1) Production of molding materials

The intent of making the molding material is to mix the various original materials constituting the molding material into a uniform unit, and to make the condition of the molding material conform to the requirements of the limiting mold.

In the production, the raw materials are first melted and mixed by heating, and then the molding materials are vigorously mixed under cooling conditions, so that the molding material becomes a paste condition for limiting the melting mold. Sometimes there is a condition in which the mold material is melted into a liquid to directly cast a mold.

2) Retraction of the molding material.

When resin-based molding materials are used, because of the high quality requirements of the investment molds, the molding materials are often used to restrict the casting of the castings. The mold material recovered after demolding is used to make a casting mold for the riser system after remelting and filtering.

Production of investment molds and modules

1) Production of investment mold

In the production, most of the pressure is used to press the paste molding into the molding method to make the investment mold. Before limiting the melting, a thin layer of the parting agent is applied to the outer surface of the molded type to remove the investment mold from the pressed type. When the wax-based molding material is restricted, the parting agent may be oil, turpentine, etc.; when the resin-based molding material is restricted, a mixture of sesame oil and alcohol or silicone oil is commonly used as a parting agent. The thinner the layer of the parting agent, the better, so that the investment can better replicate the appearance of the pressed type and improve the brightness of the external appearance of the investment. There are three ways to limit the investment, the plunger pressurization method, the air pressure method, and the piston press method.

2) Assembly of investment mold

The assembly of the investment mold is to combine the investment mold constituting the casting and the investment mold constituting the pouring riser system. There are two main methods:

1. Soldering method Use a flaky soldering iron to melt the joint of the investment mold to weld the investment mold together. This method is more extensive.

2. Mechanical assembly method In many production of small investment castings, the mechanical assembly method has been widely used in foreign countries. The selection of such modules can greatly improve the module combination and power, and the working conditions are also improved.

  Mold material

The function of the mold data should not only ensure that the investment model with accurate dimensions and high brightness, good strength and light weight can be conveniently produced, and it should also create conditions for the production of the shell and the achievement of outstanding castings. The molding material is generally made of a wax material, a natural resin, and a plastic (composition resin). The molding materials which are mainly made of wax materials are called wax-based molding materials, and their melting points are relatively low, ranging from 60 to 700 C. The molding materials which are mainly made of natural resin are called resin-based molding materials, and the melting point is slightly higher, about 70~ 1200C.

When a wax-based molding material is used, the mold material obtained after demolding can be taken back and used to make a new investment mold. However, in the cycle application, the function of the mold material will be deteriorated, the brittleness will increase, the ash content will increase, the fluidity will decrease, the shortening rate will be added, and the color will be browned from white. These are mainly related to the transformation of stearic acid in the model. Therefore, in order to restore the original function of the ancient mold material as much as possible, it is necessary to remove the soap salt from the old mold guess. The commonly used methods are hydrochloric acid (sulfuric acid) treatment, activated clay treatment and electrolytic recovery.

The process of investment casting is to make the investment mold. The investment mold is used to form the cavity of the refractory shell. Therefore, in order to obtain castings with high dimensional accuracy and high surface brightness, the primary investment mold itself should have high dimensional accuracy. And the brightness of the exterior. In addition, the function of the investment mold itself should be as simple as possible for the subsequent process of forming the shell. In order to obtain the above-mentioned high-quality investment mold, in addition to the good molding type (the mold for limiting the investment mold), it is also necessary to select suitable molding materials (referred to as molding materials) and a reasonable molding process.