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Trying to mate two parts at a specified angle in an assembly. See the chain, long pin and short pin

Trying to mate the faces of two parts at a specified angle in an assembly. See the chain, long pin and short pin assembly attached. 

Best Answer

  • billy2billy2 Member, OS Professional, Mentor, Developers, User Group Leader Posts: 1,779 PRO
    edited February 2021 Answer ✓
    This is a classic reverse dependency problem. Onshape can compute A, B & C for you.

    Typically, you'll know where the green shafts are located and want to know A, B & C angles to make this happen. Changing the location of either green shaft will update A, B & C. This is the basis of any robotics or automation exercise. Don't try to go from one green shaft to the other green shaft by typing in angles, instead, determine where the shafts are located and have onshape compute the angles.

    I'd group green to yellow and cyan to yellow to simplify the solution. In the end I'd have 3 movable links and 1 fixed link.

    To achieve what you want, I'd create 3 fixed mates and change the angle between the links. You'll have to edit the mate connectors to change the angle and not the mate. This is confusing the fact that you have mates & mate connectors and I've created an enhancement request to clean this up. While editing the mate, you can't change the mate connector. You have to exit the mate to edit the mate connector. This has been cleaned up in other areas of the program, but here, in an assembly, it's clunky. 

    What interests me, create 3 revolute mates and control where the green shafts are located. Then ask onshape for the angles that make this true. If it's not possible, then it'll error out. This gives you the ability to position a robots end effector in your assembly and ask for the angles to make this true.

    The base angle is 56.939° to make this true



Answers

  • billy2billy2 Member, OS Professional, Mentor, Developers, User Group Leader Posts: 1,779 PRO
    edited February 2021 Answer ✓
    This is a classic reverse dependency problem. Onshape can compute A, B & C for you.

    Typically, you'll know where the green shafts are located and want to know A, B & C angles to make this happen. Changing the location of either green shaft will update A, B & C. This is the basis of any robotics or automation exercise. Don't try to go from one green shaft to the other green shaft by typing in angles, instead, determine where the shafts are located and have onshape compute the angles.

    I'd group green to yellow and cyan to yellow to simplify the solution. In the end I'd have 3 movable links and 1 fixed link.

    To achieve what you want, I'd create 3 fixed mates and change the angle between the links. You'll have to edit the mate connectors to change the angle and not the mate. This is confusing the fact that you have mates & mate connectors and I've created an enhancement request to clean this up. While editing the mate, you can't change the mate connector. You have to exit the mate to edit the mate connector. This has been cleaned up in other areas of the program, but here, in an assembly, it's clunky. 

    What interests me, create 3 revolute mates and control where the green shafts are located. Then ask onshape for the angles that make this true. If it's not possible, then it'll error out. This gives you the ability to position a robots end effector in your assembly and ask for the angles to make this true.

    The base angle is 56.939° to make this true



  • Ralph_HamiltonRalph_Hamilton Member Posts: 9 EDU
    Thanks Billy2.   That was helpful.  As a high school teacher that started with SolidWorks, I wish OnShape made setting angles easier.  Maybe that is something that they could work on.  An "Angle Mate" would be awesome!  It appears that it might be easier to set the angle between two flat surfaces than it is with tubes/cylinders.  I have a student that made it work.  We're going to look at it more.  Thanks for your time and interest. 
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