3D Modeling & Design

Moira’s large back piece (I couldn’t find an official name for it, so I’ve been calling it the “biotic reactor”) was by far the most complex part of this costume and required extensive engineering design.

Using Autodesk Fusion 360, the original game model was imported as a sketching base and the bodies were constructed mostly in the sculpt workspace. The model was then split into several different components and tweaked to serve several purposes:

• Simpler finishing and painting (minimizing the need to mask)

• Considerations for rigging and stability when worn on the back

• Re-proportioning and reshaping certain pieces to scale to my body’s dimensions (the back plates in particular)

• Provide space for electronics and vinyl tubing

• Separating parts that would be resin cast (everything in purple, minus the tubes)

• Separation of major component sections for ease of disassembly and reassembly for travel

Component Sections

Reactor Shield

This is the topmost portion of the reactor. It is hollow and attaches to the Brain section with machine screws, using heat-set threaded inserts. The top silver plate separates to allow access to the screws for assembly and installation of the Neopixel rings beneath the lighted circles.

Each of the lighted circles is comprised of five pieces - all originally 3D printed, the two rendered in purple are then resin cast to function as diffusion filters.

Reactor Brain

This is the electronics hub of the piece, inside which Arduino microcontrollers are housed. It is hollow and attaches to the Shield and Bell sections with machine screws using heat-set threaded inserts. It has a back plate that allows wide access to the internals, allowing enough space to install the microcontrollers and associated wiring. It also has openings for inserting the top of the two large vinyl tubes, held in place through snug form-fit.

The only lighted portions on this section are the small piston-like bits on the front. One Neopixel is mounted inside each piston and diffuses out through the purple resin-cast diffusion filters. The pistons are affixed with magnets on the alignment pegs.

Reactor Bell

The bell is the structural core upon the other portions sit and where the rigging harness is attached. The Brain section attaches to the top of the back plate with machine screws using heat-set threaded inserts. The same method is used to attach most of the components through the entire column on this piece. A single pillar runs through the entire bell, screwing into the bottom circular plate and into the top back plate. All of the other pieces are sandwiched in between. Neopixel strips are wound around and wired through the hollow pillar, then fed up into the Brain via the back plate. Additional Neopixels illuminate the thin purple trim, to make it brighter and have a steady glow, whereas the the glassy lower portion has a pulsing light effect. These are wired into the Brain through the black tube. The bottom of the vinyl tubes sit in the lower curved cylinder. This piece has pegs that sit into the middle back plate and attach with machine screws. The middle plate, in turn, attaches to the upper back plate with machine screws. The lower back plate articulates with the curve of my back and is attached to the middle plate with a small hinge.

The glassy bell at the bottom was 3D printed, finished to a perfect mirror gloss on the outside, and 400-grit polish on the inside. It was then molded and cast with clear epoxy resin. The result is a clear, flawless glass effect on the outer surface, but a cloudy inner surface for diffusing the LEDs. The purple trim in the middle and small trim bits on the bottom were also resin cast as diffusion filters in the standard method.

Tube Fixtures

Miscellaneous pieces affix to the large vinyl tubes via a snug friction fit, with no direct attachment to the tubes themselves. The vinyl tubes were heat-shaped as much as they allowed, but still needed to be bent to fit. As such, they are under some tension when fit into these pieces. With this in mind, the tube fixtures that are affixed to the reactor itself were strongly reinforced at their connection to the reactor. The top cylinder is super-glued with a large surface area contact point, and the lower fixtures are attached with multiple screws. The front “valve” and ring fixtures have no load on them and sit on the tubes as decorative features.

3D Printing & Fixture/Rigging Installation

All components were 3D printed in PLA plastic. Threaded inserts and magnets were then installed and all pieces were assembled to test fit and stability.

The heat-set threaded inserts are small metal bits that fit over a special soldering attachment. When heated with the soldering iron, they are set into the PLA plastic, melting it as it inserts. The iron is then removed and the PLA solidifies around the inserts, fusing them into place. This method is ideal for screws that are intended to be frequently removed and replaced since it doesn’t degrade the plastic with frequent screwing (as would happen with screws self-threaded into bare plastic directly). These are ideal fixtures for a strong, removable bond in a large piece that needs to be frequently disassembled for transport.

The magnets are all neodymium, ensuring a strong hold where used. Magnets are only used for affixing non-load-bearing pieces that need to be removable but where it is difficult to fit a screwdriver.

This entire piece sits on the back, so the most convenient way to rig and strap this was to start with a regular backpack. The pack portion was cut away, leaving the arm straps and cloth back only (the “harness”). Reinforced slits were cut into the back and nylon heavy webbing straps were woven through. Heavy-duty snaps were also installed to double-secure these straps. The inside of the back plate has thin slits built into the model, through which the nylon cords are woven, then back out through the cloth. This firmly affixes the harness to the top back plate, and pulling on the nylon straps tightens the connection. Parachute buckles were attached to the free end of these straps, and they wrap around the torso and clasp in front. So all-told, this harness is comprised of four straps - the two initial arm straps from the original backpack, and two nylon straps attached directly to the Reactor.

Resin Casting

All of the purple bodies in the model needed to be able to transmit and diffuse light evenly.

After 3D printing and fully finishing the surface to a 400 grit smoothness, they were molded with silicone rubber (Smooth-On Mold Start 20T). They were then resin cast under pressure with Smooth-On Smooth-Cast 325 with a very small amount of So-Strong white. The opaque white allows the piece to uniformly diffuse LED backlighting, and the pressure cast ensures that the resin is bubble-free

The glassy bell at the bottom was first 3D printed then finished to a perfect mirror gloss on the outside, with a 400-grit polish on the inside. It was then molded and pressure cast with clear epoxy resin. The result was a clear, flawless glass effect on the outer surface, but a cloudy inner surface for diffusing the LEDs

Finishing

All 3D printed parts were finished using this method:

• 220 grit light pre-sanding/scuffing

• XTC-3D double layer

  • First layer ultra-thin

  • When tacky-cure, apply another thin glossy layer

• 400 grit full surface sanding

Painting

The black gloss surfaces were all airbrushed using this process:

• 3 coats Vallejo Gloss Black primer (74.660) with Airbrush Flow Improver (71.562)

• 2 coats Vallejo Model Air NATO Black (71.251)

  • If there is a red accent on the black, let the black dry overnight then:

  • Mask the accent shape

  • 2 coats Vallejo Model Air White (71.001)

  • 2 coats Vallejo Model Air Rot Red RLM23 (71.003)

• Allow the acrylics to fully dry (at least 24 h)

• 3 coats Rustoleum Gloss Clear

The metal surfaces were all airbrushed using this process:

• 3 coats Vallejo Gloss Black Primer (74.660) with Airbrush Flow Improver (71.562)

• 2 fine dust coats of Vallejo Metal Color Aluminium (77.701)

Electronics

The LEDs are all RGB-programmable LEDs (Neopixels), controlled with an Arduino microcontroller (Adafruit ItsyBitsy). 144 LED/m strips were used on in the Bell section, and two 16-pixel rings were used in the the Shield section.

For the details on the LEDs and electronics installation & programming, see the Electronics page.

Tubing

See the Tubes page for details.