What is Investment Casting Process?

Investment casting, or lost-wax casting, is an advanced metal forming process to create complex, high-accuracy metal parts. This process uses a ceramic mold that coats a disposable wax pattern with ceramic slurry. The wax is melted from the ceramic shell mold, leaving behind a hollow mold cavity to cast intricate or detailed metal parts.

Neway Investment casting service is typically used to manufacture critical aerospace components, turbine blades, medical implants, jewelry, and other high-value parts in metals that are difficult to machine. This process enables the production of complex geometries with excellent surface finishes impossible with other casting methods.

Steps in the Investment Casting Process

Investment casting involves the following key steps:

1. Pattern Making The process begins with creating a precision wax pattern replicating the final metal part. The patterns are injection molded for accuracy. Common wax pattern materials include paraffin, beeswax, carnauba wax, and epoxy resins. Rigid cores may be inserted for hollow parts.

2. Mold Assembly The wax pattern is attached to a sprue to form the pattern cluster or tree. It is repeatedly dipped into a ceramic slurry, stuccoed with coarse ceramic grains, and air-dried until it forms a hard ceramic shell around the patterns. The ceramic mold typically involves 4-8 coats for adequate strength.

3. Dewaxing, the ceramic mold is heated in a flash fire dewaxing oven to melt out the internal wax pattern from the shell. It leaves behind a hollow mold matching the shape of the original wax pattern.

4. Firing The ceramic shell is hardened by firing it in a furnace between 1600-1800°F. It drives off any residual wax and sinters the ceramic particles into a robust and fused mold capable of withstanding the high temperatures and pressures of molten metal pouring.

5. Casting The fired ceramic mold is filled with molten metal via gravity, pressure, or vacuum pouring. The investment mold enables the casting of alloys with high melting points. The metal solidifies into the precise shape of the mold cavity.

6. After solidification, the casting is removed from the mold by breaking away the ceramic shell using mechanical vibration, water jets, or chemical dissolution. It is known as divesting. The gates and sprues are cut off during the final casting.

7. Finishing The cast parts may optionally be cleaned, heat treated, or machined before finishing to achieve the required dimensions, visual appearance, and material properties. Thanks to the injection molded wax pattern accuracy, minimal finishing is required.

Advantages of Investment Casting

• High dimensional accuracy and smooth surface finishes

• Ability to produce complex geometries and intricate details

• Casts exotic alloys including stainless steel, superalloys, titanium

• Low labor requirements and high reproducibility

• Excellent for limited production quantities

• Minimal secondary machining required

• Can create hollow castings by using wax cores

• Suitable for casting large and small parts

Disadvantages of Investment Casting

• High tooling costs for wax pattern injection dies

• Long lead times of 4-12 weeks

• Size limitations based on pattern equipment

• Risk of ceramic shell cracking during metal pouring

• Limited to shorter production runs

• High scrap rates of 10-15%

• Restricted to smaller casting part sizes

Applications of Investment Casting

• Aerospace - turbine blades, impellers, structural castings

• Defense - armor, projectile shells, fittings

• Medical - implants, prosthetics, instruments

• Automotive - turbochargers, clamps, gears

• Food processing - valves, pipe fittings

• Jewelry casting

Investment Casting Alloys

• Stainless steels - 316, 410, 17-4PH, 15-5PH

• Cobalt and nickel superalloys - Inconel, Hastelloy, Rene

• Tool steels - H13, P20, 420 stainless

• Titanium and titanium alloys - Ti-6Al-4V, TiAl

• Refractory metals - tungsten, niobium, tantalum

• Precious metals - gold, silver, platinum

• Copper alloys - brass, bronze

These alloys are difficult or impossible to fabricate by other methods. Investment casting allows producing parts with exceptional material properties.

Pattern Materials for Investment Casting

The pattern material must burn, melt or vaporize out of the ceramic mold without residue. Typical pattern waxes include:

• Paraffin wax - the most economical option

• Beeswax - high strength, low ash content

• Carnauba wax - very hard with low shrinkage

• Epoxy resins - high accuracy and stability

Waxes are formulated with fillers for dimensional stability and low ash content. Pattern waxes are injected into dies under high pressure for precision pattern fabrication.

Investment Casting Ceramic Slurries

The prime slurry determines the surface finish quality. Zircon-based priming slurries deposit fine zirconia particles for highly smooth finishes. Backup slurries contain fused silica to build shell thickness and strength quickly. Both aqueous and alcohol-based slurries are used.

Stucco aggregate choices like fused silica, alumina, and zircon sands determine mechanical strength, permeability, and thermal shock resistance. The slurries are applied by dipping, brushing, or spraying techniques.

Investing in casting is an indispensable process for manufacturing exceptionally complex, high-performance metal components across critical industries. It leverages specialized wax pattern tooling, ceramic mold making, and molten metal pouring techniques to achieve exceptional as-cast part qualities and geometric intricacy.

Investment Casting Service at Neway

We pour our passion into every perfectly crafted part. Neway sculpts metal, plastic, and ceramic with meticulous care and cutting-edge capabilities into the extraordinary. Our commitment spans injection molding to investment casting and beyond. This year, we invite you to try our mastery and save 20% on first-time orders. Bring us your vision, and let our ingenuity take flight.