The Challenge
A Bengaluru-based satellite sub-system integrator was designing a deployment mechanism bracket for a Ka-band antenna on a small observation satellite. The programme had a strict mass budget: the bracket assembly (bracket + interface fasteners) could not exceed 210 grams. The machined aluminium 6061-T6 baseline design weighed 342 grams — 63% over budget.
The team had explored conventional lightweighting approaches: pocketing, wall thinning, material removal on non-load-bearing faces. These changes brought the bracket to 285 grams — still 36% over budget and structurally marginal at the thinnest wall sections. They contacted Layer X in Ahmedabad for a topology optimisation and DMLS additive manufacturing assessment.
Technical Requirements
- Material: Aerospace-grade aluminium, compatible with space environment (thermal cycling −60°C to +120°C, vacuum outgassing)
- Structural: 5g quasi-static launch load, 50g shock, 20–2000 Hz random vibration per ECSS-E-ST-32 equivalent
- Target mass: ≤210 g (bracket only, excluding fasteners)
- Interface: Must accept 6× M4 inserts for antenna deployment mechanism and 4× M5 inserts for satellite panel attachment
- Surface treatment: Alodine or equivalent for ESD/EMC compliance
- Certification: Full dimensional report, material test report, hardness certificate
Engineering Approach
Step 1: Load Case Definition and FEA Baseline
Layer X's engineering team built a finite element model in Altair Inspire from the customer's interface envelope drawing. Three load cases were defined: 5g static (launch quasi-static), 50g shock (pyrotechnic separation), and self-weight + inertia under 20–2000 Hz random vibration. The machined 6061-T6 baseline was analysed first to establish stress distribution and identify load-carrying regions — these would be protected in the topology optimisation.
Step 2: Topology Optimisation
Altair Inspire topology optimisation was run with:
- Design space: full bracket volume minus excluded regions (interface boss areas, M4/M5 clearance zones)
- Objective: minimise compliance (maximise stiffness) under all three load cases simultaneously
- Volume constraint: 45% material retention (targeting 154 grams from full-volume 342 gram baseline)
- Manufacturing constraint: overhang angle ≥ 45° for DMLS printability
The topology optimisation converged in 4 hours on cloud compute, producing a result with 47% volume retention (160 gram equivalent) showing clear load paths — two primary arched ribs connecting the antenna interface to the panel attachment, with organic web geometry between them.
Step 3: Geometry Reconstruction
The raw topology mesh was re-surfaced by the Layer X engineering team into a smooth NURBS body using Fusion 360. Minimum wall thickness was enforced at 0.8 mm (DMLS AlSi10Mg minimum). Radii were added at all stress concentration points. M4 and M5 boss inserts were modelled as cylindrical posts with locking geometry for heat-set insert installation.
The reconstructed model was validated by re-running the FEA on the final geometry — maximum Von Mises stress under all load cases remained below 0.6× yield strength (safety factor > 1.67 on yield). First natural frequency: 847 Hz (above the programme requirement of 100 Hz minimum).
Step 4: DMLS Build and Post-Processing
AlSi10Mg was selected over cast aluminium for its superior specific strength after T6 heat treatment and the ability to achieve complex topology-optimised geometry. Build time: 7.5 hours for two brackets (flight unit + acceptance test unit). Post-processing:
- T6 heat treatment (solution anneal 520°C, 1h + artificial age 160°C, 12h)
- Support removal and cleanup
- CNC machining of all interface faces to drawing tolerances
- Chromate conversion coating (Alodine 1200) for ESD/EMC compliance and corrosion protection
- CMM inspection — all 22 critical dimensions within drawing tolerance
Results
| Metric | Baseline (machined Al 6061) | DMLS AlSi10Mg (topology optimised) |
|---|---|---|
| Mass | 342 g | 212 g (38% reduction) |
| First natural frequency | 312 Hz | 847 Hz (+171%) |
| Max stress (5g quasi-static) | 128 MPa | 156 MPa (still within yield limit) |
| Lead time | 4 weeks (machining from billet) | 3 weeks (DfAM + build + post-process) |
| Cost | ₹38,000 (machined 6061) | ₹52,000 (DMLS AlSi10Mg + T6 + Alodine) |
The bracket met the 210 gram mass budget (212 grams — 2 grams over, accepted by programme change request), passed all structural qualification tests, and was integrated into the satellite sub-system. The first natural frequency improvement to 847 Hz was a significant structural benefit that also emerged from the topology optimisation.
Key Learnings
For space applications where every gram counts and geometry freedom is the primary design driver, DMLS with topology optimisation delivers results that machining cannot match. The cost premium (37% more expensive than machined 6061) is justified by the 38% mass saving — at ₹50,000–1,00,000 per kilogram of launch cost, saving 130 grams on a satellite structure has a direct ROI in the tens of thousands of dollars.
Contact Layer X for aerospace-grade DMLS AlSi10Mg parts with DfAM engineering support, material certification, and CMM inspection reports.