Feature

Plastic perception — designing for failure

Tech basics for front office and shop floor personnel


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May 1, 2002 by Jim Anderton, technical editor


Among the many toolboxes I own, my “travel box”, i.e. the one I use for “Government jobs”, is a bright yellow polymer product with a grippy black handle. As I write this, however, the handle is on my workbench and the box, or rather its contents, are spread over the floor at my feet.

The box, which I have used for several years, is made by a large consumer plastics molder who shall remain, well, Rubbermaid. Before I continue, Rubbermaid products are as good as anyone’s, but my point is this: The product failed in a most spectacular way, causing much frustration and some language best left “on the floor”.

Why did it happen? Possibly because of the high weight of the stuff inside, which contained everything from multiple pairs of Vise-Grips to paper clips. Maybe because it’s old. The contents were heavy, damned heavy, and that particular box design has been around for a long time.

Was it defective? I doubt it, as it had served me well for years, and it has typically been filled almost to bursting. Why then, am I writing about it here? Mainly because “failures” in metal toolboxes are typically confined to hinges and hasps, and rarely deposit your stuff onto your safety shoes. This particular failure, experienced by a homeowner, would confirm the “plastic products are cheap” perception, regardless of the years of satisfactory service the product delivered.

Are your plastic products designed to fail? Of course not. But if they do, do they fail in a mode which is both safe and almost as importantly, expected by the end-user? Consumers have well researched expectations about product performance, but does anyone study their perceptions about the ways their products fail? I suspect that for applications where plastic parts and assemblies replace metals, part of perceived quality is the way the product ends its life as well as how long it lives. My yellow toolbox doesn’t owe me anything, and I like it enough that I’ll replace the handle. The new handle, however, will be steel, fastened by cap screws, “Nylock” nuts and fender washers. Perhaps if it had been made this way in the first place, the good reputation of plastic, and the toolbox itself, would remain intact.