Porosity is the nemesis of die casting. Learn how Vacuum Die Casting works, when to use it, and how Sureton uses it to deliver leak-proof, high-density aluminum parts.
There is no worse feeling for a manufacturing engineer than machining a seemingly perfect die-cast part, only to hit a pocket of air 2mm below the surface. The part is scrapped, the tool might be damaged, and your yield rate takes a nosedive.
In the world of High-Pressure Die Casting (HPDC), porosity is the enemy. While some minute level of porosity is an accepted characteristic of even high-quality die casting, the difference between a “commercial grade” part and a high-integrity structural component often comes down to one technology: Vacuum Assist.
At Sureton, we don’t believe in crossing our fingers and hoping for the best. Here is the technical breakdown of how to reduce porosity in die casting using vacuum technology, and when you should demand it for your project.
The Root Cause: Why Does Porosity Happen?
To solve the problem, you have to understand the chaos inside the mold.
In standard HPDC, molten aluminum is shot into a steel mold at speeds up to 100 m/s. The cavity is full of air. As the metal rushes in, it mixes with that air, creating turbulence.
If that air cannot escape through the vents before the metal solidifies, it gets trapped. This results in Gas Porosity.
The Symptom: Small, round voids revealed during machining or X-ray.
The Result: Leaking under pressure, blistering during heat treatment/powder coating, and structural weakness.
The Solution: Vacuum Die Casting Explained
Standard venting relies on the pressure of the metal to push air out through small gaps (overflows). It’s passive and often insufficient for complex geometries.
Vacuum Die Casting is active.
We connect a powerful vacuum system directly to the mold. In the critical milliseconds before the metal injection shot occurs, the system evacuates the air from the mold cavity and the shot sleeve.
The Technical Advantage:
Reduced Backpressure: The metal enters a near-vacuum space, reducing resistance.
Less Turbulence: With less air to displace, the metal flow is significantly smoother and more predictable, **approaching a laminar flow condition** and drastically reducing turbulence.
Higher Density: We can achieve significantly lower gas content, making the parts denser and stronger.
When Do You Actually Need Vacuum?
As a pragmatic vacuum die casting manufacturer, we will be honest: Not every part needs vacuum. It adds cost to the tooling and the process.
However, you must specify vacuum die casting if your part falls into these categories:
1. Pressure-Tight / Leak-Proof Parts
If your component is a pump housing, a valve body, or an automotive fluid connector, porosity is a functional failure. Vacuum casting is the only reliable way to pass IP67 or high-pressure leak tests consistently.
2. Heavy Post-Machining
If you plan to machine deep into the casting (removing the dense outer “skin”), you are exposing the core. With standard casting, the core is where porosity hides. Vacuum casting homogenizes the density, so you don’t hit air pockets during CNC milling or boring.
3. Surface Finishing Requirements
Are you planning to Chrome Plate or Teflon Coat the part? Trapped gas expands when heated during the curing or plating process, causing the surface to bubble or blister. Vacuum casting minimizes this trapped gas, ensuring a flawless cosmetic finish.
4. Thin-Walled Structural Parts
For large, thin parts (like telecom housings or EV battery trays), the metal needs to travel long distances without freezing. Vacuum helps draw the metal into blind spots and thin ribs that standard pressure cannot reach.
The Sureton Approach: Simulation + Execution
Buying a vacuum machine is easy. Using it correctly is hard.
At Sureton, we integrate vacuum technology with Mold Flow Analysis.
Before we cut a single piece of steel for the tool, we simulate the injection process. We identify exactly where the air traps are likely to occur and position our vacuum valves at those critical “last-to-fill” locations.
The Result?
Scrap rates reduced from industry averages of 5-8% down to <1%.
Consistent density for CNC machining.
Reliable supply chain performance for our global OEM clients.
Stop Gambling with Quality
If you are tired of seeing “Swiss cheese” inside your aluminum parts, it’s time to upgrade your process.
Contact Sureton today. Send us your 3D files, and our engineers will review whether Vacuum Die Casting is the right solution for your specific application. Let’s build parts that are solid to the core.
