Unit -3
Advances in Metrology
Multiple features The more the (both number of features dimensional and geometric) that are to be controlled, the greater the value of CMM.
Flexibility It offers flexibility in measurement, without the necessity to use accessories such as jigs and fixtures.
Automated inspection Whenever inspection needs to be carried out in a fully automated environment, CMM can meet the requirements quite easily.
High unit cost If rework or scrapping is costly, the reduced risk resulting from the use of a CMM becomes a significant factor
CMMs can be classified into the following three types based on their modes of
operation:
1. Manual
2. Semi-automatic
3. computer-controlled
1. A programming software directs the probe to the data collection points.
2. Measurement commands enable comparison of the distance traversed to the standard built into the machine for that axis.
3. Computational capability enables processing of the data and generation of the required results.
Applications
Principle
Four types of machine vision system and the schematic arrangement is shown
1. Image formation.
2. Processing of image in a form suitable for analysis by computer.
3. Defining and analyzing the characteristic of image.
4. Interpretation of image and decision-making.
Vidicon camera
Solid-state camera
Image processor
Optical Sensors
Tactile sensors
Following are the benefits or advantages of Laser:
1. High repeatability
2. High accuracy
3. Long range optical path
4. Easy installations
5. Wear and tear
There are two types of laser interferometers: homodyne and heterodyne. A homodyne interferometer uses a single-frequency laser source, whereas a heterodyne interferometer uses a laser source with two close frequencies.
where the Δf term is due to the Doppler shift.
Reference: