IE-117 Line Balancing

IE-117 Line Balancing. Rev 1.0.

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[Audio] Line balancing attempts to assign work elements to workstations to minimize the losses due to imbalances between work stations. Balancing to TAKT time (based on the customer's demand) will optimize the number of stations required to produce a product for a given cycle time for the line. The goal is to minimize the amount of direct labor and equipment allocated to the line to minimize overall manufacturing costs..

[Audio] The line balancing method can be split into different steps. Click on each step below to see more details..

[Audio] Let's start with explaining TAKT Time: The German Word Takt time, meaning "pace", is the fundamental to lean manufacturing because it represents the HEARTBEAT of the business is the frequency at which a product must be produced in order to satisfy the customer demand It can be calculated by dividing the Total Time Available by the Total Customer Demand within a certain period (i.e. a shift, day, week, month etc.) Once you know the TAKT time is can be used to calculate the minimum manpower required to produce to the customer demand by dividing the Total Process Time by the TAKT time..

[Audio] To establish the TAKT time we need: - the volume demand forecast - the total available manufacturing time - without break time, allowances, etc - Then we can calculate the TAKT time - what will be the pace for the manufacturing process..

[Audio] Secondly we have to define the process time. work out the process time required for each work process MOST is the best time measurement tool to establish the process time for manual assembly works the machine process time can be calculated based on the machine performance actual time study can also be performed to establish the process time tasks can be grouped into bundle in order to facilitate the assigning process to each station.

[Audio] Once we have all process times, we can assign tasks to specific workstations. assign tasks to each station based on the work contents process time each station process time should not exceed the Planned Cycle Time PCT (which is 95% of the TAKT time) This allows us to cover for some minor variances of the real cycle times in the production line. Compute appropriate measures (# of workstations, percent of idle time) to ensure the assignment of tasks is being optimized TAKT time can also be used to determine the number of workstations required # workstations required = (total process time) / (TAKT time) NOTE: this formula is to provide a reference number rather than a standard as perfect line balancing is nearly impossible.

[Audio] Since we only can reach customers' demand if the CT at a station is higher than the TAKT time, we have to balance the process cycle times against the Planned Cycle Time if any process cycle time is greater than the TAKT time, the customer required delivery will not be met if any process cycle time is far less than the TAKT time, there will be waste in the processes. The objective here is to minimize the idling time to lead to higher resources utilization, and eliminate the inventory/WIP piling up due to the imbalanced work processes.

[Audio] once step 3 & 4 are completed, the process cycle time for each station now becomes the standard to achieve however, the standard process cycle time will change again with respect to the change in volume demand and TAKT time.

[Audio] To ensure we have realistic cycle times and a good line balance for production, we have to measure, control and continuously improve. all the station process cycle time MUST be measured and controlled periodically always look for opportunity to improve the process cycle time by eliminating more wastes review work methods and possibility of reassigning the tasks for further balancing measure the balancing rate to ensure it is always > 90[break]%.

[Audio] Let's look at an example: If we balance at takt time, any variation (longer cycle time, scrap, rework, different operator) will cause us to not hit takt time and be short on customer orders We need to buffer against these variations but running slightly faster than takt time. This is called the Planned Cycle Time (PCT.) A good start target is 92 to 95 % of takt. This percentage allow us buffer for internal variations like operator fatigue, minor interruptions in the cycle and variation of work content between products. Variations such as downtime, setup and scrap are not included in PCT. In this example, we decided to balance work to a PCT of 95% takt time: PCT = 100 sec x .95 = 95 sec.

[Audio] When a mix of products will be produced on the same line we need to look at the Average Weighted Cycle Time. An Average Cycle time Considers the volume of each product in the mix Along with its respective Cycle time. How do we calculate it? By multiplying the cycle time by each demand, then we Sum them all and divide by the total demand. This Helps to determine the impact that products whose cycle time exceed takt time will have on the overall mix performance so we can identify the Bottlenecks in the process. Keep in mind, this is only necessary in a mixed model line..

[Audio] Before designing a layout it is critical to know if the product family you will be flowing as a single value stream is capable of meeting takt time. Understanding takt time and knowing your planned cycle times will influence the design of the layout. In this case we cannot meet Customer demand the way is set, as a consequence you will end up running over time.

[Audio] First: Reduce the Cycle time by looking at the non value add activities within the Process Step Once you have reduced it then look at the balancing, can some of the work context in Step one be done by another operator. What else can you see here? Can you spot the waste?.

[Audio] A tool that can be used when balancing lines which involved the entire team is the Balance Charting tool. This tool allows the entire team to identify all steps within a process and determine whether they are: Value Add Non Value Add Balancing is as simple as reassigning steps by moving pieces of paper or reducing the height (time) of a step through improvement..

[Audio] Now we need to go to the GEMBA and Observe the process to do very detail time studies and observations on how can we improve the process. You will need to breakdown the operations into smaller pieces and analyze the work that is being down. Why are trying to accomplish 2 things by breaking it down. First we want to identify waste (Low hanging fruit) we want to make sure that we eliminate any waste that we can. Second we want to break the operations into smaller pieces so we can balance with the next operation In this example we have broken 2 steps, in real life you want to break down all the operations and observe the process..

[Audio] We will need to balance per product against the planned Cycle time. To Balance we need to break down each operation into smaller pieces, in the weld example we are considering the loading of the piece into a welding Fixture, the Welding and then the Unloading of the part off the fixture. We cannot cut the welding but the second operator and remove the part of the fixture. You will need to make sure that you have 2 fixtures. this is just one example on how to balance, but you will have to look into your process and see where is feasible to break down operations wherever is needed, One thing to pay attention is to look for the idle times of the operators when machines are running. In this example we do not have machines that run on their own, but in real life you will have this opportunity. At Jabil it is very common to see people watching machines, How can we avoid this? by studying the operations. In this example we were able balance the workload under the Planned cycle time using 3 operator that would be dedicated to Family A You will have to repeat the process for the other Families, also dedicating the Heads to each cell..

[Audio] Now that we have Balanced Product A, you will need to repeat the process for all the products in this Family X and design the assembly cell..

[Audio] NOTE TO JUAN: first show diagram (top left), then the definitions (bottom), and last the calculated number (top right) Let's have a look at some line balance related metrics with an example: In this example we have 3 physical stations: Station 2 is only a machine, Stations 1 and 3 are operated by Manual stations. The Bottleneck cycle time is the maximum value of the cycle times in a group of operations (this can be a machine process or a manual process) In this example 30sec The Total Cycle Time TCT is the summation of all cycle time values of processes in the same group. 65 sec in this case..

[Audio] NOTE TO JUAN: first show diagram (top left), then the definitions (bottom), and last the calculated number (top right) The difference at each station between the stations' cycletime and the bottleneck cycletime can be considered as a waste or loss. Line Balancing Loss LBL = the summation of all LBL values of processes in the same group The sum of these losses in our example is 25 sec Line Balancing Rate LBR% = the rate of how balanced a manufacturing line is. This can be calculated in 2 different ways, resulting in 72[break]%.

[Audio] NOTE TO JUAN: first show diagram (top left), then the definitions (bottom), and last the calculated number (top right) Now we focus only on the stations where there are operators. (but the bottleneck can still be a machine like in our example) Operator Balancing Loss OBL = the summation of all PBO OBL values of processes in the same group. Operator Balancing Rate OBR% = the rate of how balanced a manufacturing line is, but only focused on analyzing the balancing of operators. You may also find more details about the calculations in the IEDB Handbook..

[Audio] Production lines must be able to quickly adapt to changes in product or changes in Takt. It is for this reason why Multi-skilled operators become a key part of creating workcell flexibility. The linebalance will change depending on the number of operators in a production line. A Playbook is a 'strategic operator to workstation assignment' in a given manufacturing cell layout. Playbooks are product specific (i.e. specific to each assembly number). Playbooks are layout design specific..

[Audio] The purpose of a Playbook is to allow for different operator headcount build strategies within the same exact manufacturing cellular layout AND for the same exact assembly number..

[Audio] A Single Assembly can have multiple Playbooks. Playbooks will align operator headcount within a manufacturing cell to achieve specific KPIs. These KPIs can be HC, LBR, OBR, UPH, UPPH, and SMH. Each Playbook will have specific data depending on the headcount and needs to be stored in the IEDB. In this example you can see that the situation or Playbook with 4 operators instead of 3 has a better Operator Balance Rate (OBR) and the Runrate or UPH is almost double. So the preferred option for this line is to run with 4 operators, but it's possible to run the line with 3, although then with lower OBR and UPH..

[Audio] Creating a good line balance, will give us advantages in the area's of Productivity, because We have a balanced work content to set the pace of the line We can calculate the exact manpower needed, and Eliminate forms of waste Performance measurement, because We measure according a set standard Each operator is doing a similar amount of work, and We have an optimized production line capacity Working capital, because Investments are based on customer demand We have optimized resources, and We can reduce WIP levels..

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PUBLIC | ©Jabil Inc. 2017. All Rights Reserved.. Sources / Reference Material Maynard’s Industrial Engineering Handbook ( Kjell Zandin ) Handbook of Industrial Engineering – Technology and Operations management 3E (Gavriel Salvendy ) IEDB Training Manual (Jabil).

PUBLIC | ©Jabil Inc. 2018. All Rights Reserved.. User Date Version # Davy Nulens 28/08/2018 1.0.

PUBLIC | ©Jabil Inc. 2018. All Rights Reserved.. Question Answer The recommended Bottleneck Cycle Time is …. of the TAKT time 95%.

PUBLIC | ©Jabil Inc. 2018. All Rights Reserved.. Question Answer Drag and drop the Line balancing process in the correct order Select the correct value for each metric Select benefits of a good line balance Reduced WIP levels Optimal number of operators in production line No big differences in total work content between operators Less risk of buying too much equipment (All of the above).