Thermal distribution control in scanned processing of materials

Scan thermal processing, enabled by guidance of the heat source trajectory during fabrication, combines the flexibility of sequential methods to the productivity of parallel processes. For cylindrically symmetric parts, this is performed by their rapid revolution under a radially or axially translated torch. The source power is modulated to implement a specified thermal distribution as it sweeps the product surface, and thus to generate desirable material features. An analytical description of the thermal field, based on superposition of Green's fields, is developed for off-line analysis. Also, a multivariable model with least-squares parameter identification, is introduced for real-time compensation of the process efficiency. This model is embedded to a thermal distribution control scheme, driving the scanned torch motion and power by a simulated annealing optimization strategy. This uses temperature feedback from random surface locations by an infrared pyrometer. The thermal regulator is validated computationally and experimentally, and its applicability to other scanned processes is examined.