Learn zero to one hundred rijeh templates
The malleability of metals in the molten state led humans to melt metal and pour it into molds to make the tools and equipment they need in everyday life. In fact, the casting process dates back to more than 4,000 years BC.
Over time, more advanced methods for casting metals emerged. These methods are divided into three main groups based on equipment and working methods: sand casting, metal casting and die-casting.
The casting method in metal molds, which is known as the rigging method, is done using the rigging mold. These molds are basically metal molds that are used to produce a large number of parts in a row. The ridge mold consists of two or more metal pieces that use metallic and non-metallic muscles.
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Mold design and casting modeling
In general, molding is one of the basic processes in the production of various parts. Nowadays, suitable molds are prepared for making all kinds of parts based on the type of manufacturing process. Some of the most important molds are casting molds, plastic injection, forging and pressing. In the continuation of this article, we will exclusively design casting molds.
To produce parts with the help of casting, a suitable mold must be made. As you know, there are different methods for casting, each suitable for making a particular type of part. Therefore, the mold prepared for each of the casting methods will have a unique material and characteristics. Casting molds can be classified into different shapes. In one of these shapes, casting molds are divided into three categories: die-cast molds, ridge molds and sand molds. Another method of dividing casting molds is to divide them into temporary molds and permanent molds. Each of these molds is suitable for a specific type of casting, each of which is described below.
Types of casting molds
We first examine the templates in terms of temporary templates and permanent templates:
Temporary templates
These molds disappear after once melting and during the removal of the piece, hence they are known as temporary molds. The most common of these molds are sand molds, which we will discuss below. It should be noted that in addition to casting sand in precision and gypsum casting, temporary molds made of ceramic and gypsum are also used.
Permanent templates
These types of molds are made of metal and restore the pressure of the melt to itself, and as a result, the percentage of shrinkage is reduced and structural defects are prevented. Because the heat transfer rate in these molds is higher than in temporary molds, finer cast structures and mechanical properties are often better and higher. The two main casting methods with this mold are high pressure casting and low pressure casting. Diecast molds are used in high pressure casting and ridge molds are used in low pressure casting. In the following, we have examined these templates.
Another division of templates mentioned in the previous section is as follows:
Dykast templates
These molds are suitable for making aluminum parts that have a uniform thickness between 1.5 and 15 mm. The best method of casting these parts is pressure casting because the quality of making the final part is high and the lack of pleating eliminates steps such as pleasing, grinding and drilling from the part production process. Therefore, this method is used to make parts in high circulation, because at the same time, the production of each piece is greatly reduced and the cost of producing each piece will be lower. As the name implies, high-pressure aluminum melt is injected into the mold. Therefore, the mold used in this method must withstand the high pressure of molten metal, so molds with high volume and thickness are made of hot-rolled steel. Diecast templates are generally large and expensive.
Precise casting mold
Rigging templates
If the final part is aluminum but the thickness of the part is not uniform, or the quality of the part is considered in terms of strength, or we want to make a part without fine-grained and porosity, we can no longer use the previous method and for this purpose the melt must be slowly pushed in. Cast steel molds, which is called low pressure casting. These templates will have smaller dimensions and volume compared to diecast templates. The complexity of these templates lies in their design and especially the design of the gate system in them. Making these molds requires more advanced technology and more precise design.
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Sand Forms
Definitely the most common method of producing metal parts that has been used for a long time has been the use of sand molds for casting. In this method, first a metal model of the piece is produced and with its help, a sand mold is produced and molten metal is poured into this mold. There are many types of sands used in this method, some of the most common of which are silica sands, light sands and zirconia sands. To make some molds, sodium silicate (glass water) is used as the mold adhesive, in which case carbon dioxide gas is used to harden the mold.
Casting sand mold
Casting mold making process
Now that we are familiar with the common types of casting molds, it is better to take a look at the process of making these molds.
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Today, the advancement of technology in the field of casting has shown its effects well, the entry of CNC machines into the field of production and the development of various engineering software in the field of design of casting molds are two important results of technological advancement in the casting industry. With the help of advanced mold design software, the most complex shapes and molds can be designed and with the help of CNC, parts can be produced in a much shorter time than before.
In general, the production process of casting molds is divided into two parts: mold design and mold making. In the design department, the design engineer uses the technical drawing of the part and with the help of powerful software such as CATIA, MECHANICAL DESKTOP, SOLLIDWORKS and AUTODESK INVENTOR, designs the components of the mold and the gate system, then builds the three-dimensional model of the mold and so on.
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Types of molds in the foundry industry
Mold is used to make parts for crushers and mining machines in the casting method. The mold plays an essential role in making all kinds of parts. In casting, first the metal is turned into melt in the furnace and then poured into the mold and after freezing, the piece is separated from the mold.
Depending on the material of the part that is made, the material of the mold must be determined. There are two types of templates: temporary and permanent.
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Types of sand in terms of how to find and access
Natural sand: including river sands and wind sands. Natural sand is extracted and used directly from natural sources and no additional work is done on it, such as river sand (these sands are tested that do not contain lime). The good thing about river sand is that it is washed and has a higher roundness. The surface quality of the parts increases. But in windy sand, there is also clay, which has adhesive properties.
Synthetic sand: In this case, natural minerals are identified and, for example, it is sifted and impurities such as lime are removed, crushed and rounded (these sands have a higher temperature tolerance).
Types of sand in terms of appearance
Round sands: In this case, the shape of the sand particles under the microscope is spherical. Most artificial sands are round sands that provide better surface quality and better gas permeability (gas permeability is related to sand porosity).
Pseudo-round sands: This type of sand is round in parts and angular in parts.
Angled sands: This sand is completely angular and is fully compacted and offers higher strength. It has higher strength in terms of mold transport, melt movement and melt pressure, but low gas permeability.
Mixed sands: These sands do not have a special shape and are a mixture of 3 other types.
Sand casting operation After the casting
Sand casting operation After the casting is done and the muscles are in place, the two halves of the cast are paired together and weighed. The design of the feed to supply the required molten metal is also important when freezing the cast. The pond also acts as a feed. After solidification, the casting is shaken and removed from the mold, and the sand of the oxide layers attached to the casting is removed by vibration or sandblasting. Cast iron parts are cleaned by spraying a steel ball or sandstone. Cast parts can be cleaned electrochemically or by acid washing or chemicals. Almost all metals on the market can be sand casted. Dimensional accuracy is not as good as other castings, but it can be used to cast complex shapes. Sand casting for low production is economical and the cost of equipment is often low. Pattern and materials used to make the pattern The first step in sand casting is pattern making. The pattern is a copy of the part to be cast, along with modifications that incorporate the requirements of the casting process. Factors such as the number of molds to be made from the mold, the size and shape of the casting, the dimensional accuracy and detail required, and the casting process determine the material of the mold. Wooden patterns are usually used for parts that are to be produced in low circulation due to their cheapness and simplicity of construction. But the wood does not have very large dimensions and may deform with moisture. Metal patterns are more expensive, but have more dimensional stability and are therefore used for high-volume parts. The use of polyurethanes, which is a type of hard plastic, has become very common today. [2]
Fluidity and pouring temperature
If the melt freezes before it completely passes through the paths and fills the part, defects such as misrun or cold shot are created. The ability of the molten substance to move smoothly and fill the fluid is called. Factors such as the thinness of the castable surface, the length of this thin section, the accuracy of the details made, and the ability to fill distant and difficult points depend on the fluidity of the melt. [3]
The role of the gateway system
Because impurities are more likely to be present on the front of the melt (because it absorbs and pushes the impurities in the path), creating a runner well or runner extension can prevent this from entering. Prevent impurities into the main cavity. Ceramic filters or nets can also be used inside the gate network to trap impurities. Wire meshes can be used for non-ferrous metals, while ceramic meshes are commonly used for steels and cast irons. [3]
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In general, several different methods are used to make metal parts. Each method depends on the type of piece
As mentioned in previous articles, casting steel parts is a process that can be used to build a variety of complex structures.
The mold is used for casting operations and the method is to first melt the metal. Then the molten metal is poured into the mold and after cooling and freezing the molten material, the metal piece is separated from the mold. May be.
As mentioned above, we need a mold to perform the casting operation, and before starting the casting process, a suitable mold must be made, according to the shape of the desired production part.
Casting is done in different ways according to the material and characteristics of the piece, and based on this, the type of mold is determined.
9 steps to make a piece by precision casting
Step 1: Build the original pattern
Initially, the mold designer creates a basic pattern of wax, clay, wood, or plastic. In recent years, the use of 3D printing technology has made it much easier to make the original pattern of precision casting.
Step 2: Make a precision casting mold
At this stage, a template is produced that fits the original pattern. Sacrificed wax is cast in these molds. There are different ways to make these templates. For example, the original mold can be made directly from the original pattern by performing the casting process. Of course, in this case, the main pattern should be metal and the melting point of the main mold should be less than the original pattern.
Step 3: Make models from wax
At this stage, wax patterns are made. Of course, in addition to wax, frozen mercury or plastic can also be used. These patterns are usually prepared in two ways:
In the first method, wax is poured into the mold. The mold is rotated continuously so that a layer of wax completely covers the inner surface of the mold. This process continues until it reaches the desired thickness.
In the second method, the mold is filled with molten wax to freeze and form.
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