- Continous process
- Batch production
- Individual products production
A continous process is one in which raw materials enter one end of the system and the finished product comes out the other end of the system : the process itself runs continously. Once the process commences, it is continous for a relatively long period of time. The time period may be measured in minutes, days, or even months, depending upon the process. In batch processing, there is no flow of product material from one section of the process to another. Instead, a set amount of each of the inputs to the process is received in a batch, and then some operations is performed on the batch to produce a finished product or an intermediate product that needs further processing. The process is carried out, the finished product is stored, and another batch of product is produced. Each batch of product may be different. Some processes combine the features of the batch and continous types. In such processes, several product materials are treated and stored in batch operation. Then these stored materials are drawn off as required into a continous process. Many chemically based products are manufactured by using batch processes. Two ingrediets are added together, mixed, heated, a third ingredient is added, processed, and then stored. Each batch made may have differing characteristics by design.
The individual product production process is the most common of all processing of all processing systems. With this manufacturing process, a series of operations produces a useful output product. The item being produced may be required to be bent, drilled, welded, and so on, at different steps in the process. The workpiece is normally a discrete part that must be handled on an individual basis. In the modern automated industrial plant, the operator merely sets up the operation and initiates a start, and the operations of the machine are accomplished automatically. These automatic machines and processes were developed to mass-produce products, control very complex operations, or to operate machines accurately for long periods of time. They replaced much human decision, intervention, and observation.
Machines were originally mechanically controlled, they were electromechanically controlled, and today they are often controlled by purely electrical or electronic means through programmable logic controllers (PLCs) or computers. The control of machines or processes can be divided into the folllowing categories :
- Electromechanical control
- Hardwired electronic control
- Programmable hardwire electronic control
- Programmable logic control (PLC)
- Computer control
Source :
Petruzella, Frank. (1995). Industrial Electronics. Mc Graw Hill.304-305
