The use of a PC-based CNC machine has helped Altitude Inc. improve the quality of its designs by allowing the company to make more prototypes. The Industrial Designers at Altitude are very concerned with how a product feels in the hand. Although they use solid modeling to document their designs, viewing solid models on-screen doesn't give the sense of how it feels to hold the object. Only prototypes can do that. Before acquiring the CNC machine, Altitude had prototypes made by an outside service bureau at a cost of about $400 for a typical part. The cost and time limited the number of prototypes used in the course of a design. After installing the CNC machine, the cost of a typical prototype dropped to $150, allowing designers to make more of them to better refine a design.

Altitude Inc. is an industrial design company that specializes in ergonomically designed hand-held products. One of the company's more famous designs is the Black & Decker LeashLight. Altitude also designed the Snake Fan for Black & Decker as well as hand tools, game controllers, and consumer electronics for a variety of other clients. The firm employs 18 people.

Altitude's design process begins with sketches as designers put their ideas down on paper. When they present the sketches to clients, they often include foam models so the client has something to hold. Foam models are made by transferring the sketches to Ashlar Vellum CAD program. The 2D shapes from Vellum are used to make templates, and these are used to guide the cutting of Dow Blue Foam with a hot wire. It takes a skilled model maker about one day to make a blue foam model. While these models are good for initial concepts, they are not highly accurate since the process of cutting them requires some interpolation between surfaces.

Once a client has looked at the sketches and foam models and narrowed down the possibilities to two or three concepts, Altitude models those designs in the Pro/ENGINEER solid modeling system from Parametric Technology Corp. Prototypes are needed at this stage as well, both to help designers get a feel for the product and to show the customer. At this point, more accuracy is required than can be obtained with blue foam. In the past, the only option was to purchase this kind of prototype from an outside service bureau. These prototypes were accurate, high-quality, and could be turned around quickly for an additional fee. The main drawback to having an outside vendor do this work was that the cost limited the number of prototypes that could be made at this point in the design. A designer who wanted to feel whether a certain shape was comfortable to hold, for example, might choose not to get a prototype because of the cost.

Since Altitude was creating a solid model of the design, it made sense to use model geometry to produce prototypes in-house. At first, the company considered 3D printers as a means of doing this. These relatively new devices are less expensive versions of larger rapid prototyping systems and are designed to create quick prototypes for design reviews. However, the prototypes produced with these systems require a great deal of finishing--at least a day of sanding for most products-and Altitude didn't want to allot that kind of time to model production. Other drawbacks were the $60,000 cost of a 3D printer and not the fact that it was not highly accurate.

The other option for producing prototypes from solid models was to machine them. At a tradeshow, Altitude saw that many of the solid modeling software vendors were using a particular machine, the Techno Series III PC-driven CNC router, in their booths to demonstrate the machining of parts from their models. The manufacturer of the machine, Techno Isel, also had a booth at the show, and there Altitude evaluated the machine more thoroughly. They had learned that it cost less than $16,000 and was designed for production routing and drilling on a wide variety of materials including wood, plastic, MDF, solid surfacing materials, and nonferrous metals. The price included a CNC programming system, but Altitude chose to upgrade and uses Pro/MANUFACTURE.

The price and the capabilities included in the Techno CNC system seemed appropriate for Altitude's needs, so the company purchased it. The technical specifications of the machine they purchased included a working area for the router of 19 inches by 19 inches and z-axis height of 8 inches. The table features a rapid travel rate of 350 inches per minute, a z-axis cutting force of 200 pounds maximum, 0.0005 inch resolution and repeatability, and 0.003 inches /foot absolute accuracy. A key feature of the Techno servo system is its ability to cut 3D continuous contours at up to 200 inches per minute, far faster than most machining centers. Altitude, however, generally cuts at 60 inches per minute.

Now, when a designer wants to make a quick prototype from Pro/ENGINEER data, toolpaths are first generated in Pro/MANUFACTURE, and then he sends it to the model shop to be produced on the Techno machine. It takes about a day to program the machine and produce a prototype, so by the next day a designer has a part to examine surfaces, fit together, or see what feels good in his hand. If the prototype is destined for client review, some additional time is spent finishing the part. Thanks to the accuracy of the Techno machine, finishing time is minimal. The machine has a positioning accuracy of +1 mm in 300 mm and a repeatability of 0.01 mm. It has anti-backlash ball screws for play-free motion. These screws have excellent power transmission due to the rolling ball contract between the nut and screws. This type of contact ensures low friction, low wear, and long life. The ball screws also make it possible to produce parts to the machine resolution of 0.0005 inch. For Altitude, this means that a part can be sanded down with 220 sandpaper in about 20 to 30 minutes.

Altitude keeps the Techno machine running on average 20 hours per week, although there are situations when it runs constantly. The Techno machine has been very stable and reliable. It is constructed from extruded aluminum profiles that can support all the soft materials Altitude uses. The machine has four ground and hardened steel shafts and eight re-circulating 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. The only performance problem Altitude has had was one of the routers burning out. Since it was a standard Porter Cable production router, they were able to buy a new one locally and have the machine running again in a few hours. The other problem was noise, plus dust, created in an office environment. This was solved by enclosing the router in a cabinet constructed from the same aluminum extrusions used in fabricating the mill.

For Altitude, the Techno CNC machine fills the gap between blue foam models and service bureau prototypes. It provides more accurate models than those made by cutting with templates and a hot wire. Altitude doesn't use the Techno machine to provide the highly finished models they get from service bureaus. These are painted with beautiful lacquer finishes, and Altitude doesn't have that capability in house. Prototypes made on the Techno machine are accurate yet usually not finished to that extent, and serve more as a way of evaluating design concepts. Recently, for example, Altitude was asked to produce a game controller. Designers had eight options for the thumb button and needed to make prototypes to see how each one felt. It was impossible to get fine detail in such tiny parts with the blue foam so all eight buttons were milled on the Techno machine. Using a 1/32-inch ball mill, the model shop was able to produce the parts with the same of detail as the solid models created in the CAD system.