Accuracy of replica materials when measuring engineering surfaces

This paper presents a comprehensive study of three different materials used for surface roughness replication on five different types of machined surfaces. Steel sheets (electron beam texturing and shot blasted texturing), a cylinder liner, a crankshaft and a face-ground surface. The three different replica materials used were Araldite, Microset and Technovit. The surfaces were measured with the non-contact WYKO interference instrument, zoomed to relocate the same area on the original and on the replicas. Finally, three-dimensional surface parameters were calculated to compare each replica with the original surface. The results show that all materials are possible to use in order to measure and calculate three-dimensional surface parameters, but they have some peculiarities. The three replicas all show good accuracy on all surfaces, with deviations <10%, except for the crankshaft. Only Araldite and Technovit occasionally show Sz values that are >10% too high due to a small number of pores in these materials. Replicas in the Microset material in general show somewhat lower parameter values than the original surface. All replicas showed some problems on the fine-ground crankshaft with an enlargement of the fine structure, resulting in parameters ca 20% too large. The deviation of surface parameters on repeated measuring on replicas is considerably larger than on repeated measuring of the original surfaces. (C) 2001 Elsevier Science Ltd. All rights reserved.