Multivariate statistical process control of laser powder bed additive manufacturing

A method of multivariate statistical process control for a laser powder bed additive manufacturing process, comprising

• recording signals of a plurality of process parameters;
• building a solid three-dimensional object from the recorded process parameters;
• calculating, using a multivariate statistical process control method, a reduced variable set while building the three-dimensional object from the recorded process parameters, wherein the reduced variable set comprises one or more principal component variables, there being fewer principal component variables than the plurality of process parameters;
• returning a signal indicating whether the laser powder bed additive manufacturing process remains within statistical control based at least in part on the reduced variable set;
• and
• interrupting or stopping the laser powder bed additive manufacturing process if the signal indicated that the laser powder bed additive manufacturing process does not remain within statistical control.

A method of manufacturing a part by laser additive manufacturing comprising:

• (a) irradiating a layer of powder in a powder bed to form a fused region;
• (b) providing a subsequent layer of powder over the powder bed by passing a recoater arm over the powder bed from a first side of the powder bed;
• (c) repeating steps (a) and (b) to form the part in the powder bed;
• (d) while conducting steps (a) (c), recording, using one or more processors, signals of two or more process parameters the process parameters comprising laser power, laser power drive signal, x/y position of laser focus on build surface, laser scan speed, laser scan direction, on-axis electromagnetic emission from the melt pool, on-axis electromagnetic emission from the plasma, off-axis electromagnetic emission from melt pool, off-axis electromagnetic emission from plasma, incidence angle of laser relative to build surface, incidence angle of laser relative to workpiece, gas flow velocity, powder bed temperature, powder layer thickness, or the thermal conductive properties of workpiece below a given layer/location;
• (e) performing an orthogonal transformation to transform the two or more recorded signals into a reduced variable signal for the recorded process parameters, the reduced variable signal comprising one or more principal component variables, there being fewer principal component variables than the two or more recorded signals;
• (f) determining, by one or more processors, whether the reduced variable signal is within control limits for the process;
• and
• (g) interrupting or stopping the process, using one or more processors, when the reduced variable signal exceeds the control limits.