What is the shell formation?
Shell formation, also known as castings with a shell, is the process of creating and using resinous forms composed of thin -walled sections. The process is usually used to create small and medium metal parts. It is suitable for items requiring accuracy and consistent accuracy. Shell Formation for the first time in Germany during World War II was used, where he was patented by Johannes Croning, and can also be known as the "Croning process".
To create a shell pressing, silica sand is coated with a resin, which, when he is subjected to heat, solidifies into a solid. This mixture is placed in a "dump" -Krabice made of heat-resistant material and open at the top. The metal formula is then heated to approximately 450 ° F (approximately 230 ° C), coated with lubricant and secured via the box opening. The whole is reversed so that the resin sand comes into contact with the pattern. After 15 to 30 seconds, the whole is returned upright, the excess sand falls back into the box and The is removed.
Shell forming created by a process can only be 1/8 to 3/16 inches (approximately 3 to 5 mm), but still has adequate tensile strength, depending on the resin used. The mold can be heated further in the oven to cure and solidify it before removing it from the pattern. Once all pieces of the shell mold are created, they can either be clamped or held together with the adhesives. The finished form is then usually placed in a container, which is filled with a shot, sand or other similar material for adding force.
As soon as the mold is fully assembled, the molten metal is poured into it and left to cool. After cooling the metal, the shell is "broken", although the shell sections will not actually be damaged under normal conditions. The modular nature of the mold allows you to remove the finished metal piece without damaging the mold, ie the macro mold reusable.
Materials used in the process of forming a shell may be a dragMaterials used in other forming processes, but the completed form requires less material due to its thinness, which can compensate the difference in cost. Having a repeatedly usable mold is one of the key advantages of shaping the shell over the casts of sand. Although the materials needed for sandbles are much cheaper, the form is destroyed, while the shell -shaped form is repeatedly usable.