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Maverick now offers injection molding preventative maintenance packages to the plastics industry! Repair, troubleshooting, and installation of injection mold machines and peripheral equipment.
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"Inertia Blocks" or Reaction Masses |
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In certain applications, it is not desirable or feasible to mount a machine directly on vibration isolators. Instead, the machine is attached to a relatively heavy and rigid block (usually made of concrete), which is then supported by suitable isolators. The use of such a massive block (called an inertia block or reaction mass) is desirable for the following reasons:
1. If a machine (such as a diesel engine, forging hammer, or vibration testing machine) 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. Rigidly attaching the machine to an inertia block and mounting the inertia block on isolators can achieve this increase in effective mass.
2. In applications in which the frequency of excitation is low, the natural frequency of the system must be even lower 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 to allow excessive motion. Effective isolation may therefore be difficult to achieve. A mounting arrangement with isolators angled upward may be used to move the system's elastic center closer to the center of gravity. This will reduce the effect of "rocking", improve the vibration isolation and reduce motion. It may be more feasible to mount the machine rigidly to an inertia block (to lower the center of gravity of the assembly) and to suspend the inertia block on isolators located in the same horizontal plane as the center of gravity.
3. 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.
A foundation or mass designed to meet the requirements outlined above may be installed either above the floor level or within a pit below floor level. Isolators employed to support the mass may be made of rubber, steel springs, air springs or other suitable, resilient material. The required size of the foundation depends on the reason for its use and on the type and size of equipment.
A concrete pit of the required size is lined with the resilient material. Then this material is covered with plastic sheeting, and the concrete is poured to form an inertia block. The desired natural frequency can be obtained by using resilient pads of the appropriate thickness and area.
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Last Updated ( Tuesday, 27 September 2005 )
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Foundations 