RUG/Pennsylvania/State College/Universal Paste Extruder

Components

Name	Quantity	Link	Price
Air compressor (100 PSI)	1	http://www.harborfreight.com/1-3-hp-3-gallon-100-psi-oilless-air-compressor-97080.html	$62.99
Air compressor's hose	1	http://www.harborfreight.com/20-piece-air-compressor-starter-kit-68191.html	$12.99
Air compressor's hose to nylon hose adapter	1	http://www.wicvalve.com/Male-Connector-Tube-OD-1-8-X-NPT-1-4-Air-Instant-Fitting-PMC-T1-8-N1-4.htm	$0.94
Solenoid valve (12 V)	1 per extruding syringe	http://www.wicvalve.com/1-8-Inch-3-Way-Pneumatic-Electric-directional-Solenoid-Valve-3AK-1-8-G.htm	$16.76
Solenoid valve to nylon hose adapter	3 per extruding syringe	http://www.wicvalve.com/Male-Connector-Tube-OD-1-8-X-NPT-1-8-Quick-Release-Fitting-PMC-T1-8-N1-8.htm	$0.94
Nylon hose to syringe adapter (10cc)	1 per extruding syringe	http://www.dispensinglink.com/10cc%20syringes.htm	Not on website, ask for the price catalogue (service@dispensin glink.com)
Plastic syringe (10cc, luer-lock)	1 per extruding syringe	http://www.dispensinglink.com/luer_lock.htm	Not on website, ask for the price catalogue (service@dispensin glink.com)
Nylon hose	1	http://www.grainger.com/product/NYCOIL-Tubing-2VDL5	$10.37

Generating the gcode and printing

Slic3r (http://slic3r.org) can slice a CAD file into G-code for the paste extruder. It requires specific settings:

• Go to Preferences and turn Slic3r into expert mode

• Print settings:
  • Layers and perimeters:
    • Set the layer height to the right value (this value depends on the paste, and must be determined through experimentation)
    • Set first layer height to 100%
  • Speed:
    • In the set for print moves sub-section, all the values should be identical, and equal to the printing speed determined through experimentation (it depends on the paste, the nozzle and the pressure)
    • The speed for non-printing moves can be left to its default value
    • Set the first layer speed to 100%
  • Output options
    • Download the perl script to turn extrusion commands into fan commands (Paste-perl.zip), and place it in any folder (don't forget to un-zip it). Then add its absolute path to the post-processing frame. On Unix, open the terminal and run the command "chmod 755 /path/to/the/script". Make sure that there aren't any white-spaces in the script's path (it may result in a crash). On Windows, you need to download and install a Perl interpreter: http://www.perl.org.
  • Advanced:
    • Set the first layer to 100%

• Filament settings:
  • Cooling:
    • Disable both options (fan always on and auto cooling)

• Printer settings:
  • General:
    • Set the G-code flavor to MakerWare (MakerBot)
  • Extruder 1:
    • Set the nozzle diameter to the right value (this value depends on the paste, and must be determined through experimentation)
    • Set the retraction length to 2 (disabling it provokes a bug)

The post-processing script used turns the extruding commands into fan commands. If you plug the solenoid valve on the fan port, you won't need to re-flash the printer. Note that if you don't re-flash it, since there is a temperature security, you must left the regular extruder's thermocouple or thermistor plugged (considering that you took a working printer and replaced the extruder).

In order to determine the right values (this hasn't been done yet, and must be followed with caution):

• The layer height is close to the height of a printed paste line.
• The nozzle size shouldn't be set to the actual nozzle size, but rather to the printed paste line width.
• The speed depends on the nozzle size, the viscosity of the paste and the air pressure. Try to find values that result in a good print for these 4 parameters (including speed).