Update on shock & vibration technologies

Bansbach Easylift’s industrial shock absorbers are designed for energy absorption and linear deceleration. They absorb the impact with no bounce back. This steady, gradual deceleration allows faster cycle rates, increased equipment life, and higher production rates while reducing maintenance expenses.

When high-speed, heavy-duty industrial automation systems must decelerate and stop, damage to the load and the machine itself can result. The cause of thisdamage is the release of kinetic energy, which induces longtermvibration and fatigue and sudden shock in a system.Smooth deceleration of a system should be done with shock andvibration attenuation components.

Based on the type of inputs present in the application, vibration and shock attenuation components can include shock absorbers, linear dampers, wire rope or spring isolators, elastomeric isolators, air springs, or structural damping treatments. These devices help manufacturers reduce equipment downtime and costly cycle time limitations.

These products work in a broad range of applications — from the rate control mechanisms that slow the motion of overhead luggage bins or seat recline on commercial aircraft, to the isolators that keep GPS from losing signal or becoming damaged on farm and construction equipment as they harvest crops or pave roadways.

SHOCK AND VIBRATION DAMPING

Most shock absorbers deliver their damping characteristics through the use of hydraulic fluids. The fluid is pushed by a piston and rod through small orifice holes to create damping, and this action compresses some type of gas. This in turn creates a spring force to return the rod back to its starting position when the load is removed.

Shock absorbers and dampers are generally made of highstrength steel to handle the pressures from the internal hydraulic forces. Elastomeric seals prevent the fluid from leaking out of the cylinder, and special plating and coatings keep the units protected from harsh operating environments.

Recent and ongoing developments in sealing technologies and in the internal designs of shock absorbers and dampers have allowed for longer service life and more compact designs. Miniaturization is a growing trend in these devices, as systems require tighter tolerances and smaller machine footprints. In machine automation and robotics, motion stabilization requires the use of hydraulic dampers, particularly micro-hydraulic designs.

ACE Controls’ new HB50 hydraulic damper is designed for use in heavy-duty safety applications. Featuring a steel body, it offers individual adjustment for push and pull motion and reduces downtime and component wear. These maintenance free, ready-to-install machine elements are adjustable and provide a constant feed rate.

VIBRATION ISOLATION

Vibration-isolation products rely generally on mechanical designs to achieve their isolation characteristics. A spring function provides support for the mounted equipment, while decoupling it from the vibration source. Friction and elastomeric material properties give the isolators their damping characteristics.

Isolators can be made from a variety of materials. Wire rope and spring isolators can be made from carbon steel, stainless steel or aluminum. Elastomeric isolators generally have metallic components that function as mounting brackets, separated by an elastomeric material that provides the stiffness and damping desired. Common elastomeric compounds include natural rubber, neoprene, and silicone but many compounds and blends deliver various characteristics specific to satisfy different applications.

Air springs include metallic end fittings coupled by a composite elastomeric-based bladder that contains the compressed air to provide isolation. These single-acting designs have a pressurized bladder and two end plates. As air is directed into the air bladders, they expand linearly.

All of these reusable designs are self-contained, offering a number of advantages over any other technology that may require outside componentry. For example, hydraulic systems may require plumbing while electrical systems may require wiring and power.

Energy or power dissipation is key when selecting a damper or shockabsorbing device. The size and characteristics of the device are based on these inputs, so it is generally the first consideration to make.

Dynamic spring rate and damping are the two biggest considerations when selecting an isolator. These characteristics define system natural frequency (resonant frequency) and the most suitable isolation system.

System of interlocking Sorbothane layers can be customized to meet individual energy absorbing requirements. These specialized 4 X 4 in. Sorbothane pads can be layered and “locked” together to assemble a specific shock attenuating and vibration isolating assembly. The steel base plate provides column integrity and helps maintain the correct shape factor. A steel top plate can also be utilized. Layers of interlocking Sorbothane pads are added — or removed — to meet the desired size and isolation requirements.

ELASTOMER, RUBBER PADS FOR VIBRATION AND SHOCK REDUCING

Elastomer and other synthetic and rubber pads can also damp vibration and isolate shock loads. They come in tubes, bushings, blocks, pads and washers. These components work in heavy-duty applications to deliver strong cushioning for cranes, presses, and pipelines and bridges; they also excel in vibration reduction for lab and testing equipment and designs for aerospace.

Rubber-like materials let these padding elements satisfy specific requirements related to natural frequency, load, and area. Because they are soft, they are also forgiving.

Predicting the natural frequency of an application lets material manufacturers target known disturbance frequencies to dissipate energy. The lower the ratio of natural system frequency to disturbance frequency, the more it’s possible to isolate problem vibrations.

These cushioning plates can protect machinery subsystems against impacts and isolate vibration and structure-borne noise. For example, PAD plates from ACE Controls withstand compressive loads to 10,000 psi or 69 N/mm 2 depending on plate form and size.

Another product called Sorbothane (from a company with the same name) is a thermoset that attenuates shock with near-faultless memory. Deformation is elastic and not plastic, so pads of the material reliably return to their original shape. Custom pieces of the material work for vibration and acoustic damping and isolation. Sorbothane turns mechanical energy into heat as the material is deformed. Molecular friction generates heat energy that translates perpendicularly away from the axis of incidence.

Wire rope isolators from ITT Enidine have stainless steel cable and aluminum retaining bars to provide high multi-axis isolation. The isolators are completely unaffected by oil, chemicals, abrasives, ozone, and temperature extremes. The compact designs provide simultaneous shock and vibration attenuation where sway and package space are a premium. Their symmetrical design provides consistent, multi-axis isolation and their small size permits isolation of individual system components, rather than the entire system.