Casting produces a lower strength product than wrought processes as the cast microstructure can be porous unless the process is designed and managed correctly. There are casting methods to reduce porosity......centrifugal, vacuum, pressurised etc. The castings would then be machined where needed to a final size/ tolerance. That can expose sub-surface porosity to be opened up. There should then be an inspection stage to detect problems and allow suspect batches to be isolated and further checks done. Critical components would be 100% inspected rather than sequential sampling in a sampling plan. For example, investment cast jet engine turbine blades 100% with potentially high reject levels. Having a strong process control is essential. Make it simple to do correctly and difficult to stray from correct practises. The TVR story told in an earlier post is, unfortunately, “old school uk manufacturing attitude”. Remember the Harvey-Jones Morgan tv program years ago? They all do that, sir. Oh! The joys of setting up inspection systems and getting the message across from factory floor to boardroom! I dealt with HMRC for Tobacco duty. Huge £££££ sums involved. Teaching some of their auditing people was fun. Sampling plans based on standard accepted statistical methods.
