The Advantages of vacuum casting process
Features of vacuum casting process
⑴ Mould sand is dry sand without binder.
⑵ Use a plastic film to shape the sand mold, and harden the mold by vacuuming the sand box.
Due to the above characteristics, the processes of modeling, falling sand, cleaning and the like are greatly simplified, and no sand mixing machine and binder supply equipment are needed, which simplifies the modeling and sand processing system.
Advantages of vacuum casting process
⑴The casting has high dimensional accuracy, clear outline and smooth surface.
● The surface of the inner cavity of the mold is covered with plastic film, and the surface of the mold is smooth and flawless.
● The internal and external pressure difference of the sand mold makes the hardness of each part of the sand mold uniform and high (more than 85).
● The sand box is easy to remove the mold, and the draft angle is small (0 ～ -1 °).
● The cavity is not easily deformed by the heat of the molten metal.
● During pouring, the vacuum of the flask is favorable for filling the cavity with metal liquid.
⑵High metal utilization
● Because the surface of the vacuum casting is smooth, the dimensional accuracy is high, and the machining allowance of the casting is small.
● Due to the slower cooling rate of the metal liquid in the cavity, which is conducive to the replenishment of the metal, the riser of the casting can be reduced and the utilization rate of the metal can be increased. The steel casting can be increased by 20%, and the cast iron can be increased by 25%.
⑶ Simple equipment and low investment
Due to the vacuum molding, in addition to the need to add a vacuum pump and a special sand box, other equipment is relatively simple, can eliminate the sand mixer and some auxiliary equipment, less investment costs, and convenient equipment maintenance.
(4)Saving raw materials and power
Due to the use of dry sand in vacuum casting, falling sand is easy, and the sand recovery rate can reach more than 95%. The power consumed by the V method is less, only 60% of the wet method, which can reduce labor by 35%.
(5) Pattern and flask long service life
Because the appearance is protected by a plastic film, the drafting force is very small, it is only slightly shaken and is not affected by high temperature and high pressure, so the appearance is not easy to deform and damage.
(6)Improve the working environment
● Most of the trace gases generated during the molding and pouring process are removed by the vacuum pump, and the air pollution is small.
● After falling sand, there is no large amount of waste sand treatment.
(7) Easy to manage and organize production
Vacuum casting has a short production cycle, simple process and easy operation, and does not require very skilled technical workers.
⑻Wider scope of application
● Vacuum casting is suitable for small batch production of single pieces by manual operation, as well as large-scale production of mechanized automation.
● Can be used for ferrous metals such as cast iron and cast steel, as well as non-ferrous metals such as copper, aluminum and magnesium.
Vacuum casting process technology
1 .Model
The pattern is fastened to the mold, that is, the model is assembled and installed on the negative pressure box. The pattern can be metal mold, wood mold, synthetic resin mold. In order to attract plastic film on the model, a lot of 0.8 is drilled on the model. 1.5mm small holes, most of the small holes in the convex and concave corners of the model. The model can be semi-permanent and the surface should be smooth. If a wood type is used, cracking and distortion will not occur when the surface temperature rises to about 60 ° C. Therefore, it is necessary to use dry hard wood that is not easily deformed.
2. Plastic film
The following conditions must be considered for plastic films suitable for the V method:
● Cheap.
● Has good strength and elongation.
● Uniform film thickness.
● The film emits less gas when burning, and does not cause pollution. Plastic film materials are: polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol
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