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Copyright © 2000, MCB UP Limited
Design to fail
Design to fail
As our Guest Academic Editor, Professor Robert Messler points out in his paper "Trends in key joining technologies for the twenty-first century" (p. 118), the fundamental mechanisms for joining components together that we use today, were all developed over 2,000 years ago. Of course we have made some pretty impressive technical developments in areas such as adhesives and welding but the basic principles are rather old hat.
While reflecting on this situation it occurs to me that one aspect in which we have recently made progress in the field of joining is that products are now made with less components to start with. And so consequently less joining is required.
The countless gears and levers that comprised Babbage's first computer have now been replaced by a few silicon chips, and complex mouldings provide the enclosure and mounting brackets for electronic products; reducing an impressive parts list of screws, nuts, washers and brackets to a single item. As a child I used to derive great pleasure from taking things apart to find out how they worked and then struggling to remember how to put them back together again before their absence was discovered. These days the chances are that such exploits would be rapidly curtailed by the use of joining technologies that are not designed to allow the parts to be separated, and it is ironic that this trend should be advancing at the same rate as efforts into disassembly and recycling.
The advantages of reduced parts count are well established and our research paper "A team-based design for assembly methodology" (p. 162) describes a delightfully simple and yet sophisticated method for evaluating a products assembly and making improvements; many of which result in reduced parts counts and reduction in the number of fasteners. How then can we balance the needs of the manufacturer to make products as cheaply and reliably as possible, against our environmental concerns?
Fortunately our Guest Academic Editor's paper provides a clue in the form of adhesives that can be switched on and off. In the same way that UV light is now routinely used to cure adhesives (see article on p. 144) wouldn't it be wonderful if a different wavelength could be used to reverse the molecular bonds? Of course this approach does not need to be limited to adhesives. What about screws made from shape memory alloys that "remembered" they used to be smooth bored rods when subjected to a radio frequency heating? Or welds that fracture themselves when subjected to a resonant magnetic field?
Perhaps the next evolution within the field of joining technology will take advantage of the effects we have previously struggled to overcome, to form the basis of a whole new area of un-joining technology. Making friends of adversaries is well established as a means of making fundamental progress.