Factors affecting the size of die castings are broadly the following.
1, molding compression is caused by the size of the error.
Molding shrinkage is the main factor affecting the size of die castings. Because molding compression is a complex process, so the shrinkage rate has a wide range of choices. According to the external shape of the die casting and structural characteristics, respectively, select the size of each part of the appropriate molding shrinkage and determine the size of the molding, is to ensure that the die casting size accuracy of the key issues.
2, the manufacturing error of molding parts.
2.1, the molding parts of the insert, mold processing datum, and the impact of processing technology.
2.2, machining errors of molded parts.
2.3, assembly errors of molded parts.
2.4, the error caused by the slope of the molded parts of the mold.
3, the influence of fluctuations in molding shrinkage during die-casting.
3.1, the influence of die-casting molding process parameters, such as press injection ratio pressure and internal gate speed.
3.2, the effect of mold temperature.
3.3, the effect of the temperature of the die casting when the mold is removed.
Die castings in the shrinkage process, broadly divided into the following three stages.
a, liquid shrinkage, after die casting, still in the liquid metal liquid temperature reduction caused by shrinkage; b, solidification shrinkage, in the cooling and solidification process, the metal liquid from the liquid to solid crystallization stage shrinkage; c, solid shrinkage, metal completely solidified when the crystallization is completed stage and out of the mold body shrinkage.
In die casting, because the superheat temperature of the metal liquid is not high, so the volume shrinkage in the liquid shrinkage stage is not large; shrinkage in the solidification stage, although larger, but is completed in the mold forming parts, and therefore by the molding parts, especially the core of the resistance limit. When the die-casting die temperature decreases and can reach the temperature of the mold, die castings from the mold body, only after the free shrinkage state, that is, the solid-state shrinkage stage. This shrinkage process has continued until the die casting reaches room temperature before the basic end. Therefore, it can be said that the temperature of the mold of the final shrinkage of the die casting plays an important role in determining the amount.
4, the error caused by the phase time movement of the structural parts.
4.1, mold closing errors.
4.2, the movement error of the side-drawing core and the movable core.
4.3, the error caused by the precision of the die-casting machine and the instability of the process performance.
5, punching error.
5.1, molding parts by the impact of pressure injection deformation caused by the error.
5.2, forming parts surface by the metal liquid or impurity erosion generated by the error.
5.3, subject to pressure injection stamping, template, or forming parts to produce elastic deformation or plastic deformation and the formation of forming part of the size error.