Case Study – How a Chinese Expert Optimized Die Casting Furnace for EV Part Production

In late 2023, I was contacted by a die casting plant in Rayong, Thailand. They supply structural components for electric vehicles — battery trays, motor housings, and front shock towers. Their main customer is a Chinese OEM that has invested heavily in EV production in Southeast Asia. The plant had recently installed a 2,500-tonne vacuum-assisted die casting machine. The machine was ready. The furnace was not.

The plant manager told me: “Our leak test rejection rate is 9%. We cannot meet the OEM’s requirement. We need to fix the furnace, not the die.”

I spent two weeks on site. We did not buy a new furnace. We optimised the existing one. By the end of the following month, the leak test rejection rate had dropped to 1.8%. Cycle time improved by 8%. Energy consumption per tonne fell by 22%.

This is how we did it.

The Starting Point: A Legacy Furnace on a Modern Machine

The furnace was a gas-fired holding furnace with a capacity of 1,200 kg. It was designed for conventional HPDC. It had a simple temperature controller, a manual ladle, and no vacuum integration.

The problems were immediately visible:

The furnace was not broken. It was simply not designed for the demands of EV structural casting.

Step 1: Diagnosing the Real Problem

I started with a full process audit. I measured metal temperature at three points: in the furnace, in the ladle, and at the shot sleeve. The temperature dropped 35°C during transfer. That alone explained the cold shuts and incomplete fills.

I measured hydrogen content using a portable analyser. At 0.28 ml/100g Al, it was well above the recommended maximum of 0.15 ml/100g Al for structural EV parts. That explained the porosity and leak failures.

I watched the dosing cycle. The ladle was manual. The operator was skilled, but human. Shot weight varied by up to 5%. In a 6 kg shot, that is 300 grams of variation. Enough to cause flash on one shot and cold shut on the next.

The furnace temperature controller was cycling on and off with a 15°C hysteresis. That means the metal was always either heating or cooling. Never stable.

The root cause was not the furnace itself. It was the system around it. The furnace was a standalone unit. It was not integrated with the die casting machine, the vacuum system, or the metal treatment process.

Step 2: The Optimisation Plan

We developed a four-part plan:

Replace the gas-fired holding furnace with an electric dosing furnace. Electric gives precise temperature control. Dosing gives consistent shot weight. And no combustion means no moisture in the furnace atmosphere.

Integrate inline degassing. Hydrogen must be removed before the metal reaches the shot sleeve. A rotary degasser with argon purging was installed between the furnace and the dosing unit.

Reduce transfer time and temperature loss. A heated launder and a short, direct transfer path. Every second counts.

Train operators on the new process. The best equipment fails without skilled hands.

We chose a Chinese electric dosing furnace with a capacity of 1,500 kg. It was compatible with vacuum-assisted die casting. It had a dosing accuracy of ±1%. It could hold temperature within ±3°C. And it had a built-in data logger for traceability.

The furnace cost $68,000. The degassing unit cost $12,000. The heated launder and installation cost $8,000. Total investment: $88,000.

Step 3: Installation and Commissioning

We installed the new furnace in a weekend shutdown. The old furnace was removed. The new one was positioned directly next to the die casting machine. The transfer distance was reduced from 4 metres to 1.5 metres.

Commissioning took three days. We ran test shots with scrap metal. We measured temperature at every point. We adjusted the dosing parameters. We tuned the degasser.

The first production trial was a battery tray. The leak test rejection rate was 3.1%. Better than 9%, but not good enough.

We found two remaining problems. First, the vacuum system was pulling air through the furnace door seal. The seal was not rated for vacuum. We replaced it with a high-temperature vacuum seal. Second, the degasser was not running long enough. We increased the degassing time from 5 minutes to 8 minutes per batch.

The next trial: rejection rate 1.8%.

Step 4: Results After One Month

The plant manager was pleased. But he was also surprised. He had expected to buy a new furnace. Instead, we optimised the system.

What Made the Difference

Three things drove the improvement:

1. Temperature control. The electric dosing furnace held ±3°C. The gas furnace swung ±18°C. In EV casting, temperature stability is not a luxury. It is the difference between a leak-tight part and a scrap part.

2. Hydrogen removal. Inline degassing with argon reduced hydrogen from 0.28 to 0.12 ml/100g. That eliminated the porosity that caused leak failures.

3. Dosing accuracy. The electric dosing furnace delivered ±1% shot weight. The manual ladle delivered ±4%. That reduced flash and cold shuts.

I have written about how to choose a die casting furnace and how to optimise burner efficiency. But for EV parts, the furnace is only one part of the system. The degasser, the transfer, and the vacuum integration matter just as much.

What You Can Apply

If you are producing EV structural parts, ask yourself these questions:

Is your furnace holding temperature within ±5°C? If not, you will have inconsistent fills.

Is your hydrogen content below 0.15 ml/100g Al? If not, you will have porosity.

Is your dosing accuracy within ±2%? If not, you will have flash and cold shuts.

Is your transfer time under 30 seconds? If not, you are losing temperature and forming oxides.

Is your furnace compatible with vacuum-assisted die casting? If not, you are limiting your quality.

These are not theoretical. They are the minimum requirements for EV structural casting. I have seen foundries in China, Thailand, and Mexico fail because they ignored one of these.

When to Call an Expert

You can measure these things yourself. A pyrometer, a hydrogen analyser, and a stopwatch will tell you most of what you need to know. But sometimes an experienced eye sees the system, not just the components.

The Thai foundry had a competent maintenance team. They had kept the old furnace running for years. But they had never integrated a furnace with vacuum die casting. They did not know what they did not know.

My fee for the two-week audit and commissioning support was $14,000. The annual saving was $186,000. That is a 13x return.

If you are starting EV part production, and your rejection rate is above 3%, call someone. Or use the checklists on this blog. Either way, do not wait.

Final Thoughts

Optimising a die casting furnace for EV production is not about buying the most expensive equipment. It is about matching the furnace to the process. Electric dosing, inline degassing, short transfer, and vacuum compatibility.

In my 25 years, I have seen this pattern repeat in foundries across the world. The biggest gains come from integration, not from isolated upgrades.

If you run a die casting plant, start by measuring your temperature stability, hydrogen content, and dosing accuracy. If any of them is out of specification, fix it. You will see the difference in your leak test results.

Internal links: How to Choose the Right Aluminium Melting Furnace, How Die Casting Furnace Technology Is Evolving for Electric Vehicle Manufacturing