@jlauer Here an example to see how big are the drops. The issue now, the stepper press and the paste flow to much at start.
+Peter van der Walt Yeah, i got a lot of issues. I guess the quality of my Solder Paste are to wrong. I try with this matrix to find the perfect parameters to apply dots with the same Diameter every time. I check the china air compressors, IMHO good for manual dispensing, not for a machine.
Ok the con’s for an air dispenser:
- For the time-pressure dispensing, change in viscosity is an evil but not the biggest. The amount of air necessary to build up the pressure in the barrel varies as the syringe empties.
- You need an air compressor, loud and with a big footprint.
Now i think about an Auger Pump, i found this very interesting but old thread: https://forums.adafruit.com/viewtopic.php?f=42&t=16273 with a nice photo of a stepper with a DIY Auger Pump: http://i176.photobucket.com/albums/w189/kyrylp/IMG_0003.jpg
He use this screw on the pic for an auger pump, unbelievable 
Here a schematic view for this pump: http://www.gpd-global.com/co_website/img-gpd/fluiddispense/products/microdot/fluidFlow.jpg
So, i hope to find the best solution
Now i found a very interesting old article: http://unfoldfab.blogspot.de/2012/08/road-to-better-paste-extrusion-episode.html … and i think this auger ventil are a perfect solution: http://4.bp.blogspot.com/-YYVLDuB04Yg/T-or5riCALI/AAAAAAAAARU/wNOjBgsfLMc/s1600/TS5000DMPabc.jpg
