Doug Smock, Contributing Editor — Design News, May 18, 2009
Someday a jogger may walk into a shoe store, pick out a style, and then order specific soles and other shoe components based on their weight, running style and other factors.
There’s an emerging convergence of computer-aided design, digital manufacturing and materials technology that may be bringing very personal athletic shoes closer to reality.
A close look at advanced product engineering at New Balance Athletic Shoe Co. in Boston, MA, gives some insight into why. A single shoe sole may have 1,300 features, requiring a like number of molds and dies. Some sole designs may contain up to 1,800 features.
“The complexity at New Balance is due, in part, to the large number of sizes for each shoe, thanks in part, to an insight to offer wide sizes,” says Sean Murphy, manager of advanced product engineering. New Balance is unusual among shoe manufacturers in offering the majority of its shoes in a wide range of widths. For example, men’s sizes range from six to 20 with a width range of 2A to 6E. Styles include: running, walking, tennis, training, basketball, sandals and cleated.
“For the 993 (a men’s running shoe with a blown rubber outsole), we offer 156 unique sizes,” says Matt Dunbar, senior CAD designer for New Balance. “Even infant sizes are offered in wide and narrow.”
That’s when it gets interesting because molds and dies are produced for every unique size. What’s even more interesting is that New Balance cuts steel molds even for prototype parts. “We have rapid prototyping equipment, but they are used more for look and feel prototypes,” says Dunbar.
Look and feel doesn’t cut it for athletic shoe prototype testing. To say they take a pounding would be an understatement. “We will test a design where the runner may land farther forward, and possibly even roll in from the side as their foot lands,” says Pedro Rodrigues, one of the experts in biomechanics who runs New Balances’ brand-new $2 million Sports Research lab in the basement of the former mill building located next to the Merrimack River.
The number of molds and dies cut just for prototype purposes is mind blowing. More than 1,000 for a single shoe sole? It’s possible because New Balance uses tool builders in China, and tools aren’t built for large part runs like they are for most injection molded parts. A single tool may only need to produce a few thousand parts. And the prototype tools aren’t built with a lot of bells and whistles, or even cooling for that matter.
Murphy attended a mold cost estimating program at nearby UMass Lowell’s Plastics Education Dept. recently, and laughingly recalled the high numbers being discussed for tools, like $150,000 and up. New Balance pays a very small fraction of that for its prototype tools.
The New Balance system clearly works and its approach to shoes is a winning model. New Balance is one of the largest suppliers of sports footwear in the world, with global sales of $1.63 billion in fiscal 2007. But it doesn’t run with the pack in many important respects. According to Reuters, Nike spent $260 million on sponsorships last year. The Adidas Group, which includes Reebok, spent $90 million sponsoring the Beijing Olympics last year. New Balance eschews expensive sponsorship programs. New Balance also makes a different mark through a substantial U.S. manufacturing presence, even though much of the manufacturing and materials technology has migrated to the Far East.
The New Balance World Design Center is located in Lawrence, MA, and also features shoe manufacturing. Other manufacturing plants are located in Norway, ME, Skowhegan, ME and Norridgewock, ME. The company was founded in 1903 in Boston by an English immigrant named William J. Riley. Shoes don’t have jazzy names, just numbers like the 1500 and the 1306. The strategy helps gives the feel of an old-fashioned company that puts emphasis on products and good engineering.
Next Step: Direct Digital Manufacturing
One of the hottest areas of technology development that could impact design and manufacturing at a company, such as New Balance, is direct digital manufacturing. It’s based on the idea that you can develop short run parts with complex designs using additive fabrication technology that work directly from CAD files. As Murphy and Dunbar indicate, New Balance has significant complexity in its shoe sole designs alone.
Murphy was asked if New Balance considered using the approach as an alternative to making short-run steel molds. To date, it wasn’t part of the New Balance plan. And given the deals in China today, maybe the economics aren’t quite there yet. But they soon may be. At least that’s the impression given by executives at companies that make the equipment and the materials.
The capabilities of the equipment rise exponentially almost yearly. And the big-name players in the materials’ business are getting interested, developing special grades for the technology.
The key material for athletic shoe soles is thermoplastic polyurethane. There are several important product lines such as Estane (Lubrizol), Elastallon (BASF), and Desmopan, Texin and Utechllan (Bayer MaterialScience). Dow sold its TPU business to Lubrizol in January.
BASF has been partnering with Adidas to develop an improved cooling effect through use of fine-mesh ventilation panels. A special TPU insole performs like a fan, reducing heat generation by 20 percent while fine membranes allow any moisture build-up to escape.
Another trend for athletic footwear is the use of different TPUs in the same part, such as a shoe sole, through a co-molding or other assembly process. “Engineers now have more flexibility in design,” says Tim Jacobs, NAFTA TPU market channel manger for Bayer MaterialScience. For example, there are new grades of Texin TPU that have a very high modulus that can be mated with soft grades. The stiffer material forms the structural backbone, while the softer material provides cushioning. Some of the co-molded parts even use micro sections that can be soft or hard, depending on the requirement.
“Engineers are also pushing the envelope to find material that is as soft and clear as possible,” says Jacobs. A new Utechllan grade, for example, is transparent even in a 100 mm section used for testing.
None of the sources contacted by Design News; however, see development of a TPU for direct digital manufacturing on the near-term horizon.
However, considering the complexity of sole designs, relatively short product life and huge range of prototype tools required, it just may be coming some day.
New Balance Takes off with 3-D CAD
To accommodate the complexity of organic shapes, SolidWorks’ models can have up to 3,000 features
Think about a running shoe and the construction seems pretty basic — there’s the upper part, complete with laces, the side walls and, of course, the rubber sole. Building a 3-D CAD model of this configuration has to be a far simpler task, as conventional wisdom would have it, than creating a similar 3-D model for a complex engine or machine part.
Well, that’s not necessarily the case. New Balance, which had global sales of $1.63 billion in fiscal 2007, can have anywhere from 500 to 3,000 features in a single 3-D model, and that’s mostly to accommodate the rubber sole on the bottom of its athletic shoes. A typical CAD model, which New Balance produces in SolidWorks, has anywhere from 1,300 to 1,800 features — a striking number, due to the increasingly complex nature of today’s footwear designs.
“No one is really doing a single SolidWorks’ part file that has anywhere close to that many features,” says Matt Dunbar, senior CAD designer for New Balance’s Advanced Products Div. “Even though there are only a few components in a shoe sole, they are really organic shapes and that means a high level of complexity.”
The growing complexity in footwear design and the need for faster turnaround pushed New Balance to move from 2-D design to 3-D CAD design nearly eight years ago. Prior to using SolidWorks, it could take up to 15 days to create a 2-D drawing of a shoe design. Today, with 3-D CAD, that same process takes about five days. “Given the complexity of modern shoe soles, 2-D CAD is not an option,” Dunbar says. “2-D data would have so many cross sections that it wouldn’t be practical.”
One of the primary challenges to building a shoe sole in CAD has to do with organic shapes. Companies like New Balance are continually pushing the envelope in terms of shape and construction as a means of creating visual interest in their shoes in addition to the features that enhance performance. “Twenty to 30 years ago, athletic shoe soles were straight walls and a die-cut piece of foam cemented to the upper with a slab of rubber,” Dunbar says. “That design has progressed with the evolution of 3-D CAD and CAM. Now we can model and mill all these organic shapes to add value.”
Because there are few flat surfaces with today’s designs, the organic shapes mean little tiny features, many of which aren’t noticeable to the untrained eye. Closers, different slopes and countless nooks and crannies are what constitute the different features in a typical New Balance SolidWorks’ 3-D model, Dunbar says. For example, consider the bottom of a typical running shoe sole, which has dozens, maybe hundreds, of little lugs. Each lug might be made up of five to 20 features and the lug sizes will vary, depending on where they are located on the shoe.
This variability adds to the difficulty of using 3-D CAD, Dunbar says, because his team can’t take advantage of patterning or other capabilities offered by parametric 3-D modeling programs like SolidWorks. “It’s difficult to use patterning, not just because 3-D patterning tools could use some work, but because each of these lugs is not identical, on purpose,” he says. The feature tree adds another layer of complexity. If you have a feature tree with 1,300 features, and you need to make a change to feature 12, you could be asking for trouble. “You have to hope the software can rebuild the other features and maintain some relationship to the original underlying surfaces,” Dunbar says.
In addition to SolidWorks, New Balance employs Rhino, which is more of a free-form 3-D modeler, to handle some of the more difficult organic shapes. For instance, Rhino is better suited for modeling the “stability web” area of the shoe, which is the raised area under the arch. “It’s more in tune with doing an organic shape like that because you don’t have to worry about the history tree,” Dunbar says.