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Slide A Piston With Mechanism Constraints

ropitz
3-Visitor

Slide A Piston With Mechanism Constraints

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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1 ACCEPTED SOLUTION

Accepted Solutions
TomD.inPDX
17-Peridot
(To:Kevin)

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.

View solution in original post

17 REPLIES 17
TomD.inPDX
17-Peridot
(To:ropitz)

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.

ropitz
3-Visitor
(To:ropitz)

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

Kevin
10-Marble
(To:ropitz)

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.

TomD.inPDX
17-Peridot
(To:ropitz)

If you go to the advanced tab when editing, you can attach files.

ropitz
3-Visitor
(To:ropitz)

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

Kevin
10-Marble
(To:ropitz)

Updated Mechanism.

TomD.inPDX
17-Peridot
(To:Kevin)

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

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

‌They're there I just didn't notice how they were named.  I'll try posting again. They actually open for me with no modifying of the name.

TomD.inPDX
17-Peridot
(To:Kevin)

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.

View solution in original post

Hi Antonius,

thank you for being that busy on my problems 🙂 !

TomD.inPDX
17-Peridot
(To:ropitz)

That was Kevin's file.  I just repacked it so it would open.

Did Kevin's solution work for you?

Hi Antonlus,

I didn't get a solution from Kevin yet. And my time is running out. So I would wait and not focuse on that issue any longer now.

Have a nice weekend,

Ruediger

Kevin
10-Marble
(To:ropitz)

That was the solution I posted. As Antonius stated he renamed the files so they would open. I didn't re-post the files since he had already done so.

ropitz
3-Visitor
(To:Kevin)

Hi Antonius, hi Kevin,

thank you for your quite pretty working solution. That ist, what I was searching for. But, I must admit, I don't really understand why I need another part in the assembly just to slide the axis of the last part the way it should run. I will spend some more time on it to 'translate' this now to my origin assembly with other parts.

Again, thank you a lot!

Regards, Rudi

ropitz
3-Visitor
(To:Kevin)

Hi Guys,

now there is the next problem. How to define the servomotor for a translation constraint to get the analysis run? I am still trying a lot of ways but get always the message that the constraints are not valid. So I don't get the analysis run... It would be very nice if you may try this out and upload again a working assembly.

Many thanks, Rudi

TomD.inPDX
17-Peridot
(To:ropitz)

Simple, if you had the dynamic motion package, you could make a slot motor.  But with core Creo Mechanism, all you get is servo motors.  Therefore you need to link a rotating object to a sliding object in a gear connection. 

Hi Antonius,

I tried a while but with a servomotor it works. This is exactly what I need. See attached movie.

Thank you again for your helpful advice!! Great!

Video Link : 6764

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