Prusa Mendel Documentation

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Revision as of 11:59, 5 February 2013 by Mirage335 (talk | contribs) (→‎To Do)

This is the page on how to use the newly built Prusa Mendel (iteration 2). A PC has been dedicated to run it, below you will find the toolchain used to run it and other details that you may find useful.


Current Machine Status



CAD/Thingiverse -> Netfabb -> STL -> Slic3r -> Pronterface -> PRINT!

Any modelling software that can output the file format STL.
Some programs of interest might be the following: Google Sketchup, OpenSCAD, TinkerCAD, Solid Works, AutoCAD, Rhino.
And in case you don't want to model anything and simply want to print stuff, go to Thingiverse.
software for checking the "3D printability" of the model you created. Go to Netfabb and download the Studio Basic option. You can also simply use their cloud offering and have a repaired model emailed back to you.
if your model has issues, run the repair function with default settings and see if that remedies the issues. The repair function can be used by clicking the "first aid" symbol found at the far right on the tool bar.
current format for 3D printing (AMF is coming around the corner).
at this point, your file should be patched up and ready to print.
software for creating 3d printing toolpaths
precompiled binaries can be had from or be built built from github.
use the profiles already generated for best results.
GUI for controlling the Prusa.
where you will connect to the printer, home, warm up and send print jobs from.
can be built from github or download precompiled binaries for Windows/Mac here.
preview G-Code generated by Slic3r.
File is good to go, toolpaths are generated, time to let the robot do what it does best, PRINT!


  • PLA
  • ABS
Polylactic Acid
made from corn starch, smells like waffles/syrup while printing
extremely ecologically friendly
less prone to warping
more brittle compared to ABS
needs a fan, it remains much more molten after being extruded
lower operating temperatures (160C-200C)
Preferred plastic of choice
burns when heated too long
same plastic in which LEGOs are made of
higher operating temps (220C-240C)
smells like death, releases small quantities of hydrogen cyanide
requires a heated bed (110C) or warping occurs
requires kapton/PET tape on heated print surface for best adhesion. Possibly a light sanding of the surface and slurry of dissolved ABS in acetone for further warp prevention.

Machine Setup/Specs

This Prusa is fitted with the following:

  • Melzi - loaded with the latest Marlin firmware (as of 9/1/2012)
  • 12V 30A PSU
  • Makergear 0.35mm for 3mm filament hot end
  • LM8UUs
  • GT2 (2mm) belting and pulleys (5mm bore, 20 tooth)
  • 100K Thermistors (extruder an heated bed)

For FW reference on steps per axis: (80, 80, 2560, 666.67) {X, Y, Z, E}, this is also assuming 1/16th microstepping.



  • Power Supply. NEVER leave ATX power supply on after leaving HacDC, it gets hot.
  • Loose wires. Short circuits can cause severe damage.
  • X/Y endstops. Manually push X/Y axes to test the switches.
  • Z-axis endstop. Visually check that it will trigger before severe crash into print bed.


  • Grease smooth rods and Z-Axis threaded rod if axes show signs of binding.
  • Only grease with PTFE SuperLube, kept at HacDC next to RepRap.
  • Floss the hobbed bolt in the extruder.

Bed Cleaning

  • Polycarbonate bed should be kept flat, without excessive protrusions. Scrape excess plastic off, and trim deep cuts.
  • Glass bed must be clean, but not too clean. Best practice seems to be wiping with a paper towel, and then gently brushing dry fingers across the glass.

Print Depth

  • First-layer depth. For polycarbonate beds, this must be <0.4mm below the bed surface. For glass bed, exactly 0.2mm above the bed surface is required.
  • Z-axis height. Z-axis endstop position sets depth for entire bed.
  • Z-axis level. The dual threaded rods must be kept aligned.
  • Bed leveling. Place Z-axis just above bed, then move X/Y axes. Place thin paper strips under bed until level.


  1. Emergency Stop. Be ready to unplug USB cable when beginning X/Y/Z motion.
  2. Go through the maintenance list as necessary, especially the safety section.
  3. Check which bed you are using. Polycarbonate (lexan) bed is strongly recommended.
  4. Turn on power strip. Switch on the ATX PSU behind the machine. Large fans should start spinning.
  5. Load an STL model onto the dedicated laptop for printing. If you haven't made one, download one from Thingiverse
  6. Clean the STL model with netfabb. Alternatively, use netfabb studio basic to clean the model manually.
  7. Open Slic3r. Drag your STL file from a file manager onto the "Drag your objects here" box in Slic3r.
  8. "Print settings: Cheap" "Filament: Solid" "Printer: HacDC" Use these settings to print fast, with minimal plastic, high strength, and reasonable droop on short bridges.
  9. Export G-Code in Slic3r. This can take a while, so proceed to the next steps without waiting.
  10. Open pronterface.
  11. Connect to the printer. Check box "Watch" to see temperature readings. You should see about 20C on all temperature sensors, and basic stats in the console window.
  12. Set heated bed to 45C.
  13. Wait for Slic3r to finish. Click "Load" and load the G-Code file you have created. A preview of the first layer should appear in the middle of Pronterface. You can click on the preview and walk through the layers by holding shift and scrolling on the trackpad. In the console, a time estimate for the print should also appear.
  14. Set extrusion heater to 185C.
  15. Extrusion rate in pronterface should be 50mm/min or less. Faster speeds while priming can grind filament.
  16. Wait for it to hit temp and prime it. You can do this by either manually turning the large extruder gear or pressing the "Extrude" button. Do so until there is a nice and steady flow.
  17. Once all temps are hit and stable, file is loaded and extruder is can now hit print!
  18. Sit back and watch as the printer homes itself and sprints off to print your file!

Please Avoid

You are adding to the workload on a shared machine. Please be gentle.

  • NEVER leave ATX power supply on after leaving HacDC, it gets hot.
  • Extrusion rate in pronterface above 50mm/min grinds filament, and may wear out the extruder bolt.
  • Printing faster than 65mm/s and non-print moves above 100mm/s incur excessive stress.
  • Manually moving Z-axis threaded rods delevels machine, which takes time to fix.
  • Polycarbonate bed above 45C will have extremely strong adhesion. Even if you can remove your part, you will likely warp the bed doing so.
  • Paper/kapton tape defiles the glass bed. Use tape only on polycarbonate bed.

Slic3r Settings

Print Settings


Default Fast, minimum material use. Virtually all parts will not benefit from the other settings.


Same as cheap, reduced speed. Some artistic parts with thin walls will benefit.


Very low speed, nominal layer height, extra perimeters. Intended for extreme non-structural (artistic) components.


Solid, faithful parts. Use only for engineering parts requiring extreme strength (>10kg force across a few square millimeters). Voraciously consumes plastic, please use only if warranted.



185C Extrusion Temperature. Maximizes strength. Bridges >~3mm will droop badly.


175C Extrusion Temperature. Balances strength with better bridging.


167C Extrusion Temperature. Can pass the bridge test. Reduced mechanical strength, best for artistic parts.

Printer Settings

Leave at "HacDC" unless you feel they need debugging.

To Do

  • Tune trimpots on motor drivers
  • More Cable Management (Spiral wrap loose wires and ziptie down)
  • CRITICAL: Add new software load to dedicated laptop.
  • Add some example printouts to the wiki.
  • Print spare parts.