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Onshape Instructor Kit - 1.2.1 - Basic Sketching, answer off by 0.001

I have attached the sketch and the mass properties as images.  I am perplexed how the answer is so close, only off by one thousandth.  I believe I have all of the tangents, but I must have missed something.  Can anyone spot what I may be missing?


  • mthiesmeyermthiesmeyer Onshape Employees Posts: 37
    Hi James,

    I have attached an image that is fully constrained. Does the fix make sense? (the value of the dimension I added is probably wrong for your purposes)


  • NeilCookeNeilCooke Moderator, Onshape Employees Posts: 1,451
    I think you're supposed to add a tangency constraint between these two:

    Neil Cooke, Director of Technical Marketing, Onshape Inc.
  • ilya_baranilya_baran Onshape Employees, Developers Posts: 794
    The blue color of the lines/arcs/points indicates that they are not fully constrained.
    Ilya Baran \ Director of FeatureScript \ Onshape Inc
  • james_hawkins111james_hawkins111 Member Posts: 2
    I applied the dimension suggested by MichaelThiesmeyer, and I (separately) added the tangency constraint suggested by NeilCooke, and in both cases the model became fully constrained; however, the final volume still only calculated as 0.701.

    Here is a link to the document in case this helps at all:

  • brian_bradybrian_brady Member, Developers Posts: 245 EDU
    edited October 2017
    I found it. Your angled lines that contact the upper and lower Ø0.75 circles need to be tangent to those two circles. The end points of your lines are horizontally aligned to the centers of the circles, which are not the tangency points. Same issue with the two angled lines that should be tangent to the Ø0.625 circle.
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