Checking Gerber files with GC-Prevue Version 8

If you are involved in electronics product development or PCB design and don't already have the freeware program GC-Prevue, you need it. Here's why: GC-Prevue is the only full-featured free Gerber and NC Drill file viewer available, which makes it a great tool for viewing, checking and plotting shared printed circuit board data over a network. Because it is free, it is available to anyone in your information stream. If you haven't got it, get it from our "free stuff" page.
  1. Directory Structure
  2. Using GC-Prevue Version 8 (for Windows 9x) to view and print Gerber files.
  3. Checking mechanical dimensions in CAM files with GC-Prevue.
  4. Assembly Drawing plots from Gerber files with GC-Prevue.
  5. Gc-Prevue Frequently Asked Questions

    i.  Directory Structure

    To organize your data for best use, unzip <camfiles>.zip in the <_job_> directory, preserving any folder names (creating relative paths). Here is the directory structure to use for Gerber files (CAM files):

    <_job_> ___GCPREVUE

    OK. I know that looks confusing. So do this, download this tiny zip file (18 Kb) and unzip it. Besides illustrating directory structure, it will contain some information you may find useful.

    The GCPREVUEsub-directory immediately below the <_job_> directory will contain GCPREVUE.ZIP, which when unzipped enables the use of GC-Prevue setups that in turn enable you to view and print the CAM files with a minimum of effort using GC-Prevue Version 8.


    ii.  Using GC-Prevue Version 8 to view and print Gerber files.

    It will be easiest to work from a printed copy of this.

    1. Place the CAM files in their own directory.
      Unzip the CAM zip file ( <_job_> CAM.ZIP), preserving relative directories or "folder names" in a blank directory. "Relative directories" means that the sub-directory information (the path to files that were zipped up) was stored in the zip archive along with the filenames.
    2. Next, create a job-specific shortcut for GC-Prevue to make it start up in this GCPREVUE sub-directory.
      1. Make a copy of any shortcut that would start GC-Prevue, such as the one the installation placed in your start menu. Rename the copy to include thejob name. Click here if you need help finding that short cut.
      2. Create a shortcut to the <_job_> /GCPREVUE directory.
        1. Right-Click on the GCPrevue sub-directory and select "Create Shortcut")
        2. Right click on the shortcut and select Properties.
        3. Select Shortcut tab and then type <ctrl-C> to copy the shortcut path to the clipboard.
      3. Modify your job-specific shortcut to open in the correct directory:
        1. Right-Click on the shortcut created in step A.
        2. Select Properties.
        3. Select the Shortcut tab.
        4. Replace whatever is in the "Start-in" line by selecting all of it and then typing <ctrl-V> to paste the pathway to the <_job_>/GCPREVUE directory (the pathway you copied to the clipboard in step II.B.3) into this "Start-in" line.
        5. Click OK.
    3. Load in the CAM files for the board.
      1. Double click the shortcut just created.
      2. After GC-Prevue starts:
        1. From the File Menu, select Restore All.
        2. Select the filename. It would have an extension of .gwk , .cwk or .pwk)
      3. Load the CAM files:
        1. From the File Menu, select Load Layers.
        2. In the Data Type pop-up window select "Auto."
        3. In the Load Auto Data pop-up window, replace whatever number is in the Layers line with the text "all"
        4. Click OK. Any error messages encountered at this point can simply be acknowledged by clicking "OK."
      4. Close the Layers List window to get it out of the way. In the event that your screen is blank, use the menu items Zoom|Zoom Extents.
      5. You should be looking at all the layers in register, with the smallest objects drawn last so that you can can see portions of larger objects beneath. The drill holes are visible as black areas with crosshairs in them.
    4. At this point you can turn on or off various layers for viewing or checkplotting.
      • The Layer Status sub-window shows "v" or "h" for view or hidden. This can be changed by typing v or h or toggled by hitting the space bar. The same keystrokes work for the Layer List window, where the v or h is replaced with the words "View" or "Hide."
      • To get a print of a layer, toggle to View any layers you want on the print, and all others to Hide. I set up my artwork files to be in register, therefore you can easily combine more than one layer for a checkplot if you wish.
      • Hint: You'll get great looking checkplots by having in view three files:
        1. An artwork file (such as the component side).
        2. The NC Drill file.
        3. The board outline file.
      • From the file menu, select Checkplot. The Checkplot pop-up window contains many options. About the only one you might want to mess with at first is the Setup tab, for changing properties of your printer if needed, especially changing from "Portrait" to "Landscape" to match the orientation of the data on the screen.
      • I place targets on a global layer in PCB databases and at the extremities of the data so that Checkplot|Fit to Page (the default scaling option} will result in all layers plotted to the same scale. This won't be an exact integer scale, such as 2:1, but they will be all the same. Thus, two or more printed checkplots can be viewed as a stack of layers on a light table.

    iii. Checking mechanical dimensions in CAM files with GC-Prevue.

    Using "Jump-Nearest" and "Grids" to check artwork against mechanical drawings with GC-Prevue.
    There are some important menu selections that will aid in checking mechanical dimensions.

    Use CTRL-N to "jump" or snap the cursor to the board datum —The drill hole or board corner whichforms the origin or reference point for mechanical drawings. (This applies to the type of mechanical drawings that shows dimensions using cartesian coordinates as offsets from an origin.) After snapping to the board datum, use CTRL-SHIFT Z to zero the user coordinates to that point.

    After that use CTRL-N for mechanically significant objects and read their cartesian coordinates from the User grid sub-window in the upper right corner. These should match the mechanical drawing, and if so, those dimensions on the hard-copy drawing would be highlighted in yellow to indicate they were checked.

    For mechnanical drawings which use arrows, as in <---- 5.00" -----> , to show displacement between related objects, use CTRL-N at one object, then Z, then CTRL-N at the other object. The offset will appear in the Relative grid window on the right of the screen. If it matches the mechanical drawing, then that dimension would be highligted in yellow to show it was checked.


coordinates in GC-Prevue —There are three sets of coordinates on the right of the main window of GC-Prevue appearing in this order from top to bottom: Usr" (User) Abs" (Absolute) and Rel" (Relative). User is for the user, of course, to adapt coordinates (x and y) to his purposes. Absolute reflects what is in the Gerber files' data. Relative is used for getting offsets, and that group also gives the distance of offset as well as the x and y offsets.

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