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R
ropitz10-Marble
10-Marble
March 7, 2016
Solved

Slide A Piston With Mechanism Constraints

  • March 7, 2016
  • 3 replies
  • 7942 views

Hello Creo Users,

 

I have a very simple (?) mechanism problem that I can't solve. Two quilts created by extruded spline curves should slide at each other. It is a planar situation because the piston only moves in the xy plane. The left end of the piston always moves only horizontally. If I create cylindrical quilts to use it works with the constraint "Tangent" but it doesn't with non-cylindrical surfaces.

I am getting forward to get some advices how to assemble the piston and how to add Mechanism constraints to make the Mechanism analysis run without failure message. See the situation described in the attached pdf document.

 

Thanks a lot, Ruediger


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Best answer by TomD.inPDX

Ah, yes, perfect.  Never really thought about using a cam this way in Creo.  This could solve a lot of complex contact problems.

...save-as .zip also backs up everything in the open assembly.

3 replies

T
TomD.inPDX17-Peridot
17-Peridot
March 7, 2016

A normal piston constraint is a simple pin constraint on the connecting rod ends and a cylinder constraint on the piston.

The piston relies on an axis and typically doesn't have the degree of freedom within the cylinder.

You might be able to use a CAM.  And if nothing else, a slot connection.  Somewhere you need collision detection but you have a condition where the solutions are literally infinite as you show it in the PDF.

If you have the kinetic extension, you could use gravity to undulate the piston.  You could arbitrarily move the housing to change the angle of the piston in relation to the housing.

R
ropitz10-MarbleAuthor
10-Marble
March 8, 2016

Hello Dirriwachter,

I am not sure, if you understood the situation right. It is not a normal piston connection. To  make clear what I mean I added a video from another example (the end is quite funny and happened accidentally)

Video Link : 6743 .

This is what I like to do. I defined it by a Cam Follower. Another question: is it possible to upload simple Creo data assemblies for other user to investigate better what is meant?

Thank you again,

Ruediger

K
Kevin1-Visitor
1-Visitor
March 8, 2016

Since what is in contact changes you will probably need to use the cam constraint in Mechanism. I don't believe there is an assembly constraint set that is used for what you are wanting to do. For the cam constraint you select surface regions that remain in contact as the mechanism is articulated.

R
ropitz10-MarbleAuthor
10-Marble
March 9, 2016

So it will be easier to understand the situation having the right data. If there is anybody following this issue I will look forward to get any response that helps to get this really easy mechanism run. Attached you find a simplified assembly with two parts that represent my problem quite well.

Thank you for answers

K
Kevin1-Visitor
1-Visitor
March 9, 2016

Updated Mechanism.

    T
    TomD.inPDX17-Peridot
    17-Peridot
    March 9, 2016

    There are no parts in the file, just the assembly.

    Try using the save>backup to a folder and zip the files.

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