The Metal Casting Process Explained

What is Metal Casting?

Metal casting is a modern process with ancient roots. In the metal casting process, metal shapes are formed by pouring liquid metal into a mold, where it is cooled and later extracted from the mold. Metal casting is arguably the earliest and most influential industrial process in history. It’s used to make many metal objects used in our daily lives: automotive parts, train wheels, lamp posts, school bus pedals, and much more. Plus, metal casting foundries rely on metal recycling as a cost-efficient source of raw material, significantly reducing wasted scrap metal that might end up in landfills.

The History of Metal Casting

The oldest known metal casting is that of a copper frog, believed to have been produced in 3200 BCE in Mesopotamia. Later, around 2000 BCE, iron was discovered. But it was not until around 700 BCE that the first production of cast iron was developed in China. The sand molding process of casting metals was also invented in China in 645 BCE.

The crucible process, a technique used for producing fine or tool steel, appeared and disappeared in various locations around the globe since the early 1st millennium CE. The technique popped up in India and central Asia first, until it appeared in northern Europe around 800 CE, where it was used to make Viking swords. The technique didn’t resurface until 1750 when Benjamin Huntsman reinvented it in England. Huntsman heated small pieces of carbon steel in a closed crucible, which is a ceramic pot with refractory properties that can withstand a high degree of heat. Huntsman achieved a temperature high enough to melt steel for the first time.

Over the past thousands of years, the casting of metals into usable objects has evolved to become more exact and automated, but the process at its core has essentially remained the same. Innovations in automation of foundry processes like the General Kinematics’ VIBRA-DRUM® Sand Casting Conditioner have made processing large quantities of castings easier as well as improved the quality of castings.

The Metal Casting Process

1. Patternmaking – A pattern is a replica of the exterior of the casting. Patterns are typically made of wood, metal, plastic, or plaster. Patternmaking is incredibly important for industrial part-making, where precise calculations are needed to make pieces fit and work together.
2. Coremaking – If a casting is hollow, an additional piece of sand or metal (called a core) shapes the internal form to make it hollow. Cores are typically strong yet collapsible so they can be easily removed from the finished casting.
3. Molding – To visualize the metal casting process so far, imagine yourself walking on the beach toward the ocean. Look at a footprint you leave behind in the wet sand. Your foot would be the core, and the impression left in the sand is a mold of your foot. Molding is a multistep process that will form a mold around the pattern using molding sand. In casting, a mold is contained in a frame called a flask. Green sand, or molding sand, is packed into the flask around the pattern. Alternatively, a two-piece, non-destructible metal mold is created so that it can be used repeatedly to cast identical parts for industrial applications.
4. Melting and Pouring – After liquid metal is melted, it is poured into the mold and left to solidify. Once solidified, the shakeout process begins: the molds undergo vibration to remove sand from the casting. In industrial applications, equipment like our Two-Mass Shakeouts keeps production output high because of its efficient and smooth performance. Removed sand is typically collected, cooled, and reclaimed to be used once more in future castings. The VIBRA-DRUM® Sand Casting Conditioner improves this process of sand separation from castings by removing and cooling sand and castings, while alleviating the casting damage that is common during this point of the process.
5. Cleaning – In this final step, the cast metal object is removed from the mold and then fettled. During the fettling, the object is cleaned of any molding material, and rough edges are removed.

The VIBRA-DRUM® Sand Casting Conditioner excels at cooling, equalizing, and reclaiming sand from castings. The machine is revolutionary in its high volume mold and sand handling for foundry applications. It gently tumbles the sand off of castings, while simultaneously cooling sand temperatures and evaporating moisture. The end results are a clean cast and sand ready for the reclamation process.

Modern Day Castings

Today, nearly every mechanical device we use, from automobiles to washing machines are manufactured using metal parts that were created in the casting process. The difference between today’s cast metal products and those that were manufactured even 100 years ago is the precision and tolerances that can be achieved through the computerized automated design process, and modern methods for producing the detailed cores and molds.

Throughout the centuries, various combinations of raw materials have been developed to produce various metal types. Some cast products are used in engines that require a high tolerance for heat and cold. Cast iron pipe must resist corrosion and high pressures. Other cast parts must be lightweight but durable. In many applications, parts are designed to allow for precise tolerance between expansion and contraction. The advancement in the quality of cast metal products starts with the quality of the mineral product itself.  

Proud to serve the Foundry Industry

General Kinematics is proud to be a leading manufacturer of automated vibratory processing equipment that has innovated alongside the foundry industry for nearly 60 years. To get more information about all of the General Kinematics foundry equipment, contact us today!