Additive manufacturing (AM, also informally known as 3D printing) is a relatively new process for fabricating net- shaped parts from a computer-generated drawing. The inherent problem with using AM in mass production is the slow build times for each part. Because parts must be built layer by layer, the build time cannot be dramatically increased. The build time is limited by the physical melting and consolidation of plastic or metal, which cannot be dramatically speeded up, and the velocity of the build head, which is limited by the mechanical motion mechanism. One solution to the inherently slow build times is to replicate the building head, while replicating as few of the other machine components as possible. Utilizing this technique, the fabrication time per part can be reduced by the number of simultaneous building heads, which may make the AM process suitable for some mass production.

(a) Schematic of a laser-deposition additive manufacturing build head fabricating a metal valve stem. This component takes over six hours to build. (b) By adding an array of deposition heads using multiple lasers, several parts can be built simultaneously without having to significantly modify the other components of the machine. In this schematic, each build head has its own melting laser (200 W) while the feedstock powder is delivered to each build head from a central source. (c) An example of how the array process can be used in a simple modification of a commercially available polymer 3D printer. By using multiple build heads (which are already included on many models to print support material and different colors), several identical parts can be made simultaneously. The build time for the part is 2.5 hours, which is reduced to 38 minutes per part if the array were used. Instead of using each head individually, the software can be modified to turn on all the heads at once.

This work was completed as part of the Models, Material and Manufacturing effort at JPL. (Schematics courtesy of Joanna Kolodziejska)

To accomplish rapid part production through AM, two or more building heads must be attached to the same x-y-z control, where the melting power and the feedstock material can be delivered to each head individually. This allows one machine to build multiple parts simultaneously without having to use a separate control system, frame, workpiece, enclosure, or feedstock delivery system for each part. Because the process for arraying one build head is far less expensive than using one AM machine for each part, this technique is extremely beneficial for expanding the uses of AM in commercial production, especially for parts with small base area, such as an automotive valve stem, for example.

Designing a mass-production AM machine requires two major factors. First, one must create a working array of multiple build heads to create simultaneously as many identical parts as possible in one manufacturing run. Because the build time for each part is fixed by the physics of deposition and volume of the part, an array is the only practical way to increase the building rate. This method is extremely useful for metal AM machines, such as direct metal laser sintering (DMLS), for example, since the feedstock material is a bed of powder and the only modification required for replicating the build head is additional melting lasers. The technique is also useful for polymer AM machines that are used for making components that cannot be injection-cast, as with complex parts like CubeSats, for example. Second, one must develop mass-production AM machines specifically designed for building a particular part. Depending on the parts being mass-produced, the AM equipment can be simplified and optimized to increase part production volume while decreasing cost. This can be done by eliminating unnecessary build volume, excess laser power (over what is needed for the build), or total x-y-z translation, for example.

This work was done by Douglas C. Hofmann and John Paul C. Borgonia of Caltech for NASA’s Jet Propulsion Laboratory. For more information, contact the inventors at This email address is being protected from spambots. You need JavaScript enabled to view it..

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management
JPL
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Refer to NPO-49022

NASA Tech Briefs Magazine

This article first appeared in the October, 2015 issue of NASA Tech Briefs Magazine.

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