Abstract: In a fixed angle centrifuge having sample tube apertures symmetrically distributed around the spin axis of a rotor body, two rotor body shapes are disclosed at the rotor body top adjacent the openings to the sample tube apertures. These shapes each permit both release of the sample tube aperture cores and maintain the intersection of the top of the sample tube aperture within a plane normal to the axis of the sample tube aperture. A first shape includes placing discrete facets at the top of the rotor body adjacent the sample tube aperture openings. The second, and preferred embodiment, includes generating a spherical surface utilizing a spherical radius which is taken from the intersection of the spin axis of the rotor and the axes from each of the sample tube apertures. In both cases, precise termination of material molding the rotor body occurs at the top of the cylindrical portion of the sample tube aperture. Sample tube aperture core withdrawal easily occurs.

Abstract: In the compression molding of a fixed angle centrifuge rotor utilizing discontinuous fibers, sample tube apertures cores present in the net-shape mold are covered with pre-cured sample tube aperture inserts. The sample tube aperture inserts have a constant and unchanging inside diameter and are formed from composite fiber. This composite fiber extends from the closed bottom of the inserts, upwardly along the sides of the inserts to the open top of the inserts to provide tensile strength longitudinally of the sample tube aperture inserts. The sample tube aperture inserts have a regular and smooth inside for first accommodating the sample tube aperture cores when the rotor is compression molded and later the sample tubes themselves when the rotor is fully fabricated. These inserts have an irregular outside for forming an interference fit with the subsequently formed compression molded rotor body.

Abstract: A method for the compression molding of composite fiber fixed angle rotors is disclosed. A female mold member defines a closed cylinder cavity for molding the bottom surface of the rotor, this cavity usually defining a frustum shaped central cavity complimentary to and concentric with the spin axis of the ultimately formed rotor. A male mold member having a complimentary cylindrical profile contains a frustum shaped inner cavity with the apex of the frustum disposed to the inner portion of the cylinder and the base end of the frustum exposed to the cylindrical opening of the female mold. This frustum shaped inner cavity defines the exterior frustum shape of the ultimately produced rotor and defines between the exterior frustum profile and the frustum shaped inner cavity a rotor body wall having sufficient thickness to receive the sample tube apertures. At the apex end of the frustum shaped cavity in the male mold member, there is located a lock system for maintaining sample tube aperture cores.

Abstract: A method and apparatus for the compression molding of composite fiber fixed angle rotors is disclosed. A female mold member defines a closed cylinder cavity for molding the bottom surface of the rotor, this cavity usually defining a frustum shaped central cavity complimentary to and concentric with the spin axis of the ultimately formed rotor. A male mold member having a complimentary cylindrical profile contains a frustum shaped inner cavity with the apex of the frustum disposed to the inner portion of the cylinder and the base end of the frustum exposed to the cylindrical opening of the female mold. This frustum shaped inner cavity defines the exterior frustum shape of the ultimately produced rotor and defines between the exterior frustum profile and the frustum shaped inner cavity a rotor body wall having sufficient thickness to receive the sample tube apertures. At the apex end of the frustum shaped cavity in the male mold member, there is located a lock system for maintaining sample tube aperture cores.

Abstract: A fixed angle centrifuge rotor body is constructed from compression molded composite material. The rotor body has a frustum shaped peripheral contour about a central spin axis between a base end and an apex end. The body has net shaped angled sample tube apertures defined in the rotor body extending from openings in the apex end adjacent the spin axis of the rotor body to bottom portions of the sample tube apertures more remote from the spin axis of the rotor body. The rotor body is formed from resin cured about discontinuous composite fiber with the major axis of the discontinuous fiber disposed normal to the spin axis of the rotor body interior of the rotor body. The resin cured discontinuous composite fibers exceed 40 weight percent of the cured rotor product and have no visible layering between respective fibers. The resin cured discontinuous composite fibers have minor vertical excursion parallel to the spin axis of the rotor and relatively no kinking along their respective lengths.