P09233Vibration Dampening Material Selection 04/30/09
Four different vibration solutions were chosen for the box and its components. Each vibration dampening type was chosen for specific components. First in order to select the proper way to vibration dampen a component some back ground about vibration dampening is needed and what choices one has when selecting vibration dampening materials. To vibration dampen an object you need to place something between the object you with to isolate and its surroundings. Some ways to do this are with springs (mechanical and air), foam, and rubber. Springs were too large and took up to much space to be a viable option for our project so we narrowed our selection to vibration foam and rubbers.
When selecting vibration foams and rubbers there are many options to consider, the first being foam or rubber. Rubber is good for shock absorption, insulation, and sealing because it is strong, stretches, and bounces back. Foam can be made from rubber or plastic that is not completely solid. It contains cells of air making it very lightweight and good for gasketing, sealing, and cushioning applications. To help narrow the selection we next looked at compression recovery. Compression recovery is the ability of the material to return to its original shape after its been compressed. This was considered to be important because it allows the material to return to its original thickness after absorbing a fall or some other shock allowing it to be reused. For all of the chosen vibration dampening materials compression recovery was chosen to be either good or excellent. By choosing these options the type’s material was limited polyurethane rubber or foam. The next category of consideration was how soft the material should be. For foams softness rating range from 0-25 and rubbers range from 20-75. Selecting the softness was kind of arbitrary. For foams a softness of 1-4 seemed way to low so we looked mostly at 5-8 softness ratings, and for rubbers we mostly looked at softness ratings of 35-75.
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We then decided what method we would like to vibration dampens each component. For the box its self a sheet of rubber or foam was chosen to separate the top of the box from the plane and rubber grommet for the top of the bolts and the top of the box.
Dampen vibration and isolate and reduce shock and motion in motors, fans, blowers, actuators, circuit boards, and other electromechanical equipment. All ribbed grommets and bushings have eight ribs for added flexibility (unless noted). Unlike grommets, bushings can work with a range of hole thicknesses. Use ribbed bushings with flat ribbed rings to fill space between bushing and equipment surface.
High-damp PVC absorbs vibration quickly, has a high displacement of energy, and less rebound. Durometer is 56A. Temperature range is 55°to 105°F. Color is blue. Low-damp TPR (thermoplastic rubber) absorbs vibration more slowly than high-damp PVC, has a low displacement of energy, and more rebound. Durometer is 57A. Temperature range is -40°to +122°F. Color is black.
The chosen grommet were High Damp PVC because they of their fast absorption rates.
For every other application either vibration foam or rubber sheets were chosen do to their adaptability and because the grommets did not come thin enough. The foam and rubber can be purchased with an adhesive backing so that it can be permanently place in the box while the inside components can be taken in and out with ease. Vibration dampening materials are also important to help keep the wires from coming off, as it reduces the vibrations that reach each sensor and its connectors.
We in the end decided to by the vibration dampening grommets, as well as three vibration dampening foam. We chose foams with softness ratings of soft and one with a softness rating of firm by a mistake in the ordering. The firm foam can still be used just for a different purpose. These materials were very inexpensive so if we find that certain softness ratings are not very good it would not be too difficult to select a different softness rating and material.
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