The Virtual Concept
Direct manufacture from CAD data without prototype proving models or temporary tooling. The dream scenario outlined by Professor Phil Dickens in his address to the World Manufacturing Conference on 29 September 1999 at Durham University triggered an opportunity to compare a virtual vision of a factory of the future where a product or component design in 3D CAD is transformed almost instantly into a production standard item ready to proceed to assembly or finishing for market, with the current day to day reality of an existing manufacturing process operated by Polyurethane casting pioneers Cellular Mouldings of Kettering.
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| A Hypothetical Factory Equipped with Multiples of Computer Driven 3D Finished Product Generators |
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Professor Dickens presented outline scenarios of break-even points in the context of injection moulded parts on existing products showing how over the recent past the speed of stereolithography machines, which at this stage in the hypothesis were the suggested manufacturing vehicle, have increased six-fold in one Mark generation. Coupled with this was the suggestion that many small parts could be generated in the same bed-run ie. Simultaneously, bringing the yield up to levels broadly comparable with injection moulding.
Material properties were also addressed with the recommendation that SLA resins should develop in their own right so that designers can regard them as the final specification for the product rather than an approximation for ABS for example, fit only for evaluation and limited test models.
The logic and vision behind Dickens' clairvoyant analysis is more than just "Jules Verne" and the view from the back of the hall of the nodding heads in the auditorium indicated that some of the senior "movers and shakers" in the industry felt able to identify with at least some of the suppositions if not all of the conclusions.
In his final submissions Dickens, in fairness to the sweeping and conjectural nature of the short overview, did indicate that there was much work to do. Innovative development has yet to be started and chemical research must be directed at novel materials with the properties suited to Design for Direct Manufacture for which concept DDM would seem an appropriate acronym should it require one.
The Reality of One Niche Process
Speaking at the same seminar at the World Manufacturing Congress Tony Sands, a company operating a unique form of Polyurethane casting, quoted that fully functional working parts are the direct output of the process without the need for short run prototypes in temporary tooling. Working rapidly from Designer supplied data in 3D CAD Cellular Mouldings go straight into a production process which has no penalty for one-offs and no practical limit on volume, although the item price acts as an indicator as to when a move to injection moulding can be justified.
Design changes, hindsight modifications, niche market variants and even the transition to Mark 2 can all be accommodated "on the fly" from revised CAD data with minimal time or cost penalty.
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| Typical of the products generated by the Cellular Mouldings method is this set of mouldings for a medical instrument which went from design to direct manufacture without temporary prototype tooling. |
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From the very conception of the process in 1979 the speed of transformation from tooling pattern to cast parts has been faster in measured real time than the generation time of an SLA model by a Stereolithography machine.
Writing in Rapid News (Winter Edition 1993) Sands commented on the arrival of Stereolithography " The advent of computerised methods which can match the rapidity of the Cellular Mouldings method is a very welcome development."
As we go into the new Millennium the process operated by Cellular Mouldings has over 220 registered users, many of whom are Designers whose familiarity with the results obtained has made Cellular Mouldings an automatic choice as the fastest route to market, completely bypassing the prototype stage, using real production parts for tests and market launches, confident that the flexibility of the process will respond to their requirements. At Cellular Mouldings the DDM (Design for Direct Manufacture) concept represents a way of life and Rapid Prototyping is but one link in the chain. Cellular Mouldings is a technically aware organisation using IT, electronic data transmission, sophisticated software, rapid prototyping technologies of all varieties, combined with a well refined and developed manufacturing process which is their intellectual property, to create virtually instant copies of fully serviceable market ready products.
The material issue also has been thoroughly addressed with a continuous development programme resulting in a variety of materials with Cellular Mouldings 6 HI (High Impact) being the staple production resin system for most industrial castings. The process has been "Mainlined" using 4 production streams so that a wide variety of shapes, sizes (thimble to dashboard size) and quantity runs can be accommodated for up to 100 clients simultaneously. Clients access the use of the process via a set-up charge for each project. A master product or cloned SLA is created as a standard for the life of the product and design changes are posted on the master as and when they occur. First production castings can be available in 5 working days from availability of CAD data if the process initiation slot is pre-booked.
The Cellular Mouldings process is not a panacea for all products and the comparison of this niche process with Professor Phil Dickens' far reaching and original view of the future is viable only in the context of products which lend themselves to the characteristics of the casting process but nonetheless the ticks on a check list of criteria of a DDM world where the VIRTUAL CAD becomes the MANUFACTURED REALITY add up to a present day process which goes a long way towards the dream of the future.
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