Chris Koehn President Stotz USA Freeport, IL
www.stotz-usa.com
QualityScan A
ir gaging relies on a law of physics that states flow and pressure are directly proportionate to clearance and react inversely to each other. As clearance increases, air flow also increases and air pressure decreases proportionately. As clearance decreases, air flow also decreases and air pressure increases.
This is accomplished by having a regulated air flow that travels through some type of restriction such as a needle valve or jeweled orifice and then through the nozzle in the air tool. As the obstruction (workpiece) is brought closer to the nozzle, air flow is reduced and the back pressure is increased. When the nozzle is completely obstructed, the flow is zero and the back pressure is equal to the regulated air. Conversely, when the nozzle is open to the atmosphere, air flow is at a maximum and the back pressure is at a minimum. There are several varieties of air gaging systems: • The back pressure bleed system is the most versatile. Tooling from different air gaging systems may be used with this type. It is configured with an air pressure regulator to control the incoming air pressure to ensure maximum linearity. It is the second restric- tion that allows the user to adjust for different air gage tooling by adjusting the incoming air pressure to match the style of air tooling used. This type uses two setting masters to calibrate.
• The differential system divides the air stream into two fixed re- strictions. One side ends in a zero valve, which balances pressure to the fixed second leg of the system, which ends at the air ring or plug. The difference between these two legs is measured by a dif- ferential pressure meter that bridges the two legs. This type uses a single master to set it to zero. Tooling for this type of system needs to be ordered for each particular magnification. This system is not as forgiving with worn or damaged tooling because you are using a single calibration point. Any part not made near the zero is more likely to have an inaccurate reading.
• The flow system is measured and read in a flowmeter tube that supports a float. This system uses two masters for calibration. It is similar to the back pressure bleed system in its accuracy across the tolerance range. The range of magnification is adjusted by
10
ManufacturingEngineeringMedia.com | December 2013
Exploring the Usefulness of Air Gaging
changing flow tubes and scales and is not as simple as the back pressure bleed system. The flow system requires a much higher volume of air which requires much larger nozzles. Because the nozzles are larger, the nozzle must be kept closer to the part and therefore has a smaller nozzle drop. This can shorten tool life. The flow system can be used with long hoses without affecting the response time of the amplifier which makes it the ideal candidate for long holes such as gun barrels.
Air gaging is a very fast, efficient and reliable method of measuring. It is designed to be used on workpieces with tolerances of 0.005" (0.13 mm) or smaller. The resolution and repeatability of the measurement can be in the millionths of an inch. Because air gaging is a noncontact method, it is useful for measuring soft, highly polished, thin walled and other materials susceptible to marking.
Air gaging is a fast, efficient and reliable method of measuring—especially on work- pieces with tolerances of 0.005" or smaller.
Air gaging can be used to measure complex geometric tolerances such
as diameter, taper, parallelism, squareness, flatness and matching of components in a very fast and efficient method. These may not be able to be checked with fixed-limit gaging or may be costly and time consuming to check in a different way. The size of probes continues to get smaller and smaller and can now be as small as 0.6 mm in diameter. Many of today’s columns and/or measuring computers can become an integral part of the manufacturing cell with communication to robotic loaders and the ability to send offset values to the machine, which allows for around-the-clock manufacturing with 100% inspection of workpieces. Air gaging technology is continually improving as computer technol- ogy continues to evolve. These systems can range from simple desktop readouts to full SPC computers with contour scanning capabilities. As manufacturing requirements continue to become more complex, air gaging technology evolves to meet the demand. For these reasons, air gaging will remain a viable measuring solution for generations to come. ME
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84