Dutch designer Douwe Jacobs has given the idea of a foldable chair a whole new meaning. The Flux Chair is a foldable design chair made of injection moulded polypropylene. By integrating certain folding lines in the design the chair can be folded up to a very compact size. This way the chair can be stored easily. BPO has given advice on the appropriate production technique for mass manufacturing for this particular design.
When unfolded the Flux consists of a flat plastic plate with a number of folding lines, so called film hinges. The large area of the plate and the small wall thickness at these film hinges make injection moulding of this chair complex. With only one injection point the required clamping force of the injection moulding machine would be much too high. Mechanically weak weld lines, especially near to the film hinges, will cause problems when using multiple injection points.
This is why BPO has looked at two alternative techniques: injection-compression and cascade injection. The first technique has the mould opened a little during the first stage of injection moulding. Then at about halfway through the injection phase the mould is closed and the plastic is forced through the rest of the cavity. The main advantage of this technique is the large reduction in required clamp force. The second technique uses multiple injection points that are activated after each other (in series). That way the problem of the weld lines is eliminated and also the required clamp force is reduced. This last technique was eventually chosen for the product. The production has been allocated to HSV Technical Moulded Parts BV. For more information check the Flux website.