OEM Sand casting

Sand casting, the most widely used casting process, utilizes expendable sand molds to form complex metal parts that can be made of nearly any alloy. Because the sand mold must be destroyed in order to remove the part, called the casting, sand casting typically has a low production rate. The sand casting process involves the use of a furnace, metal, pattern, and sand mold. The metal is melted in the furnace and then ladled and poured into the cavity of the sand mold, which is formed by the pattern. The sand mold separates along a parting line and the solidified casting can be removed.

Sand casting is used to produce a wide variety of metal components with complex geometries. These parts can vary greatly in size and weight, ranging from a couple ounces to several tons. Some smaller sand cast parts include components as gears, pulleys, crankshafts, connecting rods, and propellers. Larger applications include housings for large equipment and heavy machine bases. Sand casting is also common in producing automobile components, such as engine blocks, engine manifolds, cylinder heads, and transmission cases. 

The six steps of the sand casting process are; placing the mold in patern in sand, setting up the gating system, removing the mold pattern, pour molten metal into mold cavity, wait for the metal to cool, the final step is to break open the mold to remove the casting.

Process of Sand Casting 

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Pattern construction

should be the first step of resin sand casting. Usually wooden patterns, resin (plastic) patterns and aluminum patterns could be used, but  Aluminum patterns is now the most widely used in spite of the most expensive cost, As it could be used to produce thousands of castings, and can guarantee much higher dimensional tolerance and better surface quality.

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The first step in the sand casting process is to create the mold for the casting. In an expendable mold process, this step must be performed for each casting. A sand mold is formed by packing sand into each half of the mold. The sand is packed around the pattern, which is a replica of the external shape of the casting. When the pattern is removed, the cavity that will form the casting remains. Any internal features of the casting that cannot be formed by the pattern are formed by separate cores which are made of sand prior to the formation of the mold. The mold-making time includes positioning the pattern, packing the sand, and removing the pattern. The mold-making time is affected by the size of the part, the number of cores, and the type of sand mold. If the mold type requires heating or baking time, the mold-making time is substantially increased. Also, lubrication is often applied to the surfaces of the mold cavity in order to facilitate removal of the casting. The use of a lubricant also improves the flow the metal and can improve the surface finish of the casting. The lubricant that is used is chosen based upon the sand and molten metal temperature.

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Once the mold has been made, it must be prepared for the molten metal to be poured. The surface of the mold cavity is first lubricated to facilitate the removal of the casting. Then, the cores are positioned and the mold halves are closed and securely clamped together. It is essential that the mold halves remain securely closed to prevent the loss of any material.

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The molten metal is maintained at a set temperature in a furnace. After the mold has been clamped, the molten metal can be ladled from its holding container in the furnace and poured into the mold. The pouring can be performed manually or by an automated machine. Enough molten metal must be poured to fill the entire cavity and all channels in the mold. The filling time is very short in order to prevent early solidification of any one part of the metal.

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The molten metal that is poured into the mold will begin to cool and solidify once it enters the cavity. When the entire cavity is filled and the molten metal solidifies, the final shape of the casting is formed. The mold can not be opened until the cooling time has elapsed. The desired cooling time can be estimated based upon the wall thickness of the casting and the temperature of the metal. Most of the possible defects that can occur are a result of the solidification process. If some of the molten metal cools too quickly, the part may exhibit shrinkage, cracks, or incomplete sections. Preventative measures can be taken in designing both the part and the mold and will be explored in later sections.
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After the predetermined solidification time has passed, the sand mold can simply be broken, and the casting removed. This step, sometimes called shakeout, is typically performed by a vibrating machine that shakes the sand and casting out of the flask. Once removed, the casting will likely have some sand and oxide layers adhered to the surface. Shot blasting is sometimes used to remove any remaining sand, especially from internal surfaces, and reduce the surface roughness.
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During cooling, the material from the channels in the mold solidifies attached to the part. This excess material must be trimmed from the casting either manually via cutting or sawing, or using a trimming press. The time required to trim the excess material can be estimated from the size of the casting's envelope. A larger casting will require a longer trimming time. The scrap material that results from this trimming is either discarded or reused in the sand casting process. However, the scrap material may need to be reconditioned to the proper chemical composition before it can be combined with non-recycled metal and reused.

FAQ of sand casting

What is molding sand?

Molding sand is a material used for molding in casting. molding sand is generally made of foundry sand, sand binder and auxiliary additives and other molding materials mixed in a certain ratio, or natural silica sand containing clay. The casting scrap caused by poor quality of molding sand is about 30 to 50% of the total casting scrap. Usually the molding sand requirements are: ① has a high strength and thermal stability, to withstand a variety of external forces and high temperature. ② good fluidity, that is, the molding sand in the external force or its own gravity under the action of the ability to move between the sand particles. ③ A certain plasticity, that is, the ability of molding sand to deform under the action of external force, and to maintain the given shape when the external force is removed. ④Better permeability, i.e. the ability of molding sand pores to transmit gas. ⑤ high collapse, also known as sand, that is, after the casting solidification molding sand is easy to destroy, whether it is easy to remove the performance from the casting. molding sand according to the different binders used, can be divided into clay sand, water glass sand, cement sand, resin sand, etc.. The clay sand, water glass sand and resin sand are the most used.

Advantages and Disadvantages of Sand Casting

The sand casting process has many advantages, especially in investment casting, another popular casting method (for more information, please read our article all about investment casting). This section will briefly explore why sand casting is so widely distributed in industry, and its shortcomings as a manufacturing method.

The main advantages of using sand casting are as follows.

Sand casting can be used to make almost any size part from a trigger to an engine block - if the correct mold is made, there is no limit to the size of the part required

Very complex parts can be made with sand casting if the correct core/pouring system is used

The process is highly adaptable and can be implemented in mass production of parts

Almost all types of alloys can be cast, provided they can be melted and poured

Low equipment costs, as it usually involves only sand and reusable patterns

short lead times for making molds, making sand casting ideal for short-term production

Low setup costs for sand casting and cost effective modifications

The main disadvantages of using sand casting are as follows.

Sand casting creates a high degree of porosity in the metal, resulting in low strength of the final part

Poor surface finish of the outgoing mold, which must be cleaned

Low dimensional accuracy of the casting due to poor surface finish and shrinkage of the metal after cooling

Sand casting is not defect-proof, so cleaning is mandatory and can be time-consuming

Sand castings with low tolerances must undergo some secondary processing

Therefore, although sand casting may be a cheaper alternative to investment casting and can provide more complex shapes, more work is required to obtain the same accuracy, finish and overall part quality.

Applications of sand casting

It is difficult to keep track of how many different techniques use sand casting. Its versatility as a casting process makes it ideal for almost any complex part, and almost all modern technologies benefit from this manufacturing process. The following list of only a few products manufactured using the sand casting process shows how wide the range of possible applications can be.

Sand casting is used to manufacture the following products.

A wide range of pistons and valves Sand casting

Blowers/impellers Sand casting

Cams, bushings and bearings Sand casting

Electronic equipment Sand casting

Gas/oil tanks Sand casting

Most hardware Sand casting

Engine blocks Sand casting

Automotive parts Sand casting

Screws, nuts and gears Sand casting 

Agricultural machinery Sand casting

Medical equipment Sand casting

Mining equipment Sand casting

and much more.

Sand casting, while nowhere near as precise as investment casting, is a low-cost, low-complexity manufacturing process that has repeatedly proven itself to be an integral part of modern manufacturing. If investment casting is too cumbersome, or if large parts are required, consider implementing sand casting into your production line.

About Zen Young Foundry

For many years, Zen Young Foundry has been providing customized metal casting services for various industries and project types.

Six industries where we can provide customized services:

OEM Pump & Valve Parts

Compressor Parts

Train & Railway Parts

Cylinder & Gear Box

Mining Engineering Machinery Casting Parts

Auto & Aerospace Parts

If you are looking for a solution that fits your custom metal Sand casting project, Zen Young can help you produce perfect metal parts through a reliable casting process.

We always welcome special material and difficult parts and would like to help our comstomers utmost.

 the types of casting processes:

Investment casting

Investment casting is one of the traditional casting methods. That is, the metal is heated to the temperature of the molten liquid, and then the material is poured into a mold designed with a suitable negative space and gated to effectively completely fill the molten metal. Once the metal has cooled and solidified, the metal part can be removed from the mold for finishing. Investment casting, also known as lost wax casting, is usually used to make jewelry and metal parts with complex shapes. 

Sand casting

The material used to make molds for sand casting is sand, not ceramics. Due to the roughness of sand, sand casting is most commonly used for large castings, which usually require less detail precision and tolerances.

Die casting 

Die casting is a kind of metal casting process, which is characterized by forcing molten metal under high pressure into the forming cavity. The cavity is made using two hardened tool steel molds, which have been processed into a certain shape, and die casting works similarly to injection molds.

We will choose different casting methods for processing according to the product shape, material and your working conditions. Many years of processing experience can guarantee the quality of the casting parts.

We work with our customers to design patterns and molding methods for each custom casting. Original castings or ready-to-use castings can be provided. Secondary finishing operations, including powder coating, are additional options. Contact us with any questions about the casting process and also for more information on how our casting services can meet your project requirements.