Process Fingerprints
Dr. Shih provided an example of a process fingerprint for batch intensive mixing. He proposed that the mixing torque as a function of time was an appropriate fingerprint for this process. Although not ideal, this measurement generally satisfies the requirements listed above. Many laboratory and some manufacturing batch intensive mixers are fitted with a torque transducer or power gauge to measure the mixing torque (or power) for the process. The mixing torque is sensitive to many of the key process parameters (rotor speed, rotor geometry, temperature, component addition protocol, etc.) as well as many of the key material variables (composition, component concentrations, component rheologies, etc.) For particular material systems, there are strong relationships between the torque profile and and product quality. This is probably the weakest link in this example, and in general the most difficult requirement to satisfy. One of the problems is that performance characteristics of the resulting material are not necessarily uniquely determined by the torque profile. The torque profile is linked to fundamentals such as morphological changes, chemical reactions, etc.
Consider instead the reaction injection molding process for a polyurethane. Propose a "process fingerprint" for this process. Explain how your proposed measurement does (or doesn't) satisfy the four points listed above. |
