Adaptive tape placement process control at geometrically changing substrates

The laser-assisted tape placement process faces thermal challenges at geometrically changing substrates. Due to changing optical conditions and thereby varying local energy absorption, local differences of the process temperature occur. These temperature inhomogeneities become even more pronounced due to restrictions with regard to machine dynamics. In particular, strong directional changes, which are necessary e.g. for small machining radii, result in the relative speed between workpiece and laser beam not being constant. The use of vertical-cavity surface-emitting lasers (short: VCSEL) as adaptive heat sources could improve the temperature control especially by use of application adapted intensity distributions that can be calculated through inverse simulations. In this work, the optical and thermal effects during tape placement on geometrically changing substrates are described and analyzed. A possible solution to the described challenges is shown by using application adapted intensity distributions, which aim at a suitable, constant process temperature. The simulations will consider the three-dimensional part geometry, specific intensity distributions of the VCSEL as well as machine dynamics. By the use of tape placement equipment of the Fraunhofer IPT the occurring local temperature changes and the resulting degree of process optimization are experimentally validated.