The IBM 6182 pen plotter from 1984, derived from the HP 7550, is the most advanced small plotter ever built. It has an incredible maximum acceleration of 6g, making it one of the fastest plotters ever. It was also the first plotter to include a sheet feeder, which allowed for unattended plotting. Pen plotters were popular computer printing devices during the 1980's for printing vector graphics. They print by moving a pen across the surface of a piece of paper, much like a human hand does. This means their drawing capabilities are restricted to line art. To be able to draw all sorts of shapes the plotter pen needs to be able to move across the paper on an X and Y axis. The IBM and HP line of pen plotters have a specific design where the pen moves along one axis, and the paper moves along the other axis ('grit wheel' mechanism). The pen is mounted on a carriage that moves back and forth in a line between the grit wheels, representing the orthogonal axis. These plotters became popular for desktop business graphics and in engineering laboratories for technical drawings. Starting from the mid-1990's pen plotters were gradually replaced by high-resolution inkjet and laser printers. Surviving pen plotters have often been converted to venyl sign cutters.