MOST Delta RepRap Mod[edit | edit source]

Thrown Rod Halt[edit | edit source]

Project developed by Bwbarker

  • This modification has been prototyped and is functional.

Abstract[edit | edit source]

  • I know everyone of us with a MOST Delta RepRap has thrown a rod at some point during a print. Even when you finally have a very well calibrated printer it is still possible that your hotend runs into your print or your hand as you try to fix something you don't like before your printer head comes back.
  • Since the end effector, rods, and carriages are all magnetically attached we can use this system as a fail safe or pause switch. When connected to the power selector, this system will also turn off the hot end which could potentially prevent an unattended printer from catching fire.

Bill of Materials[edit | edit source]

Tools needed for fabrication[edit | edit source]

  1. MOST Delta RepRap or similar RepRap 3-D printer
    1. Requires a printer with magnetically attached diagnonal rods
  2. Wire strippers

Skills and Knowledge Necessary for this Mod[edit | edit source]

  • Some knowledge of your firmware and host software
  • A very rudimentary knowledge of circuits and multimeters

Technical Specifications and Assembly Instructions[edit | edit source]

  1. Remove all the aluminum rods from the printer and set the end effector aside.
  2. String copper wire from on ball bearing to the other on each rod.


  1. Apply the electric paint generously to each end of the wire to ensure a good contact
  2. Apply electric paint between the magnets on both the end effector and carriages as shown in black:

Circuit1.jpg Circuit3.jpg

    1. Be sure to have good contact between the paint lines and the magnets, this is a week point in the circuit that may require some extra paint.
      1. !!! Do Not  !!!! Hot solder the magnets as heat will damage or ruin their magnetic properties
  1. Measure the resistance of the completed circuit, it should be as low as possible preferably on the order of 100 Ohms or less.
  2. Connect the completed circuit to one of three pins depending on the application and total resistance. Melzi Board Layout
    1. Connect to the power selection pin, this will cause the whole printer to shut down in the event of a thrown rod.
    2. Connect to the bed temp pin, this will allow you to monitor the circuit and set a threshold
    3. Connect to your firmware's pause or 'filament out' pin. (coming in Repetier firmware V1.0)

Common Problems and Solutions[edit | edit source]

  • The most common problem that I have found with this modification is the total resistance related to the final circuit.
    • In order to overcome the majority of the resistance, extra wire needs to be strung between the ball bearings to eliminate the aluminum rods from the circuit.
    • Conductive Grease will also be helpful if you grease between your ball bearings and magnets.

References[edit | edit source]

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