Modular multifunction micro-machining platform for European SMEs Microsystem technology and micro-machining are innovative key technologies of the presence and future. However, for small and medium enterprises it is difficult to establish themselves in this market as the preconditions consist in a profound technical knowledge, highly skilled personnel, complex and expensive manufacturing systems. The European integrated R&D-project LAUNCH-MICRO pursues the objective to develop selected micro-manufacturing machines which are affordable for SMEs and to support them by appropriate application know-how. Thanks to the funding by the European Community and the cooperation of competent partners now the first demonstrator for a modular multifunction micro-machining platform is available which perfectly meets also the most stringent demands. Figure 1): KUGLER MicroGantry micro5x laser micromachining system with housing according to laser safety standard EN 60825 and Directive 2006/42/EC. Currently laser micromachining and micromilling are very promising machining processes for tools which are applied in the mass production of mechanical and optical microparts by molding, die casting and embossing. Laser processing nowadays is an established wide field. However, a new generation of laser beam sources with ultrashort pulses and high repetition rates has reached industrial application maturity and it offer exciting improvements especially in the fileds of laser processing and micromanufacturing. Short laser pulses in the range of pico- and femtoseconds have high pulse intensities and enable high-resolution, high-quality micromachining of almost all solid materials with minimal thermal and mechanical damage and structure sizes down to the submicron range. It are excellent and universal tools for very fine, direct ablative microstructuring of solid materials and thus complement the limited potential of micromilling ideally. Regarding the machine technology for both processing methods there is a broad common ground. Therefore it is convenient that V3/290224 Page 1/5
a sub-group of the LAUNCH-MICRO consortium (machine tool builder KUGLER GmbH, laser manufacturer LUMERA LASER GmbH and R&D institutes Laser Zentrum Hannover, PROFACTOR GmbH and IDEKO S. Coop.) is cooperating in order to develop a laser machining demonstrator with picosecond laser source close to industrial maturity. KUGLER is building high-precision machining systems by using linear and rotational motion axes which are mainly based on aerostatic or hydrostatic bearings. These cost-intensive systems are well-suited for applications like micromilling, where highly accurate motion cycles with slow or moderate speed are dominant. In contrast laser processing with ultrashort pulses demands for much more dynamics as best machining results are achieved with low pulse energy, high pulse repetition rate and repeated traversing the machining path. Figure 2): Axis configuration and beam delivery system of the MicroGantry micro5x laser micromachining station. Development tasks and challenges regarding the machining system: The challenge consisted in the development of motion axes which are characterized by high dynamics, high mechanical stiffness, high dynamical stiffness of the motor drive and high accuracy of the motion path. In addition a machine structure is needed with high mechanical and thermal stability and high attenuation for vibrations which result from axis jerk or external influences. Laser processing with ultrashort pulses follows with focused beam what means that some optical components of the beam delivery system have to be moved by the linear axes. Therefore a stiff and stable mechanical set-up of the beam guiding components is needed in order to guarantee precise machining. Solution: The design of the laser machining station relies on the well-proved MicroGantry micromilling machine platform of KUGLER and the existing axis arrangement. The vibration-isolated machine base and other essential components of the machine structure consist of special granite with high thermal stability and attenuation for vibrations. Therefore this machine design is principally compatible with the requirements of ultrashort pulse laser machining. For increasing the machining dynamics a new version of linear axes was developed. These direct driven axes are based on precision-ground granite beams and have mechanical precision bearings. Guidances, static parts of the linear motors and the incremental scale of the position measurement system are mounted to the granite carriers. The slide units consist of FE-optimized light weight designs and are driven by two parallel linear motors. These motors provide enough force for accelerations > 20 m/s². An integrated water cooling system minimizes detrimental thermal effects of the motor temperature. Additionally the slides are designed such a way that it do not bend or warp when small temperature variations occur. V3/290224 Page 2/5
The latest CNC-control technique is applied. It is fast in all respects (e.g. reading frequency for position measuring systems, control loops for speed and position, reading and setting I/Oports, handling of voluminous NC-machining programs) and has an open structure regarding an adaptable user interface and I/O-ports for laser interfacing. The user interface of the CNC was supplemented by special features for laser interfacing and laser machining. Development tasks for an industrial ultrashort pulse laser source: For an effective laser processing by material ablation it is important that the laser source can be triggered with short delay time and that the pulse repetition rate is programmable (range 0 500 khz) in order to synchronize laser on/off with motion cycles and pulse overlap (ablation rate, depth of material removal) with the speed of motion. For non-thermal processing pulse duration has to be in the order of a few picoseconds and energy densities on the sample in the order of 1J/cm 2, which corresponds to pulse energies of a few µj. The beam quality is characterized by M 2 < 1.5 with excellent pointing and pulse energy stability. Due to the nonlinear absorption of the ultrashort laser pulses the fundamental wavelength of 1064nm can ablate many industrial materials with excellent quality. Further conditions for an industrial application are a rugged, compact and sealed design of the laser head with no manual adjustment degree for any laser internal optics. Easy integration into the work station and low maintenance and operating costs accomplish the requirement specifications. What is it? Functionality: The LAUNCH-MICRO laser machining demonstrator is a laser micromachining system comprising a focused laser beam delivered from a high repetition rate picosecond laser source, a suitable beam delivery system for guiding the laser pulses from the laser to the workpiece surface and a high-precision 5-axis positioning system for defined, controlled movement of the laser focus over the workpiece. The laser machining process is controlled by synchronized switching the laser on and off, changing the pulse energy and repetition rate, adjusting the focal spot diameter and the speed of relative motion between focus and workpiece. The system is specially designed to meet the requirements of industrial microprocessing and to be affordable by SMEs. The key features of the system are as follows: Positioning system Rectangularity of linear axes < ± 3 arcsec Travel length in X-Y-Z 300 x 300 x 200 mm Acceleration in X-Y-Z 20 m/s 2 Velocity 1 20000 mm/min in X-Y / 1 10000 mm/min in Z Positioning accuracy ± 0,25 µm in X-Y / ± 0,5 µm in Z Straightness deviation in X-Y-Z ± 0,8 µm (per 100 mm travel) Motor drives Ironless linear motors in all axes Position measuring systems Incremental scales with 10 nm resolution Optional rotary axes C-axis or turn and swivel unit on Y-slide CNC-control PC-based multiprocessor path control with integrated SPS and PLC, communication via MACRO-bus Operating system Win XP Professional User interface KUGLER Numeric control software Remote service and maintenance KTS Kugler Telediagnostic System The LAUNCH-MICRO laser micromachining system is deduced from a micromilling machine which can be configurated and operated for true 5-axis machining of complex 3Dgeometries. This capability is important for manufacturing moulds and requires interfacing to CAD/CAM-systems. In addition a precise turn and swivel unit (two crossed rotary axes) is needed for 3D-machining. Such a unit is available with direct drives and angular positioning accuracy of ± 0.001 degree. This technology can also be applied for laser micromachining and allows for instance microstructuring on spherical and curved free-form surfaces. Thus microstructuring is no longer restricted to planar 2 ½ D geometries. V3/290224 Page 3/5
How does it work? Description: The picosecond laser source can ablate any material with minimum thermal side effects and with high precision. When a ps-laser pulse (duration ~ 10 ps) is appropriately focused onto any material surface it will remove a material layer with a thickness in the order of 10 nm per pulse in a basically non-thermal process. The remaining material will not be heated and thus no micro-cracks develop and no burr or recast occurs. The lateral resolution is determined by the focal diameter. Precondition for material removal is that the energy density in the focal area is above the threshold of approximately 1 J/cm 2. Laser machining is localized, noncontact and almost free of reaction forces. The spectrum of laser machinable materials comprises hard and brittle materials as well as soft and even transparent materials. For processing a CNC-operated positioning system creates a defined relative movement between laser focus and workpiec surface. Applications: Examples for industrial ps-laser micromachining include: Drilling small holes and apertures into difficult machinable materials (e.g. IC-boards, semiconductor substrates, bio-medical devices) Micromilling (laminar material removal) of grooves, channels, webs, recesses (e.g. tiny moulds, fluid structures, lab-on-the-chip devices, miniaturized bio-chemical reactors, stents) Production of micro-sieves Cutting and structuring of thin foils Marking and dicing of glass wafers and integrated circuits on semiconductor wafers Cutting or repairing masks for processes in the semiconductor, display and OLED technologies Marking or repairing lithograpy masks Structuring semiconductor wafers and solar cells Nozzle drilling for printing heads and fuel injectors Generating tribologic structures on hardened metal surfaces (e.g. bearing faces, engine cylinders) Preparation of cutting edges and structuring chip leading faces of cutting tools for mechanical machining Modular multifunction micro-machining platform: A modular machine conception for 3 (only linear), 4 (additional C-rotary axis) and 5 (additional turn and swivel unit) motion axes keeps starting costs for users low and enable them to upgrade and adapt their machining system for growing demands. The strategy of using the basic structure of the micromilling machine MicroGantry nano5x for the development of the LAUNCH-MICRO laser machining demonstrator enables KUGLER now to offer optimized machine tools for pure micromilling or pure ultrashort pulse laser processing and a combination of both technologies on the basis of one and the same machine platform and CNC-system. According to the application dynamics and the machining precision required the linear axes performance includes either hydrostatic, aerostatic or mechanical precision bearings. All versions of the MicroGantry machines can be equipped with machine-based CNC-integrated measuring instrumentation as there is a tactile touch trigger probe, a video microscope and a confocal optical distance sensor (resolution 0.01 µm). The signal of the confocal distance sensor can be recorded as a function of the machine axis coordinates so that it can be used for 1D- and 2D-scanning. As all measuring devices are supported by appropriate data processing and evaluation software the MicroGantry manufacturing machines implement the functions of a high-precision multisensor-cmm in order to perform process-integrated pre-qualification of the workpieces. V3/290224 Page 4/5
Figure 3): Referencing of a steel ball workpiece by means of an integrated touch trigger probe (left) and laser scribing onto the ball surface (right) in the MicroGantry micro5x laser micromachining station. Figure 4): Examples for laser micromachining with the MicroGantry micro5x, laser marked surface of a steel ball with diameter 5 mm (left) and laser ablation generated mold of a micro-gear with diameter 2 mm (right). This work was partially funded by the European Community under the FP6-NMP project LAUNCH- MICRO IP, Contract n 011795. Salem, 23.02.2009 Published in: Micro Manufacturing 03 09 Vol. 2 No. 1 KUGLER GmbH Dr. Klaus Baier T. +49 (0)7553-92000 klaus.baier@kugler-precision.com www.kugler-precision.com V3/290224 Page 5/5