Line balancing is one of the prominent but less talked about concepts in the field of supply chain that involves allocation of tasks among different workstations or machines in a production facility, distribution facility, assembly lines, packaging facility, fulfillment facility etc. to achieve maximum efficiency and productivity of the available resources to boost the output. The goal is to minimize idle time and maximize throughput ultimately leading to lower costs and higher profits in simple words.
Some of the important features of line balancing as implemented by professionals include:
- Increased throughput: This means producing more products in a given time.
- Better resource allocation: By eliminating bottlenecks helps ensure each workstation is operating to its optimal standards.
- Improved quality: Helps in producing significantly less errors and defects, by ensuring adequate attention given at a workstation before processing parts.
- Flexibility: Helps improve flexibility by resource allocation. It also has the feature of adding/subtracting workstations based on the needs of the process.
In an industrial setting, operations consists of different workstations performing specific tasks in series. Each workstation has a cycle time to manufacture/perform a task. This concept analyses the processes and calculates how resources must be allocated/ distributed so that any kind of bottlenecks in the tasks are eliminated ensuring each workstation operates to its fullest.
The process involves following steps:
- Calculating the cycle time for each workstation: Amount of time to finish per unit of the product/process.
- Identifying the total process time for all the workstations.
- Knowing the total operating hours/ shift hours for performing the tasks.
- Identifying the number of associates and the time to complete per unit of a product.
- Calculating the Takt time: Rate at which products/services must be provided so as to meet the customer demand. In simple words it is the amount of time to produce one unit of a product or service to match the rate of customer demand.
- Having a precedence diagram: This states the order in which tasks must be performed to fulfill the demand.
- Balancing the line: Allocating tasks among the workstations based on the Takt time calculated which minimizes idling and ensures efficiency.
It is important to test the line to ensure it meets the desired customer demand.
This article highlights a real world scenario of operations at a Liquor, wine & spirits distribution facility opened in 2020 serving the eastern and central parts of Pennsylvania which involves picking, packing, wrapping, staging, loading and delivery. For the facility the initial start-up was a bumpy ride due to lack of resource planning and standardization of processes. The facility operations are mainly categorized into inbound, picking, staging and loading on a larger umbrella and are further divided into many sub operations within each category.
The problem: One such operation in the staging process is that of wrapping the pallets, followed by labelling and staging. To give a detailed view, every picker picks up cases to build pallets which are audited in the audit region and are further wrapped and labelled. Post labelling the wrapped pallets are staged and finally loaded in their respective trailers for delivery. Thus the 4 important workstations in this case were The Runner, The Wrapper, The Labeler and The Stager. General observations highlighted piling up of pallets pre and post wrapping thereby affecting the entire flow up to the staging and delivery. This was due to a lack of process standardization and improper balance between labour allocation.
The industrial engineer of the site, Mr. Viraj Lele, dived in to find the root cause and implement an engineering approach alleviating this issue. A through time and motion studies was performed on all the 4 workstations highlighted above to identify the bottleneck and the root cause.
The problem was discovered about uneven distribution of labor and idling of the labeler during the time studies as conducted by Lele. The goal was thus to have proper distribution of associates between Runner and staging to prevent idling, piling of pallets and improve outcome of pallets to be staged.
The analysis had cycle times for each station and it was observed while the pallets are being wrapped the labeler was idling as there was no task at his workstation. The entire time of wrapping was spend without a job function for the labeler making the workstation redundant almost half the time.
Observations from the time study highlighted:
- The amount of time taken by the runner to complete a cycle
- The amount of time taken by the wrapper to finish wrapping
- The amount of time taken by the Labeler to label a pallet
- The amount of time taken by the stager to stage a pallet
The process: Lele implemented the concept of line balancing to identify the optimal number of stations required to achieve efficiency and remove the idling workstation. The total processing time for the entire operation and the average number of associates was used to calculate the takt time. This value was higher than the corresponding value of the average time taken by the Runner and wrapper making them 2 independent workstations. However the combined value of average time taken by the Labeler and stager surpassed the Takt time which made it clear about the labeler being the bottleneck. Thus the solution was to combine labeler and stager as one workstation making the process consists of 3 work stations instead of 4 which was achieved through the takt time calculation.
[FIGURE 1] CYCLE TIMES (SECS)
[FIGURE 2] CYCLE TIMES (SECS)
The outcome: This eliminated redundancy and increased the number of Stagers as the time travel for stagers was more than for Runners. The Stagers were asked to label their pallets, thus removing the need for a labeler and allocating the same resources to the staging workstation. This whole setup consisted of 1 runner and 4 stagers instead of 1 runner, 1 labeler and 3 stagers. The flow of this setup was streamlined such that the bottleneck was completely eliminated along with the elimination of the idling workstation.
The same analysis was replicated across all three shifts in a span of two weeks to verify and compare the results across all shifts. Making this project go live in two weeks and provided site with a savings of 360 minutes per day, which amounted to over $80,000 in operational cost savings, eliminating the issue of piling up of pallets pre and post wrapping.
Overall the same concept can be applied to study the processes at different sites based on the product, process and customer requirements. Some quick tips to follow Line balancing:
- Ensure accurate process time of all the workstations in an operation is captured
- Calculate the total process time of the operation (summing up the process times of workstations)
- Identify the total shift hours and number of associates working in that shift
- Calculate the average time taken by each associate to complete the operation
- Calculate Takt time = Total time of shift hours/customer demand
Takt time will help identify the number of workstations and labour allocations to run the process free of bottlenecks & idling thereby making the process LEAN.
