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VUTRAX Technical Support

VUTRAX SOFTWARE ADVICE NOTICE 116 (Issue 3) - 12 Sep 2002

Vutrax issues up to and including 12.3b

PLOT - Forcing Identical Coordinates for Photoplot & CNC Output

Note: Vutrax 12.4a onwards contain a number of enhancements that automatically align Photoplot, CNC DRill and CNC Milling output. This document is for user of Vutrax 12.3b and earlier versions.

For most users the PLOT scheme for normalising the plot near 0 0 coordinate of the plotter is the most convenient scheme. However, different output devices use different offsets because:-

  • Plotted output needs to allow for artwork element width and pad sizes, while CNC output is usually required to use pad centred datums that can provide an absolute coordinate reference for setting up.
  • Plotter output formats need to force an offset to accommodate edges of paper, tendency to lose registration due to overshoot reaching limit switches etc.

The problem arises when these modules are used to generate files subsequently presented to another CAD/CAM system or viewer where the Photoplot and CNC data will be related.

The following method can be applied to produce identical coordinates.

Select Compatible Control Files:

Choose CNC and Photoplot output formats that operate using the same coordinate system and resolution.
For example.
  • For 0.001"   resolution GERBPHOT.HXY & CNCXCLNB.NXY
  • For 0.0001" resolution GERBT10.HXY (or GERB274X.HXY) & CNCBT10.NXY

Remove Edge Clearance from the Photoplot Control File

This is a once-off change that we recommend is saved as a new file used specially for this purpose. The need for the offsets still applies for 'real' plots unless precautions are taken, so you should generally use the original file for normal use. Standard Plot control files reside in the VUTRAX home directory (usually C:\VUTRAX)
The fixed offset is defined by a plot control file line:-
    $SB=<value>;$N ...
where <value> needs to be zero.
e.g. If editing GERB274X.HXY to GERB274X_0_Edge.HXY change the displayed heading at the top (lines starting $M are displayed messages while everything after $N is a comment) and find and change (line 18 in this case)
    $SB=1000;$N Edge clearance 5 mm
    $SB=0;$N Zero edge clearance
Suggestion: The menu system does not offer these extension, so use Open All Files from the text editing menu, and immediately Save As the new file before applying changes.
Prepare the Artwork to Provide a Datum

To plot a set of Artworks with consistent normalisation:

  1. Select Draw Box from (Edit > Boxed Items) (BOX CREATE) and draw an outline completely enclosing the artwork including any pads and Script at the edge, and outside the thickness of any boarder lines (e.g. 50 thou outside all existing drawing on all layers).
  2. Type command MOVE=1 or just M= to move to the first point of the box. Now render it invisible using command WIDTH  0  5 (this step is important - placing it on an unplotted layer would still allow some types of plotting to be offset to allow for the width).
  3. Make the required plots to file.

30 June 1993: Original issue.
20 Nov 1998: Revised for Vutrax 12.0 and 0.0001" resolution Control files.
12 Sep  2002: Superceded by Enhancements in Vutrax 12.4a.