Resin sand equipment is the necessary equipment for foundry, and the quality of sand treatment directly affects the quality of castings. The following points should be paid attention to in customized resin sand production line:
1. The proper LOI value of reclaimed sand should be determined before the resin sand equipment is customized. Loi value, i.e. ignition loss, is an important index to measure the film removal rate of reclaimed sand, and is also closely related to the gas evolution of molding sand and the porosity defects of castings. Generally, furan resin sand is used for iron castings. Practice has proved that LOI value controlled at about 3% can meet the production requirements.
2. The final strength of resin sand should be determined when the equipment is customized. After the resin sand is mixed, it can reach a higher strength, that is, the final strength after 24 hours of self hardening. In the actual production process of foundry, the time interval from molding to pouring is not necessarily 24 hours, so the final strength of sand should be determined according to the production process. For enterprises whose mold curing time is less than 24 hours, the final strength standard shall be the strength achieved before casting. At the same time, two tendencies should be overcome in production: on the one hand, the strength is suppressed to ensure the cost, resulting in unstable quality and wide fluctuation range, which makes the casting quality greatly affected by raw materials and operators; on the other hand, blindly improving the strength to ensure the quality, increasing the casting cost and causing waste. The foundry should determine the appropriate final strength according to its own situation, and try to save resin and curing agent on the premise of ensuring casting quality.
3. When the molding process of resin bonded sand equipment is determined, special sand box shall be made as far as possible, with more air holes left on the box wall, solid samples shall be made for the model, template modeling shall be adopted, ceramic pipe shall be used for pouring system, and multiple and scattered internal gates shall be adopted, and more air outlets shall be set.