Importance

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Abstract

The workpiece is initially held in a position in which it has a free sag near the center of its length, where it is subsequently supported by a backrest for milling so as to eliminate only the elastic deformation of the workpiece which is due to the free sag. The backrest comprises a supporting jaw, adapted to be disposed under the workpiece, and to be vertically raised to engage the workpiece from below in a position of initial contact, at least one retaining jaw, adapted to be disposed above the workpiece and to be moved downwardly toward the workpiece to clamp the latter against the supporting jaw, and a detector arranged to detect and store the position in which the supporting jaw initially contacts the workpiece. A first drive is operable to raise the supporting jaw and the workpiece to a preselected extent above the position of initial contact. A second drive is operable to move the retaining jaw into engagement with the workpiece which has thus been raised.

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First Claim