Article Description : This article titled ‘Casting Suppliers- Global Sourcing considerations’ explains the process and its types that a professional must know before he/ she decides to involve in supplier sourcing.
Casting processes performed by Metalworking suppliers : There are several supplier networks available when you look for any kind of casting processes in metalworking. But, to find unique suppliers who carry out specific sub-process of a casting process, it requires a little conscious research about your own requirement.
For your company to know which exact casting process is required, you must be aware of all the corresponding processes and must be able to choose the right match. Firstly, let us get into knowing what a casting process is!
Casting process involves transition of a metal’s chemical properties through heating at suitable temperatures. The metal is dissolved and melted by continuous application of heat. The liquid metal is then solidified by pouring it into a mold and allowing it to cool down. This renders the desired shape to the metal according to the customer’s requirement. The output is known as Casting.
The classification of a casting process is based on the type of molds used. The first factor to consider is to find if your product or service requires an expendable mold or a permanent one. But it is important to know what is ‘expendable’. Depending on the need, Manufacturers can either use just a one-time usable mold or a permanent mold.
When a casting is produced using a mound that can be disposed after the casting process, it is known as Expendable mold casting. After a metal is casting is performed using molds, the debris of the molds can be done away with. Whereas, when a casting is produced using molds that are made of strong and non-disposable materials, the process is known as Non-expendable casting.
I. EXPENDABLE MOLD CASTING:
Factors for considering expendable mold casting:
· One-time usage
· Small-size operations
· Require less maintenance.
1. Sand casting:
The process in which a casting is produced using molds created using sand molds. These sand molds are made of sand particles bonded together using clay or oil or any other kind of binders that align with the chemical properties of the work metal.
2. Shell mold Casting:
This molding process is similar to sand casting process. The mold is made of finer sand particles than the sand particle size used in the sand-casting process. The material used in this process is molded using resins that make the surface finish compact and clean. Also, the mold is made by heating and hardening the shell formed during its creation. Due to harder surface of the product mold, the precision and finish of the metal casting is much better that sand casting.
3. Plaster mold casting:
This casting process follows the same procedures as the sand-casting process, with only a difference of using Plaster of Paris instead of sand during mold formation. But, only limited types of metals can be used for forming castings using this method. Because, the plaster used in this process can withstand only metals with low melting points.
4. Investment casting:
This oldest method of casting uses inflexible materials like beeswax to form the molds. These molds exhibit intricate precision ensuring no re-work requirement once the casting is done. Yet the material requires attention and care due to the fragility of wax surfaces.
During investment casting, a pattern is created using wax. A pattern is a replica or pre-designed models of the desired metal product shapes. The wax is repeatedly dipped in a molten pool of ceramic. The wax is now melted by heating the ceramic mold making empty space for the molten metal to fill the molding cavity. Now, the molten metal is poured into the cavity and solidified. Finally, the ceramic mold is removed by application of vibration.
5. Evaporative-pattern casting:
During this metal casting process, patterns are used for producing specific metal shapes. The patterns are made of materials that can evaporate while molten metal is poured into the mold. There are two main processes carried out during the Evaporative-pattern casting:
In this process, foam is used as a pattern material. This process is similar to investment casting while the only difference is that the pattern is made of foam instead of wax.
In this process, the pattern is made of polystyrene foam. The pattern is placed inside a mold and the surrounding surface is filled using materials like sand. The molten material is poured inside the mold. This molten metal occupies the space of the pattern by making it evaporate due to its heat emission. Thereby, the molten metal replaces the occupied by the pattern thereby acquiring the desired shape.
II. NON-EXPENDABLE MOLD CASTING
Factors for considering expendable mold casting:
· Dimensional accuracy
· Good heat conductors
1. Permanent mold casting:
Strong and re-usable molds made mostly of metals are used in this process. During this process, a metal core tool that has the output design engraved on it, is filled with a mixture of sand and resin. The metal core tool is heated to melt the resin and sand mixture. The molten mix is then allowed to cool for solidification. The solidifies mix is then removed from the tool. This solidified mix is known as Fused core.
These cores are placed in the permanent mold gravity tool. On closing the tool, the feed system is fixed to the set up. Molten metal is poured into the tool. Once the metal solidifies, the feed system is removed, and the casting is taken out of the tool. The fused core is also removed through vibration.
2. Die Casting:
The mold used in this casting contains the pre-designed pattern of the desired metal product engraved on it. This set up is known as ‘Die’. During this process, the molten metal is poured into an injection barrel and fused into the mold. The metal solidifies inside the mold and then is ejected by means of rods or pins. Thereby, Die- casting can be efficiently performed.
3. Centrifugal casting:
This process is used to cast metals in rotational and symmetric axis with fixed specifications requested by the customers. Hollow metal tubes are casted using this process.
4. Continuous casting:
This process is used when large batches of constant cross-sectional metal products are required. During this process, the molten metal is poured into a copper mold. The resultant strands of metals are passed into roller chambers where water sprays are employed to cool them down. Following this, the metals are cut into desired size.
Essentials to consider before supplier sourcing for casting processes:
When you involve in the procurement of casting, it is necessary to ensure that your supplier sourcing depends very clearly on the right process required for your product. In the procurement cycle of the Metalworking market, right supplier discovery is a key challenge. When you choose suppliers, make sure:
• The supplier serves your location
• Confirm if your metal needs a one-time or a re-usable mold
• Check for the chemical properties of the mold and ensure that it do not affect your output casting
• The best supply chain management can be achieved only through best quality. Choose the suppliers with the capabilities of producing the best in the market.
• Go ahead with expendable mold casting if you choose to go with cost-effective casting process
• Select non-expendable casting if you are looking for intricate and precise output.
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