Today’s post is the first of a two-part series on cellular manufacturing. As in the last series on cycle time, much of what I will be presenting in this series is taken from my second book, The Ultimate Improvement Cycle—Maximizing Profits Through the Integration of Lean, Six Sigma and the Theory of Constraints.
Drawn-out distances and production times are often a function of location, location, location!
In many companies that I have visited over the years, it is not uncommon for products to travel great distances from machine to machine because of the equipment layout scheme. In one particular French company that produced pinions for things like turn-signal levers, the distance traveled was actually measured in miles! This was apart from the distance traveled to send parts outside the company for heat treatment.
Why so much cumulative travel distance?
The distance problem was manifested in the individual pieces of equipment used to produce the pinions (i.e. the turning, drilling, hobbing, grinding, reaming, washing, and crack detection machines) being set up as functional islands located throughout three different factories! (Functional islands are like machines that are used for the same function that are all placed in close proximity to each other in the same area of the plant.) Because of the equipment locations, it was not uncommon for the parts to travel back and forth between the factories as they made their way through the process sequence. This company also produced their parts in relatively large batches and waited until the transportation containers were full to transfer the parts to the next operation.
The deleterious effects of the protracted distance traveled and large batch sizes were prolonged cycle times that were proportional to both the distances and the sizes of the transfer batches. These long distances and inflated travel times translated directly into routine delays throughout the process. The ultimate consequences were late deliveries and missed shipments to customers. To make matters worse, when quality problems were eventually detected, it was not uncommon for very large numbers of defective pinions to be found. This required massive sorting and re-inspection of the parts.
Let’s do away with the large batch efficiency myth that has plagued manufacturing
The functional island concept for locating equipment was developed as part of the mass production mindset that still plagues many companies today. The impetus behind large batch sizes was the incorrect assumption that it was economically better to build as many parts as possible so as to avoid perceived costly set-ups. But as we have seen in the applications of Little’s Law and Ford’s EOQ model, large batch production can be a recipe for failure. We also know that there are better ways to run a business—namely one-piece flow or at least optimized batch sizes.
Coming in the next post
In the second part of this short series on cellular manufacturing, I will uncover the logic and positive effects of cellular manufacturing and one-piece flow.
Until next time.
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