Welcome to our simple guide on the G71 CNC code. Whether you are new to CNC programming or an experienced machinist, understanding the G71 code is essential.
This guide will explain everything you need to know about this unit mode command—what it is, when to use it, and why it matters.
(Step-by-step.)
Key Takeaways
- G71 is a powerful CNC lathe cycle for efficient material removal, defining key parameters like depth of cut, retract value, and finishing allowances.
- The cycle requires a subroutine to define the part’s profile and can be used in either a two-line or single-line format.
- G71 code defines the roughing pass and finish pass, controlling the material removal process and allowing for precise control over the roughing operation.
- The G71 cycle consists of 6 stages, including setting 287, start position, Z-Axis clearance plane, finishing allowance, roughing allowance, and programmed path.
- Finishing allowance is critical in G71, defined by parameters U and W to avoid cutting into the true profile of the part and achieve the desired finish quality.
G71 Roughing Cycle Overview
In CNC lathe operations, the G71 roughing cycle is a powerful canned cycle that enables you to efficiently remove material from a part while controlling the roughing process and defining its key parameters.
This cycle requires a subroutine to define the part’s profile and can be used in either a two-line or single-line format, depending on your specific application.
You can use the G71 code to define the roughing pass and finish pass, controlling the depth of cut, retract value, and finishing allowances in X and Z.
G71 Two-Line Roughing Cycle
When programming a G71 two-line roughing cycle, you’re working with a concise and powerful format that simplifies the material removal process.
This format consists of two lines: G71 U(1) R; and G71 P Q U(2) W F. The first line specifies the depth of cut for each roughing pass (U(1)) and the retract value in X (R).
The second line defines the start and end points of the subroutine (P and Q), the finishing allowances in X and Z (U(2) and W), and the feed rate (F). By setting these values, you control the roughing cycle’s boundaries, material removal, and finishing requirements, allowing you to efficiently remove material and prepare the workpiece for finishing operations.
G71 Program Example
You’ll find the G71 program example particularly useful because it illustrates how to apply the two-line roughing cycle to a specific machining task.
This example demonstrates the use of the G71 code, subroutine definition, and feed rates to machine a 45-degree chamfer at the front of the part. The program utilizes tool nose radius compensation and linear feed rate movement to achieve the desired outcome.
The example consists of a header for roughing, a footer, and a finish allowance of .010 for all axes (X and Z). The DOC is .100, and the feed rate is .008 in this example program.
G71 Single-Line Roughing Cycle
When programming a G71 single-line roughing cycle, you’ll work with a specific set of parameters that define the roughing operation.
The G71 format, G71 P Q D U W I K F, includes values that specify the start and end points, depth of cut, finishing allowances, and feed rate.
G71 Parameters
The G71 single-line roughing cycle is a powerful tool in CNC machining, and understanding its parameters is crucial for effective use. You’ll need to specify the correct values for each parameter to achieve the desired results.
| Parameter | Description | Units |
|---|---|---|
| P | Start point of subroutine | – |
| D | Depth of cut per pass | Positive radius value |
| F | Feed rate | mm/min or in/min |
The D parameter defines the depth of cut for each pass, while the U and W parameters determine the finishing allowances in X and Z. The I and K parameters define the final depth of cut in X and Y, respectively. By setting these parameters correctly, you can achieve efficient and accurate roughing cycles in your CNC machining operations.
Roughing Cycle Format
To program a G71 single-line roughing cycle, specify the necessary parameters in a single line of G-code, following the format G71 P Q D U W I K F.
This format allows you to define the roughing cycle parameters and subroutine profile in a single line. The P and Q values define the start and end points of the subroutine, while D specifies the depth of cut for each pass.
U and W define the finishing allowances in X and Z, and I and K define the final depth of cut in X and Y. Finally, F sets the feed rate.
G70 Finishing Cycle and Subroutine
You’re now going to examine the G70 finishing cycle and subroutine, which is a vital aspect of CNC machining.
This cycle is designed to remove small amounts of material from a workpiece, producing a high-quality finish.
You’ll learn about the G70 code parameters that control this finishing process, ensuring you get the desired surface finish for your part.
Finishing Cycle Overview
Finishing a part’s surface to a high-quality standard requires a deliberate and precise approach, which is where the G70 finishing cycle comes in.
You’ll typically use this cycle after the roughing cycle has removed the majority of the material, and it’s designed to achieve a high-quality surface finish.
The G70 code calls the subroutine defined in the roughing cycle with the same P and Q values, allowing for a seamless transition between the two cycles.
This subroutine defines the profile of the part for the finishing cycle, simplifying the programming process.
On a Lathe, the finishing cycle uses a smaller cutting tool and a slower feed rate than the roughing cycle, guaranteeing a precise cutter path and a smooth surface finish.
G70 Code Parameters
The G70 code parameters are crucial in defining the finishing cycle and subroutine, as they directly impact the quality of the surface finish. You need to comprehend these parameters to achieve the desired results. The G70 code is used in conjunction with the G71 code, which specifies the finishing cycle.
| Parameter | Description |
|---|---|
| P | Specifies the clearance plane for the finish cut |
| Q | Defines the number of finish cuts to be taken |
| F | Feed rate for the finish cut |
| S | Spindle speed for the finish cut |
When programming the G70 code, you need to deliberate these parameters carefully to guarantee a high-quality surface finish. By specifying the correct values, you can achieve a precise finish cut and minimize defects.
G71 O.D./I.D. Stock Removal Cycle
Frequently, CNC programmers rely on the G71 O.D./I.D. Stock Removal Cycle to rough material on a part given the finished part shape.
This canned cycle requires defining the shape of a part by programming the finished tool path and then using the G71 PQ block.
Four key aspects of the G71 O.D./I.D. Stock Removal Cycle are:
- The cycle consists of six stages, including setting, start position, Z-axis clearance plane, finishing allowance, roughing allowance, and programmed path.
- The tool is retracted from the material at a 45-degree angle and then moves in rapid mode to the Z-axis clearance plane during the cycle.
- Finishing allowance and roughing allowance determine the amount of material removal.
- You can use the G71 cycle with a single-line or two-line format, depending on the machine control and programming requirements.
When used in conjunction with the G70 finishing cycle, the G71 O.D./I.D. Stock Removal Cycle can simplify finishing cycle programming and guarantee accurate material removal for both roughing and finishing operations.
G71 Command Parameters
Define the G71 command parameters to effectively control the O.D./I.D. stock removal cycle. These parameters fine-tune the G71 command’s performance, ensuring precise control over the roughing process.
| Parameter | Description |
|---|---|
| D | Depth of cut for each pass of stock removal |
| F | Roughing feedrate in inches (mm) per minute (G98) or per rotation (G99) |
| I | X-axis size and direction of the G71 rough pass allowance (radius value) |
| K | Z-axis size and direction of the G71 rough pass allowance (radius value) |
| P, Q | Starting and ending block numbers of the path to rough (reference the subroutine) |
When setting the G71 command parameters, you’ll need to ponder the X axis, roughing feed, and P value to achieve the desired results. By carefully defining these parameters, you’ll be able to control the O.D./I.D. stock removal cycle with precision.
G71 Stock Removal Cycle
With the G71 command parameters set, you’re now ready to plunge into the G71 stock removal cycle, a powerful canned cycle that enables precise control over the roughing process.
This cycle roughs material on a part given the finished part shape, requiring the definition of the shape of a part by programming the finished tool path and then using the G71 PQ block.
- 6 stages: Setting 287, Start position, Z-Axis clearance plane, Finishing allowance, Roughing allowance, and Programmed path.
- Roughing process: The tool is retracted from the material at a 45-degree angle and then moves in rapid mode to the Z-axis clearance plane.
- Finishing allowance: Parameters U and W define the X-axis and Z-axis finish allowances to avoid cutting into the true profile of the part.
- Internal and external roughing: The G71 cycle can be used for both internal and external roughing examples, with finish passes defined using the same PQ block geometry.
G71 Address Relationships
When programming the G71 stock removal cycle, you need to understand the address relationships that govern the roughing process.
There are two types of G71 address relationships: Type I and Type II. In Type I, the X-axis tool path doesn’t reverse during a cut, and each roughing pass X-axis location is determined by applying the value specified in I to the current X location.
In Type II, the X-axis tool path can reverse direction, and the X-axis path mustn’t exceed the original starting location, except for the ending block. The I address in G71 specifies the X-axis size and direction of the rough pass allowance, which affects the address relationships.
You’ll choose between Type I and Type II depending on the specific machining operation and desired finish quality.
CNC Codes Similar to G71
|
Code
|
Mode
|
|---|---|
| G72 | Facing Cycle |
| G73 | High Speed Peck Drilling |
| G74 | Peck Drilling Cycle |
| G75 | Grooving Cycle |
| G76 | Threading Cycle |
| G77 | Canned Cycle for Turning |
| G78 | Multiple threading cycle |
| G79 | Face Cutting Cycle |
Quick Navigation