Investment Casting Process | Lost Wax Investment Casting | Investment Casting Foundry | Mechanical Engineering

发布日期:[12-07-26 18:59:48] 浏览人次:[]

Investment Casting (or) Lost Wax Method

A wax duplicate of the desired casting is created to be invested into a "Ceramic Slurry".

The slurry covered investment can be dipped into alternating coatings of sand and slurry until a suitable thickness of shell is achieved that can hold the molten metal after the investment is burnt out.

The "Burn-Out" process requires that the investment and coating are inverted in an oven that is fired to 1800F so that the investment can flow out and be recovered. The refractory coating is also cured in this procedure.

This process is beneficial for casting metals with high melting temperatures that cannot be moulded in plaster or metal.

Parts that are typically made by investment casting include those with complex geometry such as turbine blades or fire arm components. High temperature applications are also common, which includes parts for the automotive, aircraft, and military industries.

01-lost wax method-gated patterns-chess piece manufacturing

Principle

Method also called as precision investment casting. The method involves the use of expendable Pattern with a shell of refractory material surrounded to form a casting mould. Since the pattern made up of wax is melted out and gets destroyed. That is why the name-"Lost wax method".

Process parameters of Investment casting

Process principle

Refractory slurry is formed around a wax or plastic pattern and allowed to harden. The pattern is then melted cut under mould is baked. The molten metal into the mould and solidifies.

Size limits

As small as (1/10) inch but usually less than 10 lb.

Thickness limits

As thickness as 0.025 inch but less than 3 inch.

Typical tolerance

Approximately 0.005 inch.

For the first inch and 0.002 inch for each additional inch.

Draft allowance

Not required.

Surface finish

50 to 125 micron.

01-investment casting process-lostt wax casting-lost wax molding-lost wax method

Procedure

1. Produce a master pattern

The pattern is a modified replica of the desired product made from metal, wood, plastic, or some other easily worked material.

2. From the master pattern, produce a master die

This can be made from low-melting-point metal, steel, or possibly even wood. If low-melting-point metal is used.

3. Produce wax patterns

Patterns are made by pouring molten wax into the master die, or injecting it under pressure, and allowing it to harden. Plastic and frozen mercury have also been used as pattern material.

4. Assemble the wax patterns onto common wax sprues

The individual wax patterns are attached to a central sprues and runner system by means of heated tools and melted wax. In some cases, several pattern pieces may first be united to form a complex.

5. Coat the cluster with a thin layer of investment material

This step is usually accomplished by dipping the cluster into a watery slurry of finely ground refractory material.

6. Produce the final investment around the coated cluster

After the initial layer is formed, the cluster can be redipped, but this time the wet ceramic is coated with a layer of sand and allowed to dry. This process ca

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