Need help creating a flexible cylinder (rubber boot) in an assembly.

[erazorzedge]

Hi, I've been working with Inventor (2014) for a few months and trying to learn as much as I can on my own. Usually what I do is download a 3D CAD part from McMaster Carr or some other place and start from scratch trying to recreate the part or, in this case, the assembly. I'm working on modeling a simple swing-arm type of machine I've made in the past and the I've been able to recreate all of the parts with their proper ranges of motion except one. It's an Inline Ball Joint Linkage that has a rubber boot around it to keep the dust out and possibly grease in. I want to know if it is possible to model the rubber boot so that it would mimic real life movement. Right now, the boot is basically a rigid cylinder and as the linkage swivels, the solid bodies clip through each other. Can this be done? And if so, how?

I've been able to make a flexible hose type of assembly as shown here: https://grabcad.com/library/tutorial-how-to-make-flexible-hose-wire-by-autodesk-inventor. However, creating a 3D drawing with a spline that attaches to work points on the other assemblies causes the Ball Joint to no longer work. It will only rotate as opposed to swiveling.

Please see the attached file.

[PaulMunford]

The short answer is no.

Inventor isn't very good at this kind of flexible assembly. You may have to work around it.

You can either use adaptivity to create a relationship between the parts, or model the whole thing with multibodies.

Neither will be perfectly satisfactory 😞

Let us know how you get on.

[blair]

A while back, someone posted a flexible bellows (air-bag) in an assembly that worked well, but as posted this requires adaptivity between parts. You might have to either search this forum or possibly Youtube.com

[blair]

try this: http://forums.autodesk.com/t5/Inventor-General/Creating-an-Air-Bag-suspension/m-p/3785834/highlight/...

[Curtis_Waguespack]

Hi erazorzedge,

Here is a link that might be of use:

http://inthemachine-autodesk.typepad.com/blog/2006/11/make-it-adaptive.html

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[erazorzedge]

Thanks for the links. I've been able to make flexible parts such as the one Curtis linked to, but I believe they only work (without driving a constraint) because of their linear movement. The green air bag one is pretty trick, I'll have to try and recreate that.

Playing with my assembly a little more, I was able to make it work, but not exactly like I wanted. I followed the guide that I posted above by setting up Work Points along the Y axes of two parts and then created another part in the assembly with a 3D Sketch that contains Lines and a Spline that attached to the Work Points from the other parts. Then I Swept a Cylinder (based off of the geometry of the other parts) along the 3D Sketch path. After that, I had to add a couple more constraints; a Flush constraint to the XY planes and an Angle constraint to the YZ planes of the ball and socket parts. From here, I can drive the Angle constraint, but it only updates the Flexible Boot model if I check the Drive Adaptivity box. And of course, as the angle gets further from zero, the model disappears entirely. I'm assuming that's because Inventor can no longer properly sweep the cylinder along the 3D path.

So in short, I can get it to work, but only if I have Inventor drive it; no manual movement. And it's limited to 1 axis of rotation; not like a ball joint. Also, placing the assembly in a higher-level assembly, I have to delete the Flush and Angle constraints in order for it to properly move.

I've attached the updated assembly and below is a link to the Rendered Animation with the ball joint in an upper-level assembly to show the flexiblity.

https://www.youtube.com/watch?v=FKGB8o3zN0E&list=UUn_lK87Dru7FS4C-HCwPBZA