What is Computer Aided Manufacturing (CAM)

What is Computer Aided Manufacturing (CAM)

The core of CAM (computer Aided Manufacturing) is computer numerical control (CNC for short), which is a process or system that applies computers to the manufacturing process. In 1952, the Massachusetts Institute of Technology in the United States first developed a CNC milling machine. The characteristic of CNC is that the machine tool is controlled by program instructions encoded on punched paper tape. Since then, a series of CNC machine tools have been developed, including multifunctional machine tools called "machining centers", which can automatically change tools from the tool library and automatically change working positions, and can continuously complete multiple processes such as sharpening, drilling, dumpling, and tapping. These are all controlled by program instructions. As long as the program instructions are changed, the processing process can be changed. This processing flexibility of CNC is called "flexibility". The compilation of processing programs not only requires a lot of manpower, but is also prone to errors. The earliest CAM is computer-aided processing parts programming. In 1950, MIT researched and developed APT, a programming language for processing parts of CNC machine tools. It is a high-level language similar to FORTRAN. The statements such as geometric definition and tool movement are enhanced, and the application of APT makes it simple to write programs. This kind of computer-aided programming is batch processing.

CAM systems generally have two functions: data conversion and process automation. The scope of CAM includes computer numerical control and computer-aided process design.

In addition to its application in machine tools, CNC is also widely used in the control of various other equipment, such as punching machines, flame or plasma arc cutting, laser beam processing, automatic plotters, welding machines, assembly machines, inspection machines, automatic knitting machines, computer embroidery and clothing cutting, etc., becoming the basis of CAM in various corresponding industries.

Computer-aided manufacturing system is a multi-faceted work that controls and manages the manufacturing process through a computer hierarchy. Its goal is to develop an integrated information network to monitor a wide range of interrelated manufacturing operations and control each operation according to an overall management strategy.

From the perspective of automation, CNC machine tool processing is a process of automated process, the machining center is to realize the automation of part or all of the mechanical processing process of parts, computer direct control and flexible manufacturing system are to complete the automated processing process of a family of parts or different families of parts, and computer-aided manufacturing is a general concept of computers entering the manufacturing process.

A large-scale computer-aided manufacturing system is a hierarchical computer network consisting of two or three levels of computers. The central computer controls the overall situation and provides processed information. The main computer manages a certain aspect of the work and issues instructions and monitors the subordinate computer workstations or microcomputers. The computer workstations or microcomputers are responsible for a single process control process or management work.

The composition of the computer-aided manufacturing system can be divided into two aspects: hardware and software. The hardware includes CNC machine tools, machining centers, conveying devices, loading and unloading devices, storage devices, testing devices, computers, etc. The software includes databases, computer-aided process design, computer-aided CNC programming, computer-aided tooling design, computer-aided job planning and scheduling, computer-aided quality control, etc.

So far, Computer Aided Manufacturing (CAM) has two concepts: narrow and broad. The narrow concept of CAM refers to all production preparation activities from product design to processing and manufacturing, which includes CAPP, NC programming, calculation of labor quotas, formulation of production plans, formulation of resource demand plans, etc. This is the narrow concept of the original CAM system. Today, the narrow concept of CAM has been further narrowed to a synonym for NC programming. CAPP has been used as a special subsystem, while the calculation of labor quotas, formulation of production plans, and formulation of resource demand plans are assigned to MRPⅡ/ERP systems. The broad concept of CAM includes

The content is much more. In addition to all the contents included in the narrow definition of CAM mentioned above, it also includes the monitoring, control and management of all logistics-related processes (processing, assembly, inspection, storage, and transportation) in manufacturing activities.

CNC system

The CNC system is the control part of the machine tool. It generates CNC machining programs according to the input part drawing information, process and process parameters in a human-machine interactive manner, and then drives the machine tool parts to make corresponding movements through the servo drive system through the number of electrical pulses. Figure 3-4-2 is a functional diagram of the CNC system.

On traditional numerical control (NC) machine tools, the processing information of parts is stored on NC paper tapes, and the information on the NC paper tapes is read by a photoelectric reader to achieve the processing control of the machine tool. Later, it developed into computer numerical control (CNC), and the function was greatly improved. All the information of a processing can be read into the computer memory at one time, thus avoiding the frequent startup of the reader. More advanced CNC machine tools can even remove the photoelectric reader and program directly on the computer, or directly receive information from CAPP to achieve automatic programming. The latter CNC machine tool is the basic equipment of the computer integrated manufacturing system. Modern CNC systems often have the following functions:

(1) Multi-axis linkage control; (2) Tool position compensation; (3) System fault diagnosis; (4) Online programming; (5) Parallel processing and programming; (6) Processing simulation; (7) Tool management and monitoring; (8) Online detection.

Principles of CNC Programming

The so-called NC programming is the process of automatically or manually generating NC codes based on the part geometry information from CAD and the part process information from CAPP. Commonly used NC codes are ISO (International Organization for Standardization) and EIA (Electronic Industries Association of America). The ISO code is a seven-bit complement-even code, that is, the 8th bit is the complement-even bit; while the EIA code is a six-bit complement-odd code, that is, the 5th column is the complement-odd bit. The purpose of complementing even and complementing odd is to facilitate the inspection of the wrong information read by the paper tape reader. The general NC program is composed of program words, and the program words are composed of address codes represented by English letters and numbers and symbols after the address code. Each program represents a special function, such as G00 for point control, G33 for equal pitch thread cutting, M05 for spindle stop, etc. Generally, a CNC machining instruction is composed of several program words, such as N012G00G49X070Y055T21, where N012 indicates the 12th instruction, G00 indicates point control, G49 indicates tool compensation preparation function, X070 and Y055 indicate X and Y coordinate values, and T21 indicates tool number instruction. The meaning of the entire instruction is: fast move to point (70, 55), tool No. 1 takes tool compensation value on dial No. 2.

There are generally four ways of CNC programming:

(1) Manual programming; (2) CNC language programming; (3) CAD/CAM system programming; (4) Automatic programming.