![]() For 3, 3+2, and 5 axis machines, probes are routinely calibrated using traceable standards and the machine movement is verified using gauges to ensure accuracy. 00005 inch (half a ten thousandth) over the entire measurement volume. Typical probe repeatability can result in measurements of within. For a CMM using a touch probe, this relates to the repeatability of the probe and the accuracy of the linear scales. The accuracy of coordinate measurement machines are typically given as an uncertainty factor as a function over distance. These machines are available as stationary or portable. Data collection and reduction system - typically includes a machine controller, desktop computer and application software.The increasing trend towards scanning also requires the CMM Z axis to be stiffer and new materials have been introduced such as black granite, ceramic and silicon carbide. Few CMM builders today still manufacture granite frame CMM due to market requirement for improved metrology dynamics and increasing trend to install CMM outside of the quality lab. Today all the major CMM manufacturers build frames from Granite, aluminum alloy or some derivative and also use ceramic to increase the stiffness of the Z axis for scanning applications. Granite and steel were used in the early CMM's. The material used to construct the moving frame has varied over the years. The main structure includes three axes of motion.for GD&T such as roundness, flatness and perpendicularity can be assessed.Ĭoordinate-measuring machines include three main components: They can also be used to construct geometric features such as cylinders and planes etc. The measured points can be used to verify the distance between features. The points can be measured either manually by an operator or automatically via Direct Computer Control (DCC) or automatically using scripted programs thus, an automated CMM is a specialized form of industrial robot.Ī common use of CMMs is in manufacturing and assembly processes to test a part or assembly against the design intent. This process is repeated as necessary, moving the probe each time, to produce a "point cloud" which describes the surface areas of interest. When the probe contacts (or otherwise detects) a particular location on the object, the machine samples the axis position sensors, thus measuring the location of one point on the object's surface, as well as the 3-dimensional vector of the measurement taken. Each axis has a sensor that monitors the position of the probe on that axis, with typical accuracy in the order of microns. The typical 3D "bridge" CMM allows probe movement along three axes, X, Y and Z, which are orthogonal to each other in a three-dimensional Cartesian coordinate system. In addition to moving the probe along the X, Y, and Z axes, many machines also allow the probe angle to be controlled to allow measurement of surfaces that would otherwise be unreachable.Ĭoordinate Measuring Machine Description ![]() ![]() CMMs typically specify a probe's position in terms of its displacement from a reference position in a three-dimensional Cartesian coordinate system (i.e., with XYZ axes). Depending on the machine, the probe position may be manually controlled by an operator or it may be computer controlled. Various types of probes are used in CMMs, the most common being mechanical and laser sensors, though optical and white light sensor do exist. JSTOR ( September 2009) ( Learn how and when to remove this template message)Ī coordinate measuring machine ( CMM) is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe.Unsourced material may be challenged and removed.įind sources: "Coordinate-measuring machine" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification. ![]()
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