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Tag Archive: Casting Impregnation

1. Correcting Three Vacuum Impregnation Myths

   November 25, 2019 2:43 pm Leave a Comment

   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.

   

   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.

   

   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.

   

   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.

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2. Video: When Should I Impregnate a Casting

   June 20, 2019 12:50 pm Leave a Comment

   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. 

   

    

   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.

   

   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.

   

   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. 

   

   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.

3. Vacuum Impregnation Economics

   February 18, 2013 7:14 pm Leave a Comment

   The primary purpose of vacuum impregnation is to seal porous castings and prevent leakage. If the impregnation process is not efficient and fails to seal the casting it will become scrap, and the number and value of these failures will determine the economic viability of the process.

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4. Old vs New Vacuum Impregnation

   September 17, 2012 4:35 pm Leave a Comment

   The other morning I was walking the dog around 5:00 AM, and I noticed how exceptionally crisp and brilliant the stars were in the pre dawn sky, shining though the high pressure system overhead. While finishing the walk around the neighborhood, I thought about mankind’s worldview that the earth was flat as recent as 600 years ago and the reluctance of decision makers of that time, influenced by the rhetoric of naysayers, to accept anything other than the status quo.

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