Project

Microgravity Hybrid Extrusion

Copyright

Che-Wei Wang

Che-Wei Wang

Traditional additive manufacturing processes, especially those that make use of liquid resin as the feedstock, are constrained by the gravity environment on Earth. Gravity prevents extrusion into free space without sagging, which requires the use of support material to prevent. In a microgravity environment, extrusions into free space that would normally sag can proceed unimpeded, allowing for the creation of structures that could not be produced in a gravity environment.

We aim to demonstrate this using a hybrid extrusion process we developed, which can create 3D structures (such as coils) from feedstocks of flexible metal wire and photocurable resin, where the wire is bent into a 3D shape and evenly coated with the resin. Prior to resin curing, structures created with this process are weak, so in a gravity environment the structure will collapse or deform under its own weight. The resin is also free to flow and will end up not evenly coating the wire, pooling on the lower surface of the wire as well as beading up. In microgravity, we suspect that the structural deformation and resin pooling will not occur, but we are… View full description

Traditional additive manufacturing processes, especially those that make use of liquid resin as the feedstock, are constrained by the gravity environment on Earth. Gravity prevents extrusion into free space without sagging, which requires the use of support material to prevent. In a microgravity environment, extrusions into free space that would normally sag can proceed unimpeded, allowing for the creation of structures that could not be produced in a gravity environment.

We aim to demonstrate this using a hybrid extrusion process we developed, which can create 3D structures (such as coils) from feedstocks of flexible metal wire and photocurable resin, where the wire is bent into a 3D shape and evenly coated with the resin. Prior to resin curing, structures created with this process are weak, so in a gravity environment the structure will collapse or deform under its own weight. The resin is also free to flow and will end up not evenly coating the wire, pooling on the lower surface of the wire as well as beading up. In microgravity, we suspect that the structural deformation and resin pooling will not occur, but we are unsure how the resin beading will be affected.

Our experiment apparatus is designed to investigate the process described above. The apparatus uses two feedstocks: small-gauge flexible wire and a photocurable resin, and extrudes them both through a nozzle assembly which simultaneously bends the wire into a 3D shape and coats it with an even layer of the resin.

The wire bending process is similar to large scale commercial wire and tube bending machines: a feed mechanism pushes wire though the nozzle which is moved in the plane normal to the wire feed path. This creates a force on the wire, which plastically deforms it in a defined radius and direction. The motion of this system is controlled by a computer numerical control (CNC) system that uses predefined commands to create precise motion of the three axes.

Liquid resin is also fed into the nozzle where it evenly coats the wire as it exits. Just after the nozzle, an array of ultraviolet (UV) LED emitters are positioned to cure the resin, both hardening it and bonding it to the wire. After the entire shape is created, a cutting mechanism cleaves the coated wire just after the nozzle exit so that creation of another shape may proceed.

Copyright

Steve Boxall/ZERO-G

Copyright

Steve Boxall/ZERO-G