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Mendel 90 3D Printer



200mm by 200mm by 200mm build volume. The X and Y are actually a little less than that but the Z is actually about 208mm.

Equipment Settings

As long as the Slic3r settings match with the filament size temps the only other setting for the printer itself is the nozzle diameter. Current hot end is 0.4mm

When connecting to OctoPrint if the printer (the arduino) isn't connected to the RasPi then use:

  • Port: AUTO
  • Baudrate: 115200

Normally OctoPrint should be connected to the printer If the options to upload or connect aren't there then you need to log in. If you don't have a username/password then you probably haven't been certified.

Troubleshooting Problems

  • Print not sticking to bed
    • Any Material
      • If the base or first layer of a print is relatively small then using the brim setting in Slic3r might help. Turn it on if you're not using it or increase it's size if you already are. The brim setting is in mm and it's the distance from the print base it builds the brim out to. Depending on the print this could be relatively high (20 mm).
      • Check the heated bed settings. ABS needs ~100C or perhaps even higher while PLA or PLA/HPA works best around 60C
      • If you're printing in small layers (<.3mm) then check the first print layer setting in Slic3r. Set this to a higher value. The gcode will put down a thicker layer for only the first layer to help the print adhere to the bed.
    • ABS
      • To adhere to glass well you need to use a “slurry” of ABS and Acetone. This puts a thin film of ABS on the glass when it dries and helps the print adhere. When the bed cools this will release and it's not a problem getting the print off the bed. There should be a small mason jar with the mixture in the printer cabinet.
    • PLA or PLA/PHA (ColorFabb)
      • Since there isn't a readily available solvent for PLA the adherence to the bed seems to be most affected by how clean the bed is. If there are any traces of ABS then clean the bed thoroughly with Acetone and then clean it again with isoproplyl. Any oils/dirt/dust/anything on the bed seems to affect the adherence a lot. PLA seems to adhere better than PLA/HPA but both work on the glass bed if you prepare it properly.
  • Printing won't start from Octoprint
    • Octoprint, for various reasons, disconnects from the Arduino. Manually homing the Z axis is an example of a command that will disconnect the Arduino – not sure why yet. Can be fixed by reconnecting from Octoprint.


The firmware has been modified to make extruder 1 (of extruders 0 and 1) behave like extruder 0. There was a magic smoke event that cooked the current limiting resistor for the extruder 0 heater.

What Could it Use?

  • User:KHawkings will be working on a Bowden Tube based extruder to move the stepper and cold end off the X-Carriage
  • A mounting system/brackets/case for the LCD screen
  • A Cover/Case/Fan Mount for the electronics
  • The X carriage is noisy. It's probably because the linear rods are slightly smaller than the bearings. 8mm rods should be swapped in.
  • Mounting system/brackets for the RasPi and USB Hub
  • Carrying Handle
  • Replacement of the resistor for extruder 0 (I think it's a 0805 smd but no idea on the resistance).

If you're willing to tackle any of these please let someone know.

Known Problems

If the hot end stops making itself hot then unplug and plug back in the connectors for the hot end on the x-carriage (the 4 pin connectors to the protoboards)

Occasionally the filament stops being extruded. In order of frequency it's probably:

  • The filament has been “stripped” on the hobbed bolt. Take the panel on the right off the extruder, remove the big gear and hobbed bolt and clean them. There was probably an issue with the filament feeding that caused this.
  • The small gear has moved/shifted/started to slip on the stepper motor shaft.
  • The connector to the stepper motor is loose. Reseat it.

Future Ideas

  • Add more feedback/failsafe controls.
    • Additional limit switches w/ failsafe wiring.
    • Extra temperature sensors
    • Rotary encoder or other measuring tool for filament
    • Reporting code to feed back on alarms, such as limit switch failure.

Useful Software / Websites

FreeCAD – A CAD program that can produce STLs and interchange many CAD formats (even some support for OpenSCAD)

Slic3r – A slicing tool preferred for use with the ENTS Mendel90 (config file below).

NetFabb STL Repair – A tool for repairing broken STL files.

Thingiverse – A place to find things to print. Don't reinvent the wheel if you don't have to (or unless you want to)!

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ENTS provides 3D printing filament on a reasonable-use basis. Members are free to use the available filament at not cost, however, if your project consumes an appreciable amount of filament you are asked to replace the filament.