The Rose Bud Kinematic Coupling

The Rose Bud Kinematic mount
Rosebud Kinematic Mount
Rosebud KinematicMount / Coupling

The Three Ball Kinematic Coupling ( Rosebud ) is one of the top performing location devices. It restricts three degrees of freedom, without the distortion caused by clamping forces. This three-ball device takes the place of the conical cup used in the classical kinematic system. However, a three-ball system is limited to rather light load as the overall size of the coupling grows dramatically when larger balls must be used to cope with heavier pay loads.

The solution in high load situations is to use a Rose Bud configuration. By cutting cylindrical fingers out of the side of a large diameter ball, and then cutting this finger in half, a small super rigid component or rose petal is produced that is easy to mount on the Kinematic Platform. To rigidly mount these components, you simply machine a 120 degree "Y" shaped trench in the platform, with an end mill of a radius, that matches the cylindrical radius of the rose petal and glue the individual components in. Because the resulting force on the components is down and out and they are buried in the "Y" shaped trench, the limiting load factor is the strength of the material that the Kinematic Platform is made of. The spherical surfaces of these components retain the high quality geometry and excellent surface finish of the precision balls that they were removed from.

To reduce the overall height of the assembly, the tops of the cylindrical fingers are usually cut down some. These devices can be prepared for surface mounting by drilling and threading a hole in the base plane. When this is done, much of the system's rigidity is lost. A single standard component has been developed that will fill most kinematic applications. A three eighths of an inch ( 3/8", 9.53 mm) radius, that is three three quarters of an inch ( 3/4", 19 mm) diameter cylinder is cut out of a one and one quarter inch ( 1 1/4", 31.75 mm) diameter sphere. This cylindrical finger is then cut in half. The nest provided by three of these components is compatible with any ball size from three eighths of an inch ( 3/8", 9.53 mm ) to over one inch ( 25.4 mm ) diameter.

The material usually used for manufacturing these components is tungsten carbide. This is the stiffest, hardest commercially available material with a Young's Modulus of Elasticity of 98,000,000 P.S.I. and a hardness of 91 HRA. They are also available in a micro grained stainless steel that is hardened to 58 HRC minimum. Other combinations of radii and material will be produced to fill any specific customer needs. These include corrosion resistance and special magnetic or electrical properties.

Rose Bud Pricing

Part # Description Price Purchase
375-RB ROSE BUD, 0.375" ( 3/8" ), STAINLESS STEEL $59.40 Shopping Cart
375-TRB ROSE BUD, 0.375" ( 3/8" ), TRUNCATED, STAINLESS STEEL $59.40 Shopping Cart
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