Multi-Technology Machining CentreCopyright: Cluster of Excellence Integrative Production Technology for High-Wage Countries
Rapid changes in global markets require high flexibility in production. However, the demands on the achievable product complexity and production profitability should not be reduced. Therefore, one focus for the design and selection of the necessary means of production and machinery lies on maximum productivity. In contrast, further
focus is on the production of any complex components. These commonly contrary poles “scale” and “scope” are an essential part of the research within the Cluster of Excellence and can therefore be found in the mission statement, the polylemma of production technology.
Practical IssuesCopyright: Cluster of Excellence Integrative Production Technology for High-Wage Countries
The project “Development of Multi-Technology Platforms” from the interdisciplinary cluster domain “Integrated Technologies” examines how various manufacturing technologies of traditional individual machines can be integrated into so-called Multi-Technology Platforms (MTP). In order to evaluate the success potential of an MTP, the comparison of an MTP and a concatenation of individual machine tools of the given production technologies can
be performed. Important criteria for a distinction between MTPs and single machines are accuracy, lead times and idle times. Since in principal an MTP can perform several manufacturing processes in a single setup, the operator of an MTP can achieve higher accuracies and prevent waiting and setup times. However, individual machines can also operate in parallel, and thus for a certain minimum number of pieces - at least theoretically - an occupancy rate of 100% can be achieved. The possibility of utilizing all technologies integrated in an MTP in contrast decreases with an increasing number of integrated production technologies.
ApproachCopyright: Image: Thilo Vogel
To make the benefits of MTP available and to be able to operate in an economically viable way, a promising solution is the integration of additional, simultaneously usable workspaces in the MTP. This approach has already been successfully used for single technology machine tools to reduce downtimes. To evaluate the technical possibilities and limitations of an MTP with multiple workspaces, as well as to evaluate its operation, such an MTP, the Multi-Technology Machining Centre was built up. The basic machine consists of the 5-axis milling centre “Mill 2000” by CHIRON-WERKE GmbH & Co. KG, which is already equipped with a milling spindle and two equally and simultaneously usable rotary swivel tables. Within the project the machine has been extended with an industrial robot and two laser processing units, enabling the machine to perform several laser processes besides the main process of milling. One machining head allows wirebased cladding, hardening and material removal using a fibre laser. The second unit consists of a short-pulse laser and a scanner for laser structuring. For the execution of different laser processes and for the work piece handling the robot has been fully integrated into the machine
structure and control. Through flexible combination strategies of the modules spindle, robot and both lasers with the two workspaces a high utilisation of all system components can be achieved.
Technical ChallengesCopyright: Cluster of Excellence Integrative Production Technology for High-Wage Countries
The integration of the industrial robot into the machine was one central issue during development for the mechanical construction as well as for the control conception and commissioning. The robot was mechanically placed on a platform between the two working spaces, which enabled it to reach both working spaces directly. The selected control concept is based on the idea of controlling both the robot and the spindle from the same numerical controller (NC). Axe values are generated for the robot and then sent to the robot controller for transformation and application. Due to the different signal propagation times between the NC and the robot controller, it is necessary to adjust the run times by using control extensions (NC kernel extensions). Since the machine uses high power laser components, a sophisticated safety concept is necessary. As even the scattered reflections of laser radiation can already cause serious eye damage, the entire machine has been surrounded with a double-walled active protective enclosure. Damages to this enclosure immediately trigger an alarm which stops all machine resources. Due to the close integration of the described components, processes and mechanisms within a small space, interactions are to be expected. This can e. g. be the generation of vibrations from a milling process, the thermally caused displacement of the machine bed due to laser power, or heat accumulation due to the safety enclosure. Thus, another research focus is the investigation of these interactions on a mechanical, thermal and organisational level.