Investment Casting and Centrifugal Casting
In modern manufacturing, the casting process is the key link to transform liquid metal into solid parts with specific shapes and properties. As two important special casting methods, investment casting and centrifugal casting each play an irreplaceable role in different fields with their unique process principles, scope of application and casting characteristics. A deep understanding of the difference between the two processes is crucial to optimizing product design, improving production efficiency, reducing costs and ensuring product quality.
Comparison Of Mold Types
1 The Mold World Of Investment Casting
In investment casting, the selection and production of molds directly affect the quality and production efficiency of wax molds. There are usually two types of molds for making wax molds: For small batch production or castings with extremely complex shapes, hand-carved wax molds are often used. At this time, no expensive molds are required, and skilled craftsmen only need to create with superb skills, but this method is inefficient and requires extremely high skills of workers. In mass production, metal molds such as aluminum molds or steel molds are used. These metal molds have high precision and good wear resistance, which can ensure the dimensional accuracy and surface quality of wax molds. However, the development cost of metal molds is high. The production cost of a set of molds may range from tens of thousands to hundreds of thousands of yuan, and professional processing equipment and technicians are required for manufacturing. In addition, the life of the mold is also an important factor. The service life of aluminum alloy molds is generally around 500-1000 pieces, while steel molds can reach tens of thousands of pieces, but they still need to be maintained and repaired after long-term use to ensure their accuracy and performance.
2 The Secret Of Centrifugal Casting Molds
The molds of centrifugal casting need to have sufficient strength and rigidity to withstand the huge centrifugal force generated during high-speed rotation. Common mold materials include cast iron, steel or heat-resistant alloys. For the production of standard rotating body castings such as pipes and cylinders, metal molds are mostly used. This mold has good thermal conductivity and can quickly cool and solidify the molten metal, thereby improving production efficiency and the surface quality of the casting. However, the manufacturing process of metal molds is complex and costly. In addition, during the casting process, due to repeated scouring of high-temperature molten metal and the action of centrifugal force, the mold is severely worn and needs to be maintained and replaced regularly. In some special cases, such as the production of large or complex-shaped castings, sand molds are also used in conjunction with centrifugal processes. Sand molds have the advantages of low cost and flexible production, but due to their relatively poor strength and thermal conductivity, they may affect the dimensional accuracy and surface quality of castings, and the production efficiency is relatively low.
Comparison Of Cost And Efficiency
1 Investment Casting: Cost Considerations Behind High Precision
1.1 Mold Cost
The mold cost of investment casting shows great differences under different production scales. In single-piece or small-batch production, the mold cost is relatively low due to the use of hand-carved wax molds or simple mold making methods, but this method has extremely low production efficiency and is difficult to meet the needs of large-scale production. In large-scale production, in order to ensure the accuracy and production efficiency of the wax mold, metal molds are required. The development cost of metal molds is high, and a set of complex metal molds may require an investment of tens of thousands to hundreds of thousands of yuan, which puts a lot of financial pressure on the company in the early stage. However, as the production batch increases, the mold cost can be spread over more products, and the mold cost per unit product gradually decreases.
1.2 Production Cycle
The production cycle of investment casting is relatively long. The entire process includes wax model making, shell preparation, dewaxing, roasting, pouring, sand cleaning and post-processing. Among them, the shell preparation process is relatively cumbersome, requiring multiple coatings of refractory materials and long drying. The drying time for each layer is usually between 12-24 hours, and the entire shell production cycle may be as long as 5-7 days. In addition, the dewaxing and roasting processes also require strict control of temperature and time to ensure the quality of the shell and the accuracy of the casting. The long production cycle not only increases production costs, but also affects the company’s capital turnover speed and market responsiveness.
1.3 Material Utilization And Labor Costs
Investment casting performs well in terms of material utilization. Since there is no loss of sand molds in sand casting, and the molten metal can fully fill the shell during the filling process, the metal recovery rate can usually reach 85%-95%. However, labor costs account for a high proportion of investment casting, because the process requires high skills of workers in key processes such as wax mold assembly and shell coating, and requires skilled technical workers to operate. The training and salary costs of these workers are relatively high, making labor costs account for 30% – 40% of the total cost.
1.4 Comprehensive Cost
For small or complex parts, the unit cost of investment casting is relatively high. This is due to the combined influence of factors such as its process complexity, mold cost and labor cost, which makes the cost of investment casting 2 – 3 times that of sand casting. However, in the case of mass production and extremely high requirements for product precision and quality, the cost of investment casting can be effectively controlled by optimizing the process, improving production efficiency and reducing scrap rate, and because it can reduce subsequent processing steps, the total cost of the product is reduced overall.
2 Centrifugal Casting: Cost Advantage Of Efficient Production
2.1 Mold Cost
The one-time investment cost of metal molds for centrifugal casting is relatively high, especially for large molds, whose manufacturing process is complex and requires the use of high-quality materials and advanced processing equipment, so the mold cost is relatively high. However, since centrifugal casting is mainly used for mass production of standardized rotating body castings, the mold cost allocation per unit product decreases rapidly with the increase in production batches. Compared with investment casting, the mold cost advantage of centrifugal casting gradually emerges in the case of large-scale production.
2.2 Production Cycle
The production cycle of centrifugal casting is short, which is one of its significant advantages. During the centrifugal casting process, the rotation of the mold allows the molten metal to quickly fill the mold and solidify, and the whole process usually only takes a few minutes to a few hours. For example, when producing small pipe castings, the production efficiency of centrifugal casting can reach dozens of pieces per hour or even more, greatly improving the production capacity and market supply capacity of the enterprise. The shorter production cycle not only reduces production costs, but also enables enterprises to respond to market demand more quickly and improve the competitiveness of enterprises.
2.3 Material Utilization And Labor Cost
Centrifugal casting also performs well in material utilization. Since it does not require a complex pouring system and riser system, it reduces the consumption of molten metal in these parts and has a high process yield. At the same time, the degree of automation of centrifugal casting is relatively high. In the production process, except for the pouring link, which requires manual operation, other links such as the rotation of the mold and the demoulding of the casting can be completed by automated equipment. This makes the proportion of labor costs in the total cost low, usually only 10% – 20%, effectively reducing the company’s labor cost expenditure.
2.4 Comprehensive Cost
For standardized rotating body castings, the unit cost of centrifugal casting is low. This is because it has advantages in mold cost sharing, production cycle, material utilization and labor costs, which enables centrifugal casting to achieve efficient and low-cost production when mass-producing these products. For example, when producing products such as cast iron pipes, the cost of centrifugal casting is only 60% – 70% of sand casting. However, for castings with asymmetric or complex shapes, the cost of centrifugal casting will increase significantly due to the need for special tooling and process design, and may even exceed other casting processes.
3 How To Choose A Process?
3.1 Investment Casting Is Preferred:
Requirements: complex shapes, high precision, difficult-to-process materials (such as aviation blades, medical implants);
Limitations: cost-sensitive large-volume parts need to be treated with caution (unless costs are reduced through technologies such as 3D printing wax models).
3.2 Centrifugal Casting Is Preferred:
Requirements: rotationally symmetrical structure, high mechanical properties, large-scale production (such as pipes, cylinder liners);
Limitations: not suitable for asymmetric or complex inner cavity parts, and the initial investment in molds is high.
