DIMENSIONAL METROLOGY BEYOND THE CMM

Computed Tomography takes inspection beyond the coordinate-measuring machine in reducing machining scrap and increasing throughput.

In the world of high-volume automotive cylinder-head production, the yields realized from casting processes count for a lot. Having to reprocess faulty heads is inefficient enough. Sending them through expensive post-cast machining processes, only to find that they are not up to standard, is an equal or greater cost. Late-stage rejection of any machined product because of sub-spec quality means that machining assets have been stranded, labor wasted, throughput slowed and product-to-market-fulfillment time lost.

Porosity is the main culprit in rejection of cylinder heads, whether aluminum or iron. All castings exhibit porosity. The real question is “how much” and “where?” Porosity control is very important in complex, thin-wall structures such as between water and oil carrying passages, and potentially less critical in thicker, less-optimized areas such as the engine block.