Multi-Technology Machining Centre

Cluster of Excellence

Integrative Production Technology for High-Wage Countries

Integrated Technologies

Multi-Technology Machining Centre

Introduction

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 ma-chinery 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 Issues

The project “Development of Multi-Technology Plat-forms” from the interdisciplinary cluster domain “Integra-ted Technologies” examines how various manufacturing technologies of traditional individual machines can be in-tegrated 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.

Figure 2: Machine structure Figure 3: Decreasing costs per piece for small lots

Integrated Technologies

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 utilising all technologies inte-grated in an MTP in contrast decreases with an increasing number of integrated production technologies.

Approach

To make the benefits of MTP available and to be able to operate in an economically viable way, a promising soluti-on 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” from CHIRON-WERKE GmbH & Co. KG, which already

Figure 4: Different laser based manufacturing technologies on a sample workpiece

Figure 5: Motion axes of the robot

Bild 6: Übersicht der Arbeitsräume

Figure 6: Overview of workspaces

is equipped with a milling spindle and two equally and simultaneously usable rotary swivel tables. Within the project the machine has been extended with an indus-trial robot and two laser processing units, enabling the machine to perform several laser processes besides the main process of milling. One machining head allows wire-based 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.

Integrated Technologies

Technical Challenges

One central issue during development for the mechanical construction, as well as for the control conception and commissioning was the integration of the industrial robot into the machine. The robot was placed mechanically 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 to control both the robot and the spindle from the same numerical controller (NC). Axes 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 ne-cessary to adjust the run times by using control extensi-ons (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 sur-rounded 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 compon-ents, processes and mechanisms within a small space, interactions are to be expected. This can e. g. be the ge-neration of vibrations from a milling process, the thermal-ly 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.

Figure 8: Laser deposition welding (Laser off)

Figure 9: Laser deposition welding (Laser on)

Figure 7: Machine and active laser protection housing

Integrated Technologies

Regarding the further development of the demonstra-tor the integration of additional tools and processes is planned for the near future. In particular a cooperative processing of robot and spindle for different processes such as handling operations or the robot-based deburring of components shall be achieved.

Figure 10: Laser deposition welding experiments

Figure 11: Measuring displacement with a laser tracker Figure 12: Investigation of thermal displacement

Displacement Sensors

X-Direction

Y-Direction

Z-Direction

Integrated Technologies

Technical Data

� Milling, drilling, laser deposition welding and laser structuring in a single machine

� Control of all components by a single NC controller � All processes can be used in one clamping � Two workspaces for optimal use of resources (parallel processing)

Technical Equipment

Hardware:Machines & components: � Base machine: Chiron Mill 2000

� 5-axis milling centre � Two identical workspaces, each with a swivel and rotary axis

� Spindle power: 25 kW � Siemens 840D sl with own NCK extensions

� Robot: Kuka KR-16 � 6-axis industrial robot � Payload: 16 kg

� Deposition welding laser � Laser source vendor: IPG � Laser scanner vendor: Arges � Type: fiber laser Yb:YAG � Power: 2.4 kW � Welding head with scanner and media supply (Ad-ditional wire and shielding gas)

� Led by robot

� Structured laser � Highly pulsed � High-precision microstructuring / deburring � Led by milling spindle

� Peripherals (chip conveyor, cooling and ventilation systems, hydraulics, etc.)

� Several camera and test computers � Laser radiation protective enclosure

Software: � CAM-System

� Siemens PLM NX � Extensions for simulation and laser cladding (self-developed)

� Laser control � Lasernet � Inscript

Project Team

� Prof. Christian Brecher Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University

� Frédéric du Bois-Reymond Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University

� Wolfram Lohse Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University

� Johannes Nittinger Laboratory for Machine Tools and Production Engineering (WZL), RWTH Aachen University

Cluster of Excellence

Integrative Production Technology for High-Wage Countries

c/o Werkzeugmaschinenlabor WZLRWTH Aachen UniversitySteinbachstraße 19D-52074 Aachen

Phone: +49 (0) 241 80-25322 Fax: +49 (0) 241 80-22293 Email: xcluster@wzl.rwth-aachen.deWebsite: www.production-research.de