Master Taper Turning Using G90 Modal Cycle: CNC Programming Guide

G90 Modal Turning Cycle

G90 Turning Cycle is briefly explained in this cnc tutorial G90 Turning Cycle.

For an Example of Straight Turning with G90 Modal Turning Cycle read G90 Turning Cycle Fanuc – CNC Program Example Code.

G90 turning cycle is used for simple turning however multiple passes are possible by specifying the X-axis location of additional passes.

What is Modal

“Modal” G code meaning that they stay in effect until they are cancelled or replaced by a contradictory G code. Same way G90 is a modal G code it remains active until another motion command is given like G00, G01 etc. As in the cnc program example below G90 G code is cancelled with G30 G code.

G90 Turning Cycle Usage

• Straight turning.
• Boring operation.
• Taper cutting.

This cnc program shows usage of G90 taper turning.

Taper Turning with G90 Turning Cycle

CNC Program Example

Taper Turning with G90 Modal Turning Cycle – CNC Example Code

G30 U0 W0
G50 S2000 T0100
G96 S200 M03
G00 X61.0 Z2.0 T0101 M8
G90 X55.0 W–42.0 F0.25
X50.0
X45.0
X40.0
Z-12.0 R-1.75
Z-26.0 R-3.5
Z-40 R-5.25
G30 U0 W0
M30

As you can see in the above cnc program example you yourself have to calculate the taper value.

Tool Path Explanation

The figure below shows how tool travels when running the above program

If possible you can use G71 turning cycle which makes every calculation for us.
Another point is G90 turning cycle can only make straight and taper cuts, you can’t cut any arc (circular interpolation) with G90 turning cycle.
Instead G71 cuts straight, taper, arc also.

Alternative of G90 Turning Cycle

1. CNC Fanuc G71 Turning Cycle or Stock Removal Canned Cycle
2. G71 Rough Turning Cycle One-line Format
3. CNC Programming Example with Fanuc G71 Rough Turning Cycle and G70
4. Fanuc G70 G71 Rough and Finish Turning Cycle Program Example