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November/December Feature

This rotomolded carrying case for a 10-foot trade show display includes the back wall, table, graphics and lights.
This screenshot is of the rotomolded carrying case using the Vellum CAD program from Ashlar Inc.
CAD Program ‘TransForms’ Into
A Molded Carrying Case

CAD program combines 2D, 3D and solid modeling techniques to design a rotomolded carrying case. By Arthur G. Carr

The ability to combine 2D, 3D, and solid modeling techniques played a key role in enabling Washington-based TransForm Design to create a rotomolded carrying case for trade show displays. The case is unique in that it can hold all the elements of a 10-foot by 10-foot trade show display, including the back wall, table, graphics and lights. The carrying case was designed for Nomadic Display, a Virginia-based producer of displays.

The design challenge was in figuring out the most efficient arrangement of the display components within it. Diagrammatic layouts created with 2D CAD tools allowed the company to quickly try different arrangements. Once the basic configuration was determined, the part was modeled in 3D to check the fit and interferences. After finalizing the design, solid models were created to serve as illustrations for the user's guide. All work was done using the Vellum CAD program from Ashlar Inc.

A Packaging Puzzle

One of the design considerations for the carrying case was to have it conform to UPS shipping requirements. This would allow customers to ship their trade show displays in the case itself rather than having to put it into another container. Another issue was that the display was one of Nomadic’s newer designs and was still evolving, even as the case was being designed. Also, the modular nature of the display allowed for a number of options such as shelves, table, etc. Finally, the package also had to protect the graphics used in trade show displays.

The initial design stage involved measuring all of the components the case would have to contain. Next, 2D models of each of the components were created in Vellum. The issue of how to include graphics within the case, without damage, was solved by incorporating separate compartments around the outside of the case to store the heavier components. A number of “extras” were included in the design, including a low opening for easier packing and unpacking, a top that doubles as a step stool to adjust lights and graphics, and conversion to a table after unpacking.The fit was checked using a 3D Vellum program. A patented feature called Drafting Assistant was used to identify relationships such as endpoints, midpoints, center points, tangencies, and real and extended intersections. Elements could be changed by selecting them with the cursor and entering new values. For example, when Nomadic decided to increase the size of the fabric panels, the diameter of the tubes, and placement in the case, likewise had to be adjusted.

Preparing Drawings for Rotomolding

After finalizing the design, the next step was to create production drawings. Using 2D, two points were identified and the software automatically added that dimension to the drawing.

Vellum’s 2D drafting tools were also used to prepare section drawings for the rotomolding company. The rotational molding company wanted section views to evaluate material flow during the molding process. Using the Drafting Assistant program, the elements needed to section were automatically located. The program also maintains a temporary relationship between two different views of the drawing. For example, if an area was selected that might be of concern to the molder in a front view, the software placed a vertical line through that location in the side view. As the cursor moved in the side view, a horizontal line appeared and when a point was selected in the side view, the software would place it on the intersection of the horizontal line with the vertical line, giving the location needed to section.

To prepare the illustrations for the user's manual, Vellum Solids, which also has Drafting Assistant, was used. The software created solid models which could be shaded to indicate such things as how the contents should be loaded into the case. The Trimetric view feature also was used to extrude from existing geometry in any direction.

Arthur Carr is the president and chief designer for TransForm Design, an industrial design firm serving industry- and consumer-oriented manufacturers since 1991. For information, contact or visit For information on Ashlar Inc., contact (512) 250-2186 or visit

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Plastics Molding & Fabricating
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