CENTRE OF GRAVITY COMPUTATIONS IN PRO-E?

[ferc]

Hi!
Can anyone help me explaining how to determine the centre of gravity in PRO-E for any part

[PTC_FRC]

Hello,

This can easily be done in Pro/E. Please see the attached document that explains the process.

Good luck.

mark

[ferc]

Thanks a ton, for ur help
I still need to figure out how to do impact analysis on the structures of robot using
Mechanica

[PTC_FRC]

Glad to help.

As for using Pro/E Mechanica to analyze structure, there are plenty of tutorials available.

You might want to check out the one from Carnegie Mellon - http://www.me.cmu.edu/academics/cour.../tutorials.htm

Look at the bottom of the page.

Mark

[ferc]

Thanks for your help.
Can we replicate a single step and apply the same to other process?
For Example: Adding nut to the bolt in one step and copying the steps or manipulating them to add bolts to other nuts?

[Greg Needel]

Originally Posted by ferc

Thanks for your help.
Can we replicate a single step and apply the same to other process?
For Example: Adding nut to the bolt in one step and copying the steps or manipulating them to add bolts to other nuts?

I am not familiar with this, I would recommend making sub-assemblies and then using those to speed up the process.

[ferc]

It's a time saving technique than assembling parts individually

[Tristan Lall]

Originally Posted by ferc

Thanks for your help.
Can we replicate a single step and apply the same to other process?
For Example: Adding nut to the bolt in one step and copying the steps or manipulating them to add bolts to other nuts?

There is a method for that, when assembling components.

You first constrain the first instance of the components as normal. Then you select a component to duplicate and go to Edit | Repeat. That brings up a dialog box where you pick which constraints you'd like to not reuse when placing the duplicates. (If you leave constraints deselected, it reuses the constraint from the first component; if you select them, you can click on an alternative object of the same type to constrain it to that.)

Once you've picked the constraints to vary, then you click Add, and click on the new references, in order. Repeat this order for as many components as you want to add.

This is actually one of the biggest time-savers, when dealing with lots of similar constraints.

Another option is to use reference patterns. If you pattern the holes that a bolt goes into, then you can pattern the fasteners that go in it. The best way to do this is to create one initial hole feature. Then constrain a bolt in the hole by inserting it (and adding whatever other constraints you need). Then constrain a nut—but I believe you've got to reference the hole somehow, so use the insert constraint on the hole.

Pattern the hole, with whatever options you want. Then, when patterning the nut and bolt, the option of "Reference" will be available. Use that, and it will refer automatically to the existing hole pattern, and make dependent copies.

[ferc]

thanks for your timely help!

[OrthoDan]

Pro-Mechanica is limited to static analysis, so whatever you might learn about impact in a simulation will be an approximation. The CMU tutorial posted by PTC_FRC has a nice example of building a beam-type finite element model that would be a reasonable approach for welded aluminum frames, which many FRC teams use. You need to be sure to place nodal points (at the ends of beam elements) at locations where you either want to constrain the structure or apply a load. For impact protection, avoid long unsupported spans of thin walled aluminum tubing. Cross-bracing will help avoid impact related permanent bending of your frame.

[Tristan Lall]

Originally Posted by OrthoDan

Pro-Mechanica is limited to static analysis, so whatever you might learn about impact in a simulation will be an approximation. The CMU tutorial posted by PTC_FRC has a nice example of building a beam-type finite element model that would be a reasonable approach for welded aluminum frames, which many FRC teams use. You need to be sure to place nodal points (at the ends of beam elements) at locations where you either want to constrain the structure or apply a load. For impact protection, avoid long unsupported spans of thin walled aluminum tubing. Cross-bracing will help avoid impact related permanent bending of your frame.

To expand a little on Dan's comments, one of the biggest problems with using FEA software isn't the software itself, but rather the user...it's very easy to get results that look convincing, but which are actually quite false. Sanity-check your results with simplified test cases, and seek out assistance if necessary, in order to set up the simulation correctly.

[tech snob] I'd be impressed if you could calculate the True center of gravity.... Center of Mass, on the other hand, is much easier! [/tech snob]