What is V-Casting Process?
V Casting Process (also known as Vacuum mold casting process) is a casting process in which the mold cavity holds the shape of the casting due to forces exerted by the vacuum pressure. The sand mold used in the vacuum casting process does not contain moisture or any binders.
Thin walled profiles can be made with good accuracy using vacuum process.
V casting process (or vacuum mold casting process) was first developed in Japan around the year 1970.
V Casting Process (7 Steps)
The step by step procedure involved in V casting is mentioned below.
Step 1: Attaching plastic sheet to the pattern
In the V-casting process, a special type of pattern is used which contains vacuum holes.
A thin plastic sheet is attached to the pattern and then the vacuum pressure is turned on. Because of this, the sheet remains in contact with the surface of the pattern.
Special type of flask containing holes is used for the manufacturing process.
Step 2: Assembly of vacuum flask over a pattern
The flask is placed over the casting pattern and it is then filled with sand.
Step 3: Attaching pouring cup and cutting Sprue in the mold
Now, the pouring cup and sprue are cut into the mold for the pouring of molten metal.
Step 4: Attaching thin sheet on the top of the mold
Another thin sheet is also placed on the top of the mold.
The vacuum pressure is turned on which adheres the top plastic sheet to the mold.
Step 5: Separating the pattern from the mold
Now in the next step, the vacuum on the pattern is turned off and then the pattern is removed.
During this process, the vacuum pressure is still kept on.
Because of this, the plastic sheet at the top remains in contact with the mold and the other plastic sheet remains in contact with the mold at the bottom as shown in the diagram.
The thin sheet which is at the bottom is now holding the impression of the pattern due to the vacuum pressure.
Step 6: Preparing the drag portion
In the exactly similar way, the drag portion of the pattern is made.
After this, the cope and drag portion (i.e upper portion and lower portion) are assembled with each other as shown in image.
So now there are a total 4 plastic sheets used in the combined mold (two sheets are the top and bottom, and the rest two sheets hold the impression of the pattern.
Step 7: Pouring of molten metal and solidifying it
The molten metal is poured in the mould cavity from the pouring cup.
When the molten metal is poured in the mold cavity, it burns the plastic sheet.
The molten metal is allowed to solidify and finally the casting component is obtained.
Advantages of Vacuum mold casting process
Advantages of the V casting process are mentioned below.
- Special types of molding sands and binders are not needed for Vacuum mold casting process.
- The metal casting defects which are related to moisture are eliminated.
- Wastage of material (metal) is less because of the small size of riser.
- It is easy to make castings at high volume in less time.
- It is possible to cast complex shapes with uniform properties.
Disadvantages of Vacuum mold casting process
Disadvantages of the V casting process are mentioned below.
- The disadvantage of vacuum process is that the tooling cost is higher.
- Recovery of sand occurs due to lack of binders and other additives in the sand.
- The mold used in the vacuum casting process has short life. If steel or iron is used in vacuum casting process, then the mold life becomes extremely small. This is because steel and iron have higher melting temperatures.
Applications of Vacuum mold casting process
Applications of the V casting process are mentioned below.
- Vacuum mold casting process is perfect to use for prototyping works as the plastic pattern can be easily modified.
- V casting process is used for manufacturing the parts of gas turbine. Parts with wall thickness of 0.5 mm can also be manufactured using vacuum mold casting process.