Clad height control in laser solid freeform fabrication using a feedforward PID controller

Environmental comparison of MESO-CLAD® process and conventional machining implementing life cycle assessment

“…Owing to this PCE, which take powder recycling rate into account, both surface roughness and processing time are improved and production velocity reaches values ranging from 2 to 10 cm 3 h À1 . For comparison, the most efficient technologies at the present time have a PCE of 20% (without taking account of powder recycling rate), which corresponds to a production velocity ranging from 0.6 to 3 cm 3 h À1 (Lin and Steen, 1998;Fathi et al, 2007). All energy consumption data during the process are tabulated in Table 2.…”

A camera based feedback control strategy for the laser cladding process

“…Closed loop control well maintained the height of the layer in case of changes in the absorption of the base material. Fathi et al (2007) developed a feedforward PID controller based on a semi-empirical nonlinear model to control the clad height. They controlled the cladding speed to obtain the desired clad height, while maintaining the laser power and powder feed rate constant.…”

A survey of sensing and control systems for machine and process monitoring of directed-energy, metal-based additive manufacturing

“…Taking advantage of variations in intensity of each spectral range with working distance, due to chromatic distortions, they designed a height control system and coupled it with a laser-power controller based on pyrometer measurements of melt pool temperature. Fathi et al (2006) utilized a more conventional, charge-coupled device (CCD) imaging sensors to assess the influence of various process conditions on deposition height, and then utilized system identification techniques to determine a dynamic system model. With this, they were able to construct PID controllers both with and without an additional feedforward term (based on the identified system dynamics).…”