(a.k.a. Heijunka, Balancing) A Technique used to balance production throughput according to the needs of customers (Demand).
Comments: Level-Loading is loading your production system according to the exact needs (+ or -) of your customers. Ideally it is based on the consumption of products customers are “pulling” from your system.
Mixed-Level-Loading supports the same concept as Level-Loading which is to supply your customers with exactly what they need when they need it. However, “mixing” includes producing perhaps many different models of products in correct quantities and ratios to satisfy customer demand for a variety of products with shorter than average lead-times.
Level and Mixed-Level Loading are advanced Lean methods and require a good deal of Lean implementation before they can be very successfully applied in “real world” plants. You must have the ability to switch from one product to another very quickly (usually automatically) to make this system work.
Often you will need to modify tooling to accept a variety of parts so that no changeover process is required at all.
Example: One particular client of ours is an automotive OEM plant. They are so good at Mixed-Level-Loading that on one small conveyor you will often see 2 or 3 Toyota parts followed by 1 or 2 GM parts, followed by 4 or 5 Nissan parts, followed by 2 Toyota parts, followed by 6 or 8 Ford parts, followed by…
You get the point! Finding the right “mix” to satisfy each customer “real-time” is much easier than being able to produce that mix. Putting all the best Lean tools in place will enable you to eventually take your production to this pinnacle level of performance.
SME also has a good article and graphic about the “Heijunka Box” tool that you might find useful.