Exercise 5.10 Discussion Point

Think about some automated system and the way it operates. Talk over its advantages and disadvantages with the group.

Unit 6

Programmable Automation

Pre-reading Task

Scan the text for answering the following questions:

1. Examples of programmable automa­tion include numerically controlled machine tools, industrial robots, and programmable logic controllers, do not they?

2. For programmable automation, is the equipment designed in such a way that the sequence of production operations is controlled by a program or by a man?

Text

For programmable automation, the equipment is designed in such a way that the sequence of production operations is controlled by a program, i.e., a set of coded instructions that can be read and interpreted by the system. Thus the operation sequence can be readily changed to permit different product configurations to be produced on the same equipment. Some of the features that characterize programmable automation include high investment in general-purpose programmable equipment, lower production rates than fixed automation, flexi­bility to deal with changes in product configuration, and suited to low and/or medium production of similar products or parts (e.g., part families). Examples of programmable automa­tion include numerically controlled machine tools, industrial robots, and programmable logic controllers.

Programmable production systems are often used to produce parts or products in batches. They are especially appropriate when repeat orders for batches of the same product are ex­pected. To produce each batch of a new product, the system must be programmed with the set of machine instructions that correspond to that product. The physical setup of the equipment must also be changed: special fixtures must be attached to the machine, and the appropriate tools must be loaded. This changeover procedure can be time-consuming. As a result, the usual production cycle for a given batch includes (1) a period during which the setup and reprogramming is accomplished and (2) a period in which the batch is processed. The setup-reprogramming period constitutes nonproductive time of the automated system.

The economics of programmable automation require that as the setup-reprogramming time increases, the production batch size must be made larger so as to spread the cost of lost production time over a larger number of units. Conversely, if setup and reprogramming time can be reduced to zero, the batch size can be reduced to one. This is the theoretical basis for flexible automation, an extension of programmable automation. A flexible automated system is one that is capable of producing a variety of products (or parts) with minimal lost time for changeovers from one product to the next. The time to reprogram the system and alter the physical setup is minimal and results in virtually no lost production time. Consequently, the system is capable of producing various combinations and schedules of products in a continuous flow, rather than batch production with interruptions between batches. The features of flexible automation are (1) high investment for a custom-engineered system, (2) continuous production of mixtures of products, (3) ability to change product mix to accommodate changes in demand rates for the different products made, (4) medium production rates, and (5) flexibility to deal with product design variations.

Flexible automated production systems operate in practice by one or more of the following approaches: (1) using part family concepts, by which the parts made on the system are limited in variety; (2) reprogramming the system in advance and/or off-line, so that reprogramming does not interrupt production; (3) downloading existing programs to the system to produce previously made parts for which programs are already prepared; (4) using quick-change fixtures so that physical setup time is minimized; (5) using a family of fixtures that have been designed for a limited number of part styles; and (6) equipping the system with a large number of quick-change tools that include the variety of processing operations needed to produce the part family. For these approaches to be successful, the variation in the part styles produced on a flexible automated production system is usually more limited than a batch-type programmable automation system. Examples of flexible automation are the flexible manufacturing systems for performing machining operations that date back to the late 1960s.

Post-Text Exercises

Exercise 6.1 Read and Translate the Text into Ukrainian

Exercise 6.2 Comprehension Check

Answer the following questions:

1. How is the equipment designed for programmable automation?

2. Can the operation sequence be changed? What is the purpose of this?

3. What do some of the features that characterize programmable automation include?