Free analysis service proves a boon for design engineers
Where optimal joint strength is the main requirement, heat shrink bonding is a great solution. The heat in the assembly helps to create a rapid cure and the contraction of the outer component exerts a compressive load on the curing adhesive. The result is a total strength far in excess of the adhesive shear strength and the dry interference strength combined.
Heat shrink bonding is a technique most commonly used for joining steel to steel. It is also suitable, however, for joining dissimilar materials for which consideration needs to be given to differential expansion during service. And this is a field in which Henkel has considerable experience.
Henkel’s knowledge helped Ford to engineer a Loctite bonded solution that has saved costs as well as guarantee the required performance from the part. The process is now employed in the production of engines at Ford, Bridgend. The components of a shrink fit joint have an interference fit at working temperature but are assembled with a clearance. To achieve this, the outer component is heated and the other, to which the adhesive is applied, is kept cold. This was the method Henkel recommended to Ford for securing steel drive gear onto the steel crank to ensure no movement.
Henkel has many tools at its disposal to assist in finding the best process and adhesive product for the task including extensive laboratory and testing facilities both here in the UK and on mainland Europe. The company also has developed various software programmes for analysis, one of which was used widely for the Ford project and is available to all manufacturers contemplating a bonded solution.
The procedure is simple. Henkel inputs known information supplied by the customer and the programme calculates the unknown. So, by supplying the loads and performance required, Henkel is able to recommend the most appropriate substrate material and joint design. Alternatively, if the substrate is known, then the load which can be applied in specific environments can be calculated.
Other calculations could include minimum and maximum taper diameter, joint length, clearance and assembly temperature. In other cases details of the operating environment, temperature extremes, the continuous operating temperature and operating medium might be known but calculations involving tolerances are needed.
With more and more design engineers specifying adhesives in their original design, this free analysis service is proving invaluable for many companies. It helps to calculate the parameters of designs and as a consequence saves time and cost, ensuring that much of the testing work is completed before any metal is cut.
In Ford’s case, the service was an important element in proving the suitability of a special Loctite adhesive for the high strength bond. The product is optimised for the process and is now creating an instant bond between drive gear and crank that has all the performance qualities required by Ford.
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