Machine Design

Software with the unwieldy moniker GW3Dfeatures lets users create complex curves and surfaces.

 The cross section is of a helix or coil spring bent 90 °. Checking interference on such a construction starts by typing in a minimum gap into the field near the bottom of the menu. The software calculates the minimum radius the coil can go through while maintaining clearance between coils. The distance from the centerline of the helix to the sketch or graph controls the pitch. The farther the sketch from the centerline, the greater the pitch in that area. The length of each line segment controls the distance the pitch lasts. After selecting the Radius law, the distance from the centerline to the sketch controls the radius diameter. The pitch is constant. The farther the lines are from the centerline, the greater the pitch diameter. The length of the line segment again controls the distance of the pitch diameter. A helix can be governed by both a pitch and radius sketch. The results would be difficult to design by almost any other technique. Wrapping flat surfaces produces smooth continuous surfaces without seams.

It's an addin for SolidWorks' 3D CAD system. The curve and surfacing software works so well inside the CAD system that it doesn't seem like an add-in tool. Editing, for instance, is done just as you would in SolidWorks. A few curve-specific features include C1, C2, and C3 curves (curves with sharp edges, those tangent to a surface, and continuous curves, respectively). There are also variable pitch and variableradius helixes, as well as surface wrapping and unwrapping. Attention to detail has made GW3Dfeatures easy for our users to learn.

Helix control is easy and flexible. Start by creating a simple sketch that looks like a line graph. It defines pitch and its variations. And transitions between each pitch can either be smooth or abrupt. The number of transitions is unlimited and can be edited, even deleted without difficulty even after the helix has been created.

Another sketch varies the helix radius. This lets users create variable pitch, variable-radius springs in one command. An option to create a swept surface along the helix at the same time the helix is generated is another option. Usually, helix geometry increases files to unmanageable sizes and slows the computer system. But the software reduces file sizes and trims rebuild time. The software calculates arc circles used for the surface so that it reduces buckling or bulging of the surface as it turns through a small pitch.

The software also gives users a minimum radius for bending a coil around a curve. This allows modeling a coil without the coils overlapping on the inside portion of the bend as the coil compresses. Checking for a minimum radius is another option I have only seen in this software. Overlapping coils in the model are said to self-intersect, which can result in display problems that eventually affect the drawing.

The software's wrapping capabilities are also useful. It lets users wrap almost any shape imaginable. Begin by creating the shape as a flat pattern. This makes it easier to create the pattern or shape because it uses standard patterning and feature tools. Then by defining a circumference, once again by a sketch, the software wraps the shape to either a partial or full circumference. This shape can also be thickened to form a solid. Solids created from these surfaces have been so perfect users can fillet and chamfer edges on a complex shape by simply using standard modeling features.

Before GW3Dfeatures was available, using edges of wrapped shapes as guides was either impossible or time consuming because of edge discontinuity and a large number of facets that defined the surface. Wrapping a flat surface usually formed a problematic seam where edges come together. The software eliminates issues in the area of the seam that would have prevented fillets and chamfers from propagating through those areas. Now adding these features is done more frequently.

The extensive surfacing, sweeping, and lofting capabilities of the software allows for additional shapes more complex than SolidWorks alone could produce. For example, the ability to control twist and transition conditions lets users create shapes with the exacting control needed. Full control of U and V parameters (values that define points on a Nurbs surface) as well as surface normals make achieving the correct shape much easier.

Training is currently only available through the developer. But between the online help and step-by-step instructions, the software is not difficult to learn. If someone has a background in surfacing and solid models, they can learn to use GW3Dfeatures. About the most difficult thing to get used to is the new terminology that describes features. But the developer is readily available to help.

When it comes to support, the developer is one of the best. They listen to suggestions and regularly ask for feedback on new features. Some of our suggestions-have been added to the software the day following the request. For instance, we sent them files that were not giving the expected results. They corrected the error, stepped us through the feature, and sent out an update soon thereafter.

GW3Dfeatures comes from
31878 Del Obispo #118-332
San Juan Capistrano, CA 92675
(949) 728-1309

Mark Holzapfel

Mark Holzapfel is principal designer at Boston Scientific Corp.

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