RUG/Pennsylvania/State College/Universal Paste Extruder

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This page is dedicated to providing detailed information on how to build and use a universal paste extruder. These types of extruders are becoming more and more popular as can be seen in the media timeline.

Types of Materials That Can Be Used







Related Projects and Results

Below are details about paste extrusion projects that have been completed by students using this extruder.

Name Students Link Description


Name Quantity Supplier Link Files Price
Gear and drive set (small gear, medium gear, large gear, idler block, syringe pressure block 1 Thingiverse [1] [2] n/a
Plastic Body V2 Extruder 1 Thingiverse [3] [4] n/a
NEMA17 motor 1 Stepper Online [5] n/a $10.76
T5 10teeth Metal drive Gear 1 Thingiverse [6] [7] n/a
624 Bearings 4 VXB [8] n/a $6.95 each
608 bearing 1 3DMakerWorld [9] n/a $0.75 each
20mm M8 Smooth rod 1 Make Mendel [10] n/a $24.99
55mm M4 Bolt 1 Home Depot [11] n/a $1.76/2 pack
75mm M4 bar or bolt 1 [12] n/a $0.96 each
M4 Hex spacer (or M4 wingnut) 1 DigiKey [13] n/a $0.65 each
M4 plain nuts 2 Fastenal [14] n/a $0.30
M4 Nylock nuts 4 Hobby Express [15] n/a $2.29 per pack of 10 nuts
M3 Nuts 6 Hobby King [16] n/a $0.79
20mm M4 bolts 2 Amazon [17] n/a $4.98 per pack of 100
10mm M3 bolts 5 Ultimachine [18] n/a $2.99 per pack of 50
M3 washers 14 Ultimachine [19] n/a $1.89 per pack of 100
45mm M3 bolts for Idler 2 Open Builds Part Store [20] n/a $0.25
springs or Silicon pressure spacers for Idler 2 Ebay [21] n/a $5.74 for pack of 4
small zip tie 1 Amazon [22] n/a $2.18
5-6mm wide T5 belt ~about 40cm 1 RI [23] n/a $15.00
Plastic sheet 1 Amazon [24] n/a ~$12.00


Slic3r: Generating Gcode

Slic3r can slice a CAD file into G-code for the paste extruder. It can be downloaded here. Slic3r requires specific settings which can be set following these directions:

1) Open Slic3r
  • Click "Preferences" and select "Expert" from the drop-down menu next to "Mode"
2) From the "Print Settings" tab
  • Layers and perimeters:
    • Set the "Layer Height" to the right value (this value depends on the paste, and must be determined through experimentation, usually about equal to nozzle diameter)
    • Set "First Layer Height" to 80% of Layer Height
  • Infill:
    • Change "Fill Density"
      • Higher density will obviously take longer, but is better for parts that actually function.
  • Speed:
    • Speed for print moves"
      • 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
    • Modifiers:
      • Set the "First layer speed" to 100%
  • Output options
    • Download the perl script to turn extrusion commands into fan commands (, 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:
  • Advanced:
    • Set the "First layer" to 100%
3) From the "Filament Settings" tab
  • Cooling:
    • Enable:
      • Disable both options (fan always on and auto cooling)
4) From the "Printer Settings" tab
  • General:
    • Firmware:
      • Set the "G-code flavor" to MakerWare (MakerBot)
  • Extruder 1:
    • Size:
      • Set the "Nozzle diameter" to the right value (depends on the printer)
    • Retraction:
      • Set the "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).

Pronterface: Starting a Print

Pronterface is software that controls RepRap printers, and prints using a sliced Gcode file. It can be downloaded here. The following directions will help you set up Pronterface:

1) Open Pronterface
2) Connect printer
  • Select correct COM port from drop-down menu next to the "Port" button at the top of the screen or type in the correct port yourself (port number can be found in the control panel)
  • Click "Connect" button along the top of the screen
  • Check to see that the printer _____
3) Click the "Load file" button along the top of the screen and open your Gcode file
4) Remove coding that prevents printing until temperature stabilizes
  • Click "Tools" tab at the top of the screen
  • Select "Edit..."
  • Find line of Gcode that begins with "M109" and insert a semicolon before it to comment it out
5) Set hot tip temperature
  • Type printer's tip temperature in the box next to "Heat:" along the left side of the screen
  • Click "Set" button
  • Check to see that temperature is reached:
    • Select "Watch" box below "Check Temp" button to watch temperature increase on graph or...
    • Click "Check temp" button and temperature will appear on right side of screen