Mini-subassembly borescope ensures integrity

Greg Reed, Contributing Technical Editor -- Test & Measurement World, 11/1/2005

For many automotive industry suppliers, testing products against regulatory standards is an integrated part of production. As a result of this need for advanced product testing, CAR Engineering, a multidisciplinary engineering and machine shop, has experienced a boost in requests for pre-tested products.

Recently, a manufacturer of remote visual inspection equipment asked the company to design a miniature-sized borescope with improved performance and efficiency. Used for detecting subtle irregularities within castings and complex assemblies, an optical borescope offers a nondestructive test mechanism that can ensure the structural integrity of a complex aircraft engine or can diagnose a simple cause of an automobile squeak. Smaller components often mean additional cost and loss of precision, so the challenge for CAR was to meet quality specs in a cost-effective manner.

CAR selected Kerk Motion Products as a partner for miniaturizing the borescope. The engineering backbone of the resulting borescope consists of Kerk's mini series of lead screws, which are made of 303 stainless steel. With its small-diameter lead-screw components, the mini series provides reliable precision motion control at as little as 1/10th the cost of miniature ball screws.

The new borescope uses four lead screws simultaneously, resulting in both a clockwise and counterclockwise direction within the subassembly, thus loosening one or two of the positioning leads and tightening the balance. This variability accommodates the high-load capacity, high speeds, and smooth motion necessary for the borescope's operation.

The borescope lens now provides 25% more articulation, and the size of the motion control subassembly has been reduced by about 50%. The final product is in its last build and is expected to be in full production, with about 2000 units annually, by April 2006.