Importance

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Abstract

A method and apparatus for providing platen mapping for known clearance pen movement in a graphics plotter system having a platen over which paper is moved longitudinally to create one axis, penholding apparatus moved transversely across the platen and the paper to create the other axis, and a controlled raising and lowering mechanism connected to the penholding apparatus for lowering a pen being held therein into contact with, for raising it from contact with the paper, and for providing a relative vertical position value signal. Vertical sensing apparatus is connected to the penholding apparatus for sensing the top surface of the platen. First logic is operably connected to the vertical sensing appartus and to receive the vertical position value signal from the controlled raising and lowering mechanism for calculating and saving a plurality of deviation values indicating the distance deviation of the platen top surface from parallel at a plurality of spaced points across the platen. Finally, second logic is operably connected to the controlled raising and lowering mechanism for adjusting the position of the penholding apparatus as a function of the deviation values to maintain the penholding apparatus at a known distance from the top surface of the platen as the penholding apparatus is moved transversely across the platen. Various methods of pen movement employing the platen mapping data are shown. In the preferred method, the pen is raised to a full up position for initial movement and ramped down to a known spacing for final pen drop. Adjustment of pen positioning for rotational deviation and pen dropping 'on the fly' are also disclosed.

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First Claim