1 Function and structure analysis of pouring system
System pouring refers to the channel in the sand mold to guide the molten metal into the mold cavity, which is generally composed of sprue cup, direct sprue, transverse sprue, internal sprue, etc. The sprue cup receives the liquid metal, flows into the transverse sprue through the direct sprue, and then into the mold cavity through the internal sprue. Therefore, the shape and section size of each intersection affect the casting quality. For this design, the basic form of intermediate injection is adopted, which is characterized by that the internal sprue is set at a certain height in the middle of the casting, generally it is convenient to open the mold on the parting surface, and it has both the advantages and disadvantages of top injection and bottom injection. It is widely used in production, and it is suitable for all kinds of small and medium-sized castings with uniform wall thickness and small height . It is suitable for the parts of the support table.
2 Sprue cup and sprue
The function of the sprue cup is to receive the liquid metal from the ladle, prevent the liquid metal from flying and overflowing, facilitate pouring, reduce the impact of the liquid flow on the cavity, separate the dregs and bubbles, prevent them from entering the cavity, increase the filling pressure head, etc. The structure shape of gate cup can be divided into funnel-shaped and pool shaped. The funnel-shaped structure is adopted in this design. A sprue cup is arranged on the upper profile.
The sprue is mostly a cone-shaped pipe with circular or square cross-section. Its function is to guide the liquid metal from the sprue cup down into the transverse sprue, the internal sprue or directly into the cavity, and provide enough pressure head, so that the liquid metal can overcome various resistance in the flow process under the action of gravity, and fill all parts of the cavity .
3 Transverse and internal sprues
The horizontal runner is used to connect the sprue and the inner runner and distribute the liquid metal to each runner smoothly and evenly. In addition to the distribution of liquid flow, it plays a role of slag retention. The cross section of the runner is mostly trapezoid, circular and dome trapezoid. Among them, trapezoid and dome trapezoid sections are mainly used for Casting Grey Cast Iron and non-ferrous metal castings. Trapezoid section is adopted for the cross sprue of the supporting platform parts.
The function of the internal sprue is to guide the molten metal into the mold cavity. The internal sprue is relatively short and can not retain the slag itself, but the reasonable structure size and the connection way with the transverse sprue will help to retain the slag. The internal sprue is 20 mm-30 mm for small parts, which is helpful to block slag in the cross sprue, and convenient for formwork making and cutting. The inner sprue is set up on the lower surface of the support platform parts, and the liquid metal is injected from the flange at both ends in two ways, which is conducive to the feeding in the flange cooling process. And the inner runner adopts trapezoid section.