Supporting role…

CAD played an important part in the development of a new brassiere concept for underwear manufacturer, Charnos.

In June 1998, design company Seymour Powell was asked to rethink the design and construction of the humble bra. The remit, from underwear manufacturer Charnos, was challenging: ‘Go back to fundamentals’.

The result was an entirely new concept, replacing conventional under-wiring with a much more high-tech co-moulded polymer insert – in a construction, believe it or not, inspired by a kind of frisbee with a hard middle and soft edge.

While the development of this project has had an unprecedented public exposure (it was even the subject of a TV documentary) what is less well-known is the process by which the first rough sketches from Seymour Powell eventually took shape as the finished product.

So here’s how they did it.

Database of busts

To start with, the initial sketches were taken into early CAD models using Alias Wavefront for form generation. Then, after early assessment of 3D elements produced by stereolithography, Seymour Powell tried them out on rigid dressmaker’s busts. But these were not realistic enough.

At this stage PDD, a London-based product innovation consultant was brought in. Its starting point was to capture digital representations of the shapes of real women.

With the help of Nottingham University and Coventry-based 3D Scanners, 180 volunteers were laser-scanned. The images of each bust were averaged to create a unique database of bust shapes, and SDRC’s Imageware was used to generate Nurb (non-uniform rational B-spline) surfaces for a range of cup sizes from which Seymour Powell and PDD could begin to evolve structural shapes.

Scanning provided accurate data but it could be used only to generate digital forms for either the unsupported bust or one held in a conventionally under-wired bra. However, the scanned data did provide a basis for scale and proportions for the 3D form, and allowed the project team to get closer to the final shape of Bioform much more quickly than by using traditional measuring techniques.

Phil Shade, senior designer at PDD, says: ‘It was clear that the variety of shapes meant the geometry had to be far more than a mean average.’ PDD then made silicon rubber moulds from the Alias surfaces and produced foam castings. These wired-foam armatures were used in comfort trials.

Alias Wavefront’s communication software, Surface Studio, was chosen for its freeform modelling capabilities. Scans taken into Surface Studio enabled the designers to exchange and modify 3D forms using IGES export files. At PDD, the files were imported into I-deas, an engineering form-generator.

One of the early challenges facing PDD was to select the thickness of the armature – the structural element of the Bioform bra. From the wearer’s point of view, this needed to be thin enough to make it invisible and comfortable but also needed to provide improved support while being robust enough to withstand repeated washing.

I-deas’s 3D models were sent to Arrk Formation, which carried out the rapid prototyping. From the SLA models, PDD made silicone rubber moulds and vacuum-cast prototypes.

The development process was relatively straightforward. The designers started off with the SLAs that gave a shape, but were hard. These were used to make silicon tools and then to cast foam rubber containing the under-wire from an ordinary bra. PDD next moved on to producing two-shot castings using a hard armature casting and a soft rubber.

Creeps under load

SMP in Torquay made the ‘soft’ tooling. The large blocks of mild steel used for soft tooling (‘soft’ tools are not fully hardened and do not include full tooling or cooling) were cut from I-deas files via IGES into Delcam Powermill. After this, Charnos stitched the prototype mouldings into several hundred bras, which were consumer-tested.

But that was not the end of the engineering process. In early 1999, Ove Arup was commissioned to conduct finite element analysis.

It may sound surprising to submit a bra to FEA, but here the aim was to assess how the bras behaved under load. PDD had anticipated a measure of creep under continued load, which the tests confirmed. Although some creep is beneficial during wear for user comfort, the tests and FEA indicated that a material with more creep-resistance was needed for the final product.

PDD sent an IGES file from I-deas to Ove Arup, which returned its findings with a report and an animation. PDD then made the modifications, and the Bioform bra, in its final iteration, was complete…