Casting/Machining

Most first-generation investment casting manufacturers in China are joint-ventures or wholly-owned investment from Taiwan, Japan and other places. Most of them use silica sol shell making technology and are mainly distributed in coastal areas or its surrounding areas, such as Shandong, Jiangsu, Shanxi, Anhui , Guangdong and other provinces.

After 20 years development, the 2nd generation and the 3rd generation investment casting manufacturers in China have already well developed and taken most export business. High level equipment and facilities, the quality control system established, product quality can reach similar level of western companies’ but with strong competition on TCO and service. They can be considered as potential suppliers to produce their own products to replace foreign products.

Many precision casting factories use different technical routes. According to different quality requirements, prices and delivery time of castings, these factories need take correct selection of the right casting technology to meet customers’ needs. In recent years, in order to provide samples quickly, many investment casting manufacturers in china use 3D printing to make shells, which greatly speed up the prototyping process and provide fast solutions for customers to develop new products.

Shell Molding

Shell molding, also known as shell-mold casting, is a process of expendable mold casting that uses resin-covered sand to form the mold. This process has greater dimensional precision, high productivity and less labor costs advantages when comparing with sand casting. It is used for tiny to medium components that require high precision.

Shell mold casting is a sand-like metal casting method, in which molten metal is poured into an expendable mold. The mold, however, is a thin-walled shell produced by adding a sand-resin combination around a motif in shell mold casting.
Shell mold casting enables both ferrous and non-ferrous metals to be used. For instance, cast iron, coal steel, alloy steel, stainless steel, aluminum alloys and metal alloys are widely used. Typical components are small size to medium size and involve elevated precision, such as equipment housings, heads of the cylinder, linking wires and arms of the lever.

The big advantages for shell molding process is high productivity, less labor costs, good surface finishes, low tooling and equipment cost, short lead time. While it also has disadvantages, such as possible high porosity and often needs secondary machining. If performs manually, high labor costs occurs. There are fewer shell molding manufacturers in mainland China. When we visit some shell molding suppliers, we realize that these potential suppliers need keep monitoring on daily basis for quality control.

Sand casting

Sand casting, also known as sand molded casting, is the most commonly used casting process. It is suitable for all kinds of materials, most Ferro-alloys and non-ferrous alloy can be used for sand casting. The weight of castings can be from tens of grams to tens of tons. The biggest advantage of sand casting is: low production cost. The disadvantage of sand casting is that it could only produce castings with simple structure; the surface roughness is low, the metallurgy of the castings and the internal density is low. Casting mold can be produced by hand or by machine. Manual molding is suitable for single piece, small batch and complex shapes. Machine modeling can greatly improve the surface accuracy and dimensional accuracy but with large investment at the very beginning.

As China tightens environmental protection in recent years, many small and medium-sized OEM sand casting parts manufacturers have been forced to close down because they fail to meet the minimum environmental protection standards. Therefore, there are fewer sand casting factories than before. Currently, the sand casting factories are mainly in northern China. But, the Yangtze River Delta region still retains some sand casting manufacturers and aluminum sand casting manufacturers.

Low-pressure casting & gravity die casting

Casting material: non-ferrous metals
Casting quality: tens of grams to tens of kilograms
Casting surface quality: good
Casting structure: complex
Production cost: higher cost (because of upfront cost on mold)
Scope of application: small batches, prefer large and medium-sized non-ferrous alloy castings, thin-walled castings

Low-pressure casting is a casting method, in which liquid metal fills the mold and solidifies into a casting under the action of low-pressure gas. Low-pressure casting is primarily used for the production of aluminum alloy castings.

In gravity die casting, molten aluminum is poured into a metallic tool. The casting temperature is about 750℃. The tolerances and surface finish are good. The use of sand cores in gravity die casting enables casting of very complex components.
Gravity die casting method is a competitive casting method when production quantity is relatively small or when heat treatment is needed to improve the mechanical properties. This casting method gives better tolerances and surface finish than sand casting. The tooling cost of this method is somewhat higher than by sand casting.

Because process chain is short and it is not difficult to control quality, suppliers’ ability of low-pressure aluminum castings and gravity die casting are mature; not only casting process, most suppliers provide series of post finishing of polishing, machining anodizing and other processes. Furthermore, new technology development capabilities of both low-pressure casting and gravity casting are also strong. After a period of running-in, it can be considered as a qualified supplier.

Lost Foam Casting

Lost foam casting (LFC) is a casting method used to create solid metal parts from molten metal. When a part is created through casting, a mold is used to produce the desired shape. In lost-foam casting, the mold is made from polystyrene foam, which is lost during the casting process as the liquid metal melts it and replaces its shape — hence gets name “lost-foam.”

Lost foam casting is a new process with almost no margin and accurate forming. This process does not need to take a mold, has no parting surface and no sand core, so the casting has no flash, burrs and draft slope and reduces the core due to dimensional error caused by combination.

The above casting methods have different process characteristics. In casting production, different castings choose corresponding casting methods.