Integrating a Vision System With a Coordinate Measuring Machine to Automate the Datum Alignment Process

Inspection is an important stage in the manufacturing process of machined parts. Coordinate measuring machines (CMM) have become more automatic, programmable, and capable of fulfilling the growing demands of inspection. However, fixturing (datum alignment) of parts is still done manually, consuming valuable inspection time. In this paper, we describe an automated datum alignment technique which integrates a vision system with the CMM to avoid part fixturing. The rough position of the part is estimated through image analysis. This initial reference frame drives the CMM through an automatic datum alignment procedure, thereby automatically establishing the reference frame without the use of fixtures. This technique has been demonstrated for two and a half dimensional (2.5D) machined parts with well-defined features that exhibit a stable position on a flat table.

End Milling of Elastomers—Fixture Design and Tool Effectiveness for Material Removal

This paper describes the machining of elastomers using sharp, woodworking tools and the machining of cryogenically cooled elastomers. Due to the lack of information on tool selection for elastomer machining, a set of thirteen tools that cover different sizes and tool geometries and materials was used in this study. Fixture design was found to be critical in machining of elastomers because of its relatively low elastic modulus. The cutting force created during machining can generate significant deformations in the elastomer workpiece. The finite element technique is used to analyze the structural stiffness of the elastomer workpiece under different geometric configurations. The effective stiffness is defined to quantify and compare the stiffness of elastomer workpiece machined by different tool sizes. The cleanliness of the groove machined by end milling is investigated. Use of some down-cut end-milling tools effectively removed the elastomer material at room temperature and generated a clean groove. The tool configuration and part fixturing are identified as the two most important variables that affect the cleanliness of machined grooves. Cooling the elastomer workpiece by solid carbon dioxide (dry ice) to about −78.6°C improved the machined surface finish.

Tool for Assembly Locating Scheme Definition

Locating schemes control the stability of a system, which has a major impact on the way variation propagates through that system and affects overall critical dimensions. The definition of the locating scheme should be made early in the design process in order to eliminate the need for costly modifications later on. This paper presents a tool that aids the designer in selecting the optimal locating scheme definition. It requires only the basic geometry of the components and is therefore easy to use early in the design process. The tool graphically indicates in which way the locating scheme should be modified to increase the stability of the system. The objective function for the stability of the system can be a number of defined critical dimensions or the general stability of all the components. The tool can be used for single part fixturing as well as for complete assemblies. Color coding is used to quickly identify sensitive areas of the assembly and as an easy way to compare different concepts. The use of the tool is shown in a number of examples.