An introduction to investment casting process.
Investment Casting also known as precision casting or Lost wax casting, is a manufacturing process in which a wax pattern is used to shape a disposable ceramic mold. A wax pattern is made in the exact shape of the item to be cast. This pattern is coated with a refractory ceramic material. Once the ceramic material is hardened, it is turned upside-down and heated until the wax melts and drains out. The hardened ceramic shell becomes an expendable investment mold. Molten metal is poured into the mold and is left to cool. The metal casting is then broken from of the spent mold.

The term investment casting is derived from the process of “investing” (surrounding) a pattern with refractory materials. Investment casting is often selected over other molding methods because the resulting castings present fine detail and excellent as-cast surface finishes. They can also be cast with thin walls and complex internal passageways. Unlike sand casting, investment casting does not require a draft.

Though investment casting, also known as lost wax casting, has been around for thousands of years, there have been improvements to the method. The modifications are intended to improve the pattern development procedure and address the use of wax. Evaporative pattern casting is the general term for lost wax casting because the material used to produce the pattern is removed or evaporates.
Casting in Foam
Engineers can use it to produce three-dimensional renditions of their conceptualizations. It is a manufacturing process used to make decorative, elaborate, and intricate metal shapes, arrangements, and designs.
Investment Casting in Water Glass
Instead of ethyl silicate, the water glass is employed as the shell’s binding agent. The technique, which dates back to the 1950s, has a material cost and manufacturing cycle advantages. It has a simpler technique, operation, and parameters that may be accomplished by ordinary personnel, resulting in increased production and efficiency.
Casting with Direct Investment
The first approach involves carving the pattern by hand or machine to generate a one-up version that is then treated using the lost wax method. This method is used to make a prototype, produce small batches of final products, or determine dimensions.
Sand Casting
Sand casting is used to make huge pieces by pouring molten metal into a mold hole that has been formed out of natural or synthetic sand. The cavity is constructed by using a pattern, which is usually made of wood or metal and is the same shape and size as the actual item. The cavity is somewhat larger as a result of the pattern being slightly oversize, which compensates for the contraction of molten metal during cooling.

The ancient art and science of investment casting is also known as the lost wax process.
Investment casting was developed over 5500 years ago and can trace its roots back to both ancient Egypt and China. Parts manufactured in industry by this process include dental fixtures, gears, cams, ratchets, jewelry, turbine blades, machinery components and other parts of complex geometry.

Lost wax is a very literal alternative name for the process. The investment in refractory material is a covering that is formed wet, over a wax pattern. This covering is then allowed to dry, before baking at high temperature. This serves two purposes. First, the refractory investment is solidified and chemically fused to form a strong material. Secondly, the wax is burned away, making the investment a tough and hollow body that perfectly and precisely represents the now-absent wax, as a space to be filled with metal. Thus, the wax is lost, hence the naming of the process.

Investment casting is a manufacturing process in which a liquid material is poured into a ceramic mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is the casting, which is broken away from the ceramic mold to complete the process. The steps within the investment casting process are as follows:
Step 1: Engineering Review
The first step of this manufacturing process begins with a full Design For Manufacturing (DFM) review with the customer. This would include an evaluation of print dimensions as it relates to the investment cast process, wax injection mode build considerations such as gate placement, post-case material requirements and expected tolerances for fit, form and function of the part, and final inspection criteria to determine a mutually acceptable part.
Step 2: Mold Design & Build
The process begins with a precision-engineered wax injection mold to produce wax patterns representing the final part. These design considerations are discussed with the mold builder and a mold design is created. Our wax injection molds are built here at Aero Metals at our in-house mold shop. The molds are designed and built to reproduce millions of wax parts over its lifetime.
Step 3: Wax Pattern
The wax injection mold is quantified to run production and brought to the Wax Room for injection and assembly. Anywhere from one to 100 patterns are injected and placed or glued onto a pre-fabricated wax runner system known as a “tree” in our process. The populated tree of wax parts is also known a cluster (of parts). The tree cluster is then sent to the Dip Room for the next part of the process.
Step 4: Ceramic Mold Construction
The wax tree is dipped and completely enveloped into ceramic slurry, taken out, then completely coated in sand to create the first layer of shell, and then dried. This enveloping process of dip and sand is repeated 6 or 8 times with a drying period between each one. By repeating this process, it creates a lamination effect building a strong ceramic shell around the wax pattern as known as “investment”. The shell now runs through our drying system for 24 to 36 hours before removing the wax from the shell.
Step 5: De-waxing
The shell, which consists of the wax pattern and its coating of ceramic and sand, is placed into an autoclave to quickly remove the wax under extremely high pressure and steam heat. This vessel helps to hold the shell in place and the steam heat quickly melts the wax out creating an empty ceramic mold, hence the name “lost wax” casting. The ceramic shell is then moved to the foundry ovens to start the casting process.
Step 6: Foundry & Pouring
The mold is then placed into a high temperature oven, approximately 1000°C (1832°F), to cure (cristobalite) the ceramic mold and prepare it for accepting molten metal. The cured ceramic mold is removed from the hot oven and molten metal is immediately poured into the mold cup and its subsequent gating system, completely filling out the mold cavity with metal.
Step 7: Shell & Casting Removal
After the metal has cooled to the touch, the ceramic mold shell can be broken away from the part(s), and the casting(s) removed from, the now metal, tree. The ceramic shell is brittle and typically broken free by using water jets, vibration, and other methods. Once the tree is clean of the ceramic, the parts are removed from the gating system by either cutting off with a saw with vibration or liquid nitrogen.
Step 8: Finishing
Often, the part’s gate is removed by a grinding or machining post-cast operation. Further finishing such as heat treatment to anneal before machining, plating, or harden is completed before final inspection and shipping to the customer.

Steadfast dedication to the field of precision casting and machining for 30 years,Qianhao Metal is a global leading investment casting foundry.Backed up by our modernized workshops, reliable equipment and advanced manufacturing technology, Qianhao Metal is devoting to manufacturing high quality industrial products for our customers. We have abundance of experience investment casting process.