CNC Router, Plasma, 3D Printer, combo unit.

Discussion in 'Workshop Tips and Secrets / Tools' started by Armilite, Sep 18, 2018.

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  1. Oct 15, 2018 #61

    pictsidhe

    pictsidhe

    pictsidhe

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    Use polythene and a very sharp cutter and the rib should just pop out when you flex the mould.
    Start at the nose with two strings. Twist them at intersections between truss and surface strings and it will be very strong.
    I will steal this idea!
     
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  2. Oct 15, 2018 #62

    proppastie

    proppastie

    proppastie

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    I was thinking thin thread, going into all the paths/elements continuous multiple times. Have to work out the truss style and tow routing but I think it could be done with 30/60 degree truss elements.

    If aluminum male/female could stick it in the oven or use heat pads and use the fancy heat cure/stronger epoxy with bleed cloth and pressure... just like the big boys.

    But warp is a problem maybe room temperature is the way to go.

    Normally if all the cross sections are uniform like 1/8x1/8 square, warp is a minimum, check out a typical plastic part.
     
  3. Oct 15, 2018 #63

    FritzW

    FritzW

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    The way I was thinking it'd take a minimum of three wraps (three trips around the mold) to make one complete layer of two strands. Depending on how thin the tow was it'd take several sets of these "three trips around" to fill the mold.

    To get back on topic before Armilite throws us off the thread: ;) if the tow was very thin you could mount a small wire loop on your combo CNC machine (like a dull sewing needle that was bent on the end) and have it wrap a whole bunch of tiny layers really fast.

    Rib Wrap R2.jpg ...just for fun, my take on the proppastie rib

    Rib Wrap.jpg three times around the mold would give everything at least two layers (the middle two layers in the picture are just an exploded view of one layer)

    Rib Wrap Stereo.jpg I did a stereo view so I could see what I was thinking :gig:
     
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  4. Oct 15, 2018 #64

    Jay Kempf

    Jay Kempf

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    Wouldn't you have to get more bond area where the zigzag meets the outline of the profile than that? What if you just put straights instead of the zigzags and those straights had extra outboard. Then you wrap on a profile, then you fold over the straight to complete the zigzag and as many times as you needed for however many layers. Then the outline would be interlaced with the struts....
     
  5. Oct 15, 2018 #65

    proppastie

    proppastie

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    yes.....like cad path idea, see if you can go continuous for example portion of top mold line to first truss element then down to the bottom mold line, then over to the next truss element and up to the top mold line. I think without playing with it,... if there are odd number of elements the missing portions of the mold line will fill in on the next pass.

    Edit:Just though about what you did, and probably just as good and easier than what I suggested above.
     
    Last edited: Oct 15, 2018
  6. Oct 15, 2018 #66

    proppastie

    proppastie

    proppastie

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    That we could have a 3D male/female mold the "bulges" could certainly be accommodated in the mold...

    One of the issues is a non-uniform x-section may cause the part to warp if it is oven cured for optimum strength.

    However using room temperature cure, and lots of bleed cloth, the male/female mold could be bolted together for a very considerable squeeze for optimal/minimal resin content, which is also great for optimum strength.
     
  7. Oct 15, 2018 #67

    pictsidhe

    pictsidhe

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    Polypropylene will take 200F and is way cheaper than teflon which takes a lot more. Unfortunately, like most plastics, it has a high CTE. So things will need to slide fairly freely during warm up or it will distort. That could be tricky.
    How about a tiny shoe following the placing loop to push the tow into the groove a bit?
    Infusion will save a lot of mess.

    Should we call this the HBA rib?
     
  8. Oct 16, 2018 #68

    proppastie

    proppastie

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    maybe we should start out with room temperature cure.

    I was thinking machined alum. for the bolted mold, but perhaps the printed mold could take a moderate amount of weight piled on top of it.

    I think the goal should be to replace a wood truss rib, and some analysis needs to be done to decide exactly how small x-section in CF vs say 1/4 sq. wood, and how much weight would be saved.

    I like the auto infusion idea.
     
  9. Oct 16, 2018 #69

    FritzW

    FritzW

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    Yep, good catch!
     

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