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INDUSTRY LEADING INVESTMENT CASTING PROCESS
What Is Investment Casting?
Investment casting, often referred to as precision casting or lost wax casting, is a sophisticated and highly precise metal casting process known for its ability to produce components with exceptional dimensional accuracy, intricate detail, and superior surface finish. The investment casting process ideal for manufacturing complex metal parts with minimal to no machining required. This step-by-step process starts by forming a ceramic shell around wax patterns. Molten metal is then poured into the shell, melting the wax away and leaving the metal to solidify in the mold, replicating the final casting’s exact shape.
Investment casting is particularly suitable for producing small to medium-sized components with extremely tight tolerance requirements and complex internal structure, and its versatility allows for significant design freedom, thus making it ideal for many demanding industries for a whole spectrum of applications. At Taiyuan Simis Investment Casting Co., Ltd, we offer custom investment casting services to meet your specific project requirements.
Over the years, we have made a huge technological advancedment, A key change is switching to silica sol binder from traditional water glass in the shell building step. This significant change eliminates harmful hardening agents like ammonium or aluminum chloride, improving both worker safety and casting quality. We’ve also drastically cut silica sol shell drying time from eight hours to just one hour per layer, boosting production speed and shell strength.
Our advanced silica sol investment casting process now handles a wider range of materials, producing both carbon steel castings and alloy steel castings up to 50kg. This expansion reduces costs, particularly for these types of castings previously deemed expensive with silica sol.
Furthermore, our shell making is fully automated. Robots handle all steps, including air drying, with dedicated robots and chambers for each of up to eight layers. This ensures consistent quality, eliminates errors, and results in stronger, thinner, more breathable shells, ultimately delivering superior casting surfaces.
The Step-By-Step Investment Casting Process
Step 1: Tooling design and manufacture
The very first step of the investment casting process is tooling design. In this process, tooling is used for creating the wax patterns that replicates the shape of the final metal cast part. Software applications like CAD is frequently used to produce precise digital models, considering factors like metal shrinkage, gating, and venting.
Taiyuan Simis specializes in designing and manufacturing investment casting tooling from our own machining workshop. Our tooling experts use CAD software to create various mold types, including automatic and manual wax injection molds, and automatic opening molds, suitable for diverse casting designs. We pride ourselves on customizing tooling tailored to different wax machines and casting needs, which guarantees high precision and superior quality in every project.
Step 2: Wax Pattern Production and Assembly
The second step of the investment casting process is creating wax patterns that replicate the final design of the castings. To handle different casting designs and volumes, we use various types of wax injection machines—fully automatic, semi-automatic, and manual.
We also have a fully automated system for preparing and reusing mold materials. After the wax patterns are created, we check their dimensions and surface and make any necessary fixes, such as deburring the patterns.
Depending on the part’s structure, we then attach the wax pattern to a gate or riser rod to avoid shrinkage defects. Once these are assembled, the “wax trees” are welded together and then move along an automated line for shell building.
Step 3: Shell Building
After the wax patterns are assembled, we begin the next step of the investment casting process: shell building.
In this step, the wax patterns are repeatedly dipped into a ceramic slurry. Once fully coated, they are immediately covered with refractory materials, such as silica or zircon sand, depending on the type of casting metal. After the slurry and refractory sand dry, a strong shell forms around the wax pattern. This process is generally repeated 4-8 times until the shell is strong enough for de-waxing.
At SIMIS, a large portion of the shell building is performed by an automated robotic system. By using robotic arms and an automated transfer line, we ensure the shells are uniform and avoid any cracking during transfer to the next stage.
Step 4: De-waxing
Steam dewaxing is exclusively employed in our investment casting process. Our 3m³ dewaxing machine, at 0.7MPa, ensures rapid wax removal within 30 minutes. Post-dewax, high-strength shells reveal a fine, ceramic-like finish. As a result, our castings’ surface roughness and dimensional accuracy are improved by two grades over water glass binder methods.
Step 5: Shell Firing
For shell firing, we use a huge 30-meter tunnel kiln fueled by clean natural gas – it’s essential for strong investment casting shells. The kiln slowly heats shells from 200°C to 950°C to avoid cracking from sudden heat. This advanced kiln ensures shells are strong and precise, which is key to our casting quality.
6. Smelting and Pouring
The smelting and pouring is one of the most important phases in the entire investment casting process, representing one of the core strengths of our company. We possess the expertise to precisely smelt various materials, ensuring that the chemical composition requirements of the investment castings are met.
Our quality control extends to the stability of molten steel’s chemical composition, free from impurities or internal defects such as pores. Before tapping the molten steel, we subject it to three spectral inspections to verify its composition and perform temperature checks twice using a thermocouple. We employ the finest deoxidisers and slag-making agents to guarantee the quality of each casting.
During pouring, we utilise teapot ladles, effectively preventing impurities from entering the castings. We then conduct secondary deoxidation in the ladle to further enhance the internal quality of the castings.
7. Cooling, Solidification, and De-Shelling
After precisely pouring molten metal, the castings cool and solidify within the ceramic shells. Then comes de-shelling – removing the ceramic shell. At Simis, we’ve automated this with advanced, hanging-type equipment. Our system automatically removes dust and uses suspension to prevent damage during shell removal. It significantly reduces manual labor while ensuring efficient and precise de-shelling and dust removal.
Once de-shelled, the intricate castings are revealed. They then proceed to finishing, quality control, and inspection, guaranteeing they meet our high standards.
8. Finishing and Inspection
This is the last stage in the investment casting process, it is vital for making certain that our casting components meet stringent quality standards and specifications. We provide fully in-house machining, heat treatments, surface treatments and testing.
Taiyuan Simis is an ISO9001 certified manufacturer committed to delivering only the highest quality castings. To achieve this quality, we fully inspect every casting before it leaves our facility. Along with each casting, we provide comprehensive reports detailing chemical, physical, and mechanical properties, and dimensional data. We are equipped with cutting-edge testing equipment: ultrasonic testing, X-ray, and CMM and more.
Our Investment Casting Advantages
Investment casting offers numerous advantages such as complex shapes, tight tolerance, superior finish, and material versatility unmatched by other methods. Compared to sand casting, it achieves intricate details and smoother surfaces. When compared with die casting, it handles a wider range of metals, from steel to iron. In contrast to shell mold casting, investment casting provides an even finer surface finish and the ability to create more intricate and complex internal geometries. It also minimizes costly machining, delivering near-net-shape components. At SIMIS, our investment casting process offers several compelling advantages, delivering parts with the highest possible quality while achieving cost efficiency.
Intricate Designs and Complex Geometries
The investment casting process provides unparalleled design freedom for intricate, detailed parts. Taiyuan SIMIS leverages this process and expert tooling to guarantee industry-leading quality for complex geometries. Advanced software and techniques create precise tools replicating even the finest features.
Ceramic cores enable intricate internal shapes and undercuts, precisely formed within the mold and extracted after casting. The combination of advanced silica sol casting process, skilled engineers, and tooling expertise allows us to produce parts with unmatched complexity.
Excellent Surface Finish
The investment casting process is known for creating parts with a superior surface finish. We select premium wax for creating accurate patterns, high-grade refractory materials for building durable ceramic shells, and appropriate alloying compositions for the final castings. Excellent surface smoothness is the result of controlling every stage of the process, from the initial wax pattern creation to the final pouring of molten metal into the ceramic shell.
High Dimensional Accuracy
Achieving tight tolerances and high dimensional accuracy is a hallmark of our investment casting process. Our advanced silica sol casting process to deliver castings of exceptional precision for your projects. We can cast parts strictly according to your drawing requirements, meeting even demanding tolerances down to CT4 grades.
Material Versatility
One of the key advantages of our investment casting process is our ability to work with a wide range of materials. As an experienced investment casting manufacturer in China, we can cast various grades of stainless steel castings, carbon steel castings, and alloy steel castings, such as high-strength, high-nickel, and high-manganese steels, among others.
Cost-Effectiveness
For small to medium production runs, our investment casting process offers a compelling cost advantage: significantly lower tooling costs compared to other casting methods. While some tooling investment is required, it’s much less substantial than the tooling required for processes like die casting. This makes investment casting a highly cost-effective choice for smaller volumes. We further enhance this cost advantage through efficient automated systems, such as automated wax injection and shell building (reducing labor), and our deep process expertise (minimizing waste and maximizing efficiency). This results in high-quality parts through our investment casting services with significantly reduced overall investment casting costs.
Superior Quality
Quality is top priority throughout our investment casting process. Our automated systems, particularly our automated drying system, are crucial for achieving consistent, high-quality results. The automated drying system ensures uniform drying of the ceramic shells, greatly minimizing human error and variations in the drying rate. Our controlled drying process creates stronger, more consistent shells, which directly translates to higher-quality castings with fewer defects and improved dimensional accuracy. This commitment to automation and precision ensures top-notch quality in every casting.
Repeatability and Consistency
A prominent benefit of our investment casting process at Taiyuan SIMIS is the high level of repeatability and consistency we achieve. Once the tooling is made, we can produce identical castings in every production run, ensuring consistent quality and performance for every part. Our efficient production scheduling management system is key to maintaining consistent delivery and meeting project timelines.
In addition to process control and scheduling, we also prioritize strict material management. We utilize dedicated pouring equipment (ladles) for different materials to prevent cross-contamination and maintain the specific properties of each alloy. Our well-organized facility with clearly labeled sections for each customer’s materials further ensures proper handling, storage, and traceability throughout the entire production process.
Reduced Post-Processing
A significant advantage of our investment casting process is the reduced need for post-processing thanks to the near net shape nature of the castings. Because of the inherent precision and excellent surface finish, many parts can be used as-cast, meaning they don’t require additional machining, grinding, or polishing. This near net shape capability saves you valuable time and reduces manufacturing costs.
Wide Applications Across Industries
The versatility of our investment casting process allows us to serve a wide range of industries. Our castings are used in demanding applications across diverse sectors, including aerospace, automotive, railway, energy section, food processing, engineering machinery, mining and construction, agriculture, and many others.
Minimizing Environmental Impact
Many investment casting manufacturers in China, especially those using the water glass casting process, have faced production delays due to failing local environmental inspections. At Taiyuan SIMIS, we prioritize minimizing our environmental impact through sustainable casting practices. We instead use advanced environmental protection equipment and employ an environmentally friendly silica sol binder which minimizes material wastage, contributing to a more sustainable manufacturing approach.
Frequently Asked Questions (FAQs)
What's The Lead Time of a New Design?
The lead time for investment casting often depends on the part’s design, including its structure, complexity (such as thin walls or intricate internal features), material (as some less common grades can take time to source), and order quantity, among other factors. Generally speaking, for any new design, the tooling and sample manufacturing can take about 30-45 days. For very complex designs, this period can extend even longer. After sample approval, production typically takes about 30-60 days, depending on the order quantity. This is just an estimate, as the actual lead time can vary based on specific designs. To get an accurate lead time for your project, speaking with our experts is the best approach.
Are You Using Silica Sol or Water Glass Technique?
We are using silica sol investment casting process, we have 2 investment casting workshops, one of them is using a method called ‘rapid drying process’, and the other is standard silica sol casting. Our advanced rapid drying technique is used solely for casting carbon steel and alloy steel parts. And our silica sol process is dedicated to producing stainless steel castings. Both methods can achieve very high-quality parts, suitable for different industries. However, I recommend consulting with our experts regarding your requirements, so we can choose the best process for you.
How Do You Deal With Parts with Defects?
Realistically speaking, just like any casting process, defects can happen in investment casting. Some can appear as early as the wax tree assembly stages, such as defective wax models. Some can appear after raw castings have been produced. And some can appear after machining. Depending on the types of defects, we choose several different methods to tackle them, such as welding repair for defects like shrinkage and gas porosity, misruns, sand inclusions, etc. If unfixable, we then scrap these castings and melt them down for the next batch. However, no parts with defects can leave our factory, so we always do 100% inspection on all castings, including visual inspection, mechanical testing, chemical testing, dimension checking, and more.
What If My Part is Too Heavy?
Investment casting is a very robust casting process, but there are certain limitations, such as size and weight. If your part is too heavy (let’s say over 200kgs), we can recommend that you use our sand casting or lost foam casting services, as we have a sand casting factory and a lost foam casting workshop for parts that are particularly large and heavy. So, let us know your part’s dimensions and weight, and we can help you decide which process is best for you.
Can You Do Heat Treatments?
Yes, we have heat treating workshops in our foundry, we can do heat treatment according to your specific requirements, so just let us know.
Can you Do Surface Treatments?
Yes, of course, we can do various surface treatments in our workshops, including painting, powder coating, anodizing, sandblasting, galvanizing, phosphating, e-coating, electroplating, and more. Just let us know your requirements.
Can You Do Machining?
Yes, we have 3 machining workshops equipped with advanced CNC machining centres. We are capable of doing all kinds of machining operations on all our investment casting parts. Our in-house machining capabilities make us very cost-competitive and can help you save cost.
I'm New to Investment Casting and I don't know If I Should Choose This Process, Can You Help Us Decide?
Investment Casting has several advantages yet, it comes with some limitations, not all parts are suitable to be cast by the investment casting process. To learn more about investment casting advantages and disadvantages, you can check out our detailed article. SIMIS is an experienced foundry. Not only can we recommend the best process for your parts—whether it be investment casting, sand casting, lost foam casting, shell molding, or die casting—but we can also help you choose the most appropriate material grades, fix design flaws, and help you simulate the outcome from each casting process, and eventually, help you select the best process from different perspectives (cost, application scenarios, requirements, etc.).
Can I Visit Your Factories?
Absolutely! You can visit our facilities at any time. Just contact us in advance so we can arrange your visit.
Credentials Beyond Compare
We’re a professional investment casting manufacturer and a member of the China Foundry Association. Our long-held ISO 9001 certification and our TUV certification show our dedication to quality in every aspect of our work. This means our customers can always expect top-quality products and services that meet all their needs and industry standards.