Pro/ENGINEER Surface Modeling

Surface modeling skills allow the designer to move beyond the basic shapes that are used in solid modelers. By using high end CAD software such as Pro/Engineer and understanding the theory of how light reflects off of surfaces and how the human eye perceives this reflected light an experienced surface modeler can turn a clunky design into a freeflowing organic shape that catches the eye of the customer and stands out against the competition.

Advanced Surfacing Techniques

To make good looking plastic parts you need to understand the principals of G2 or C2 curvature continuity and how to use these principals when creating a design. The attractive free flowing shapes that you see on the market today are almost always created in a high end surface modeler like Pro/Engineer that can create and check for curvature continuous conditions. These good looking plastic part designs usually have no flat surfaces or constant radius rounds on major visible surfaces. These designs are frequently based on splines and conic sections that blend into each other in a curvature continuous condition. If a model is created with the major visible surfaces being curvature continuous the human eye can detect no instant changes in curvature and therefore perceives the surface to be continuous and "correct".

Since it is difficult for solid models to maintain curvature continuity between multiple surfaces most solid models are constructed with flat faces, single plane curves, and constant radius rounds. The joint where a flat or a curve transitions into another round has an instant change of curvature that is detected by the human eye and is interpreted as "something being wrong" even if the flat surface is perfectly tangent to the round . This condition is what makes a solid model look "clunky" next to a nearly identical surface model created by an experienced surface modeler that understands curvature continuous conditions.

The "Master Model Merge" technique is a great time saver if you want a look to extend across multiple parts. In this technique one "master model" creates the appearance of the overall skin of the product. This master model is referenced by the various parts such as doors, plugs or others that must be physically different but still continue the shape of the overall skin. Updates to the master model are passed to the individual parts keeping the parts in sync during the entire design process. The picture at right shows the master surface model that we used to develop the KR Industries "Special Edition 2 Ball Rolling Bowling Ball Bag" and the Brunswick "Zone Pro 2 Squared Roller" using the master model merge technique and curvature continuous styling. The purple image at the top of the page is the final molded part. These products have an eye appeal that attracts customer attention and has turned them into best sellers.

Solid Modeling is Not Enough

Modern solid modeling programs have greatly increased the ease with which complex designs can be created. However, if your products need to look good solid modeling by itself will not give you the best looking product possible. The proven technique for making good looking products is to create an appearance surface quilt in a high end surface modeler, use the surface analysis tools in the surface modeler to optimize the surface, create a solid from the appearance surface, and then use solid modeling techniques to finish the parts with ribs, draft, rounds, etc. If you want to create better looking products Product Design has the in house experience applying surface modeling techniques to the design of good looking plastic parts to create products that look better and sell better.

Product Design, Inc.
5133 Washington St., Suite 9
Downers Grove, Illinois 60515

Phone: 630.663.1642
Fax: 630.663.4552
Toll Free: 888.609.6199

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