Manufacturing system: Mass, Batch, Job-Shop and Project23/02/2020
There is no single concept of a manufacturing system covering all industries in every detail. It is necessary to examine the fundamental properties and characteristics of a range of systems and to consider the way they are synthesized and operated before consolidating general conclusions. What is seen depends very much on the viewpoint and the narrowness of the focusing range. Nevertheless there is much to be gained from a fundamental study of-all aspects of manufacturing systems and their interactions since there are opportunities for technology transfer between industries
Manufacturing systems must be designed by taking into account both steady state and-dynamic performance, whilst ensuring there is an adequate number of controllable variables to compensate the effects of uncontrolled disturbances. The technological process part of the manufacturing system is synthesized from interacting unit-operation subsystems, and this itself is a subsystem of the overall business system. The business system has a complex multivariate nature and for its effective control it is important that information flows and plans or set points are well defined to allow people to be effective controllers of the system.
Types of Manufacturing Systems
Custom Manufacturing Systems
Custom manufacturing is by far the oldest and most popular type of manufacturing system in existence. It also happens to be associated with both the highest-quality products and the lowest-volume efficiency.
In the custom manufacturing system, each item is produced by a single craftsperson, who works solely by hand or with the help of a machine. When machines are used, they tend to be highly specialized to their task and cannot produce more than one item at a time.
This system will tend to have the highest unit cost for the product manufactured. As a result, custom-manufactured products are of the highest quality but are also the most expensive products in the market.
Intermittent Manufacturing Systems
The intermittent manufacturing system allows companies to make different types of goods using the same production line. Therefore, the manufacturing facility is designed to handle different product sizes and requirements. Generally, the goods are processed in lots to fulfill orders.
This system is commonly referred to as a “job shop” due to its popularity in countries with relatively cheap labor making products for multinationals based thousands of miles away. The goods made using this manufacturing method are produced in small quantities, so they may not be suitable for stock. Customization is typically done post-purchase.
This type of system is designed for production runs that happen intermittently, hence the name, or products that don’t require high volumes. It uses general purpose machines and requires highly skilled labor.
Continuous Manufacturing Systems
Continuous manufacturing systems are designed to enable the mass production of a single product. The product goes through an assembly line with different stations where parts are added or worked on a little further. This method first arose during the Industrial Revolution and is most closely associated with the Ford Company, which employed the system to produce Model Ts in the 1920s.
This type of production system is ideal when a company has very high volume targets since it reduces the unit cost of the product. It does, however, require a massive capital injection at startup due to the investment in equipment and labor required.
Flexible Manufacturing Systems
Flexible manufacturing is a modern manufacturing system that has become very popular. It involves a significant investment in machinery, although it reduces labor costs by implementing robots eschewing human labor altogether. These machines can easily be reconfigured to manufacture different products in different quantities, and the whole process is automatic.
This method is called flexible manufacturing due to the flexibility in the variety of high-volume goods it can produce. Due to the automated process, quality control is a lot easier, and unit costs are low.
CLASSIFICATION OF PRODUCTION SYSTEMS
Manufacture of discrete parts or assemblies using a continuous process are called Mass Production. This production system is justified by very large volume of production. The machines are arranged in a line or product layout. Product and process standardization exists and all outputs follow the same path.
Mass Production is characterized by
- Standardization of product and process sequence
- Dedicated special purpose machines having higher production capacities and output rates
- Large volume of products
- Shorter cycle time of production
- Lower in process inventory
- Perfectly balanced production lines
- Flow of materials, components and parts is continuous and without any back tracking
- Production planning and control is easy
- Material handling can be completely automatic
Advantages of Mass Production
Following are the advantages of Mass Production:-
- Higher rate of production with reduced cycle time.
- Higher capacity utilization due to line balancing
- Less skilled operators are required
- Low process inventory
- Manufacturing cost per unit is low
Limitations of Mass Production
Following are the limitations of Mass Production:-
- Breakdown of one machine will stop an entire production line
- Line layout needs major change with the changes in the product design
- High investment in production facilities
- The cycle time is determined by the slowest operation
American Production and Inventory Control Society (APICS) defines Batch Production as a form of manufacturing in which the job pass through the functional departments in lots or batches and each lot may have a different routing. It is characterized by the manufacture of limited number of products produced at regular intervals and stocked awaiting sales.
Batch Production is characterized by-
- Shorter production runs
- Plant and machinery are flexible
- Plant and machinery set up is used for the production of item in a batch and change of set up is required for processing the next batch
- Manufacturing lead-time and cost are lower as compared to job order production
Advantage of Batch Production
Following are the advantages of Batch Production:-
- Better utilization of plant and machinery
- Promotes functional specialization
- Cost per unit is lower as compared to job order production
- Lower investment in plant and machinery
- Flexibility to accommodate and process number of products
- Job satisfaction exists for operators
Limitation of Batch Production
Following are the limitations of Batch Production:-
- Material handling is complex because of irregular and longer flows
- Production planning and control is complex
- Work in process inventory is higher compared to continuous production
- Higher set up costs due to frequent changes in set up
Job-shop production are characterized by manufacturing one or few quantity of products designed and produced as per the specification of customers within prefixed time and cost. The distinguishing feature of this is low volume and high variety of products.
A job-shop comprises of general-purpose machines arranged into different departments. Each job demands unique technological requirements, demands processing on machines in a certain sequence.
Job-shop Production is characterized by:-
- High variety of products and low volume
- Use of general purpose machines and facilities
- Highly skilled operators who can take up each job as a challenge because of uniqueness
- Large inventory of materials, tools, parts
- Detailed planning is essential for sequencing the requirements of each product, capacities for each work centre and order priorities
Advantage of Job-shop Production
Following are the advantages of Job-shop Production:-
- Because of general purpose machines and facilities variety of products can be produced
- Operators will become more skilled and competent, as each job gives them learning opportunities
- Full potential of operators can be utilized
- Opportunity exists for Creative methods and innovative ideas
Limitation of Job-shop Production
Following are the limitations of Job-shop Production:-
- Higher cost due to frequent set up changes
- Higher level of inventory at all levels and hence higher inventory cost
- Production planning is complicated
- Larger space requirements
Project production is characterized by complex sets of activities that must be performed in a particular order within the given period and within the estimated expenditure. Where output of a project is a product, such products are generally characterized by immobility during transformation. Operations of such products are carried out in “fixed position assembly type of layout” which can be observed in production of ships, locomotive and aircraft, construction of roads, buildings, etc.
Characteristics of Project Production
(i) Definite beginning and definite end
Each project has a definite beginning and a definite end.
(ii) “Fixed position” layout
Where the output of a project is a product, such products are generally characterized by immobility during transformation. Operations on such products are carried out in “fixed position assembly type of layout” which can be observed in production of ships, locomotive, aircraft, construction of roads/ buildings, etc.
(iii) High cost overruns
Often delays take place in the completion of the projects. Such delays are generally very expensive due to escalation in the cost of factors of production and incident of penalties.
(iv) Personnel problems
Project production has many personnel related problems namely:-
- When there is a fast build up, staff is either borrowed from other departments or hired for short duration. Therefore, personnel involved in the project have limited (or short lived) interest in the project.
- Since each project has a limited duration, the staff starts spending more time forgetting prepared for the next project.
- Site for the project may be in the underdeveloped region and it may change from project to project which causes dislocation of the normal life.
Importance of Project Production
(i) Non-uniform requirement of resources
Requirement of resources for project production is not uniform. At the end of the project, resources from the project are redeployed elsewhere in other projects. Even during the life of the project, requirement of resources is not uniform. Generally resource requirement (men, materials, money, etc.) in the beginning of the project is low which builds up fast with the progress of the project as more and more resources are absorbed, and then it levels off until there is gradual cutback as the project approaches completion.
(ii) Involvement of different agencies
A project generally involves many tasks, each having its own specialization to be performed by different agencies. The tasks generally have strict precedence (i.e. certain tasks must be completed before the next begins) amid as such co-ordination between agencies is of utmost importance.
(iii) Scheduling and control
Because of large number of activities, involvement of different agencies and strict precedence requirements, scheduling and control assumes great importance. Some network planning techniques like PERT and CPM have been found to be very useful to overcome the problems mentioned above.