When it comes to sand molding, Green Sand is definitely the most diversified of the molding methods that bare in use today. The term green however does not quite denote what most people might expect- it is simply a reference to the fact that there is moisture present in the molding sand and that it is not a dried or baked mold since the latter does not usually have any moisture within it. Green Sand is typically composed of a large proportion of sand, usually silica, mixed with water, pulverized coal and bentonite clay. The clay is normally added according to different recipes and is useful in order to help strike the proper balance between surface finish, mold ability and how the molten metal is going to be able to degas. Because of the simplicity of the nature of the materials that are used in the process, sand casting remains the cheapest method of casting metals and it has the reputation of being one of the earliest forms of casting to be practiced on a commercial scale.
How it is made
The first step in the process involves making the mold material and this is done by mixing silica sand with clay as the bonding agent and water. The mold is then shaped by placing a metal frame or wooden flask over the pattern so that a cavity is produced that represents one half of the casting. The next step is compaction of the mold and this can be achieved by either squeezing or jolting it. Using the same procedure, the second half of the mold is then produced and then the complete mold can be formed by placing the two flasks together.
In the event that the casting produced happens to have some hollow sections, a core can be used and this core is usually made of clay that has either been chemically hardened or baked. This process, however, is mostly used in small scale sand casting. Large sand casting companies, such as Gamma Foundries, normally use sophisticated equipment to do the job more efficiently on a large scale but the underlying principles remain the same.
Because the molds made in the manner described above can be poured without the need for any further conditioning, green sand has grown to become one of the most popular of the sand casting methods used today. Of course, there are many variations of the molding process and they will depend on the sand casting foundry you choose to go to. Some of the more common variations of green sand molding include the following;
• Skin dried molding
• Flaskless molding
• High density molding
• Tight flask molding
• Dry sand molding
Other advantages associated with Green Sand molding include low material and pattern costs, adaptability to small and large quantities, almost limitless in terms of shapes, weight or size of parts and the fact that it can be used for most ferrous and non-ferrous metals. On the downside, it has reduced dimensional accuracy and low complexity in terms of design.
About the Company
Gamma Foundries proudly provides its clients with access to 3D printing sand casting services. The company is one of Canada’s largest sand casting foundries, serving clients across the country and globe with design, development and production services. From single prototypes and one-offs to orders in the thousands, the company is equipped to deliver.