A Complete Guide to CNC Machining

CNC Machining is a manufacturing process in which pre-programmed computer software controls the movement of factory tools and machinery. The process can be used to control a wide range of complex machinery, from grinders and lathes to mills and routers. Three-dimensional cutting work can be performed using CNC machining with a single set of prompts.

The CNC method, which stands for “computer numerical control,” works in opposition to — and thus overcomes — the limitations of manual control, which requires live operators to prompt and direct machining tool commands through levers, buttons, and wheels. A CNC device may appear to the untrained eye to be a standard collection of computer components, but the software programs and consoles used in CNC machining set it apart from all other types of computation.

How Does CNC Machining Work?

When a CNC system is turned on, the required cuts are programmed into software and dictated to corresponding tools and machinery, which, much like a robot, carry out the dimensional tasks as defined.

In CNC programming, the code generator within the numerical system frequently assumes mechanisms are faultless, despite the possibility of errors, which is increased when a CNC machine is directed to cut in more than one direction at the same time. The placement of a tool in a numerical control system is defined by a set of inputs known as the part program.

Punch cards are used to input programs into a numerical control machine. CNC machine programs, on the other hand, are fed to computers via small keyboards. A computer’s memory stores CNC programming. Programmers write and update the code. As a result, CNC systems have a much larger computational power. Best of all, CNC systems are far from static, as new prompts can be introduced to existing programs through revised code.

CNC Machine Programming

Machines are controlled by numerical control in CNC, which uses a software program to control an entity. The language behind CNC machining is known as G-code, and it’s used to control the speed, feed rate, and coordination of a corresponding machine.

In essence, CNC machining allows you to pre-program the speed and location of machine tool functions and run them in repetitive, predictable cycles using software, all with minimal human intervention. The process has been adopted across the manufacturing sector as a result of these capabilities, and is particularly important in the areas of metal and plastic production.

For starters, a 2D or 3D CAD drawing is conceived, which is then translated to computer code for the CNC system to execute. After the program is inputted, the operator gives it a trial run to ensure no mistakes are present in the coding.

Types of CNC Machining Operations

CNC machining is a manufacturing process that can produce a wide range of products such as automobile frames, surgical equipment, airplane engines, gears, and hand and garden tools. It is suitable for a wide range of industries including automotive, aerospace, construction, and agriculture. The process includes a variety of computer-controlled machining operations, such as mechanical, chemical, electrical, and thermal processes, that remove the required material from the workpiece to create custom CNC parts or products. While chemical, electrical, and thermal machining processes will be covered in a later section, this section will look at some of the most common mechanical CNC machining operations, such as:

  • Drilling
  • Milling
  • Turning

CNC Drilling

Drilling is a type of machining that uses multi-point drill bits to create cylindrical holes in a workpiece. In CNC drilling, the CNC machine typically feeds the rotating drill bit perpendicular to the plane of the workpiece’s surface, resulting in vertically aligned holes with diameters equal to the diameter of the drill bit used for the drilling operation. Angular drilling operations, on the other hand, can be carried out with the help of specialized machine configurations and work holding devices. Counterboring, countersinking, reaming, and tapping are all operational capabilities of the drilling process.

CNC Milling

Milling is a machining process that removes material from a workpiece by using rotating multi-point cutting tools. In CNC milling, the workpiece is typically fed to the cutting tool in the same direction as the cutting tool’s rotation, whereas in manual milling, the workpiece is fed in the opposite direction as the cutting tool’s rotation. Face milling—cutting shallow, flat surfaces and flat-bottomed cavities into the workpiece—and peripheral milling—cutting deep cavities into the workpiece, such as slots and threads—are two operational capabilities of the milling process.

CNC Turning

Turning is a machining process that removes material from a rotating workpiece using single-point cutting tools. To produce cylindrical parts with external and internal features such as slots, tapers, and threads, the machine—typically a CNC lathe machine—feeds the cutting tool in a linear motion along the surface of the rotating workpiece, removing material around the circumference until the desired diameter is achieved. Boring, facing, grooving, and thread cutting are all operational capabilities of the turning process. When deciding between a CNC mill and a lathe, milling, with its rotating cutting tools, is superior for more complex parts.

CNC Machining Materials

The CNC machining process is appropriate for a wide range of engineering materials, including:

  • Metal (e.g., aluminum, brass, stainless steel, alloy steel, etc.)
  • Plastic (e.g., PEEK, PTFE, nylon, etc.)
  • Wood
  • Foam
  • Composites

The best material to use in a CNC manufacturing application is largely determined by the specific manufacturing application and its specifications. Most materials can be machined as long as they have enough hardness, tensile strength, shear strength, and chemical and temperature resistance to withstand the machining process.

The optimal cutting speed, cutting feed rate, and depth of cut are determined by the workpiece material and its physical properties. The cutting speed, measured in surface feet per minute, refers to how quickly the machine tool cuts into or removes material from the workpiece. The feed rate, measured in inches per minute, indicates how quickly the workpiece is fed towards the machine tool, and the cut depth indicates how deeply the cutting tool cuts into the workpiece. Typically, the workpiece will go through an initial phase in which it is roughly machined to the approximate, custom-designed shape and dimensions, followed by a finishing phase in which it is subjected to slower feed rates and shallower cut depths to achieve its more precise and accurate specifications.

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