Turning point

For manufacturers keen to lower their production costs, there are many benefits and advantages to taking the plunge and investing in mill/turn technology. Martin Oakham explains


For the increasing number of manufacturers investing in mill/turn technology, the advantages are shortened machining cycles, greater accuracy and efficiency and reduced set-up times — which means lower production costs.

Although 3-axis control is the accepted basis for the majority of prismatic machining applications, there is a steadily growing interest in 5-axis machining. Without question, the benefits of 5-axis set-ups can be substantial, especially when coupled with mill/turn-type machining flexibility.

But without the control software to drive the machine axes, and the CAM software that translates the component designs into cutting strategies the machine drives can work with, multi-axis control would be impossible.

‘We are seeing an increased use of 5-axis machining in production manufacturing,’ said Bill Gibbs, founder and president of software developer Gibbs and Associates. ‘Not only do 5-axis machine tools minimise the number of set-ups required to machine a part, but many of the models being created by today’s CAD systems contain geometry that can only be economically machined using 5-axis technology.’

These include impellers, turbine blades, wing spars and porting on cylinder heads. In addition, many multi-task machining centres, such as Mazak’s Integrex E-series and Mark IV series, incorporate B-axis live tooling to provide even more flexibility and versatility.

Five-axis technology provides the ultimate in control when applying tooling to a part. This provides numerous benefits such as collision avoidance, improved surface finish and reduced tool wear. Newcomers to this technology need a full understanding of the systems available, and how they relate to the work being undertaken, before committing themselves to a considerable investment.

The control aspects of multi-axis machining generally depend on the machine type purchased and the work it will undertake. As such, it is usually dealt with by the machine tool builder. But CAM systems are so flexible that they are very much the responsibility of the purchaser, who must consider the variety and complexity of the components required.

In most cases, the ‘best’ CAM system is not necessarily the one with the most features, but the one with a strong set of standard machining cycles that the user can easily augment. The ideal software enables programmers to create customised routines that extend beyond ordinary toolpaths. Systems that include Visual Basic make customisation easy by supplying an industry-standard macro language. What’s more, users should be able to store their machining knowledge and preferences within the CAM system in the form of a database that can be accessed for use on any part.

In addition, a full library of editable post-processors should be available so users can adjust them to suit their specific machining needs. Realistic simulation of machine movement is also becoming necessary, although this might be in a third party product such as CGTech’s Vericut machine simulation application.

The new GibbsCAM 5-axis software provides a complete range of 5-axis simultaneous milling functionality and, when combined with the GibbsCAM MTM option, can support multi-task machining centres with articulated live tooling. It is also fully integrated with GibbsCAM’s Machine Simulation option, allowing the user to virtually set up and prove-out complex 5-axis programs of the machine tool. This minimises costly machine down time. The 5-Axis option can be used when GibbsCAM is integrated with CGTech’s Vericut.

Companies will probably pack their software with more features as the demand for 5-axis software increases in the UK.

‘The largest markets for 5-axis machining in this country are Formula One, followed closely by aerospace, where take-up of such productivity solutions is growing fast,’ said Richard Nolan, managing director of Open Mind Technologies UK of Oxford. ‘For the last four years 90 per cent of our UK sales revenue has been 5-axis related, which is a big change from our advanced 2 and 3-axis mould, tool & die days. Interested companies are typically small to medium-sized businesses (50 employees or fewer), where the owner, managing director or principle CAM programmer is pushing the limits of the existing CAM system.’

Open Mind’s hyperMILL Version 9.6 includes a new millTURN module featuring machining strategies for turn roughing, turn finishing, grooving and thread turning. Because the mill/turn module is seamlessly integrated in hyperMILL, V9.6/V9.7, users can switch between turning and milling strategies at any time while they are programming. The software also features automatic stock tracking and stock management, a tool database and collision control for all turning and milling strategies.

Sescoi is also an exponent of multi-axis machining. Its ‘WorkNC’ G3 is the third generation of WorkNC, and features a new integrated graphical interface that combines geometry, analysis, machining and verification into a single environment. The interface makes most complex 5-axis toolpaths easy to create, with an emphasis on speed and smoothness.

Verification in WorkNC G3 considers the tool, its holder and the complete machine tool structure, together with the axis limitations when checking a cutterpath. The advances in the new version will allow aerospace manufacturers to cut low-volume, high-value components with confidence, so they can achieve and exceed quality, accuracy and productivity targets.

Additional options for 5-axis machining are also a feature of Delcam’s PowerMILL 8. The most significant of these is a powerful tool-axis editing function that allows for the selection of any region of a toolpath and redefine the tool-axis vectors within that region.

Previously, a single tool-axis specification was applied to a complete toolpath. The new ability to use different options in different regions of the toolpath will enable users to optimise cutting conditions and avoid any sudden machine tool movements that could result in a poor surface finish.

Delcam has also launched a dedicated PowerMILL module for programming and machining blisks and impellers. The company claims this will allow even complex pieces to be programmed in around 30 minutes, compared with the many hours needed previously.