Types of Automation Systems
Automation systems can be categorized based on the flexibility and level of integration in manufacturing process operations. Various automation systems can be classified as follows
Fixed Automation:
It is used in high volume production with dedicated equipment, which has a fixed set of operation and designed to be efficient for this set. Continuous flow and Discrete Mass Production systems use this automation. e.g. Distillation Process, Conveyors, Paint Shops, Transfer lines etc. A process using mechanized machinery to perform fixed and repetitive operations in order to produce a high volume of similar parts.
Programmable Automation:
It is used for a changeable sequence of operation and configuration of the machines using electronic controls. However, non-trivial programming effort may be needed to reprogram the machine or sequence of operations. Investment on programmable equipment is less, as production process is not changed frequently. It is typically used in Batch process where job variety is low and product volume is medium to high, and sometimes in mass production also. e.g. in Steel Rolling Mills, Paper Mills etc.
Flexible Automation:
It is used in Flexible Manufacturing Systems (FMS) which is invariably computer controlled. Human operators give high-level commands in the form of codes entered into computer identifying product and its location in the sequence and the lower level changes are done automatically. Each production machine receives settings/instructions from computer. These automatically loads/unloads required tools and carries out their processing instructions. After processing, products are automatically transferred to next machine. It is typically used in job shops and batch processes where product varieties are high and job volumes are medium to low. Such systems typically use Multipurpose CNC machines, Automated Guided Vehicles (AGV) etc.
Integrated Automation:
It denotes complete automation of a manufacturing plant, with all processes functioning under computer control and under coordination through digital information processing. It includes technologies such as computer-aided design and manufacturing, computer-aided process planning, computer numerical control machine tools, flexible machining systems, automated storage and retrieval systems, automated material handling systems such as robots and automated cranes and conveyors, computerized scheduling and production control. It may also integrate a business system through a common database. In other words, it symbolizes full integration of process and management operations using information and communication technologies. Typical examples of such technologies are seen in Advanced Process Automation Systems and Computer Integrated Manufacturing (CIM)
As can be seen from above, from Fixed Automation to CIM the scope and complexity of automation systems are increasing. Degree of automation necessary for an individual manufacturing facility depends on manufacturing and assembly specifications, labor conditions and competitive pressure, labor cost and work requirements. One must remember that the investment on automation must be justified by the consequent increase in profitability. To exemplify, the appropriate contexts for Fixed and Flexible Automation are compared and contrasted.
Fixed automation is appropriate in the following circumstances.
A. Low variability in product type as also in size, shape, part count and material
B. Predictable and stable demand for 2- to 5-year time period, so that manufacturing capacity requirement is also stable
C. High production volume desired per unit time
D. Significant cost pressures due to competitive market conditions. So, automation systems should be tuned to perform optimally for the particular product.
Flexible automation, on the other hand is used in the following situations.
A. Significant variability in product type. Product mix requires a combination of different parts and products to be manufactured from the same production system
B. Product life cycles are short. Frequent upgradation and design modifications alter production requirements
C. Production volumes are moderate, and demand is not as predictable
Point to Ponder: 9
A. During a technical visit to an industry how can you identify the type of automation prevailing there from among the above types?
B. For what kind of a factory would you recommend computer integrated manufacturing and why?
C. What kind of automation would you recommend for manufacturing
a. Light bulbs
b. Garments
c. Textile
d. Cement
e. Printing
f. Pharmaceuticals
g. Toys
Lesson Summary
In this lesson we have dealt with the following topics:
A. Definition of Automation and its relations with fields of Automatic Control and Information Technology: It is seen that both control and IT are used in automation systems to realize one or more of its functionalities. Also, while Control Technology is used for operation of the individual machines and equipment, IT is used for coordination, management and optimized operation of overall plants.
B. The role played by Automation in realizing the basic goal of profitability of a manufacturing industry: It is seen that Automation can increase profitability in multiple ways by reducing labour, material and energy requirements, by improving quality as well as productivity. It is also seen that Automation is not only essential to achieve Economy of Scale, but also for Economy of Scope.
C. Types of Factories and Automation Systems that are appropriate for them: Factories have been classified into four major categories based on the product volumes and product variety. Similarly, Automation Systems are also categorized into four types and their appropriateness for the various categories of factories explained.
Exercises
A. Describe the role of Industrial Automation in ensuring overall profitability of a industrial production system. Be specific and answer point wise. Give examples as appropriate.
B. State the main objectives of a modern industry (at least five) and explain the role of automation in helping achieve these.
C. Explain with examples the terms “economy of scale” and “economy of scope”. How does industrial automation help in achieving these? Cite examples.
D. Differentiate between a job shop and a flow shop with example what are their ‘process plant’ analogues? Give examples.
E. Run any internet search engine and type “History of Automation” to prepare a term paper on the subject.
F. There are some aspects of automation that have not been treated in the lesson. Consult references and prepare term papers on the impact of automation on
a. Environmental Appropriateness for Industries
b. Industrial Standardisation Certification such as ISO 9001
c. Industrial Safety
G. Locate the major texts on Manufacturing Automation
H. From the internet find alternate definitions of the terms: Industry, Automation and Control
Answers, Remarks and Hints to Points to Ponder
Point to Ponder: 1
A. Why does an automated system achieve superior performance compared to a manual one?
Ans: Because such systems can have more precision, more energy and more speed of operation than possible manually. Moreover, using computing techniques, much more sophisticated and efficient operational solutions can be derived and applied in real-time.
B. Can you give an example where this happens?
Ans: This is the rule. Only few exceptions exist. How many of the millions of industrial products could be made manually?
Point to Ponder: 2
A. Can you explain the above definition in the context of a common control system, such as temperature control in an oven?
Ans: Consider a temperature-controlled oven as found in many kitchens. A careful examination of the dials would show that one could control the temperature in the oven. This is a closed loop control operation. One can also control the time for which the oven is kept on. Note that in both cases the input signal to the process is the applied voltage to the heater coils. This input signal is varied as required to hold the temperature, by the controller.
B. Is the definition applicable to open-loop as well as closed loop control?
Ans: Yes
Point to Ponder: 3
C. Can you give an example of an automated system, which contains a control system as a part of it?
Ans: Many examples can be given. One of these is the following:
In an industrial CNC machine, the motion control of the spindle, the tool holder and the job table are controlled by a position and speed control system, which, in fact, uses a separate processor.
Another processor is used to manage the other automation aspects. Another example is that of A pick and place automated robot is used in many industrial assembly shops. The robot motion can be programmed using a high level interface. The motion of the robot is controlled using position control systems driving the various joints in the robotic manipulator.
D. What are the other parts of the system?
Ans: The other functional parts of the CNC System include: The operator interface, the discrete PLC controls of indicators, lubricant flow control, tool changing mechanisms.
Point to Ponder: 4
Try to find an example automated system which uses at least one of the areas of Industrial IT mentioned in Fig. (Hint: Try using the internet)
Ans: Distributed Control Systems (DCS) used in many large Continuous-Flow processes such as Petroleum Refining and Integrated Steel Plants use almost all components of Industrial IT
Point to Ponder: 5
A. Can you give an example of an automated system, some of whose parts makes a significant application of Industrial IT?
Ans: Distributed Control Systems (DCS) used in many large Continuous-Flow processes such as Petroleum Refining and Integrated Steel Plants use almost all components of Industrial IT
B. Can you give an example of an automated system, none of whose parts makes a significant application of Industrial IT?
Ans: An automated conveyor system used in many large Discrete Manufacturing Plants such as bottled Beverage Plants use no components of Industrial IT.
Point to Ponder: 6
A. Can you give an example of an automated system, which is reactive in the sense mentioned above?
Ans: Any feedback controller, such as an industrial PID controller is reactive since it interacts with sensors and actuators.
B. Can you give an example of an automated system, which is real-time in the sense mentioned above
Ans: Any feedback controller, such as an industrial PID controller is real-time, since it has to compute its output within one sampling time.
C. Can you give an example of an automated system, which is mission-critical in the sense mentioned above
Ans: An automation system for a Nuclear Power Plant is mission critical since a failure is unacceptable for such a system.
Point to Ponder: 7
A. With reference to Eq. (1), explain how the following automation systems improve industrial profitability.
d. Automated Welding Robots for Cars
e. Automated PCB Assembly Machines
f. Distributed Control Systems for Petroleum Refineries
Ans: Some of the factors that lead to profitability in each case, are mentioned.
a. Automated Welding Robots for Cars Increased production rate, Uniform and accurate welding, Operator safety.
b. Automated PCB Assembly Machines Increased production rate, Uniform and accurate placement and soldering
c. Distributed Control Systems for Petroleum Refineries Energy efficiency, Improved product quality
Point to Ponder: 8
A. You give an example of an industry where economy of scope is more significant than the economy of scale?
Ans: One such example would a job shop which manufactures custom machine parts by machining according to customer drawings. Another example would be a factory to manufacture Personal Computer components
B. Can you give an example of an industry where economy of scale is more significant than the economy of scope?
Ans: One such example would be a Power plant. Another one would be a Steel Plant.
Point to Ponder: 9
A. During a technical visit to an industry how can you identify the type of automation prevailing there from among the above types?
Ans: Check for the following.
· Whether automatic control exists for majority the equipment
· Whether supervisory control is manual, partially automated or largely automated
· Whether operator interfaces are computer integrated or not.
· Whether communication with individual control units can be done from supervisory interfaces through computers or not
· Whether any information network exists, to which automation system and controllers are connected
· Product variety, product volumes, batch sizes etc
· Whether the material handling systems are automated and if so to what extent.
The type of automation system can be determined based on these information, as discussed in the lesson.
B. For what kind of a factory would you recommend computer integrated manufacturing and why?
Ans: For large systems producing sophisticated and expensive products in large volumes having many subunits to be integrated in complex ways.
C. What kind of automation would you recommend for manufacturing a. Light bulbs
Ans: Fixed
b. Garments
Ans: Flexible
c. Textile
Ans: Programmable
d. Cement
Ans: Programmable
e. Printing
Ans: Flexible
f. Pharmaceuticals
Ans: Flexible
g. Toys
Ans: Flexible