Differences Between Milling Machines and CNC Milling Machines

 

In the field of mechanical processing, milling machines and CNC milling machines are both commonly used processing equipment, playing vital roles in industrial production. Although both belong to the category of milling machines and are used for milling workpieces, they exhibit significant differences in technical principles, operation methods, processing capabilities, and other aspects. Understanding these differences helps in selecting the appropriate equipment based on specific processing needs, thereby improving production efficiency and machining quality.

A milling machine is a machine tool that achieves material removal through the rotational motion of a milling cutter and the movement of the workpiece. Its basic working principle involves using the circumferential or end cutting edges of the milling cutter to machine flat surfaces, grooves, steps, formed surfaces, and other features on the workpiece. Traditional milling machines mainly rely on mechanical transmission structures, such as gears and lead screw-nut pairs, to achieve feed movements of the worktable along the X, Y, and Z axes. Operators need to manually adjust the position and feed speed of each axis and control the operation in real time by observing the machining process.

CNC milling machines are advanced processing equipment that integrates a numerical control system (CNC) based on traditional milling machines. The CNC system controls the machine’s movements and processing through computer programs. The working principle involves programming machining parameters, tool movement trajectories, and other information into a CNC program, which is then input into the numerical control unit. The CNC unit processes the data and sends command signals to control servo motors, driving the worktable and spindle to achieve precise feed and rotational movements. CNC milling machines can realize multi-axis linkage control (multi-axis linkage control, i.e., simultaneous control of multiple axes) and are capable of machining complex 3D surfaces and high-precision parts.

Operation of milling machines relies heavily on manual labor. Operators must be familiar with the machine’s mechanical structure and operation handles, controlling the worktable’s movement and the spindle’s start/stop and speed changes by manually turning handwheels or flipping switches. During processing, they must continuously observe the workpiece’s machining status and manually adjust parameters such as cutting depth and feed rate to ensure machining quality. This operation mode places high demands on the operator’s skill level and experience, results in relatively low processing efficiency, and makes it difficult to guarantee consistent machining accuracy.

CNC milling machines feature a high degree of automation. Operators only need to input the prepared CNC program into the machine’s CNC system, set tool parameters and the workpiece coordinate system, and start the program; the machine will then automatically complete the machining process according to the predetermined program. During processing, the CNC system continuously monitors the machine’s operating status and machining accuracy, automatically adjusting feed speed and cutting parameters without manual intervention. The operator’s main tasks include program preparation, tool installation, workpiece clamping, and monitoring and managing the machining process. This operation mode significantly reduces labor intensity, improves processing efficiency and accuracy, and minimizes the impact of human factors on machining quality.

Milling machines have relatively limited processing capabilities, mainly suitable for machining simple geometric features such as flat surfaces, grooves, and steps. Due to manual feeding and mechanical transmission, their machining accuracy is greatly affected by factors such as mechanical transmission clearance and operator skill level, typically achieving a precision grade of IT8-IT10 and a surface roughness Ra value of approximately 1.6-6.3μm. They struggle to meet the processing requirements for complex curved surfaces and high-precision parts.

CNC milling machines possess powerful processing capabilities, capable of machining various complex 3D surfaces, mold cavities, box-type parts, and more. Through multi-axis linkage control, they can achieve arbitrary tool trajectory movements in space, completing machining tasks that traditional milling machines cannot handle. Their machining precision depends primarily on the CNC system’s control accuracy, servo motor resolution, and the machine’s mechanical structure precision. Modern CNC milling machines can achieve a precision grade of IT5-IT7, with surface roughness Ra values controllable below 0.8-1.6μm, meeting high-precision machining requirements. Additionally, CNC milling machines feature automatic tool change functions, enabling multiple machining operations to be completed in a single clamping, thus improving processing efficiency and the consistency of part machining accuracy.

Milling machines are suitable for single-piece small-batch production, simple part machining, and teaching/training scenarios. In situations with low precision requirements and simple part shapes, they offer advantages such as easy operation and low cost. For example, in general mechanical processing workshops, milling machines are often used to machine basic flat surfaces and grooves on parts, preparing them for subsequent processing steps.

CNC milling machines are widely used in complex part machining, high-precision processing, and mass production. They are indispensable in industries such as mold manufacturing, aerospace, and automotive parts. They can efficiently machine various complex mold cavities, automotive panel dies, aero-engine blades, and other parts, meeting the high-precision and high-efficiency processing needs of these industries. Meanwhile, CNC milling machines can integrate with computer-aided design (CAD) and computer-aided manufacturing (CAM) software to realize an integrated process from part design to machining, enhancing production automation and intelligence levels.

Milling machines have relatively simple structures, low manufacturing costs, and convenient maintenance. Their main maintenance tasks include lubricating mechanical components, adjusting transmission systems, and replacing tools. Since operation relies on manual labor, the cost of operator skill training is relatively low.

CNC milling machines have higher manufacturing costs due to integrating advanced components such as CNC systems, servo motors, and sensors. Their maintenance requires professional technicians and involves complex tasks such as CNC system fault diagnosis, servo motor debugging, and mechanical component precision calibration. Additionally, the software systems of CNC milling machines need regular updates and maintenance to ensure normal operation. Furthermore, tooling and CNC program preparation also involve certain cost investments.

Milling machines and CNC milling machines differ significantly in definitions/principles, operation methods, processing capabilities, application scopes, and maintenance costs. Milling machines are characterized by simple operation and low cost, suitable for single-piece small-batch processing of simple parts. CNC milling machines, however, offer high automation, high machining precision, and strong processing capabilities, making them ideal for high-precision and mass production of complex parts. In practical production, the selection between a milling machine and a CNC milling machine should be based on specific processing requirements, part precision needs, and production scale to achieve optimal machining results and economic benefits. With continuous technological advancements, CNC milling machines will increasingly expand their application scope and become the mainstream equipment in the mechanical processing field.