Forming-induced Gloss Reduction of Coil Coated Sheets for White Goods

In the household appliance industry piecework coating of body components has been successively substituted by usage of coil-coated sheets. For components with low strains or components not visible for the customer and therefore with no requirements concerning the visual impression these organic-coated materials bear a proper possibility for cost savings. But besides that, for high quality household appliances there are high visual requirements on the front panels. Already the gloss reduction of the coating layer due to higher strains restricts the application for front panels in most cases. From an economic point of view the application of coil-coated sheets even for these components is highly demanded. For an acceptable substitution the resulting paintwork properties after the forming process should be able to forecast within numerical simulations. Therefore the forming-induced gloss reduction of the respective coated material has to be determined in a proper manner.This paper deals with analyses concerning the forming-induced and strain-state-depending gloss reduction of a coil-coated material commercially used for white goods components. The investigations include measurements of strains and gloss by using an in situ approach. For that purpose, material specimens are formed using a modified experimental setup referring to the Marciniak-Test (ISO 12004-2). A fundamental advantage of the in situ measurements is a minor demand of experiments together with a high resolution of the measured variables. In conclusion, based on the experimental results a conceivable forming limit criterion is defined and integrated in an exemplarily simulation model. The front panel of a front-loading washing machine is used as a practice-oriented application example. Using of the pursued approach improper gloss reductions on the formed panel can be predicted within forming simulation.