1. Definition of foam lost foam casting
Foam lost foam casting is also called solid casting. It is made of foamed plastics such as EPS, STMMA or EPMMA and other polymer materials to form a solid mold with exactly the same structure and size as the part to be cast. , Smooth, and air-permeable) and dried, buried in dry quartz sand and subjected to three-dimensional vibration modeling. The molten metal is poured into the casting sand box under negative pressure, so that the polymer material model is heated and gasified, and then Liquid metal replaces the one-time molding casting process formed after cooling and solidification to produce a new casting method.
Different names for foam lost foam casting: "dry sand solid casting" and "negative compaction casting"

2. Sanzhuji combines the lost foam casting process, it is recommended to pay attention to the following points in the foam lost foam casting process
2.1 The main process flow includes: pouring riser system design, pouring temperature control, pouring operation control, negative pressure control, etc.
The pouring system has a very important position in the lost foam casting process and is a key to the success or failure of casting production. Due to the wide variety of castings and their different shapes, the specific production process of each casting has its own characteristics and is extremely different. These factors directly affect the accuracy of the gating system design results.
2.2 The design of the gating system is different from traditional sand casting. In the design of the gating system, the particularity of this process should be considered. The cross-sectional dimensions of each part of the gating system are related to the size of the casting, the combination of model clusters and the number of pieces per box.
2.3 The combination of model clusters can basically reflect the characteristics of castings and the feeding form of castings. Due to the existence of model clusters, the behavior of molten metal is very different from sand casting. In the pouring process, the model gasification needs to absorb heat, so the pouring temperature of lost foam casting should be slightly higher than that of sand casting. For different alloy materials, compared with sand casting, the casting temperature of lost foam casting is generally controlled to be 30-50 ℃ higher than sand casting. The heat of the molten metal, which is 30 to 50°C higher, can meet the heat required for model gasification. Castings with too low pouring temperature are prone to defects such as insufficient pouring, cold insulation, and wrinkles. Castings with high pouring temperature are prone to defects such as sticky sand.
2.4 When designing the cross-sectional dimensions of each part of the pouring system, the resistance caused by the existence of the model during the pouring of the lost foam casting metal should be considered, and the minimum flow resistance area should be slightly larger than that of the sand casting
Negative pressure is a necessary measure for black alloy lost foam casting. The role of negative pressure is an important measure to increase the strength and rigidity of the sand mold, and it is also the main measure to eliminate the model gasification products. The size and holding time of the negative pressure are related to the casting material, the model cluster structure and the paint. For coatings with good air permeability and coating thickness less than 1mm, the negative pressure on iron castings is generally 0.04～0.06MPa, and the upper limit is taken for steel castings. For aluminum castings, the negative pressure is generally controlled at 0.02～0.03MPa. The holding time of the negative pressure depends on the structure of the model clusters. In the case of a large number of model clusters in each box, the holding time of the negative pressure can be appropriately extended. Generally, the negative pressure can be stopped when the solidified crust on the surface of the casting reaches a certain thickness. For thicker coatings and poor air permeability, the negative pressure and holding time can be appropriately increased.

3. In the process of manufacturing sand casting equipment, sanzhuji concluded that the taboo of foam lost foam casting is hoped to help the foundry.
The most taboo of lost foam casting pouring operation is intermittent pouring, which easily causes cold barrier defects in castings, that is, the temperature of the molten metal poured first decreases, resulting in a cold barrier between the molten metal poured later. In addition, the lost foam casting pouring system mostly uses a closed pouring system to maintain the pouring stability. In this regard, the form of the pouring cup is closely related to whether the pouring operation is stable. During pouring, the liquid level in the pouring cup should be kept stable to make the pouring dynamic pressure head stable.

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