Activities Applied Laser Technology

Permanent staff A.J. Huis in ’t Veld, G.R.B.E. Römer, R.G.K.M. Aarts

Research objective

Research objective is the development and application of technology for laser materials processing. The laser material interaction is studied and processes are improved by sensoring and automation.

New processes are developed for micromachining using ablation by femto- and pico second laser pulses. Improvement of processes and process control are the objectives for laser processes like cladding and welding. Other laser processes are applied, including drilling, cutting, hardening and alloying.

Knowledge is transferred to industry by process- or product oriented application studies where real industrial problems are solved.

Research topics

The following research topics are distinguished:

1. Laser micromachining processes

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.

2. Laser cladding and welding

Within the other laser processes emphasis in research is on 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.

3. Robotics and machine dynamics

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.

4. Lasers

Lasers itself are no part of the research programme although they are frequently used. Attention is given to properties of the beam in relation to beam delivery, material interaction and safety and interfacing the laser in a fast machining (software) system.

The available lasers are:

4000 W CW Nd: YAG (TRUMPF)

1W Titan sapphire femto second laser (Coherent)

50W picosecond pulsed laser (TRUMPF)

600 W CO2 Starcut laser (Rofin Sinar)

Scribing laser YAG (Haas)

All Nd: YAG lasers are supplied with optical fibers as beam delivery system. In addition different workstations and robots are available for the machining of 3D parts.

National and International Co-operation

The laser laboratory co-operates with several external partners

•M2i: Materials innovation institute (former NIMR): Within this institute projects are done on laser welding, laser cladding and micromachining

•STW: Stichting Technische Wetenschappen

•ELAN: European Laser Application Network. Development of software for laser training and education

•CRAFT: research on laser surface treatment

•IOP: research on laser surface treatment

•LAC: Laser Applicatie Centrum (co-operation of the University of Twente with the Metaalunie. The Metaalunie is the largest employers’ organisation for small and medium enterprises in the metal sector in the Netherlands. This national centre located at the Royal Metaalunie in Nieuwegein makes use of our laser laboratorium to support SME companies in the Netherlands in product- and process development system design, education and training.

•7 FP: several European projects are under preparation

Current Ph.D. Projects

•Ir. M.N.W. Groenendijk, ‘Fabrication of ultrahydrophobic surfaces by femtosecond pulsed laser micromachining’ (IOP-precision)

•Ir. D. Iakovou, ‘Development of an integrated robotic laser welding head’ (STW)

•M.Sc. N. Karlitskaya, ‘Laser die transfer’ (IOP-precision)

•Ir. J.T. Hofman, ‘Application of impact resistant layers on low alloyed and mild steel by laser surface modification’ (M2i)

Other research projects

•Ir. J. Olde Benneker, ‘M2i – knowledge application, demonstration and transfer projects’

•Ir. J. van Tienhoven, ‘Design of hydroformed parts for laser welding’ (M2i)