Prototype times Crunched at Nike
For Nike Inc., the world-renowned sports company, prototype shoes are a crucial step between new designs and production tooling. Samples produced in-house provide almost the only opportunity for rigorous testing before production starts in hundreds of combinations of sizes and graphics.
To meet its needs for tight tolerances and fast turn-around, Nike has invested over a million dollars in high-speed, high-precision machine tools at its Mold & Tooling Center (MTC) in its headquarters campus in Beaverton, Oregon, USA. Keeping them running requires a staff of six mould designers and programmers, equipped with a range of software including eight licenses of PowerMILL and five of PowerSHAPE. Four types of mould are produced; rubber moulds for the outer soles; foam moulds for the inner soles, uppers and mid-soles; injection moulds for the inserts between the outer and inner soles; and blow moulds for the distinctive Nike airbag.
If need be, Nike can now turn out a set of three or four moulds for a new design overnight. The average turn-around time is five days, including mould design and toolpath programming. To make its investment in top-of-the-line machine tools and highly skilled people pay off with this level of productivity, Nike has aggressively automated the making of tools. The most revolutionary effort is Cruncher, a unique programming system with its own graphical user interface that has been built on top of PowerMILL. PowerMILL was originally brought into MTC because the installed CAM packages could handle neither "point cloud” data from scanning and digitising nor STL files. Both are essential to the reverse engineering methods Nike relies on to handle the large number of tooling iterations as new designs are developed. PowerMILL soon became recognised for its speed, its ability to support shop-floor programming, and its consistent results – job to job, machine to machine. "The biggest differentiator was the speed in creating toolpaths,” recalled Todd Waatti, MTC mould technology developer. "The best other software could do on our test part was twenty minutes and some needed a lot longer. PowerMILL did it in five.”
In addition to its prototyping duties, Nike’s Mold & Tooling Center is also responsible for producing the tooling for custom athletic shoes created for the top athletes sponsored by Nike. The athletes’ feet are cast in rubber or plaster. From that cast a model is made which is scanned and digitised. This data is then converted to a CAD file for the manufacture of perfectly fitting shoes. One recent client was Marion Jones, winner of five medals, including three golds, at the Sydney Olympics.
"As with any automation project, Cruncher was developed by breaking down all the repetitive work,” said Marshall Page, MTC technology development manager. "We took full advantage of the high degree of automation available in PowerMILL.” Todd Waatti pointed out that, "the first step in creating Cruncher was standardising cutting tool practices such as the leads and links. This alone saved the machinists a lot of time and eliminated a large number of errors.”
"From that,” Mr. Waatti continued, "we reached a consensus on what essentially were our best practices – strategies to use on each type of job, speeds and feeds, ramp angles and so on. After a lot of negotiation, we built them into the Cruncher.” Working closely on the project was Stephan Hausmann, a CADCAM programmer for the MTC. "PowerMILL was already at the zenith for macros and automation but we took it to a new level to build a fully-automated CAM system for mould programming,” Mr. Hausmann said.
"Blow moulds for the airbags in the heel are done in one day, thanks to Cruncher,” said Mr. Page. "Originally, blow mould machining alone took a week.” Machining is done at such high surface speeds and tight tolerances that no more than 15 minutes of hand polishing is necessary.
About 80 percent of the toolpathing process has been automated, said Mr. Waatti. The other 20 percent may never be. Instead, the team plans to build more and more upstream operations into Cruncher, like mould design tasks including the generation of parting lines and split surfaces. Already some simple jobs do not even go through shop programming. They go from the designers right to Cruncher and PowerMILL, and cutting the mould starts in as little as two hours. Time saved is put to good use. It allows programmers to improve the mould designs, Mr. Page noted, and to automate more of the process with future versions of Cruncher.