06.11.2007 | Autor / Redakteur: Ralf Loettgen / Frank Fladerer
Automation has long since found its way up to the level of machine tools. The palette of options range from simple tool changers to the coupling of machine tools into complex production lines. A clear trend toward the integration of different types of fabrication processes is evident.
The automation palette goes beyond individual fabrication processes nowadays. Recently on display at EMO 2007; successfully combined automation of different fabrication processes. Eroding and high speed machining (HSM) or high performance machining (HPM) do not have to be mutually exclusive, indeed they can be meaningfully combined to complement one another (Figure 1).
Why push automation? When one looks at the markets, it is clear that Western Europe, North America and Asia are the central points. Whereas in European industrial centres the reduction of machine hour rates and associated wage costs are the essential motivators, developing Asian countries (i.e. not Japan, Hong Kong, Singapore and South Korea) are primarily striving for better, reproducible quality and greater volumes. As far as motivation is concerned, North America must be classified as being similar to Europe – although the hurdles to technical solutions are taken somewhat easier there when they appear to be commercially plausible.
In Europe and North America there is a desire: to obtain increased productivity and reduce piece-costs, to eliminate disliked shift-work and weekend shifts (for both commercial and humane reasons), and a less problematic means of adjusting output capacity to the fluctuations of order volumes. Another aspect not to be disregarded may be that, in addition to the actual part-handling capabilities, at least the more complex systems offer additional information services (factory management systems) which support the acquisition of data from the fabrication environment as well as acquisition and preparation of order-related data. The demand for reduced production and delivery time is common to all markets.
What are the framework conditions for linking multiple machine tools? Flexible automation solutions integrate the key technologies for tool and mould making, or more specifically, for the production of high-value components. Automation that affords linkage for individual fabrication equipment units must handle some special tasks. A mastery of the individual fabrication processes and their sequence is necessary to solve such tasks. A reliable, functional mechanical system is prerequisite for sequencing. Clearly delegated responsibilities should be viewed as a further prerequisite.
What options are there with modern automation solutions? Automation concepts which have already been incorporated in the framework of machine development – seamlessly integrating mechanical, electrical and control techniques into machine tools – represent the simplest solutions. Such equipment presents a very small risk factor because it is already fully and clearly specified and documented, along with all of its available configuration options, at the time of the first contact between potential customer and sales personnel. The complexity of realisation, the costs and responsibilities for such a purchase are already absolutely transparent from the outset.
Nevertheless, customer-specific automation solutions must be seen as the automation solutions with the most flexibility. These are initially formulated in a project specification between customer and supplier with the help of a technical consultant. A production problem is typically the primary reason for such a customer-specific solution; perhaps it is only necessary to specify suitable automation for a given work-piece or, in an extreme case, a fabrication process must be defined in which the selection of components and the configuration of the complete line is influenced.
One example of this is the „Concept Cell“ system from Agie-Charmilles (Figure 2). It offers process-secure linkage for: high-speed milling of graphite electrodes on a Mikron HSM 300, spark-erosion of mould cavities on a FO 350S, as well as the manufacture of production parts via five-axis high-speed milling on a Mikron HSM 400U and spark-erosion wire cutting on an AC Challenge V2.
The integration of different fabrication techniques requires a great deal of expertise in fabrication processes and a knowledge of the interdependencies between processing steps. More than ever, graphite electrodes are recommended for integrated processes which include EDM cavity sinking. This is because the fabrication of electrodes, done by milling graphite with high-speed milling techniques, does not produce burrs – a central requirement for unsupervised operation of the equipment. The automatic cleaning processes (Clean & Dry) for all processing elements ensures a process-secure quality control and pre-setting (Zeiss Vista), whereby offset data is calculated, managed and utilised automatically.
Completely independent of a market‘s geographic location or the branch of industry, automation solutions for part handling must be examined on a project-specific basis. Experience has shown that a substantial number of projects can be accomplished with relatively simple, economical means, whereas others require sophisticated specifications and a great deal of investment capital.
The linking of machine tools by Concept Cell is done with a seven-axis, linear-travel handling unit from Fanuc Robotics that operates a total of nine chucks (3R system) from 492 magazine positions for pallets. All processes are automatically administered by a master computer with appropriate cell-control software. This system utilises Sigma software from the company GF Agie-Charmilles.
Ralf Loettgen is New Applications manager for Systems & Automation at GF Agie-Charmilles (Switzerland), Tel. (+41-32) 3661300, www.gfac.com
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