As he set out to design a new chair for Herman Miller Inc., Jerome Caruso took a serious look at swimming turtles.
He was drawn, he said, to the way water could both support a turtle, yet also respond to its movements.
``The most important part in seating is the surfaces,'' the industrial designer said in a June 9 telephone interview from his Lake Forest, Ill., office. ``I thought, `Wouldn't it be nice if those surfaces could have intelligence, could respond in different areas to different portions of the human anatomy?' ''
The chair he created for Zeeland, Mich.-based Herman Miller, the Cella, provides that reaction, he said, and it does so with a patented design that relies extensively on injection molding.
Working with molder Cascade Engineering Inc. of Grand Rapids, Mich., and mold maker CDM Tool & Manufacturing Co. of Hartford, Wis., Caruso came up with a system that uses 1,540 individual polymer cells that loop together to provide both support and a flexible surface.
And because the design and tooling allow Cascade to injection mold an entire polypropylene and Kraton styrenic block copolymer seat surface or back in one shot, the Cella is one of Herman Miller's least-expensive seating offerings.
The chair rolled out at the Chicago NeoCon office furniture show June 13-15 starts at $564 - a 25 percent savings from the company's Aeron chair and 10-15 percent below its midpriced Mirra.
``Because the cellular suspension design was so efficient, and with its [injection molding] process and the price of the material, we decided we could show the world we could do a mid- to lower-priced chair with the Herman Miller name on it without compromise,'' Caruso said.
By comparison, the Aeron relies on a multistep process to make its suspension seating, starting with a flat fabric panel that must be encapsulated in an injection molded rim.
``We had to consider how we can stretch the limit of technology and material selection and design,'' said Jim Gingrich, sales director for Cascade's industrial solutions group.
Herman Miller asked Cascade to work with Caruso to bring the Cella concept to life, tapping into Cascade's experience in molding and engineering, and calling on Cascade's sister company, compounder Noble Polymers Inc., to create the custom resin blend.
``This was probably the most collaborative development we've ever had with Herman Miller on a seating program,'' Gingrich said. ``We had collaboration with the designer, with Herman Miller, with Noble and with the toolmakers.''
The heart of the chair is the matrix of 1,500 cells, each working like a miniature plastic spring. The complex tooling and molding puts thicker, more robust cells on the parts of the chair that handle the most weight, such as under the hip bones or behind the shoulder blades, Caruso said.
``We kept using stress analysis and adjusting the size and shape of the zones,'' he said. ``Under the scapulas, they needed very deep loops to be very flexible. In the center, down the spine, there was less flex.''
Spaces between each pad provide space for air to flow between the sitter and the seat, he said.
The Cella marks the first design Caruso has produced from start to finish in the computer, taking advantage of everything from engineering tests to track the stress on the cells under simulated pressure, to computer-aided design and production of the tools.
The project became the largest CAD file Cascade ever had, Gingrich said, forcing Herman Miller and the injection molder to upgrade their computer equipment. The CAD data file for the seat back alone filled 400 megabytes, the seat another 200. A typical CAD file for the company is about 20-30 mb.
