VUTRAX SOFTWARE ADVICE NOTICE 96 - 13 Feb 1992

       PLOTTING TO HPGL PLOTTERS - SPEEDING UP PAD DRAWING

Output of PCB layouts to pen-plotters can be very time  consuming
owing  to  the  number of operations necessary to fill areas. The
worst of these is normally the  drawing  of  filled  circles  for
component pads, vias, and end-rounding (option Q1). The following
suggests ways in which to improve such plotting. A guide to  each
likely performance improvement is listed in brackets.

For those items suggesting changes to the .PXY file, first

COPY \VUTRAX\MAIN\HPGL<whatever>.PXY \VUTRAX\MAIN\TRIAL.PXY

and apply changes to \VUTRAX\MAIN\TRIAL.PXY. For testing, use the
[SELECTPLOTTER] menu box to select plot control file TRIAL.PXY

  o For check plots use option Q2 to obtain outline  only.  Since
    this  prevents  all  filling,  use  of  other items with this
    scheme either have no effect, or in the case of forcing white
    space, are counterproductive. (600% faster)

  o Ensure that you are using the largest available pen  for  the
    job. An additional large pen in the colour appropriate to the
    pads, will be selected in preference to a  smaller  one  when
    possible,  and  can  greatly  reduce  the  number  of drawing
    strokes. Simply add any  additional  available  pens  to  the
    appropriate .NIB file. e.g.

        Draw 12 12 +02 -02 A Fixed '0.12" BLK FIBRE' '1'
        Draw 24 24 +02 -02 A Fixed '0.24" BLK FIBRE' '2'

    with the wider pen in position 2. (100% upwards).

  o Minimise the overlap between passes by altering the  .PXY  as
    described in the introduction. Find line

        $SN=4;$N Minimum overlap on constructions

    and change 4 to the smallest value that fills without leaving
    white  streaks  between  lines.  If you can set this to 0 and
    still get no white streaks then the pen is probably drawing a
    wider  line  than  you  have tabulated in the .NIB file. (20%
    faster)

  o Apply the Force  Whitespace  option  Q36  which  reduces  the
    amount of fill required (30% faster).

  o If the actual drawing of circles is substantially slower than
    similar  length  line  drawing  operations  try either of the
    following (but not both together):-

      * Alter line   $SN=4;$N Node fill using concentric ...
        to           $SN=0;$N Node fill using Octagons
        (50% faster)

      * In line $T4=$... ...C;,10;$K10;$R$U$

        Change the 10 in ,10; (not $K10)  to  20,  30  or  45  to
        change  the cord angle from 10 to the nominated number of
        degrees.  45  produces  octagons  maybe   faster,   maybe
        not, than line  drawing  them  as  the  first  item. (40%
        faster)