So far in this series we’ve talked about what Mixed Model Manufacturing is, and whether or not it might be applicable to your company. Let’s now shift gears and talk about why Mixed Model Line Design is a good idea, and what the specific benefits are.
BENEFIT 1: BETTER RESOURCE UTILIZATION
The resources we’re referring to are people, equipment, buildings, raw materials, WIP. It only makes sense that if you can build multiple products using the same resources, that your resource utilization is going to go up. If you don’t have demand for one product, you can be building another one using the same resources, and not have them sitting idle. The factory footprint is going to also be smaller, of course.
BENEFIT 2: NATURAL SMOOTHING
The more products you can mix, the more you can take advantage of a natural smoothing effect that takes place. Demand for individual products can vary quite a lot, but they don’t all go up or down at the same time. The more you can mix, the smoother the overall variation in demand from day to day.
BENEFIT 3: MINIMUM MANUFACTURING CYCLE TIME
When you follow the design principles of Mixed Model Line Design, the time from manufacturing launch to completion will be the shortest time possible. This is called MCT or Manufacturing Critical Path Time, and the shorter this time the better. Your ability to respond to customer order, reduce space, and a host of other benefits are related to reduced MCT.
BENEFIT 4: OPTIMIZED INVENTORY LEVELS
Notice that I didn’t use the word “minimized”. Short MCT and a pull-based material delivery system and supply chain will result in optimized inventory, following the guidelines: don’t run out and don’t have too much.
BENEFIT 5: IMPROVED PRODUCTIVITY
The concept of “flexing” is strongly emphasized in the Mixed Model methodology. If you don’t have work to do in front of you, move to where the work needs to be done (based on a clear set of signals, not randomly). Flexing is highly important in a Mixed Model environment, where variation in products and in product work content is much higher than with a dedicated line. It would not be unusual to find gains of 20-30% when workers are cross-trained and are willing and able to move to the work.
BENEFIT 6: IMPROVED WORKMANSHIP QUALITY
Mixed Model Manufacturing requires the practice of Standard Work Definition, documenting the best way that you know right now to do the work, but which can be improved in the future. This is the #1 thing you can do to impact quality, if you don’t have this already. In addition to Error-Proofing the work, operators in a Mixed Model line are also trained to do checks of their own work, and checks of work done at the prior workstation, with a method called Check-Do-Check.
These benefits are the types of improvements that not only flow to the bottom line, but also improve the quality of work life for your employees, by reducing stress and allowing them to do the job they were hired to do, instead of waiting or fighting fires. Notice that not all but many of these benefits are unique to the Mixed Model methodology.