The Concept of Investment Casting
The model is made of fusible material, and the shell is made of several layers of refractory material covered on the surface of the model. After hardening, the model is heated again, so that the fusible material melts and is discharged out of the model, thus obtaining the casting model, and then the liquid metal can be poured to obtain the metal casting parts. Because the main component of the fusible material is paraffin, therefore, investment casting is also known as lost wax casting.
3D Molding Technology
There are different molding technologies for 3D printing. The main molding technology being talked about here is stereolithography (SLA). The tolerances of SLA parts are typically less than 0.05 mm, and the surfaces of products made by SLA are very smooth. Given its superior quality qualities, SLA is particularly suited to the creation of high-precision cast molds. SLA is a well-established 3D molding technology that can be used to create high-precision molds.
Advantages of 3D Printing for Investment Casting
With 3D printing technology, large-size molds can be printed in one go. Not only does it significantly reduce the time of making a mold, but the large-sized parts also reduce labor costs because the smaller the number of parts, the less bonding is required. For example, it takes only 2-3 days to make a 66-centimeter diameter mold, costing only about $6,000-$15,000. By traditional means, however, it would take months and cost $20,000 to $30,000 to make a wax mold of this part alone.
One of the major difficulties with investment casting is shrinkage during the manufacturing process. One of the advantages of 3D printing is that you only need to calculate the shrinkage of the metal, not the mold. This is because models made through 3D printing are more accurate and have fewer errors than prototypes made from wax molds. Because of this greater accuracy, 3D investment casting can meet the customers’ requirements in the aerospace industry.
Source of the 3 Images: 3dsystems
The molds produced through 3D printing are more fault tolerant. If something goes wrong during prototyping, or if a part fails to meet expected standards, it only takes a few days to re-design and re-produce the prototype, unlike the traditional process that takes weeks or months to modify wax molds. Moreover, the new 3D printing material is a transparent, polycarbonate-like material that does not contain heavy metals such as antimony, making it less susceptible to imperfections when creating the final metal part. When applied to investment casting, it produces almost no residue, which saves a lot of post-processing time while ensuring quality.
Application of 3D Priting + Investment Casting
By printing molds for investment casting through 3D SLA technology, there is no need for making wax molds, and the parts required by the customer can be made at a very high rate of speed. Because the aerospace industry often requires small quantities of highly complex parts, 3D investment casting products are very well suited to the needs of the aerospace market.
Engine nozzles are an excellent product for 3D printing+ investment casting. Engineers successfully integrated 20 parts and their assembly steps into a single structure, resulting in a waste-free, dimensionally precise, time-saving, and about 25% weight-saving industrial artifact that was successfully mass-produced.
The turboprop engine is another testament to this. Engineers consolidated 855 parts into 10 3D printed components, allowing the engine to reduce weight by 5% and oil consumption by 1%. The process allowed the team to turn a dream into a reality in just two years, whereas before it usually took years, up to a decade, to go from design to application.
Image Source: GE
Process of 3D Printing + Investment Casting
Mold Making | 3D printing for mold making can be made quickly, regardless of their complexity. Without the mold-making process, it saves a lot of time and money. The main printing material is photosensitive resin which has a small ash content. By using this kind of resin, the surface of the final part is smooth and the dimension tolerance is small.
Shell Making | Before hanging the first layer of paste, carefully observe for the appearance of air bubbles when cleaning the mold. If there are, the mold is not sealing well. Another thing to remember is to avoid damage to the mold by buoyancy when the mold is immersed in the slurry.
Roasting | Roast the mold at a high temperature and keep the temperature at 800-1100 degrees for two hours (according to the size of the parts, appropriately extend).
SLA casting special resin begins to soften at 50 ~ 60 ℃. At more than 300 ℃, the molecular structure of the resin collapses. Reaching 600 ℃, the resin decomposes into carbon dioxide, water, and a small amount of residue. At about 800℃ the resin disappears completely.
Remove the Residual Ash | Residual ash will affect the product quality and cause internal defects. So it is necessary to remove the residual ash carefully.
Preheating and Pouring | The model needs to be preheated before pouring. After that, the liquid metal can be injected into the mold.
For more information on the investment casting process, please read metal casting.
Image Source: 3duke & Admateceurope
3D investment casting can produce high-quality products at a short production time, effectively reducing the risk in the supply chain. All of these make 3D investment casting has unlimited potential in the future industrial manufacturing field, more high-end castings will be made by 3D investment casting.
Our Metal Casting Service
With years of experience in metal casting, Tengye has adapted the manufacturing and services we offer to meet the evolving needs of our clients.
Experiences | Our team has years of experience in metal casting for various industries and can handle those challenging projects.
Tight Tolerances | Our services in high-end industries lead to the production of precise parts with tight tolerances.
Wide Range of Materials | We have served a wide range of clients and could offer a variety of rapid prototype materials and finishing processes.
No MOQ | We can handle one-off prototypes and low-volume parts.
Rapid Turnaround | Our capacities allow us to finish your prototyping projects in days.
