How can you use heijunka to level your production line?

1 Assess your current state

The first step to implement heijunka is to assess your current state of production. You need to collect and analyze data on your demand, capacity, cycle time, lead time, batch size, and inventory levels. You also need to identify the sources of variation and waste in your production process, such as defects, rework, overproduction, waiting, transportation, motion, and overprocessing. You can use tools such as value stream mapping, Pareto analysis, and fishbone diagrams to visualize and prioritize your improvement opportunities.

2 Calculate your heijunka box size

The second step to implement heijunka is to calculate your heijunka box size. This visual tool helps plan and schedule production according to the leveled demand, consisting of rows and columns that represent different products and time intervals. Each cell in the box contains a card that indicates the quantity and sequence of production for each product and time interval. To determine the box size, you need to consider the total production time per day or shift, the average demand per product per day or shift, the average cycle time per product, and the number of products per batch or kanban. The formula for the heijunka box size is (Total production time / Average cycle time) / Number of products per batch.

3 Fill and use your heijunka box

The third step to implement heijunka is to fill and use your heijunka box. You need to distribute your production cards evenly across the rows and columns of the box, following the pull system and the first-in-first-out (FIFO) principle. You also need to assign roles and responsibilities for the operators and supervisors who will use the box. The operators will pull the cards from the box and follow the instructions to produce the required quantity and sequence of products. The supervisors will monitor the production performance and replenish the cards as needed.

4 Monitor and adjust your heijunka box

The fourth step to implement heijunka is to monitor and adjust your heijunka box. You need to measure and track your key performance indicators, such as throughput, quality, delivery, inventory, and customer satisfaction. You also need to conduct regular reviews and audits to check the effectiveness and efficiency of your heijunka system. You should identify and eliminate any root causes of variation and waste that may affect your production flow. You should also seek feedback from your customers and stakeholders and adjust your heijunka box accordingly to meet their changing needs and expectations.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?