Comments Off on Video: When Should I Impregnate a Casting
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.
Comments Off on Should Porosity Be Sealed Before or After Machining?
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. Vacuum impregnation is a proven process that seals internal porosity without impacting any other features of the manufactured part. A common question asked about vacuum impregnation is “Should vacuum impregnation be done before or after die casting machining?”
Porosity
While some refer to porosity as a defect, it occurs naturally and is found in most materials, both man-made and in nature. In metal castings, porosity is typically considered any void found in the casting. Some metal casting porosity can affect the part’s structural integrity, creating a failure point. More commonly, porosity prevents the part from being pressure tight. This will impact performance if the part is designed to hold gases or fluids.
Casting porosity can be caused by gas formation or solidification while the metal is being moved from a liquid state to a solid state. This porosity can range in size, from sub-micron to voids greater than 10 mm, depending on the casting.
In general, there are three casting porosity classifications:
Blind Porosity: From one surface only and therefore not forming a continuous passage for liquid (highlighted in blue in figure 1).
Through Porosity: Stretching from one side of a casting to another (highlighted in red in figure 1).
Fully Enclosed Porosity: Enclosed within the casting, and has no passage to the surface (highlighted in green in figure 1).
Figure 1: There are three types of casting porosity: blind porosity, through porosity, and fully enclosed porosity.
Blind and through porosity cause immediate casting problems. Blind porosity can cause internal corrosion; while through porosity will create a leak path and allow gas and liquids to seep through the casting (Figure 2). In addition, blind porosity can cause defects on the part surface when secondary treatments, like powder coating or anodizing, are done. This is because solutions used to clean the castings prior to the treatment will leech out of the voids after the surface finish process.
Should Porosity Be Sealed Before or After Machining?
Figure 2: Blind porosity can cause internal corrosion; while through porosity will create a leak path and allow gas and liquids to seep through the casting.
When a machine tool cuts into the surface or “skin” of a casting, it can expose or open porosity (Figure 3). The porosity may be either blind porosity or existing blind and enclosed porosity may be opened and become through porosity.
Figure 3: When a machine tool cuts into the surface or “skin” of a casting, it can expose or open porosity.
The new inter-connected porosity (highlighted in green) will create a leak path (Figure 4). The leak path will cause fluids and gases to leak from the casting, causing it to be non-conforming, and in many cases unusable. Unfortunately, this occurs precisely at the wrong time, since the non-conforming part has already been cast, cubed (pre-machined), washed, tested, shipped, fully machined, washed and tested again. All the value has been added to the non-conforming part. In the worst-case scenario if the problem occurs frequently, the manufacturer may have maxed-out their production and may be unable to replace the non-conforming castings with functional parts, delaying shipments and significantly increasing costs.
Figure 4: The new inter-connected porosity (highlighted in green) will create a leak path. This leak path will cause fluids and gases to leak from the casting, causing it to be non-conforming, and in many cases unusable.
Impregnating 100% of castings after final machining is the best way to insure leak free castings at build. If prior to assembly, a final leak test of individual parts is incorporated into production, leak testing fully machined casting and impregnating only the non-conforming parts (often referred to as fix-on-fail) is an excellent alternative.
Another approach is that manufacturers have chosen to increase the machining content at the pre-machine stage (cubing) thus maximizing the exposure of blind and through porosity prior to the parts reaching the final production line. After pre-machining 100% of all parts are impregnated and tested. Only conforming parts are sent through to production when the parts are fully machined in production only a reduced amount of material is removed. Since the impregnation at pre-machining has already sealed both the blind and through porosity, the opportunity to open an interconnected leak path is substantially reduced. In some cases, any non-conforming parts that make it to final test can be easily impregnated without disrupting production on a “fix-on-fail” basis.
In Summary
Because machining may potentially uncover additional casting porosity, vacuum impregnation should be done after machining. Performing vacuum impregnation after machining is the only way to seal all leak paths. However, some castings may be pre-machined or cubed. Impregnating 100% of production castings after cubing will seal the exposed porosity. In this case, impregnation is still very effective in reducing non-conforming parts at final assembly.
Comments Off on Article: Vacuum Impregnation Enables Lightweight Material Use
Godfrey & Wing has published an article in LightWeighting World titled “Vacuum Impregnation Enables Lightweight Material Use”. This article discusses the surge in aluminum use and how vacuum impregnation eliminates aluminum casting porosity. You can read the entire article below.
Recent decades have seen a surge in use of aluminum castings in car manufacturing. Aluminum has been a key 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 later1. Since this time, aluminum has become the leading material used in various components and car models. Aluminum use now ranges from mass-market to luxury vehicles.
As this surge has happened, vacuum impregnation has become the primary method to eliminate the porosity inherent in aluminum castings. OEMs are redesigning parts and bringing vacuum impregnation systems in-house to meet the aluminum use demand.
Comments Off on Video: How Godfrey & Wing’s Equipment Works
Godfrey & Wing’s vacuum impregnation equipment is the best in the world. The equipment re-imagined vacuum impregnation by making it safer, increasing production and eliminating casting defects. But how exactly does it work? Watch this animation video.
Comments Off on Understanding the Vacuum Impregnation Process
Vacuum impregnationseals porosity and leak paths in metal castings and powdered metal parts that form during the casting or molding process. The process is done by filling the pores with a sealant under pressure to stop fluids or gases from leaking under pressure. Vacuum impregnation stops casting porosity and allows manufacturers to use parts that would otherwise be scrapped.
Comments Off on Top 5 Vacuum Impregnation Blogs of 2016
It is the end of another year. Which means that it is time to address our mixed feelings about New Years
resolutions, and reflect on the year that is about to end. While we cannot help with your 2017 resolutions, we
can look back on the most read vacuum impregnation and porosity blogs of 2016. Here are our top 5 blogs from
2016.
3 Types of Porosity Classification
When a porosity problem occurs, the first challenge
is to determine the type of porosity. The following
porosity classification guide can help you determine
the porosity type.
Vacuum Impregnation FAQ
When a customer has a casting with porosity that is leaking,
they need a solution quickly. Here are some of the more common
questions that we receive in regards to vacuum impregnation and porosity.
Understanding Vacuum Impregnation (Handbook)
Casting impregnation stops leaks caused by porosity.
It is important to understand what vacuum impregnation does not do.
Advanced Powertrain Impregnation (Video)
The Advanced Powertrain impregnation (APi) system simplifies
and compacts the vacuum impregnation process for parts like
engine blocks or powertrain transmission cases.
Next year, we will continue to write insightful and helpful content on vacuum impregnation and porosity. Don’t worry,
our 2017 blogs will not require gyms or special diets. They will help you understand vacuum impregnation and solve
your porosity problems.
Comments Off on Understanding Vacuum Impregnation (Handbook)
We recently update our vacuum impregnation handbook. The handbook takes the complicated subject of vacuum impregnation and simplifies it. This handbook will allow you to better identify porosity and then learn what vacuum impregnation process and system is best to seal your porosity.
When porosity occurs in your part, you need to get it seal quickly.Use our handbook as a guide to help you find the best solution for your part. Flip through this easy to follow handbook to learn about:
Comments Off on CFi Vacuum Impregnation System Creates Competitive Advantage
The Albert Handtmann Metallgusswerk GmbH is the largest lightweight (aluminum) foundry in Germany. When the opportunity arose for the company to cast and machine one third of the entire world production of transmission cases and clutch housings for Mercedes Benz, not just any vacuum impregnation system would work.
They needed a vacuum impregnation system to meet:
-Stringent Quality Standards -High Production Volumes -Meet a Tight Cycle Time -Fit in a Confined Space
To learn how Godfrey & Wing played an integral role in Handtmann’s manufacturing process, click here to read the entire case study.
Comments Off on What is the lifespan of your vacuum impregnation system?
Is it more cost-effective to repair your existing vacuum impregnation equipment or to purchase a new system? There are many factors to consider when making this decision.
Comments Off on Don’t Hesitate to Use Vacuum Impregnation
I often meet with potential customers who are hesitant to implement a vacuum impregnation process for a variety of reasons. In this article, I will discuss the most common reasons as well as provide some explanation as to why and how a vacuum impregnation program can benefit your business.
