Peter wrote an article detailing his prototype solder-paste extruder:
The prototype that I put together is more of a sketch in hardware to help me appreciate the issues of paste extrusion, and help hammer out a design. Instead of using a plunger, I’ve used a very long lead screw that acts as the plunger, and has a gear atop with a captive nut to transfer force. The gear is driven by a Parallax continuous rotation servo, which I thought I’d try given that it simplifies the design by having an integrated gear box (which gives it lots of torque), and it can be directly driven by a microcontroller rather than requiring a separate stepper driver.
More details at Tricorder Project.
Nice!
I have my g-codes turn on an off a solenoid valve that uses compressed air to drive the syringe – lust like those $100 odd dollar dispenser machines. It works really well.
There are some little tricks to getting the paste on the board to snap off correctly, I.e. A small gyration of the paste head, but it is simple and awesome!
Here is a little video of it in action
http://youtu.be/tLs8p8pv0No
Sam, @samotage