CAM software brings machining back in house

Following installation of Open Mind's hyperMILL CAM software, TVR has rapidly learned how to take full advantage of its facilities for machining a wide range of geometric forms.

Blackpool is famous as a seaside resort but it is also the home of the UK's most successful domestically owned car manufacturer.

Sports cars made by TVR are justifiably famed for both their shapely lines and a performance per pound ratio that leaves other cars stranded at the traffic lights.

Throughout most of the company's history it has relied on highly modified bought-in engines and transmissions.

However, since the mid 1990s it has funded development of its own individualistic range of engines.

Latterly it has also embarked on development of gearboxes.

This has led to development of machining facilities and installation of CAD/CAM at the factory, including Open Mind's hyperMILL computer aided manufacturing (CAM) software.

It is now an important part of TVR's component development process, providing proven and reliable capability to generate programs to machine components which are an accurate facsimile of the original CAD model.

TVR engine development engineer Gavin Beach comments, "For some time after we acquired our machining centre we were reliant on manual programming methods which placed a major restriction on the scope of our in-house machining activity.

Following installation of hyperMILL we have rapidly learned how to take full advantage of its facilities for machining a wide range of geometric forms.

Just by using the system to program the machine to produce foundry patterns, we have more than saved its cost by not having to employ outside contractors do the work." TVR established its engine development department in 1995.

Its first 'product' was the AJP8 / Speed V8 engine which made its debut in the TVR Cerbera coupe.

This engine has been followed by the Speed 6 in-line and Speed 12 V-format engines, giving TVR a range of in-house developed power units to rival that of any other sports car maker.

This is in addition to the highly modified Land Rover V8 engines which the company also offers in its Chimaera and Griffith models.

"When TVR decided to build its own engines we were almost completely reliant on outside contractors for development as well as for production machining," says Mr Beach.

"In the beginning this was probably a very wise thing to do, but once we became more established as engine builders the cost of development components in particular was seen to be prohibitive, while long lead times on delivery used to interrupt our development schedules.

"We already had CAD-based design facilities and it was decided to add a machining centre for production of small batches of components.

However, without off-line programming we could only hope to do relatively simple two dimensional machining and drilling work." Crunch time came when the company needed to get a pattern ready for a bell-housing casting.

Lack of a suitable component was holding up production of cars so the need was urgent.

Trionics, the North West of England distributor for Open Mind software, had already been in contact with TVR about the possibility of the company using hyperMILL.

As the CAM software is designed for use within the Autodesk Mechanical Desktop environment, the system was a good match with TVR's existing CAD facilities.

"Trionics were very good," Mr Beach recalls.

"They came to see us with hyperMILL and as their demonstration piece they created the program for machining the bell-housing directly from our CAD model.

It took a day to develop the program which we then loaded onto the machine.

Two days of machining later we were able to take off a pattern which conformed exactly to our CAD design.

It was a very impressive introduction to hyperMILL and it also saved us a lot of money and around a month of lead time compared to availability of a commercially produced pattern." Nevertheless, TVR also examined other programming systems before committing to hyperMILL as its in-house system.

However, the more closely they examined the alternatives, the more impressed they became with the Open Mind product.

"The really good thing about hyperMILL is that it does exactly what the manual says it will do whereas some of the other systems we looked at do not," Mr Beach confirmed.

"Moreover it is equally good at routine work like drilling holes and pocketing as it is at complex surface work.

The graphics are not as spectacular as some of the other systems that are around but its functionality is perfect.

Once I've developed a program and done a toolpath simulation on the screen I know that what I'm going to get from the machine is what I've just seen." The system is now wisely used for both development and production metalcutting.

Around 75 per cent of machining centre time is devoted to development, producing 1- or 2-off components, and about 25 per cent is production related.

As well as assisting bell housing and prototype parts machining, possession of hyperMILL has allowed TVR to start using machined aluminium moulds for plastic injection moulded trim components.

Compared to the resin moulds that were previously used, they last longer and provide more consistent finish throughout the mould life.

The system's main function, however, is development of engine, suspension and transmission components.

One of the larger projects to date has been machining of a gearbox casing from a solid aluminium billet.

This included generating a lot of internal features while the finished wall thickness - which had to be machined from both sides - was around 2.0mm in places.

The machine has also been used to produce prototype cylinder heads and camshaft carriers for the Speed 12 engine, and suspension components for the Cerbera sports racing car.

"HyperMILL integrates very well with Mechanical Desktop and offers some useful features for the type of machining that we do, which is almost always from solid billet," Mr Beach adds.

"For instance the Z-level roughing strategy is highly effective at establishing large basic cavities while the profile roughing capability is useful as a lot of the components we machine have 'webbed' surface features to provide rigidity and torsional strength.

The automatic rest milling feature also saves us a lot of time.

Likewise we're very keen on attaining a good surface finish and the finishing strategies available in hyperMILL ensure that we can do that." But the major advantage of the system from Mr Beach's point of view is the confidence that the system inspires.

"Once I've viewed the simulation in the 3D verification module, hyperVIEW, I'm happy to commit to cutting metal.

In the recent past I've had to do this at the end of a very long day when I could easily have made a mistake.

In practice I know that if the system says everything is OK, then it is.

We also get good technical support from Trionics, which is very helpful.".

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