A Coordinate Measuring Machine (CMM) is a highly sensitive instrument, used mainly for quality control applications, that locates point coordinates on three dimensional structures. A CMM measures parts down to a fraction of an inch and must be properly maintained and protected to ensure that accurate measurements are achieved. A CMM contains many delicate air bearings on which the measuring arm floats. Oil, moisture and particulate matter are commonly found in compressed air and can be extremely harmful to a CMM, often resulting in “drag” or resistance in the air bearings leading to hysteresis. These contaminants can also cause condensation and rust, resulting in poor machine performance and inaccurate measurements. Correcting the damage caused by contaminated compressed air is costly and requires production downtime.
The best way to protect a CMM from oil, moisture and particulate matter contained in compressed air is to install an air dryer/coalescing filter combination upstream of the CMM. Several different types of air dryers are available including membrane dryers, refrigerated dryers, chemical dryers and desiccant dryers. Choosing the Right Compressed Air Dryer for Your Application
A membrane air dryer with a high efficiency coalescing filter is a smart choice for CMM applications. Membrane air dryers use specially formulated membrane microtubes that are selectively permeable to water vapor. The microtubes provide an excellent medium for producing dry air from standard compressed air. As the compressed air travels along the length of the membrane, water vapor diffuses through the membrane, producing clean, dry compressed air at the outlet. A small fraction of the dry air is then directed along the outside surface of the membrane to sweep the moisture-laden air away from the membrane. The illustration above shows how a membrane dryer operates.
Membrane dryers can reduce the dew point of compressed air to as low as -40°F/°C, and are designed with no moving parts and no requirement for electricity. They operate with very little noise output - just a small amount of purge air is emitted through small exhaust ports. Membrane dryers require minimal maintenance and are inherently explosion proof. They are ideal for water sensitive applications, remote areas, explosive environments, sub-freezing environments, and applications requiring a consistent dew point.
Read this marketing application for more information on membrane air dryers for coordinate measuring machines.
This post was contributed by Judy Silva, Compressed Air and Gas Technology Blog Team Member, Parker Hannifin.