i wonder if the money saved outweighs the cost of a laser cutter….

These instructions are partially wrong…I’ve been cutting stencils from Eagle files for about a year. He’s right about the Eagle PDF export causing problems, I’ve been using Inkscape to open it and save in a format Corel understands.

The main thing he’s wrong about is the actual sizing of the cream outlines. You can see a lot of his pads actually overlap, this will allow too much solder to be deposited and cause bridges during reflow. Due to the kerf left by the laser cutter you need to shrink the outlines by a few mil. I usually go into the DRC Mask section, and on the Cream part I set a max of 10mil and a percentage of 20% or so. Then export the cream layer.

For 2mil mylar on a 45 watt laser, I tape the plastic on smooth birch plywood and cut the outlines in vector mode with 8% speed and 3% power. That seems to eliminate most of the melting and rough edge problems people complain about with mylar. It actually sticks most of the chads to the plywood, so when you pull off the stencil it automatically weeds most of them.

Here’s a picture of one stencil I made: http://www.flickr.com/photos/macetech/3311194156/

And here’s a video of cutting a stencil recently: http://www.twitvid.com/5F80B

This is going to be exceptionally useful, given I have access to a laser cutter and do lots of SMD work. I’ve always wanted to try to make stencils on the lab laser cutter, but this is a good head start.

We’ve been figuring out how to get extremely fine pitch stencils on kapton (polyimide) film out of our laser cutter, and have found that you need to not only adjust the cream layer, but you need to adjust the aperture of your gerber as well, depending on how the beam of your laser cuts.

It’s fairly straightforward in principle, but like most things, it takes a bit of practice.

Details are here.

http://wiki.metrixcreatespace.com/laser-cutter

@macegr

You are right about the laser kerf and the need to shrink the size a bit. However this post was just to show the guys in http://www.theqlabs.com‘s hardware hacking class how I made their stencils. I know lots of people use mylar however I have learned that using a higher grade card stock paper works better. Mylar starts to melt and the edges are not super clean. Mylar is better in the long run for multiple uses (meaning multiple days). But the paper does not melt and edges are 100% straight.

@mrgoogfan
If this is all you used the laser for then I would say No… I use mine for alot of different stuff check out my flickr stream.
http://www.flickr.com/photos/rileyporter/

Before he has even finished processing the Eagle files, I’ve been pasting up my whole board using the classic syringe method.

If you need to make many (large) boards, then this would have been faster, but considering a pro stencil cost only $90 for a 24″x24″ frame, why bother.