Frequently Asked Questions
Q. Why choose a casting?
A. Casting is an economical method for producing components. It's also very versatile. Foundrymen have at their disposal many different methods that allow for the casting of "near net" complex metal shapes. The resulting castings may require little or no additional secondary processing prior to use.
The methods of casting production currently used in the foundry industry include sand mold casting, permanent mold casting, lost foam casting, lost wax molding, centrifugal casting, continuous casting, and pressure die casting.
Each of these methods are uniquely suited for the production of specific kinds of castings.
Q. How do I choose which method to use for my product?
A. Although a foundry may utilize more than one casting process, this choice is usually dictated by the class of product to be made and by the relative economies of the various processes.
Factors that must all be taken into account to select the most appropriate casting process include:
- casting size
- surface finish
- dimensional accuracy
- required alloy properties
With modern alloys and continuing advances in casting technology, Riverside Brass is finding ways to bring improved production economies to an ever-widening range of product applications.
Q. What molding method does Riverside Brass use?
A. Riverside Brass specializes in the green sand molding process exclusively.
Our facility is equipped to produce medium to high volumes of high quality castings in copper, aluminum and zinc based alloys.
With our recent process innovations, Riverside is able to produce extremely precise castings that achieve excellent precision and economy with little to no need for further finishing.
Q. What is green sand molding?
A. The green sand process utilizes a molding aggregate whose sand grains are bonded together with clay which has been plasticized by the addition of controlled amounts of water.
It is the presence of this "temper" water in the sand/clay mixture which causes the molding aggregate to be called green sand, as distinct from dry sand.
Q. How are green sand molds made?
A. Green sand molding consists of compacting the tempered sand around the pattern by one or more mechanical means.
Compaction methods can include "jolting", squeezing, ramming, or vibrating.
The plasticity (greenness) of the bonding clay is sufficient to produce a mold which is rigid enough to hold its shape during pattern removal, core placement, pouring, and solidification.
At Riverside Brass we use olivine sand exclusively as our green sand molding media.
Q. What is olivine sand?
A. Olivine is a magnesium-iron orthosilicate, (Mg,Fe)2SiO4, consisting of a solution of the two minerals forsterite (Mg2SiO4) and fayalite (Fe2SiO4) in approximately equal proportions.
The mineral is the primary constituent of a rock called "dunite", found principally in the states of Washington and North Carolina.
Dunite must be crushed and washed to permit gravity separation of mineral impurities, mainly serpentine and talc. The crushed material, now the consistency of sand, is then dried and screened into different grades of fineness.
As a crushed material, the grains of olivine are angular and somewhat cracked.
Q. Is olivine sand better for casting than silica sand?
While olivine sand is more expensive than other types of molding sands, it has several advantages over the silica sands commonly used in the foundry industry.
One advantage is the health benefit: by replacing silica sand with olivine, there is no silica dust in the molding area, which has been linked to lung damage.
Olivine also exhibits one third of the thermal expansion compared to many other sands. This results in greater dimension stability or tighter casting tolerances. In some cases, this can allow customers to use green sand casting instead of more costly processes and to reduce the cost of finishing parts that have been cast.
The third major advantage that olivine provides is a better cast surface finish.
We believe that these advantages to our customers easily offset the increase in the initial purchase price of our molding sand.