Production Methods

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Learning outcomesStudents should be able to:

Apply knowledge and understanding of the following production methods: • assembly line;• batch;• mass; and• just-in-time (JIT).

Scales of productionThe annual demand and the time required to make parts or products (production rate) are important economic factors that determine the processes and equipment required to produce the parts or products. The scale of production required will impact on the type of machinery required, tooling costs, labour costs, skill level of the work force and the variety of parts that can be produced.

Assembly line production Assembly line production can be defined as a process where the assembly of a complicated product is broken down into a sequence of very small and simple tasks to be carried out by unskilled workers. The products are manufactured in large quantities and are identical but may have minor variation such as colour.

The assembly line concept has existed in a simple form since medieval times and has become the dominant system of production for complex mass

produced products especially in the automotive industry. Key developments that have driven the development of the assembly line are interchangeable parts, moving conveyor systems and more recently robotics and automation.

Assembly line production breaks the production down into very simple and specific tasks which reduce the level of skill required by line workers. As a result new workers can be trained quickly and can be easily replaced but wages tend to be higher in comparison to other low skilled jobs. Assembly line production systems offer good progression for workers who may start on basic assembly tasks but can have the opportunity to advance as they master each task in the assembly line plant.

An important feature of assembly line production is that each item produced is identical or very close to identical. This means that parts are identical and interchangeable so as a result replacing parts or repairing the product once it has entered service is much easier. This concept of interchangeability was first introduced by musket makers to simplify and

FACTFILE:GCSE Engineering and Manufacturing3.3.2 Production Methods

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FACTFILE: GCE HISTORY OF ART / ARCHITECTUREFACTFILE: GCSE ENGINEERING AND MANUFACTURING / 3.3.2

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deskill the repair of early firearms during the 1800s. Because of the highly structured and sequential nature of assembly line production any product defects or problems in the production process can be quickly identified and rectified. A breakdown at a given station on an assembly line can also be costly as a backlog will build up very quickly and halt production on the whole line. If defective products are not quickly detected then a large number of products may have to be scrapped, reworked or recalled at great expense.

Assembly line production involves moving the product along at a set speed often by suspending it from a moving conveyor. This eliminates heavy lifting and manual transportation of parts by workers. The work on an assembly line can be very repetitive and monotonous and can deny workers the opportunity for creativity or mental stimulation. Assembly lines can also reduce the amount of labour required due to increased efficiency and the replacement of many jobs by the use of robotics and automation.

Cars, mobile phones, computers and domestic appliances are generally mass produced on assembly lines.

Batch ProductionSmall batch production quantities range from 10 to 100 products and requires general purpose machines and highly skilled and flexible workers. Small batch production is in many ways similar to jobbing production.

Batch production usually involves products that are made in groups of 100 to 5000 units. Batch production uses general purpose machines but with the addition of CNC control and certain stages of production may be highly automated. A feature of batch production is the use of jigs and fixtures to ensure consistency and increase the speed of production.

Batch production can deliver reduced unit costs and products that are more tailored to suit the needs of different customer groups. For example a company that produces bicycles may switch between making a range of different styles of bicycle using the same staff and equipment. As production switches over, machine tools and equipment will have to be reset causing lost production or down time. Down time is a major disadvantage of the batch production system particularly if the batch sizes are small.

A more recent approach to batch production is the evolution of Flexible Manufacturing Systems (FMS) that use computer controlled general purpose machines and automated handling systems to produce a range of parts in small batches in a very cost effective way.

Typically clothing, food products, newspapers, high end sports cars and aircraft are produced using the batch production system. Batch production is also suitable for the manufacture of seasonal goods.

Mass Production

Mass production is suited to runs of over 100,000 units and uses special purpose equipment (dedicated machines) and a high level of automation to handle materials and work in progress. Mass production facilities are designed and organised to produce one specific product, and as a result they lack flexibility and product changes cannot be accommodated. The set up costs for mass production are very high due to the cost of specialised equipment but labour costs are low. Output from a mass production system produces goods at a high volume and low unit cost.

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In some cases the production, once started, cannot be stopped and must run continuously. The production of steel for example cannot be shut down as the furnaces may take many weeks to cool down and restart.

Products produced in mass production tend to be those more suited to a very high degree of automation and tend to be components or less complex products than those produced on assembly lines.

Examples of mass produced products are lightbulbs, electronic components, plastic cutlery, toilet tissue, raw plastics, batteries and petrochemicals.

Just in Time (JIT) Just in Time is a part of the Toyota production system which has become known as “Lean Manufacturing”.

JIT is a production philosophy that focuses on the elimination of various types of waste associated with inventory.

Just in Time uses a strict schedule to coordinate and to initiate the various stages of the production process.

A customer will place an order causing the generation of a work order to the store which would issue a demand to the parts manufacturing centre who would in turn issue an order for materials. These demands for parts and materials should arrive just as they are needed.

The main principle is that materials are not ordered until they are required and should arrive just in time to be used in production.

The Just in Time system aims not only to produce items just in time but also to produce just enough with no surplus product or stocks of parts. The main benefit of Just in Time is that it eliminates the huge cost of storage, work and materials that can be tied up in inventory and reduces the risk of producing parts and products that will not be sold.

Just in Time requires very close working relationships with suppliers and very fast communication so that orders to suppliers can be processed in real time. Electronic data interchange involves the linking and synchronisation of all the computer systems of all the companies involved in the supply chain to enable very fast responses to low stock levels.

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Revision Questions

1. Outline the factors that determine the most suitable production method for parts or products.

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2. Describe the characteristics of assembly line production.

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3. Discuss the disadvantages and advantages for workers on an assembly line.

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4. What advantage does batch processing have over assembly line production?

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FACTFILE: GCE HISTORY OF ART / ARCHITECTUREFACTFILE: GCSE ENGINEERING AND MANUFACTURING / 3.3.2

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5. Describe the features of mass production and give an example of a mass produced product.

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6. What is the economic benefit of the Just in Time production philosophy?

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7. Explain how Just in Time affects the relationship between a manufacturer and suppliers.

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8. Explain the main principle of Just in Time (JIT).

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FACTFILE: GCE HISTORY OF ART / ARCHITECTUREFACTFILE: GCSE ENGINEERING AND MANUFACTURING / 3.3.2

© CCEA 2018

Additional Resources:

Assembly lines https://www.youtube.com/watch?v=cZDeIO42mMY

Batch Processinghttps://www.youtube.com/watch?v=XKGak-4yh-8

https://www.youtube.com/watch?v=rGespWiyB3E

https://www.youtube.com/watch?v=7ZPS_iwoeJg

Mass Productionhttps://www.youtube.com/watch?v=BylLOWRojyY

https://www.youtube.com/watch?v=gFK_LqvlBjk

JIThttps://www.youtube.com/watch?v=kce2L23yLcw

https://www.youtube.com/watch?v=9dwqu7pRqGg