Bernhardt Design, a leading furniture design company headquartered in North Carolina, teamed with internationally renowned designer, Ross Lovegrove, to develop a stacking chair that would push the boundaries of originality, technology and craftsmanship. Called ORBIT, it was originally made only of Scandinavian ash or zebrawood veneer with a variety of painted or natural wood finishes.
While elegant in design and sleek in profile, the innovative wooden chair is also very complex and expensive to manufacture. Bernhardt wanted to remain 100 percent true to the original design, but at the same time, produce it in a more economical material that would be less expensive to manufacture, and thus, expand its marketability.
The solution? Plastics. “The moral of this story is to always talk with a good molder before ruling out injection molding for even the most complex designs,” says Ken Kincaid, technical engineering manager at Mack Molding’s Statesville, N.C., facility. “Even if injection molding looks like an unlikely partner for your design, show your molder what you’re trying to do and ask how you can get there…sometimes solutions are possible, but not obvious at first glance.”
The ORBIT stacking chair is a perfect example of this. But through the combined efforts of Bernhardt, GE Advanced Materials/Plastics and Mack Molding, a solution gradually evolved after weeks of painstaking trial and error. “This was more than just shooting plastic into a tool to get a shape,” comments Zack Lyon, Bernhardt product design & development engineer. “It was shooting plastic into a tool while extending the process to its maximum limits, as well as creating a part that would accept paint without requiring exceptional hand labor and finishing…it’s not just the chair but the finish too, and our customers are very, very picky about that. It had to be a very clean, debris-free, consistent, textured part, and that’s what we’ve been able to achieve.”
Using gas-assisted injection molding
“The first question we had to answer was whether or not we could mold the chair using a gas-assisted process,” says Kincaid. “There were cross-sections of the chair that were close to 1.5 inches thick. And Bernhardt wanted to maintain the integrity of the original design, which meant producing smooth, very stylish contours on both sides of the chair. Even the gas pins had to be hidden underneath the chair where it mounts to the frame. That meant using multiple gas pins with sequencing to direct the material the way we wanted it to go. Gas-assist was really the only option.”
It was a unique project for gas-assist, however, given the size and length of the gas section. “We’re basically filling 75 percent of the cavity with material, and coring out a full 25 percent of the volume of the mold with gas,” explains Steve Langen, Mack Molding program manager. “That’s a tremendous amount of material displacement.”
Mack worked closely with Delta Mold, Charlotte, N.C., to build the tool. After some 15 molding trials, the gas-assist process proved successful in reducing stress, maintaining flat and smooth surfaces, reducing both press and part size, and eliminating thick sections of material.
Developing a new material
While proving out the process, Mack simultaneously worked with GE and Bernhardt to sample possible materials. “We started with ABS and PC/ABS, but they clearly weren’t stiff enough,” says Langen. “So we started moving up the material food chain for more rigorous mechanical properties. We liked a long glass-fiber material because of its stiffness, but then we had to determine the base resin. We tried everything from polypropylene to nylon to PC/ABS with long glass-fibers, but paintability kept bringing us back to the amorphous PC/ABS type of material.”
The result is a new long glass-fiber PC/ABS composite from GE that offers superior tensile strength and stiffness at low glass loadings, which results in a resin-rich surface that can be painted without priming. Called LNP VERTON PCA-F-7004 EM compound, the material provides exceptional strength as evidenced by the Business and Institutional Furniture Manufacturers Association (BIFMA) back test, where it passed twice the normal load requirement with no sign of fatigue or failure.
The compound also provides a degree of flex for seating comfort. “This was an unexpected, but very welcome outcome,” says Bernhardt’s Zack Lyon. “The material gives the plastic chair flexibility that the wooden chair doesn’t have…it’s not only comfortable, but it has a built-in rocking aspect, a fidget factor. It was an unplanned, unpredictable, positive outcome that has turned into a selling feature for the chair.”
The plastic version sells for roughly half the price of the wooden chair and takes only a fraction of the time to produce. It is Bernhardt’s first foray into plastics, but won’t be the last, according to Lyon. “Based on the way things went with this project, Mack Molding will be our go-to molder on the next launch project. The collaborative effort was very important to the overall success of the product.”
About Ross Lovegrove
Ross Lovegrove was born in Cardiff, Wales. He studied design at Manchester Polytechnic, and later, at the Royal College of Art, London. He then worked for the well-known design consultancy, Frog Design, where he worked on such projects as the Sony Walkman and Apple computers. As an in-house designer for Knoll International in Paris, Lovegrove designed the successful Alessandri Office System. He has served as design consultant for many large firms, including Louis Vuitton, Dupont and Hermes.