Why Returnable Containers

Lean producers insistence on reusable containers with item-specific dunnage is puzzling to those who are not used to it, because it appears to be an unnecessary expense. Why not just use pallets and disposable cardboard boxes Single-use containers appear to be cheaper, even after including their disposal cost. Let us explore why it is not so. 

Returnable containers are made of sturdy plastics and contain item-specific dunnage that separates and presents parts to assemblers one by 

Returnable containers also play a role in regulating the flow of parts. We know how many returnable containers are in circulation, and this number places a cap on how much material is in the supply chain. The two-bin system and variations on it are examples of the use of returnable containers as pull signals. For most items, however, kanbans are preferred because they offer more sequencing flexibility. 

Whenever an assembler has to open a cardboard box, extract a part from a bag, or dispose of packing materials, the product waits. The need to make the assembly line productive justifies the investment in containers that present parts one at a time, unpacked, and properly oriented. The cost and work added in materials management can result in savings that are ten times larger in assembly. 

This explains why the containers must be customized, but not why they need to be returnable. Single-use, item-specific containers could be quite expensive, but using returnable containers means sending empties back to suppliers. Clearly, the economics of doing it depend on how far that is and, more specifically, on whether there are opportunities for return freight. 

Returnable containers are made of sturdy plashes and contain item-specific dunnage that separates and presents parts to assemblers one by one. The top shelf is slanted in the opposite direchon and used to return emphes. The main reason is that the containers used on the line side present parts to the assemblers, and the lean philosophy is that they must be designed for the assemblers convenience. In prachce, most plant managers view transporters and assemblers as equivalent, when in fact they are not. First, there are ten times more assemblers than transporters. Second, the assemblers are linked together in a chain of balanced operahons leading to shipment of a product. Each assembler is a bottleneck, so that each second added to an assembler job means one second added to the jobs of all the assemblers on the same line. 

This multiplier is not present with transporters, because they work in parallel. (This principle was described in Chapters 25 and 29.) 

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