CNC machining process: G-code writing examples for aluminum alloy 3D parts and plastic molds

🧭 1. Initial Preparation Stage

1. Design Drawings (CAD)

Use CAD software (e.g., AutoCAD, SolidWorks, Fusion 360) to create 2D or 3D part drawings.
The drawings should clearly indicate dimensions, tolerances, materials, and other technical details.

2. Process Planning and Analysis

Determine the machining sequence (e.g., roughing → semi-finishing → finishing).
Select appropriate machining equipment (e.g., CNC lathe, milling machine, machining center).
Choose suitable tools, fixtures, and coolants based on the material and design requirements.

🧮 2. Programming Stage

3. CAM Programming (Computer-Aided Manufacturing)

Use CAM software (e.g., Mastercam, UG NX, Fusion 360) to generate toolpaths based on the CAD model.
Set machining parameters such as spindle speed, feed rate, and depth of cut.
Generate CNC machining code (G-code / NC code).

4. Simulation and Verification

Perform virtual simulation using CAM software or directly on the CNC machine.
Check for potential issues such as tool collisions, overcuts, and interference problems.

🏗️ 3. Machine Setup Stage

5. Equipment Setup and Calibration

Install tools and apply tool length and radius offsets.
Mount fixtures and securely clamp the workpiece.
Set up the work coordinate system (e.g., G54, G55, etc.).
Transfer the NC program to the CNC controller.

🛠️ 4. Actual Machining Stage

6. Machining Operation

Perform a dry run or trial cut to verify the program is correct.
Start the actual machining process under operator supervision.
Monitor for tool wear, coolant flow, abnormal sounds, and any unexpected behavior during cutting.

🔍 5. Inspection and Post-Processing Stage

7. Quality Inspection

Use measuring instruments (e.g., calipers, coordinate measuring machines) to check part dimensions, tolerances, and geometric accuracy.
Confirm that all critical dimensions meet specifications.

8. Surface and Post-Processing (As Required)

Processes may include deburring, grinding, sandblasting, anodizing, electroplating, etc.

9. Cleaning, Packaging, and Shipping

Clean the finished parts to remove cutting fluids and burrs.
Package, label, and ship according to customer requirements.

✅ Simplified CNC Machining Workflow Diagram:

mathematica複製編輯Design Drawing → Process Planning → Program Generation → Machine Setup → Trial Run & Verification → Machining → Quality Check → Surface Treatment → Shipping




✳️ 1. G-code Examples and Explanation
G-code (also known as numerical control code) is the programming language used by CNC machines to execute machining operations. Common commands include:

Command	Function Description
G00	Rapid movement (non-cutting)
G01	Linear interpolation (cutting move)
G02	Clockwise arc interpolation
G03	Counterclockwise arc interpolation
G17/G18/G19	Select working plane (XY/XZ/YZ)
G90	Absolute coordinate system (commonly used)
G91	Incremental coordinate system
M03	Spindle clockwise rotation
M05	Spindle stop
M06	Tool change
M30	End of program and reset

✅ Simple G-code Example (Milling a 50x50 mm square):
gcode
複製
編輯
G90 G17 G21         ; Absolute programming, XY plane, units in mm
G00 X0 Y0           ; Rapid move to start point
M06 T1              ; Load tool #1
M03 S1200           ; Spindle on CW at 1200 rpm
G01 Z-2.0 F100      ; Plunge into material 2mm deep at 100 mm/min
G01 X50 Y0 F300     ; Cut along X-axis 50 mm
G01 X50 Y50         ; Cut along Y-axis 50 mm
G01 X0 Y50          ; Cut back along X-axis
G01 X0 Y0           ; Return to start point to complete square
G00 Z10             ; Retract to safe height
M05                 ; Stop spindle
M30                 ; End of program
📌 Note: This is a basic example. Actual programs must be adapted to part design and machine specifications.

🔧 2. Tool Types and Their Uses
Different machining operations require different types of cutting tools. Below are common CNC tools:

Tool Name	Appearance	Application	Features
End Mill	Cylindrical	Surface, slot, contour milling	Can cut side and bottom surfaces; common
Ball Nose End Mill	Hemispherical tip	Surface finishing, 3D models	Smooth finish, high precision
Bull Nose Mill	Rounded corner	Semi-finishing 3D surfaces	Stronger than ball nose, ideal for roughing
Drill Bit	Tapered point	Hole drilling	For standard hole-making
Boring Tool	Single-point tool	Precision internal boring	Improves hole diameter and finish
Thread Mill	Thread-shaped flutes	Thread hole machining	High precision, usable for blind holes
Chamfer Mill	Angled edges	Chamfering and deburring	Ideal for edge finishing

🧠 3. Machining Strategies (Cutting Methods and Sequences)
A well-planned machining strategy enhances both efficiency and quality. Below are standard strategies:

1. Machining Sequence Planning
Step	Machining Type	Description
1	Roughing	Remove large material volume, basic shape
2	Semi-finishing	Refine geometry, improve dimensional accuracy
3	Finishing	Final dimensions and surface roughness
4	Surface Treatment	Deburring, chamfering, coating, etc.

2. Cutting Strategy Types
Strategy Type	Description	Best Used For
Z-level machining	Layered cuts along Z-axis	3D surface machining, commonly in mold making
Contour machining	Moves along outer profiles	2D profiles, part outlines
Rest machining	Targets small areas missed by larger tools	Used in finishing stages
Facing	Flattens the material surface	Initial operation, creates reference surface
Helical ramping	Spiral entry to reduce tool stress	Deep holes, hard materials
Adaptive clearing	Constant-load intelligent pathing	Common in CAM, increases tool life

🔚 Summary
Topic	Key Concepts
G-code	Programming language for CNC; must be precise and verified
Cutting Tools	Tool choice affects machining precision, surface finish, and efficiency
Machining Strategy	Core to balancing speed and quality; structured in progressive stages

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