Plastic Injection Moulding Specialists. Est 1948.

Brief

In 2009 Westons were approached by Queen guitarist Brian May who planned to publish a book on the stereoscopic photographs of TR Williams. It was proposed that the book would reproduce Williams’ stereoscopic series ‘Scenes In Our Village’, and so would require a flat packing plastic stereoscope included with the book to enable the reader to view the pictures in 3D.

Brian had been unable to source a stereoscopic viewer that he was happy with, and so came to Westons with the intention of putting his own viewer design into production.

Having already produced card prototypes, Brian had a firm idea of what he wanted from his viewer, what he did not know was exactly how the injection moulding process would work for the design, what the benifits and pitfalls would be, and what considerations would need to be taken into account in order that the injection moulding manufacturing process would be successful.

CAD Component Design

We began the project working closely with Brian and co-author Elena Vidal to develop what became the OWL viewer, modeling it using CAD software and eventually resolving the design as a two piece polypropylene moulding with snap fit lenses to be inserted at the time of manufacture.

Prototypes

The development stage involved several prototypes. The most important being a polypropylene model with fully functioning hinges (of which there were 6), runners and snap in lenses. This prototype model was CNC machined from sheet polypropylene on our Hurco, giving a very accurate indication of how the final moulded version would behave.

Tooling

The design was approved from the prototypes and on Brian’s request we began tooling here in the UK in our onsite workshop.

The fixed half core insert plate set up on our Bridgeport Milling machine for the drilling of ejector pin holes.

An eyepeice core showing the tracks created by the CNC milling program.

Spark Erosion of an eyepiece core. A copper electrode is lowered onto the steel and an electrical current passed through it. The result is perfect erosion in the form of the copper electrode.

The OWL tool features two laser cut inserts. The London Stereoscopic Company Logo was cut from CAD files supplied by Brian which used the original London Stereoscopic Company artwork.

Brian May, Elena Vidal and Reid Weston viewing test mouldings.

5 mould trials occoured before production took place. The tool was designed with certain tolerances in place which were tweaked minutely to perfect the stiffness of all of the clips, the runners and the snap in lens fit.

Elena Vidal, Brian May and Tony Weston reviewing test mouldings.

Brian May, Elena Vidal and Chris Dodman with the final book and viewer.

Manufacturing

Brian requested that the material colour should change during the run and so 15 different colour masterbatches were mixed into the virgin material sequentially. All mouldings were used including the ones produced as one colours mixed into another. It took S.B.Weston only a few days to manufacture and assemble the 8.8k multicoloured viewers for the books initial run.

Conclusion

The OWL Stereoscopic Viewer project came to a successful conclusion for S.B.Weston Ltd as we despatched the 8.8k mouldings for packaging into the book slipcase having met our deadline. The most important aspect being that Brian was very happy with the final product, which is now getting very good reviews – the book is still in the Independent top ten book list a month after release.

Tags: Brian May, Cad Cam Tooling, CAD Component Design, Injection Moulding, Polypropylene, Stereoscopic Viewer

We are experienced in the way Polypropylene behaves when injection moulded and are able to design in features that will maximise the properties strengths and eliminate its weaknesses.

The shrinkage of Polypropylene is largely influenced by processing conditions, hence, ultra close dimensional tolerances on mouldings are difficult to achieve. On the other hand, for assembly purposes, the resilience and resistance to stress cracking of polypropylene diminish the need for close tolerances.

Polypropylene –S.B.Weston’s packaging and storage box production occurs in Polypropylene due to the materials resistance to fatigue, its light weight toughness, rigidity and excellent resistance to chemical attack or ‘leeching’ all of which which make it very suitable for our range of storage boxes.

Live plastic hinges are often made in polypropylene. The material is selected due to its resistance to corrosion and chemical leeching and its resilience towards most forms of physical damage such as impact and freezing.

S.B.Weston use three main grades in the production of our boxes: A Polypropylene Homopolymer for our Regular Boxes which while strong, is not impact resistant and becomes brittle in very low temperatures. A toughened Copolymer – our TOUGH Boxes – which is impact resistant even at low temperatures, but is a whitish semi-opaque color in its natural state. And a Random Copolymer which combines the improved toughness of the toughened copolymer with the transparency of the regular homopolymer.

Tags: Copolymer, Homopolymer, Materials, Polypropylene, Random Copolymer

Tags: Acetal Resin, Copolymer, Homopolymer, materials, Polycarbonate, Polypropylene, Random Copolymer