Metrology, Sensors and Control

This chapter focuses on metrology, sensors and controls for micromanufacturing. In general, a variety of sensors are employed in micromanufacturing. Many of them are used for metrology, and in particular dimensional metrology. Most are used on production machines to provide feedback during production. Few metrology systems for process and product control are available. The sensors and metrology systems available for product and process analysis are, in general, slow and not readily implemented. From a metrology and sensing perspective, the currently available systems are mostly two-dimensional in nature. Most of the measurement systems are fairly slow, which makes them suitable for R&D as their measurement speed limits their utility on actual production lines. Controllers fall into two architecture categories, open and closed (standard computer numerical control (CNC) controller architecture). In most cases, commercially available systems employ more traditional closed architecture controllers, while research and development teams tend to use open architecture systems. For most manufacturing systems, process control is a desired capability. In many cases it is achieved by measuring parameters from both the process and the product and adjusting process parameters to improve the quality of the part. In general, this approach is far from being achieved in the micromanufacturing field as the actual measurement of part and process parameters in realtime is limited to a few very special instances. Furthermore once a measurement is made, the process must be tuned according to the process model. In most cases, such models do not exist. Thus, in order to effectively achieve process control and quality enhancement, improved real-time metrology systems and sensors are needed along with models that accurately describe the various manufacturing processes at the micro level such that true process control can be enabled.