Date of Completion

Spring 5-22-2020

Project Advisor(s)

Chih-Jen Sung, Song Han, Tai-Hsi Fan, Horea T. Ilies

University Scholar Major

Mechanical Engineering


Acoustics, Dynamics, and Controls | Controls and Control Theory | Manufacturing | Mechanical Engineering


Selective laser sintering (SLS) is an additive manufacturing technique that involves using a laser to fuse powdered material together, layer by layer, in order to create a 3-D product. Despite its numerous benefits over traditional methods of manufacturing, including higher efficiency, versatility, and the ability to process many materials, selective laser sintering suffers from its propensity to generate structural errors during operation.

Feedback control has been shown to improve fabrication quality in other laser-based additive manufacturing techniques when implemented properly. Widespread exploration of applying feedback control in SLS might lead to significant performance improvements in this form of manufacturing.

This project covers the design of versatile feedback control system components for laser-based additive manufacturing machines to aid in the investigation of feedback control in SLS. Two separate SLS testbeds are used as platforms for development to verify that the components can be adapted for use across different machines. Adjustment capabilities are present to allow the investigation of different feedback control strategies and their impact on SLS manufacturing.

Among the components is a sensor consisting of a thermal camera and image analysis program. This sensor component gathers images during the manufacturing process. Properties, such as the size of target temperature regions, can be determined.

Measured values from the sensor are then sent to a controller component. The controller component can make use of any of these measurements as inputs for testing a wide range of different control strategies.

Two different plans for an actuator component are explored specific to the design of each SLS testbed. Both component plans are intended to impact fabrication quality by influencing laser energy density through adjusting a single laser parameter. On one machine, a component strategy is devised that enables laser scan speed adjustments during manufacturing. On the other machine, a modification is formulated that would allow continuous laser power adjustments during system operation. Both actuation plans work by taking advantage of the way each machine processes g-code. The presented actuation strategies require minimal machine hardware additions to implement.