Finishing
Lost-wax Casting
Lost-wax casting, also known as investment casting, is a precise and versatile manufacturing process in which molten aluminium alloys are poured into a ceramic mould to produce complex and detailed parts. In lost-wax casting, a wax model of the desired product is first made, which is then coated with multiple layers of ceramic material to form a strong mould. Once the wax is melted out, a hollow shape remains, into which the molten aluminium is poured.
The process is renowned for its ability to reproduce intricate and thin-walled structures with high precision. This enables the production of parts with minimal post-processing, saving both time and cost. Lost-wax casting is commonly used to produce components for the aerospace, medical technology, and other industries where high standards of accuracy and finish are required.
Although the production cycle of lost-wax casting is longer than that of high-pressure die casting, the process allows for the manufacturing of parts with exceptional detail and surface quality, often without the need for further machining. The ceramic mould can only be used once, but the quality of the cast parts and the ability to create complex shapes make this process especially suited for small to medium production runs of 100 to 10,000 pieces.
With lost-wax casting, both small and large quantities can be produced, with production costs depending on the complexity of the design and the required precision. Compared to high-pressure die casting, the unit prices for lost-wax casting are relatively higher. However, the startup costs for moulds are a fraction of those for high-pressure die casting.
Finishing
Advantages
The main advantages of lost-wax casting are:
- Lost-wax casting allows for the production of highly complex and detailed parts with minimal tolerances and excellent surface quality.
- The flexibility of the wax model enables virtually unlimited geometric shapes, including thin-walled structures and internal channels that are difficult to achieve with other casting methods.
- The high precision of the process ensures that many parts are immediately usable without extensive post-processing, saving time and costs.
- In addition to aluminium, various other alloys can be cast, making the process suitable for different applications and industries.
- The process is economically viable for both small and medium production runs, with quantities ranging from a few dozen to thousands of pieces.
- Lost-wax casting produces parts with very good structural integrity and surface finish, which is important for applications in aerospace, medical technology, and other precision industries.
Consequences
- Lost-wax casting is most cost-effective for medium production runs. For smaller quantities, the cost of making wax models and ceramic moulds can be relatively high. Alternative casting methods may be considered in such cases.
- Although thin-walled structures are feasible, a minimum wall thickness of 2.5 to 4.0 mm must be taken into account, depending on the product. Too thin walls can lead to deformations or casting defects.
- Aluminium tends to shrink during solidification. Therefore, designers must account for possible shrinkage and maintain the correct tolerance limits to avoid issues like shrink holes or deformation.
- While lost-wax casting is suitable for complex geometries, very intricate designs may require additional attention when producing the wax models and moulds. In some cases, multiple castings or post-assembly may be necessary to achieve the desired final product.
- Lost-wax casting is most suitable for small to medium-sized parts. For very large components, other casting methods such as sand casting may be more appropriate.
- To ensure high quality, precise process control is essential. This includes carefully managing the melting temperature, pouring temperature, and degassing procedures to minimize defects such as porosity and inclusions.
Samples
