An experimental investigation on accuracy of Hausner Ratio and Carr Index of powders in additive manufacturing processes

Powder based additive manufacturing processes are the most reliable and widely used additive manufacturing processes of present era. Among other parameters, flow of powders within these processes play a critical role in obtaining desirable characteristics of end products. Two most significant parameters which define the flow of powders in additive manufacturing processes are Hausner Ratio and Carr Index. Both Hausner Ratio and Carr Index are theoretically calculated so their numerical values represent the flow character of powders. Since Hausner Ratio and Carr Index are not intrinsic properties of powders therefore an argument exists on their accuracy to determine the powder flow. In this research, an experimental setup is organized to validate the accuracy of Hausner Ratio and Carr Index. The setup consists of a system comprising of three identical powder housing chambers each integrated with a DC servo motor. The speed of motors is controlled by LABVIEW graphical user interface. Three powder lots with similar morphology were used with each having average particle size (d₅₀) equal to 25 µm, 75 µm and 150 µm respectively. The actual flow of powder lots was obtained by using the experimental setup. Results of actual flow were compared with Hausner Ratio and Carr Index of respective powder lots. The effect of particle size distribution on flowability of powders is also discussed.