Mirroring the ExpressPCB print out

ExpressPCB is a free and easy to learn PCB drawing cad software for hobbyist, many simple circuit application do not required complicated software such as protel PCB, primarily because numerical control automation make use of gerber file is not required.

But the problem for many user that want to make their own simple PCB is that they need a mirror print out to properly done with iron on transfer or photo resist, the printed side need to be in contact with the circuit board to achieve the best result, especially when using a transparency as photo resist, closer contact possible will make fine line as there are very limited gap for scattered light beam.

The print out can in fact be mirrored by printer setting if you do have one of this option in your printer preference. But if you don't have one, you can make use of the Windows XPS Document Writer, I found out that it was pretty easy to mirror XML drawing script. It describe exactly the pattern of the print out by script not pixel, up to capability of 600dpi.

1. Print the layer you want out by choosing Windows XPS Document Writer as your printer, mind the paper size you choose, A4 is by default, this must be the same as your printer setting for paper size.

2. Rename the print out from .XPS to .zip

3. Extract all file, in the extracted folder look for file 1.fpage in directory drive:\your extracted folder name\Documents\1\Pages\1.fpage

4. Mirror all the value of x coordinate in the file, that will mirror the entire print out. Example:

FixedPage Width="816" Height="1056".....
Path Data="F1 M 302.4,436.8 L 513.6,436.8 513.6,619.2 302.4,619.2 z"  Fill="#ff000000" /

The path data describe a filled rectangle, 302.4, 436.8 is coordinate as (x,y), just modify (can be done with computer program) all x such that:

newX = Width - oldX

The scripts will look like this after modified:
Path Data="F1 M 513.6,436.8 L 302.8,436.8 302.8,619.2 513.6,619.2 z"  Fill="#ff000000" /

Basically XML drawing script use to describe those simple image is just line and rectangle, round pad is describe as a line in revolution, all it need is just coordinate information to describe where to draw the item.

5. Rezip the extracted folder with modified contain back to .zip and rename it back to .xps, I found out that rezip using winzip won't work, right click add a new zip file and drag everything into the zip file do work very well indeed.

6.Open the modified .xps file with xps viewer or internet explorer, at the menu click print and you will have a mirrored image print out.

Alternatively this may also work with Microsoft Word image writer, but the procedure may be different or easier.