Resource: Line Balancing Cycle Time Takt Time Workload Balance Man Machine Setup Time Assembly Line Balancing
• Everyone is doing the same amount of work
• Doing the same amount of work to customer
• Variation is ‘smoothed’
• No one overburdened
• No one waiting
• Everyone working together in a BALANCED fashion
• The time it takes one workstation in a process to complete its workload for processing a part.
• Cycle Time is the total elapsed time to move a unit of work from the beginning to the end of a physical process.
• Note: Cycle Time is not the same as Lead Time
Takt‐time = Net Available Time per Day/ Customer Demand per Day
• Takt Time sets the ‘beat’ of the organization in synch with customer demand.
• One of the three elements of Just In Time (along with one‐piece flow and downstream pull)
• Takt Time balances the workload of various resources and identifies bottlenecks.
• Often confused cycle speed with time or machine speed.
• Takt Time comes from a German word ‘takt’meaning rhythm or beat. It is a term often associated with the takt the conductor sets so that the orchestra plays in unison.
• Takt Time is used to match the pace of work to the average pace of customer demand.
• Takt is not a number that can be measured
• Cycle Time may be less than, more than, or equal to Takt Time.
• You can never measure Takt Time with a stop watch. You must calculate it. The formula for
• Takt Time is expressed as “seconds per piece”, indicating that customers are buying a product once every so many seconds. Takt Time is not expressed as “pieces per second”
What is Line Balancing
• Assembly line balancing is concerned with readjusting the size and assignment of the work force (balancing) of a high volume assembly line for different desired production rates.
• The line is like a huge machine, and the sequencing is part of its original design. However, there is some flexibility to reassign labor and resources across the line if the production rate is increased or decreased.
• When a plan calls for a change in the labor force level, it is through re-balancing that we can absorb more or less labor on the lines.
Assembly Line Balancing
• The work is divided into series of elementary tasks withshort durations.
• It is impractical to assign a different worker to each task, instead tasks are grouped into managerial bundles which are assigned to a work station.
• The goal is to obtain task groups that will minimize idle time of workers and will provide high utilization of labor and equipment. This goal can be achieved by designing the groups to represent approximately equal time requirements (balancing)
• Unbalanced lines are undesirable since they create morale problems.
Models of Assembly Line Balancing
There are two basic line balancing model which are usually considered:
• Model I tries to determine the minimum work force to achieve a given desired production rate.
• Model II tries to determine the maximum production rate which can be achieved with a given number of workers
Line Balancing ‐ Considerations
• Can only be used if:
– Processing time for an activity does not vary
– Several operators, performing consecutive operations, working as a unit
– Only if you want a balanced line, may want to de‐couple (consider quality, inventory concerns)
• Specify sequential relationships among activities using a precedence diagram
– Precedence diagram does NOT illustrate work flow.
– It illustrates constraints in production order
– Fewer constraints allows for more flexibility in line balancing solutions
• Meet production demands ≡ Perfect line balancing solution (i.e., 0% idle time, 100% efficiency).
• Required data:
– Work elements and associated times
– Precedence diagram
– Rate of required production
• Times usually given as constants, but not really constant
• Line may ‘look’ balanced ‐ but operators pace to each other
• Rate of production dependent on slowest station (i.e., bottleneck)
• Once the Takt time is has been determined, it is now a matter of comparing several aspects of the process and the Takt time in order to design a balanced workload. Following operational elements of each product are examined with the relation of Takt‐time:
– Man Time
– Machine Time
– Setup Time
• The man‐time is compared to Takt time to address two opportunities:
• Automation: Equipment does not need to be monitored unless something goes wrong.
• Work Improvement: Examining the individual work element of each operation and determining if they can be reduced, shifted, re‐sequenced, combined or eliminated.
Machine time is compared to takt time in order to determine if the fixed cycle time of any piece of equipment is greater then the takt time. If this is so, action must be taken to change the available time
– Reduce the cycle time
– Change the process
– Add equipment
– Split demands
• The time it takes to change over to make a different part or do a different process
• Identify steps needed to complete the change over
• There typically Internal and external steps
– Internal: steps where the process must be stopped to complete
– External: steps which can be done without stopping the process
• Seek to make Internal steps External