The G71 Longitudinal Roughing Cycle is a powerful G-code used in CNC programming for Mazak and Fanuc controls. It allows for efficient material removal in roughing operations, particularly in turning processes.

Usage Format

The basic format for the G71 cycle is as follows:

G71 U(Peck Depth) R(Retract Amount);
G71 P(Start of Profile) Q(End of Profile) U(Finish Allowance in X) W(Finish Allowance in Z) F(Feed Rate);

Explanation

• U specifies the depth of each roughing pass.
• R defines the retract distance away from the workpiece between passes.
• P and Q denote the start and end block numbers of the shape profile to be machined.
• F sets the feed rate for the cutting process.

Example

Consider a scenario where we need to rough turn a workpiece with a specific profile. Below is a text diagram and the corresponding G-code:

(Text Diagram)
|<--- Workpiece --->|
____________________
|                  |
|                  |
|                  |
|                  | <- Start of Profile (P)
|                  |
|     _______      |
|    /       \     |
|   /         \    | <- End of Profile (Q)
|  /           \   |
| /             \  |
|/_______________\|

(G-code)
N005 G50 S2000;
N010 T0101;
N015 G96 S150 M03;
N020 G00 X100. Z5. M08;
N025 G71 U2. R1.;
N030 G71 P035 Q080 U0.5 W0.2 F0.15;
N035 G00 X90. Z2.;
N040 G01 Z-40. F0.2;
N045 X70. Z-60. R5.;
N050 X50. Z-80.;
N055 G02 X30. Z-100. R10.;
N060 G01 Z-120.;
N065 G03 X10. Z-140. R5.;
N070 G01 Z-160.;
N075 X30.;
N080 G70 P035 Q080;
N085 G00 X200. Z200. M09;
N090 M30;

In this example, the G71 cycle is programmed to rough turn the profile between N035 and N080. The U and W values leave a finishing allowance for a subsequent finishing pass.