An experimental study on the surface mechanisms formation during the laser milling of PMMA

Laser milling is a recent technology adopted in rapid prototyping to produce tools, molds, and polymer-based microfluidic devices. In this process, a laser beam is used to machine a solid bulk, filling the area to be machined with a number of closely spaced parallel lines. Compared to traditional machining, this method has some advantages, such as: greater flexibility of use, no mechanical contact with the surface, reduction of industrial effluents, fine machining accuracy even with complex forms, and the possibility to work different kinds of materials. In the present article, an experimental study on poly-methyl-methacrylate (PMMA) laser milling is carried out with the aim to study the influence of the process parameters on the removed volume, depth and roughness. Laser milling tests were performed on a PMMA plate, using a 30 W CO2 laser source working in continuous wave or pulsed wave mode. To estimate the depth and the roughness of the milled pockets, a semi-empirical model, based on energy considerations, was developed. The results showed a good agreement between the model and the experimental data. However, the results clearly show that the mechanisms of interaction change considerably in dependence of the processing parameters.