Northwestern University Robert R. McCormick School of Engineering and Applied Science

Advanced Manufacturing Processes Laboratory

MRI: ARPI - Additive Rapid Prototyping Instrument


The Additive Rapid Prototyping Instrument (ARPI) would allow a more versatile production method that can utilize two families of processes: laser engineered net shaping (LENS) and Selective Laser Sintering (SLS). This makes the machine especially valuable for research and prototyping since it allows the rapid creation of different complex metal designs. Having both processes in one machine eliminates the need for multiple machines to create different products. The ARPI can be adjusted to manufacture different finished products within volume constraints.


The ARPI machine’s unique selling point is its ability to combine an additive-type process with the benefits of a secondary surface operation at the micro-scale. An in-situ metrology will also be incorporated into the machine in order to characterize parts as they are built, to be able to self-correct build quality via changing process parameters. A schematic of ARPI’s capabilities is shown in the image below:

Schematic of ARPI’s capabilities

The ARPI will be capable of performing two types of additive manufacturing processes, both of which are laser-based. One of these is the SLS process, which deposits a layer of metal powder and uses a laser to melt that layer into its desired form. The other is the LENS process, which deposits a very small amount of metal powder and uses a laser to melt that bit of powder. We aim to have the ARPI to be able to switch easily between these two processes with only minor modifications to the machine for each one. Similarly, the ARPI machine incorporates several secondary-processing and metrology techniques as well. An image of the new test-bed is shown below:

ARPI test-bed



National Science Foundation (CMMI-1429658)