A secure bond for engine production

Oct 3, 2012 | Fasteners & adhesives

Through a relationship spanning forty years, Henkel has become Ford’s preferred single source supplier of industrial adhesives and sealants for engine production throughout the world, with the most recent applications being on the new Volvo S16 engine

Becoming a preferred single source of adhesives and sealants for Ford engines is a great accolade for Henkel, the manufacturer of the Loctite brand, and testimony to the performance of its products. 

It is, however, the result of Henkel’s focus on customer support that allows companies such as Ford to continuously push the boundaries of technology and gain competitive edge.

Shrink bonding

Many applications at Ford exemplify this continuous development partnership – two of which involve the Volvo S16 engine which Ford manufactures at its plant in Bridgend.

A design upgrade on this short, six cylinder engine, required a drive gear to be shrink fitted onto the crank to carry higher torque. Laser welding was a clear option but would have involved considerable capital expenditure. Bolting the drive gear was another consideration, but that would have increased overall weight and size of the engine. So, Henkel was asked to assess the suitability of bonding the structures – and this involved a considerable amount of testing and finite element analysis.

Heat shrink bonding is a technique that has been used in the automotive industry for many decades, and is the technology that Henkel calls on when maximum joint strength is the overriding design criterion.

The company’s specialist, Bob Orme, explains: “It is a more costly bonding process than room temperature assembly as energy is involved, but it is often a superior alternative to mechanical fixing.  It provides very high strength without adding complexity to the design and extra weight.”

A similar method is cold shrink bonding. This is widely used in the construction equipment sector for applications such as bonding the bearings between the arm sections of a mechanical digger.  In this instance the interference fit bearing sleeve is cooled down with liquid nitrogen to create a slip fit during assembly. As the parts return to ambient temperature the interference returns and compresses the adhesive.  The technique has also been used in the white goods industry on heavily loaded bearings.

Henkel recommends its Loctite 128467 product whose cure speed has been optimised for shrink bonding, so it was the natural choice for the Ford application too. For the drive gear application it provided an instant bond that ensures the gear does not move throughout the service life of the engine.  Furthermore, it does so without the need for major redesign, large capital investment or the risk of introducing stress in the crank.

Design savings

Another cost saving on the Volvo S16 involved the potential redesign of a mid-shaft bearing. To achieve the strength needed to prevent bearing spin and resultant wear, an increase in wall thickness was originally proposed, but this would have increased the weight and cost of the component.

Henkel suggested maintaining the lightweight housing and slip fitting the bearing using a retaining compound. However, as the Ford rule dictates there should be no possibility of adhesive migrating into the bearing, Henkel turned to its non-run Loctite 121078 thixotropic adhesive to eliminate bearing spin and fretting without risk of stressing the housing.

Retaining compounds have considerable scope of application across industry, saving both time and cost. They are used in cylindrical assemblies to bond one part that is inserted into another. Applied as liquids, these compounds not only cover the area of the components to be joined but also fill in all the surface irregularities, however minute they may be.

As the surfaces are brought together and the air excluded, the adhesive begins to harden to form a tough plastic, which bonds the parts securely. The adhesive provides 100% contact to seal the area which prevents any moisture entering the  joint. Fretting is eliminated, joint strength increased and worn parts can be reclaimed.

Simplified design

Retaining compounds can be utilised for standard slip fits, removing the need for circlips or clamping plates. In addition, stress concentrations can be decreased. With the absence of these parts and the reduction of stress, many design and production processes can be simplified, resulting in cost savings and faster production processes.

For too long, adhesives were seen as relatively low-tech products that simply make things stick together and were only considered when other methods were deemed unsuitable. That stigma has long since disappeared and now designers and engineers – such as those at Ford – consider adhesives right from the concept stage.


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