CNC

CNC Basics - What is CNC?

Computer-Controlled Manufacturing

Computer-controlled manufacturing uses digital instructions to control equipment that produces, modifies, or inspects physical components.These instructions may control the movement of a cutting tool, the deposition of material, the path of a laser, or the operation of an automated production process.Computer-controlled manufacturing connects digital design to physical production. It enables repeatable processes, complex geometries, and automation across a wide range of materials and industries.

Computer Numerical Control (CNC) is one category of computer-controlled manufacturing. Other examples include 3D printing, laser cutting, and automated inspection.

CNC manufacturing can have confusing terms, go see CNC nomenclature if there a word you don't quite understand.

How Does It Work?

Most computer-controlled manufacturing processes follow a similar workflow.

1. Design: A component is designed using Computer-Aided Design (CAD) software or another suitable digital design tool.
2. Process planning: A manufacturing method is selected based on the part geometry, material, accuracy requirements, and production volume.
3. Manufacturing preparation: Software converts the design into instructions appropriate for the selected process. These may define toolpaths, cutting parameters, print layers, or laser movements. These instructions are called G-code.
4. Simulation and verification: Where supported, the planned process is checked for errors, collisions, or other potential problems.
5. Setup: The material is prepared, the workpiece or build area is established, and the required equipment settings are configured.
6. Production: The equipment executes the programmed instructions to manufacture the component.
7. Post-processing and inspection: The part may require support removal, finishing, heat treatment, cleaning, or dimensional inspection.

The exact workflow depends on the manufacturing method. For example, CNC milling generally removes material from a solid workpiece, while 3D printing builds a component by adding material.

Common Types of CNC Manufacturing

Subtractive Manufacturing

Subtractive manufacturing produces a component by removing material from a larger piece of stock.

• CNC milling: Uses a rotating cutting tool to produce pockets, slots, holes, and flat or contoured surfaces.
• CNC turning: Removes material from a rotating workpiece to produce cylindrical features such as shafts and bushings.
• CNC grinding: Uses an abrasive process to achieve specific dimensional and surface-finish requirements.
• CNC routing: Machines materials such as wood, plastics, composites, and suitable metals using programmed cutting paths.

Typical applications: Precision components, brackets, shafts, housings, fixtures, and mechanical assemblies.

Additive Manufacturing

Additive manufacturing produces components by adding material according to a digital model, typically in successive layers. 3D printing is the most familiar example of additive manufacturing.

Common methods include:

• Fused Filament Fabrication (FFF/FDM): Melts and deposits thermoplastic filament to build a component layer by layer.
• Resin printing (SLA/MSLA): Uses light to selectively cure liquid photopolymer resin.
• Powder Bed Fusion: Uses a heat source, such as a laser, to fuse selected regions of a powder bed. Depending on the process, it can manufacture metal or polymer components.
• Material Jetting: Deposits droplets of material that are subsequently solidified or cured.

Typical applications: Prototypes, custom housings, jigs and fixtures, complex internal geometries, lightweight structures, and low-volume production.

Key consideration: Additive manufacturing can produce shapes that are difficult to machine, but parts may require support structures, post-processing, and careful consideration of material properties and build orientation.

Computer-Controlled Cutting

These processes separate material along programmed paths without relying on conventional milling or turning.

• Laser cutting: Uses a focused laser to cut suitable sheet materials.
• Waterjet cutting: Uses a high-pressure water jet, sometimes mixed with abrasive particles, to cut a wide range of materials.
• Plasma cutting: Uses a high-temperature plasma jet to cut electrically conductive materials, particularly metals.

Typical applications: Sheet-metal parts, flat brackets, panels, plate components, and cut profiles for fabrication.

Key consideration: These processes are particularly useful for producing two-dimensional profiles from sheet or plate stock. Their suitability depends on material thickness, edge quality, dimensional requirements, and the geometry required.

Electrical Discharge Machining (EDM)

EDM removes electrically conductive material through controlled electrical discharges.

Common forms include wire EDM, which cuts profiles using a continuously moving wire electrode, and sinker EDM, which produces cavities using a shaped electrode.

Typical applications: Intricate profiles, precision tooling, moulds, and features in electrically conductive materials that are difficult to machine using conventional cutting tools.

Key consideration: EDM is not a general-purpose process for every material. It requires electrically conductive workpieces and is often selected for specific geometry or precision requirements.

Computer-Controlled Inspection

Digital manufacturing also includes equipment used to measure and verify components.

• Coordinate Measuring Machines (CMMs): Measure geometric features using a probe and a defined coordinate system.
• Optical inspection systems: Use cameras or optical sensors to measure features without necessarily contacting the component.
• 3D scanning: Captures surface geometry to create a digital representation that can be compared with a CAD model.

Typical applications: Quality control, dimensional verification, reverse engineering, and checking manufactured parts against design requirements.