- Dr.ir. G.R.B.E. Römer
- Dr.ir. R.G.K.M. Aarts
- Dr. B. Pathiraj
Research of the Chair of Applied Laser Technology focuses on the development and application of technology for laser materials processing. To that end, the fundamentals of laser-material interaction is studied and subsequently processes are improved by the development and exploitation of sensoring and monitoring and/or real time feedback control. Research is currently mainly focused on:
- Micro- and nano processing using ultra short pulsed laser sources with pulse durations in the femto and pico-second regime,
- Real-time control strategies for laser cladding and welding.
Laser micro and nano processing
The production of micro- and nano-structured surfaces with femto- and pico-second pulsed laser ablation is an emerging and promising technique for which continuously new applications are encountered that may result in completely new devices. It is e.g. applied to metal master surfaces that are subsequently used for reproduction by injection moulding or rolling to produce super-hydrophobic mass products. In addition research is conducted into the physical aspects of the interaction of ultra short laser pulses with materials.
In general the results will contribute to bridging the micro – nano manufacturing gap. Many nano manufacturing processes are based on lithographic techniques that have driven the silicon wafer industry, but increasingly the new drive is for low cost, high precision products based on non-silicon materials like polymers, ceramics, and metals. The need to structure these materials in the size range 100 nm – 10 µm, has led to the development of a new range of process technologies and laser micromachining is one of them. Miniaturization and high precision are rapidly becoming a requirement of many industrial processes and products. As a result, there is great interest in the use of laser micro fabrication approaches to achieve these goals. A next step will be the development of laser assisted deposition of patterned layers.
Laser ablation of steel causes small bubbles with sizes of 20 - 50 nm and very fine ripples.
Example of lasertexture used for superhydrofobic surfaces.
Real-time control strategies for laser cladding and welding
The quality of clad layers is modelled by considering residual stresses in clad layers and substrate material. Experimentally, the melt pool width is measured with a CMOS camera. These measurements are used to control the heat input to guarantee good-quality clad layers as required by industry. Optical sensors are developed to monitor the welding process and sensor data are related to the quality of the realized welds. A feedback controller uses these data to adjust the laser power and/or welding speed in real time. Modelling of the unsteady physical phenomena in the weld pool (keyhole) is essential for a better understanding of the process, interpretation of the sensor data, and development of new sensor concepts.
Laser cladding of industrial parts.
Laser machining is a highly automated contactless process at high speed. The moving parts of the system have to be designed with low reduced masses. In case of 3D products often complex 5-axis movements are required. The theme robotics and machine dynamics is addressed to tracking control of robotic manipulators for instance for laser welding of three dimensional seams in sheet metal or for other industrial processes. The main challenge is to obtain the required accuracy at high speed.
For an overview and details of (inter)national research projects currently carried out, see the list below.
Knowledge is transferred to industry by process- or product oriented application studies where real industrial problems are solved, as well as by workshops, Master Classes, and an annual Industrial Laser Event. Knowledge is also disseminated through the Laser Application Center (LAC), which is a spin-off of the Chair.
The facilities of the Chair include two state-of-the-art laser laboratories, including a clean room for micro and nano machining. Laser sources in these labs include:
- 4 kW, CW Nd: YAG (Trumpf), equipped with optical fibers as beam delivery system.
- 1W Titanium Sapphire femto second laser (Coherent)
- 50W, picosecond pulsed laser (TRUMPF)
- 600 W, CO2 Starcut laser (Rofin Sinar)
- Scribing laser, YAG (Haas)
In addition different workstations and robots are available for the machining of 3D parts. The ultra-short pulse laser sources are stationed in a state-of-the-art clean room. Further, the Chair has the availability of numerous analysis tools, including, but not limited to:
- optical microscopy,
- Scanning Electron Microscopy (SEM),
- Atomic Force Microscopy (AFM),
- Confocal Laser Scanning Microscopy (CLSM).
The Chair is (or was) involved in research projects industry including, but not limited to: ASML, Philips, FEI Company, Fiat, TNO, Holst Centre, Coherent, Trumpf, NXP, Tyco Electronics, Xio Photonics, Stork, and IMEC.