prototypes

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Designed to Fail

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In this age of high tech, computer based design. A growing problem is becoming obvious to us here at Clevedon. As you know, whilst we do some very clever cold forgings and self-piercing products, our main business is based on the humble rivet. Solid Semi-Tubular and Fully tubular rivets. Some of you reading this blog may not even know what these products are or will confuse them with “pop” or other blind rivets

Therein lies one of the problems with modern design techniques. A confluence of two factors, demise of “old style” apprenticeship’s where some of our best engineering talent learned their trade and the rise of the computer savvy, iPad literate younger generation, many young designers have not been taught some of the most basic, fundamental engineering techniques.

This is not their fault, most CAD systems are great at producing designs drawings. Unfortunately, only certain techniques are included in the various wizards and “look ups” which mean that only certain outcomes will be produced.

Quite often these unintentionally, pre-defined outcomes are very difficult to productionise and more importantly very costly to manufacture.

We have had experience of being told by very well meaning designers that our suggested fixing proposal will not work because their Finite Element Analysis (FEA)testing show that the rivet will fail at a particular load. This despite that fact that in our long history (we began business in 1939), we have never encountered a failure mode of the type the FEA predicted would happen. To prove the point, we undertook practical testing to discover what happens in actual practice. The rivet did not fail.

Drawings are sent to us where in order to realise the designers dream, the product needs to be turned, milled, drilled, ground etc.  Each operation results in expensive individual set up and run times and thereby the final product is very costly to manufacture, at which point some very innovative designs are dropped because they do not make economic sense to peruse.

Powder printed samples are very good straight off the CAD system, but are incapable of predicting that the whole project will fail due to the lack of basic engineering input at the beginning. The old adage rubbish in, rubbish out, still holds true. All of these very sophisticated, technologically advanced  CAD and FEA systems all have the same fundamental, inherent weaknesses and results in the waste of large amounts of time, money and company resources, to say nothing of the potentially game changing design concepts that never come to fruition.

Here at Clevedon (the parent of Clevtec) we do not claim to have all the answers, but we are very good basic engineers. Having had to fight against overseas competition that has destroyed many good UK engineering companies we do have a very good track record in providing low cost, practical, innovative solutions to seemingly intractable design issues.

For the above reasons we have introduced a “Design Support Agreement” to work with designers to put some of the practical elements back into the design process that don’t come straight out of the can. We have found this has the most beneficial effect when we are involved early on in the design cycle but have also been able to re-engineer designs that have got into difficulty (usually cost difficulties).

Please contact us and ask for Steve Hardeman and we will very soon be able to let you know if we are able to help.

Engineering 101

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Riveting is one of the oldest forms of fastening

Solid rivets have been found dating back to the Bronze Age (ended 800BC)

You will have seen rivets hidden in plain site on bridges, ships, Aircraft and Trucks to name but a few common applications

 

bridge

 

Rivets are formed by a process called Cold Forging, this process produces no waste as the head of the rivet is formed by upsetting the shank of the rivet. This ensures the grain flow of the material remains in-tact thus strengthening the fastener.

The rivets are inserted in the material to be fixed together and “set” by deforming the end of the shank of the rivet to product a permanent fix

rivet 1

 

The more popular, semi-tubular rivet is set in a similar way but require a lot less setting load and provides a “Clinch” fix which pre-stresses the material

rivet 3

Many engineers are unaware of the advantages or even the function of rivets, tending instead to fall back on threaded fasteners which are more widely available.

The most recent development in Riveting is the self-piercing rivet, where you do not need a hole in order to rivet two materials together. This process is now commonplace in state of the art automotive manufacturing plants. JLR being pre-eminent in this regard

Self_Piercing_Rivets_sketch[1]

The process used to produce these fasteners has been developed in order to use the same manufacturing technique, cold forging, but to enable finished components to be forged outright, with the same benefits, no waste and a very strong structural integrity

forg 1

 

We are happy to help customers or prospective customers with any queries that may have regarding riveting or cold forging. We have recently helped a number of companies by producing and riveting prototype designs for them.

We have been in this business since 1939, over that time we have provided innovative, low cost solutions to many fastening and cost reduction requirements, thrown at us by our customers.

In the first instance, contact me, Steve Hardeman either by e-mail (steve@clevedon-fasteners.co.uk ) or by telephone on +44(0)121-378-0619