Nano-positioning technology for picosecond laser system Engineered solution for the mechanical stages and motion control system provides the ultra-fine resolution and precision that is necessary for micronn level laser micro-milling. MicroBridge is an open access facility for micro and nano engineering and micro fabrication of parts and components. The specific aim of the facility is to bridge the gap between conventional precision micromachining and lithographic/direct write semiconductor patterning technologies with a range of technologies. The project is based at the Manufacturing Engineering Centre (MEC) at Cardiff University where a combination of expertise and state-of-the-art equipment is made available for companies who wish to develop manufacturing techniques and opportunities for products offering new levels of functionality in diverse areas. As part of the list of enabling equipment available through this open access service is an Oxford Lasers’ Picolase1000, a state-of-theart picosecond laser ablation system capable of micro-milling complex 2.5D and 3D microscale resolution structures in virtually any material. With its ultra short pulse length of 10 picoseconds and average power of up to 10W, this dual beam 355nm and 532nm laser has the ability to remove material at processing speeds that are commercially attractive when compared to shorter pulse lasers and ion beam machining techniques. A combination of twelve optical and mechanical positioning axes allow for the most complex machining including micro-hole trepanning. The machine is capable of a 1-micron spot size under optimum conditions allowing the machining of structures in metals, glasses, ceramics and polymers to just a few tens of microns. To provide the ultra-fine resolution and precision that is a fundamental requirement for micron level laser micro-milling and to maintain the high throughput capabilities necessary to complement this impressive machine, Oxford Lasers chose an engineered solution from Aerotech for the mechanical stages and motion control system. The complete system was supplied as an integrated and fully tested assembly in a process that involved collaborated engineer-to-engineer participation. Two interchangeable low-height mechanical stage configurations were used to ensure that laser structures could be machined to the high levels of accuracy and within the complex geometries required. Both configurations included 600mm x 300mm fully sealed ALS25000 series direct-drive linear stages for general micron level X-Y alignment and a 4mm travel ANT-4V vertical stage with nanometre level resolution for Z axis depth machining. The vertical stage included a dowelled mechanical alignment interface for fast changeover between two nanometre level positioning solutions - an X-Y precision aligned ANT50-L linear direct drive nanopositioner with 50mm of travel or two ANT-20G goniometric cradles with 20 degrees of nanoradian resolution angular rotation around X and Y axes. In addition to the main 5-axis system, Aerotech also supplied an ATS150, 100 mm travel ball screw driven stage fitted with a brake for general vertical adjustment of the laser system. The complete system was controlled with the A3200 Digital Automation Platform, the control system with a Firewire connected 6-axis NPAQ series 19 inch rack mounted servo drive unit comprising both PWM amplifiers for general positioning axes and exceptionally low-noise and highly stable linear technology servo amplifiers to ensure the extreme levels of precision required for the nano resolution axes. The platform was ordered as a 14-axis configured system to allow for straightforward configuration changeover. Oxford Lasers developed its user interface around the A3200 using the Microsoft.NET development environment that helped reduce project development timescales and simplify device integration. The system also allows engineers to develop its own routines easily using a choice of languages. The specification included the Position Synchronised Output (PSO) option, which manages the precise, on-the-fly, synchronisation of the laser’s pulse, power level and firing pattern with the exact position of the multi-axis positioning system. PSO acquires all axis positions using high-speed/real-time encoder feedback to process two or three axis vector positions and provide the laser firing control output exactly synchronised to the 2-D or 3-D contoured position. For this application, PSO was combined with Aerotech’s HALAR option that involves interferometer calibration and error mapping of each mechanical axis to provide a look-up table contained within the A3200. HALAR (High Accuracy Linear Accuracy and Repeatability) improves stage performance to a typical level for a single axis ANT-50L stage to within 5 nanometres resolution and 0.3 microns accuracy. Even with such nanometre level resolution, these stages are capable of speeds up to 250 mm/sec or more and are found in industrial production applications where high speed and high throughput are fundamental requirements. The complete system supplied to Oxford Lasers included a chain type cable management system and all cables complete with interfacing connectors for simple system commissioning. The scope of supply also included "test as system" dynamic testing with complete parameter setup for each axis along with comprehensive documentation, training and on-site support during commissioning. Speed Link InfoService Request more information by e-mail Reader Service No. Reader Number Email Address 00976    Tell a friend about this article:
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