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I am building what I dub Frankenstein's printer from various components I could find in the electronics dumpster to print the proteins for a P3 Steel (toolson edition).

I want to elevate a scanner bed with an attached DVD drive motor for X-Y movements of the hotend. I plan to connect this by threaded rods to a base that also hosts the heated bed on a stury z-axis mechanism. To make this as stable as possible, I plan to conncect M8 threaded rods in the 8 edges in wooden blocks.

I am planning on 4 vertical rods and 2 crossing rods along the diagonals of the backside of the system. Additionally each side is planned to have one diagonal connected by a rod.

We're talking about a height of about 30cm and M8 rods. Will this introduce lots of vibrations and is it possible to avoid easily? Are there any better connection ideas or improvements I can make to this design?

*edit: here is a really bad hand-drawn sketch: hand-drawn sketch

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    $\begingroup$ do you have a schematic, 3D model or image that you could include in your question? That would certainly be of help to better understand your situation. $\endgroup$
    – Tormod Haugene
    Mar 10 '16 at 12:35
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    $\begingroup$ up to now i have successfully avoided getting into a CAD program (next on the list). I will include a pretty bad drawing (my skiills here are as well developed as the CAD ones) as soon as I have the time. $\endgroup$
    – kamuro
    Mar 10 '16 at 14:39
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    $\begingroup$ Even a pen-and-paper sketch would help enormously. $\endgroup$
    – Ryan Carlyle
    Mar 10 '16 at 20:37
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    $\begingroup$ That sounds ok for light duty; the main thing I'd worry about is that threaded rods are weak under compression and flexion. That might mean you end up with vibration, or just inaccuracy. Perhaps consider substituting something more rigid (angle stock, T-extrusions, etc) for some or all of the places where stiffness is important? $\endgroup$
    – TextGeek
    Mar 14 '16 at 18:02
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If I understand you correctly, compared to a Mendel RepRap you are using:

  • M8 threaded rod (the same kind of rod used in the Mendel RepRap frame)
  • roughly the same lengths of rod as in the Mendel, and
  • cross-braced with more diagonals than the Mendel design.

So I expect less vibration and the same print quality as a Mendel.

Rather than put one block of wood at each corner with holes drilled at a bunch of weird skewed angles, the "1X2 split vertex" looks like it is a lot easier to construct.

I've heard several people claim that lots of threaded rods and associated corner connectors can be replaced with a few big sheets of wood in a 3D printer. See Mendel90, RP9, SGBot, WolfStrap, etc.

Looks like a very educational project. Good luck.

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    $\begingroup$ To split the blocks up into their angular parts is a great idea. I was stuck with one block since I had the minimization of vibrational possibilities in mind. I guess when screwed tight the vertex should easily do the job. This was really helpful input, I didn't know about the 1X2 design... $\endgroup$
    – kamuro
    Mar 16 '16 at 9:20

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