Motivation

The SLS process is greatly affected by uncertainty sources that are aleatoric in nature and which ultimately contribute tremendously to the quality of the printed part. In this study the aim is to quantify the amount of uncertainty that arises from printing a SS 316L part via the SLS process. The SLS process consists of using a thin laser that scans the top of a bed of powdered material in order to melt and consolidate local powdered material and ultimately print a part layer-by-layer. Uncertainty in the amount and shape of the material that melts and consolidates arises from the random arrangement and the size of the particles in the powder layer. It is the local arrangement and the size of the particles that empirically affects the amount of laser energy that is locally absorbed by the material and that ultimately permeates the powder layer into the underlying, previously-solidified material substrate.

Method & Results

A single track of the laser scan path is simulated and the thermal equation is solved by leveraging a coupled finite difference – discrete element method by Ganeriwala and Zohdi. The method is enhanced by computing a local effective powder layer thickness at each voxel, thus capturing a stochastic effect on the local absorbed laser energy based on the random nature of the arrangement and size of the particles. The solution of this simulation is to be used in a downstream step for capturing and analyzing the size of the material melt pool, both in space and in time, for measuring the variation of the shape of the melt pool.

The video above shows a simulation where a laser scans the top of the domain in the +x direction. On the top-right corner we see that an x-z cross section has been taken to provide a better visualization of the thermal field into the substrate. A top view is also provided on the bottom portion of the video pane.