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  • How Does Metal Casting Work?
    Nov 04, 2022

    The metal casting process can create anything from tiny fasteners to large industrial components, all through a five-step procedure. It happens by creating a pattern and making a mold, melting and transferring the metal and finishing, cleaning, polish and inspecting the casting. While metal casting is a straightforward practice, it requires specialized skills and techniques to perfect.

    At Hengchang Foundry, we have the mastery and technology to form objects of various sizes for different industries like heavy equipment and transportation. No matter the complexity of the parts you require, our professional team can produce tailored castings to deliver unique parts for your application.

    What is the metal casting process? Continue reading to learn what to know about metal casting and how our metal casting services work.


    When talking about a pattern, we aren’t referencing one you trace on a piece of paper. Instead, metal casting foundries refer to patterns as a replica of the object they’re casting. This pattern helps form the mold cavity, which can be made of wood, plastic, aluminum and many other suitable materials. Making a pattern is a crucial first step because the accuracy of the mold determines the accuracy of the final product.

    The four steps in producing a precise pattern include:

    1. Shaping the mold cavity
    2. Adapting the properties of the metal cast
    3. Referencing accurate dimensions
    4. Creating a way for the liquid metal to enter the mold

    Depending on the type of material being poured into each mold, the final, solid product will distort to a certain degree. For example, it may shrink compared to the original size of the mold. This is why each pattern has allowances for slight alterations. Additionally, patterns require a draft, or a vertical tapered wall, where professionals can extract the pattern without tampering with the molded product.

    municipal ductile iron cover


    It’s now time to create the mold, which is a hollow shape that will form the metal later on in the process. While some molds are expendable, others are nonexpendable.

    An expendable mold means you can’t use it again. In that case, materials like sand, plaster foam or plastic make up the mold, and they’re destroyed during the casting process. Alternatively, you can use nonexpendable molds indefinitely, as they’re often made of aluminium.

    Both expendable and nonexpendable molds can support different pattern complexities and materials.


    While we use a multitude of materials for metal casting, they all fall under one of two categories — ferrous and non-ferrous metals. The metals used in metal casting can include iron, zinc, aluminum, tin, copper, lead alloys and others. While a ferrous metal contains malleable iron or steel, a non-ferrous metal contains nonmalleable metal, such as copper, nickel or aluminum.

    After selecting the appropriate metal type, we load it into the furnace where temperatures rise until it reaches the material’s melting point. At Warner Brothers Foundry Company, we use gas furnaces during the metal casting process, though there are two other common types of furnaces for metal casting — electric arc and induction.

    Using electric furnaces is our preferred method for metal casting because it burns cleanly and efficiently. Electric furnaces also allow us to heat the metal to the necessary temperatures without using high amounts of electricity. Electric furnaces are more efficient for our process, which keeps costs lower on our end and allows us to offer lower prices on your end.

    Once the material melts down, it’s transferred to a large ladle before it reaches the mold. Through gates and risers, or openings in the mold, workers or machines pour the liquid material into the mold. Once it takes shape, solidifies and cools, we eject the casting from the mold, removing excess metal from the gate and rider system before moving to the next step in the process.

    Understanding how long metal casting takes depends on the material — some may cool within minutes, and others take several days.


    This stage involves making the final touches and cleaning each individual part. At Hengchang Foundry Company, we go in and remove excess metal parts and begin the cleaning process, using different tools to clear away particles and dirt. The final product is the same proportion and shape as the original pattern used during step one.

    Additionally, some products may require a heat treatment, such as rail clamp, hydraulic cylinder, buffer. This process alters the properties of the material through a heating and cooling technique where the metal becomes more resilient. These treatments are ideal for applications that may endure extreme weight, wet environments or freezing temperatures.


    The metal casting process ends with an inspection to ensure everything is complete and up to our standards. During the final stage, we check the part’s physical structure and integrity to ensure it’ll hold up and perform the expected job.

    There are destructive and nondestructive testing methods, which are put in place depending on the casting’s specifications. In particular, visual inspections include looking for cracks, accuracy and surface finishes, and more in-depth testing checks tensile strength, hardness and ductility, among other components.

    No matter the industry, we inspect everything from trailer hitches and industrial equipment to small automotive parts. In the end, you’ll have a durable component that’s suited to your unique needs and operations.

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  • Metal casting foundry
    Oct 28, 2022

    The global metal casting market will be worth $12.38 billion in 2023. It is expected to grow at a CAGR of 5.3% from 2022 to 2032. With the booming castings industry, the market is witnessing an increasing demand for metal casting companies. The global casting market is currently characterized by the presence of diverse international and regional manufacturers. Metal casting companies continuously invest in developing new technologies and products to remain cost-effective and competitive. It is a good signal for the foundry like us, who export tailored valve, ring, ditch cover, agitator, etc for our customers

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  • The Change For The Tensile Strength Of Gray Ductile Iron
    May 03, 2023

    In the industry, it is customary to decide whether the gray ductile iron is qualified not depends on whether its tensile strength is qualified. While the tensile strength of the gray ductile Iron is determined by the carbon content. In addition to ensuring the basic chemical composition is qualified. With the increase of carbon content, the tensile strength will decrease. From the basic characteristics of gray nodular iron castings, it can be seen that if a small amount of carbon is added to the raw materials, the tensile strength can be improved. Therefore, in the carbon content of gray iron castings, try to make the carbon content reach 2.6% - 3.6%, and the silicon content is 1.2% - 33.0%. It is necessary to add some manganese properly when the wall thickness of gray iron castings is determined. At the same time, alloying method can also be used to improve the tensile strength of gray nodular iron castings, or adding a proper amount of microalloys, such as chromium, molybdenum, tin and other elements. It is also one of the ways to improve the tensile strength of gray iron castings. But the corresponding molten iron inoculation should be done well. It should be noted that carbon and silicon affect the strength of gray nodular iron castings in different ways. With high carbon content, it will increases the graphite content, promotes the coarsening of graphite flakes, relatively reduces the austenite dendrite content, and reduces the tensile strength. Therefore, when the carbon equivalent is constant, increasing the silicon content, the carbon equivalent is relatively reduced, the graphite content is correspondingly reduced. And the primary austenite content is increased. The Silicon with ferrite can strengthen and improve the strength. However, silicon can increase the eutectoid transition temperature and coarsen the pearlite. In a word, if the carbon equivalent is low, increasing the ratio of silicon to carbon, or reducing the ratio of silicon to carbon properly. The tensile strength of gray nodular iron castings will be improved. But if the ratio of silicon to carbon is too low, it is easy to produce white spots. In this case, inoculation treatment is needed.

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  • What is the difference between ductile iron and cast iron?
    Oct 12, 2022

    Ductile iron is an alloy of cast iron or grey iron in which the carbon forms into nodules as opposed to plates as it is in grey iron. This makes the metal more ductile than cast iron hence the name.

    Ductile iron has greater strength and ductility than gray iron. Those properties allow it to be used effectively in a wide variety of industrial applications, including pipe, automotive components, wheels, gear boxes, pump housings, machine frames for the wind-power industry, and many more.

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  • Preliminary Raw Casting Inspect
    Oct 21, 2022

    After produce the items, the preliminary casting inspection will use the visual. This inspection way involves using the human eye to detect surface defects, tears, misruns, cracks, cold shuts, gas evolution, molding flaws, metal penetration, slag adhesions and sand inclusions. This inspection is essential to ensure the casting adheres to visual acceptance standards. Inspection results should be documented and recorded, and every surface irregularity should be classified. Any castings with visually detected defects should be picked out and not moved to next steps or delivered to customers. The inspection way always use in the casting parts with different material, such as QT450-12, QT500-7,QT600-3 etc

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  • Sand Casting Process
    Oct 28, 2022

    The Sand Casting Process

    Even a child playing at the beach or in a sandbox can immediately grasp how sand casting works. When you see a child mixing water into sand to make it easier to shape it into a sand castle, that child is demonstrating how combining some sand and water works so beautifully for creating a shape. 

    At its simplest, the sand casting process for a casting foundry  is nothing more than making a cavity in the sand in the desired shape, pouring molten metal into the cavity and letting it cool. Humankind has been doing this for thousands of years. Sand is heat resistant and readily available almost anywhere on earth. 

    If you’ve ever noticed the way footprints made in wet sand hold their shape, you can easily imagine what likely inspired the first ancient metal workers to use wet sand to shape their cast metals. Everything after that has just refined and perfected the basic process.

    What Is Green Sand Casting?

    The term green sand has nothing to do with the color of the sand casting material. It means there’s some moisture in the sand; when the sand is said to be green, it means the mold has not been baked or dried. This kind of molding sand is a very economical and versatile material. When desired, the foundry can add select additives can make the green sand more ideal for a specific purpose. Green sand is used in the most common sand casting processes.

    How Do You Make Sand Casting Molds?

    Sand casting equipment within a foundry can be very basic or quite advanced, depending on the items being made. Typically, the sand is placed in a mold box, which is known as a flask. The pattern, or model, is placed in the prepared sand inside the flask to make a mold. The pattern is removed, leaving behind a perfect shape in the sand. The mold is filled with molten metal, which is allowed to cool. When the metal is sufficiently cooled, the sand mold can be broken away.

    More complicated items can be cast by combining an upper and a lower section. The upper mold is known as the cope, while the bottom half is known as the drag. Once the cope and drag are ready, they can be fastened together so that molten metal can be poured into the resulting cavity. Even further detailing is possible with the addition of a core. A core is something placed inside the mold to form a negative space that no molten metal will fill. An example would be the middle of an engine block or any other cast item that requires a hollow space.

    Castings made with cope and drag must provide a way to introduce the molten metal into the mold. It can be a simple vertical passage, known as a sprue. The sprue and its channel will fill with molten metal that will solidify and will need to be machined off to get the item to its final design.

    How Does The Sand Casting Process Work?

    In the modern foundry or casting industry, the knowledge of how each alloy will react with each potential form of mold and each potential additive allows the worker to make choices to give the finished item the desired characteristics. Metal casting is both an art and a science.

    As the molten metal cools and solidifies, it will give off gasses. The molds are designed to take that into consideration and when necessary, will be constructed to allow the gasses to escape throughout the sand casting process.

    What Is Sand Casting Used For?

    Chances are good that you’re less than 10 feet from at least one cast item right now that has been through the sand casting process. There’s hardly an industry that doesn’t have some kind of need for cast materials. Some cast items are large and can weigh hundreds of pounds, while other cast items are tiny and intricate.

    What Are Some Common Metals Used in Sand Casting?

    Almost any kind of metal can be shaped using the right sand casting equipment. Grey iron and ductile iron very well.

    What Additives Are Common In Sand Casting?

    Modern manufacturers will usually add some water and other additives to the sand casting process to make it work better for various purposes. Different alloys and different items call for additives, including these common materials:

      • Clay: It could be bentonite clay (most likely calcium bentonite) or another kind of clay. For special delicate and high-detail items, such as jewelry, Delft clay, which is imported from the Netherlands, can be used.
      • Coal Dust: Also known as Sea Coal, this is added to produce a more even surface, to make it easier to get the cast item out of the mold. It also produces casts with fewer defects.
      • Corn Flour: Believe it or not, a little bit of corn flour added to the wet sand gives the sand greater strength and plasticity.
      • Dextrin: Dextrin, derived from corn starch, is used as a binder. It improves the dry surface strength of the sand.
      • Pitch: Made from soft coal, a little pitch added to the sand improves the surface finish.
      • Wood Flour: This material is combustible, which like other combustible additives helps create a space for the grains of sand to expand without changing the shape of the mold.
      • Silica Flour: This material is just finely ground sand that’s mixed into casting materials for a more durable mold. 

    What’s The Future In Sand Casting?

    Relatively new technology in today’s casting foundry is 3D printed patterns and molds.
    The latest 3D printing equipment is capable of manufacturing a sand mold and core in just a few hours. This can save considerable time and money in some cases. 

    Once the pattern is produced, sand casting proceeds as usual, but the ability to use a 3D printer to produce the pattern, molds and cores greatly speed up the process, potentially saving production costs and increasing the accuracy of the casting. If an example of the item to be sand cast already exists, it can easily be scanned to create the 3D model.

    Once the program for producing the sand mold and core is perfected, it can be reproduced as many times as desired. Such sand casting equipment is a growing part of the metal casting industry. The sand casting advances of today would no doubt amaze the master sand casters from a hundred years ago — not to mention those of a thousand years ago!

    Why Do Some Cast Items Require Machining?

    In some cases, an item produced through the sand casting process requires machining, painting, or another process to bring it to completion. Oftentimes, the item will have extraneous material necessary to make a good cast but not meant to be part of the finished design. At other times, fine detailing is needed and can be added after the cast is completed. Cast Technologies has a CNC machine shop on-site in order to deliver a finished product that meets your needs. This allows us to serve our customers better, as we take responsibility for all the processes the part requires to meet its design specifications.

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  • What Is Heat Treatment?
    Dec 15, 2022

    We have two quench furnace and a anneal furnace. For the castings parts with high class material, such as wheel brake wehd, piston cylinder, frame  etc. to make sure stable mechanical property, usually will be used with heat treatment.

    Heat treatment is a thermal process that accomplishes three primary improvements to the material properties of metal castings: 

    • Improving mechanical properties
    • Enhancing corrosion resistance
    • Reducing residual stresses

    The heat treatment process begins with heating the metal casting to the desired temperature before cooling the metal in a controlled way to achieve the desired improvements. This heating and cooling process “locks in” the final metal microstructure and the improved material properties.

    Why Heat Treatment?

    As outlined above heat treatment is used to achieve a variety of desired outcomes for a metal casting.  Heat treatment can also be designed to reduce hydrogen levels, simulate in-service conditions, restore mechanical properties, and reduce stresses after a project is welded.  These various outcomes are achieved with different heat treatment processes.  The overarching objective of heat treatment is to achieve customer specification requirements and comply with industry standards. 

    What Types Of Heat Treatment Are There?

    While there are a range of different heat treatment processes available at Hengchang, some are used more often than others.

    Homogenizing Heat Treatment:

    This process involves heating the metal casting in a furnace to an extremely hot temperature and holding for an extended period to improve chemical uniformity by diffusion.  Homogenization is sometimes employed as a pre-treatment to make subsequent heat treatments more effective.  

    Normalizing Heat Treatment:

    Normalizing is heating the metal casting to an elevated temperature above the transformation temperature and then air cooling it back to room temperature.  This process alters the microstructure to reduce the variation in hardness and ductility within the casting.  The temperatures and times are typically lower and shorter than for homogenization.  Normalizing is often followed by tempering.  Tempering is heating the metal casting to a temperature below the transformation temperature to lower the hardness and improve the ductility of the metal.  

    Hardening Heat Treatment And Quenching Heat Treatment:

    The use of this treatment results in an improvement in metal casting mechanical properties, related especially to increasing hardness or durability.  It is often used for steel parts.  Metal is heated to an elevated temperature (above the transformation temperature) and then rapidly cooled (quenched).  This causes the softer initial material to transform its structure into a stronger one.

    Quenching cools the metal casting after the initial heating process. The quench is typically performed in oil or water, depending on the material and specification requirements.  Tempering is the last step in the hardening and tempering process and is required after the quench.  It involves reheating the metal at a low temperature (below the transformation temperature) to achieve final specifications.  Tempering lowers the as-quenched hardness, restores ductility, and reduces stresses of fully hardened steel.

    Anneal Heat Treatment:

    Annealing is heating and holding the metal at an elevated temperature followed by furnace cooling to obtain the desired hardness.  This is typically performed on “hardenable” ferrous alloys  to reduce hardness, increase ductility, and improve the machinabilityof the casting.  This process is often used on tool steels, alloy steels, and martensitic stainless steels to allow for quick rough machining prior to any hardening and tempering operation.   

    Solution Anneal Heat Treatment:

    Solution annealing is heating and holding metal at an elevated temperature to cause constituents like carbides and undesirable phases to go into solid solution and then cooled rapidly to hold these constituents in solution.  This process improves mechanical properties and the corrosion resistance of an alloy.  Austenitic and duplex stainless steels are typically supplied in the solution annealed condition.   

    Stress Relieving Heat Treatment:

    Stress relieving is heating to a relatively low temperature and holding for a long enough time to reduce residual stress within the casting.  The process typically employs controlled heating and cooling rates to minimize the development of new stresses.  Stress relieving is often done after rough machining prior to tight-tolerance finish machining work. 


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  • Comparison Between Ferrous Metals and Non-ferrous Metals
    Apr 07, 2023

    From skyscrapers to naval propulsion stystems, from automotive parts to petrochemical furnace tubes, there is no shortage of real-world applications for metal.  Metals come in a wide range of structures, properties, and applications but are commonly organized into two categories: ferrous metals and non-ferrous metals.  Below we explain the definitions, common types, differences, and popular applications of both ferrous metals and non-ferrous metals.

    Ferrous Metals:

    A ferrous metal contains mostly iron.  Ferrous metals are common and make up the bulk of castings in the metal castings industry.  Typically, ferrous metals are stronger than non-ferrous metals and heat treatment can further improve their material properties


    Common Ferrous Metals:

    Common ferrous metals include:

    • Steel
    • Stainless Steel
    • Wrought Iron
    • Cast Iron
    • Low, Medium, and High Carbon Steel

    Non-Ferrous Metals:

    A non-ferrous metal is a metal that does not have iron.  Except for iron, all pure metals are non-ferrous.  Metal technology has continually developed throughout history, but natural non-ferrous metals still play a vital role for critical, real-world applications such as defense, process equipment and renewable energy .

    A prominent non-ferrous material is copper-based alloys – bronze and brass.  Brass is a copper-based alloy that has zinc as a principal element, while bronze does not have zinc or nickel as the principal element.  More on Bronzes and non-ferrous metals can be found here: What is Non-Ferrous Metal?

    Common Non-Ferrous Metals:

    • Bronze and brass
    • Aluminum
    • Lead
    • Nickel
    • Zinc
    • Gold
    • Silver

    Key Differences: Ferrous Vs. Non-Ferrous Metals


    Iron is magnetic, so ferrous metals have magnetic properties.  Non-ferrous metals do not have magnetic properties. Iron has magnetic properties due to its electrons becoming easily aligned to a magnetic field.  This property allows ferrous metals to be ideal for electrical projects – a prime example is induction heating.

    Corrosion Resistance

    Ferrous metals are often not ideal for applications where corrosion is a concern. Iron reacts with water to form a layer called hydrated iron (III) oxide, commonly known as rust. One notable exception to ferrous metals is stainless steel. This material was designed, among other things, to provide corrosion resistance. 

    Non-ferrous metals form oxide layers that function as barriers to water.  These layers provide a high degree of corrosion resistance.  This is a major reason copper pipping has traditionally been used for water pipes in homes, for example.


    Ferrous metals are typically stronger than non-ferrous metals. Steel is a prime example of one of the strongest metals. Combine that with its low cost and steel is a natural choice for building structures and other projects requiring high degrees of tensile strength. Titanium is stronger than other non-ferrous metals, but due to its high price, it typically makes for a poor selection for large projects like building structures.

    Common Applications

    Ferrous Metals Common Applications

    • Shaft sleeves
    • Heat exchangers
    • Pressure vessels
    • Calciners
    • Centrifuges
    • Hydraulic cylinders
    • Petrochemical components
    • Chemical & food processing equipment 
    • Pump & valve components
    • Catering Equipment
    • Train parts

    Non-Ferrous Metals Common Applications

    • Bearings
    • Bushings
    • Gears
    • Sleeves
    • Wear rings
    • Pump & valve components
    • Automotive engines
    • Fastener
    • Wiring kits
    • Pipes

    Ferrous Vs. Non-Ferrous Metals: Conclusions

    The differences between ferrous and non-ferrous metals are important, but that does not mean that the choice is clear for every project. It is critical to understand the various chemistries and how they will react to their application environment . Both ferrous and non-ferrous metals are vital to countless critical applications. We--Zhangzhou Hengchang are here to help with your project and identify the appropriate alloy for your specific application.

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  • What is a Foundry
    Jun 23, 2022

    Human beings left the Stone Age behind roughly 4,000 years ago when the Bronze Age began, although some foundries go back even further. The team at Cast Technologies takes great pride in coming from a long line of skilled craftsmen that reaches back to the ancient world. We are today using processes based on the same principles as those used by our ancient ancestors to radically change and modernize the world. While people might think of things like electricity, the printing press and computers as the building blocks of the contemporary world, the truth is our way of life rests to a very large degree on the work of foundries: Automotive, air travel and energy production are just three industries that heavily depend on cast items. You depend on multiple cast items every day of your life.

    Naturally, modern foundries bear little resemblance to the primitive technologies that man invented to make weapons and tools from simple bronze alloys, but the ideas are much the same: Melt a mixture of metals together and pour the liquid into some kind of mold. Making a bronze spearhead uses much the same technology still used for making parts for a power generator.

    The ancients made things like weapons and plows, allowing them to put aside their more primitive stone tools. Today, foundries make an almost infinite number of items we rely on in modern life, including car engines, pipes, chains, aircraft parts, tools and many other metal components. Of course, foundries today aren’t limited to bronze, but can cast countless metal alloys depending on the characteristics required by the finished item. 


    How Has Foundry Technology Changed?

    Foundries have evolved considerably, thanks to advances in technology and the science of metallurgy. Initially, charcoal fires were used to power little furnaces hot enough to melt metal, but now gas or electric heat are used to power more advanced furnaces. 

    Early foundries were a dangerous work environment, but modernization and mechanization have made them much less hazardous. For example, pouring molten metals into molds via a robot or other automated equipment is much safer than pouring by hand using a ladle. 

    Another change in foundries involves the methods used to placing the molten metals into molds. Traditional gravity pours are still used, but there are other methods available now, including vacuum or pressurized gas pours.


    A Simple Explanation of the Foundry Process

    Imagine you are living a few thousand years ago and you wanted to cast a simple item, such as a flat disk, in metal. The easiest method would be something called sand casting.

    You might start by carving something called a pattern from wood. Once you had your desired shape just as you wanted it, you could sink it into a sandpit and then — very carefully! — you would remove your wooden model from the sand. Done right, this would leave a perfect impression of your wooden model in the sand. 

    Next, you would prepare your metal according to the characteristics you wanted your finished item to have. Perhaps you’d follow the ancient recipe of one part tin to nine parts copper. You’d need a small furnace, a clay melting pot and of course a hot charcoal fire for melting. Yes, primitive charcoal-fired furnaces can indeed get hot enough to melt copper and tin together, although it’s much easier to achieve the necessary temperatures in a modern foundry.

    Once your metals had melted together, you’d carefully pour your mixture into the sand cavity and let the metal cool. Finally, you’d remove the solidified metal disk from the sand. If all went well, you’d have a perfect metal copy of your wooden disk.

    Now let’s imagine you wanted to make a more complex casting. You might want to make your item in two different sections, a top and bottom. This is called a split pattern, and the upper section is called the cope, while the bottom section is called the drag. 

    Even more complex designs can be made using something called a core. The core is inserted into the mold to create a hollow area. 

    Now imagine you needed your item to have a smoother finish. You could smooth it out by sanding or grinding. Today, you might sandblast the surface, sand it or machine it smooth with a grinder. This same general process is used in making everything from the simplest tiny items, such as jewelry, to the most complex and large parts weighing hundreds of pounds, such as wind turbine blades.

    After the item comes out of the mold, further processes may be used if necessary. Cast Technologies has an on-site machine shop to add the finishing touches to any component.

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  • Advantages and Disadvantages of Casting Pattern Classes Types
    Jun 23, 2022

    The table shows the advantages and disadvantages of the different classes of pattern equipment used by sand casting process.


    Pattern Type
    Advantages Disadvantages
    Wood Loose Low cost to produce. Use to produce plastic patterns. Easily modified. Not suitable for production batches unless converted into plastic before becoming worn. Tend to become inaccurate and to produce poor surface finish.
    Hardwood Inexpensive for small-batch production. Can be used as masters for plastic patterns. Fairly easily modified but expensive if multiple impressions involved. Fair wearing properties. With care, will remain reasonably accurate over fairly long periods. Not suitable for high-volume production.
    Plastic Inexpensive to produce. Urethane technology provides good wearing properties and accuracy. Easily modified depending upon the materials used. Suitable for high-volume production patterns with the same dimensional tolerances as metal patterns. Urethane technology has reduced many of the disadvantages of early plastic pattern materials.
    Metal Excellent wearing properties. High standard of accuracy and stability. Suitable for high-volume production and shell molding. CAD/CAM improvements are greatly reducing cost and lead time requirements. Costly. Difficult to modify. Equipment is less adaptable for movement from one foundry to another.
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  • Casting Competition: Sand Castings vs. Permanent Mold Castings
    Jul 22, 2022

    Sand castings or permanent mold castings? Since we offer both casting processes here at Hengchang Foundry, we often get posed this question. What is the difference between these two casting processes and which one is better suited for your application? Let’s clear up the casting confusion with a cursory overview.

    Sand Castings: A one-time sand mold is produced, which may contain one or more impressions of the part. Molten metal is poured into the sand mold, then following solidification and cooling, the sand is broken away and the casting is removed. In most cases, the sand is recycled and reused. So when is sand casting the appropriate method? When the production is suited for low and high volumes, the process is driven by material and mechanical casting property requirements, only moderate surface finishes and dimensional tolerances are needed, low tooling costs are needed, and when size and configurations dictate that the part can only be made as a sand casting. There are additional considerations that may have to be taken into account, and it is recommended that the user consult with the foundry prior to finalizing part design.

    Permanent Mold Castings: Unlike a sand casting, the mold is made from cast iron or steel, allowing for one or more cavities depending on the geometry of the part. The process is best suited for mid to higher volumes, when the part configuration dictates this type of casting, or the process is best suited for the application of the casting. The molds are in, most cases, fully CNC machined with the parting surfaces aligned with a locking system that provides good repeatable casting dimension conditions. When compared to sand castings, permanent mold castings have improved surface finishes, less machining allowances required, and closer net shaped profiles which are made possible by the metal mold configurations. Unlike sand castings, however, permanent mold castings are limited in size and the tooling proves to be more expensive (though part price tends to be lower!). Again, consult with a foundry to determine the right process for your needs!

    Do you better understand the difference between sand castings and permanent mold castings? Have you decided which is better for your specific applications? See our website for more information on.

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  • Investment Casting vs. Sand Casting — What’s the Difference?
    Jul 22, 2022

    Several casting methods exist for producing the machine parts required for industrial manufacturing processes, including sand and investment casting . Here, we will explore some key similarities and differences between the two. 

    Sand Casting Process 

    Metalworkers widely use sand casting technology because it is suitable for casting steel, iron, brass, and most nonferrous alloys—as well as for final products that weigh anywhere from less than a pound to thousands of pounds. The sand casting process begins with creating a sand mold. In a traditional foundry, after making the desired pattern or model of the final product from hardwood, urethane, or foam, sand is compacted around it to form the mold. In order to maintain its shape, the sand is initially treated with a bonding agent known as binder, which improves adhesion between its particles. The pattern is then removed by splitting the sand mold apart into two or more sections. These sections are then bound to receive the molten metal through a delivery system referred to as the gating system. After the metal sufficiently cools and solidifies, the final product is recovered by removing the sand through a shake-out process.

    Advantages of Sand Casting 

    Some key benefits of sand casting are outlined below:

    • Low operational costs
    • Can cast ferrous and nonferrous materials
    • Suitable for casting large parts
    • Relatively easy to change the design of the mold
    • Fast lead time 

    Investment Casting Process

    Also known as lost wax casting, investment casting technology is reliable for complex and detailed components. Metalworkers use it to create a final product with a near-net shape, leading to lesser material, machining, and labor costs compared to other forms of metal casting. 

    The investment casting method begins with molding wax into the desired cast and coating it with refractory material, such as ceramic. Applying heat melts out the wax, leaving an empty shell with the void to be filled shaped in the geometry desired. Molten metal is then introduced into this pre-heated shell. As soon as it suitably cools and solidifies, it is recovered by shattering the shell. 

    Advantages of Investment Casting 

    Some major advantages of employing investment casting include:

    • Capable of casting ferrous and nonferrous materials 
    • High levels of accuracy 
    • Can cast thin-walled products with complex designs 
    • Smooth surface finishing 
    • Lesser need for extra machining and finishing  

    Investment Casting vs. Sand Casting Comparison

    Both investment and sand casting have experienced significant improvements over the years—geared at minimizing the quantity of metal used and reducing extensive finishing and machining requirements. Although they are similar in some ways, some notable differences exist between them. 


    A few similarities between both casting methods include:

    • They can both cast ferrous and nonferrous materials 
    • Metalworkers shatter the molds to recover the finished product in both methods
    • They both require a molten metal delivery system  


    There are some fundamental differences between investment and sand casting, including:

    • Casting time
    • Quality of appearance
    • Materials
    • Design
    • Dimensional tolerance
    • Range of products
    • Mass production  

    Casting Time

    The molding cycle for sand casting is short, while the investment casting process takes longer.

    Quality of Appearance

    The final product from sand casting is usually rough depending on the sand used. Other defects include clip sand, sand wash, and gas holes. Meanwhile, products from investment casting are significantly smoother.


    Materials needed for investment casting, such as paraffin wax, sodium silicate, etc., cost more than those required for sand casting (sand, binder, etc.). Sand casting is relatively cheaper.


    Metalworkers can achieve more complex designs with investment casting, while sand casting may require extra tapering and machining to achieve the desired geometry. Sand casting patterns are more cost effective and require much less time to modify than the tooling required to manufacture investment castings, if design changes are required during a production run.

    Dimensional Tolerance

    With the high dimensional tolerance of investment casting (CT 4-6), finished parts can have thin walls, while finished parts from sand casting have a minimum wall thickness of 3 to 5mm because of their lower-dimensional tolerance (CT 10-13).

    Range of Products

    The adaptability of sand casting is broad, and as a result, it can be used for a wide range of castings, including ductile iron, grey iron, steel, aluminum, etc. Although investment casting can be used for other metallurgies, they are generally suitable for steel castings.

    Mass Production 

    Since investment casting can ensure consistency, it is suitable for mass production. Sand casting, however, cannot promise such consistency. Hence, mass-producing finished parts are more challenging using sand casting methods.

    Which Method Is Right For You?

    Knowing the appropriate method requires you to put some factors into perspective. Different materials are well suited for different products. Therefore, you must know the materials suitable for your product since it can help you determine the better-suited casting method. You must also consider the possibility of mass production and that each casting method requires different cycle times to inform your decision. Additionally, the overall casting cost must be considered. Ultimately, it is up to you to select the method which overall casting benefits for your project or application.


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