At first glance, an office chair looks simple. But it is a complicated piece of machinery. Done well, the chair will work exactly as intended. Done really well, the chair becomes a piece of art.
Most office chairs utilize a number of plastic parts - most of which are injection molded. Some of these parts are small, some are quite large. All of them have performance requirements, with strict cost constraints. The large parts are the most challenging. They typically have a number of exposed surfaces, with complex contours, and color and appearance requirements off the map. Not only are they structural, they are often integral design elements in the look and feel of the chair.
As always, the angels are in the details - not just in the part design - but also the mold design, the draft angles, the parting lines, the mold textures, the materials being used, the colorants, the gate locations, the processing parameters. The plastic gestalt. For a plastics engineer, working on an office chair is the cat's meow.
I've had the opportunity to work on a number of office chairs in my career. The most recent is the Anthros chair. It is now in production. Check it out at Anthros.com.