CNC Controls: Fanuc

Fanuc Mill: Locating Program Zero 270

This class describes how to determine work offsets and tool geometry offsets on the Fanuc 0-C mill control during setup.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 13

  • Language English


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Course Outline
  • Objectives
  • What Is Program Zero?
  • The Work Coordinate System
  • Considerations for Selecting Program Zero
  • Determining Work Offsets
  • Adjusting Work Offsets
  • Determining Tool Length Offsets
  • Adjusting Tool Length Offsets
  • Methods for Offsetting the Z-Axis
  • Determining Work Offsets in the Z-Axis
  • Calculating Cutter Compensation Offsets
  • Adjusting Cutter Compensation Offsets
  • Summary
  • Compare program zero to machine zero.
  • Describe the work coordinate system.
  • Identify common locations for program zero on the mill.
  • Explain common methods for determining work offsets.
  • Explain how to adjust work offsets on the Fanuc 0-C mill control.
  • Describe how to determine tool length offsets.
  • Explain how to adjust tool length offsets on the Fanuc 0-C mill control.
  • Describe disadvantages for setting Z-axis offsets against the part surface.
  • Explain the steps for determining work offsets in the Z-axis.
  • Describe the steps for determining cutter compensation.
  • Explain how to adjust cutter compensation on the Fanuc 0-C mill control.
Vocabulary Term

1-2-3 block

A precise metal block with dimensions measuring one, two, and three inches respectively. An operator can use a 1-2-3 block to touch off tools during setup.

center finding indicator

A measuring instrument that allows an operator to find the center of a hole on a part.

cutter compensation

An offset used on the mill that accounts for variations in tool diameter. Cutter compensation is necessary only for tools that travel in the X- or Y-axis.

dial indicator

A measuring instrument with a contact point attached to a spindle and gears that moves a pointer on the dial. Dial indicators have graduations that are available for reading different measurement values.

edge finder

A device used on a mill to locate the exact position of a part edge along the X-axis or Y-axis.


A ring or collar surrounding the toolholder that allows the tool to be grasped by the toolchanger.


The command code that defines program zero in a part program.


The command code that places the X- and Y-axes in a temporary home position.

gage line

The imaginary line marking the portion of the toolholder that matches the bottom edge of the machine spindle.

job sheet

A document that includes all manufacturing specifications for a lot of parts.

machine coordinate system

An unchangeable coordinate system that has machine zero as its origin.

machine zero

The position located at the farthest possible distance in a positive direction along the machine axes. This position is permanently set for each particular CNC machine.

manual reference position return

A procedure for returning a tool to a position specified by a parameter. The manual reference position return switch is located on the machine operator's panel.

part program

A series of instructions used by a CNC machine to perform the necessary sequence of operations to machine a specific workpiece.

program zero

The position that acts as the origin for the part program of a particular workpiece. This position is unique to each workpiece design, and it is selected by the part programmer.

reference plane

A surface chosen for touching off all tools on a mill. A reference plane can be defined relative to a vise, fixture, or object like a 1-2-3 block.

tool length offset

An offset used on the mill that accounts for variations in tool length along the Z-axis. Each tool requires its own offset, which is measured from the tip of the tool to the gage line.

work coordinate system

A variable coordinate system that has program zero as its origin.

work offset

An offset used to adjust the location of every tool loaded in the machine. On the mill, the work offset changes the position of the spindle in both the X- and Y-axes, and often the Z-axis as well.