I. CNC Milling Machine
A CNC milling machine is also known as a Computer Numerical Control (CNC) milling machine. In English, it means a milling machine controlled by electronic digital signals.
CNC milling machines are automated machining equipment developed from general milling machines. The machining processes are basically the same, and their structures are also somewhat similar. CNC milling machines are divided into two main categories: those without a tool magazine and those with a tool magazine. CNC milling machines with a tool magazine are also known as machining centers.
CNC milling machines are powerful CNC machine tools. The rapidly developing machining centers and flexible machining units are all based on CNC milling machines and CNC boring machines, both of which rely on milling. Because CNC milling is the most complex process and requires solving the most technical problems, milling has always been a key focus in the research and development of CNC systems and automatic programming languages.
The machined surfaces of a milling machine are generally composed of straight lines, arcs, or other curves. According to the requirements of the drawing, the operator of a conventional milling machine continuously changes the relative position between the cutting tool and the workpiece, and then coordinates this with the selected milling cutter speed to allow the tool to cut the workpiece, thus producing workpieces of various shapes.
CNC machining involves dividing the motion coordinates of the tool and workpiece into the smallest unit quantities, i.e., the minimum displacement. The CNC system, according to the requirements of the workpiece program, moves each coordinate by several minimum displacements, thereby achieving the relative movement between the tool and the workpiece to complete the machining of the part.
II. Main differences between CNC milling machines and conventional milling machines
(a) Different natures
1. CNC milling machine: This is an automated machining equipment developed from a general milling machine. The machining processes are basically the same, and their structures are also somewhat similar. CNC milling machines are divided into two main categories: those without a tool magazine and those with a tool magazine. CNC milling machines with a tool magazine are also called machining centers.
2. Ordinary milling machine: A machine tool that uses a milling cutter to process multiple surfaces of a workpiece.
(II) Different Application Characteristics
1. CNC Milling Machines: With the rapid development of social production and science and technology, mechanical products are becoming increasingly precise and complex, and the demand is frequently changing. This is especially true for mechanical parts required in fields such as aerospace, shipbuilding, and the military, which have high precision requirements, complex shapes, and small batch sizes. Processing these products requires frequent modification or adjustment of equipment, and ordinary machine tools or highly specialized automated machine tools can no longer meet these requirements.
To address the aforementioned problems, a new type of machine tool—the CNC machine tool—has emerged. This new machine tool boasts advantages such as strong adaptability, high machining accuracy, stable machining quality, and high production efficiency. It integrates technological achievements from various fields, including electronic computers, automatic control, servo drives, precision measurement, and novel mechanical structures, and represents the future development direction of CNC machine tools.
2. Ordinary milling machine: It has strong adaptability and flexibility in part processing. It can process parts with particularly complex contours or difficult-to-control dimensions, such as mold parts, shell parts, etc. It can process parts that ordinary machine tools cannot process or are very difficult to process, such as complex curved parts described by mathematical models and three-dimensional curved surface parts.
(III) Differences between CNC milling machines and conventional milling machines in machining
1. CNC milling machines generally have a CRT screen display function, showing the machining program, various process parameters, machining time, tool movement trajectory, and workpiece graphics. CNC milling machines also generally have an automatic alarm display function, which can quickly locate machine faults based on alarm signals or alarm prompts. Ordinary milling machines do not have the above functions.
2. CNC milling machines use DC or AC continuously variable servo motors for the main drive and feed drive. They generally lack a spindle gearbox and feed gearbox, resulting in a short transmission chain. In contrast, conventional milling machines typically use three-phase AC asynchronous motors for the main drive and feed drive, with a gearbox providing multi-stage speed changes to meet process requirements, resulting in a longer machine tool transmission chain.
3. CNC milling machines generally have a workpiece measurement system, so manual measurement of workpiece dimensions is usually not required during the machining process. In contrast, conventional milling machines require continuous manual measurement during the machining process to ensure the machining accuracy of the workpiece.
4. The most significant difference between CNC milling machines and ordinary milling machines is that when the object (workpiece) changes, CNC milling machines only need to change the machining program (application software) and do not require major adjustments to the machine tool to process various different workpieces.
