CNC (Computer Numerical Control) machining is a high-precision manufacturing process that uses computer programs to control machine tools for automatically cutting metal or plastic parts. Its core advantages lie in high precision, high efficiency, and strong repeatability.
Below is a detailed introduction to the standard execution steps of CNC machining:
Product Design and 3D Modeling (Design & CAD Modeling)
Design three-dimensional part models using professional CAD software (e.g., SolidWorks, AutoCAD, or CATIA);
Define critical dimensions, tolerances, thread specifications, chamfers, and fit requirements;
Export files in standard formats such as .STEP, .IGES, or .DXF;
Incorporate machining allowances during design to ensure process stability.
Objective: Generate engineering-compliant 3D models providing accurate data for programming and process planning.
Process Planning & CAM Programming
Import CAD models into CAM software (e.g., Mastercam, Fusion 360, UG NX);
Select machine tool type (e.g., 3-axis, 4-axis, or 5-axis CNC machine);
Set cutting tools, rotational speed (RPM), feed rate, and cutting depth;
Simulate tool paths to prevent interference or collisions;
Output G-code and M-code—machine-recognizable control instructions.
Objective: Convert design drawings into executable machining programs for precise and efficient processing.
Machine Setup & Workpiece Mounting
Select appropriate tools (milling cutters, drills, taps, etc.) and fixtures (vices, magnetic chucks, jigs, etc.);
Securely mount the workpiece on the worktable to maintain stable positioning;
Calibrate tool length, tool setting points, and establish the workpiece coordinate origin;
Inspect machine status: coolant, lubricant, air pressure, power supply, and safety devices.
Objective: Ensure equipment is in optimal condition to prevent dimensional deviations caused by clamping errors or equipment malfunctions.
Dry Run & Simulation
Perform a dry run to verify toolpaths;
Simulate the machining process using CAM simulation or the machine control system;
Check for program errors, tool collisions, or path boundary violations;
Conduct test cuts on critical machining areas to validate dimensions and surface quality.
Objective: Prevent tool collisions and material waste, ensuring program safety and reliability.
Rough Machining
Rapidly remove excess material from the blank using larger feed rates and cutting depths;
Employ wear-resistant tools (e.g., carbide tools) to enhance efficiency;
Retain a small allowance for subsequent semi-finishing operations;
Monitor tool wear and workpiece temperature changes during machining.
Objective: Quickly establish the part’s general contour, providing a stable foundation for subsequent finishing operations.
Semi-Finishing & Finishing
Adjust cutting parameters and use high-precision tools for dimensional correction;
Focus on machining critical surfaces, mating holes, and high-precision areas;
Perform burr removal and chamfer grinding on part edges near the end of machining;
Control dimensional tolerances within design specifications;
Finishing typically utilizes lower feed rates and smaller cutting depths;
Ensure surface roughness meets design requirements (e.g., Ra ≤ 0.8μm).
Post-CNC machined parts must undergo deburring per ISO 13715 standards:
Functional surface burr height ≤ 0.05mm
Fitting surfaces require C0.3-C0.5mm chamfers
Automated grinding employs 6-axis robots + nylon grinding heads (3000rpm)
Objective: Achieve high dimensional accuracy and smooth surface finish.
Electrical Discharge Machining (EDM)
In CNC machining, EDM is a critical process for handling high-hardness materials (HRC 50+) and complex cavities. It also removes excess material from milled parts to prevent deformation:
Fast wire EDM: Utilizes molybdenum wire electrodes (0.18mm diameter), cutting speed 8-12m/s, accuracy ±0.03mm, suitable for mold rough machining and low-precision parts
Medium wire EDM: Employs multiple-pass cutting technology, achieving accuracy ±0.005mm and surface roughness Ra1.6μm, meeting precision part requirements
Inspection & Quality Control
Post-machining measurements are performed using specialized tools:
Vernier calipers, micrometers, depth gauges (for rapid inspection)
Coordinate Measuring Machine (CMM) (high-precision dimensional inspection)
Surface Roughness Tester (Ra value measurement)
Geometric accuracy checks (perpendicularity, concentricity, flatness, etc.)
Inspection results are documented and archived; process parameters are adjusted promptly if deviations occur.
Objective: Ensure each part meets tolerance requirements and customer standards (e.g., ISO 2768).
Post-processing & Finishing
Manually remove burrs from areas inaccessible to grinding tools and clean workpieces;
Perform necessary surface treatments:
Polishing, sandblasting, anodizing, electroplating, passivation, etc.;
Mark part numbers or laser engrave;
Protectively package to prevent shipping damage.
Objective: Enhance product appearance, corrosion resistance, and functional performance.
Data Feedback & Process Optimization
Store machining parameters, tool life, and inspection data;
Summarize experience to optimize tool paths, fixture designs, or cutting parameters;
Establish a standardized CNC machining database;
Provide repeatable, traceable process solutions for similar parts.
Objective: Achieve continuous improvement, enhance production consistency and efficiency.
Summary
CNC machining is a highly automated precision manufacturing technology where every step—from design modeling to inspection optimization—directly impacts part quality and production efficiency.
Through standardized processes, scientific programming, and rigorous inspection, it achieves high precision, stability, and consistency in production outcomes. If you have CNC-machined components to produce, contact Weldo Machining for the latest quote.
