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How to concave a flat surface?

tj_thornileytj_thorniley Member Posts: 32
edited November 9 in Community Support
I'm trying to create a model of a microscope objective lens assembly. This is the first element in the series. It's a bit of an unusual shape, but essentially it's a cylinder with a 45° bevelled edge (the chamfer tool worked really nice, by the way). 

It's basically done, but I need to make a shallow indent/depression (concave) in the highlighted surfaces. Kind of like the inverse of a dome, hemisphere, dimple, or parabolic dish (imagine scooping it out with a spoon). If I could invert the chamfer tool (and round off the hard inside edge/corner so that it's a smooth arc/curve - like in the diagrams below) that would be perfect. 

Answers

  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 1,047
    Please take a look at the revolve feature. You could do that part all in one sketch/revolve. 
    Neil Cooke, Director of Technical Marketing, Onshape Inc.
  • tj_thornileytj_thorniley Member Posts: 32
    Okay, sweet. I've been trying with the revolve tool tool but can't seem to get it to co-operate. Would you mind going into more detail? What's the correct procedure? I just need to push it in about a millimetre or two at the deepest point. Thanks in advance, much appreciated.
  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 1,047
    You need to draw only half a section something like this (badly drawn, I know):


    Neil Cooke, Director of Technical Marketing, Onshape Inc.
  • tj_thornileytj_thorniley Member Posts: 32
    So, it's kind of like using the symmetry tool, but you end up with a 3D cylindrical / spherical object? Surely there's a way to modify the solid I already have? I suppose I could try to split the current model in half and use the 3-point arc tool (and trim) to carve out the concave.

    But for more complicated models that's going to be a major hassle. Rather than drawing the whole thing in a single sketch, I usually start with a basic sketch of a single shape, extrude, then sketch from a surface of the new solid, then extrude, and so on.
  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
    Revolve is the best way for this shape.

    But if you really like to trim away at a solid you can use boolean operations and making your cuts that way
  • owen_sparksowen_sparks Member, Developers, Configurations EVP Posts: 925 PRO
    edited November 10
    Yes as the chaps mentioned
    Option 1 Revolve remove the bits you want to cut away from your existing part.
    Option 2 New Revolve to create whole part in one go. Note:- Easier than option 1 :wink:

    You can even use the equations you've posted above to drive the sketch for the revolve if you wish.

    Owen S.
    Production Engineer
    HWM-Water Ltd
  • tj_thornileytj_thorniley Member Posts: 32
    edited November 14
    Here, I got it to work using revolve, from scratch.


    Then bevelled the edge with the chamfer tool.



    Changed the material to glass, edited the appearance to a translucent blue, and hid the intersecting planes.


    But I still haven't managed to scoop the concave out of an existing object. This shape is relatively simple, but I anticipate having to do this kind of operation on more complex solids in the future. Having to redraw a completed part from scratch every time I want to make a minor adjustment is very quickly going to become a major headache. Especially if the dimensions are already specified. 

    I've tried to be detailed and include diagrams depicting every step of the procedure (not unlike a tutorial). If someone could do the same for me, I would really appreciate it. Thanks in advance.
  • owen_sparksowen_sparks Member, Developers, Configurations EVP Posts: 925 PRO
    edited November 14
    Howdy.

    Removing from an existing part is exactly the same but instead of selecting the "new" option on the revolve you select "remove" and then which part you want to remove it from. Termed the merge scope, shown below.



    The highlighted area is the new sketch used to make the cut away.  (The actual grey part was created earlier from an extrude of a circle.)

    Note shown with cross section turned on as it shows the concave nature better, the part is of course whole with that view turned off.



    File here:-
    https://cad.onshape.com/documents/b6a887c3cdcfbf681b9c9373/w/f16831af92b9443420026b87/e/2b158c9b00f1666108d2bff7

    Owen S


    Production Engineer
    HWM-Water Ltd
  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
    edited November 14
  • owen_sparksowen_sparks Member, Developers, Configurations EVP Posts: 925 PRO
    edited November 14
    Too slow, chicken marango o:)

    Owen S.
    Production Engineer
    HWM-Water Ltd
  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
     :'( 
  • owen_sparksowen_sparks Member, Developers, Configurations EVP Posts: 925 PRO
    Have an up-vote anyway :p
    Production Engineer
    HWM-Water Ltd
  • tj_thornileytj_thorniley Member Posts: 32
    Thanks for the quick replies fellas. I did try something like that, but to no avail. I'll try it again in a bit, with your examples to guide me. Hopefully this helps someone else too. By the way, how did you do the cross section view? That could be useful.
  • john_mcclaryjohn_mcclary Member, Developers Posts: 439 PRO
    There is a lot of neat things you can do with section view, but this is the basic start:

    For more info you should check out the OnShape youtube channel. All kinds of stuff to look at there, including a complete run down of this

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