RepRapMag BeginnerSpace Article on Morgan – details, refinements, questions

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    • #5898
      MacMarty15221
      Participant

      The “Morgan Visual Instructions” article in Issue 3 of RepRapMagazine is a HUGE step forward, collecting information from many forum topics into one document. It is labeled as a “BeginnerSpace” article, but a true beginner on the Morgan path (like me) may still have a few questions.

    • #5900
      MacMarty15221
      Participant

      Stepper Motors – the article calls for 2 each two types – 200 step and 400 step. There’s an inference that these need 2 types of Pololu stepper driver cards – 2 each “low-current 1/16” and 2 each “high-current 1/32”. What’s left unsaid is the torque specification for each motor, and where on the machine each type goes. Any suggestions?

      (It’s pretty easy to guess that Psi and Theta are driven by the same type, and this infers that Z and the extruder get the OTHER type.)

    • #5917
      Quentin Harley
      Keymaster

      Again, You can use the same drivers if you like. The 32th microstepping drivers gives higher resolution, and is recommended on Theta and Psi (although my first morgan printed ok with 16th uStepping and 200 step (1.8deg) motors.

      It is an economy based choice.

    • #5943
      MacMarty15221
      Participant

      [For section 4, page 73]
      The 3D printer at my makerspace seems to have some calibration issues. When I printed the “Z Mount Bottom” and “Z Mount Top”, they came out undersized.

      Rather than wrestle with the calibration, I consulted the part PDFs, and made my own parts out of acrylic. I used a milling machine to cut the holes, and now the steel rods are VERY precisely positioned at 175mm apart, and aligned with the drive-pipe assembly.

      [For section 6, page 74]
      Many people notice that the top platform does not end up parallel to the bottom platform. Quentin says that’s OK – the only thing that matters is that the print platform should be perpendicular to the drive rods and drive-pipe assembly.

    • #5981
      MacMarty15221
      Participant

      [For section 1, page 71]
      Following the instructions literally will lead you to a physical impossibility. If you thread the nut onto the shaft, and then slide on the drive wheel, you can’t thread the next nut into its socket.

      It’s best to START by inserting the two M8 nuts into the Drive-wheel-rod-mount. I used a woodworking clamp to press them squarely into the hexagonal sockets on the drive wheel. By doing this first, you will be able to thread the complete wheel assembly (nut+wheel+nut) onto the threaded rod.

    • #5982
      MacMarty15221
      Participant

      [Section 3, page 72]
      To flange, or not to flange, that is the question

      Quentin’s instructions on the Wiki suggest that one should use a F608Z bearing, a detail that is missing in the magazine. If you use a normal 608Z, it is possible for the bearing to get pushed too far up into the center bore of the drive wheel. And then the Theta wheel will be to low, and not line up with the pulley on the stepper.

      Quentin has helpfully provided a small hole in the side of the Theta drive wheel part. You can use a short M3 screw to affix the wheel to the 22mm tube.

    • #5989
      Quentin Harley
      Keymaster

      Very handy comments. Thank you!

    • #6016
      MacMarty15221
      Participant

      For today’s chapter, I have one observation about calibration, and a lot of confusion.

      OBS #1: The graphical flowchart in Morgan-Calibration-Guide is puzzling if viewed alone. If you examine it in combination with reprap.org/wiki/G-code, it will make a LOT more sense.

      And the confusions:
      If “Bed 0 is at the top right corner when viewed from the front”, what are the coordinates of the bottom left corner? [x=205, y=205] , or [X=-205, y=-205] ? If it is the former, as I suspect, then I need to turn my mental perspective around, and imagine that I am sitting on top of the threaded rod, with the print bed spread out in front of me. (0,0 at my left near corner, 205,205 at far right corner.)

      But then I am in conflict with the jog controls of Pronterface, which moves the wheels counterclockwise toward the MAX end stops when I click the +X or +Y buttons. 🙁

      I think that I am missing the Big Picture. Help?

      • #6018
        MacMarty15221
        Participant

        There are many ways to configure things incorrectly, or perceive them incorrectly. I seem to have encountered most of these. 🙂 Ignore the “confusion” part of the previous post. Not that I’ve de-confused myself or anything… I’m just the Perfect Idiot who has come along to flush out alternatives that are Not Perfectly Obvious. Perhaps by blundering along, I can collect a set of “principles of operation” that may not be evident to the new observer, who will be freed to go forth and make NEW mistakes. Here are a few samples.

        Jogging +Z should increase the distance between the nozzle and the bed. The Z stepper will move CCW, the bed will go down.

        Homing the Z axis should send the bed downward, until it reaches Manual_Z_Home_Position -or- hits the hardware “Z MAX” endstop.

        Sending an M114 code (through the interactive text line) should cause the RepRap machine to report its current X, Y, Z and E coordinates to the host. SCARA diagnostic values will also be reported.

    • #6031
      Quentin Harley
      Keymaster

      Movement on Morgan is inverted when viewed from the front.

      X+ goes left, Y+ comes towards you.

      Z+ as you rightly stated brings the bed down (to increase the nozzle height)

      It helps to place the morgan with the back facing you, but humans are amazingly adaptable. I suggest just learning to operate the controls in reverse.

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