Dec 062011

It’s pretty common to see application stories, where engineering software vendors try to demonstrate why their software is wonderful.

I find application stories interesting, but they don’t really tell me what I want to know: What is the right tool for the job? Or rather, what are the right tools for the job?

I started thinking this way maybe 28 years ago, when I’d see different types of manufactured goods, and ask myself if the CAD software I was using could handle that kind of design.

Even up to 10 years ago, the answer has too often been “no.” Fortunately, things have gotten better—but choosing the right tools for the job hasn’t gotten particularly easier. There are just so many options today.

In the sprit of understanding engineering software tools, I’d like to start a thought experiment: Looking at particular products, and considering what toolsets would be best for their design.

Not that I actually know what the best toolsets would be. I’m not that smart. But I do know a lot of smart people—on both the user and vendor sides of the markets—read this blog.  So, consider this a request for feedback. I’d like to hear from software vendors about their tools. And from people who have real-world design/engineering experience with a particular type of product and the relevant tools. I’ll gather what I learn, and write a follow-up article.

Inspired by an upcoming webinar, the first product type I’d like to look at is a golf club head.

Golf Lessons

This Wednesday (December 7, 11:00 AM CST ), Pointwise, Intelligent Light and the University of Tennessee at Chattanooga SimCenter are presenting a free webinar that illustrates the various steps of the complete computational fluid dynamics (CFD) process typically followed in aerodynamic analyses of realistic geometries.

They’ll be creating meshes with Pointwise, and with tools developed at the UTC SimCenter. Steady and unsteady CFD solutions will be computed on a distributed memory LINUX compute cluster with TENASI, a UTC SimCenter parallel-unstructured Reynolds averaged Navier-Stokes code. Post-processing will be performed using FieldView by Intelligent Light.

For this webinar, they’re using a pretty well-known type of geometry: a golf club head (a wood.)

I assume they chose a golf club head as an example because it’s interesting, and it lets them demonstrate what their tools can do—not because their software is the only (or even best) choice for analyzing golf club head designs. (I’m thinking it’s possibly massive overkill.  But there’s nothing wrong with that, is there?)

What tools does it take to design a golf club head (specifically, a wood?)

The USGA has a set of rules that govern the design of golf clubs (and their heads.) They cover all kinds of arcane details, including everything from the geometry of grooves to the volume of heads.

The goal of club designer is to work within those constraints, maximizing range and accuracy, providing as much forgiveness for swing variations and errors as possible, while making an aesthetically desirable product. (What, you don’t think golfers care about aesthetics?)

The fact that different number woods have differing face angles would suggest that that an ideal CAD program for golf club head design might have parametric capabilities. The USGA rules provide a set of constraints that also hint at using a parametric CAD program.

Still, not all CAD systems can effectively use the USGA constraints as parameters. For example, one of the rules is that a wood head’s volume must not exceed 460 cubic centimeters. For many CAD systems, it’s simply impossible to drive geometric dimensions using volume. It gets worse: The USGA limits the moment of inertia of a club head to 5900 g-cm2. See if you can plug that constraint into most CAD systems.

Woods are aerodynamic clubs, designed to be swung fast. While a wood’s face may be flat, not much else about it is. This implies that an ideal CAD system would have the ability to handle class-A surfaces. Certainly with G2, and possibly with G3 surface continuity.

With any product that’s aerodynamic in design, it’s a given that CFD should be in the design toolset. At least, if you want to compete with the market leaders. If you really wanted to complicate the analysis, you could optimize for under-water shots, for when players need to hit their balls out of  a water hazard. (Or you could add many-body dynamics analysis for when they need to hit out of a sand trap.)

It’s also a given that FEA should be in the bag of tricks, to optimize strength and stiffness within the USGA geometric constraints.

Modal, vibration, and acoustic analysis might make sense too (though these might imply analyzing a full club, not just a club head.) Modal response and vibration figure into performance, but sound figures into aesthetics. Guess which is more important? Karsten Solheim built a golf club empire based on the sound his putter made when hitting a ball: Ping.

Beyond CAD and CAE, there’s the issue of optimization. To do real justice to the problem of golf head design requires going beyond the “red is bad, green is good” school of static FEA thinking. It requires going to the Pareto frontier, to find the set of optimal design solutions. There are a number of interesting tools available to help you get there.

Chances are that, if you’re going to do a truly rigorous design of a golf club head, you might want to model a golf swing. For that, you’ll need a computer algebra system. And, since you’ll eventually want to do testing with physical prototype, you’ll probably want an instrumentation/data acquisition system, to capture and use test data.

And you thought golf clubs were simple.

Well, golf clubs look simple, at least. But they require real engineering, based on real science. That implies that they require serious engineering software tools. I don’t think you can get away with using SketchUp and AutoCAD LT. (As nice as they are for some things.)

The toolset for designing commercially competitive wood heads (which are not usually made out of wood anymore) includes CAD/CAID, meshing, FEA, CFD, post-processing, optimization, math, instrumentation, and probably a half-dozen things I’ve forgotten. I’m not counting manufacturing tools, because, at least for wood heads, most are produced by foundaries using investment casting.

While I could tell you, off the top of my head, what toolsets I think might work well for this design problem, I’m far more interested in hearing what toolsets you think would work best. If you have some thoughts, either leave a comment, or write me a note at