Aluminium Die Casting for
Poultry Equipment Gearbox Housings

Gearbox housings used in poultry farming equipment — ventilation fans, feed conveyor drives, egg collection systems, and climate control units — operate in some of the most aggressive light-industrial environments a mechanical component can encounter. Airborne ammonia from litter breakdown attacks unprotected metal surfaces. Wash-down cycles with pressurised water and disinfectant chemicals are routine. Temperatures fluctuate between unheated winter conditions and humid summer heat loads.

At the same time, the dimensional requirements are unforgiving. Bearing bores must be held to H7 tolerance to prevent premature bearing failure. Gear cavity geometry must be accurate to maintain correct mesh. Mounting faces must be flat and square to prevent misalignment under load. And because poultry equipment is manufactured in high volumes — hundreds or thousands of units per batch — the casting process must deliver that consistency part after part, not just on the first article.

Cast iron was the default material for gearbox housings for decades. It handles the structural and damping requirements well. But at roughly 7.1 g/cm³, it is nearly three times heavier than aluminium. For equipment that is mounted overhead, moved frequently, or where weight reduction has a downstream energy cost, that difference is significant. Corrosion resistance is another weakness: uncoated cast iron rusts quickly in wet agricultural environments, requiring additional surface treatment that adds cost and process steps.

Aluminium die casting, specifically High Pressure Die Casting (HPDC) using ADC12 alloy, addresses both problems and adds further advantages that make it the preferred process for high-volume poultry gearbox housing production.

ADC12 (equivalent to A383 in the ASTM system) is the most widely used aluminium alloy in HPDC for industrial applications. Its composition — roughly 9.6–12% silicon, with copper and small additions of iron, manganese, and zinc — gives it a specific combination of properties that align well with gearbox housing requirements.

Castability. The elevated silicon content gives ADC12 excellent fluidity in the die, allowing it to fill complex cavity geometries including thin walls, deep pockets, and intersecting ribs. This matters for gearbox housings, which typically combine thick bearing bosses with thin web sections.

Machinability. Compared to A380, ADC12 machines more cleanly. Bearing bores, seal grooves, port threads, and mounting face surfaces are all finish-machined after casting, and ADC12 produces good surface finish at competitive tool life.

Dimensional stability. ADC12 has a low and predictable shrinkage rate in the die, which is essential for holding bearing bore location and gear cavity geometry consistently across a production run.

Corrosion resistance. Aluminium naturally forms a stable oxide layer that resists moisture and mild chemical exposure. With an additional powder coat or anodising treatment, ADC12 gearbox housings withstand agricultural wash-down environments without the rust risk of uncoated iron.

Weight. At 2.7 g/cm³, an ADC12 gearbox housing is approximately 60% lighter than an equivalent cast iron housing. For a typical poultry fan gearbox housing weighing 1.8 kg in iron, the aluminium equivalent comes in around 700 g.

The table below compares ADC12 against the other alloys and processes most often considered for gearbox housings.

Both processes can produce aluminium gearbox housings. The right choice depends on volume, geometry, and structural requirements.

HPDC injects molten metal into a hardened steel die at pressures between 700 and 1,500 bar. Cycle times are short — typically 30 to 90 seconds per shot — making it cost-effective from around 500 units per year upward. Wall thickness can go as low as 1.5mm, and dimensional repeatability is excellent. The rapid solidification under pressure can introduce micro-porosity in thick sections, which is relevant if the housing will be pressure-tight or welded, but for most gearbox housing applications this is not a constraint.

Gravity Die Casting (GDC) fills the die under gravity with no applied pressure. Solidification is slower, which produces a denser microstructure with better elongation and fatigue performance. This makes GDC the preferred process for structurally demanding housings at lower volumes — typically below 500 units per year. Wall thickness minimum is around 3mm. LM25 is the standard alloy for GDC gearbox housings where mechanical properties are the priority.

For most poultry equipment gearbox housings — produced at several hundred to several thousand units per year, with walls in the 3–6mm range — HPDC in ADC12 is the correct process.

Getting the part right starts at the design stage. Several geometry decisions made during CAD have a direct impact on casting quality, tooling cost, and post-cast machining.

Draft angles. External surfaces need a minimum 1° draft to allow ejection from the die without drag marks. Internal surfaces — gear cavities, bearing boss bores — need 1.5° to 2°. Insufficient draft is one of the most common causes of die wear and surface defects on gearbox housings.

Bearing bore approach. Bearing bores are cast with a 2–3mm pre-machine allowance and finish-bored on CNC to the required H7 tolerance after casting. Attempting to cast bearing bores to final tolerance is not reliable in HPDC. The bore location must be accurate in the die — typically held to ±0.15mm — so that the CNC operation has consistent material to remove.

Parting line location. The parting line position determines which surfaces are exposed to flash and which are tool-controlled. For gearbox housings, the parting line should be located away from bearing seats and gear mesh faces wherever possible.

Wall thickness transitions. Abrupt changes from thick to thin sections cause shrinkage defects. Gradual transitions with cored-out pockets or ribs distribute metal flow and reduce porosity risk in thick sections such as bearing bosses.

Seal grooves and mating faces. Mating faces that will carry O-ring seals or gaskets should be machined flat to Ra 1.6 µm or better. The casting should provide sufficient material at the mating face for a 0.3–0.5mm machining allowance without breaking into any core or internal feature.

SAPL supplies aluminium die cast gearbox housings to manufacturers in the agriculture and off-highway sector from our facility in Chakan MIDC, Pune. Our five fully-automatic HPDC machines span 180T to 450T clamping force, covering gearbox housing weights from under 200g to approximately 1.5 kg. ADC12 is one of our standard production alloys, alongside A380 and LM24.

Post-cast operations are completed in-house. Our CNC and VMC machining centre — 20+ machines including 4th-axis VMC capability — machines bearing bores to H7 tolerance, finishes mating faces, and completes thread operations. Tolerances to ±0.02mm are achievable on critical features. In-house powder coating with 5-tank nano-ceramic pre-treatment provides corrosion protection suitable for agricultural environments.

For new programmes, we conduct full DFM review before die design begins, provide first article inspection with dimensional report and material certificate, and can support PPAP documentation for customers who require it. Traceability from alloy heat to finished component is maintained for every production batch.