Air gaging works according to a law of physics that states pressure and flow are directly proportionate to clearance, which then react inversely to each other. This means that when clearance decreases, air flow and air pressure also decrease and increase respectively. When clearance increases, air flow and air pressure will increase and decrease proportionately. This is usually accomplished by regulating air flow via some sort of restriction. Two common options include a jeweled orifice or a needle valve. With that in mind, one will be able to increase back pressure and reduce air flow by bringing the workpiece (the obstruction) closer to the nozzle. If the nozzle becomes completely obstructed, there will be zero flow. Regulated air and back pressure will also be at the same level.
What are Air Gages?
The first batch of air gages were developed in France by a carburetor company. Before World War II, the company wanted more reliable methods of measuring its carburetor jets. Back then, earlier versions of air gages utilized simple back-pressure technology and provided the basis for virtually all of today’s air-gauging styles. A U.S. patent was approved in 1943 and it allowed the design to make significant improvements. New air pressure regulators were incorporated into existing simple back-pressure systems.
Why is Air Gaging still Needed Today?
Air gaging provides a quick, easy, and reliable method of measuring highly polished, soft, thin-walled, and other materials that are susceptible to marking. In addition, it can be used to measure complex geometric tolerances, including matching, flatness, squareness, parallelism, taper, and diameters of components. In most cases, air gaging can also be used on workpieces that feature tolerances of 0.005 inches or less! What’s more, the repeatability and resolution of the measurement can be in the millionths of an inch. Since air gaging is a noncontact measurement method, it requires no special skills for the operator.
Another reason for the steady demand of this type of gaging is that a majority of today’s columns and measuring computers are an essential part of manufacturing cells. Those cells communicate with robotic loaders and need to send offset values to the machine. All in all, air gaging systems have a very long and dependable service life. It continues to improve as computer technology continues to evolve, remaining a viable measuring solution for generations to come.
Different Types of Air Gaging Systems to Keep in Mind
- Flow systems: Flow systems are measured and read in a flowmeter tube. It utilizes two masters for calibration and features an adjustable range of magnification. Flow systems are ideal candidates for measuring long holes such as gun barrels.
- Differential systems: Differential systems use a single master to set it to zero and divide the air stream into two fixed restrictions. Oftentimes, operators need to order this type of system for each particular magnification.
- Back-pressure bleed systems: Back-pressure bleed systems are versatile systems that can be configured with an air-pressure regulator. Since it can control the incoming air pressure, maximum linearity can be ensured. It uses two setting masters, which allow operators to compensate for any minor damage, dirt build-up, and wear to the tooling.