The inner workings of an aluminum foundry are quite complex. There are 6 major components to running a successful aluminum foundry. We’ll talk about each of those components and what their role is in a foundry.
- The metal
- The sand
- The equipment
- The quality system
- The safety system
- The employees
The Metal – Aluminum Alloys
Most successful aluminum foundries pour more than one alloy. An alloy is a substance that combines more than one metal or a metal and a non-metal. The most common alloys poured by most foundries today are either 319 alloy or 356 alloy, both aluminum-type alloys, each made up of their own unique compositions. Both of these very common alloys have different strengths and weaknesses as far as tensile strengths and mechanical properties.
319 does not need any heat treatment to fulfill its mechanical properties. It’s corrosion-resistant, easily welded, and has high mechanical properties. 319 can also ‘self-age’ and is at its optimum strength within two weeks of being cast. 356 on the other hand, needs to be heat-treated to achieve its full mechanicals and improve its strength. Thus, 356 is a higher-cost alloy. Foundries need to be competitive but also attractive to new customers. They do so by offering several alloys on their daily pour menu. However, this introduces the chance of contamination between alloys. For example, here at Precision Enterprises, we currently have 8 dedicated furnaces to avoid cross-contamination between alloys. Once the alloys are mixed in a furnace, and the furnace is not purged and used for another dissimilar alloy, all metal coming out of that furnace is contaminated.
We go one step further by marking the gates and risers as to which alloy is being poured so that even the re-melts are controlled. Some castings we pour are permitted by our customers to have a certain percentage of remelt allowable. These are non-critical castings. Most of this ‘scrap’ type of aluminum from the actual molding process is sold back to our smelters to be recycled and smelted again into prime alloy.
All of our metal needs to be degassed prior to the pour. This means we purge our metal with a gas called Argon to capture any water molecules or impurities in the molten metal. Precise temperature monitoring is critical to this stage of the melt. Each alloy has its own temperature range and is also dependent upon the shape and size/weight of the final casting itself. This process of degassing before each pour is critical to produce high-quality aluminum castings.
The Sand – Sand Casting
The sand is what the metal is poured into that creates its final shape while cooling and solidifying the metal. This is where we get the term sand casting. The sand is critical in determining the surface smoothness of the casting. Sand can be ordered by grit. Then, we add binders and water. The mixture of each determines the outcome of the casting. Too much water in the sand can introduce porosity into the metal. Porosity in sand casting is just a fancy term for a defect that happens if something, usually gas or air, gets stuck and causes a bubble in the metal during solidification. Too little binder can cause flaws in the casting surface. Precision Enterprises has invested in a quite complex computerized sand system that allows us to change the parameters on a job-to-job basis. A 100-pound aluminum sand casting with thick heavy walls needs a higher moisture content than a 2-pound thin wall casting, and so on. We can change the sand in our whole foundry with a few changes to the computer.
All of our jobs track the prior run success of the casting, record the optimal settings from the last run which also includes the temperature and humidity from that last day’s run, adjust for the present day’s run, and change the necessary parameters.
Who knew sand could have so many aspects that require constant monitoring to operate a successful foundry?
The Equipment – Molding Machines
The equipment can be as old as or as new as whatever the foundry can possibly invest. The newest equipment is also the most expensive. Here at Precision, we run Sinto automatic molding machines. These are high-production molding machines that can produce several hundred molds per day, meaning thousands of castings.
Sinto automatics can hold tighter tolerances and better finishes on cast surfaces than most of the other molding methods. They are also more consistent, part-to-part.
We also have squeezer lines, rotolift, and cope and drags for larger castings. Precision Enterprise can run just about any pattern that we inherit. If not, our in-house engineering team can produce a pattern from reverse engineering or a new pattern from your CAD files.
The Quality System
Precision Enterprises is ISO-certified. That basically means that we have a quality system in place, that is internationally recognized for our type of manufacturing. Our high standards in quality control procedures enable us to confidently run a casting today, and way into the future and get the same results we did the last time we ran that part. Each stage of our process is certified for success. Each process is measured and recorded. And we are audited yearly to keep our certification, part-to-part consistency, over time, and repeatable.
The Foundry Safety System
Safety is the most important. Working around machinery and alloys that reach temperatures of 1,400 degrees Fahrenheit is a serious matter. OSHA audits us regularly. Precision Enterprises goes way beyond what is the basic requirement from OSHA. We work on this daily, with continuing education on everyone’s part.
The Aluminum Foundry Employees
Over the last 5 years, this has been a high-level challenge for any foundry here in the States. On the one hand, all our customers need us keep our overheads low, but still be able to attract and hire new talent. On the other hand, our hourly rate has skyrocketed over the past few years, as I am sure is happening with all foundries.
To counteract the increase in pirates, we have begun to look at robotics to alleviate the repetitive work, such as grinding castings, and still offer jobs that our people can turn into much-needed skills as they move forward into foundry careers.
We cherish our employees and try to supply them with an exciting job, different from most, but especially safe. We cannot do any of this without them.
Aluminum Casting Foundry Recap
There are fewer aluminum foundries today than there were just 10 years ago. That concerns me. As you can see, it is not an easy business, especially one that you want to be an expert at. You must know all there is to know about metal alloys, the best casting methods, which equipment to use, how to measure quality, and most importantly how to always keep valuable employees safe. We’ve been doing it for three generations, that’s more than 70 years, here at Precision Enterprises and we’re still growing. We’re proud to be one of the best aluminum foundries in the country. Check back often for more updates on how foundries work, to learn more about casting methods, alloys, machine molding, and more.
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