Sand Casting Disadvantages
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| Sand Casting Disadvantages |
What are the disadvantages of the sand casting?
- High volume small size casting is possible using machine moulding but the process is not suitable for mass production because the moulds need to be made and broken every time new casting is to be manufactured.
- It is a time-consuming process compared to the die-casting process which is used for mass production.
- Care must be taken to avoid erosion, fusion and metal penetration of molten metal into the mould cavity where solidification of the casting takes place.
- The entire sand-casting process takes up a lot of space in the foundry.
- Moisture needs to be controlled properly while mould-making to avoid casting defects in sand casting such as pinhole porosity.
- Surface finish is very dependent on the type of sand used, ramming and the size of the grain.
- Very complex casting cannot be produced as we produce in the investment casting.
- It requires higher labour costs for casting operations, pattern making, mould making, mould-breaking and the shake-out of casting from the mould. A well-trained operator is required with experience and skills.
- At times casting needs to be protected from oxygen with argon gas to avoid molten metal to oxides as metal is poured in the open.
- A secondary manufacturing process is necessary after sand casting as the casting surface is rough. This step is less for processes such as die casting and investment casting process.
- A skilled pattern maker needs to be employed for this process to obtain good final casting. The mould-making process is time-consuming and manual in small foundries.
- Casting flexibility is less as compared to special casting processes.
- Sand casting is traditionally the conventional time-consuming casting process. To reduce the time consumption and dependency on skilled labour high tooling cost needs to be invested for producing 3D printed cores and moulds using machines.
- Dimensional accuracy is low as compared to investment casting, shell casting and die casting process.
- This process is more prone to casting defects such as blowholes, open holes casting defects, internal air pockets and air inclusions due to the presence of moisture in the mould, to reduce this moisture (water) is replaced with resin to improve strength and reduce any water content.
- Sections with different thicknesses joined together require padding and chills to reduce hotspots and hot tears.
- The use of sand as a moulding material has added disadvantages as it increases the casting defects chances such as fusion, penetration of sand in the metal, honeycomb or sponginess defects, slag inclusions and drop and run-out of the weaker mould reducing the overall productivity and quality of the casting.
- The surface finish is lower than all other casting processes.
- This process is not suitable for high tolerance and to produce dimensional accurate casting.
- Difficult to produce final casting without having porosity defects because of sand mold.
- Harmful fumes are produced in the foundry due to the sand during the sand casting process.
- Sand casting has numerous applications and uses apart from the disadvantages but this process is best suitable for producing casting in large sizes for any material, that is why I have written a separate article explaining the advantages of sand casting.