Tuscarora Plastics

CNC Router Shrinks Labor Time for Foam Samples
from Hours to Minutes

Tuscarora Inc. has reduced the labor time for manufacturing foam samples from hours to minutes in some cases. Previously, prototypes of the company's molded foam products were carved by hand, requiring between one hour and eight hours of a skilled craftsman's time. Now, after CNC machines are programmed from CAD geometry, they automatically cut the prototypes. Programming and setup takes about 20 minutes, while actual cutting takes 10 minutes to 4 hours, depending on the complexity of the part. The machines operate unattended except for loading the foam stock and removing finished pieces. "It's a huge labor savings because the prototype makers are free to do other work while the machine is in operation," says Bill Brokob, manager of Tuscarora's western region technical center in Colorado Springs, Colorado. Another benefit of the CNC machines is improved accuracy, especially for the complex 3D shapes that Tuscarora's customers are now requiring.

Tuscarora Inc. is one of the world's largest manufacturers of custom molded products made from expanded foam plastic materials. The company designs and manufactures interior protective packaging and material handling solutions as well as molded plastic and thermoformed components. Its customers are major manufacturers in the high technology, consumer electronics, appliance, and automotive industries. Tuscarora currently serves more than 2,500 customers located in the United States, Canada, Mexico, and the United Kingdom from 30 locations. The company is divided into a foam molding group, an integrated materials group, a thermoforming group, and an automotive group, and an engineering services group.

Product protection and beyond
Tuscarora's foam molding group utilizes a variety of materials such as expanded polystyrene (EPS), expanded polyethylene (EPE), expanded polypropylene (EPP), copolymers such as ARCEL®, and R-MER®, and hi-heat resins. These raw materials are injected as beads into molds, then heated with steam which causes them to expand and solidify into the finished shape. The resulting molded foam shapes protect and cushion fragile products better than virtually any other interior packaging or material handling product available today. Molded foam plastics are also cost-effective, resulting in less packaging labor and smaller carton sizes. In addition to packaging applications, Tuscarora's molded foam plastics are used for products and components with a long service life. For example, foam's unique properties make it an excellent insulation component in building construction, refrigeration, and shipping containers. Recently Tuscarora has begun to offer an innovative molded foam assembly chassis for electromechanical devices that uses molded EPP foam to replace sheet metal and traditional fasteners.

The complexity of molded foam products produced by Tuscarora has increased in recent years, driven by similar changes in the complexity of its customers' products. "Nothing is square any more," says Brokob. As customers create products with more graceful curves, Tuscarora's designers must match those shapes in the packaging components they create. The use of solid modeling has helped them do this. Many customers now provide CAD models of their products. Tuscarora engineers import the models into their CAD system, Pro/ENGINEER, and design the foam packaging components around the customer's geometry.

Most customers request one or more prototypes for testing prior to having the foam parts manufactured. Previously, prototypes were produced by hand. Working from drawings, a prototype maker drew lines indicating the general shape of the part on a block of foam, then used a Bridgeport milling machine to carve out the part. Some fine-tuning was usually required, so he chipped away at the foam with hand tools until it fit the customer's product. This was a slow process, requiring anywhere from one to eight hours, depending on the complexity of the part. It was also somewhat inaccurate. "We could hold a tolerance of 1/16 inch at best working by hand," says Brokob.

Another limitation of making prototypes by hand became evident as the shape of customers' products became more aesthetic. "It was impossible to follow those curves accurately when we were cutting prototypes by hand," Brokob adds. "If we had two end caps, for instance, one for the right side of a monitor and one for the left, the two sides wouldn't always match." This problem was complicated by the fact that as the shapes were getting more complex, customers were also raising the bar on the accuracy of the prototypes. "Some of our more high tech customers have started to demand highly accurate prototypes," Brokob says. "If they want five samples for testing and verification, they want them to be virtually indistinguishable from each other. Hand samples are all different."

The drawbacks of hand production led Tuscarora to consider using a CNC machine to cut the foam samples. As the company looked into this, they found that one option was to purchase a heavy and expensive machining center primarily designed for metalworking. "These machines cost about $75,000 and are more heavy-duty than we need for cutting foam," says Brokob. Further investigation revealed a more suitable alternative, a Techno CNC router from Techno-Isel, New Hyde Park, New York. This machine was designed for production routing and drilling on a wide variety of materials including wood, plastic, MDF, solid surfacing materials, and nonferrous metals. Its $25,000 price was affordable and its 0.003 inches/foot absolute accuracy and 0.0005-inch resolution and repeatability met Tuscarora's accuracy requirements. The company selected a Techno system with a 48" x 40" table size and a Z-axis height extension of 19-7/8".

Labor-saving process
Now, after modeling a new foam part in Pro/ENGINEER, the designer exports the solid model directly into Pro/ENGINEER's CAM program. This eliminates the step of creating drawings for the prototype maker, as was done in the past, because the CAM program generates toolpaths for the Techno router directly from the CAD geometry. Tuscarora has set up its CAM program so that it's "almost just the push of a button," as Brokob says, to generate toolpaths. Once this is done, the CAM file is exported into the ICAM post processor that creates the actual code that drives the Techno router. Total programming time, from when the Pro/ENGINEER model is imported into the CAM program until the machine code is complete, ranges from 10 to 15 minutes.

Another five minutes are needed to cut the foam stock to the right size and attach it to the Techno router. The operator then hits the "start" button and the sample is then carved automatically. It takes only 10 minutes per side to cut simpler pieces, while more complex pieces may take up to four hours per side. One key advantage of using the CNC machine instead of cutting prototypes by hand is that it frees the prototype makers to do other work. The router does not require any supervision, except to remove the finished piece and attach a new foam block to repeat the process. "It's a significant labor savings," says Brokob. "Instead of spending one to eight hours cutting foam by hand, we just attend to the machine as necessary, which takes minutes. We quite often turn on the router when we leave for the day, and when we come back the next morning, one side of a part is done."

After prototypes have been machined, they are checked against the customer's product. This is another area where Tuscarora sees an advantage to using a Techno CNC router. Since parts are cut directly from CAD data, the shape of a prototype matches the shape of the customer's product perfectly, something that was almost impossible to achieve in the past. "The improvement in accuracy is an important part of customer satisfaction," notes Brokob. "It also differentiates us from the other competitors who are still working by hand."

Tuscarora was so pleased with the CNC method of prototype production that the company eventually equipped each of its regional technical centers with Techno routers. The western regional center has three CNC routers devoted to making foam prototypes, and there are 10 in the entire company. Having multiple machines has been very helpful during times when one center has trouble meeting a big order. The company simply emails the machine code to other technical centers, which can be producing the parts within minutes.

Tuscarora has been pleased with the reliability of its Techno machines. Part of their reliability is due to the materials used in their construction. For example, each router uses anti-backlash ball screws. These screws have excellent power transmission due to the rolling ball contact between the nut and screws, and this type of contact ensures low friction, low wear, and long life. In addition, the router is constructed on steel stress-relieved bases with hardened steel linear ways, and ball screws with servomotors standard. The shaft and bearing system produces very smooth, play-free motion and is an extremely rigid system that produces high-quality cuts.

Using CNC routers to manufacture foam prototypes has paid off for Tuscarora in a number of ways: more efficient use of labor, more accurate samples, better satisfied customers, and a competitive advantage. "It has become more and more important that we supply highly accurate prototypes," says Brokob. "With the Techno machines, we can fulfill this requirement in a cost-effective manner."