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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. It is a process ideal for manufacturing complex metal parts with minimal to no machining required. This process involves 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.
The Investment Casting Process
1. Tooling design and manufacturing
In investment casting, tooling design is crucial for creating the wax or plastic patterns that become the mold for the metal part. CAD software is often used to produce precise digital models, considering factors like metal shrinkage, gating, and venting.
Taiyuan Simis specializes in designing and manufacturing investment casting tooling in-house. We 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 custom tooling tailored to different wax machines and casting needs, which guarantees high precision and superior quality in every project.
2. Wax Mold Production
To handle different casting designs and volumes, we use various wax injection machines – fully automatic, semi-automatic, and manual. We also have a fully automated system for preparing and reusing mold materials. After creating wax patterns, we check their dimensions and surface, and make any necessary fixes. Depending on the part’s structure, we then attach the wax pattern to a gate or riser rod to avoid shrinkage defects. These assembled “wax trees,” welded together, then move along an automated line for shell making.
3. Shell Making Process
At Taiyuan SIMIS, our investment casting process features significant technological leaps, particularly in shell making.
A key change is our switch to silica sol binder from traditional water glass. This 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 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.
4. Mold Dewaxing
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.
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.
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.
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, 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 at a competitive price.
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.
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.
