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Posted by Javeria Rahim
In manufacturing, non-value-added activities such as waiting, reworking, overproduction are common. Cumulatively, these activities can significantly increase production costs and slow down overall efficiency, which is why manufacturers are constantly trying to eliminate them. One way to do it is through a Yamazumi chart.
Yamazumi is a Japanese term that refers to ‘stacking up’. The Yamazumi chart is a stacked bar chart used in Lean manufacturing. It is a visual representation where time is being spent effectively and where it’s being wasted. The visualization makes inefficiencies “inescapable” and prompts discussions for improvement.
A Yamazumi Chart can help you find out Muda (Waste), Mura (unevenness), and Muri (Overburden). With a Yamazumi chart, you can balance your assembly line to optimize the cycle time and align it with takt time. Based on it, your team can make informed decisions about redistributing tasks or removing tasks for a bottleneck-free line.
In addition to the impact on customer satisfaction, quality products also result in fewer defects, lower production costs, and increased productivity. This is because high-quality products require fewer repairs, rework, and returns, which can result in significant cost savings over time. Additionally, when production processes are optimized to produce high-quality products consistently, efficiency and productivity improve, reducing production time and increasing output.
Yamazumi charts are a powerful tool available for process optimization. The importance of Yamazumi charts can be assessed from a research that highlighted that they helped a leather manufacturer significantly increase its efficiency from 36% to 72%. Here is how a Yamazumi chart helps:
1.Assessing Performance
The Yamazumi chart shows the timing of every task in every process in the manufacturing line, which helps you identify which tasks take more time than others. It help your team learn easily how workers are performing the task and highlights inconsistencies (Mura), so the workers can achieve consistent results every cycle.
2. Line Balancing
With the help of a Yamazumi Chart, your team can identify the operators or workstations that are overburdened or underutilized. The bigger picture helps your team make decisions about what task to remove from a procedure to reduce bottlenecks. Your team can also properly redistribute the tasks to an underutilized workstation or operator.
3. Waste Elimination
The Yamazumi chart meticulously breaks down each step in a process and assigns color codes based on value addition. Activities that consume time but don’t contribute to the final product become clear red flags. The best part about this tool is that it doesn’t just show waste, it quantifies it, allowing you to pinpoint exactly where the most significant time-wasters lie. The visual nature of the chart also helps identify bottlenecks in the process flow. Processes that exceed the ideal takt time (production rate) become evident instantly.
4. Easy to Use
A Yamazumi Cart is easy to use and understand for everyone on the team. You can easily view the data on different tasks and make informed decisions as per the data. The chart makes it easy to compare different figures and helps optimize the line.
Additionally, this data helps everyone understand why certain changes are necessary. When your workers understand the basis for changes, they don’t resist them.
5. Great for Communicating
You can place the Yamazumi chart on your factory floor to help everyone understand the goals of changes in the assembly line. With this practice, you can continue to improve the process for better output.
Figure 1: Yamazumi Chart in Kaizen
In manufacturing, a Yamazumi chart helps the viewers understand the assembly line’s cycle time and the role of each task in the process. Here’s a breakdown of the chart:
X-Axis
The x-axis denotes the different processes that take place in the making of a product. Each horizontal bar within the process refers to a single task. The x-axis can also refer to different operators or workstations in an assembly line, based on how you make the chart.
Y-Axis
The y-axis showcases the cycle time of the process, which refers to how long it takes to complete the task. Oftentimes, chart makers also add a line to denote the takt time. The presence of the takt time signifier helps identify if your current cycle time is more than the takt time.
Process Steps
The x-axis refers to the various processes taking place in an assembly line. The stacked bars however showcase different tasks that make up a process. Each process usually comprises different tasks. On the y-axis, you can measure the time each task takes in the whole process.
Cycle Time Breakdown
Within the Yamazumi Chart, the stacked bars often show up in three different colors. Each color shows the status of the task in the process.
Value-Added Task
These tasks are coded green. Value-added tasks add value to the final product in the eyes of the customer.
Non-Value Added Task
The red color is commonly selected to signify the non-value-added tasks. These are the tasks that do not add any value to the final product.
Necessary Non-Value Added Task
These activities are usually a shade of yellow. The purpose of necessary non-value-added tasks is that they are usually a requirement for legal or operational reasons.
Target Cycle Time
The target cycle time is the mean cycle time that every process should aspire to meet. The mean cycle time line is present in the chart as a dotted line that traverses across the graph. Any process that crosses the dotted line is above the required cycle time. This dotted line is often inline with the takt time.
Data Collection
The first step is data collection. You need to measure each process step and its cycle time. Just follow the process flow from the first step to the last and note down the cycle time for each. There are two ways to collect data
In a Gemba walk, industrial engineers go from unit to unit for a detailed overview of a workstation’s activities. They then engage with the assembly line workers, note down the activity of the workstation, and then record the cycle time. Gemba walks take longer to collect data as often engineers have to record multiple cycles at a workstation.
The second and a more modern way of data collection is through video recording. Industrial engineers record cycles on a workstation through cameras or even smartphone and then upload it on a software to conduct time and motion study.
Activity Classification
It is helpful at this point to identify and classify all the tasks into three types: value-added, non-value added and necessary non-value added.
Now depending on how you have collected the data, there are two ways to make a yamazumi chart. One is through the manual way through excel and next is through an automated software such as Kaizen Copilot
1- Formulate a Table in Excel
Process Step: Enumerate each process phase in the initial column.
Task: Within each cell, elaborate on the specific tasks involved. There can be several rows for tasks within each process step.
Duration: Document the average duration (in seconds) each task takes in the corresponding row.
2- Stack the Tasks
To formulate the stacked bar chart, you will require separate columns for each task type (Value-adding, Non-value-adding, necessary non-value-adding).
Determine Task Types: Categorize each task as value-adding, non-value-adding, or necessary non-value-adding.
Form Separate Columns: Incorporate new columns for each task type.
Allocate Durations: Compute and allocate the average task times from the “Duration” column into the corresponding task type columns based on your categorization.
3- Chart Formatting
Select the data table and navigate to the “Insert” tab.
4- Stacked Bar Chart
In the “Charts” section of the Insert tab, opt for the “Stacked Bar Chart” option. Choose a visually pleasing subtype like “Stacked Column” or “100% Stacked Column.”
5- Chart Customization
Click on any component of the chart to access formatting options. You can customize the table.
Axis Labels: Rename the X-axis to “Process Steps” and the Y-axis to “Duration (seconds)”.
Legend: Modify the legend to identify each task type.
Colors: Assign distinct colors to each task type for better visual differentiation.
Kaizen Copilot is an AI-powered continuous improvement solution that significantly boosts the productivity of industrial engineers. The solution combines the capabilities of several software in one easy to use platform that expediates continuous improvement projects.
Figure 2: Creating Yamazumi chart in Kaizen Copilot
Once the work content sheet is complete, Kaizen Copilot will automatically create precedence chart, line balance and Yamazumi chart.
Figure 3: Yamazumi Chart Illustration in Kaizen Copilot
Once the work content sheet is complete, Kaizen Copilot will automatically create precedence chart, line balance and Yamazumi chart.
Manual Creation | Kaizen Copilot |
Requires your industrial engineer to record each step with a stopwatch. | Automatically parses the video into tasks and records time data. |
Easy to adapt to different situations on the workstation. | Very detailed data collection that allows you to make informed decisions. |
Requires a long time for properly recording the time for each task. | Saves time and effort for your industrial engineers. |
It’s difficult to collect data for large manufacturing setups or complex assembly lines. | Easy to accommodate manufacturing lines of varying sizes. |
Industrial engineers have to create a Yamazumi chart in Excel manually. | Automatically creates a Yamazumi chart with the time studies data. Kaizen software even provides suggestions for task improvements. |
Data collection is prone to human error. | The software’s data collection capabilities are second to none. The data is accurate and free from human error. |
Minimal investment is required. | Requires an investment. |
Once you have successfully made your Yamazumi chart, now it is time to implement the changes.
1- Analyze the Chart
Identify the discrepancies in the process steps that are taking longer times. This is a great time for your whole team to identify all the bottlenecks i.e., tasks taking longer time than others. Recognize all the processes with more non-value-added activities.
2- Identify Opportunities for Positive Action
Utilize the chart to observe all the tasks that are easy to remove because they don’t add any value. Focus on the ones that can reduce cycle time when adjusted. Yamazumi chart will show all the different wastes in your assembly line. It will highlight the the operators that are overburdened and units that waste time waiting.
3- Apply Changes to the Line
Now it is time to implement the changes for a shorter or ideal cycle time. You can either introduce new tools or train the assembly line workers about the new ways to perform a task. Remove the non value adding tasks, reallocate to different stations
4- Assess the New Line
Once the changes are in place, it is time to check the results of the changes. Observe the new cycle time, has it changed with the new line? It is also important to note the impact of the new line on the end product’s quality.
5- Create an Updated Yamazumi Chart
With the changes in line, update your Yamazumi chart to reflect the new cycle time. You can use this new updated chart to keep an eye on new opportunities.
Monitor all the KPIs including cycle time, throughput, and rework rates to identify positive changes.
6- Improve the Line Based on Insights
Upgrading the line is a constant in lean manufacturing. With the help of your Yamazumi chart, your team can keep on updating your line to meet your evolving needs. Automatic data collection makes it even more easy to identify opportunities, you only need to do a single time and motion study.
Yamazumi charts are a helpful tool to identify and eliminate waste in the process. Kaizen Copilot makes it easier to optimize processes by automating data collection and analysis. Schedule a demo to see Kaizen Copilot in action.
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Brandin is a seasoned manufacturing leader, who has spent more than a decade designing and setting up assembly lines in both the US and China, optimizing them, and working with human operators to maximize productivity and quality.
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