Time-Compression Technologies

"Rapid Short-Run Production Helps Rush Unique Product to Market "

Right-the-first-time aluminum tooling yields homegrown rapid prototyping and production-quality injection parts for product start-up. 

“One speaker at the 2002 American Mold Builders Association Convention said that China has a double-barrel shotgun pointed at U.S. manufacturing,” according to Terry Wohlers, president of Wohlers Associates, Inc. ( Boulder, CO) www.wohlersassociates.com — a consulting firm specializing in prototyping and rapid product development. “One barrel is pointed at the molders and the other at the moldmakers. One bright spot is that U.S. companies continue to design and prototype in impressive numbers.”

The American-made Segway® Human Transporter (HT) www.segway.com is a prominent example of excellence assisted by American moldmaking skill. It’s the first of its kind – a self-balancing personal transportation unit designed to give riders the ability to move much faster than walking and to and carry more. Users commute, shop, and run errands more efficiently while adding a little fun to their day. It also makes businesses more productive by allowing workers greater visibility, versatility, mobility, and carrying capacity.

The manufacturers and design engineers of the Segway HT, seeking to shorten time-to-market without sacrificing quality, found some key time- and cost-saving benefits in the emergent field of rapid injection molding. The combination of Segway engineers’ use of 3-D CAD and one supplier’s Mastercam®-created high-speed machining CAM toolpaths let the Segway engineers expect super-fast turnaround from 3-D CAD drawings they sent via the Web to Dynamic Plastics, Inc. ( Chesterfield Township, Michigan) www.dynamicplastics.com.

The DP advantage: People using technology

As specialists in rapid manufacturing of prototype plastic injection molds for customers who need small but high-quality parts runs, speed is everything for Dynamic Plastics. DP also provides production runs of up to 50,000 pieces from its 25,000 square foot facility. “The skill of our triple-duty moldmakers sets us apart from a lot of our competition, DP tool foreman Tom Prebelich says. “For most jobs, they not only create toolpaths and do the machining; they do their own design work. Our choice of what we feel is the cad/cam/cnc program with the most user-friendly interface allows our crew the latitude to apply a wide variety of their skills to get the whole process done quickly and accurately.”

For Dynamic Plastics, these triple threat technicians, the company’s materials selection experience, and fine-tuned shop floor scheduling flexibility are key to the shop’s reliable rapid proto-production. Co-owner Jim Connell credits Mastercam-driven design and toolpathing driven by Mastercam® software for DP’s accurate-the-first-time machining in high-quality aluminum -- setting them up for production right from the prototype stage.

Staying on the right path

Cutting mold tooling in QC7 aluminum from virtual model-verified toolpaths, DP quickly produced injection-molded prototypes; Segway staff reviewed the prototypes and sent minor changes in their geometry back to DP. Since Mastercam (by CNC Software, Tolland, CT) features associative toolpathing –the CNC software automatically adjusts all pertinent toolpaths to conform to the changes in the geometry – DP technicians either modified the mold tooling or created new tooling as necessary with drastically reduced turnaround.

Unlike other rapid prototyping methods, rapid injection molding created real, production-quality injection-molded parts for Segway in just a matter of days. Compared to traditional injection molding methods, rapid injection molding typically cuts both costs and lead-times by as much as two-thirds.

Teaming up on the project

J. R. Hoell, a mechanical engineer for Segway, had outsourced to DP earlier in his career and asked Connell and his partner, Joe Doss, to bid on moldmaking and limited production of several parts during the development of the HT. For Segway, this added up to production-quality parts in product-introduction quantities – minus the added start-up expense of steel tooling.

Joe Doss was DP’s project manager for the Segway projects. Doss, designer Jim Minch, and tooling manager Prebelich worked out production details and time-saving mold design alternatives with Segway technicians and designers. Doss felt that Segway’s team was particularly open to talk over ideas and listen to suggestions. He says, “We tried to use our experience with materials and Mastercam to help make the projects more easily tooled, with as simplified a process as possible for improved production speed and quality.”

Versatility is a must

The angle and direction in which the rider leans controls the HT’s speed and forward/reverse selection; function controls and indicators are in the handlebar. One handgrip steers the HT in a 0º turning radius, and the control shaft telescopes to adjust to individual riders’ comfort. Dynamic Plastics made the prototype/production molds for the control shaft’s two-part height adjust collar , a two-piece ferrule with overmolding and, as the project progressed, battery cases, trim parts and a three-part, multi-material hemi-wedge for the braking mechanism.

A wedge drives supplier and customer together

Molded in a two-step process and finished by two secondary operations, the Makrolon® polycarbonate resin base of the brake part is overmolded with a pattern of clear plastic pads. These provide the friction that helps the part act like a brake shoe. Finding the material with the proper coefficient of friction for smooth braking resulted from ongoing collaboration on materials selection between Segway engineers and DP’s Joe Doss. Once DP cut the molds, the team followed a test-and-remold strategy until, with the help of purchasing manager Jerry Barranca, Doss’ suggestion of Texin® thermoplastic polyurethane (TPU) hit the mark.

The first “shot” molded the body of the piece, with deep voids left in the body of the part to secure the Texin to it in the following operation. For the overmolding, designed a plug to keep the Texin from filling the accessory hole.

Ever faster; even better

“The production time constraints and our own quality control don’t leave room for dealing with flash, either,” reports Prebelich. “The mold parts must fit right the first time out. For the overmolding step, cutting accuracy has to be absolutely precise so the face of the tooling shuts off, leaving just the “bumps” without getting Texin all over the face. Using Moldplus, an add-in for Mastercam, we copy the run-off and parting line surfaces for the cavity mold into the core mold layer for that perfect fit. In the seven years we have used Mastercam’s Moldplus add-on, it has given us a time savings of up to 70% on the most complex jobs.”

When slower is faster

Under high production conditions, the plug would be pulled from the part as the mold halves separated and the slide would set it back in place for the next piece as the mold closed. DP opted for hand-insertion and removal, though, because Segway needed prototypes fast and, right on their heels, production parts. The time saved in not designing and machining the automatic actuation dramatically cut the time-to-customer in the prototype stage.

DP continues to supply the part in moderate quantities, so that same design and fabrication time and dollar savings continue. One simple but astute addition to the process brings the cycle very close to automated speed. Operators remove the molded piece, plug and part, immediately set a second plug in place in the mold and, while the next part is in process, remove the first plug – now ready for the third go-‘round.

Cutting more time at cutting time

As tooling foreman, Tom Prebelich ran the program through the shop. “Our technicians can take virtually any kind of file into Mastercam,” Mr. Prebelich observes, “and move the job right along. In a real rush situation like this, we’ll separate the customer’s model, design the cavity mold, and hand that off to another operator so machining begins on the job even before the whole mold is designed.”

Pete Anders, DP’s Molding Foreman, worked with Doss and Prebelich to establish the molding process parameters and parts sequences. This simplified tooling, further reducing cost by saving time in designing the action and machining it. With 13 designer/programmer/machinists on DP’s staff, there’s no waiting for qualified personnel to throughput work on any project.

Cutting in real time

“We like to do an intermediate “semi-rough” surface toolpath, stepping down to a ¼-inch bullnose mill with a.020-inch radius,” Mr. Prebelich says, “to get it closer to the finish dimensions but still perform a fairly aggressive cut. Since our software remembers what it has cut, I was able to use the leftover feature with a much smaller cutter — a .060-inch flat or ball mill, depending on the geometry — to clean up just the stock left from corners and details missed by the larger cutters. Finally, surface finish contour and, in some places, surface finish parallel toolpathing gave us an extremely clean mold surface finish.”

Rather than adding machining time, Dynamic Plastics’ three-step progression of toolpaths results in faster results. Running appropriate feed-and-speed rates for each successive cutter in the progression keeps feed speeds high without pushing the tools to their respective limits. With this rough to semi-rough to finish combination, larger cutters give greater speed while leftover, with its quick cleanup, completes the details with time to spare.

Reports on the Segway HT hail the machine for its superb functionality, elegant design, and high quality. Mr. Doss says, “Mastercam gave us the accuracy needed to produce parts quickly and at a level of quality in keeping with Segway’s engineering idealism.” And Jim Connell adds, “It’s DP people like Betsy Weichel, our quality manager, who help us stay that way.”

A prototyping bonus

Along the way, DP machined main housing and gearbox casing prototypes composite]from the same QC7 aluminum used for the molds. The extra-hard QC7 aluminum is the foundation of DP’s turnaround time and production quality. Using Mastercam-optimized feed/speed rates, Dynamic Plastics machines the QC7 so no material gums up the tooling or stock. In this early development stage, Segway got rapid aluminum prototyping of future parts with the same super turnaround DP’s toolpathing and machining advantages gave to their plastic prototypes and start-up production pieces.

Growing a fast, flexible shop

Dynamic Plastics owners Joe Doss and Jim Connell tell a story typical of many niche moldmakers: he started in a garage, invested in quality cad/cam/cnc software, took increasingly complex rush-delivery jobs, hired, trained, and expanded his workforce. That was 11 years ago.

Now Dynamic Plastics employs 12 moldmakers and 13 support/management staff. “We’re always being pushed to get things ‘today’ at production quality,” says Tom Prebelich. “We’re now in the process of fine-tuning production even further using the Solids functions of Mastercam. Our moldmakers can’t believe it’s so easy to use. The time saved by Solids offsets the learning curve with no slowdown on the floor, so they’ve getting up to speed by using Solids on real projects.”

The configuration of Dynamic Plastics’ production process — from their choice of materials, software, and equipment to the decision to train their technicians as designers/programmers/machinists — contributes mightily to the company’s rapid turnaround and solidifies their place in their niche market.

And the customers are happy. They get rapid prototyping at first-line production quality and production runs that suit their startup needs, all from a single, low-cost mold. Betsy Weichel, Dynamic Plastics’ QC manager consistently confirms that their products meet customers’ quality specifications. Escalating offshore market competition is driving customers’ demand for higher quality, economy, and faster turnaround. Flexible, knowledgeable niche shops like Dynamic Plastics are already good to go!