Control of the removal rate in laser chemical machining

An important challenge for all processes based on laser material removal is the control of the precision of the shape. This is so, because all methods are non-contact methods and the removal rate underlies certain influences depending on the exact processing conditions and material properties, making only limited prediction and control of the removal rate possible. In laser chemical machining the radiation locally initiates on a metal surface a thermo chemical etching reaction, which leads to selective material removal at high resolution. To achieve an intensive mass transport and also cooling of the work piece the etch liquid is injected co-axially to the laser beam directly into the irradiated area. Measurements of the electrochemical potential against a reference electrode show a cathodic shift of the potential as a function of laser power and feed rate while processing. These functional dependencies of the chemical potential on the processing parameters can be used to control the temperature driven reaction and therefore the removal rate, as the chemical potential can be more easily and instantaneously measured than the temperature.