A die cast EV motor housing is an aluminum casting that holds the stator and bearings of an electric drive unit and, in many designs, carries the coolant passages too. Molten alloy is injected into a steel die at high pressure, and the part performs only when four things line up: the right alloy, controlled gas porosity, machined datums that keep the bearings aligned, and a process validated before volume starts.
This guide covers what the housing has to do, why aluminum die casting suits it, alloy choice, porosity and leak control, how die casting compares with gravity casting and CNC machining, the path from drawing to mass production, and what EX Die Casting publishes about its machines and inspection equipment.
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Table of contents
- What Is a Die Cast EV Motor Housing?
- Why Aluminum Die Casting Suits EV Motor Housings
- Which Aluminum Alloy Should You Specify for an EV Motor Housing?
- Controlling Porosity and Leaks in a Die Cast Motor Housing
- Die Casting vs Gravity Casting vs CNC Machining for Motor Housings
- From Drawing to Mass Production: How a Housing Project Runs
- What Part Size and Volume Can EX Die Casting Handle?
- How to Choose an EV Motor Housing Manufacturer
- Die Cast EV Motor Housing FAQ
- Related Reading
- Sources
What Is a Die Cast EV Motor Housing?
A die cast EV motor housing is the aluminum shell around the stator of an electric motor. It locates the bearings, closes the drive unit against dirt and oil, and, in liquid-cooled designs, contains the water jacket.
Picture the RFQ package on a purchasing engineer's desk. A 3D model of the housing, a coolant jacket marked in blue, a leak-rate line in the notes, a launch date that will not move. Nobody asks whether the housing can be cast. The real question is whether it can be cast, machined to the bearing datums and shown not to leak, lot after lot.
That is why the housing is rarely a single part. A drive unit usually needs:
- Motor (stator) housing: the main body around the stator, often with ribs for stiffness and a cooling jacket.
- End and rear covers: they close the housing and carry bearing seats, so their flatness and concentricity matter as much as the main body.
- Aluminum gearbox housing: the reduction stage beside the motor. In integrated e-axles the motor and gearbox housings are sometimes combined or bolted into one stack.
EX Die Casting lists EV motor housings, aluminum gearbox housings and battery enclosures on its page for aluminum die casting for automotive and motorcycle components.
Four jobs the casting must do at once
Stator bore and bearing seats stay concentric after machining and after years of thermal cycling.
Coolant, gear oil and dirt stay on the right side of the wall.
Winding heat has a path into the coolant or the housing surface.
Bolt bosses carry vibration and torque reaction without cracking.
Here is where it gets difficult. The casting is thin where weight matters and thick around bolts and bearings. That mix is exactly where shrinkage and gas porosity like to collect.
Why Aluminum Die Casting Suits EV Motor Housings
Aluminum die casting suits a motor housing because one die forms the ribs, bosses, mounts and cooling features in a single shot, and at volume it gives the lowest cost per part of the common routes.
Volume is the point. The IEA reports that electric car sales grew 20% worldwide to exceed 20 million in 2025, about one quarter of all new cars sold, and expects 23 million in 2026, or 28% of sales (IEA, Global EV Outlook 2026). That scale is what lets a die investment pay back across a platform life.
- Integration. Ribs, bosses and channels come out of one die, so fewer parts need machining or assembly.
- Weight. Aluminum is roughly one third the density of steel, so thin ribbed walls save mass where it counts.
- Cycle time. Once the die is proven and the process is stable, a casting cycle is measured in seconds. The basics are in our article on what aluminum high pressure die casting is.
- Repeatability. Same die, same dimensions, shot after shot.
- Recycled content. EX can source all materials from 100% recycled aluminum alloys, which helps with ESG reporting.
The catch: the die is the big upfront cost, and a design change means modifying hardened steel. If your volume is uncertain, say so in the RFQ. A realistic forecast changes which route is cheapest.
Which Aluminum Alloy Should You Specify for an EV Motor Housing?
Start from the drawing, because OEM specifications often name the alloy. Where they do not, ADC12 (A383) is the fluid, cost-effective grade, ADC10 (A380) adds strength and ductility for structural housings, and A360 offers good airtightness and corrosion resistance.
High fluidity, stable castability, cost-effective. EX lists automotive and motorcycle parts and electronic enclosures among its typical uses.
Improved strength and ductility for structural parts. EX lists EV structural components among its typical uses.
Good airtightness and corrosion resistance. EX lists airtight components and fluid control parts.
Heat-treatable to T6, with a balance of strength and ductility. EX lists EV suspension parts.
Heat treatment has a catch. Trapped gas is the reason heat-treated die castings need low gas content. The Archives of Foundry Engineering study cited below notes that vacuum die casting can bring gas content under 10 cm³/100 g, which allows simpler heat treatment and welding.
If the housing also has to move heat, EX lists a high thermal conductivity grade, DX-19, for server heat sinks. Whether it fits a motor housing depends on strength and castability, so raise it at DFM instead of assuming.
Grade is only half of material control. EX checks each aluminum batch by OES spectrometry and keeps traceability from raw material batch to finished casting, with optional RoHS and REACH reports. The details sit on the capabilities page.
Controlling Porosity and Leaks in a Die Cast Motor Housing
You cannot remove porosity from a die casting entirely, but you can lower the gas content, keep what remains away from sealing walls and prove it with inspection. Vacuum is the biggest single lever.
The numbers explain why. Researchers at the Łukasiewicz Research Network report that die-cast parts typically contain about 10 to 50 cm³ of gas per 100 g, and that a vacuum system can bring that below 10 cm³/100 g, even down to 1 (Piwowońska, Białoń and Dudek, Archives of Foundry Engineering, 2026).
Where the gas comes from, and what stops it
- Gassy or dirty melt. Each melt at EX is skimmed, degassed, settled and gas-tested in dual crucible furnaces, supported by five degassing and slag removal machines. A reduced pressure test checks gas content after degassing.
- Air trapped in the shot sleeve and cavity. Two vacuum systems pull air out before the metal arrives, and the Moldflow review at DFM looks at air entrapment and venting before the die is cut.
- Lubricant vapor and uneven die temperature. ABB IRB 4600 Foundry Plus spray robots control how much release agent goes on, six mold temperature controllers hold die temperature, and an infrared thermal camera checks the temperature distribution. The full list is on the peripheral equipment page.
- Defects that slip through. Two industrial X-ray inspection systems look for internal porosity, shrinkage and cracks without damaging the part. See the inspection equipment list.
One practical tip from the quality side: set porosity limits by zone, not as one global number. A coolant-jacket wall and a bolt boss do not need the same limit. A single number either rejects good parts or hides a bad one.
Die Casting vs Gravity Casting vs CNC Machining for Motor Housings
For series production, high pressure die casting usually wins on cost per part. Gravity or low-pressure casting suits low volume or pressure-critical walls, and CNC machining from solid suits prototypes and finishing.
| Route | Best fit | Walls and complexity | Tooling and design changes | Cost per part at volume | Leak-tightness risk |
|---|---|---|---|---|---|
| High pressure die casting | Series production, medium to high volume | Thin walls, with ribs, bosses and cooling features in one shot | High die cost up front. A design change means modifying hardened steel. | Lowest once the process is stable | Gas porosity. Managed with vacuum, degassing and X-ray inspection. |
| Gravity or low-pressure casting | Low to medium volume, or walls that must be pressure-tight | Thicker walls and simpler shapes | Lower tooling cost than die casting, but slower cycles | Higher, because cycles are slower | Slower filling usually traps less gas. |
| CNC machining from solid or extrusion | Prototypes, bridge builds and very low volume | Almost any outer shape, but internal coolant channels are hard to machine | No die. Changing the program changes the part. | Highest, with long cutting time and a large share of material turned into chips | Solid stock has no casting porosity. Cover plates and joints replace cast channels. |
A general industry comparison to help you shortlist a route. It is not a quotation or an EX Die Casting specification.
Most housings use two routes anyway. The casting makes the shape, and CNC machining makes the bearing seats, sealing faces and threads. EX runs 50 CNC milling machines in-house, including 4-axis and vacuum-fixture work, so the datum scheme can be planned with the die instead of patched afterwards. The capabilities page lists the machining services.
From Drawing to Mass Production: How a Housing Project Runs
A motor housing project runs through eight stages, and the most valuable work happens before steel is cut, at the DFM and Moldflow review.
| Stage | What happens | What you send or receive |
|---|---|---|
| 1. RFQ | EX reviews the request and the files behind it. | You send annual volume, 2D drawings and 3D models. |
| 2. DFM review | Parting lines, wall thickness, draft angles, gating and venting are evaluated against your drawing. | You receive manufacturability feedback and proposed changes. |
| 3. Moldflow analysis | Filling behavior, air entrapment, cold shut locations and defect risks are simulated. All new projects can be supported by Moldflow. | You receive gating and venting findings. |
| 4. Tooling and T0 trial | The die is built and tried. Moldflow lets dies approach mass-production conditions as early as the T0 trial. | You receive trial parts. |
| 5. APQP and PFMEA | Phase control under IATF 16949. PFMEA covers injection, clamping, cooling, part removal and secondary processes. | You receive the risk plan and controls. |
| 6. PPAP | PPAP documentation, dimensional inspection reports and locked process parameters are completed before launch. | You receive the PPAP package. |
| 7. Mass production | Casting with vacuum, robotic spray and mold temperature control, then CNC machining and surface finishing as required: vibratory finishing, sandblasting, anodizing, ED coating, powder coating or liquid painting. Can die cast parts be color anodized? | You receive production parts. |
| 8. Inspection and traceability | X-ray, CMM and spectrometer checks, with digitalized records, SPC capability and traceability from raw material batch to casting. | You receive inspection records. |
EX does not publish lead times, because they depend on part size, die complexity and the approval level your customer requires. Ask for a project timeline with the quote. The capabilities page describes the tooling process in detail.
What Part Size and Volume Can EX Die Casting Handle?
EX Die Casting runs 19 aluminum die casting machines from 150 to 1100 tons, and its two 1100-ton machines handle parts up to an estimated 15 kg and 160,000 mm² of projected area.
| Machine | Quantity | Origin | Est. max product weight | Est. max projected area (mm²) |
|---|---|---|---|---|
| 1100T Die Casting Machine | 2 units | Italy | 15 kg | 160,000 |
| 650T (500T) Die Casting Machine | 6 units | Japan, Taiwan | 3.3 kg | 93,000 |
| 420T (350T) Die Casting Machine | 5 units | Japan, Taiwan | 1.8 kg | 60,000 |
| 250T Die Casting Machine | 4 units | Japan, Taiwan | 0.8 kg | 36,000 |
| 150T Die Casting Machine | 2 units | Taiwan | 0.3 kg | 21,000 |
Source: the EX Die Casting die casting machine list.
How to read the table: clamping force scales with projected area, not weight. A wide, shallow end cover can need a bigger machine than a heavier, compact part. Check both numbers against your model.
Across the plant, EX states an annual capacity of up to 8.5 million parts, 50 CNC milling machines and a quality system built on IATF 16949. ISO 9001 and ISO 14001 are also published on the certificates page.
How to Choose an EV Motor Housing Manufacturer
Choose an EV motor housing manufacturer on evidence you can verify: a current quality system certificate, documented control of gas in the melt and the die, and named methods for finding internal defects.
- Quality system. Ask for the current IATF 16949 certificate and its scope. EX publishes IATF 16949, ISO 9001 and ISO 14001 certificates.
- Gas control. Ask how vacuum, degassing and gas testing are done and recorded. EX publishes two vacuum systems, five degassing machines and gas-content testing for each melt.
- Tooling and simulation. Ask who runs DFM and whether Moldflow is done before steel is cut. EX publishes DFM, Moldflow, APQP, PFMEA and PPAP under IATF 16949.
- One roof. Ask whether machining and finishing are in-house. EX publishes 50 CNC milling machines plus six finishing processes.
- Inspection. Ask which method finds internal porosity and how dimensions are verified. EX publishes two X-ray systems, two CMMs, a spectrometer and a universal testing machine.
- Traceability. Ask whether you can trace a casting back to a raw material batch. EX publishes digitalized quality records, SPC capability and batch-to-casting traceability.
If a supplier cannot tell you how it inspects for porosity, treat that as the answer.
For a documented example of a process review, read the automotive aluminum die casting mass production improvement case study.
Die Cast EV Motor Housing FAQ
What information do you need to quote a die cast EV motor housing?
At minimum your annual volume, 2D drawings and 3D models, the three items EX asks for on every RFQ. Add the alloy if your spec names one, the leak-test method and acceptance limit, the machined datums, and any surface treatment or PPAP level. The more of that sits on the drawing, the less guesswork sits in the price.
Can a die cast motor housing be leak-tight enough for a coolant jacket?
Yes, but casting alone does not guarantee it. Vacuum die casting lowers gas content, which cuts the porosity that leaks follow. Melt degassing, gating reviewed in Moldflow and X-ray inspection do the rest. Put the leak-test method and limit on the drawing and agree them at DFM. Some programs add a sealing step after machining, and your leak specification decides whether yours needs one.
Which alloy should I specify for an EV motor housing?
Your drawing or OEM specification usually names it. Where it does not, ADC12 (A383) is the fluid, cost-effective grade, ADC10 (A380) adds strength and ductility for structural housings, and A360 offers good airtightness and corrosion resistance. Settle the final choice at DFM against wall thickness, strength and leak requirements.
Does EX Die Casting machine the housing after casting?
Yes. EX runs 50 CNC milling machines for 3D contouring, surface milling, 4-axis machining, vacuum-fixture work, tapping and drilling, so bearing seats and sealing faces can be finished in-house. Agree the datum scheme at DFM so the casting leaves stock where machining needs it.
How is porosity checked in a die cast housing?
There are two checkpoints. At the melt, reduced pressure testing checks gas content after degassing. At the part, EX's two industrial X-ray systems look for internal porosity, shrinkage and cracks without damaging the casting. Dimensions are checked on two CMMs and alloy composition on a spectrometer. Ask which sampling plan applies to your part, because it belongs in the control plan.
Related Reading
Sources
- IEA (2026), Global EV Outlook 2026, executive summary
- Piwowońska, J., Białoń, J. and Dudek, P. (2026), Optimization of the High Pressure Die-Casting Process to Reduce Porosity, Archives of Foundry Engineering, 26(2), 15-20
- Equipment, capability and certificate data: EX Die Casting pages for die casting machines, peripheral equipment, measuring and inspection, capabilities and certificates.
Send your 3D model, 2D drawing and annual volume.
If you are comparing EV motor housing manufacturers, a drawing review is the quickest test of fit. Add the alloy, leak-test method and datum requirements you already have, and the EX team can review your die cast EV motor housing drawing and get back to you.
EX Die Casting provides high quality, reliable lead times, and professional process capability for global customers.
For any RFQ or new project, please fill out the form or email us with your annual volume, 2D drawings, and 3D models. Our team will get back to you shortly.
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