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Pierce constraint part way through a loft

brett_suttonbrett_sutton Member Posts: 42 ✭✭✭
I have a simple loft between two planes and I now need to attached a construct to the bottom of the loft part way between the two planes.

The loft is forming the roof of a bell housing for my cat door bell.

I've created a third plane (referred to as 'bell holder') and created a sketch of the construct which will become the bell holder.

The problem is that I can't see anyway of attaching the sketched bell holder to the loft that forms the roof of the bell housing.

I thought the pierce constraint would allow me to constrain a point on the bell housing sketch to the loft that forms the roof where it intersects the bell holder  plane, but no luck with that.

I've hacked around the problem by visually aligning the holder to the roof (loft) of the bell housing. But this just seems wrong.

I thought it worth posting the questions as others may also find the correct answer useful.

You can set a point in time version with a sectional view through the 'bell holder' plane. 


Thanks in advance,

And yes, I'm making a cat bell for my front door, as I'm sick of the cat scraping the paint off the front door when it wants in.
Some pavloving training will ensue.

And no its not my cat, its the wife's. If it was my cat, I would be making an entirely different type of contraption :)


  • andrew_troupandrew_troup Member, Mentor Posts: 1,584 ✭✭✭✭✭
    You can only create a pierce constraint to a line or edge, not to a face
    (this is because the remote entity in a pierce constraint has to pierce the sketch plane at a single point in order to be solved)

    Other MCAD packages have the ability to create an intersection curve, but that is not yet available in Onshape

    What you could do is first to relocate your part so the Right plane is the midplane (you're making things hard by offsetting the model)

    Then roll the model back to just below your loft profile sketches, and create a sketch on the Right (mid)plane, whose endpoints have a pierce relation with the inner curve of the respective loft profiles. This is effectively a retrospective guide curve.

    Now you can create a pierce relation to that 'guide curve' in your sketch 3.
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