Single-Composition Hemming Sealant Application for an Aluminium Alloy Hood

Abstract

Normal process is to use a two-composition hemming sealant for an aluminum alloy hood. The hemmed hood assembly then needs to be cured using high-frequency curing equipment. The curing process can help to solve quality problems such as, hood distortion and mismatch between inner/outer parts during the manufacturing process. The equipment required for the application of two-composition sealant and high-frequency curing is very complex and expensive. The sealant application process is also very difficult. In order to reduce cost, investment and area footprint requirement, we needed to develop a single-composition hemming sealant for a new and future product. After investigations and trials using a two-composition hem sealer we were able to establish the technical and performance requirements of a two-composition sealant. Using the same process we established the performance of a single-composition sealant by undertaking trials offline with the same parts. From these results and working closely with a sealant manufacturer, a project was undertaken to develop a single-composition hemming sealant for use on aluminium alloy hoods that meets the technical and performance requirements of the two composition material. For overcoming any possible mismatch between the inner/outer parts of the product, we requested the new sealant included glass beading. After finishing further trials using the new sealant material, we commenced testing on aluminium hoods for our new product. The function tests included bench test, GTR test and on road test. The test also included quality checks for hood surface distortion, panel mismatch between inner and outer panels and part dimension. The aluminum alloy hood is hemmed by using a press machine and hem die, this type of hemming process can assure that the glass beading can be forced into the surface of aluminium alloy. The result of our experiments indicates that the single-composition sealant can meet the requirements of vehicle function and manufacturing process. We decided to commence using the new single-composition sealant for all aluminium alloy parts on our new and future products. This negated the need the expensive curing equipment and process. This technology has been in use on our product for more than 6 months. We have gained several benefits and experience from using this new technology. (1) Reduced equipment investment, circa 3512900 RMB. (2) Cost per car reduction of circa 10 RMB per vehicle. (3) Equipment failure ratio and running cost have been reduced considerably. (4) Environmental benefits. The curing process emits fumes into the atmosphere. Finally we have a quality product at a reduced cost, this is very important due to the high level of competition in our business.

F2012-H01-003