Tag Archive: Vacuum Impregnation

  1. How to Seal Die Casting Porosity?

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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.

    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).

    Shrink Porosity

    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).

    Gas Porosity

    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.

    Casting Sectioned Porosity Rev1

    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.

  2. Preparing Parts for Vacuum Impregnation

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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.

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  3. Three Reasons to Seal Electronics with Vacuum Impregnation

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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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  4. How Vacuum Impregnation Enables Lightweighting

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    Recent decades have seen a surge in the use of aluminum castings in car manufacturing. Aluminum has been a critical material in car manufacturing since the beginning. The first sports car featuring an aluminum body was unveiled at the Berlin International Motor Show in 1899. Carl Benz developed the first engine with aluminum parts two years later. Since then, aluminum has become the leading material used in various components and car models. Aluminum use now ranges from mass-market to luxury vehicles.  

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  5. Cost of Vacuum Impregnation

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    Manufacturers are constantly faced with either scrapping castings that leak or sealing the castings through vacuum impregnation. Some may perceive vacuum impregnation as a non-value added cost and assume it is less expensive to scrap die castings that leak. In this simplified yet real-world example, we will review the costs of die casting scrap compared to vacuum impregnation.
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  6. Sealing Electronics with Vacuum Impregnation vs Potting

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    The use of electronics in automobiles has made cars faster, safer, and more reliable. Electronics have become so prevalent that they’re practically a commodity in the same way that aluminum and steel are. As this trend continues, manufacturers need solutions that address the leak paths that occur naturally in the manufacture of these components.

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  7. How Vacuum Impregnation Supports Environmental Responsibility

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    Automotive manufacturers realize that being environmentally responsible and profitable are not mutually exclusive. Being environmentally responsible can achieve better growth, cost savings, improve brand recognition, and increase profitability. The environmental impact of the responsible use of resources is beneficial to everyone, and automotive manufacturers play a leading role.

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  8. Correcting Three Vacuum Impregnation Myths

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    In some die casting applications, components must also be pressure-tight to hold pressurized fluid or gases. Companies use vacuum impregnation to meet these requirements by sealing the internal leak paths caused by interconnected porosity.

    Misconceptions and lack of information about the vacuum impregnation process can hinder its implementation, which may increase unforeseen costs and negatively impact part quality. This piece demystifies vacuum impregnation by correcting three common myths.

    Myth: Vacuum Impregnation is a CoatingFact: The process occurs subsurface, with no residual sealant remaining on the part’s surfaces, machine features, blind holes, and taps. Only the sealant drawn into the leak path by the force of the vacuum and pressure remains in the casting.

    Vacuum Impregnation Not a Coating

    Myth: Vacuum Impregnation Causes Dimensional Changes to CastingsFact: Vacuum impregnation does not change the casting’s dimensions, thus allowing engineers the freedom to design and make parts to the net shapes. Since the vacuum impregnation process occurs subsurface, an engineer does not need to incorporate dimensional allowance.

    Vacuum Impregnation No Dimensional Changes

    Myth: Vacuum Impregnation is a Cork or PlugFact: Vacuum impregnation seals porosity deep within the leak path; it is not a cork or plug. In the case of visible or open porosity, low viscosity sealants will most likely be washed out of pits or holes. Thus, a casting with surface porosity or blemishes before the process will exhibit the same surface porosity and blemishes after the process. However, the leak path below the part’s surface is fully sealed.

    Vacuum Impregnation Seals Porosity

    In Summary A clear understanding of how vacuum impregnation works can help companies maximize their production results. As the preferred method to prevent fluids or gases from leaking under pressure, the vacuum impregnation process seals casting porosity that forms during manufacturing. When done properly, the casting will function so that fluids or gasses will flow only where needed while physical characteristics, simply stated, will not be different in any manner. Vacuum impregnation helps manufacturers decrease the rate of scrapped parts, increase productivity, and ultimately increase their profitability.

  9. Can Vacuum Impregnation Seal Cracks?

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    In some die casting applications, components must also be pressure-tight to hold pressurized fluid or gases. Companies use vacuum impregnation to meet these requirements by sealing the internal leak paths without impacting any other features of the casting. A commonly asked question is in addition to leak paths, can vacuum impregnation seal cracks?

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  10. Video: When Should I Impregnate a Casting

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    The goal of a foundry is to produce high quality die castings that meet or exceed the customer’s specifications at a competitive cost.  In some die casting cases, those specifications require that the part must hold pressurized fluid or gasses. Companies use vacuum impregnation when the part must hold fluids or gasses under pressure. A common question asked about vacuum impregnation is “When Should I Impregnate a Casting?” This video addresses this question by answering if vacuum impregnation should be done before or after machining and finishing. 

    When Should I Impregnate A Casting

     

    Video Transcript

    Hey, everyone. Welcome to “Casting Call” with Johnny Impreg. This is a premiere episode of a video blog series where we hope to answer all your compelling questions of everything impregnation. We’re going to start with the question I think I hear most often from folks is, “When should I impregnate a casting?”

    Spoiler Alert!

    Now, spoiler alert, I’m going to give you the answer now in case you’re short on time. But you want to do the impregnation after machining and prior to any kind of finishing like plating or painting. 

    Types of Porosity

    Now, here’s why. Let’s consider the three different types of porosity you see in a raw casting—blind porosity, through porosity, wall to wall, and fully enclosed. If you impregnate a casting in this condition, you’ll get sealant in the blind. You’ll get it here, but you won’t get any sealant in this area. That becomes important when you do the machining, because when you machined from here, you’re going to have a leak path.

    Porosity Types Vlog REV2-1

    Now, if you do the impregnation after machining, you’ll still fill this and now you’ll fill this leak path as well. The reason you want to do it prior to finishing is you want to fill up all the porosity before you do the plating or painting. Otherwise, you could end up with out gassing or other blemishes that really don’t look so nice.

    Machining Porosity Vlog REV2

    Real World Example

    Let’s look at a real-world example on a cylinder block. Now, in this region here, we had a case where there was blind porosity going from here into the casting. It didn’t cause a problem until this machining cut was made. We have some other areas where we had enclosed porosity that was connected through two different machining passes. So, this is a real-world example of why you should do impregnation after machining. 

    Cylinder Block Porosity REV1

    So, I hope this little tutorial helped you. If you have any questions, please feel free to leave comments below and hit me up on WhatsApp or LinkedIn.