JOB SHOP PRODUCTION
Job shop production are
characterised by manufacturing of 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.
Characteristics
The Job-shop production system is
followed when there is:
1.
High
variety of products and low volume.
2.
Use
of general purpose machines and facilities.
3.
Highly
skilled operators who can take up each job as a challenge because of
uniqueness.
4.
Large
inventory of materials, tools, parts.
5.
Detailed planning
is essential for sequencing the requirements of each product, capacities for
each work centre and order priorities.
Advantages
Following
are the advantages of job shop production:
1.
Because of
general purpose machines and facilities variety of products can be produced.
2.
Operators will
become more skilled and competent, as each job gives them learning
opportunities.
3.
Full potential of
operators can be utilised.
4.
Opportunity
exists for creative methods and innovative ideas.
Limitations
Following
are the limitations of job shop production:
1.
Higher cost due
to frequent set up changes.
2.
Higher level of
inventory at all levels and hence higher inventory cost.
3.
Production
planning is complicated.
4.
Larger space
requirements.
BATCH PRODUCTION
Batch production is defined by American Production and
Inventory Control Society (APICS) “as a form of manufacturing in which the
job passes through the functional departments in lots or batches and each lot
may have a diferent routing.” It is characterised by the manufacture of
limited number of products produced at regular intervals and stocked awaiting
sales.
Characteristics
Batch
production system is used under the following circumstances:
1.
When there is
shorter production runs.
2.
When plant and
machinery are flexible.
3.
When 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.
4.
When
manufacturing lead time and cost are lower as compared to job order production.
Advantages
Following
are the advantages of batch production:
1.
Better
utilisation of plant and machinery.
2.
Promotes
functional specialisation.
3.
Cost per unit is
lower as compared to job order production.
4.
Lower investment
in plant and machinery.
5.
Flexibility to
accommodate and process number of products.
6.
Job satisfaction
exists for operators.
Limitations
Following
are the limitations of batch production:
1.
Material handling
is complex because of irregular and longer flows.
2.
Production
planning and control is complex.
3.
Work in process
inventory is higher compared to continuous production.
4.
Higher set up
costs due to frequent changes in set up.
MASS PRODUCTION
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 standardisation
exists and all outputs follow the same path.
Characteristics
Mass production is used under the
following circumstances:
1. Standardisation of product and process sequence.
2. Dedicated special purpose machines having higher
production capacities and output rates.
3. Large volume of products.
4. Shorter cycle time of production.
5. Lower in process inventory.
6. Perfectly balanced production lines.
7. Flow of materials, components and parts is continuous
and without any back tracking.
8. Production planning and control is easy.
9.
Material handling
can be completely automatic.
Advantages
Following
are the advantages of mass production:
1.
Higher rate of
production with reduced cycle time.
2.
Higher capacity
utilisation due to line balancing.
3.
Less skilled
operators are required.
4.
Low process
inventory.
5.
Manufacturing
cost per unit is low.
Limitations
Following
are the limitations of mass production:
1.
Breakdown of one
machine will stop an entire production line.
2.
Line layout needs
major change with the changes in the product design.
3.
High investment
in production facilities.
4.
The cycle time is
determined by the slowest operation.
CONTINUOUS PRODUCTION
Production facilities are
arranged as per the sequence of production operations from the first operations to the finished product. The items are
made to flow through the sequence of operations through material
handling devices such as conveyors, transfer devices, etc.
Characteristics
Continuous
production is used under the following circumstances:
1.
Dedicated plant and equipment with zero flexibility.
2.
Material handling
is fully automated.
3.
Process follows a
predetermined sequence of operations.
4.
Component
materials cannot be readily identified with final product.
5.
Planning and
scheduling is a routine action.
Advantages
Following
are the advantages of continuous production:
1.
Standardisation
of product and process sequence.
2.
Higher rate of
production with reduced cycle time.
3.
Higher capacity
utilisation due to line balancing.
4.
Manpower is not
required for material handling as it is completely automatic.
5.
Person with
limited skills can be used on the production line.
6.
Unit cost is
lower due to high volume of production.
Limitations
Following
are the limitations of continuous production:
1.
Flexibility to
accommodate and process number of products does not exist.
2.
Very high
investment for setting flow lines.
3.
Product
differentiation is limited.
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