model pneumatic cylinder plus lever movement

[rhelber]

Is there a video or tutorial on how to model the movement of a Bimba pneumatic cylinder connected to a lever arm using the educational version of PTC Creo parametric?

If not, how should I get started on modeling movement of connected parts?

[sm · Accepted solution]

Robert,

Attached is an old concept model I worked on with FRC 2876 - Devilbotz for the LogoMotion game. We never did build this, but it would have been pretty cool. I'm assuming you can open the model the investigate the assembly techniques used to create the pin joints and slider joints that make up the motion. Let me know if you have any specific questions after looking at the model.

Video Link : 6679

[rhelber]

Thanks!  This example has been a big help.  I opened up the file and was able to figure out how to model our pnumatics.

[rhelber]

I have a question.  I have made a nice pneumatic cylinder attached to a lever.  When I put this assembly on the robot assembly and try to drag the lever, the whole robot moves.  I've tried to constrain the robot to datum planes but it still moves. How can I hold the robot still so that I can see the lever/cylinder action?

[sm]

If one or more of your assembly components are not constrained, this is what will happen. All of you non-moving components need to be "grounded" with proper assembly constraints. Look for a small box in front of the component name to identify "packaged" components. You can also display the Feature Attributes column in the model tree and look for "Packaged" components.

In this video, the first instance of the drive module is not constrained. The second instance is connected with a slider mechanism. When the model is dragged, both parts move around on the screen. After assigning the first component the "Default" constraint to ground it, the slider works as expected.

Video Link : 6681

[rhelber]

Hi, Thanks again for the help.  I have another question.

When I download bimba cylinders the creo 2.0 cad files don't have constraints at all.  All the parts are fixed.

Direct insert does not work on my laptop for some reason.

So, I have been applying constraints to the cylinders, but it is tedious.  Is there an easier way?  Does direct insert have constraints?

Thanks.

[sm]

Unfortunately, the BIMBA site is creating all the various CAD formats from a neutral file (STEP) which does not contain any constraints. You will get the proper geometry and structure for the CAD, but you will have to re-engineer the constraints since they are not retained in the neutral file.

[rhelber]

Okay, that is fine.  I think I made a discovery.  If I group parts of the cylinder into a sub-assembly, then I can make the sub-assembly behave like one part, which makes the constraints more simple, rather than constraining every part in the sub-assembly. Does that make sense?  Thanks.

[sm]

Yes, you can Restructure the components into a more appropriate group of components before adding any constraints since the neutral file does not have constraints. As you mentioned, once you have them organized into the proper sub-assemblies, you can apply the required constraints and connections.