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Another design contest

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Answers

  • MBartlett21MBartlett21 EDU Member Posts: 1,640 EDU
    It's because they are wizards Larry!

    It's amazing some of the black magic I've seen people do in onshape.
    Too true, too true. It also seems that some of that black magic is exactly that and hidden within the interface from the every day user but I learn something new with each one of theses 'contests'.
    @larry_hawes

     Do you mean like how my opBoolean feature ( https://cad.onshape.com/documents/84d939daceef6a928b8abcba ) makes use of hidden interface options, such as sllowSheets and eraseImprintedEdges, that the normal Boolean feature does not use?
    MB - I make FeatureScripts: view FS (My FS's have "Official" beside them)
  • vytautas_paltanavičiusvytautas_paltanavičius Member Posts: 1
    edited June 2018
    So far I have managed to achieve this. Still feels like way too much.

  • john_hackingtonjohn_hackington ✭✭ Member Posts: 43 ✭✭
    edited June 2018
    Hi all,

    This is a very informative exercise, and I've learnt a lot from following all of your examples.

    Just like to add my 2 cents here, which I believe many here could already be aware of, but it would be helpful for others reading this thread to follow along.

    The main issue facing all the models so far would be this particular dimension requirement:

     

    Which is that the minimum distance from each slot to the top slanted plane has to be a defined value of 'A'.


    Firstly, for @NeilCooke 's model at:
    https://cad.onshape.com/documents/132908f652f6ebeb86dccf55/w/657ad40db02fcf3f72bd345d/e/6af53f5236d0b8bb579f5bc0

    To meet the aforementioned requirement, a plane was implemented with an offset of 'A' from the top slanted plane:



    In such a case, the direction of the offset is actually normal to the top slanted plane. As a result, this will only give the correct 'A' distance for the slot that is situated under the middle of the slant.

    For the slots situated under the top and bottom of the slant, the minimum distance is actually measured in the vertical direction, and not in the direction normal to the plane.

    Thus, considering the 15 deg angle slant applied, the minimum distance for the slots under the top and bottom of the slant would turn out to be [10 / cos(15)] = 10.353.




    On the other hand, for @emagdalenaC2C 's Part Studio 4 model at:
    https://cad.onshape.com/documents/98c43f730cc7deb2d25486e7/w/988e18dbc7c3f809e9da275c/e/b9028454f0634d679840eab5

    An offset of 'A' was also made from the slanted top plane, but this time the offset direction is simply vertical, instead of normal to the plane:



    As a result, the minimum distance will be precisely 'A' for the slots located at under the very top and bottom of the slant.

    However, for the other slots in between, that are located under the slope of the slant, the minimum distance value would not be correct.



    Referring to the picture above, whereas the goal should be to set d to the value of 'A', the above operation set d' to the value of 'A' instead. Therefore, the minimum distance measured for the other slots will always be smaller than the desired value of 'A'.

    To delve a bit more into this problem, we could imagine opening this slanted top cylinder up, and taking a look at the top part of this flattened cylinder.



    The directions in which the minimum distances would be measured for any given point on the top rim would be perpendicular to the rim. The difficulty in setting the correct 'A' dimension lies in how the directions are changing according to the curve of the rim.

    So far @emagdalenaC2C managed to make the model manually in his Part Studio 5, but the number of slots could not be varied.

    An idea that could potentially work was brought forth by @brucebartlett at:
    https://cad.onshape.com/documents/c4ba2cbb65d395eeb3d2009f/w/e7c87743cb563ced4c73b0e5/e/5f281deafc8d6fbf12fc26f6
    in which the slots will first originate from a sketch, where the minimum distance between the semi circle and the top plane could be set and then regenerated in the Circular Pattern by using 'Apply per instance'. However, @lana clarified that constraints to out-of-sketch geometry are ignored, so reference to the top plane could not be regenerated, and that route leads to a dead end too.

    This should be the rough breakdown on the issues that we are facing in dealing with this particular problem. Wonder is there a way to tackle this design problem?
  • emagdalenaC2iemagdalenaC2i ✭✭✭✭✭ Member, Developers Posts: 567 ✭✭✭✭✭
    Great description @john_hackington

    So, You Wonder if there is a way to tackle this design problem?

    Well, maybe if we have the option in Onshape to extrude to a surface (or plane) with an offset parallel to the extrude direction...

    Take a look to this post EXTRUDE UP TO FACE WITH THE OFFSET OPTION SHOULD TRANSLATE THE FACE OR USE AN OFFSET SURFACE
    Un saludo,

    Eduardo Magdalena                           C2i Change 2 improve                           ☑ ¿Por qué no organizamos una reunión online?   
                                                                 Consulting Partner de Onshape                                      Averigua a quién conocemos en común

    Consulta mis cursos de Onshape en Español:
  • owen_sparksowen_sparks PRO Member, Developers Posts: 2,418 PRO
    So this whole contest was an elaborate ploy to get your IR up-voted?  :) :) :) :) :)

    Well played!

    Owen S.
    Production Engineer
    HWM-Water Ltd
  • emagdalenaC2iemagdalenaC2i ✭✭✭✭✭ Member, Developers Posts: 567 ✭✭✭✭✭
    Of course, What do you think it was about?  >:)
    Un saludo,

    Eduardo Magdalena                           C2i Change 2 improve                           ☑ ¿Por qué no organizamos una reunión online?   
                                                                 Consulting Partner de Onshape                                      Averigua a quién conocemos en común

    Consulta mis cursos de Onshape en Español:
  • john_hackingtonjohn_hackington ✭✭ Member Posts: 43 ✭✭
    That's a very interesting point on True offset and Translational offset that you've brought up @emagdalenaC2C !

    However, True offset and Translational offset seem to only have a geometrical difference when the reference (line or surface) is curved.

    So far in the attempts tackling this case, all the offsets are done with respect to straight geometries (straight line, flat plane), so the option of a True offset still might not solve the underlying issue.
  • MBartlett21MBartlett21 EDU Member Posts: 1,640 EDU
    However, True offset and Translational offset seem to only have a geometrical difference when the reference (line or surface) is curved.
    Not quite, that was why one of the models used a pplane as "Up to", rather than offset from the top face
    MB - I make FeatureScripts: view FS (My FS's have "Official" beside them)
  • john_hackingtonjohn_hackington ✭✭ Member Posts: 43 ✭✭
    edited June 2018
    Hi @mbartlett21 !

    If I've understood correctly, you're referring to @NeilCooke 's model. The plane used for "Up to" itself is offset from the top face, so there shouldn't be a geometrical difference from a direct offset from the top face, as the surface is flat.

    The actual offset distance will be different, but it can be compensated by adjusting for the angle between direction of the normal to the plane and the vertical direction. 

    I'm not sure about the accuracy issue that Neil was referring to, but he is not sure about it too and attributed it to something about the surface boundary. So technically, that has nothing to do with the difference between a True offset and a Translational offset.

    On a quick side note, when "Up to" is used, it's like a Translational offset to 0 mm. When the offset is 0 mm, there indeed is no difference between a True offset and a Translational offset even if the geometry is curved.

    Also just like to lay out my understanding of Translational offset and True offset here, as described in @emagdalenaC2C 's post:

    A Translational offset happens when the offset distance to the reference line/surface is measured in a single direction (which is the direction of the extrude). A True offset happens when the offset distance is measured in directions normal to the reference line/surface.

    For example, if we would set an offset distance of d,

    Translational offset for a curve and for a straight line would look like this:

              

    In the vertical direction, the distance between the reference and product will be d.


    True offset for a curve and for a straight line would look like this:

              

    In the vertical direction, the distance between the reference and the product may no longer be d.

    Looking at the straight line examples above, although the vertical distance is different, geometrically, both the products are still straight lines. This is because at all points through the line, both the vertical and normal directions to the reference are constant.

    The difference between a Translational offset and True offset in this case can thus be easily compensated by taking into account the angle between the normal and vertical direction.

    This is not the case for the curve, as at different points on it, the normal direction to the reference is changing. At some point the vertical distance might be a' while at another it might be b'. The radius of the product by True offset is different.

    This is what I meant by Translational offset and True offset only having a geometrical difference when the reference is curved, but there's no geometrical difference when the reference is straight.
  • MBartlett21MBartlett21 EDU Member Posts: 1,640 EDU
    @john_hackington

    OK, i get it now :smile:
    MB - I make FeatureScripts: view FS (My FS's have "Official" beside them)
  • MBartlett21MBartlett21 EDU Member Posts: 1,640 EDU
    Accepted Answer
    MB - I make FeatureScripts: view FS (My FS's have "Official" beside them)
  • emagdalenaC2iemagdalenaC2i ✭✭✭✭✭ Member, Developers Posts: 567 ✭✭✭✭✭
    Nice  :D
    Un saludo,

    Eduardo Magdalena                           C2i Change 2 improve                           ☑ ¿Por qué no organizamos una reunión online?   
                                                                 Consulting Partner de Onshape                                      Averigua a quién conocemos en común

    Consulta mis cursos de Onshape en Español:
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