Tool Nose Radius Compensationon Turning Centers

CNC Applications

Facing and Straight Turning

• When facing or straight turning, the tool nose radius has no effect on the part other than leaving a radius on inside corners.

Theoretical sharp point is what we program.

This tangent point finishes diameters.

This tangent point finishes faces.

The ProblemWhen turning tapers or radii, the tool nose radius leaves excess material as shown here:

Excess Material Here

The Solution

1. Manually program the exact tangent points. This is time consuming since it requires trig calculations or accurate CAD drawings to locate the tangent points.

2. Use tool nose radius compensation. The tool nose radius is entered into the machine controller, and the program turns on compensation for finish cuts only, and then turns it off. The machine calculates the tangent points so we can continue programming as if the cutter has a sharp point.

Tool Nose Radius G Codes

Compensate for tool nose radius to the RIGHT of the programmed path.

G42

Compensate for tool nose radius to the LEFT of the programmed path.

G41

Cancel tool nose radius compensation.G40

ApplicationG Code

G41 & G42

G41 – the cutter is to the left of the work when looking in the direction of the cut.

G42 – the cutter is to the right of the work when looking in the direction of the cut.

Turning Nose Radius Compensation On

Start Point of Finish Passwith Compenation On,0.1 Away in Z.

Compensation Point, 0.1 AwayFrom Start Point in Z, 0.2 in X.

Turn Nose Radious Compensationon in This Move.

To turn compensation on, the machine must move at least the distance of the nose radius in X and Z. For easy calculations, back away from the start point 0.1 in Z and 0.2 in X. Remember X is diameter based, so 0.2 in X is actually 0.1 radially.

Turning Nose Radius Compensation Off

Feed Moves Clearof the Part.

Feed Move to TurnNose Radius Compensation Off.

To turn compensation off, we feed the cutter completely off the work and then make a move larger than the nose radius while calling G40.

Note: Do not reverse the Z direction with nose radius compensation on! The machine may get confused, and then later cuts may be off by some multiple of the nose radius. Always call G40 BEFORE reversing the Z direction!

A G42 Example

Ø2.500 Ø1.500

R0.375

0.2500.625

1.000

2.000

Ø1.750

0.25x45°

We will program ONLY the finish pass on this part using G42 right tool nose radius compensation. We are given 800fpm cutting speed and 0.006ipr feed.

The Finish Pass

Program Start

Load the V insert tool.

Cap the RPM.Set the cutting speed to 800fpm, forward direction.Rapid to the G42 start point in Z.Rapid to the G42 start point in X, coolant on.Move to turn nose radius compensation on, beginning of chamfer.Machine the chamfer.Machine the straight 1.0” diameter.Machine the taper.Machine the radius.Feed clear in Z leaving room for the 0.125” parting tool.Feed clear in X.Move to turn off nose radius compensation.Program End

% O999G20 G40 G99 G28 U0 G28 W0T0303 G54G50 S4000G96 S800 M3 G0 Z2.2X1.0 M8G42 G1 X0.8 Z2.1 F0.006X1.5 Z1.75Z1.0X1.75 Z0.625G2 X2.5 Z0.25 I0.375 Z-0.15X2.875G40 X3.075 Z-0.25M9 M5 G28 U0 G28 W0 M30 %

ActionProgram Codes

The Final Pass

Select this link tostart the animation.