These are the systems which are used to measure a number of dimensions simultaneously. Part to be gauged are compared with a setting master which simulates the component. The feature gauged could be external/internal diameters, lengths, straightness, squareness ovality, run-out of faces, etc. The measuring head gauging fixture is specifically designed to suit the component to be measured and may be completely special or it may be built using a series of modular elements. It contains the means for sensing the dimensional difference between the components and the master which may take the form of mechanical or electronic probes or air jets connected to the means for amplifying the difference. The amplifying and display of readings may take the form of dial gauges or some form of electronic or air/electronic system. Displays can be analogue, digital or graphic and may be augmented by out of tolerance indication. Using electronic differential methods, the relationship between different features can be related to a common datum. The choice of system depends on number of factors like initial cost, dimensional tolerances of the features to be measured, complexity of the component, complexity of the features to be measured, number of features to be measured, speed of measurement required, skill or otherwise of the user. The reasons affecting the choice of displays are given below :
*(i) Pointer displays*—best where a rapid check run-out or concentricity is required.
*(ii) Columns*—natural choice where a considerable number of dimensions are involved. These are fastest and most convenient form of displaying the readings for every dimension.
*(iii) Digital*—provides high accuracy over a longer measuring range and best for situations where it is required to work in drawing dimensions. Can be viewed without strain over longer distances.
*(iv) Graphic on VDU*—the most sophisticated display essential when statistical process control systems are employed. Systems capable of dealing with very large number of interrelated dimensions can be developed. Automatic inspection machines incorporate both automated loading hopper, magazine, pick and place robot and—automated segregation of inspected components. Automatic inspection is essential where the complexity of the component is such that manual methods can not achieve the desired levels of accuracy. The results of inspection could be fed to electronic computer based system which may also control the machine operation. The use of such computer based processing also allows the results obtained to provide a wide range of control facilities including feedback for control of the manufacturing process. Coordinate measuring machines accommodate multi-dimensional inspection by using a single point contact to take successive measurements over the component profile. The contact movement and processing of the dimensional information is under computer control, which can also provide similar facilities to those offered by multi-point gauging.
Types of Multi Gauging
1. Multi Gauging System
2. Air Multi Gauging System
3. Automated Gauging Systems
4. Computerised Gauging System