What are Greensand Castings?
Greensand Castings are made by using wet sand, also known as greensand molds. The sand is not actually green in color nor do these molds require the use of what we call greensand, which is a greenish color sandstone. What this refers to is sand that is used before it dries out and still has moisture in it when molten metal is poured in the mold. It’s called greensand as a reference to greenwood. What gives the sand moisture and helps the sand stick together when making molds is the bentonite clay which is used as the binder and is mixed in the sand. By mixing this clay and greensand together, the result is strong molds that can be created on an automated assembly line.
Greensand consists of silica sand, about ten percent bentonite clay, between two and five percent water and about five percent sea coal which is used as an additive to improve casting finish. It’s important to know which type of metal is being cast in order to determine which additives and what gradation of sand should be used.
What products use greensand casting?
Roughly 42% of all parts cast in the United States are made using greensand molds. Greensand castings are the way that many ship parts are made as well as auto parts such as:
– pump housings
– engine blocks
– cylinder heads
– machine tool bases
– engine manifolds
– lever arms
– electrical contact parts
– machinery parts
– landing gear parts
What are the advantages of using greensand castings?
Speed and affordability are two of the reasons that greensand castings are so popular. Greensand castings molds can be made quickly and at low costs through automated making these casting economical and popular for making medium to high volume castings.
Another advantage of greensand castings is that they can also make large castings. While commonly these castings are in the 1- 500-pound range however these castings can be as large as 7,000 pounds.
Are there disadvantages to using green sand molds?
Greensand casting is not a good choice for very large castings. For extremely large castings, other casting methods should be chosen. Greensand castings can be limited in size because of the compaction required in making the mold.
Another issue is that greensand molds castings do not have as tight a tolerance as some other mold types. This means if you have castings that require tight tolerances or precise dimensions, greensand castings may need a little more machining than other forms of molds. It is also true that some other casting processes may render a better or smoother surface finish.
How are Greensand Molds Made?
Greensand is loaded into a mold maker and then a pattern is pressed into the sand. The pressure created when pressing the mold into the sand creates the desired form.
After the casting is created, the sand is done with and cannot be used for future castings without the expensive process of separating out the materials. It’s far cheaper to start fresh with new sand.
At Faircast Inc. we offer multiple types of castings and specialize in grey and ductile iron. Our knowledgeable and friendly staff is ready to answer all of your questions. We will have one of our engineers to meet with you to discuss your needs and work with you to complete your project. We are capable of producing almost any casting needed. Contact us for more information or to set up a time to meet with one of our engineers and get the ball rolling.