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Cylindrical coordinate measuring machines or CCMMs, are specialized variations of standard coordinate measuring machines (CMMs) that incorporate a moving stage to rotate the part relative to the probe.The probe moves perpendicular to the part axis and collects radial data at regular angular intervals.
Descriptions
A standard CMM uses a three-dimensional Cartesian X, Y, Z system where each axis is orthogonal to the other, whereas a cylindrical CMM omits the X or Y axis.The probe moves in only two axes (vertical Z axis and X or Y horizontal axis), and the rotating stage positions the inspection object (cylindrical part, hence the word "cylindrical" in the title) in a precise manner.Probes can be tactile or optical in nature.Optical detection methods include laser interferometry and telecentric lenses.
Coordinate System
The CCMM coordinate system differs from the standard Cartesian coordinate system in that it uses a rotating stage.For this purpose, a spherical coordinate system is used to define the axes.A complete definition can be found here:The cylindrical coordinate system allows construction of crankshaft gauges, transmission shaft gauges and inspection machines for other shaft applications.
Uses
Standard CMMs are good for prismatic parts, while cylindrical CMMs are great for cylindrical parts.Examples include camshafts, crankshafts, propshafts, and other rotating parts that are longer than their diameter.Parts whose length is less than their diameter are usually measured with a circular gage.
Technology
The method of recording the angular position of a part always uses an optical encoder.However, radial measurement probes can incorporate optical or tactile techniques.Optical technologies include non-contact laser interferometry or shadowing systems, while haptic systems use optical gratings.
Standardization
Standards similar to those used for standard CMMs also validate CCMM performance.The ISO 10360 series defines the characteristics of probing systems and length measurement errors:
PForm: Probe bias when measuring the shape of a sphere
PSize: Probe bias when measuring the size of a sphere
EUni: Deviation of sphere measured length from one direction
EBi: the left and right deviation of the measured length of the sphere
The ISO 10360 series consists of the following parts:
ISO 10360-1 Geometric product specification (GPS) -- Acceptance and verification tests for coordinate measuring machines (CMMs) -- Part 1: Vocabulary.
ISO 10360-2 Geometric product specification (GPS) -- Acceptance and verification tests for coordinate measuring machines (CMMs) -- Part 2: CMMs for measuring linear dimensions.
ISO 10360-7 Geometric product specification (GPS) -- Acceptance and verification tests for coordinate measuring machines (CMMs) -- Part 3: CMMs with imaging detection systems.
ISO 10360-8 Geometric product specification (GPS) -- Acceptance and verification tests for coordinate measuring systems (CMS) -- Part 4: CMMs with optical distance sensors.
