Assembly-Line Balancing
Assigning all tasks to a series of workstations so that each workstation has no more work than what can be done in the cycle time and so that the idle time across all work stations is minimized.
Includes precedence relationships (order in which tasks must be done)
1.Place the tools and the men in the sequence of the operation so that each component part shall travel the least possible distance while in the process of finishing.
2.Use work slides or some other form of carrier so that when a workman completes his operation he drops the part always in the same place-which place must always be the most convenient place to hand-and if possible have gravity carry the part to the next workman for his operation.
3.Use sliding assembly lines by which the parts to be assembled are delivered at convenient distances
Assembly lines, sometimes called flow or production lines, are undoubtedly the principal feature of mass production systems. Whilst the details may differ somewhat, the concept remains the same -the items are manufactured or assembled as they pass through a series of work stations.
Raw materials or components are fed in at the beginning of, and at certain points along the assembly line, and finished goods are delivered from the end of the line.
In the assembly of motor vehicles, the chassis unit is delivered to the first work station on the line and the workers at subsequent stations add the engine, transmission, suspension, body, trim and so on, until the vehicle is completed.
The total work content of the job, i.e. the total standard time for the job, is divided as evenly as possible amongst the stations on the line where a worker, or groups of workers, continually performs this same operation on successive items.
In other industries, such as the manufacture of domestic appliances, radios, televisions, etc., assembly lines usually consist of benches or belts along which the work is passed, the workers sitting at stations along one or both sides of the line, passing the work to one another along the line either at specified times or when they have completed their operations.
In many cases this type of production can be achieved without the use of human operators. For example, a transfer line consists of a series of work stations at which automatic tools perform operations. The work pieces are fed onto the line, move along and are automatically dumped at each station where one or more tools perform set machining cycles.
The output of assembly lines and transfer lines is determined by the cycle time at the stations. The cycle time at each station must be the same since each one must deal with the same number of items. If the cycle time is one minute, then the output from the last station, and consequently from the line, is one item every minute or sixty items per hour. Whilst it is comparatively easy to determine the cycle time in this manner, the allocation of the work to the stations is a somewhat more complex matter, and this aspect of assembly line design is normally referred to as assembly line balancing.
Work Elements (sometimes called Minimum Rational Work Elements)
As per the principles of work study, work can be divided into elements or even smaller components such as therbligs or basic motions.
Work Station: -
A combination of work elements to be performed serially forms a work station. In the type of assembly line we shall be considering, a work station is a physical location on the line normally staffed by a single worker
Work Station Time
This is the standard time required to complete the elements allocated to a particular work station
The objective of assembly line balancing is that, given a desired cycle time or output rate, the minimum rational work elements and their standard times, and other constraints, one should attempt to assign work elements to work stations in order to:
a) Minimize idle time or balancing loss
b) Minimize the number of work stations
c) Distribute balancing loss evenly between stations
d) Avoid violating any constraints.
Includes precedence relationships (order in which tasks must be done)
1.Place the tools and the men in the sequence of the operation so that each component part shall travel the least possible distance while in the process of finishing.
2.Use work slides or some other form of carrier so that when a workman completes his operation he drops the part always in the same place-which place must always be the most convenient place to hand-and if possible have gravity carry the part to the next workman for his operation.
3.Use sliding assembly lines by which the parts to be assembled are delivered at convenient distances
Assembly lines, sometimes called flow or production lines, are undoubtedly the principal feature of mass production systems. Whilst the details may differ somewhat, the concept remains the same -the items are manufactured or assembled as they pass through a series of work stations.
Raw materials or components are fed in at the beginning of, and at certain points along the assembly line, and finished goods are delivered from the end of the line.
In the assembly of motor vehicles, the chassis unit is delivered to the first work station on the line and the workers at subsequent stations add the engine, transmission, suspension, body, trim and so on, until the vehicle is completed.
The total work content of the job, i.e. the total standard time for the job, is divided as evenly as possible amongst the stations on the line where a worker, or groups of workers, continually performs this same operation on successive items.
In other industries, such as the manufacture of domestic appliances, radios, televisions, etc., assembly lines usually consist of benches or belts along which the work is passed, the workers sitting at stations along one or both sides of the line, passing the work to one another along the line either at specified times or when they have completed their operations.
In many cases this type of production can be achieved without the use of human operators. For example, a transfer line consists of a series of work stations at which automatic tools perform operations. The work pieces are fed onto the line, move along and are automatically dumped at each station where one or more tools perform set machining cycles.
The output of assembly lines and transfer lines is determined by the cycle time at the stations. The cycle time at each station must be the same since each one must deal with the same number of items. If the cycle time is one minute, then the output from the last station, and consequently from the line, is one item every minute or sixty items per hour. Whilst it is comparatively easy to determine the cycle time in this manner, the allocation of the work to the stations is a somewhat more complex matter, and this aspect of assembly line design is normally referred to as assembly line balancing.
Work Elements (sometimes called Minimum Rational Work Elements)
As per the principles of work study, work can be divided into elements or even smaller components such as therbligs or basic motions.
Work Station: -
A combination of work elements to be performed serially forms a work station. In the type of assembly line we shall be considering, a work station is a physical location on the line normally staffed by a single worker
Work Station Time
This is the standard time required to complete the elements allocated to a particular work station
The objective of assembly line balancing is that, given a desired cycle time or output rate, the minimum rational work elements and their standard times, and other constraints, one should attempt to assign work elements to work stations in order to:
a) Minimize idle time or balancing loss
b) Minimize the number of work stations
c) Distribute balancing loss evenly between stations
d) Avoid violating any constraints.
