Ice cream in Yorkshire

When a leading UK ice cream manufacturer wanted to expand sales through local convenience shops, they came up with a point of sale concept using pre-packaged soft dairy ice cream cartridges and a foolproof, low cost dispensing machine.

A great marketing idea, but how could they turn the concept into a well engineered machine at the right price for small retailers, and get it delivered in time for the 2003 summer season?

Enter Nick Dearden from the Yorkshire company Deardens. Dearden runs a ‘virtual company’. With a small core of permanent staff and a network of well-qualified freelance specialists and subcontractors, he can grow and shrink project teams as the work demands, while combining high quality and efficient workflow.

For this project, his ‘virtual’ team was spread all the way from Devon to Tyne and Wear, covering everything from 3D solid modelling, stereo-lithography and finite element analysis to endurance testing, tool making, parts production, assembly, documentation and distribution.

At the centre of the design process is Cobalt – Deardens’ 3D solid modelling CAD system from Vellum Software in Cambridge. Cobalt is the senior member of the ‘Designer Elements’ family of desk-top graphics and CAD software, specifically tailored for product designers. Nick Dearden particularly likes Cobalt’sintegrated 2D/3D technology, which allows him to work flexibly between 2D drawing, 3D solid modelling and ‘free form’ surfacing.

As Nick says, ‘Cobalt is the heart of our virtual prototyping design and development process, supplying all our solid modelling, 2D drawing and image rendering needs in the one package. After initial hand sketches, we move as fast as possible to a digital solid model of the outside form for approval purposes, complemented by stereo-lithography as necessary. Then we develop progressively more detailed models to create the ‘virtual prototype’ that generates all the downstream 3D information for mechanism studies, engineering analysis, tool making and manufacture. At all times we can see exactly what we are doing.’

No less than 100 design reviews of the dispenser were required, so the ability to e-mail rendered 3D images and engineering drawings was absolutely crucial. With marketing in mind, the design of the ‘swirl’ predictably produced much debate, especially as it was likely to require some expensive mould tooling. Cobalt’s ability to do complex surface modelling paid off here, enabling 6 different swirl designs to be SLA-modelled for evaluation.

As soon as the ‘virtual dispenser’ had been approved (with Photoshop promotional artwork added to the Cobalt solid model), full sized SLA models were made, sprayed up and used at trade fairs to promote the product in advance of its launch. Meanwhile, the designers were shelling out the solid model, adding the interior metal structure and designing the operating mechanism.

Some 15 sub-contractors were involved in product development and production, most of them requiring 3D geometry in one form or another. Malton Laser supplied and prefabricated all laser cut and bent components, Sheffield Hallam University performed the finite element analysis on critical components, taking Cobalt 3D IGES files into Pro-Engineer, interfaced to their Ansys CAE software. Rapid prototyping bureau Amsys imported Cobalt STL files for SLA modelling. 2D and 3D IGES files were used by several contractors producing metal parts, one of the most important being the highly stressed cartridge support ring.

In the process of designing the critical parts of the machine Deardens had become familiar with the pitfalls of extruding potentially frozen ice cream. For strength and stiffness, as well as food hygiene reasons, the support ring had to be a stainless steel casting, produced by Advanced Castings in Birmingham.

So now the mechanism existed, but how long would it last? Here was where the best of computer technology had to be supplemented by good old-fashioned mechanical testing, and quickly. Once more, ‘Nick’s Network’ proved invaluable: Bob Mackrel of Laidler, Devon, designed a special purpose electro-hydraulic rig that put the dispensing mechanism successfully through 200,000 operating cycles. That was the green light for production.

All the ‘curvy bits’ of the dispenser casing are injection moulded by Hillside Plastics, County Durham, with a few of the less complex parts vacuum formed by ESP Plastics – 14 components in all. Moulding capacity was a key factor, the larger parts of the dispenser cover being in the ‘Flymo size’ category. Tooling, of course, was a major consideration, with only five months from product concept to launch and with the complex ‘swirl’ requiring a four-part tool to cope with the undercuts! Fortunately CP Engineering of Bolden in Tyne and Wear, a Nissan supplier, was fully equipped to meet the challenge using their Delcam Powershape 5020 CAM system to import Cobalt 3D IGES files.

Finally, product documentation – the better it’s done, the less chance there is of problems arising in the field. In this case, 28 pages of illustrated assembly and operating instructions were produced because Cobalt outputs 2D perspective line drawings and exploded assembly views from the solid model almost automatically. Add notes, and the job was done!

After only five months from concept to delivery the ice-cream dispenser went on sale in April 2003.