The manufacturer of a cell analyzer, Immunicon Corp., Huntingdon Valley, Pa., had to hustle to redesign it when the company got word suppliers would soon discontinue critical components. The analyzer looks for cancer cells in biopsy samples, often one cell in a million, with a camera that focuses on microscopic areas as the biopsy inches by underneath. That requires precise movements on precision bearings.

Frank Modica, Immunicon's manager of mechanical engineering, says his team had time for few design iterations and then on-time component delivery was key to staying on schedule. “One bearing manufacturer wanted up to eight weeks to get product from Japan”. But NB Corp. Wood Dale, Ill., (nbcorporation.com) delivered in about three.

“New bearings were needed because we selected a linear motor instead of a conventional stepper design, and that required redesigning the motion stages,” says Modica. Cross-roller linear bearings were chosen for their accuracy. They have larger contact areas than ball bearings which reduces elastic deformation for consistently precise movement. Rollers do not recirculate so they all carry load, which increases rigidity as well as load capacity. Nonrecirculation also means lower friction. In fact, the bearings exhibit little or no difference between static and dynamic frictional resistances, even under low-load conditions, making them well suited for small movements. And being all stainless steel makes them ideal for clean room applications.