Metal Components for Drones and Unmanned Vehicles
Aerial, ground and marine drones are built from light metal parts that must survive vibration, heat, dirt and water, and be identical from one unit to the next. Eurobalt produces these parts to customer drawings: die-cast housings for electronics, machined mounts and shafts, sintered and MIM gears for drives, and shock absorber components for suspensions and landing gear.
Unmanned vehicles now cover very different machines. Multirotors inspect power lines and map building sites, agricultural drones spray fields, fixed-wing and VTOL aircraft survey long corridors, wheeled and tracked robots carry loads across farms and warehouses, and surface and underwater drones measure harbours and pipelines. The electronics and software differ from one type to the next. The metal parts that hold these machines together have a lot in common.
Every gram counts on an aircraft and on a battery-powered robot. Motors and rotors send vibration through every joint. Motor controllers and power modules need their heat taken away. Ground and marine drones work in dust, mud and salt water. When an airframe goes into series production, the hundredth unit has to receive the same part as the first one.
This article goes through the assemblies of an unmanned vehicle and shows which manufacturing process suits each of them. All parts are made to the customer’s drawing or 3D model.
Where Metal Parts Sit in an Unmanned Vehicle
| Assembly | Typical metal parts | Process |
|---|---|---|
| Airframe and mounts | Motor mounts, arm-folding joints, wing-joint plates, landing-gear brackets | CNC machining in aluminium, stainless steel, titanium |
| Electronics and power | Housings for flight controllers, motor controllers, power modules and radio units | Aluminium die casting; zinc for small shells |
| Drives and mechanisms | Gears for gearboxes, pumps and winches, rotors and shafts, latches and small levers | Powder metallurgy, metal injection molding |
| Suspension and landing gear | Pistons, base valves, rod guides and piston rods of shock absorbers | CNC machining, sintering, induction hardening and hard chrome |
| Ground drive | Wheel hubs, shafts, sprockets, gearbox housings | CNC machining, die casting, powder metallurgy |
| Marine and underwater | Housings, shafts and fittings in stainless steel | CNC machining in SS316 |
Light Housings for Electronics: Die Casting
A drone carries its flight controller, motor controllers, power distribution and radio in small enclosed housings. High-pressure die casting in aluminium forms such a housing complete with cooling fins, internal ribs, threaded bosses and cable ports in one cycle measured in seconds. Aluminium die-casting alloys conduct heat at about 90 to 155 W/(m·K), so the housing wall itself works as the heat sink of a motor controller or a power module.
A cast aluminium housing is also a shield. With cast-in mating surfaces and chromated grounding pads it screens the electronics against electromagnetic interference, which matters on a drone where the radio link and the satellite receiver sit a few centimetres from switching power electronics.
The alloy is chosen by heat load, corrosion exposure and finish:
| Alloy | Density | Thermal conductivity | Suits |
|---|---|---|---|
| EN AC-47100 / ADC12 | ~2.74 g/cm³ | ~92 W/(m·K) | Thin-wall electronics housings in high volume |
| EN AC-43400 / AlSi10Mg(Fe) | ~2.65 g/cm³ | ~140 W/(m·K) | Heat-loaded housings of controllers and drives |
| EN AC-44300 / AlSi12(Fe) | ~2.65 g/cm³ | ~155 W/(m·K) | Sealed housings exposed to water and spray |
| Zamak 3 / Zamak 5 | ~6.6 g/cm³ | ~110 W/(m·K) | Small precision shells and connector bodies |
- Walls: 1.5 to 4 mm on production parts, down to 1.0 mm in local zones, with draft angles of 0.5° to 3°.
- Sealing: gasket grooves and machined mating surfaces for IP54 up to IP67, which covers drones that fly in rain and robots that are washed down after work.
- Finishing: shot blasting, chromate conversion coating, powder coating in any RAL colour, e-coating. Anodizing is possible, but silicon-rich die-casting alloys give a darker, less even film. Of the alloys above, AlSi10Mg gives the most predictable result.
- Machining after casting: flange faces, threads, connector openings and bearing bores are machined to drawing tolerance.
Zinc is the most fluid die-casting alloy. It fills the thinnest walls and the finest details and needs little or no machining afterwards, and a die for zinc lasts up to ten times longer than a die for aluminium. Zinc is heavy, so on a drone it makes sense for small parts: connector shells, latch bodies and small precision housings. Where the weight target is tighter, the same workshop casts housings in magnesium AZ91D.
Machined Airframe and Drive Parts
Structural parts of an airframe are usually machined. Motor mounts, arm-folding joints, wing-joint plates and landing-gear brackets carry thrust, landing loads and constant vibration, and their mounting faces and bores decide whether the joint stays tight. On CNC turning and milling centres we machine these parts from aluminium alloys, stainless steel SS316 and titanium, and check critical dimensions on a Mitutoyo CMM. The same applies to the metal parts of brushless drone motors: motor bells, rotor end caps and motor bases with a mounting flange are turned and milled from aluminium and anodized black, natural or in colour.
EN AW 6082-T6 is a common choice for light, loaded parts. It combines high strength with good machinability and corrosion resistance, and anodizing adds a hard, protective surface. We used it for the lightweight shock absorber pistons described below, with ±0.05 mm on critical diameters and a 20 µm anodic layer.
On ground robots the same machining line produces wheel hubs, drive shafts, sprockets and brackets for manipulators. On marine drones stainless SS316 is the usual choice for thruster housings, shafts and fittings that stay in salt water.
Sintered Gears, Rotors and MIM Parts for Drives
Wheel-motor gearboxes of ground robots, winches of cargo drones, pumps of agricultural sprayers and servo actuators all run on small gears. In series these gears are pressed and sintered. The powder is compacted at 400 to 800 MPa in a die that forms the tooth profile, the bore and other features in one stroke, and sintering bonds the particles in a controlled-atmosphere furnace. Material grades of our PM gears follow ISO 5755.
- Accuracy: IT8-IT9 directly after sintering, so most secondary machining disappears.
- Material use: the part is formed almost to its final contour, and metal losses stay at 3 to 5%.
- Cost: on medium and large series the saving reaches 30 to 40% of total production cost.
- Noise: the residual porosity of a sintered gear damps vibration and makes a small drive run quieter.
The same process makes rotors, splined shafts and shafts with integrated gear crowns. In one recent project we produced more than 5,000 such rotors and shafts for a European manufacturer of special equipment.
Metal injection molding covers the smaller and more complex parts: bearing retainers and shaft collars, positioning sleeves, standoffs and threaded inserts, landing-gear hinge blocks, lock blocks and pivot pins, latches of folding arms and small gears with integrated hubs. We produce MIM parts up to 453 grams at a density of 99.5%. The part shrinks by roughly 15 to 20% during sintering, so the mould is made oversize, and before tooling we check even wall thickness, datums for the holes and large flat areas that could warp.
Our article on powder metallurgy standards explains how the process is standardised and where it is already used in light aviation and drones.
Shock Absorbers for Ground Robots and Landing Gear
Wheeled and tracked robots that drive over fields, construction sites and uneven yards need suspension, and heavy multirotors and VTOL aircraft often land on damped landing gear. A damper on an unmanned vehicle is close in size and load to the shock absorbers of motorcycles and ATVs, and we have produced parts for those for many years.
- Pistons: machined from EN AW 6082-T6 for light weight, with ±0.05 mm on critical diameters, an ultra-thin bleed hole, a 20 µm anodic layer and PTFE sealing tape, each checked by a leak test. Sintered steel pistons are the choice for high volumes.
- Base valves and rod guides: sintered to complex shapes and kept dimensionally stable from batch to batch, machined where pressing alone cannot reach the final geometry. They can be supplied with PTFE bushings and PTFE tape, ready for assembly.
- Piston rods: Ø8 to 50 mm and 150 to 1500 mm long, induction hardened on the running surface, straightened and finished with 20 to 30 µm of hard chrome to Ra ≤ 0.2 µm, or with a black QPQ finish. For weight-optimised dampers the rod is gun-drilled hollow, with the bore concentric to the outer surface within 0.05 mm over 600 mm. Smaller diameters are possible with dedicated tooling.
A hard, smooth rod surface matters even more on a ground robot than on a road vehicle, because dust and dried mud are exactly what wear out a rod without a hard coating, and its seal with it. Our production capacity allows up to 200,000 additional shock absorber parts per month. More detail is in our articles on lightweight pistons for motorcycle shock absorbers and piston rods for shock absorbers.
Quality for Series Production
A drone programme that moves from a few prototypes to a production series needs the same part in every airframe. Our quality control runs on three levels: at the factory according to internal standards, by an expert from our head office, and, by prior arrangement with the customer, by independent organisations such as SGS. Depending on the part, the inspection plan includes:
- CMM measurement of the first article and periodic batch control;
- X-ray inspection of castings for porosity in pressure-tight or load-bearing zones;
- leak testing of sealed housings and damper parts;
- coating thickness checks for anodizing and chrome;
- material certificates to EN 10204 3.1 on request.
Our quality management system is certified to ISO 9001.
About Eurobalt
Eurobalt is an industrial group with its head office in Tallinn, Estonia, and branch offices in Latvia and Serbia. The parts described above are made at our own production facilities by die casting, CNC machining, powder metallurgy and MIM, casting and forging, and each facility has its own quality control laboratory. Our R&D engineers adapt drawings and 3D models to the chosen process before tooling is ordered. Quality is checked at every production stage, to PPAP or to the customer’s own requirements. We have long supplied parts to makers of agricultural machinery, to automotive and consumer electronics companies and to manufacturers of LED lighting for airports. Read more about Eurobalt.
Technology pages: die casting · powder metallurgy and MIM · CNC machining · shock absorber parts
