MCAD Tech News (#244)

9 Jul, 2008

Beyond Parametrics: Designing With Rules

New add-on expands Autodesk Inventor's parametric modeling capabilities.

By Jeffrey Rowe

Jeffrey Rowe photoLike it or not, most mechanical CAD software employs parametrics, a method of linking dimensions and variables to geometry. When values associated with geometry change, the geometry itself also changes. A parameter is a variable to which other variables are related, and these other variables can be obtained through parametric equations. With parametrics, design modifications and creating a family of parts can be performed quickly compared with the redrawing required by CAD packages that don't provide parametrics, although most contemporary CAD packages have this ability built in.

Parametric modifications can be performed in several ways, including via a spreadsheet, script, or by manually changing the dimensional numerical values associated with a digital model. Parameters can define the size and shape of features and control the relative positions of components within assemblies. For example, you can specify the size of a cover plate as: height = width/16, with equations that define the relationships between the parameters.

You can also define parameters that relate dimensions to functional requirements. For example, you can define the cross-sectional area of a part to have certain proportions and withstand a certain load, such as: area = load/material strength * factor of safety.

You can link a spreadsheet to a part or assembly and drive the parameter values from cells in the spreadsheet. Parameters can also be exported to bills of materials (BOM) and parts lists. Read more »

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cadalyst contributing editor Jeffrey Rowe is the principal of Cairowest Group, an independent industrial design, mechanical engineering, and technical communication consulting firm with offices in Colorado and Michigan. You can reach him by e-mail at or by phone at 719.221.1867.


MCAD Modeling Column:
The Current State of MCAD

By Mike Hudspeth, IDSA

Each year, I like to take a look at our beloved 3D MCAD industry and assess what shape it's in. I have to say that it has been a very long time since I've felt the way I do about the future. Gas prices are at all-time highs (which drives up the price of everything else). Myopic companies aren't making high enough profits to suit their goals (despite record performance), so they're laying off skilled workers and sending their work overseas (thus losing their ability to do the real work themselves and weakening the country's industrial capability). And the American worker is caught in the middle, all but helpless to do anything about it. But things aren't all doom and gloom. There's actually a lot to feel encouraged about.

Free Stuff
It has never been easier to acquire MCAD software. Earlier this year, I wrote an entire article about low- or no-cost CAD. You can download programs that can put you on the right path to meeting your MCAD needs. You can explore different ways of doing things without spending too much. Say, for example, you need 2D CAD. Visit the Solid Edge Web site and check out its free 2D drafting product.  Read more »


Mark Your Calendar: MCAD Events

Webcast: Improving Data Management with Autodesk Productstream
July 16 and August 20, 2008
11:00 a.m. CT
This Webcast will demonstrate how Autodesk Productstream can be used for file organization, design reuse, design revisions, 2D and 3D file viewing, and more. Presented by Applied Engineering. Read more »

24th Coordinate Metrology Systems Conference
July 21-25, 2008
Charlotte-Concord, North Carolina
The CMSC is dedicated solely to users of portable, high-precision measurement technology used to inspect manufactured and assembled components on the factory floor. Read more »

For a complete list of CAD meetings, conferences, training sessions, and more, check out our calendar of events on