CNC planar arc machining is a core process in manufacturing, used in industries like automotive, aerospaziale, and precision tooling. Mastering how to process CNC plane arcs ensures accurate arc profiles, smooth surface quality, and efficient production. This guide breaks down the entire workflow, key techniques, and practical examples to help you avoid common mistakes.
1. Choose the Right Work Plane First
The first critical step to process CNC plane arcs is selecting the correct work plane—this determines where the tool performs arc interpolation. CNC systems use three standard plane selection commands, each corresponding to a specific coordinate plane.
| Plane Command | Corresponding Plane | Applicazioni tipiche |
| G17 | XY Plane | Machining flat arcs on horizontal surfaces (PER ESEMPIO., circular grooves on a metal plate) |
| G18 | ZX Plane | Arc machining on cylindrical surfaces (PER ESEMPIO., camshaft grooves) |
| G19 | YZ Plane | Vertical arc cutting (PER ESEMPIO., rectangular part corner arcs) |
Esempio: If you need to machine a clockwise arc on a horizontal aluminum plate, start with the G17 command to set the XY plane—this tells the CNC system to focus on the X and Y axes for arc movement.
2. Write Arc Interpolation Commands
After setting the plane, utilizzo arc interpolation commands to define the tool’s direction (clockwise or counterclockwise). Two core commands are used here:
- G02: Clockwise (CW) arc interpolation. Use this when the tool needs to move in a clockwise direction around the arc center.
- G03: Counterclockwise (CCW) arc interpolation. Choose this for counterclockwise tool movement.
All arc commands must include the arc’s end coordinates (X/Y/Z) e velocità di alimentazione (F).
Esempio pratico:
To machine a CW arc in the XY plane (G17) with absolute coordinates (G90), the program segment would look like this:
G17 G02 G90 X100.0 Y50.0 F800
Here:
- X100.0 Y50.0: End coordinates of the arc.
- F800: Velocità di alimentazione (800 mm/min), controlling how fast the tool moves along the arc.
3. Define Arc Dimensions: I/J/K vs. R Parameters
To process CNC plane arcs accurately, you need to define the arc’s size—this is done with either I/J/K parameters (offset from the arc start point to the center) or the R parameter (arc radius).
Differenze chiave & Use Cases
| Parameter Type | Come funziona | Meglio per | Esempio |
| I/J/K | Represents the X (I), Y (J), Z (K) offset from the arc’s start point to its center. | Full circles, 3/4 arcs, or arcs where the center position is known. | If the arc starts at (150, 100) and the center is at (100, 100), the offset is I-50 (X: 100-150 = -50) and J0 (Y: 100-100 = 0). |
| R | Directly specifies the arc’s radius. | Simple arcs (1/4, 1/2) where the radius is known. | A 25mm radius arc: R25.0. |
Critical Note: For full-circle machining, never use the R parameter—since two arcs (large and small) can share the same radius, this causes program errors. Always use I/J/K for full circles.
Full-Circle Example:
Machining a full circle in the XY plane (G17) starting at (50, 0) with center at (0, 0):
G17 G02 G90 X50.0 Y0.0 I-50.0 J0.0 F500
The I-50.0 value means the center is 50mm left of the start point (X-axis), and J0 means no Y-axis offset.
4. Set the Right Feed Rate
IL velocità di alimentazione (F parameter) directly impacts machining quality and efficiency when processing CNC plane arcs. It is usually measured in mm/min (feed distance per minute).
- Per materiali morbidi (alluminio, plastica): Use higher feed rates (600–1200 mm/min) Per ridurre l'usura degli utensili.
- For hard materials (acciaio, titanio): Lower feed rates (300–600 mm/min) to ensure surface smoothness.
A special case: When machining spiral arcs (with a 3rd-axis component), the CNC system automatically calculates the actual tangent velocity—you only need to specify the target tangent speed for the spiral.
5. Optimize Your Program to Avoid Errors
Simplifying your CNC program reduces typos and improves efficiency. Here are two easy tips:
- Omit repeated coordinates: If the arc’s start and end coordinates are the same (PER ESEMPIO., full circles), you can skip writing X/Y values (the system remembers the starting position).
- Omit zero offsets: If I/J/K values are 0 (PER ESEMPIO., J0), leave them out—this shortens the program and lowers error risk.
Optimized Example:
The full-circle program above can be simplified to:
G17 G02 G90 I-50.0 F500 (X/Y and J0 are omitted since they’re redundant).
Yigu Technology’s Perspective on CNC Plane Arc Machining
Alla tecnologia Yigu, we believe precise CNC plane arc machining relies on a mix of correct programming and quality equipment. Many manufacturers struggle with full-circle errors or surface roughness—this often stems from overusing R parameters or ignoring feed rate matching. Our engineering team recommends testing programs with simulation tools first, then fine-tuning I/J/K values and feed rates based on material hardness. We also offer CNC solutions tailored to arc machining, helping users cut setup time by 20% and improve arc accuracy to ±0.01mm.
FAQ
- Q: Can I use the R parameter for 3/4 arcs?
UN: Non è consigliato. 3/4 arcs have similar radius ambiguity to full circles—using I/J/K parameters ensures the CNC system follows the correct path.
- Q: What happens if I forget to set the work plane (G17/G18/G19)?
UN: The CNC system will use the last selected plane (default is often G17). This can lead to arcs being machined in the wrong plane, ruining the part. Always specify the plane at the start of your arc program.
- Q: How do I adjust the feed rate for spiral arcs?
UN: Specify the target tangent velocity (PER ESEMPIO., 100 mm/min) for the spiral— the CNC system automatically calculates the actual feed rate by accounting for the 3rd-axis movement. No manual adjustment of F is needed.
