Anderson Design Associates

ID Firm Uses Gantry Router to Produce Foam Models at
Half the Cost of SLA or Conventional Machining Equipment

By Tim Van Leeuwen - Engineering Manager, Anderson Design Associates Plainville, Connecticut

An innovative industrial design firm used out-of-the-box thinking and found a way to produce prototypes at about half the cost of methods used by most firms. Not only was the initial purchase price of a gantry router less than one-fourth that of stereolithography apparatus (SLA) or CNC milling machines, day-to-day operating expenses are significantly less as well. The router's working area is larger than that of conventional milling machines, and it delivers more aesthetically pleasing surfaces than SLA. In another example of the firm's innovative thinking, the router also serves as a coordinate measuring machine. The benefits to the firm's clients are a shorter design cycle, faster turnarond, the ability to evaluate more design options and lower costs.

Anderson Design is a general-purpose industrial design house with clients in a variety of industries including toys, tools, appliances, heavy machinery, and medical equipment. The company has achieved a consistent record of solving challenging product design problems. Its services range from conceptual design, to focus group research, to engineering, to purchasing and manufacturing support. Many companies choose Anderson Design for its "one-stop shopping" breadth of capabilities. Clients include Becton Dickinson, Black & Decker, Johnson & Johnson, Fisher-Price, Rubbermaid, and Coleman, among others.

Preparing prototype models for client review is a critical part of the product development process at Anderson Design. Until recently, this was done by hand using urethane foam. The company had no way of generating models from its Pro/ENGINEER CAD data unless it went to an outside service. When the decision was made to bring this capability in-house, company officials investigated a variety of options.

Anderson Design first considered SLA, a commonly used method of producing prototype models, but determined that it had several drawbacks. First, it was not suitable for all parts. Aesthetically critical parts with complex surfaces, for example, couldn't be produced with SLA since this technology makes tiny steps or facets in a curved surface. Second, the least expensive SLA system cost about $100,000. Third, that system had only a 12" x 12" by 10" high working area. Many of Anderson Design's projects would require parts made in sections and bonded together. This is a time-intensive and costly option. Finally, because operating expenses are high, SLA models cost nearly twice as much to produce as foam models.

The firm also considered a traditional CNC machine. These machines, made by companies such as Bridgeport, start at $50,000, not including the CNC programming software. To get a model with a large enough working area, Anderson Design would have had to buy one of the larger machines costing at least twice that.

Then a chance encounter in an industrial directory led the company in a different direction. The ad described a new breed of gantry router that interfaced with CAD systems, had a large cutting area, and a low price. Anderson Design ended up purchasing that machine, the Techno Series III from Techno-Isel, New Hyde Park, New York. The price was less than $19,000 and operated from CNC programming software, Mastercam, from CNC Software, Tolland, Connecticut. Its working area of 24 inches by 36 inches with a Z-axis height of 6 inches was large enough for most of the firm's projects. And it could handle all the materials they needed to cut.

After purchasing the Techno machine and related equipment such as clamps, tools for installing clamps, lighting, vacuum systems, cutting tools, and software, the total cost of bringing automated model production in-house was approximately $40,000. Within three days of installing the Techno system, Anderson Design was billing clients for work done on it. This was largely because the Mastercam software was easy to learn. Although originally designed for metal working, Mastercam is also well-suited for industrial design models because of its ability to generate the most complex contours with little programming effort. Mastercam includes IGES, DXF and CADL converters so that geometry can be uploaded from many CAD systems including Anderson Design's Pro/ENGINEER.

Although the Techno router was designed for production routing and drilling on a wide variety of materials including wood, plastic, MDF, solid surfacing materials, and nonferrous metals, so far Anderson Design has used it mostly for cutting models out of seven-pound or 15-pound density polyurethane foam, or #35 or #65 Ren Shape. Typically, 4" thick sheets of 4-foot by 8-foot foam are used, although a few polycarbonate parts have also been made.

The machine's 0.0020 inch resolution and repeatability and 0.003 inch absolute accuracy ensure that the foam models are faithful representation of the designs created on the computer. This is critical in an industrial design application since the models must give the client an accurate likeness of the eventual end product. The Techno router's accuracy is the result of several features inherent to the table, such as the use of ball screws and servomotors. For example, anti-backlash ball screws permit play-free motion that makes it possible to produce accurate circles and inlays. The ballscrews have excellent power transmission due to the rolling ball contact between the nut and screw. This rolling contact also ensures longer life and greater rigidity during the life of the system because of the reduced wear as compared to ACME screws and nuts, which have a sliding friction contact.

The resolution of the Techno router has allowed Anderson Design to use the system in unanticipated ways. Many of firm's projects involve products that must interface with products already on the market. These products may not be made by Anderson Design's client, which means that the industrial design team doesn't have access to the documentation or CAD files that define them. In these situations, the designers go out and buy the product and then figure out how to design an interface to it. 3D digitizing offers one method of capturing the surfaces of the product for use in the CAD system, but Anderson Design has found most digitizing techniques to be impractical. Laser reflective scanning, for instance, generates too much information for the designer to work with since it captures thousands of x, y, and z coordinates. It is impossible to fit a surface through all these points, so much of the data is eventually discarded.

Anderson Design found a better way to get surface data into its CAD system. They modified the Techno router to function as a coordinate measuring machine. After securing an object to the machine's table, just as if it were going to be milled or routed, an operator manually moves the machine's crosshead until a flexible touch probe positioned in the tool holder touches the object. The machine's display shows the x, y, and z position of the probe at that point. This value is recorded manually and after the designer has captured a number of points, they are entered into the CAD system.

The benefit of this technique is that a designer has complete control over the number of coordinates that are recorded. Anderson Design has found that between 70 and 80 planned points give a better indication of the surface than the thousands of points that are captured with a laser scanner. Once the 70 or 80 points are indicated in the CAD system, the designer uses them to guide the creation of the existing object's surfaces. This use of the Techno router once saved Anderson Design six months, the time they would have needed to go through the legal process to get drawings for a particular product. They simply bought the product and captured its coordinates in three days.

In approximately 300 hours of operation, Anderson has had no problems with the Techno router. This is partly due to the strength and rigidity of the table, which is constructed from extruded aluminum profiles that provide easy clamping capability. The router also has four ground and hardened steel shafts and eight recirculating bearings in each axis. This shaft and bearing system produces very smooth play-free motion and an extremely rigid system that produces high-quality cuts. Anderson Design has also required no technical support since acquiring the router. For this company, Windows® PC-based CNC has proved to be an affordable, practical, and accurate option for the production of industrial design prototypes, as well as a good coordinate measuring machine from time to time. To the firm's clients this means shorter lead-times, lower costs and, most important, better designs.