Using computer-aided manufacturing (CAM) software called Hypermill from Open Mind, mould manufacturer Fylde Precision toolmakers has reduced dramatically the time it takes to generate programs for high speed metalcutting of plastic injection moulds. During a benchmark trial against other software, Hypermill took just 45 minutes to generate NC code from an autodesk mechanical desktop CAD model incorporating engraved characters on a curved surface, whereas Fylde estimate that it would have taken three hours using its previous CAD/CAM system. Blackpool-based Fylde, whose UK, Irish and American customers range from small plastic moulders to multinationals like Black and Decker, Lucas and Polaroid, is increasingly producing its moulds directly on a machining centre from blocks of hardened steel.
This is in preference to the more conventional but longer method of producing a graphite electrode and then spark eroding the mould by ram-type electric discharge machining.
Says Roger Wolfe, a director of Fylde, 'Cutting graphite is fairly simple but machining hardened steel is a much more demanding application as a wrong cutter path can ruin both the tool and the mould.
Sophisticated Z-level strategies are needed to avoid such expensive mistakes.' Fylde ventured into CAD/CAM during the mid 90s when Black and Decker started to supply designs as Catia CAD data files.
Roger Wolfe remembers, 'The CAD side of our system was good and allowed us to verify the manufacturability of the design and even suggest improvements, which today's customers expect in addition to top quality work, competitive prices and fast delivery times.
The CAM functions, however, were relatively poor so we ended up with inefficient machining cycles which took a long time to produce'.
So the company researched the market for a new CAD/CAM system and identified a combination which Mr Wolfe describes as 'heaven sent', comprising Mechanical Desktop CAD and Open Mind Hypermill CAM.
Not only did it produce the outstanding benchmark machining test results mentioned above, but it is also capable of accepting CAD designs in a variety of data formats via IGES and other graphical exchange protocols.
Unlike many other CAM systems, Hypermill is fully integrated within Mechanical Desktop, so it runs inside the CAD program environment.
Thus there is only one data model for the entire design-through-manufacturing process.
Hypermill offers a number of functions that make life easier for the mouldmaker.
In addition to standard cycles expected in a modern CAM system, such as profile and Z-level roughing and finishing, the software offers features that free the operator from repetitive work.
One example is the slope machining function.
To achieve a high quality finish when cutting steel moulds, the surfaces have to be machined according to their angle of inclination.
On flat planes, profile finishing is the most efficient strategy, while on steep surfaces the Z-level finishing achieves best results.
Conventionally, the operator has to analyse the CAD model to decide which surface should be machined with which strategy.
Then borders are drawn around the areas so that different machining strategies can be applied to them.
HyperMILL performs these operations automatically.
The model is analysed by the software and all surfaces steeper than a preset angle are machined automatically with Z-level finishing.
The operator is able to review the proposed machining sequence using the on-screen simulation and can edit if necessary.
The NC programs generated are downloaded to the shop floor for prismatic machining via an Ethernet link.
An example of Fylde's CAD service is illustrated by its co-operation with Black and Decker, which recently developed a power tool with exchangeable heads.
Based on a prototype model, the casing was designed by Fylde incorporating various changes which not only reduced the manufacturing cost but also, after modification of the interior, allowed the case to be used for three different power tools instead of one.
Roger Wolfe draws attention to the know-how which is required to produce top quality moulds.
The design of the hinges of the power tool case, for example, are critical.
If the material is too thin in this area, the plastic will change colour under stress and eventually break; too thick and the case would be difficult to open and close.
This section of the casing mould must be machined to within 10 microns to achieve the optimum result.
Europe, if not the world, is a single market these days in the toolmaking industry and the strong pound is not helping UK suppliers.
Serious competition comes from Portugal and the Far East.
Roger Wolfe stresses that to combat the threat, UK manufacturers must be able to supply high quality moulds and tools in short lead times.
State-of-the-art CAD/CAM software such as the Autodesk Mechanical Desktop and Open Mind Hypermill combination is paramount in achieving this.