One of the chief tenets of lean manufacturing is the elimination of waste. Years ago the Toyota Production System identified seven kinds of waste that should be addressed and eliminated in lean manufacturing implementation. Three of these are directly related to the concept of “pull” production: overproduction, excess inventory, and unnecessary delay.
In traditional manufacturing, a “push” system of production, in which products are pushed along the production stream and finally outward, has historically been the norm. With a push system, manufacturers mass produced ahead of time, estimating and anticipating demand. Operating under this system frequently resulted in overproduction, excess inventory, and costly delays and waiting. When the demand isn’t there, idle inventory sits around consuming space and resources. In addition, unrealized demand also demands costly marketing campaigns to create an artificial demand.
The lean manufacturing term “pull,” on the other hand, denotes a production process that begins from the other end-the customer demand. Demand “pulls” the product along the production stream, thus reducing waste. The flow of resources in the process is regulated because there is now replacement of only what has been consumed and no more than is immediately deliverable. In this way, overproduction, resultant delays, and excess, resource-consuming inventory are avoided. And waste is eliminated or reduced.
An illustrative, though slightly over-simplified, analogy often used to illustrate the pull principle is that of a vending machine. The machine is stocked with snacks and sodas. Customers come along, put in their money, and make their selections. Later, the vending machine is restocked with only those items and in those amounts determined by customer demand. Consequently, there’s never too much of anything taking up valuable space in the machine and possibly spoiling.
Now, “customer,” within the context of lean manufacturing implementation in the pharmaceutical industry, means more than just the end user. It also encompasses downstream segments of the production process. The downstream “customer” demand pulls the product from the upstream segments, downstream activities signaling their needs to those upstream. This means, then, that there’s not too much anything at any time and people aren’t waiting. In the pharmaceutical industry, however, the difficulty arises in trying to adjust batch or blend sizes to accommodate the pull principle of lean manufacturing.
Further complicating things is the fact that there are three basic kinds of pull systems:
– The simplest, the “supermarket” or replenishment system, we saw in our vending-machine analogy. Here, material is replaced by upstream processes as it is withdrawn by downstream process.
– The sequential system requires less inventory, and so there’s less potential for waste. Basically, with this system, products and parts are made to order, which demands a keener eye on scheduling and high process stability.
– The mixed system is a combination of replenishment and sequential systems. These two systems can be applied selectively as process needs dictate or they can be used in tandem or both. This mixed pull system is best utilized when the 80/20 rule obtains.
The pharmaceutical industry, owing to these difficulties, has been a fairly late and sometimes half-hearted adopter of lean manufacturing techniques. But they can and have worked well in this industry. It just takes the guidance of good pharmaceutical consultants with industry experience in lean manufacturing implementation.