In numerical control (CNC) machining,Fixture offsetUsed to define differentWorkpiece coordinate system(WCS) – It allows the machine tool to "know" the exact position of the workpiece on the table.

 

This functionality requires the G54–G59 code and the extended bias code G54.1 P1–P99。

 

What is fixture offset?

The origin of the CNC machine tool (machine tool zero point) is fixed, but the zero point of the workpiece (workpiece zero point) can be flexibly adjusted.

 

The function of the fixture offset is to tell the machine tool:

 

"For this workpiece, take this position as the (0,0,0) coordinate point."

 

With fixture offset, you can place multiple workpieces or fixtures on the table and switch between them with program control.

 

G-code rollup

G-code	illustrate
G54	Workpiece Bias 1 (Most Common)
G55–G59	Additional standard workpiece bias
G54.1 P1	Extended bias (P1 stands for bias number 1)
G54.1 P99	Support up to 99 extended biases

 

Typical application: G54 code

G54; Select the No. 1 fixture offset
G00X0Y0Z100; Move to workpiece zero (based on selected bias)


 

• The G54 applies the X/Y/Z axis offset that is predefined in the machine controller settings
• Thereafter, all G-code executions are based on the zero point of the artifact (i.e., running relative to the artifact coordinate system)

 

Tool representation example

Bias number	G-code	X-axis (mm)	Y-axis (mm)	Z-axis (mm)
1	G54	100.0	200.0	50.0
2	G55	300.0	200.0	50.0
3	G56	500.0	200.0	50.0
…	…	…	…	…

Each offset corresponds to a different workpiece zero point on the table.

 

Switching between fixtures

G54
(Machining program of the workpiece on the left)

G55
(Machining procedure for intermediate workpieces)

G56
(Machining program of the workpiece on the right)


This switching method is common in horizontal machining or in scenarios where multiple vises hold the workpiece.

 

G54.1 PN – Extended fixture offset

Many modern CNC machine controllers support extended bias functions from G54.1 P1 to G54.1 P99:

 

G54.1P6        ; Select Extension Fixture Offset No. 6

 

• Ideal for pallet exchange systems
• It is ideal for high-volume production or automated machining scenarios
• More than 6 offset stations are available compared to standard bias

Practical example: Multi-workpiece machining setup

G54; Left vise (clamped workpiece)
(Perform machining operations)

G55; Intermediate vise (clamped workpiece)
(Perform machining operations)

G56; Right vise (clamped workpiece)
(Perform machining operations)


Each workpiece has its own zero point – no need to modify the toolpath or reprogram the coordinates.

 

How to set up the fixture bias (manually or via G10 code)

 

The fixture offset can be set in three ways:

1. Set it up manually on the machine control panel
2. Automatic setup using the probe system
3. Set up programmatically via G10 code

 

Example (G10 code setup):

G10L2P1X100.0Y200.0Z50.0; Set G54 Bias (P1 corresponds to G54)
G10L2P2X300.0Y200.0Z50.0; Set G55 Bias (P2 for G55)


 

• code,L2Represents the "workpiece offset" type,P1corresponding to G54 bias,P2Corresponding to the G55 bias, and so on.

visualization
│   G54       │   G55       │   G56       │
│ Workpiece A │ Workpiece B │ Workpiece C │
└─────────────┴─────────────┴─────────────┘


• Each workpiece has its own fixture offset
• The same machining program can be used with different G-codes to machine workpieces in different positions

⚙️ Tips for using fixture offset

• ✅ Before you start cutting, be sure to activate the correct G54–G59 (or G54.1 Px) bias
• ✅ Use probe loops such as G65 or G43.4 codes to achieve automatic setting of bias
• ✅ If you need a fully automated setup, consider using the G10 code
• ✅ Exercise caution is exercised when simulating multi-bias programs to avoid tool collisions

 

Summary table

G-code	illustrate
G54–G59	6 built-in standard fixture offsets
G54.1 Pn	Up to 99 additional extended biases
G10 L2 Pn	Set the bias values programmatically

 

summary

The fixture offset gives the CNC machine the following capabilities:

1. Multiple workpieces are machined in a single machining cycle
2. There is no need to modify the toolpath for different fixture settings
3. Save time in high-volume production or repetitive processing

Mastering the use of fixture offset is the key to achieving professional CNC automation, modular fixture setting and rapid changeover production.