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Die casting is a metal casting process that involves injecting molten metal into a die using high pressure. Die casting facilitates the production of hundreds or thousands of pieces with high dimensional accuracy and a good surface finish, making it highly economical; however, maintaining quality and consistency at such high volumes comes with its own challenges. Manufacturers need to account for porosity, or the tendency for die castings to have voids or holes that cause surface-level flaws. Read on to learn more about die casting porosity, problems it can cause, and how vacuum impregnation seals die casting porosity.
What Is Die Casting Porosity?
Die casting porosity refers to specific defects found within the casting. Two of the most common types of porosity in completed metal goods are gas porosity and shrinkage porosity. Gas porosity is often caused by trapped air or other gases during solidification. It is always buoyant, meaning the resulting bubbles are typically found near the top of the casting (as seen below).
Shrinkage porosity, on the other hand, refers to internal voids that can form as the metal cools. This is because the solid metal volume is less than the volume of liquid metal at higher temperatures. Shrinkage porosity has a linear or jagged appearance and tends to occur in either the drag or cope portion of the casting (below the surface).
In addition to the above, having too much die lube can also contribute to porosity in die casting. While die lube is essential for removing cooled goods from the molds, too much can interfere with solid formation and create surface-level flaws.
Why Is Porosity a Problem?
While porosity is inherent in die casting manufacturing, it can impact part performance, especially in applications where pressure integrity is a vital characteristic. Far from just being an aesthetic or durability problem, die-cast porosity can lead to early breakdowns or even failures. Consider the following examples:
Blind Porosity
Blind porosity creates gaps that sit along the surface, pushing slightly into the interior but not creating uninterrupted passages for liquid to seep in. Manufacturers can expose blind porosity during the finishing stages. While it doesn’t make goods mechanically weaker, it does increase the risk of corrosion. The pores can also hold onto cleaning chemicals from powder coating or anodizing pre-treatments and then leach out after treatment, causing blemishes on the surface.
Through Porosity
Through porosity creates a leak path that runs through casting walls, or can be exposed after machining. This can weaken the metal and make it unsuitable for applications that require excellent pressure tightness, such as automotive and marine applications. Through porosity may make components weaker, create failure points, and prevent parts from reliably holding fluids.
Fully Enclosed Porosity
These pores are completely enclosed and don’t create leak paths. However, fully enclosed pores can become problematic if they’re exposed during surface finishing.
How to Fix Die Casting Porosity
Manufacturers can significantly reduce or completely eliminate failures due to die casting porosity with the right equipment and processes. One of the most effective methods is vacuum impregnation. With this controlled method, manufacturers use vacuuming and pressure to introduce the impregnating material into the voids, sealing the voids to make the casting fit for pressure-sensitive applications.
Benefits of using die casting vacuum impregnation include:
- A fast, cost-effective seal that doesn’t impact the component’s physical properties or functionality
- No residual contamination or leaching
Manufacturers can use vacuum impregnation for castings of any size, creating a permanent seal as well as a more consistent look, feel, and functionality in finished products.
Why Godfrey & Wing Is the Trusted Solution for Die Casting Porosity
At Godfrey & Wing, we specialize in closing the gaps left by die casting processes. Our equipment can provide fast, cost-efficient, and thorough vacuum impregnation processes to address porosity in die casting manufacturing. We’re committed to building systems that create effective, reliable seals that meet or exceed OEM requirements, and our team has decades of experience researching and improving solutions for die cast porosity.
Contact us today to learn more about our products and services.
Godfrey & Wing, a leading global manufacturer of vacuum impregnation technology, has received a contract for an Advanced Graphite Impregnation (AGI) system from a hydrogen fuel cell manufacturer. Starting in 2023, the system will seal leak paths in bi-polar plates in fuel cell stacks for fuel cell vehicles (FCV).
The AGI is designed from Godfrey & Wing’s , which is the world’s most widely used impregnation system. While the HVLV was originally designed to seal leak paths in die cast aluminum, the AGI seals leak paths in graphite parts. A modular system, the AGI seals graphite leak paths while keeping parts clean. With a small footprint of 116 square feet, it can fit in the production line to achieve continuous production flow. In addition, the AGI will be equipped with custom fixtures to remove the risk of part damage and contamination.
While FCVs operate on electricity and are zero-emission, they do so differently than battery-powered Electric Vehicles (EV). In an FCV, hydrogen reacts electrochemically to produce electricity to power the vehicle. Hydrogen fuel cells are designed for use in industries such as transportation, construction, industrial equipment, and others that have traditionally relied on internal combustion technology.
“With a proven record in delivering results for ICEs, we are helping OEMs and manufacturers succeed as they now invest in FCV and EVs.” Said Johnny Halladay, Business Unit Director. “OEMs are moving at a fast pace to build better and cleaner cars. We are excited to help these companies meet their demand.”
Hydrogen infrastructure is growing across North America, and fuel cell transit buses are already in use in the United States and Canada. The global market for fuel cells was valued at $6.6 billion in 2021, according to BCC Research, and is expected to grow at a 20.1% CAGR from 2022 to 2027.
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When it comes to vacuum impregnation, it’s essential to ensure that the parts being impregnated are dry beforehand. This is because any surface impurities can interfere with the impregnation process, leading to subpar results.
If any residual fluids or debris are on the parts prior to impregnation, then the following problems may occur.
Vacuum Pressure Impregnation (VPI) is a method to insulate wound electro-mechanical parts thoroughly with a resin or varnish. VPI is a critical process to insulate and seal the porosity of the parts. VPI is essential to ensure that parts function correctly and improve the longevity of the equipment (Image 1). This blog is a guide that will explain the process, advantages and applications of VPI.
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The phrase aluminum die casting porosity is used extensively when talking about any void in an aluminum casting, but it does not describe the actual problem. It can take many different shapes and forms, but it is often described just as “porosity”. When analyzing a casting’s porosity, it is important to describe specifics like size, shape, location, and frequency (Image 1). Since porosity is within the casting’s walls, the best way to analyze it is through Nondestructive Testing.
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One component that engineers are designing in electric vehicles (EVs) is the electric motor. This component is one of the main driving-forces behind EVs. Per IDTEchEx, over 100 million electric motors will be required by 2032. The EV market is constantly evolving with new designs and higher performance requirements to meet these consumer demands. These requirements can result in more parts being rejected and scrapped. Leading to increased costs, and delayed production.
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Electronics play a crucial role in electric vehicles (EVs). In 2000 automobile electronics were responsible for 18 percent of the cost of a car. Twenty years later, electronics accounted for 40 percent of a car’s cost. The use of electronics will continue to meet fuel efficiency, safety regulations, and consumer standards. However, while the use of electronics will grow, manufacturers must ensure their parts’ quality, safety, and their bottom line’s integrity.
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When 3D printing was first developed in the 1980’s, it was primarily used for a product’s proof of concept or initial prototypes. The limits of the technology and material did not allow one to use the process for field testing, or production. The past decade has seen a surge in 3D printing use. The rapid developments in 3D printing technology and materials has accelerated areas like product development, offer customized product, and eliminate design restrictions.
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The increased use of turbochargers has become an important trend in car manufacturing. This trend has been driven by requirements to design smaller, more powerful engines that also reduce fuel consumption.
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