when powered off
• On power-up, motors may shift slightly as they energize
• On dual-motor axes (such as Y), this can introduce slight gantry skew
• Homing re-squares the machine and restores accurate machine coordinates

WARNING:

You MUST home the machine after every power cycle. Stepper motors do not maintain exact position when powered off. Failure to re-home can result in positional errors or gantry misalignment, especially on dual-motor axes.

Procedure

1. Power on machine
2. Enable machine
3. Click Home All

WARNING:

You will not be able to run a program or use interface buttons before homing. The machine position is unknown until homed.

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Work Offset System (G54-G59.3)

LinuxCNC uses coordinate systems:

Offset	Use Case
G54	Default (most jobs)
G55-G59.3	Multiple fixtures or setups

A work offset stores:

• X shift
• Y shift
• Z shift

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Setting Work Zero (PROBOTIX Workflow)

Step 1: Set XY Origin

1. Jog to desired XY location on your part
2. Click Origin X/Y

Result:

     X = 0
     Y = 0

Step 2: Set Z Origin

1. Move tool to material surface
2. Click Origin Z

Result:

     Z = 0

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Step 3: Fine Adjustment (Optional)

Use Set Selected Axis Origin for:

• Single-axis adjustments
• Precision corrections
• When using edge finders, probes, or spacers to accurately locate edges or surfaces

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Manual Tool Changes (Critical)

Key Rule:

• X and Y stay the same
• Z must be reset

Workflow

1. Change tool
2. Move tool to reference surface
3. Click Origin Z

WARNING:

After changing tools, you MUST re-set Z using Origin Z. Failure to do so will result in incorrect cutting depth or machine crashes.

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Z Re-Touch Between Manual Tool Changes

If material has been removed or surface changes:

1. Jog to a valid reference location
2. Click Origin Z

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What You Are Actually Doing

• Homing → Defines where the machine is
• Origin X/Y → Defines where the part is
• Origin Z → Defines tool height for the current tool

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Common Mistakes

• Not homing before running a program
• Running MDI commands before homing
• Forgetting to re-set Z after manual tool changes
• Using the wrong coordinate system (not G54)
• Setting origin incorrectly

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Quick Reference

STARTUP:
    Home All

SETUP:
    Jog to XY → Origin X/Y
    Touch Z → Origin Z

TOOL CHANGE:
    Change tool
    Re-touch Z → Origin Z

RUN:
    Cycle Start