Faster is better, but collaborative manufacturing is essential

I’ve attended the JEC show in Paris for many years, initially as a visitor, then as a part-time journalist and, for the past 10 years, as an exhibitor. I’m often asked what I saw on the show floor that indicates trends in technology, market focus or innovations. The time I have to walk the floor is pretty limited, because I am either tied up on the Quickstep stand with scheduled meetings or interfacing with prospective customers. My opportunity this year came on the afternoon of the third (and last) day, when floor traffic typically slows down and most of the discussions are “exhibitors talking to exhibitors.” So, I zipped up and down the aisles, taking in the show in rapid fashion. Nonetheless, a couple of themes emerged, which are closely related.

The first is the race among thermoset resin suppliers, particularly epoxy and polyurethane, to develop fast-curing systems designed for the manufacture of structural automotive parts. Ten years ago, a 30-minute molding cycle time in resin transfer molding (RTM) was considered the state of the art for carbon fiber/epoxy parts. Several years ago, breakthroughs in high-pressure injection permitted cycle times as low as five minutes. This year at JEC, multiple resin suppliers touted resin systems with under three minute cycle times, with one major company advertising an epoxy system with a 90-second cycle time! These are times that rival engineering thermoplastics and are faster than most high-temperature thermoplastic molding times.

But will the industry really be able to take advantage of these fast systems in continuous fiber-reinforced parts? Or will production rates be constrained by other process steps? In the late 1980s, I was employed at Fiberite, then the world’s largest prepreg supplier (acquired by Cytec Industries, Piedmont, S.C., in 1997). All of Fiberite’s managers were required to read The Goal: A Process of Ongoing Improvement, by the late Eliyahu Goldratt. Written in the form of a “business novel,” the book is the story of a manufacturing manager who faces problems delivering consistent volumes of products in a system of interdependent manufacturing operations, of which some are automated and others rely on manual labor. He faces issues with variability in cycle times, product yields, work-in-process inventory and capacity constraints because not all steps in the process can produce consistently at the same rate.

The protagonist struggles to find a solution, and it becomes clearer to him while leading a group of Boy Scouts on a long hike. Naturally, the faster boys go to the front, causing the line to stretch out (representing inventory accumulation), and the Scouts have to stop often to regroup. After many attempts to keep the group together, he decides to put the slowest boy in front, followed by the second slowest, etc. The group moves at a steady pace, but clearly not at the speed necessary to reach the endpoint on time. When he removes some items from the slowest boy’s backpack (increasing his capacity to walk faster) and distributes them to the faster boys, the whole group speeds up and they reach their destination sooner. He goes back to the factory and applies similar principles to the production line, resulting in lower costs, faster production and reduced inventory. The Goal seems obvious to today’s practitioners of lean manufacturing, but at the time, it was considered leading-edge thinking.

Back to the question above: What will be the rate-limiting operation in the manufacture of carbon fiber parts via RTM? I personally think it will be the preforming/fiber orientation step, but it could also be postmold trimming/machining or inspection, especially for more complex or integrated parts. In order for overall production rates to increase, all the steps must be addressed.

Which brings me to my second observation at JEC. At least five different companies at the show exhibited a carbon fiber roof panel from the R1 Roadster, built by Roding Automobile GmbH (Roding Germany). This included the panel’s fiber manufacturer, Zoltek Inc. (St. Louis, Mo.); the fabric supplier, Chomarat (Le Cheylard, France); press systems supplier Dieffenbacher GmbH (Eppingen, Germany), which did the preforming; Henkel Corp. (Rocky Hill, Conn.), the resin supplier, and the machine supplier/project leader KraussMaffei (Munich, Germany), which supplied the injection unit and press. This group of suppliers, along with a few others not at JEC, collaborated to address all the major issues of manufacture and coordinate the process steps to deliver a successful finished part to the OEM.

I believe this sort of ad-hoc, or better, formal collaboration will be increasingly necessary to overcome inertia in markets such as automotive or offshore oil, which are unfamiliar with designing and manufacturing advanced composites. Collaborations also could accelerate growth within the aerospace industry as it seeks faster and less costly routes to composite manufacture.

Oak Ridge National Laboratory