MONITORING OF METAL-POWDER DIAMETER BY EDDY-CURRENT SENSOR

Metal Injection Molding (MIM) is a technology by which metal products of high density and complex shape can be mass produced in a cost-effec tive manner. The density and particle size of metal-powder throughout the compound must be monitored if uniform products are to be obtained. In this report we examine the applicability of eddy-current technique s to in-process monitoring of powder density and particle size. An edd y-current based monitoring system developed by the authors to measure metal-powder density is expanded for monitoring of metal-powder diamet er in metal compounds. Experimental sensor readings were gathered usin g three different metal powders with known particle sizes: aluminum-li thium alloy (AA8090), nickel-iron magnetic allay (PB-47) and stainless steel (SUS316L). Analysis of the data showed that the sensor output w as proportional to the powder diameter under wet conditions with therm oplastic binder of constant density, and that the sensitivity of the s ensor differed with the type of metal powder. The merit of this techni que is its reliance on a simple and inexpensive sensor probe.