Head Expanders |  Inclined Three Axis Vibration Fixture  |  Rotating Three Axis Cube Fixture
Lazy Susan Test Fixture | Vibraglide Sliptable | Hydraglide Sliptable | Seismic Bases | Shakermate



M/RAD produces a wide variety of standard and custom test fixtures for use with electrodynamic shakers. A vibration fixture is the device that interfaces the vibration shaker and the test item(s). Its design can range from a very simple plate with a few attachment holes to an extremely complex device with automatic features that enable production testing to occur with rapid insertion and/or removal of the test item.


Head Expanders

Head Expanders are the most common fixture for vertical motion, as they provide larger surfaces to which test specimens may be attached. Most head expanders are fabricated from magnesium to provide the optimum combination of light weight, rigidity and strength. They are available in round, square or rectangular shapes and are usually manufactured as a weldment, although cast head expanders are also available. Optional features include damping treatment, corrosion protection, thermal barrier, thermal treatment, shaker guidance/ support and a choice of insert locations. Other standard fixtures are available for mounting product to the shaker, such as cubes, L fixtures and T fixtures. These fixtures provide a means to position the test specimen to allow for multi-axis testing without rotating the shaker head from the vertical to horizontal position.


Inclined Three Axis Vibration Fixture

M/RAD has designed and developed a vibration test fixture adapted for attachment to a conventional electrodynamic shaker to support a test item relative to the shaker table so that the test item can be vibration tested along three mutually-orthogonal axes in a single vibration test procedure without repositioning the test item during the procedure. This fixture simultaneously applies three equal mutually orthogonal X, Y and Z axes by a single attachment of the test item to the test fixture. The 3-Axis Vibration Fixture may be designed to accommodate test items of varying sizes and payloads. The fixture is constructed of AZ31B magnesium to insure the lightest possible weight and is a weldment to provide the optimum in strength and rigidity.


Rotating Three Axis Cube Fixture

To minimize the time and effort required to reposition an object when multi-axis testing of the object is to be performed, a three-axis vibration test fixture has been developed. This test fixture includes a cube to which a test object is secured and a clamp assembly for securing the cube to a head expander. The head expander is rigidly attached to the vibration table. A shaft is attached to one corner of the cube so as to diagonally extend along an axis that intersects the center and opposite corners of the cube. When it is desired to reposition the test object for vibration testing along a different axis of the object, the clamping assembly is actuated to release the cube. Then, the cube is repositioned by automatically rotating the shaft until the cube is in the desired new position. Thereafter, the cube is reclamped to the head expander.


Lazy Susan Test Fixture

This test fixture has been developed to provide an easy means to rotate a test item every 45 degrees while attached to a sliptable. This test fixture includes a lower plate with retractable ball bearings, an upper plate which rotates upon the ball bearings and a clamp assembly for securing the upper plate to the lower plate. The test item is securely fastened to the upper plate and, by releasing the clamp assembly, the upper plate is indexed for a smooth rotation in 45 degree increments. For multi-axis test requirements, the lazy susan fixture is a proven alternative to minimize set up and dismantling time.


Vibraglide Sliptable

For horizontal motion, the M/RAD Vibraglide Sliptable is considered the industry favorite for ease of operation and longevity. Vibraglide sliptables have been in continuous operation for over twenty-seven years. Designed for interface with any electrodynamic shaker, the vibraglide test table eliminates the necessity for supporting test specimens by shock cord, rollers or flexures. It permits simplified translational testing of components and provides savings in test fixture design, weight and set up time. The vibraglide sliptable consists essentially of a magnesium worktable supported on a stationary granite block by a pressurized oil surface. The magnesium table is easily movable along the axis of applied force with a minimum of friction loss. Self-aligning spherical washers are supplied to simplify attachment to the shaker. Drive Bars are available to increase the rigidity of the shaker armature and to provide a quick means of attachment to the slipplate. Proper alignment insures that the table does not inflict unnecessary and damaging twisting moments and severe strains to the shaker armature. The substantial granite base assures a firm foundation for the test and represents substantial resistance to overturning moments. A 30 psi oil supply system provides adequate table breakaway force under heavy specimen loads and is externally mounted for ease of maintenance. Flexures and low pressure bearings are available for increased overturning moment restraint.


Hydraglide Sliptable

The M/RAD Hydraglide Hydrostatic Bearing Sliptable permits testing of heavy payloads with a high center of gravity as well as off center loads. Designed for interface with any electrodynamic shaker, this sliptable features journal hydrostatic bearings, fabricated by M/RAD, to provide restraint in the pitch, roll and yaw axes. The standard stroke of the bearings is 1.2 inches, with 2 and 3 inch stroke available. These sliptables may be integrated with either a seismic base or alignment mass.


Seismic Bases

M/RAD Seismic Bases are used to couple vibration shakers and slip tables to a common base while isolating the vibration from the surrounding area. Bases can be supplied as stand alone units or integrated with a combined shaker/sliptable to provide a low profile system. The seismic base is a steel structure filled with reinforced concrete. The steel frame is constructed to provide all the structural strength and stiffness necessary under full dynamic load conditions. M/RAD seismic bases include a pneumatic isolation system under the base (2.2 Hz natural frequency), control panel and all interconnecting hardware. M/RAD also manufactures seismic bases provided in a pit, below the floor with air isolators. Manual or servo controls are available to position the height of the air isolation system to +0.005 inch. No seismic block is too large for M/RAD to engineer and construct.

500,000 lb. Seismic Base under Construction. Base Size: 17 Ft X 25 Ft. X 8 Ft. thick.