Manufacturers & Distributors ARTICLE - Get Into the Mix: Consider Mixed-Model Scheduling
Target Audience: Manufacturing and Distribution Companies, M&D Industry, Manufacturing Distributors, Marketing Department Employees, Public Relations
If your manufacturing company produces a variety of products with different specifications, you may struggle with how to schedule production. Multiple changeovers can result in multiple production gaps, which isn’t good for anyone.
Most manufacturers use a batch-build approach to capture savings associated with large-volume production and limited changeovers. Companies may be saving some money, but are they also delaying delivery on some products while other products pile up in inventory? Another option you may want to consider — one that fits well with lean manufacturing — is mixed-model scheduling.
With mixed-model scheduling, you layer production of less-popular products with the ongoing production of your best sellers. For example, let’s say your most popular product is Widget A. There’s less demand for Widgets B and C, but sales of both are about equal.
With mixed-model scheduling, an eight-hour workday might consist of making one Widget A per hour and one each of Widgets B and C every two hours. The manufacturing sequence could be B, A, C, A, B, A, C, A and so on. At the end of the day, you have produced 16 products: eight As, four Bs and four Cs. Of course, customer demand should determine the mix.
This allows you to speed the time-to-market on all three products without amassing a large inventory. It also means your labor requirements are stable, you can size machines appropriately, and demand on upstream suppliers is smoother.
The challenge, though, is to develop efficient line operations to support mixed-model scheduling. These operations must be flexible enough to deal with the product mix without requiring long, expensive or inconsistent changeovers.
Stay in the Family
When implementing mixed-model scheduling, begin by identifying product families — products that require the same or similar manufacturing processes. Forming product families allows you to develop a clear mixed-model production path using group technology manufacturing cells, where workers perform several operations for different products. The operations and the products are similar — but not identical — and adjacent employees may share tasks to maintain work balance and limit idle time.
A critical component of keeping products moving through the line is ensuring that every part and tool required for each product is immediately available in each cell. This may not be problematic for smaller products but can pose challenges for larger items, such as refrigerators. Possible solutions to those challenges may include multipurpose tools or dedicated cells with permanent tool setups and continuous replenishment of small quantities of parts.
As you determine the optimal design for your group technology cells, bear in mind that market changes may create imbalances in the demand for entire cells or a product. Design accordingly, with an eye to multiple levels of staffing and a plan to move workers among cells as demand varies.
In addition, don’t lose sight of the fundamentals of cell design. It’s OK to have excess equipment capacity in a cell; it’s not OK to have excess human capacity. Employees are more flexible than machines, so cross-train them to perform several jobs as needed.
Be sure to train your suppliers, as well. They likely run a high mix of products, too, so they’ll understand if you request more frequent deliveries. Better yet, show them your mixed-model operation so they understand the vital role they play.
Know Your Limits
Mixed-model scheduling isn’t for every manufacturer. If you make larger quantities of a few products, for example, you may be better off with a product-focused cell arrangement in which one cell runs one product through multiple operations. But if you produce smaller quantities of more products, mixed-model production may be the right approach.
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