Motor housings
Stator shells and end bells for BLDC, servo and induction motors. Concentricity between the two bearing bores sets the air gap, so both bores are bored in one setup wherever the geometry allows rather than flipping the part.
Die cast aluminum housings
Aluminum Die Cast Housings
An aluminum die cast housing is a structural casting that carries mechanical load and locates rotating or moving components, such as a motor housing, pump body, gearbox case or valve body. CharMax Precision casts housings in A380, ADC12, A360 and A413 aluminum from 0.2 to 12 kg, then machines bearing bores and sealing faces to ±0.02 mm.
In short
An aluminum die cast housing is a structural casting that carries mechanical load and locates rotating or moving components, such as a motor housing, pump body, gearbox case or valve body. CharMax Precision casts housings in A380, ADC12, A360 and A413 aluminum from 0.2 to 12 kg, then machines bearing bores and sealing faces to ±0.02 mm.
The engineering priorities for a housing are structural. Bearing bore concentricity, sealing face flatness, pressure tightness under working load, a continuous load path from the mounting feet to the shaft centreline, and wall thickness chosen for stiffness rather than for the thinnest section the process can fill. If the part you are sourcing is instead a sealed box whose job is to protect and shield electronics, the die cast aluminum enclosures page linked below covers gasket design, IP ratings and EMI shielding.
Housings are the part family where the split between cast and machined features matters most to price. We cast the form, the ribs, the cooling features and the bolt bosses, then machine only the bores, faces and threads that genuinely have to be accurate. Deciding that split at design review, rather than after tooling, is usually worth more than any negotiation over piece price.
Capability at a glance
| Typical parts | Motor, pump, gearbox, valve, compressor and actuator housings |
|---|---|
| Preferred alloys | A380 general purpose, A360 where pressure tight or outdoors |
| Part weight | 0.2 to 12 kg per housing |
| Wall thickness | 2.5 to 4 mm on structural sections |
| As-cast tolerance | ±0.1 mm for the first 25 mm |
| Bearing bore | H7 fit, ±0.02 mm after machining |
| Sealing face flatness | 0.02 mm per 100 mm machined |
| Surface roughness | Ra 1.6-3.2 µm as-cast, Ra 0.8 µm machined |
| Machining | 3, 4 and 5-axis CNC on dedicated casting fixtures |
| Leak testing | Air or helium test to your specified pressure |
| Annual volume | 500 to 500,000+ parts |
| Lead times | 25-40 days tooling, 15-25 days production |
What an aluminum die cast housing is
A housing is a structural casting whose primary job is to carry load and hold other components in position. It provides bearing seats for a shaft, a sealed cavity for oil or hydraulic fluid, mounting feet that transfer load into the machine frame, and frequently integral cooling fins or a mounting flange. Unlike a cover or a plate, a housing is loaded in service and its internal geometry is dimensionally functional rather than decorative.
Because a housing is loaded, section thickness is driven by stiffness rather than by the minimum the process can fill. Structural sections run 2.5 to 4 mm rather than the 1.5 mm achievable on a thin-wall part, with ribs and gussets carrying load into the mounting points. Past about 5 mm the section stops adding useful stiffness and starts adding solidification time, which shows up as shrinkage porosity in exactly the region you were trying to strengthen.
The features that define a housing are almost never as-cast. A bearing bore, a shaft centreline height, a bore-to-bore centre distance and a gasketed joint face all need better than ±0.05 mm, which puts them into a machining operation. The casting exists to put metal in roughly the right place, cheaply, with the ribs and passages that would be slow to machine, and to give the fixture something repeatable to locate on.
Pump housings
Volute, gear and vane pump bodies where the casting must be pressure tight and impeller clearance is a machined dimension. A360 is usually specified because it is rated excellent for pressure tightness.
Gearbox and transmission cases
Multi-bore cases where bore-to-bore centre distance controls gear mesh and backlash. All bores and the mating face are machined from a single datum scheme so tolerances do not stack between setups.
Valve bodies
Flow passages cored into the casting, with seat faces, port threads and flange faces machined afterwards. Wall thickness in the pressurised region is set by working pressure and verified by leak test.
Compressor housings
Scroll and rotary housings with tight running clearances and a sealed joint face. These parts combine a machined precision cavity with cast external cooling fins on the same casting.
Actuator and cylinder bodies
Linear and rotary actuator bodies where the working bore is bored or honed and the mounting interface holds a positional tolerance referenced to that bore.
Housing or enclosure: which part do you actually need?
The words housing and enclosure are used interchangeably in everyday speech, but they describe two different engineering problems and the design rules diverge almost immediately. Getting the distinction right before you send a drawing saves a round of DFM comments.
A housing is loaded. Its critical requirements are bearing bore concentricity, sealing face flatness, pressure tightness and a defined load path, and its wall thickness is chosen for stiffness. An enclosure is generally not structurally loaded. Its critical requirements are gasket groove geometry, IP65 or IP67 ingress protection, EMI shielding, cable gland bosses, PCB mounting standoffs and lid flatness for even gasket compression, with cosmetic finish frequently as important as any dimension on the drawing.
If your part locates a shaft, a bearing, a gear, an impeller or a piston, you are on the right page. If your part is a sealed box that protects a circuit board, a terminal block or a sensor, follow the link to Die Cast Aluminum Enclosures in the related links below, where gasket groove design, ingress protection and shielding are covered properly.
| Design factor | Structural housing | Electronics enclosure |
|---|---|---|
| Primary function | Carry load and locate moving components | Protect and shield electronics |
| Typical wall thickness | 2.5 to 4 mm, set by stiffness | 2 to 3 mm, biased toward thin wall |
| Critical tolerance | Bearing bore H7, bore-to-bore centre distance | Gasket groove depth and lid face flatness |
| Sealing method | Shaft seals, O-rings and a pressure-tight cast wall | Continuous gasket compressed by evenly spaced screws |
| Preferred alloy | A380 for machinability, A360 where pressure tight | A360 for corrosion resistance, ADC12 for thin walls |
| Proof of function | Leak test at working pressure, CMM bore report | IP ingress test, gasket compression check, salt spray |
| Finish priority | Corrosion protection and paint adhesion | Cosmetic appearance and colour match |
| Typical machining | Bores, sealing faces, threads, mounting datums | Lid mating land, gland holes, threaded bosses |
Some parts are genuinely both, such as a motor drive housing with a sealed electronics cavity. Send the drawing and we will apply both rule sets to the regions that need them.
Alloy options for die cast housings
Housing alloy selection turns on three questions: how much of the casting will be machined, whether the cavity has to hold pressure, and whether the part lives outdoors or in a corrosive environment. Strength is rarely the deciding factor, because all four common die casting alloys land within 10% of each other on tensile strength.
A380 is the default and covers most housings. It has the best machinability of the group, which matters when a housing has two bearing bores, a sealing face and a dozen threaded holes to cut. A360 is the choice when the casting must be pressure tight or corrosion resistant, at the cost of slightly harder machining and a few percent more on the alloy price. ADC12 comes in when a housing has thin transitional sections or a long flow path from the gate. A413 appears where a housing also has to dissipate heat.
One limit worth stating early: high pressure die castings are not given a conventional T6 heat treatment, because gas entrapped during injection expands at solution temperature and blisters the surface. If your housing calculation depends on T6 properties, the answer is a different casting process or a redesign with more section, and we will say so at design review rather than after the die is cut.
| Alloy | Specify it for | Trade-off |
|---|---|---|
| A380 | General motor, gearbox and machine housings with heavy machining | 3 to 4% copper limits outdoor corrosion life without a coating |
| A360 | Pump bodies, hydraulic housings, sealed and outdoor housings | Slightly harder to machine and a few percent more expensive than A380 |
| ADC12 | Housings with thin transitional walls or long flow paths | Machinability rated good rather than very good |
| A413 | Housings that also dissipate heat, at 121 W/m·K | Lowest tensile strength of the four at 296 MPa |
Full mechanical property data for each alloy is on the material pages linked below. Send the drawing with working pressure, ambient environment and machining scope marked and we will recommend a grade.
How a die cast housing is manufactured
A housing program runs through the same stages as any casting, but two of them carry most of the risk: die design around the cored cavity, and the machining fixture strategy. Cored internal passages, bearing pockets and bolt bosses all have to release from the die, so parting line position and any slides are settled before anything else. Once the steel is cut, those decisions are fixed for the life of the tool.
Flow and solidification simulation is run before cutting steel, with particular attention to the heavy sections around bearing bosses. A solid boss is a thermal mass: it freezes last, shrinks inward, and puts porosity exactly where a bore is about to be machined. Coring the boss out and blending it into the wall with a generous radius fixes the problem in the model rather than in production.
After casting, gates and overflows are trimmed and the part is shot blasted, then it goes onto a fixture built specifically for that casting, locating on cast datum pads. Everything that needs accuracy is machined against that one datum scheme so errors do not stack: bearing bores, the sealing face, port threads and positionally toleranced mounting holes. Pressure-tight housings are leak tested after machining, because machining is what usually breaks into a porous section and exposes a leak path.
- Cast: outer form, ribs and gussets, cooling fins, mounting feet, cored internal passages, bolt bosses, cable and hose channels, cast-in part identification
- Cast: rough bearing pockets carrying 0.5 to 1.0 mm of machining stock, plus cast datum pads for the machining fixture to locate on
- Machined: bearing bores to an H7 fit, bored in a single setup wherever possible so concentricity is controlled by the machine rather than by the fixture
- Machined: sealing and mating faces to 0.02 mm per 100 mm flatness and Ra 0.8 µm or better
- Machined: threaded holes, dowel holes, port threads and any positionally toleranced mounting hole
- Machined: bore-to-bore centre distances, shaft centreline height and every datum-referenced geometric tolerance on the drawing
- Left as-cast: wall thickness, external surfaces, rib geometry and non-functional faces, which is what keeps machining cost proportional to function
| Housing feature | As-cast | After CNC machining |
|---|---|---|
| Bearing bore diameter | ±0.1 mm | H7 fit, ±0.02 mm |
| Bore-to-bore centre distance | ±0.15 mm across the parting line | ±0.02 mm |
| Sealing face flatness | 0.1 mm per 100 mm | 0.02 mm per 100 mm |
| Sealing face roughness | Ra 1.6-3.2 µm | Ra 0.8 µm or better |
| Mounting hole position | ±0.2 mm | ±0.05 mm |
| Shaft centreline height | ±0.15 mm | ±0.03 mm |
| Linear dimension, first 25 mm | ±0.1 mm | ±0.02 mm |
| Wall thickness | ±0.15 mm | Not usually machined |
As-cast values follow NADCA precision standards and widen by roughly ±0.02 mm per additional 25 mm of dimension. Dimensions crossing a moving slide carry a further allowance.
Design considerations for die cast housings
Size walls for stiffness, not strength
Deflection, not fracture, is what usually governs a housing. Use 2.5 to 4 mm on structural sections and gain stiffness with rib depth instead of wall thickness, because section stiffness rises with the cube of depth while solidification time rises with thickness.
Core out bearing bosses
Blend the boss into the wall with a generous radius and core the centre rather than casting it solid. A solid boss freezes last, shrinks inward and concentrates porosity directly under the bore you are about to machine.
Keep critical bores in one die half
Concentricity between two bores is far easier to hold when both sit on the same side of the parting line, and easier again when both are machined in one setup. A bore that must cross the parting line will be ±0.15 mm as-cast and has to be machined.
Raise machining pads
Design sealing and mating faces as pads standing 0.5 to 1.0 mm above the surrounding surface rather than flush with the casting. The pad guarantees full cutter engagement and stops the tool skipping across an as-cast surface.
Nominate cast datums on the drawing
Specify three cast pads, or two pads and a boss, as the machining fixture datum and mark them explicitly. Without defined datums, machined feature positions vary part to part no matter how accurate the machine is.
Specify the pressure, not just no leaks
State the test pressure and medium on the drawing. Pressure-tight housings need A360 or vacuum assist, a minimum 3 mm wall in the pressurised region, and a machining plan that does not break into a porous core.
Draft deep cored features generously
Use 1 to 2° on external walls and 2 to 3° on internal walls and cored bores, and more on deep features. Ejection force rises with die contact area, and a deep cored housing has a great deal of it.
Choose threads by service life
Tapped holes in A380 are fine for joints assembled once. Where a joint is serviced repeatedly or carries high preload, specify a steel threaded insert or a through-bolt rather than relying on cast aluminum threads.
Design the load path deliberately
Trace metal continuously from the shaft centreline to the mounting feet, keep the path short, and gusset every corner it turns. A housing that is stiff in bending but flexible in torsion will still lose bearing alignment under load.
Industries that buy aluminum die cast housings
Automotive and EV
Auxiliary motor housings, e-pump bodies, actuator housings and transmission covers, supplied with PPAP documentation, first article reports and IMDS data where the customer program requires it.
Robotics and automation
Joint housings, harmonic drive and gearbox cases and servo motor shells, where stiffness-to-weight sets arm dynamics and machined datum accuracy sets repeatability at the tool point.
Industrial equipment
Pump volutes, valve bodies, gearbox cases and compressor housings. These programs often run on the same tooling for ten years or more, so tool maintenance and dimensional stability matter as much as first-article accuracy.
Fluid power and hydraulics
Manifold and valve housings that hold working pressure, cast in A360 with wall thickness set by the pressure rating and every lot leak tested before shipment.
Medical equipment
Imaging drive and instrument housings where lot traceability to the ingot batch, documented first article inspection and a cleanable finish are specified conditions of supply.
Energy and power generation
Generator end housings, inverter bodies and sensor housings for outdoor installation, usually A360 with a powder coated finish and salt spray tested conversion coating underneath.
Proof
Related production programs
Real parts we have manufactured that involved this capability.
A360 Aluminum Pump Housing: From Billet Machining to 8,000 Units a Year
A European industrial pump manufacturer converted a billet-machined housing to A360 die casting to reach 8,000 units a year, holding 6 bar pressure tightness, an H7 bearing bore and a 0.05 mm sealing face.
ADC12 Robot Joint Housing at a 2 mm Wall: 34% Lighter Than Machined
A collaborative robot manufacturer moved a joint housing from machined prototypes to ADC12 die casting at 12,000 units a year, cutting 180 g per joint while holding ±0.02 mm concentricity between the harmonic drive seat and the encoder bore.
A413 LED Heat Sink Housing: Two Parts to One, 11 °C Cooler
An LED lighting brand replaced a bonded two-piece design, an extruded heat sink adhered to a die cast housing, with a single A413 casting, removing the thermal interface and taking 11 °C off the LED junction temperature at 60,000 units a year.
Keep exploring
Related capabilities and resources
Manufacturing services
Aluminum alloys
Part types
Industries served
Further reading
Frequently asked questions
What tolerance can you hold on a bearing bore in a die cast housing?
A machined bearing bore holds ±0.02 mm and an H7 fit; the same bore as-cast holds ±0.1 mm. Bores are therefore cast with 0.5 to 1.0 mm of stock and finished on a CNC machining centre, and where two bores must be concentric, both are cut in one setup so the machine controls the relationship rather than the fixture. Roundness and cylindricity are reported on request from CMM measurement.
Can a die cast aluminum housing be pressure tight?
Yes, and it is a routine requirement on pump and hydraulic housings. Pressure tightness comes from four things together: A360 alloy, which is rated excellent for pressure tightness, a minimum 3 mm wall in the pressurised region, gating and venting designed so gas does not collect in that region, and vacuum assist where the pressure is high. Every pressure-tight part is leak tested to the pressure stated on the drawing before it ships.
How thick should the walls of a die cast housing be?
2.5 to 4 mm on structural sections, and 3 mm minimum anywhere that holds pressure. That is thicker than the 1.5 mm typical wall we quote on thin-wall parts, because a housing is loaded and needs stiffness. Going above roughly 5 mm rarely helps: the extra section solidifies slowly and traps shrinkage porosity, so stiffness is better bought with 12 to 15 mm deep ribs at 60 to 80% of the wall thickness.
Should I choose a die cast housing or a machined housing?
Volume decides. Above roughly 2,000 housings a year, casting is clearly cheaper because the tooling cost of 3,000 to 25,000 USD spreads thin and the cast ribs, passages and fins would be slow to machine. Below 500 a year, machining from billet is usually cheaper and needs no tooling. Between 500 and 2,000, it depends on geometry, and we will price both rather than argue about it.
Can you cast internal oil or coolant passages into a housing?
Yes, within the constraint that every cored passage has to release from the die. Straight or gently drafted passages that run in the draw direction are straightforward, passages perpendicular to the draw need a slide, and passages that curve in two planes generally cannot be cast at all. The usual solution for a complex circuit is to cast the simple runs, drill the cross-connections, and plug the drill entries.
Do you machine the housings you cast, or do we have to arrange that?
We machine in-house on 3, 4 and 5-axis machining centres, using fixtures built for each casting. Keeping casting and machining in one company means one supplier owns the entire tolerance stack, so there is no argument about whether an out-of-spec bore came from the casting or the machining. You can also buy raw or shot-blasted castings and machine them yourself if you prefer.
How do you control porosity in die cast aluminum?
Porosity is controlled at three stages: melt preparation with degassing and filtration, die design with engineered overflows, vents and gate geometry validated by flow simulation, and process control with logged shot profiles and die temperatures. Where parts must be pressure tight or heavily machined in critical areas, we design vacuum assist or use A360 alloy, and verify with leak testing or X-ray inspection.
Request for quote
Get your housing quoted with a machining plan
Send your 2D drawing and 3D model. You will get piece pricing, tooling cost, lead time and a written DFM report that states which features we would cast, which we would machine, and what tolerance each one will hold.
- Engineering response within 24 hours on business days
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