Line Balancing

Description

Line Balancing is leveling the workload across all processes in a cell or value stream to remove bottlenecks and excess capacity. A constraint slows the process down and results if waiting for downstream operations and excess capacity results in waiting and no absorption of fixed costs.

Objective

Match the production rate after all wastes have been removed to the Takt time at each process of the value stream.

EXAMPLE:
Taking the example from the Takt time page as the starting point, there were additional studies conducted each the remaining processes that it takes to make UNIT ABC.

There are five processes in the workcell dedicated to only UNIT ABC.

Each process has same demand and available work time = same Takt time. The LOADING data was found using historical production data of ACCEPTABLE parts only including downtime but only when the processes were scheduled with operator(s). The customer only wants acceptable parts and that is what the customer demand is based on within the Takt time formula. When figuring the production rates (loading) the scrap or non-conforming pieces must be netted out.

Often the bottlenecks or areas of excess capacity are known by the team members but this analysis provides the quantitative data to prioritize activities to improve.

Process 1: Taking much longer than Takt time. Overtime is probably used to make up production and is the #1 constraint.

Process 2: Exceeding the Takt time, probably a lot of waiting and the excess capacity can be filled by absorbing some of the work from Process 1 and/or Process 4.

Process 3 & 5: Very close to meeting Takt time, not a focus area but possibly some best practices and application of LEAN tools can improve these loading rates. Improvement in these areas could be used to share workload from constraint processes.

Process 4: Taking longer than Takt time. Again, overtime is probably used or there are late deliveries, high expediting costs or unhappy customers. Apply Lean Manufacturing principles and try to alleviate workload to Process 2 or others that may be able be improved to absorb some of the workload.

Examine all the specific activities occurring in each process. Time studies, motion studies, and other Lean tools often provide most the ideas for improvement.

Develop a plan for immediate, low-cost improvements. Professional signage, advanced comprehensive training and capital investments are not needed or justified yet.

Run studies to determine the potential LOADING improvements. There is most likely not much that can be done to change the Takt time; focus on improving the LOADING (production rate).

Improving the LOADING, even in non-constraint operations is desirable, but the top priority is relieving constraint operations.

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AFTER

The table and chart below shows the results of the Line Balancing improvements.

Visual Management tools were added to reduce complexity and improve consistency of units produced.

Standard Operating Procedures (SOP) and training were done for all operators.

SMED activity was done on all operations with focus on Process 1.

Point-of-use tooling and shadow boards were implemented.

Kanbans were established for materials.

Some steps in each process were no longer required as former paradigms and rules were challenged.

The machines in a couple operations received upgrades and overdue minor rebuild and were added to a TPM program. There speeds were dramatically improved (the "performance" component of OEE)

Error-proof jig to prevent defects and rework was implemented.

And/on lights were added as communication signals.

5S event held with key stakeholders. 

There were gains...and the success was to the point where there was excess capacity. All the activities could now be completed in four processes. Floor space was gained and excess older and fully depreciated equipment were sold for cash.

A new loading study was done and the results are shown.

Recall, the goal of Line Balancing is to have the loading rates meet the Takt time and this is accomplished as the chart indicates.

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Takt Time and Line Balancing Calculator

A Takt Time and Loading calculator with an example is available here.

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