Re: creating stencils

[Michael Ross <michael e ross gmail com>]

Dear William,

My first choice to make accurate masks is a CAD program.  At least with CAD it is easy to have precision in the relative lengths of the various items in the drawing. 

The printer must also be calibrated properly - that means you need a printer that is high end enough to have the ability to be calibrated.  Many good office laser printers have the capability to be calibrated, but how that is done may not be obvious - it may be something the service personnel can do, but you may have no documentation to go by.

The alternative is to actually measure shapes on paper to see how they software, printer driver and printer are all working together.  Then you can scale your virtual mask to produce reasonable PCB masks.

Mask and stencil are in some ways synonymous.  

I think you may find printing images of an exact size with Dia to be less than easy.  Not to discourage you, but to warn you incase you are in a time sensitive mode.  Here are a couple of helpful hints.  
To show a grid go to File/Preferences, select the tab Grid Lines, and set the grid line color to something that contrasts wit the background color. 
In the tab Diagram Defaults set the paprt size to what you want to use (it comes set to A4 paper).  Here you can also set the background color and whether the sheets are portrai of landscape in layout. 
In the tab View Defaults set the page break line color to contrast with the grid and the background.  Set the page breaks to be visible.

Each drawing (create a new one to see) can have settings for paper size and layout, go to File/Page Setup to change this, and notice the margin settings.  Also notice the Scale setting.  Set Scale to 100 for a US letter alndscape and the page will be close to filling you monitor screen. Higher numbers show more pages (I am not clear what a scal of 1 or 100 means but you can use this cahnge the visibility of the pages of the diagram.

THIS IS VERY IMPORTANT: Units in Dia are centimeters. The page break lines you see in the workspace are NOT the edges of the paper you have chosen.  These are the perimiter of the margins inside the paper size.  For example if you had the following margins set for a US letter size paper (8.5inches x 11.0inches):

top = 0.25inch = 0.635 cm
bottom = 0.25inch = 0.635 cm
left = 0.5inch = 1.27cm
right = 0.5inch = 1.27cm

This would mean the area between the page break lines is 8.0 inches x 10 inches. 

You can turn on the grid at Diagram/Properties. Uncheck the Dynamic Grid, and set x and y Spacing to 2.54 and leave the Visible Spacing to be 1 and 1.   Diagram/Colors changes the grid lines and page break colors for this particular Diagram.

At the bottom of the Diagramming window are two icons to toggle grid snapping and object snapping.

I think a nice quick check of you printer would be to set the all as I have described above, set the magrgins, set to grid snapping ON.
Draw a rectangle around the extents of a single sheet, snapping it to the exact corners of the page 
and maybe draw another rectangle one grid inward to make a box that is 7 inches by 9 inches. Set the rectangle properties to Draw Background NO so you can see the grid behind them.

Print this out NOT "Fit to page," but use instead Actual Size (or whaterver you printer driver calls these things).

You should get two rectangles that are exactly 8 inches by 10 inches, and 6 inches by 8 inches.  That latter offset exaclty one inch inward from the outer.

Measure those two reactangles as printed and see if you need to make changes.

Your best bet to make exactly sized shapes is to have the grid set to some minimum desired resolution and only draw to grid snaps (coiunting then in between to get the size right).  This is not at all practical, but you have no other choice that I know of.  Getting a CAD program is the better solution.  Dia was not designed to make precisely dimensioned shapes on paper.

Good luck,

Mike

On Fri, Mar 13, 2009 at 5:52 PM, William Estrada <MrUmunhum popdial com> wrote:

Hi group,

 I need to create a paper template to use for a mask on a PC board. I plan to
use DIA and I need to know how to create one. I think they are called stencils(?).
I would like to get a mask with the holes at .1 inch spacing and then create
the sheets representing IC to overlay the the PC board image.

Any pointer??

--
William Estrada
MrUmunhum popdial com
Mt-Umunhum-Wireless.net ( http://64.124.13.3 )
Ymessenger: MrUmunhum


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-- 
                    Michael E. Ross
ArcAngle Design & Analysis | MX Automation
=================================
Bachelor of Science Mechanical Engineering
  Machine & Product Design - SolidWorks
    Data Acquisition & Control - LabVIEW
      Finite Element Analysis - Cosmos

 
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