This Project has been supported by the National Science Foundation Grant Number 1343480.
Since the mid-1980s, Selective Laser Sintering has been utilized as a prominent additive manufacturing technology to meet the needs associated with obtaining 3D parts. However, as the search for faster printed parts with higher resolution increased, an alternative cost-efficient process was desired to meet such demands. With all in mind, Behrokh Khoshnevis invented the Selective Inhibition Sintering process for metals.
HOW IT WORKS
An SIS-Metal process has been developed based on microscopic mechanical inhibition. In this process, the inhibitor (typically a ceramic salt or carbohydrate solution) is printed in selected areas of each metal powder layer. The active ingredient (salt or carbohydrate) re-crystallizes when water evaporates under moderate heat. Later, during bulk sintering, it decomposes to second phase metal oxide or carbon. The decomposed solid particles cover the surface of affected metal powder particles and exert a retarding force which inhibits sintering. The SIS-Metal process has numerous advantages including: reduced costs in equipment when compared to similarly capable technologies such as Selective Laser Sintering (SLS), increased speed/efficiency as the entire layer is sintered at once and inhibitor need only to be deposited at the periphery of the part, high dimensional accuracy and surface quality, multi-color part fabrication with the use of a commercial inkjet print head, no contamination of parts, materials or furnaces and a great potential of building large parts.
Step 1: A thin layer of metal powder is spread over the build tank.
Step 2: Inhibitor is deposited along the layer profile with a small-orifice nozzle or inkjet print head.
- Repeat Steps 1,2 until the entire part has been completed.
Step 3: The part is bulk sintered in a conventional sintering oven under appropriate atmosphere.
Step 4: The inhibited regions are removed, revealing the desired part and its negative.