Eliminating finishing errors in powertrain finishing

Quality control for surface finishes on automotive camshafts and crankshafts is paramount in manufacturing. This is the last step in the part production sequence and one of the most critical to ensure extended lifetimes and low maintenance needs for engines. North American manufacturers have made great strides in quality improvement, in part by focusing on this important process.

Along with continually improving micro-finishing products, emphasis has been put on error-proofing or mistake-proofing the manufacturing process to eliminate human error. Poka-yoke, the Japanese term for this, is an important mechanism in lean manufacturing processes. There are three distinct methods used to eliminate product application errors and draw attention to operator mistakes in powertrain surface finishes.

The use of different core sizes in the rolls of micro-finishing film, based on the width requirement of the film being used, is the first method. Different widths may be required, due to surface width variations within the same part – main bearing surfaces, seal surfaces, pin bearing surfaces, or cam lobe surfaces. The list of different core sizes has grown as surface finishing requirements have changed and now come in eight common sizes ranging from 0.5" to 3.0". A different core size for each width ensures that the proper product is placed in the machine at each location for the specific part feature being polished. It is common to have 10 to 15 rolls loaded in one station in a machine, to polish all the necessary features of the part.

Second is the use of different color media, or backing layer of the microfilm product, based on the grit size of the grain used for polishing. Different part features may require different grit sizes, due to varying surface finish requirements. Additionally, there are often roughing, intermediary, and finishing operations on the same surfaces, each requiring a different grit size. As a result, a color code has been established for eight of the commonly used grit sizes: 9µm, 15µm, 20µm, 30µm, 40µm, 50µm, 60µm, and 80µm.

Loading abrasive material into the machine with the correct side of the microfilm layer coming in contact with the part surface is the third method. This is particularly critical for the smaller grits used, as it is not obvious to determine visually, or by touch, which side is the abrasive layer. Materials are ordered either abrasive side in (ASI) or abrasive side out (ASO), depending on how they are wound in the machine, and part information is embossed on the side of the microfilm that does not contain the abrasive layer. Markings usually include the trade name, product designation, and grit size.

Norton/Saint-Gobain Abrasives Inc. has incorporated error-proofing methods into its new Norton Finium line of abrasive microfinishing film rolls. Finium rolls are used in powertrain polishing operations in the automotive, truck, marine, small engine, and very large engine manufacturing operations.

Norton/Saint-Gobain Abrasives Inc.
www.nortonabrasives.com
IMTS 2014 booth #N-7051

About the author: Gordon Witte is an ap- plications engineer at Norton/Saint-Gobain Abrasives. He can be reached at Gordon.R.Witte@saint-gobain.com.