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Fabreeka has a leading role in providing vibration isolation systems and design techniques to meet the increasing demands of automotive, aircraft and aerospace testing in simulated environments. The company has been providing vibration isolation and shock control products for the past decade, utilizing combined expertise for customized projects and turnkey solutions.
In doing so, the solutions for auto testing include the design of test equipment support foundations and their reaction masses together with structural and dynamic analysis. Applications range from dynamometers, rolling road isolation, road simulators, multi-axis shaker tables to many kinds of other test equipment.
To support engineers in aircraft testing, Fabreeka has designed a number of soft support systems using standard and custom pneumatic isolators for ground vibration testing, while the company provides low frequency vibration isolation systems for critical testing applications in the aerospace and defense industry, which require ultra-low frequency isolation and vacuum chamber isolation.
Additionally, Fabreeka provides solutions for foundation isolation as well as for material testing machines including tensile, compression and fatigue testing equipment that can create vibration and shock.
Aerospace Testing
When performing testing of large spacecraft or hardware that will be launched into orbit, it is necessary to conduct testing in a space-simulated environment. To achieve this, a vacuum chamber or thermal vacuum chamber is used which creates an environment to simulate the pressure and thermal effects of launch or space travel in orbit.
It is necessary to decouple the spacecraft or payload from the chamber using Fabreeka vibration isolators to attenuate environmental vibration from the testing. In some cases, where feasible, the entire chamber with payload is decoupled from the test facility. In cases where the size of the vacuum chamber, or the existing chamber, does not allow for external isolators the test payload must be isolated inside the chamber. To achieve this, a vacuum compatible isolation system is used. When isolators are used inside a vacuum chamber, they must meet strict material specifications to limit out-gassing and be constructed to fulfill particulate and molecular cleanliness requirements as well. Additionally, in thermo-vacuum applications, the isolators may be required to function in temperature extremes where heater blankets are necessary to keep them at an operable temperature.
Applications often include nano-type measurements and can have error budgets within microns or tenths of arc seconds. In this sensitive field, experts cooperate with Fabreeka and use customized stainless steel PAL isolators for vacuum chamber isolation with a special design to keep air permeation to a minimum so the vacuum chamber can achieve deep vacuum levels. The assembly can be done in a clean-room environment, and isolator components can be baked out to minimize out-gassing.
Aircraft Testing
Fabreeka has designed a number of soft support systems (SSS) using standard and custom pneumatic isolators for ground vibration testing (GVT) of aircraft. To obtain accurate results during GVT, the modal testing of the aircraft requires simulation of a “free-free” condition. To achieve this condition, Fabreeka works with the structural and dynamics testing groups of aircraft manufacturers to design the required SSS for the GVT.
The pneumatic isolators support and decouple the aircraft from the ground when the aircraft is undergoing GVT and modal or flutter analysis. The role of the system is especially important in identifying structural resonances and validating flutter models. The SSS can include a mechanical jacking system to lift the aircraft off of its landing gear. Fabreeka’s custom isolator designs can achieve a natural frequency as low as 0.5 Hz.
Professionals are well aware that they save time during testing by using a Fabreeka custom system since traditional methods such as bungee cords are very time consuming due to the bungees being changed out for every load condition.
Auto Testing
Fabreeka is also a leader in providing vibration isolation systems and design techniques to meet the growing demands of vehicle testing in simulated environments where dynamometers, engine test rigs, road simulators and multi-axis shaker tables are in use. Here, Fabreeka’s technical expertise includes the structural design of support structures and reaction masses; static and dynamic analysis and acceptance testing.
In many cases when the forces are not extreme and the frame or base of the machine is rigid, Fabreeka's PAL or RLA pneumatic isolators are directly placed under the equipment, namely dynamometers or vibration tables. RLA isolators offer a larger piston stroke to handle larger dynamic loads typically seen in vibration testing applications such as shakers and 4-post-shakers without compromising the natural frequency of the system.
PAL or RLA pneumatic isolators are also the right choice for supporting a concrete foundation with the test equipment. Over decades, Fabreeka has gained the expertise to develop all types of vibration isolation projects for automotive testing and can provide a turnkey solution including foundation design, demolition, construction work, bedplate, installation and acceptance testing.
Countless successful projects with car and truck manufacturers are also proof of Fabreeka's know-how from concept to the final production model in rolling road isolation.
Fabreeka has a leading role in providing vibration isolation systems and design techniques to meet the increasing demands of automotive, aircraft and aerospace testing in simulated environments. The company has been providing vibration isolation and shock control products for the past decade, utilizing combined expertise for customized projects and turnkey solutions.
In doing so, the solutions for auto testing include the design of test equipment support foundations and their reaction masses together with structural and dynamic analysis. Applications range from dynamometers, rolling road isolation, road simulators, multi-axis shaker tables to many kinds of other test equipment.
To support engineers in aircraft testing, Fabreeka has designed a number of soft support systems using standard and custom pneumatic isolators for ground vibration testing, while the company provides low frequency vibration isolation systems for critical testing applications in the aerospace and defense industry, which require ultra-low frequency isolation and vacuum chamber isolation.
Additionally, Fabreeka provides solutions for foundation isolation as well as for material testing machines including tensile, compression and fatigue testing equipment that can create vibration and shock.
Aerospace Testing
When performing testing of large spacecraft or hardware that will be launched into orbit, it is necessary to conduct testing in a space-simulated environment. To achieve this, a vacuum chamber or thermal vacuum chamber is used which creates an environment to simulate the pressure and thermal effects of launch or space travel in orbit.
It is necessary to decouple the spacecraft or payload from the chamber using Fabreeka vibration isolators to attenuate environmental vibration from the testing. In some cases, where feasible, the entire chamber with payload is decoupled from the test facility. In cases where the size of the vacuum chamber, or the existing chamber, does not allow for external isolators the test payload must be isolated inside the chamber. To achieve this, a vacuum compatible isolation system is used. When isolators are used inside a vacuum chamber, they must meet strict material specifications to limit out-gassing and be constructed to fulfill particulate and molecular cleanliness requirements as well. Additionally, in thermo-vacuum applications, the isolators may be required to function in temperature extremes where heater blankets are necessary to keep them at an operable temperature.
Applications often include nano-type measurements and can have error budgets within microns or tenths of arc seconds. In this sensitive field, experts cooperate with Fabreeka and use customized stainless steel PAL isolators for vacuum chamber isolation with a special design to keep air permeation to a minimum so the vacuum chamber can achieve deep vacuum levels. The assembly can be done in a clean-room environment, and isolator components can be baked out to minimize out-gassing.
Aircraft Testing
Fabreeka has designed a number of soft support systems (SSS) using standard and custom pneumatic isolators for ground vibration testing (GVT) of aircraft. To obtain accurate results during GVT, the modal testing of the aircraft requires simulation of a “free-free” condition. To achieve this condition, Fabreeka works with the structural and dynamics testing groups of aircraft manufacturers to design the required SSS for the GVT.
The pneumatic isolators support and decouple the aircraft from the ground when the aircraft is undergoing GVT and modal or flutter analysis. The role of the system is especially important in identifying structural resonances and validating flutter models. The SSS can include a mechanical jacking system to lift the aircraft off of its landing gear. Fabreeka’s custom isolator designs can achieve a natural frequency as low as 0.5 Hz.
Professionals are well aware that they save time during testing by using a Fabreeka custom system since traditional methods such as bungee cords are very time consuming due to the bungees being changed out for every load condition.
Auto Testing
Fabreeka is also a leader in providing vibration isolation systems and design techniques to meet the growing demands of vehicle testing in simulated environments where dynamometers, engine test rigs, road simulators and multi-axis shaker tables are in use. Here, Fabreeka’s technical expertise includes the structural design of support structures and reaction masses; static and dynamic analysis and acceptance testing.
In many cases when the forces are not extreme and the frame or base of the machine is rigid, Fabreeka's PAL or RLA pneumatic isolators are directly placed under the equipment, namely dynamometers or vibration tables. RLA isolators offer a larger piston stroke to handle larger dynamic loads typically seen in vibration testing applications such as shakers and 4-post-shakers without compromising the natural frequency of the system.
PAL or RLA pneumatic isolators are also the right choice for supporting a concrete foundation with the test equipment. Over decades, Fabreeka has gained the expertise to develop all types of vibration isolation projects for automotive testing and can provide a turnkey solution including foundation design, demolition, construction work, bedplate, installation and acceptance testing.
Countless successful projects with car and truck manufacturers are also proof of Fabreeka's know-how from concept to the final production model in rolling road isolation.
KEY FEATURES/BENEFITS
A concrete support structure (foundation, inertia block, reaction mass) is used to satisfy one or more of the following conditions:
1). Provide/improve structural stiffness for the machine/equipment being isolated. Some types of equipment do not operate properly unless supported by a rigid structure. This applies to certain types of machine tools that are not inherently rigid and therefore need a rigid support to maintain the prescribed accuracy. In other types of machinery (such as printing presses) consisting of articulated components, a rigid support may be needed to maintain the proper alignment of working parts.
2). Increase stability on the vibration isolators by limiting dynamic deflection. If a machine (such as a diesel engine, forging hammer or electro-dynamic shaker) generates relatively large forces during its operation, the overall movement of the machine on its isolation system tends to become excessive unless its effective mass is substantially increased. This increase in effective mass can be achieved by attaching the machine rigidly to an inertia block and mounting the inertia block (reaction mass) on isolators.
3). Isolate the equipment/machine from the environment when installing isolators directly beneath the unit would compromise the conditions above. In applications in which the frequency of excitation is low, the natural frequency of the isolation system must be very low to provide low transmissibility and therefore good vibration isolation. A problem often arises with a machine intended to be mounted only at its base, because a low-stiffness base-mounted system tends to be unstable and will allow excessive motion to take over.
Technical Specifications
Pneumatic isolators are installed after the foundation has cured and the machine/equipment has been installed and anchored properly. The isolators are positioned under the foundation at predetermined support points and then activated to float or lift the foundation and machine off the pit floor.
The desired natural frequency (stiffness) and damping for the isolation system is usually established by the operating characteristics of the mounted equipment (source) and/or the isolation required (recipient). The design basis for the support foundation natural frequency assumes that the foundation is a rigid body with a stiffness much greater than the isolators. Similarly, the pit base also should be stiffer than the soil supporting it.
For large machine tools and CMM’s using automatic part handling systems where parts can weigh several tons, loading and unloading can generate vertical motion on the isolators. To avoid this problem, Fabreeka can vary the internal pressure of the isolators to lower the support foundation onto hard stops.
In certain applications, it is not desirable or feasible to mount a machine directly on vibration isolators.
Direct installation of vibration isolators on a machine whose frame/bed stiffness is inadequate for such, can cause bending, relative displacement and other problems, even when the floor is sufficiently rigid. For smaller machines, this can be remedied by securing the frame/bed to a rigid plate and then installing the isolators between the plate and the floor. For larger machines, the frame/bed is attached to a properly designed concrete foundation, which is then supported on the appropriate isolators for the application.
Fabreeka designs and manufactures large capacity pneumatic and air bag isolators, which support loads from 13,000 lbs (5,800 kg) to 120,000 lbs (54,000 kg) each for foundation isolation applications requiring low frequency vibration isolation. Air bag isolators provide a larger dynamic stroke than our standard PAL isolators and are used in applications where a low natural frequency (0.5 – 1.5 Hz) and large displacements must co-exist.
FAQS
How many pneumatic isolators do I use to support the inertia mass (reaction mass)?
The inertia mass should be supported on its two longest sides and the spacing between isolators is normally 5 – 8 feet. The isolators may need to be closer depending on inertia mass depth and stiffness requirements.
How can I calculate how much dynamic deflection the pneumatic isolator or airbag will have?
The calculation can be made through a dynamic analysis, which Fabreeka routinely conducts for our proposed solutions. The dynamic deflection is function of isolator/dynamic spring rate and the frequency and magnitude at which the input occurs.
When should I use an airbag and when should I use a PAL-type pneumatic isolator?
PAL-type isolators should be used in all cases where the dynamic deflection is 1/2″ or less. Airbag isolators should be used if the dynamic deflection is more than 1/2″.
How can I calculate the structural frequencies of my inertia mass (reaction mass)?
The structural frequencies can be determined using FEA software. Fabreeka can provide this service if this software is not available to you.
Is there anything special about the design of the pit and inertia mass (foundation) I should know about?
Besides the normal structural requirements considering static and dynamic loads and soil conditions, an isolated inertia mass must be designed with structural modes that are higher than the disturbing frequencies and the natural frequency of the isolators. The inertia mass will amplify the vibration, if the modes are near these frequencies (in resonance). The inertia mass must be dynamically stiff enough not to be in resonance with the isolator frequency and any disturbing frequencies. The pit must be designed based on a soil analysis to insure it is dynamically stiff enough to support the mass.
