Computer Integrated Manufacturing, known as CIM, is the phrase used to describe the complete automation of a manufacturing plant, with all processes functioning under computer control and digital information tying them together. It was promoted by machine tool manufacturers in the 1980's and the Society for Manufacturing Engineers (CASA/SME). Quite often it was mistaken for the concept of a "lights out" factory. It includes CAD/CAM, computer-aided design/computer- aided manufacturing, CAPP, computer-aided process planning, CNC, computer numerical control machine tools, DNC, direct numerical control machine tools, FMS, flexible machining systems, ASRS, automated storage and retrieval systems, AGV, automated guided vehicles, use of robotics and automated conveyance, computerized scheduling and production control, and a business system integrated by a common data base.
The heart of computer integrated manufacturing is CAD/CAM. Computer-aided design(CAD) and computer-aided manufacturing(CAM) systems are essential to reducing cycle times in the organization. CAD/CAM is a high technology integrating tool between design and manufacturing. CAD techniques make use of group technology to create similar geometries for quick retrieval. Electronic files replace drawing rooms. CAD/CAM integrated systems provide design/drafting, planning and scheduling, and fabrication capabilities. CAD provides the electronic part images, and CAM provides the facility for toolpath cutters to take on the raw piece.
The computer graphics that CAD provides allows designers to create electronic images which can be portrayed in two dimensions, or as a three dimensional solid component or assembly which can be rotated as it is viewed. Advanced software programs can analyze and test designs before a prototype is made. Finite element analysis programs allow engineers to predict stress points on a part, and the effects of loading.
Once a part has been designed, the graphics can be used to program the tool path to machine the part. When integrated with an NC postprocessor, the NC program that can be used in a CNC machine is produced. The design graphics can also be used to design tools and fixtures, and for inspections by coordinate measuring machines. The more downstream use that is made of CAD, the more time that is saved in the overall process.
Generative process planning is an advanced generation of CAD/CAM. This uses a more powerful software program to develop a process plan based on the part geometry, the number of parts to be made, and information about facilities in the plant. It can select the best tool and fixture, and it can calculate cost and time.
Flexible machining systems (FMS) are extensions of group technology and cellular manufacturing concepts. Using integrated CAD/CAM, parts can be designed and programmed in half the time it would normally take to do the engineering. The part programs can be downloaded to a CNC machining center under the control of an FMS host computer. The FMS host can schedule the CNC and the parts needed to perform the work
Computer integrated manufacturing can include different combinations of the tools listed above.
One of the key issues regarding CIM is equipment incompatibility and difficulty of integration of protocols. Integrating different brand equipment controllers with robots, conveyors and supervisory controllers is a time-consuming task with a lot of pitfalls. Quite often, the large investment and time required for software, hardware, communications, and integration cannot be financially justified easily
Another key issue is data integrity. Machines react clumsily to bad data, and the costs of data upkeep as well as general information systems departmental costs is higher than in a non-CIM facility.
Another issue is the attempt to program extensive logic to produce schedules and optimize part sequence. There is no substitute for the human mind in reacting to a dynamic day-to-day manufacturing schedule and changing priorities.
Just like anything else, computer integrated manufacturing is no panacea, nor should it be embraced as a religion. It is an operational tool that, if implemented properly, will provide a new dimension to competing: quickly introducing new customized high quality products and delivering them with unprecedented lead times, swift decisions, and manufacturing products with high velocity.
It might be more prudent for a company to begin the process of computer integration with CAD/CAM and an integrated business data base. There are many reliable and proven CAD/CAM software packages available, as there are integrated business software systems. Taking small steps instead of a wholesale CIM approach is advisable.