— Materials

Aluminium 7075 or MJF polymer — our trade-offs

March 202614 min readby C. Aubry

The mass of an NVG housing is first and foremost a story of materials. For the LAB-NVS, we balanced two families — printed polyamide and aerospace aluminum — and chose to combine them by zone. Here's why.

MJF PA12 — sintered polyamide

Polyamide 12 printed in Multi-Jet Fusion is today our material of choice for the pods and structural pieces. Why:

Lightness — density 1.01 g/cm³, 2.7× lighter than aluminum.
Near-perfect isotropy — unlike FDM, MJF has no weak layers. The part behaves as a homogeneous solid.
Mechanical strength— tensile strength around 48 MPa, elongation > 12%. Well above what a MIL-STD-810H drop test requires.
Precision — ±0.3 mm tolerances on critical dimensions, more than enough for assemblies where steel axles carry the constraints.

7075 aluminium — for critical zones

7075-T6 is the historical aerospace alloy — used on aircraft wing structures since the 1960s. We use it in three zones:

Mounting interface (mount → housing)
IPD knob and secondary axles
Bridge screw anchor points

Where polyamide would creep under repeated clamping or wear in sliding, anodised 7075 holds. The cost: ~85 g of aluminum per binocular if used everywhere. Too heavy. The rule is simple: aluminum at the interfaces, MJF everywhere else.

The material we ruled out

We tested Grade 5 titanium(Ti-6Al-4V) printed via SLM. Excellent at every point — but unit price was 8× MJF for a strength gain that's only relevant in extreme environments (temperatures > 100°C, ballistic shock). Out of scope for standard MIL-STD-810H.

We also ruled out moulded carbon fibre (CFRP): pronounced anisotropy, fragility against point impacts, prohibitive tooling cost for Silicate volumes.

Why not metal everywhere

That's the recurring question. Answer: because the mass criterion is binding. An all-aluminium LAB-NVS would weigh ~310 g bare housing — three and a half times the current weight. We could do it, but we'd lose the «90 g bare housing» signature, which is precisely the central trade-off of the architecture.