Optical method for inspecting surface defects inside a small bore

Abstract

Most automotive powertrain parts made of castings have surface defects such as pores. However, detecting pores inside small diameter bores is a challenge because of the limited dimensional accessibility. Adding to this difficulty is the auto industry's desire to conduct the porosity inspection in-line, i.e. within the machining production cycle time of a part. A technique or equipment that meets these requirements currently does not exist. In order to meet these demands, it is necessary to develop an entire new methodology to inspect the inner surface of small diameter bores. This paper presents an innovative methodology to inspect the porosity of the inner surface of small bores and to provide their characteristics such as size and location. A prototype measurement system was built and tested in the lab. Experimental results showed the proposed method to be reliable and consistent.