Cutter compensation

Cutter compensation in CNC (Computer Numerical Control) machines is a crucial feature that ensures precise machining by accounting for the size of the cutting tool. This allows the machine to adjust the tool path so that the final machined part matches the intended design, regardless of the cutter’s diameter.

There are two primary types of cutter compensation used in CNC programming:

1. Cutter Radius Compensation (CRC):

Cutter radius compensation adjusts the tool path based on the radius of the cutting tool. It ensures that the tool cuts at the correct distance from the programmed path, which is especially important when machining contours or profiles.

• G41: Activates left-hand CRC. The tool is offset to the left of the programmed path when looking in the direction of travel.
• G42: Activates right-hand CRC. The tool is offset to the right of the programmed path when looking in the direction of travel.
• G40: Cancels CRC, returning the tool to the exact programmed path. Example:

   G01 X10 Y10 F500 (Move to starting point)
   G41 G01 X20 Y20 D01 (Activate left-hand cutter radius compensation with tool #1)
   G01 X30 Y30 (Continue cutting)
   G40 G01 X40 Y40 (Cancel cutter radius compensation)

In this example:

• D01 refers to the tool table entry for the specific tool being used, which contains the tool’s radius or diameter.
• The tool will cut along a path that is offset by its radius, ensuring the final part matches the desired dimensions.

2. Cutter Length Compensation (CLC):

Cutter length compensation adjusts the Z-axis position of the tool to account for variations in tool length. This is particularly useful when using multiple tools of different lengths in the same program.

• G43: Activates CLC in the positive Z direction.
• G44: Activates CLC in the negative Z direction.
• Hxx: Specifies the tool length offset value from the tool table. Example:

   G00 Z100 (Rapid move to safe Z height)
   G43 H01 Z5 F500 (Activate cutter length compensation for tool #1 and move down)
   G01 Z-5 F100 (Cut at Z-5)
   G49 G00 Z100 (Cancel cutter length compensation and return to safe Z height)

In this example:

• H01 refers to the tool length offset for tool #1, which is stored in the machine’s tool table.
• The machine will adjust the Z-axis position based on the tool’s length to ensure accurate depth of cut.

Key Considerations:

• Tool Table: Both cutter radius and length compensation rely on the tool table, where the tool’s dimensions (radius/diameter and length) are pre-programmed.
• Activation/Deactivation: Always activate and deactivate compensation appropriately to avoid overcutting or undercutting.
• Direction of Travel: When using G41/G42, ensure the direction of travel aligns with the desired side of the part (left or right).

By properly applying cutter compensation, CNC machines can achieve high precision and accuracy, even when using tools of varying sizes and lengths.