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How would one make a pyramid shape?

HouseOfBreadCrumbsHouseOfBreadCrumbs Member Posts: 13
edited October 31 in Using Onshape
I tried searching online for an answer to this question before I asked the question but to no avail. There are some videos showing how to make a tetrahedron but my question is how to make a traditional pyramid with 4 sides (triangles) coming to a point and a flat bottom. The thing is though, I don't just want a pyramid shape per se, I am building something that I am actually going to have to create in real life, i.e. a pyramid out of a 3/8" flat acrylic sheet. Thus, each of the sides needs to be separate piece that I can cut and assemble together to form the pyramid. That is where I am having difficulty. Is there a way to create it so various calculations are done for me, such as the bevel angles to cut the triangles at? My project is here: https://cad.onshape.com/documents/be1cf4cd738c3fe03182dca4/w/64f757abb31dce8e28e63dc8/e/c68c9b9bb7b48446644542ca

You can see from the front of the object (where the orange part is) where I am trying to create the pyramid shape. Is there a way to make it so the edges line up neatly and bevel exactly as I need them to depending on how tall I make the pyramid?

Thanks for your help :smile:
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Answers

  • 3dcad3dcad Member, OS Professional, Mentor Posts: 2,423 PRO
    Just something out of blue, never had to make pyramid before.

    - Sketch rectangle
    - Extrude pyramid using 'Draft' checkbox
    - Shell to proper material thickness
    - Create planes with line & angle on corner
    - Split using those planes
    - Remove unnecessary parts



    I'm sure there will be a contest to make it with fewer features and end up with parametric feature script to make any pyramid in seconds. But this was the first idea I had when thinking this shape.
    //rami
  • owen_sparksowen_sparks Member, Developers Posts: 2,455 PRO
    I'd have lofted a square to a point and then done exactly as @3dcad ; describes above.
    Owen S.
    Production Engineer
    HWM-Water Ltd
  • HouseOfBreadCrumbsHouseOfBreadCrumbs Member Posts: 13
    edited October 31
    @3dcad
    I'm trying to follow your suggestion but can't quite seem to get it.

    1. Sketch a square

    2. Extrude using draft checkbox


    3. Shell to proper material thickness... do I select all the faces? I don't understand what do to at this step.

    Also, if I use a rectangle that is not a square then drafting does not form a pyramid shape with all faces coming to the same point. Instead it looks like this:

  • owen_sparksowen_sparks Member, Developers Posts: 2,455 PRO
    Click the "Hollow" checkbox at the top.
    Owen S.
    Production Engineer
    HWM-Water Ltd
  • david_van_der_meerdavid_van_der_meer Member Posts: 13 ✭✭
    Here is my attempt, but by trying to solve it with the assumption that the base could be non-square, and the peak not in the center of the base resulting in 4 uneven sides.

    https://cad.onshape.com/documents/b7a03380e6f81f03d5b40de7/w/f903f740ae0c0d2cfe4bd59d/e/2f7f4a6b2c1d13870b134f30

    It's not 100% stable, and partially fails when you change from a 10x8in base to 8x10in base for example, because the internal face of the triangle changes from having 3 vertices to 4 and vice versa, which doesn't work well with the projected sketch on that face used for the loft.
    It also leads to a slight interference at the peak when forcing the 4-vertices internal triangles to be a 3-vertices triangle instead, for lofting between internal and external triangle. (love the new interference analysis!)

    I think @NeilCooke 's method is very elegant, but relies on the design having rotational symmetry. Is there a way to achieve the above non-symmetrical pyramid in a way that would be 100% correct and robust but still manageable in terms of complexity? I made an attempt trying to slice all sides using planes on a shelled pyramid, and while it might have been possible, it would have become quite unwieldy by the end of it.

    Mind you I don't have a need for such a pyramid, it's more the technical challenge that interests me :smile:
  • HouseOfBreadCrumbsHouseOfBreadCrumbs Member Posts: 13
    @NeilCooke
    Okay, yours does seem like the best solution, though surprisingly more complex than I would've thought it should be! As always, I appreciate the help. :)
  • larry_haweslarry_hawes Member Posts: 429 PRO
    edited November 2
    Here's what might be a little simpler method using line angle to vertex planes and simple sketches on same. Height and peak location determined by plane vertex.

    https://cad.onshape.com/documents/b2c81db1fe30af018349a03c/w/5ccf5b61326982faea5c5d97/e/4c0626e0505912de7da21d4d

    I know these threads tend to die a quick death but am curious about the model posted above. It seems like a simple pyramid template changeable in most all of its aspects. The rectangle base can be altered as well as the height of the peak's plane and location of the top point/vertex. Curious about what might be missing?
  • larry_haweslarry_hawes Member Posts: 429 PRO
    I know it's hard to resurrect these threads but is there a reason that the method shown in the PYRAMID PLANES part studio would not be acceptable? Are there pimples in the method that I can't see?

    Thanks in advance

    https://cad.onshape.com/documents/b2c81db1fe30af018349a03c/w/5ccf5b61326982faea5c5d97/e/4c0626e0505912de7da21d4d
  • larry_haweslarry_hawes Member Posts: 429 PRO
    Just ain't gonna happen is it...
  • bruce_williamsbruce_williams Member, Developers Posts: 377 PRO
    @larry_hawes

    just to give my 2 cents - I think the OP is looking for parts for each side.  On yours the parts overlap.  I suppose you could skip the Offset surface features and do some trimming of parts to each other. I think Neil's solution has fewer features (although it is more advanced use of the tools).
  • larry_haweslarry_hawes Member Posts: 429 PRO
    Thanks for taking the time Bruce and yes even though the resulting surfaces create a pretty clean model any part creation, either by thickening or original parts on planes does create some not so great overlaps. I studied Neil's solution advanced as most likely is and barely followed what I would have thought to have a been a pretty easy exercise which was the reason for my attempt. Thank you again as I know how hard it seems to be to revisit some threads...
  • HouseOfBreadCrumbsHouseOfBreadCrumbs Member Posts: 13
    Yeah I do think that making a pyramid should be a simpler feature. Although some of the offered solutions work I just ended up lofting a rectangle and shelling the bottom. For my purposes all I needed to do was measure the length of each face so I know how big to cut it.
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