Ellipsis

The Basics of Skeletal Modeling

I received some great feedback from the YouTube video on Skeletal Modeling Made Easy with Autodesk Inventor. Some of the feedback was asking if I could step back a minute and start from scratch. I just finished up the two part video “The Basics of Skeletal Modeling in Autodesk Inventor”. This is a very basic example of the fundamental tools used for rules based design. A basic understanding of parameter sharing within an assembly is key to moving your design to something like rules based or configuration management.

Take a look, subscribe to the channel and start to think about how you might apply some of the techniques and hairstyles discussed in this two part video.

Part 1

Part 2

-Rob

My Introduction

Hello every one. Welcome to the newly refreshed blog “Ellipsis”. I’d like to take a moment to introduce myself. My name is Justin Hoey, I’m one of the new faces that will be posting to this blog. I work out of the Portland, Oregon Autodesk office as one of our Industry Solution Evangelist. I am one of the few in the Portland office that has been born and raised here in Oregon.

I like to spend my time tuning cars, 

Riding BMX,

Working in my yard

And spending time with the family.

So now that you know a little more about me, let’s get a little more serious. We have started filming for series of video that Interview Product Managers at Autodesk, about the 2010 launch. We also have a special surprise for the last interview. Enjoy!

Also you can follow me on twitter at http://twitter.com/EverydayTropic .

So... what now?

You've completed a single point stress analysis, discovered several areas of high stress in your assembly, but how best to deal with them?  There are a dizzying number of model parameters that could be changed, all of which will no doubt have an effect upon, but which one(s) would yield the best results?

Well, fortunately, Inventor Professional 2010's Stress Analysis environment has a tool to help you determine just that!  The technique is sometimes referred to as Parametric Optimization, but in the SA environment it is called Parametric Dimension.  Essentially, it allows you to select a group of sketch and model parameters that will be used to build part/assembly iterations, and each of these interations, and all of the resultant combinations, will be analyzed and then the results measured against a set of design constraints in a process that it sometimes referred to as a sensitivity study.

Stick with me here... in the example below, you see that after we run the single point analysis we find that we have several high stress areas.  These stresses, while not significant enough to exceed the yield strength of the material, are nonethless a concern because ultimately they could lead to fatigue failure of one of the parts in the assembly.  The highest stresses are concentrated in the tab, so we can try a few different thicknesses for the tab itself and also for it's stiffening rib.  Three different values for the tab, and two for the rib give us a combination of 6 different versions that will be analyzed.  To save time in processing there is an option for running what is called a "Smart set" of configurations.  If you arranged the versions in a table, you would see that we have 3 columns and 2 rows, or vice versa, of interations... 4 total with regard to the 1st column and 1st row, and a total of 6 different combinations.

In our case, the "Smart set" analyzes those 4 versions, and because we are performing linear analysis, is able to interpolate the results for the other two.  Once the analysis is complete, we open up the Parametric Table once again and are now able to evaluate our results against specific design criteria... in our case, Mass, Stress and Factor of Safety.  Once a version is found which meets our design requirements, we promote the parameter changes back to the model, whcih then changes all of the assoicated parts/assemblies/drawings. 

It is a very powerful addition to what was already a powerful analysis tool.  Check it out and let me know what you think.

 

Getting to Know Rob Cohee

Ah, the getting to know me blog. These have to be more painful to write than a resume or worse yet a bio. Why is it that we have such a hard time talking about ourselves? But somehow I can ramble on for hours about technology, industry trends, and military history – but ask me to talk about myself… hmmm. Maybe it would be cool to share stuff that there is no way you would know if I didn’t tell you.

For starters I’m originally from Omaha Nebraska. I might be the first person you have ever met from Nebraska so yes, there are people there and no I didn’t have to shoo cows out of my front yard in order to get to work. Nebraska is the home of the College World Series, Henry Doorly Zoo (a world class zoo btw), and the world famous Nebraska Cornhuskers. Yes, I’m a Cornhusker fan. During games I pace back and forth like a junkie needing a fix, scream at the TV or radio – picture Dennis Leary hunting for a cigarette – that’s me on College Football game day.

So what next - I’m married with three kids and we now live in the Manchester New Hampshire area. It’s been ok so far, we like being close to Boston, Skiing, and the coast. We’ll see how a summer goes before we decide how much we like it out here or not.

Ah, here’s one you would never know about me. Although my stout 5’9” 230 lb physique (I can’t write that without laughing btw..) doesn’t scream soccer player, I was a goalie for my high school soccer team where we won the state championship. I rode the pine for the entire game which combined with my current level of physical fitness makes the whole story all the more funny.

Ok, fine something work related. I started working with AutoCAD whilst studying Industrial Management at Peru State College in Peru, NE where I was attending on a Football scholarship. See, the physique now makes a little more sense… Anyway, you could call me the class of AutoCAD R10. It’s always funny that those of us that have used Autodesk products for any period of time identify ourselves as which version we stared working with. Those AutoCAD R2.3 guys are always looked at as the tenured faculty.

How did I get started with 3D modeling? Funny story - I designed safety equipment for Union Pacific Railroad for a while after school and started out using 3D so that I could get funding for a project that I was working on. I needed $150,000 to build a shock absorber removal mechanism for rail cars. I first showed the VP of Railcar my 2D design, and man let me tell you how proud I was of that drawing set. It was an R13 work of art (anything in R13 was a work of art right….[grin]) Anyway – true story here. The VP looked at me, looked at the drawings, looked at me again and said “Boy, these drawings don’t mean [expletive] to me.” And that was it. From then on out I did everything in 3D. I did ultimately get the design approved if you were wondering. R13 Boolean solids baby!

Another thing about me, if you haven’t figured it out already is that I never take myself too seriously. There is always somebody that knows more than you know, read more books than you did, and are probably better looking too. I figure I have two eyes, two ears, and one mouth and try my best to use them proportionally. That seems to have worked out pretty well for me so far, so you’ll never see me trying to be the de-facto, one and only end all be all expert. I take a look at technology from a standpoint of what challenges can be addressed by applying technology, and then go from there. Top it off with a nice Grey Goose and Soda with a lemon and that’s pretty much me.

The focus of my YouTube series (www.youtube.com/robcohee) , blogs, and other rantings will for the most part be focused on the convergence of building information modeling (BIM) and Digital Prototyping. I will explore where it is advantageous to utilize any one, or combination of Autodesk applications. I will primarily focus on using Autodesk Inventor and Revit in the building product and equipment, and building fabrication industries. Where appropriate, I’ll reach out to the Navisworks, Alias, Showcase, and sustainable teams to provide input and insight into where we could utilize those tools to solve design challenges.

I’m excited to hear your feedback on what I put up here. I do take requests so please feel free to let me know some areas where you would like more information about.

Cheers,

Rob Cohee
Industry Solution Evangelist, BPF
Autodesk Manufacturing Industry Group

P.S. I had a bet with my wife that I could fit in a “whilst…” Winner. Winner. Chicken Dinner!

Interoperability or Collaboration...

Heres another post from Rob Cohee, our resident BPM expert... Enjoy!

 

I’d like to expand upon a discussion thread that I saw on Facebook the other day. It had to do with which application should be applied toward a particular design challenge. Or to be specific, should I use Inventor, or Revit, or Maya, or MAX, or Navisworks, or Alias, or AutoCAD, etc. Yes – use them all, the key is how to determine which one to use. It’s simple really, ask yourself “what is my desired result.” The answer to that question will determine which application, or combination of applications to utilize on a project.

Here’s an example – I want to build a new line of configurable office workspaces. Simple enough, sounds like I fire up Inventor and start creating iAssemblies, right? Well, what if you were working with an Architect to build out a project? Maybe starting with the Revit file to perform some early analysis of the project would be appropriate? Here is where we can start to talk about the difference between interoperability and collaboration. At this stage I want to collaborate with the Architect. I don’t want to, nor do I have any influence to change the design of the building, so I’m not looking for interoperability between Revit and Inventor. However, by utilizing the Revit model to bring in the information I need to perform my analysis on these workspaces I have saved myself a considerable amount of time compared to re-drawing or re-modeling the architectural space. I don’t in this case, require interoperability between the Revit files and Inventor – I just need some sort of collaboration between the two.

Let me expand then on what I mean by interoperability. Interoperability, in this example, would be the ability to open a Revit project file natively in Inventor – AND be able to manipulate the native geometry through parametric or other methods. So if I wanted to move a wall, I could click on the wall and have Inventor recognize the Revit wall element and move, clean corners, adjust schedules, door position, window position – essentially all the things that Revit does, but do it within Inventor. That’s interoperability, and that’s not what you want.

THUD! That’s the sound of someone hitting me on the back of the head with a bat. “What are you doing telling the customers that what they want isn’t exactly what they want?” Sorry guys, that’s the cold hard truth of it. Where is the control in the design process if everyone can edit anything whenever they want? Plus, when you create a single, monolithic application that is good at many things; they become average as a complete solution. Here’s my thought - apply the appropriate technology determined solely by the desired result allows you to determine which purpose built tool to apply to the design; with a higher degree of accuracy and unmatched ease of use. Any one of the Autodesk products previously mentioned is best in class at modeling, drafting, collaborating, and managing every aspect of a project throughout its lifecycle. Check out this example...

 

This should get some blood pressure up... Bring on the comments!