Vibration Absorbers

The vibrations produced from the operation of certain kinds of processes and equipment can be a hazard to nearby objects. Therefore, items such as rubber pads, engine mounts, bushings and shock absorbers are used to reduce the transfer of energy between a machine and its components or outside environment by placing them between the floors and vibrating equipment to both reduce the noise of equipment-floor vibrations and to eliminate the risk of equipment damage. Vibration absorbers, or vibration isolators, also help to minimize the noise produced from engineering and mechanical operations. In addition, they provide vibration control and energy absorption for both small and large heavy-duty applications. For sensitive measuring equipment or control panels, even gentle vibrations could adversely affect the output of the machines. Hydraulic shock absorbers tend to provide the most powerful protection from jarring shocks and vibrations, leading to their common application in motor vehicles and precision equipment.

Elastomeric rubber bumpers, or rubber mounts, are mounted between two pieces of machinery to prevent vibrations from transferring through metal-to-metal contact. Consistent contact between two rigid parts results in expedited deterioration and therefore higher maintenance, repair and replacement costs. In order for a mechanical system to be its most cost effective, it has to be operating at its highest output which can often be affected by the amount of vibration caused. Through vibration damping methods, machines can run at higher speeds, and as improved linear deceleration can be achieved, higher processing rates will result in higher outputs for the manufacturer. In addition, cars, trucks and other moving transportation vehicles use nearly every type of vibration absorption available to protect numerous parts within the engine and vehicle chassis from vibration and shock damage. Shock mounts and vibration mounts are commonly used to absorb jolts and bumps from the traveling surfaces and to prevent damages and discomfort to those in the vehicles. Molded rubber engine mounts are particularly crucial because the engine is a large source of vibration, and the metal-to-metal vibrations between the engine and the car body would quickly damage the engine. Rubber mounts are also used in industrial areas to prevent contact between vibrating machinery and other surfaces.

Rubber is a commonly used material in the vibration absorption process as it holds many elastic properties which enable it to absorb large amounts of kinetic energy with minimal rebounding energy. It also provides excellent slip resistance and so rubber bumpers, pads and mounts can also be used to further secure equipment and machines and to prevent their movement as a result of vibrations. Natural and synthetic rubber materials such as butyl, EPDM, fluoroelastomer, nitrile, neoprene and silicone are used in applications specifically requiring various characteristics of heat resistance, chemical resistance and hysteresis. Other vibration absorbers rely on different qualities to create a smoother operation. Hydraulic shock systems for example are composed of a cylinder and piston rod with a hydraulic fluid of sorts. These are commonly used in vehicles to prevent jolts and bumps from the road disturbing the interior of the vehicle. The shock impact the piston rod which is forced into the hydraulic fluid. The fluid absorbs the kinetic energy and transfers it into heat energy which is then dissipated. In this way, a minimal amount of energy from the initial jolt reaches the vehicle itself. Pneumatic air shocks work in a similar way using air instead of hydraulic fluid, but converting the kinetic energy into heat.

Vibration absorption is a simple way to prevent equipment breakage and noisy operation. The components used to prevent excessive vibrations and noises from equipment processes are often simple and cheap. For a manufacturer, installing vibration absorbing parts is a decision that will quickly pay off. Replacing machinery parts or repairing damage caused by vibrations can be very costly. Damaged or ill working equipment could result not only in production slowing, or stopping altogether, but also in potential worker injury. Furthermore, excessive noise in a factory or manufacturing setting could contribute to an unsafe work environment, making the need for vibration absorption methods important to meet. Consumer households and commercial laundry businesses place rubber pads beneath washing machines and dryers which are specially designed to absorb the motion caused by spin cycles, reducing equipment noise and giving laundry equipment longer life. Household air conditioners typically have some form of vibration isolation preventing vibration between the air conditioner and its window housing. Rubber or foam vibration absorbers are used simultaneously for vibration isolation and for soundproofing in audio equipment applications such as speakers and sub-woofers. Common automotive and industrial applications for vibration isolating rubber bumpers and rubber pads include railway cabins, industrial machinery, radiators, electronic equipment, welding equipment and vibratory finishing equipment. The benefits are numerous and that is why vibration absorbers are used in such a variety of applications.

Vibration Isolation and Energy Absorption - Endine-ITT	Industrial Shock Absorbers - Endine-ITT

Types of Vibration Absorbers

• Air springs offer a favorable stroke-to-compressed-height ratio, when compared to air cylinders, and can accept a wide variety of actuation media, such as air, water, nitrogen or anti-freeze for use in a variety of vibration isolation applications.
• Bushings are placed between moving parts to absorb vibration.
• Cam followers are driven by circular motion. The cam follower traces the surface of the cam transmitting its motion to the required mechanism.
  
• Dashpots are absorption devices that use fluid to enact resistance. Once downward force is no longer being applied, the plunger-like device remains in position. Dashpots are used normally in small devices, such as instrumentation and precision manufacturing machinery.
  
• Energy absorption is the process of reducing the strength and magnitude of vibratory motions. Specialized materials and devices accomplish this by converting kinetic energy into heat which is then diffused.
  
• Engine mounts are vibration isolators placed between an engine and the structure that supports the engine, in order to reduce the effects of vibration, noise and shock encountered during engine operation.
  
• Helical isolators achieve attenuation of both shock and vibration and are made entirely of non-corrosive materials. Helical isolators are most commonly used for vibration and shock absorption in such industrial and commercial machinery as compressors, hammers, printing machines and other applications in which shock isolation is important to the effective and efficient running of the apparatus.
  
• Machinery mounts protect machines from vibrations emanating from within the equipment itself, as well as from other pieces of equipment. Machinery mounts are used on compressors, screw machines, pumps and generators.
  
• Rubber bumpers are commonly used in the automotive/trucking industry to protect vehicles and trailers through vibration and shock absorption.
  
• Rubber mounts are rubber components that isolate the vibration from moving parts.
• Rubber pads are vibration dampeners often placed between industrial equipment and the surface upon which the equipment rests. Rubber pads may have a ribbed pattern to prevent slippage.
  
• Shock absorbers use various methods to dampen vibrations caused by sudden motion and mechanical shocks.
• Shock mounts isolate and absorb the kinetic energy created by oscillatory mechanical components in order to reduce the noise pollution and physical wear otherwise caused by continuous vibration.
• Vibration control involves isolating, dampening and canceling secondary oscillatory movements in industrial settings using a number of different devices and materials which absorb the kinetic energy of a vibration before it reaches adjacent surfaces.
• Vibration damping within an industrial setting is a method of controlling and reducing vibrations made by machinery when design strategies have reached their limits.
• Vibration mounts are rubber mounts used to protect a variety of industrial items, including engines, machinery and equipment components. Vibration mounts effectively reduce or eliminate oscillation.
  
• Vibration isolators are used to protect equipment by keeping the vibration of a component from spreading to the entire machine or work environment.
• Wire rope isolators consist of a metal cable configured in sets of strands. Wire rope isolators are used in applications in which exposure to chemicals, oils and high or low temperatures is common.

Vibration Absorbers Terms

Amplitude - Amplitude is the maximum value of a repetitively oscillating quantity (i.e. acceleration, displacement).
 
Damping - The reduction of oscillatory motion in a vibratory object through the loss of energy in the form of heat during vibratory cycles. Vibration dampers increase the amount of vibratory energy lost during an object's oscillatory motion, which decreases the vibration of the object.
 
Deflection - An indication of a vibration isolator's ability to provide vibration control. Deflection refers to the amount that an elastomer, such as a rubber mount, moves due to a force, such as vibration or shock.
 
Displacement - The movement of an object from its initial placement. Vibration is a common cause of displacement.
 
Elastomer - A material, such as rubber, that is capable of returning to its initial length after being stretched at room temperature to at least twice its original length.
 
Forced Vibration - The vibration of an object due to an applied force.
 
Fragility - A measurement representing the level of vibration to which an object can be subjected before sustaining damage.
 
Free Vibration - The occurrence of vibratory movement during an object's displacement without the application of an external force.
 
Frequency - The repetition of vibratory motion during a specified period of time.
 
Hertz - Also referred to as "cycles per second," it is a measurement of vibratory motion or frequency that occurs per second.
 
Impulse - The integral of force over a time interval.
 
Jerk - The rate of change of acceleration with time.
 
Natural Frequency - The number of cycles that an object freely vibrates during a given unit of time.
 
Periodic Motion - Motion that repeats itself at measurable intervals of time.
 
Resonance - An increase in the vibratory motion of an object that occurs when an object's natural frequency and the frequency of the force applied to an object are equivalent to one another. This frequency point is termed the resonant frequency.
 
Shock - A force to which an object is subjected that disturbs the object's stability, causing an imbalance of equilibrium. Shock is often isolated in conjunction with vibration to stabilize an object's equilibrium.
 
Steady State Vibration - Steady state vibration exists in a system, if the velocity is a continuous periodic quantity.
 
Transmissibility - The amount of vibration generated by an object that is transmitted to the object's support structure.