Lost wax casting and sand casting are two metal casting methods used often in metal part manufacturing industry, but they have some differences in terms of production process, production cost, dimensional tolerance, surface finish and part size etc. Also, they have their own advantages and disadvantages. 

What is the lost wax casting method? And the principle difference between lost wax casting and sand casting

1. What is Lost Wax Casting & Sand Casting:

Lost wax casting process is also called silica sol investment casting, it is a casting model made of hot melted wax, coated with multi-layer special ceramics or water glass paint to make a shell, and then burnt the wax model at high temperature, and then cast it with molten metal. casting method. Sand casting uses wet clay sand as the main molding material, which is cheap, paints the casting model, forms a cavity in the sand mold, and then pours liquid metal to form a casting.

Lost Wax Casting Wax Model

Sand Casting Mold

2.  What is the Difference Between The Lost Wax Casting Process and Sand Casting Process?

Lost wax casting process needs to design the wax pattern for lost wax casting first, and then apply multiple layers of special refractory coatings on the surface of the wax pattern to form a dense, high-strength shell mold, and then heat and dry it. Afterwards, the shell mold is placed in an oven to heat, so that the inside of the wax model expands with heat and contracts with cold. After the wax pattern is burned, molten metal is poured into the shell at high temperature to obtain the required casting. In contrast, sand casting requires placing the casting model on a special sand mold, then coating the surface of the casting model, then forming a cavity in the casting model and the sand mold, and finally injecting liquid metal into the cavity, and waiting for the metal to cool. Then remove the required casting.

3. Casting Surface Quality, and Surface Defects

Lost wax casting can produce high-precision, high-quality castings with high dimensional accuracy, good surface finish, and stable internal quality. While sand casting is more suitable for the production of large and complex castings, the cost is relatively low, the process is simple, and the size and shape of the castings are more flexible. However, compared with lost wax casting, sand casting has a rough surface, low precision, and relatively unstable internal quality.

Lost wax casting parts(above)

Sand Casting Parts(Bottom)

4. Casting Complexity, Unit Weight and Wall Thickness Differences

Sand casting process can produce very heavy and very large steel castings, but it can not be used to produce too small, too complex or very thin wall thickness castings.

The following table could be reference to tell their difference.

5. Big Difference in Casting Prices

The mould material costs of them cause very big difference on their casting prices. The wet clay sand is very cheap, and silica sol zircon sand is very expensive. For example, the sand casting is 1.45 USD/kg, and the silica sol investment casting will be 6.79 USD/kg.

In short, lost wax casting and sand casting have their own advantages, and which casting method to choose depends on the specific situation. Though lost wax casting advantages and disadvantages exist, it's still the most commonly used method to produce metal parts due to its high precision, it can reduce post machining cost and polishing cost, as it can make near to net shape of the metal part which adhere to the tolerance standard, only some of parts which need more tight tolerance need further machining. 

LE-TA Green Tech is the leading lost wax casting foundry in China with rich experience in stainless steel casting, carbon steel casting and alloy steel castings, etc. with tight tolerance and we can process complex metal casting parts with thin walls, at the same time, we can offer machining services to save your time and cost as well. Contact our engineer to understand our capabilities and see how we can assist you on your custom parts.