KOMET GROUP: Innovations in the cutting process

Broadening the scope for complete machining in a single clamping arrangement

If component machining processes are considered from blank to finished workpiece, complete machining becomes is an attractive strategy. In some areas and to a certain extent, this strategy has already been successfully adopted. However, there are many types of workpiece that require intermediate steps in their machining and, unavoidably, the workpiece still needs to be transferred to different machines or systems. Dr.-Ing. Jürgen Fronius, Head of the Mechatronics Division of the   KOMET GROUP, is of the opinion: “It's worthwhile looking into how we can broaden the scope for complete machining in a single clamping arrangement.”

The reasons to innovate in the field of complete machining are clear: Machining operations performed in one clamping arrangement bring about great qualitative benefits. Avoiding clamping changeovers allows always the same reference system for the production units to be maintained, thereby enabling optimal positional relationships between geometrical features to each other. Then there is the financial reward from wanting to reduce changeover times.

In some areas, outstanding solutions have already been developed for implementing extensive complete machining processes. These include, for example, combining machining tasks such as drilling or milling with turning. As distinct processes, they have conventionally been performed separately on different machines. However, a major proportion of workpieces to be finished today are often characterised by the complexity of their turning contours and essential geometrical properties. In mass manufacturing with the use of transfer lines or rotary indexing machines, this problem is solved by stations equipped with facing slide tools. For smaller quantities and in flexibly organised production sequences involving machining centres, mechatronic tooling systems, such as KOMET KomTronic® U-axis systems, are an alternative solution. They are automatically interchangeable and, in addition to the adjustment mechanism, have integrated the drive components, measuring system, data and energy transfer from rotary motion into stationary machine components. This has enabled machining centres to support freely programmable lathe operations, which eliminates workpiece clamping changeovers to other production units and, in this way, constitutes a specific kind of complete machining.

Even the integration of measurement and inspection tasks is part of cutting edge technology through the use of plug gauges or callipers. By further broadening one's idea of complete machining from the blank to the finished workpiece, one encounters a sequence of machining steps, such as thermal treatment or joining processes, that are inconceivable on today's machining centres given the current state of technological progress. The process chain is therefore interrupted and it is extremely difficult to achieve the same degree of accuracy from one clamping arrangement to the next.

Specifically, this is a common problem in the case of heavily stressed components requiring a relatively high level of precision and are conventionally preworked by soft cutting and then, after thermal treatment, finished by hard cutting. Recently, efforts have intensified to develop appropriate laser optics that can be transferred to the spindle from a pickup station. In this way, the spindle or machine kinematics would become a handling unit that would deliver the laser beam to the cutting point from the stationary laser by light guide. If the process chain could be closed here, i.e. if machining could take place in a single clamping arrangement, it would be possible to realise improvements in accuracy that would otherwise be inconceivable. Fronius explains: “While insert seats can be manufactured economically to an accuracy of around 20 µm today, depending on machine accuracy, a positional tolerance of 4 to 5 µm would be achievable without need for extra resources.” He envisages similarly revolutionary improvements in the integration of joining tasks. There are a lot of modularised products to which the finished elements need to be adapted, such as variable mechanical interfaces, and the finishing process must take this into account. In this area, adaptations to brazing or welding processes would be desirable. Developments here would have farreaching consequences. Not only would they improve the accuracies of products already modularised today, they would also encourage innovations to deliver much greater product modularisation and thereby make production more cost efficient.