Welcome to our simple guide on the G98 CNC code. Whether you are new to CNC programming or an experienced machinist, understanding the G98 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
- G98 is a fundamental G-code command that controls the feed rate in CNC machining operations, particularly in canned cycle operations.
- G98 sets the feed rate at the initial Z position, unlike G99 which sets it at the R level, the retract position.
- G98 is used in drilling and tapping operations, returning to the initial Z-depth after each operation, making it suitable for deep hole drilling.
- G98 uses the R-level as a clearance plane, and the feed rate determines how quickly the tool moves through the material.
- Mastering G98 and G99 canned cycles enables efficient CNC programming for drilling and tapping operations, increasing manufacturing safety and reducing manufacturing time.
G98 and G99 Overview
When programming CNC machines, you’ll frequently encounter G98 and G99, two fundamental G-code commands that control the feed rate of your machining operations.
These codes are vital in canned cycle operations, where the machine performs a sequence of actions to machine a specific feature.
The primary difference between G98 and G99 lies in the Z position at which the feed rate is set. With the G98 code, the feed rate is set at the initial Z position, whereas the G99 code sets it at the R level, which is the retract position.
G82 Counterbore Cycle Example
Now that you have a solid grasp of G98 and G99, let’s apply this knowledge to a practical example.
The G82 cycle is a canned cycle for counterboring operations. Imagine you need to counterbore a hole at a specific location on your workpiece.
You can use the G82 cycle to simplify the process. The format for this cycle is G82 X Y Z R P F, where X and Y specify the hole location, Z is the depth of the counterbore, R is the radius of the counterbore, P is the dwell time, and F is the feed rate.
G98 and G99 Functionality
You’ve mastered the G82 counterbore cycle, which is a significant step in simplifying your CNC programming.
Now, it’s time to delve into the G98 and G99 canned cycles, which share similarities with the G82 cycle. These cycles are used for drilling and tapping operations.
The primary difference between G98 and G99 lies in their Z-depth handling:
- G98: The Z-axis returns to the initial Z-depth after each drilling or tapping operation.
- G99: The Z-axis returns to a specified Z-depth, usually the R-level, after each operation.
- Both G98 and G99 use the R-level as a clearance plane.
- You can use G98 and G99 with other G-code commands to customize your CNC program.
Program Explanation and Best Practices
Mastering G98 and G99 canned cycles opens the door to creating efficient CNC programs for drilling and tapping operations.
When writing a program, you’ll typically start with a modal G code, such as G81 for drilling or G84 for tapping. Next, you’ll specify the feed rate, which determines how quickly the tool moves through the material.
For G98, you’ll define the retract height and the dwell time at the bottom of the hole. You can also specify the number of repetitions and the peck drilling depth.
Understanding G Codes and Canned Cycles
You’re likely familiar with G codes, but understanding their nuances is vital for efficient CNC machining.
To master G codes, you need to grasp the basics, including modal G codes that remain in effect until changed or canceled.
Now, let’s examine G98 and G99 codes, which control tool return points after canned cycle operations and significantly impact machining time and safety.
G Code Basics
As you plunge into the world of CNC machining, understanding G codes and canned cycles is pivotal for efficient and precise manufacturing.
G codes are a set of instructions that tell the machine what to do and how to do it.
Fundamentally, the code tells the machine where to move, what speed to use, and what action to perform.
- Positioning: G codes specify the machine’s position in 3D space, allowing for precise movement and placement.
- Using G codes, you can define the toolpath, which determines the machine’s movement and action.
- G codes also regulate the feed rate, which affects the machine’s speed and efficiency.
- Spindle control is another key aspect, as it regulates the machine’s rotational speed and direction.
Modal G Codes
When working with G codes, you’ll often encounter modal G codes that control the behavior of canned cycles.
These codes, such as G98 and G99, determine where the tool ends up following a cycle. In a canned cycle, the R-point is defined in the cycle command line, and the Initial Plane is defined as the last Z position before the canned cycle is called.
The CYCLE command can also be used to specify the return height relative to the cycle control point. By using G98 and G99 correctly, you can control cycle clearance, increasing manufacturing safety and reducing overall manufacturing time.
Proper use of these modal G codes is essential for efficient and safe CNC milling operations.
G98 and G99
In conjunction with canned cycles, G98 and G99 modal G codes play a crucial role in determining the tool’s retraction point.
When you program a CNC machine, you need to specify whether the tool should retract to the initial Z word position or the R point (a predetermined level above the workpiece).
- G98 specifies that the tool retracts to the initial Z word position after each cycle.
- G99 specifies that the tool retracts to the R point after each cycle.
- You can use G98 or G99 in combination with canned cycles like G81 (drilling) or G83 (peck drilling).
- By understanding how G98 and G99 work, you can optimize your CNC machine’s performance and guarantee accurate results.
Configuring CAM-POST and RETURN Parameters
You’ll need to configure the CYCLE parameters tab in the CAM-POST QUEST Developer module to set the RETURN parameter, which affects the cycle and specifies the return height relative to the cycle control point.
This is vital as it determines how the machine will behave during the cycle. When configuring CAM-POST, verify the post-processor understands that G98 and G99 codes are available on the machine.
The RETURN parameter can be set to a specific value, ON, OFF, or AUTO. If not specified, G99 code is output, returning the tool to the R-point level. If specified without a value, G98 code is output, returning the tool to the initial level.
Benefits of G98 and G99 in CNC Milling
Two G-code commands, G98 and G99, play a crucial role in CNC milling, offering significant benefits that improve the machining process.
When you use these commands, you can expect improvements in your machining operations.
- Improved precision: G98 allows for X incremental movements, ensuring precise control over your machining process.
- Canned cycle cancellation: With G98, you can cancel canned cycles, giving you more flexibility in your machining operations.
- Efficient tool movement: G99 returns to the initial Z-axis position, reducing unnecessary tool movement and increasing efficiency.
- Enhanced productivity: By optimizing your machining process with G98 and G99, you’ll experience increased productivity and reduced production time.
CNC Codes Similar to G98
|
Code
|
Mode
|
|---|---|
| G00 | Rapid Positioning |
| G01 | Linear Interpolation |
| G02 | Circular Interpolation (Clockwise) |
| G03 | Counterclockwise Circular Interpolation |
| G04 | Dwell |
| G09 | Exact Stop |
| G10 | Setting Tool and Work Offsets |
| G11 | Programmable data input cancel |
| G17 | XY Plane Selection |
| G18 | Circular Interpolation in XZ Plane |
| G19 | Selects YZ plane for machining operations |
| G27 | Reference point return check |
| G28 | Return to Home Position via Reference Point |
| G29 | Return from reference position |
| G30 | Return to second reference position |
| G33 | Thread cutting, constant lead |
| G40 | Cancel cutter compensation |
| G41 | Cutter Compensation Left |
| G42 | Tool Radius Compensation Right |
| G43 | Tool Length Compensation |
| G44 | Negative Tool Length Compensation |
| G49 | Tool Length Compensation Cancel |
| G50 | Limit Spindle Speed |
| G51 | Scaling/Mirroring Function |
| G52 | Temporary Local Coordinate System Offset |
| G53 | Move In Absolute Machine Coordinates |
| G54 | Work Offset Selection |
| G55 | Work Coordinate System (WCS) |
| G56 | Work Coordinate System 3 Select |
| G57 | Seventh Work Coordinate System |
| G58 | Selects work coordinate system 5 |
| G59 | Work Offset |
| G61 | Exact Stop Mode |
| G64 | Path Blending / Constant Velocity Mode |
| G65 | Macro Call |
| G66 | Modal Macro Call |
| G67 | Cancel modal macro call |
| G68 | Coordinate System Rotation |
| G69 | Coordinate System Rotation Cancel |
| G73 | Peck Drilling |
| G74 | Left-hand Tapping Cycle |
| G76 | Threading Cycle |
| G80 | Cancel Canned Cycle |
| G81 | Drilling Cycle |
| G82 | Drilling Cycle with Dwell |
| G83 | Peck Drilling Cycle |
| G84 | Tapping Cycle |
| G85 | Boring Cycle |
| G86 | Boring Cycle |
| G87 | Boring cycle with a special tool for expanding diameter of hole |
Quick Navigation