In general, an automated production process can be classiﬁed into one of three groups: ﬁxed, programmable, or ﬂexible.
Fixed automation is typically employed for products with a very high production rate; the high initial cost of a ﬁxed-automation plant can therefore be spread over a very large number of units. Fixed-automation systems are used to manufacture products as diverse as cigarettes and steel nails. The signiﬁcant feature of ﬁxed automation is that the sequence of the manufacturing operations is ﬁxed by the design of the production machinery, and therefore the sequence cannot easily be modiﬁed at a later stage of a product’s life cycle.
The typical features of fixed automation are:
- The high initial investment for custom-engineered equipment.
- High production rates.
- Major variability in product type. A combination of various parts is required in the product mix and products that will be manufactured from the same production system.
- Relatively inflexible in accommodating product changes.
- The life cycles of the products are short.
- Production volumes are moderated, and the claim is not as predictable.
Examples of fixed automation include mechanized assembly and machining transfer lines.
Programmable automation can be considered to exist where the production equipment is designed to allow a range of similar products to be produced. The production sequence is controlled by a stored program, but to achieve a product change-over, considerable reprogramming and tooling changes will be required. In any case, the process machine is a stand-alone item, operating independently of any other machine in the factory; this principle of automation can be found in most manufacturing processes and it leads to islands of automation. The concept of programmable automation has its roots in the Jacquard looms of the nineteenth century, where weaving patterns were stored on a punched-card system.
Some of the features that characterize programmable automation are:
- High investment in general-purpose equipment.
- Low production rates relative to fixed automation.
- Flexibility to deal with changes in product configuration.
- Most suitable for batch production.
Examples of programmed automation include numerically controlled machine tools, PLC, and industrial robots.
Flexible automation is an enhancement of programmable automation in which a computer-based manufacturing system has the capability to change the manufacturing program and the physical conﬁguration of the machine tool or cell with a minimal loss in production time. In many systems, the machining programs are prepared at a location remote from the machine, and they are then transmitted as required over a computer-based local-area communication network.
The features of flexible automation can be summarized as follows:
- High investment for a custom-engineered system.
- Continuous production of variable mixtures of products.
- Medium production rates.
- Flexibility to deal with product design variations.
The essential features that distinguish flexible automation from programmable automation are:
- The capacity to change part programs with no lost production time.
- The capability to change over the physical setup, again with no lost production time.
The development of technologies including artiﬁcial intelligence and the Internet of Things has led to the development of the Industry 4.0 concept, which is widely considered to be the fourth industrial revolution, based on the development of smart factories. Within a smart factory, cyber-physical systems monitor physical processes, which can then be communicated to allow the decision to be made on a decentralized basis.