The term “manufacturing” covers a broad spectrum of activities. Metal working industries, process industries like chemical plants, oil refineries, food processing industries, electronic industries making microelectronic components, printed circuit boards, computers and entertainment electronic products etc. are examples of manufacturing industries. Manufacturing involves fabrication, assembly and testing in a majority of situations. However, in process industries operations are of a different nature.
Manufacturing industries can be grouped into four categories:
1. Continuous Process Industries
In this type of industry, the production process generally follows a specific sequence. These industries can be easily automated and computers are widely used for process monitoring, control and optimization. Oil refineries, chemical plants, food processing industries, etc are examples of continuous process industries.
In this type of industry, the production process generally follows a specific sequence. These industries can be easily automated and computers are widely used for process monitoring, control and optimization. Oil refineries, chemical plants, food processing industries, etc are examples of continuous process industries.
2. Mass Production Industries
Industries manufacturing fasteners (nuts, bolts etc.), integrated chips, automobiles, entertainment electronic products, bicycles, bearings etc. which are all mass produced can be classified as mass production industries. Production lines are specially designed and optimized to ensure automatic and cost effective operation. Automation can be either fixed type or flexible.
Industries manufacturing fasteners (nuts, bolts etc.), integrated chips, automobiles, entertainment electronic products, bicycles, bearings etc. which are all mass produced can be classified as mass production industries. Production lines are specially designed and optimized to ensure automatic and cost effective operation. Automation can be either fixed type or flexible.
3. Batch Production (Discrete Manufacturing)
The largest percentage of manufacturing industries can be classified as batch production industries. The distinguishing features of this type of manufacture are the small to medium size of the batch, and varieties of such products to be taken up in a single shop. Due to the variety of components handled, work centres should have broader specifications. Another important fact is that small batch size involves loss of production time associated with product changeover.
The largest percentage of manufacturing industries can be classified as batch production industries. The distinguishing features of this type of manufacture are the small to medium size of the batch, and varieties of such products to be taken up in a single shop. Due to the variety of components handled, work centres should have broader specifications. Another important fact is that small batch size involves loss of production time associated with product changeover.
As mentioned earlier, integration of computer in process industries for production automation, process monitoring and control and optimization is relatively easy. In the case of mass production and batch production computer integration faces a number of problems as there are a large number of support activities which are to be tied together. These are discussed in detail later in this chapter.
Automation of manufacture has been implemented using different techniques since the turn of the 20th Century. Fixed automation is the first type to emerge. Single spindle automatic lathe, multi spindle automatic lathe and transfer lines are examples of fixed automation. Fixed automation using mechanical, electrical, pneumatic and hydraulic systems is widely used in automobile manufacturing. This type of automation has a severe limitation - these are designed for a particular product and any product change will require extensive modifications to the automation system.
The concept of programmable automation was introduced later. These were electrically controlled systems and programs were stored in punched cards and punched tapes. Typical examples of programmable automation are:
i. Electrical programme controlled milling machines
ii. Hydraulically operated Automatic lathes with programmable control drum
iii. Sequencing machines with punched card control /plug board control
Development of digital computers, microelectronics and microprocessors significantly altered the automation scenario during 1950-1990. Machine control systems are now designed around microprocessors and microelectronics is part and parcel of industrial drives and control. The significant advances in miniaturization through integration of large number of components into small integrated chips and the consequent improvement in reliability and performance have increased the popularity of microelectronics. This has resulted in the availability of high performance desktop computing machines as well as file servers which can be used for industrial control with the help of application software packages.