The Five Functions of Investment Casting Pouring System

The Five Functions of Investment Casting Pouring System

When designing the pouring system for investment casting, we must fully understand the functions of the pouring system before we can correctly design the pouring system. In the investment casting manual, the five major functions of the pouring system are mentioned, namely filling, shrinkage filling, wax removal, heat distribution, auxiliary tools, etc. Today, precision casting manufacturer Tianyao Metal will discuss these five functions in detail.

1. Filling, which is relatively easy to understand, is actually a channel function. The molten metal enters the mold cavity through the pouring system, forming the casting. But in reality, it's not that simple. The filling function needs to ensure accurate replication of the shape of the mold cavity to prevent casting defects such as insufficient pouring and cold shuts. It is also necessary to ensure that the metal liquid is poured and filled smoothly, avoiding gas entrapment, inclusions, and secondary oxidation of the alloy.

2. Shrinkage, this function is also very important. When the metal liquid cools and solidifies, the volume will decrease. If sufficient metal liquid cannot be obtained to supplement the space generated by shrinkage, the casting will produce shrinkage and porosity. The pouring system therefore performs a shrinkage function on the casting. The general order of filling and shrinking is to fill the sprue cup with a straight sprue; Vertical sprue and horizontal sprue; Horizontal sprue with inner sprue; Repair castings for internal gates and risers. Therefore, the order of cooling and solidification is casting - inner gate - transverse gate - vertical gate - gate cup, and riser. From the appearance, the ones that solidify first are relatively small and thin in volume and wall thickness, while the ones that solidify later are thick and large in volume.

3. Wax removal, this function is unique to investment casting. Just like sand casting uses wooden molds, which must be taken out the same way in the end, investment casting uses mold materials to create a pouring system, and ultimately melts all the mold materials, which is why it is called investment casting. Therefore, a major function of the pouring system is wax removal, which is responsible for smooth wax removal when the mold material melts. The wax removal route is exactly opposite to the filling route, which is like pouring melted wax out of the module, mainly to make the mold material as clean and fast as possible.

4. Heat matching may be a bit difficult for newcomers to the investment casting industry to understand. There is a question of solidification method involved here, let's discuss it in detail later. In fact, if you are interested, you can take a look at the tweet in front of the official account, which talks about the solidification method of castings. Here we will only briefly discuss the functions. This function refers to the fact that the design of the pouring system must ensure a reasonable temperature distribution during the solidification process of the casting, avoiding the occurrence of hot cracking, cold cracking, deformation, internal stress, etc.

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