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First step is to sketch a map of the customers task and write in, what he is already able to do

We formulate the aim of the customer, so that it implies a solution of the problem Then we put some details within the landscape (areas that he can not walk/drive

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Diagnostics: Capture reality = see what happens in your process Identify dependencies = plot a map, with important dependencies; main routes Formulate your goal

Reduced Models: Do not try to solve the hole problem. Do not want to model the whole reality Focus on your problem

Method: Here the experience in modelling and simulation is required

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Meta models tell us, how to set up a model. Which parameters have a lot of influence and should be considered in detail. A good meta model is able to tell us the structure of the problem. Then we can see, what our reduced model should be able to show.

We also use meta models to optimise the processes in case of many criteria.

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The center of our competences is to calculate the movement of free boundaries. For example the melting front during cutting. The melting front moves through the workpiece. The movement of this boundary through the workpiece is the cutting process.A lot of subjects are needed to describe the movement of those boundaries.

Hydrodynamics are required to describe the melt flow and its effects on e.g. quality criteria.

Diagnostics are necessary e.g. to identify the relevant subprocesses during laser processing and to validate the models.

Electrodynamics to describe the propagation of light (even through free boundaries)Effects: Diffraction, Reflection, Wave guiding.

Mathematics and Numerics: Additional to physical parameters, numerical parameters exist, that influence the solution of simulation. You have to know mathematics and simulation to distinguish between physical and numerical phenomena.

Thermomechanics: Heating of workpieces

Gasdynamics: Gas jets are important tools in laser processing (e.g. to blow out the melt during cutting). You need gas dynamics to know the influences of gas jet to e.g. the shape of the cutting front or to the melt blow out

Kinetics: Another gas that has to be considered is the vapour of the material. At the moment, we have to deal with evaporation, the continuum physical description of the processes is not sufficient. At the transition between liquid and gaseous phase, we have to consider the kinetics of single gas and liquid molecules and their interaction (collisions).

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For cutting with 1 - radiation you can see waves of melt on the cutting front in simulations and experiments (middle and left). Parts of the melt solidify at the cutting front and causes high surface roughness.At cutting with 10 -radiation experiments show, that the melt flow is nearly stationary.

For diagnosis (left and right) half of the metal sheet is replaced by transparent material. This is a method to observe the cutting process.

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The quality of a cut with 1m-radiation is low because there is a very strong wavy motion in melt flow, that does not occur at cutting with 10m radiation

Contribution of Simulation is to consider Amplitude, Phase, Polarisation of the laser light to calculate the absorbed intensity on the cutting front.

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