G62 Automatic Corner Override G-Code Guide: Fanuc, Siemens, Mitsubishi

Introduction

An uncompensated coordinate shift or a geometry axis switchover executed with parameter MD 10604 set to 0 deactivates active working area limitations in the basic coordinate system. When the tool turret indexes and executes absolute positioning commands, the tool nose can bypass soft limits and drive the cutting tool directly into physical workholding components—such as table-mounted fixture clamps, workpiece vise jaws, or the rotating jaws of a spindle chuck. This abrupt physical impact results in a catastrophic hard collision, shatters the cutting tool, damages the axis ball screws, generates severe axis overload alarms, and converts raw stock into a completely ruined scrap part. During inside contour profiling, the physical volume of material being removed rapidly increases as the tool is wrapped by the corner wall, causing a sudden spike in cutting load that deflects the cutter and distorts the machined surface. Implementing G62 automatic corner override mathematically scales and moderates the feedrate within corner deceleration zones, ensuring constant tool loading and uniform surface quality.

Technical Summary

Quick Read

• Activate G62 modally before cutting inside corners to automatically scale down feedrates and prevent tool deflection.
• Switch back to G64 cutting mode to cancel G62 corner overrides modally on straight, non-critical paths to optimize cycle times.
• Verify that parameters 8007, 8008, and 8009 are configured with non-zero values to avoid silent disabling of the corner override function.
• Do not command skip functions like G31 while nose radius compensation is active, as this triggers severe program errors or tool collisions.
• Maintain working area limitations (G25/G26 or G22/G23) to protect physical turret, measuring station, and workholding components during manual intervention.
• Execute G291 to toggle the Sinumerik interpreter into ISO Dialect mode when executing legacy G62 commands.

Basic Concepts

Automatic Corner Override (G62) is designed to manage feedrate changes at inside corners during cutting feed interpolation. When machining inside pockets or profiles, the physical volume of material being removed (the machining allowance) increases rapidly because the tool is wrapped by the corner wall. Without automatic adjustments, this sudden spike in the cutting load can deflect the tool, distort the machined surface, and degrade dimensional accuracy. Programmers and setup operators must establish proper parameters to scale down the feedrate in these deceleration zones to ensure constant tool loading, uniform surface finish, and prolonged tool life.

To achieve this moderation, the motion controller calculates the tool center path based on the workpiece coordinate system and active tool radius or tool nose radius compensation (G41/G42). If the inner corner angle is less than the configured threshold, the controller automatically applies the override percentage to the programmed cutting feedrate. The feedrate reduction starts inside the designated deceleration zone distance before the corner and continues until the tool exits the zone, maintaining a balanced cutting force.

Setup operators must ensure that G62 is modally canceled by commanding G64 (cutting mode) or G40 (compensation cancel) before executing straight paths or non-critical zones to avoid unnecessarily slow cycle times. In addition, if the parameter values for the override percentage, maximum corner angle, or deceleration zone range are configured to boundary values (like 0 or 180), the corner override is silently disabled. This requires operators to inspect the control parameters directly to confirm the override is active.

Command Structure

The G62 command is a modal preparatory function that activates automatic corner feedrate reduction for subsequent blocks. Once commanded, the control applies feedrate modifications to all linear (G01) and circular (G02/G03) movement commands. It remains modally active until canceled by executing cutting mode (G64), exact stop check (G61), high-accuracy control (G61.1), tapping mode (G63), or tool radius compensation cancel (G40).

To program the command, G62 is written in a standalone block or prefixed before coordinate blocks. For Fanuc and Mitsubishi controls, the command behaves as a standard modal G-code. For Siemens controls, G62 belongs to Group 57 and can be programmed alongside motion paths or combined with dynamic rounding parameters.

; Fanuc & Mitsubishi Syntax
G62 ;
G01 X100.0 Y50.0 F500 ;
; Siemens Native Syntax (G290 mode)
G62 G01 X100.0 Y50.0 F1000 ;
G621 ;
FENDNORM ;

Brand Applications

Fanuc

Fanuc systems implement G62 as a modal Group 15 Turning G-code or Group 13/19 Milling G-code. It relies on parameters such as Parameter No. 8007 and Parameter No. 8008 to determine corner overrides.

To apply G62 on Fanuc, tool radius compensation (G41/G42) must be active, and G62 is commanded in a separate block prior to linear cutting moves: G62 ; G01 Y150.0 ;.

Warning: Issuing skip command G31 during active nose radius compensation is strictly prohibited and immediately halts the machine.

Siemens

Siemens controls parse G62 under Group 57, which determines corner deceleration at inside corners. The reset default behavior is configured by parameter $MC_GCODE_RESET_VALUES[7].

The command is programmed in native mode (G290) or using the G291 interpreter to parse ISO dialect: G290 ; G62 X150.0 Y100.0 ;.

Warning: Resuming automatic cycles after a geometry axis switchover with MD 10604 set to 0 deactivates basic working area limitations, which can lead to tool collisions.

Mitsubishi

Mitsubishi systems map G62 to Group 13 in milling or Group 15 in turning. The motion controller uses Parameter #8007 and Parameter #8008 to execute inside corner overrides.

To operate, tool radius compensation (G41/G42) must be active, and G62 is initialized in a separate block: G62 ; G01 X100.0 Y50.0 F1000 ;.

Warning: Changing compensation direction during nose radius compensation triggers Program Error P157 unless commanded in rapid traverse positioning blocks.

Brand Comparison

Technical Analysis

An analytical comparison of these CNC controls reveals distinct path interpolation and look-ahead preprocessor strategies. Fanuc uses a flat parameter architecture where parameters such as Parameter No. 8007 and Parameter No. 8008 directly control feedrate scaling. While this enables high-speed execution, it lacks dynamic path adjustment and restricts modal co-existence, since G62 cannot coexist with high-accuracy modes like G61.1 or G08.

Siemens Sinumerik controls implement a more complex, bilingual compilation structure. Programmers must switch interpreters via G290 and G291 to process Siemens native commands or external ISO dialect codes. Instead of relying on static distances, Siemens integrates corner deceleration (Group 57) with continuous-path modes (Group 10, such as G642 or G643) that dynamically calculate axis dynamics and rounding tolerances using axial parameter MD 33100.

Mitsubishi controls feature a bimodal program compiler mapping. Toggling G188 maps commands to machining center formats, whereas G189 maps coordinates back to turning environments. Additionally, Mitsubishi supports manual arbitrary reverse run (G127), which allows the operator to execute a manual rollback using a handwheel. The motion kernel tracks active G62 feedrate overrides and tool compensation vectors using a modal information storage block, preventing axis drift during recovery. In milling systems, Mitsubishi also separates automatic corner override and inner arc override, keeping the inner arc override active even when feedrate overrides are disabled.

Program Examples

Fanuc Example

G90 G17 G41 D01 G01 X50.0 Y50.0 F500 ; Start-up cutter radius compensation left on the XY plane
G62 ; Activate Automatic Corner Override mode to reduce feedrate at inside corners
G01 Y150.0 ; Linear movement, G62 override applies dynamically at inside corner deceleration zones
G64 ; Switch to modal Cutting Mode (G64) to cancel G62 automatic corner override

Dry run: The control initializes cutter radius compensation left (G41) and starts cutting at a feedrate of 500 mm/min. When G62 is commanded, the control monitors inside corners. During the G01 move to Y150.0, the feedrate dynamically scales down as the tool enters the inside corner deceleration zone. Switch to G64 cancels G62 corner override modally.

Siemens Example

G290 ; Switch interpreter to native Siemens SINUMERIK mode
G17 G64 G41 T1 D1 G01 X100.0 Y50.0 F1000 ; Activate XY plane, continuous-path mode, and TRC left
G62 X150.0 Y100.0 ; Enable automatic corner deceleration for inside corners along the linear path
G621 ADIS=0.5 ; Switch modally to corner deceleration at all corners with transition rounding

Dry run: The system switches to native Siemens mode (G290) and activates continuous-path mode (G64) with tool radius compensation (G41). When G62 is active, the control decelerates the path velocity at inside corners. Switching to G621 ADIS=0.5 applies corner deceleration at all corners with a transition rounding of 0.5 mm.

Mitsubishi Example

G90 G17 G41 D01 G01 X100.0 Y50.0 F1000 ; Start-up tool radius compensation on the XY plane
G62 ; Modally enable Automatic Corner Override to scale feedrate at inside corners
G64 ; Cancel G62 modally by switching to Cutting Mode G64

Dry run: The controller activates tool radius compensation left (G41) on the XY plane. Commanding G62 activates automatic corner overrides. In subsequent coordinate blocks, the cutting feedrate scales down automatically in inside corner deceleration zones. Switch to G64 cancels G62 and restores standard cutting feedrates.

Error Analysis

Application Note

A catastrophic hard collision shatters the cutting tool, damages the axis ball screws, generates severe axis overload alarms, and converts raw stock into ruined scrap when the tool revolver (turret) travel path is shifted during manual intervention. Setup operators must verify that workpiece finishing contours are programmed under active radius compensation (G41/G42). If parameter No. 10604 is set to 0, working area limitations are deactivated during axis switchovers. Programmers must ensure that G62 is canceled by commanding G64 or G40 before executing straight paths to prevent excessive cycle times. Additionally, operators must watch out for parameter settings: if override parameter #8007, maximum angle parameter #8008, or deceleration zone range parameter #8009 are set to 0, automatic corner override is silently disabled, resulting in unexpected cutter deflection at corners. Skip functions like G31 must never be commanded during active radius compensation to avoid immediate machine shutdown.

Related Command Network

• G60 Single Direction Positioning: Enforces unidirectional axis approach to eliminate physical mechanical backlash, whereas G62 automatically scales feedrates at inside corners.
• G61 Exact Stop Mode: Forces axes to decelerate to a complete stop at the end of each block to check positioning, which modally cancels G62 corner overrides.
• G54 Workpiece Coordinate System: Establishes the primary workpiece coordinate reference frame on which the G62 path interpolation coordinates are calculated.
• G09 Exact Stop (Non-modal): Decelerates axes to a complete stop to verify positioning for a single block, whereas G62 is a modal override command.
• G64 Cutting Mode: Cancels G62 corner overrides to restore normal feedrate blending across block transitions.

Conclusion

Integrating G62 automatic corner override within toolpaths balances mechanical load changes and maintains surface quality across inside profiles. Setup operators must verify that corner parameters match tool geometries and that exact stop modes are canceled outside critical areas to optimize production cycle times.

FAQ

Why does G62 fail to apply feedrate overrides on straight paths

The G62 motion kernel calculates deceleration zones only at inside corner boundaries under active cutter radius compensation (G41/G42). Operators must verify that tool radius compensation is active and that the programmed angle falls within the parameter maximum to trigger deceleration.

How is silent disabling of automatic corner override detected

If parameters #8007, #8008, or #8009 are set to zero, the control disables G62 without throwing alarm codes. Operators must inspect parameter values directly on the control screen to confirm they are configured correctly.

What is the difference between G62 corner override and inner arc override

Automatic corner override scales feedrates at inside corners along straight paths and is disabled by feedrate override OFF parameters. Inner arc override remains active for circular arcs even when feedrate overrides are deactivated, requiring programmers to manage both functions in the motion controller.