What is the difference between precision casting and ordinary sand casting?

Casting, as a fundamental process in the equipment manufacturing industry, is a crucial step in injecting molten metal into molds and cooling them to form the required parts. Among numerous casting processes, precision casting and ordinary sand casting are the two most widely used types, which support the production needs of different fields with their different process characteristics, adaptation scenarios, and cost advantages. With the transformation of manufacturing towards diversification and high-end, how enterprises can accurately distinguish and choose suitable casting processes based on product positioning, quality requirements, and production costs has become the key to improving production efficiency, reducing costs, and enhancing product competitiveness. Industry experts point out that there are significant differences between precision casting and ordinary sand casting in terms of process flow, forming accuracy, and application scenarios. Clarifying these differences is necessary to achieve precise matching between process and product requirements.

According to research data from the China Foundry Association, the application of ordinary sand casting in China currently accounts for over 70%, widely serving fields such as general machinery and construction hardware; Precision casting applications account for about 20%, mainly concentrated in high-end fields such as aerospace, military, and medical equipment. The core difference between the two processes is first reflected in the process flow and mold preparation, which are also the basis for determining the forming accuracy and production efficiency of the two.

As the most traditional and fundamental casting process, ordinary sand casting has a relatively simple process, which includes the core steps of mold making, sand molding, pouring, cooling, and sand cleaning. The mold is often made of wood, resin, or metal, and then filled with molding materials such as quartz sand and clay around the mold. After compacting, the mold is taken out to form a sand mold cavity. The sand molds for ordinary sand casting can be manually or mechanically molded. Manual molding is suitable for small-scale and irregular parts production, while mechanical molding is suitable for large-scale production, with the characteristics of easy operation, low mold cost, and short production cycle. However, sand molds have low strength, good breathability, and high surface roughness after molding, making it difficult to achieve high-precision molding.

Precision casting is more complex and refined in its process flow, including investment casting, shell preparation, roasting, pouring, cooling, cleaning, and other steps. Among them, investment casting and shell preparation are the core steps that differ from ordinary sand casting. Taking the most widely used investment casting as an example, firstly, it is necessary to use materials such as paraffin, resin, etc. to make an investment mold that is completely consistent with the shape of the casting. Then, refractory materials are coated multiple times on the surface of the investment mold, and after drying and hardening, a high-strength shell is formed. Then, the investment mold is heated, melted, and discharged, and the shell becomes the final casting mold. The shell of precision casting is made of high-temperature resistant and high-strength refractory materials, with much higher forming accuracy than ordinary sand molds. The surface of the shell is smooth and can accurately replicate the details of the investment mold, enabling the formation of complex structures and thin-walled parts.

Forming accuracy and surface quality are the most obvious differences between precision casting and ordinary sand casting, and they are also the core basis for adapting to different product requirements. Due to the coarse sand particles and limited mold accuracy, ordinary sand casting has relatively low casting accuracy, large dimensional errors, and high surface roughness. It usually requires subsequent machining and polishing to meet the product size and surface requirements. Generally speaking, the dimensional tolerance grade of ordinary sand casting castings is mostly between CT12-CT14, and the surface roughness Ra value is mostly between 12.5-50 μ m, which is suitable for the production of general parts with low precision requirements.

Precision casting, with its fine process flow and high-quality shell, has significantly better forming accuracy and surface quality than ordinary sand casting. The dimensional tolerance level of its castings can reach between CT4-CT8, and the surface roughness Ra value can be controlled between 1.6-6.3 μ m. Most precision castings do not require subsequent machining or only require a small amount of precision machining to meet the accuracy requirements of high-end products. For example, engine blades in the aerospace field and artificial joints in the medical device field require precision casting to achieve complex structures and high-precision molding, which is difficult to achieve with ordinary sand casting.

The differences between the two processes are equally significant in terms of applicable scenarios and product types, and precise selection should be made based on product requirements. Ordinary sand casting has the advantages of low cost, short production cycle, and wide adaptability, suitable for the production of large quantities, low precision, and large shaped parts, such as mechanical bases, machine tool shells, building hardware, agricultural machinery accessories, etc. This type of product does not require high precision and focuses on production cost and efficiency. Ordinary sand casting can effectively balance these two aspects and is currently the most widely used casting process in industrial production.

Precision casting is more suitable for the production of products with small batches, high precision, complex structures, and high added value. It is mainly used in high-end fields such as aerospace, military, medical equipment, and high-end equipment. For example, precision components in the aerospace industry need to work in high temperature and high pressure environments, with extremely high requirements for dimensional accuracy and mechanical properties, and can only be achieved through precision casting; Artificial joints and surgical instruments in the field of medical devices require good surface smoothness and biocompatibility, and precision casting can effectively ensure product quality; Complex structural components in the high-end equipment field, such as gears and turbines, can be integrated through precision casting, reducing subsequent assembly processes and improving product reliability.

Production cost and production efficiency are also important considerations for enterprises when choosing casting processes, and there are significant differences between the two in this dimension. The mold cost of ordinary sand casting is low, the process flow is simple, the production efficiency is high, and it is suitable for large-scale production. The production cost per unit product is relatively low. For example, mass production of ordinary mechanical bases using ordinary sand casting can effectively reduce mold investment and production cycle, and improve production efficiency.

The process of precision casting is complex and cumbersome, with high preparation costs for molds and shells, long production cycles, and much higher production costs per unit product than ordinary sand casting. For example, in the production of precision aerospace components, only investment casting and shell preparation require a lot of time and materials, resulting in a significant increase in product costs. However, precision casting can reduce subsequent machining processes, enhance product added value, and is suitable for high-end product production. Its higher cost can be compensated for by the high added value of the product.

In addition, there are certain differences in material compatibility and environmental requirements between the two processes. Ordinary sand casting has a wide range of adaptability to metal materials, including low-alloy steel, cast iron, cast copper, cast aluminum, and other materials. Sand casting materials can also be recycled and reused, making them environmentally friendly; Precision casting requires higher purity and performance of metal materials, and often uses high-performance materials such as stainless steel, high-temperature alloys, and titanium alloys. In addition, the recycling of shell materials is difficult, and the requirements for environmental protection treatment are higher.

Industry experts remind that when choosing casting processes, companies do not need to blindly pursue high precision, but should consider their own product positioning, quality requirements, production batch size, and cost budget comprehensively. If the product is a large-scale, low precision, and universal part, ordinary sand casting should be preferred to balance cost and efficiency; If the product is a high-end part with small batch, high precision, and complex structure, precision casting can be chosen to ensure product quality and added value. At the same time, with the continuous upgrading of casting technology, ordinary sand casting is gradually improving its forming accuracy by optimizing the process; Precision casting continuously reduces production costs and shortens production cycles through technological innovation, and the two processes show a trend of mutual optimization and coordinated development.

In practice, many enterprises have achieved a dual improvement in production efficiency and product quality by accurately distinguishing the differences between two processes. For example, a certain general machinery enterprise produces large machine tool bases using ordinary sand casting technology, effectively controlling production costs and improving production efficiency; A certain aerospace enterprise produces engine blades using precision casting technology, ensuring high precision and reliability of the products and meeting the needs of high-end applications.

With the transformation of manufacturing towards high-end and precision, the application scenarios of precision casting and ordinary sand casting will become clearer, and they will respectively support the production needs of high-end and general fields. In the future, with the application of technologies such as 3D printing and intelligent control, the performance of both processes will be further optimized. Ordinary sand casting will achieve improved accuracy, while precision casting will achieve cost reduction, providing stronger support for the high-quality development of the manufacturing industry.