Within a metrology inspection environment, fixturing is a three-step process of positioning, locating and securing a workpiece within a measuring volume for inspection. Whether this inspection involves a coordinate measuring machine (CMM), vision machine or flexible gaging system, the goal of the fixture is to hold the part securely and repeatably. A well designed and manufactured fixture will remove operator variance and help to ensure consistency of inspection.
The true benefits of precise metrology fixturing and how it can significantly affect the efficiency of an inspection process are largely underestimated. It is commonplace for fixtures to be neglected until the last minute of a project, or even worse, forgotten altogether. It is only when a CMM backlog starts to build or metrology results drift that the focus is drawn to the part fixturing and positioning within the machine. By then, it is generally at the expense of lost time and money, and the costs of implementing suitable control measures retrospectively are increased. Within the productive process pyramid framework for process control, the post-process monitoring phase is the final step to ensure effective end-to-end metrology. It is within this phase that consideration needs to be given to the fixturing solution to maximize the effectiveness of a CMM, vision machine or flexible gage. There are many benefits that the correct use of metrology fixturing can bring to your inspection process. This article will focus on the top three considerations: repeatability and reproducibility, part positioning and productivity, and cost reduction.