Job shop
| Job shop |
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Job shop is an organization made of a number of work stations which are capable of performing operations on objects in many specific and different ways. It shows that job shop is not a company which is specialised in one type product. Job shops are receiving orders from other companies to produce objects by putting them through several series(number of series depends on object) of operations[1].
The process of scheduling the day-to-day workings of a job shop is critical. The scheduling process means specifying which work station is to perform operation, from which contracts, and on which objects. Bad scheduling process may impact on[2]:
- work stations standing idle;
- deadlines;
- quality of objects which may be unacceptable.
Copanies have to use universal machinery and other equipment because they are used to variety of different operations. As well as workers who have to have high technical qualifications because of the wide range of products.
Definition by Cambridge Business English Dictionary
By this popular and well known dictionary Job shop normally is more often a small than a big company which makes a single, specific product or sometimes some part/number of products for one customer at a time. The dictionary indicates that employees of that kind of companies have to be multi-skilled because the work treats it as a significant and relevant feature.
Main constraints on jobs and machines
As mentioned job shop is created by a set of different machines which perform on jobs. There are 4 main constraints on those jobs and machines[3]:
- there is no specific rule in relation to sequences of the operations
- no signal that the operation can be interrupted
- each machine can be used only to one job at a specific time
- each job can be done only on one machine at a specific time
See also:
Job shop scheduling as the most problematic feature
Job shop scheduling problems are most visible in the production environment which is characterised by high variety and low volume[4]. The classical job shop scheduling problem is to determine an optimal schedule. An optimal and possible schedule which is able to achieve at least one of several possible objectives. In general, it is very difficult to do because often the problem is large and more complex. To reach this assumption, manufacturing layout is needed such as the flow shop[5].
The flow shop is a processing system where every single task is fully specified by a unique sequence. All the jobs visit the task stations in the same, repetitive order.
Footnotes
References
- Błażewicz, J., (1996)., Wolfgang Domschke b, Erwin PeschThe job shop scheduling problem: Conventional and new solution techniques, "European Journal of Operational Research"
- Emmons, H., (2013)., Flow Shop Scheduling, Springer
- Grefenstette, J., (1985)., Proceedings of the first international conference on genetic algorithms and their applications, Psychology Press Taylor & Francis Group
- Kuhpfahl, J., (2015)., Job Shop Scheduling with Consideration of Due Dates, Springer Gabler
- Pinedo, M., (2005)., Planning and Scheduling in Manufacturing and Services, Springer
Author: Rafał Gamrat
