Influence of Damage on Molds
Mold damages not only affects the wear ability and conductivity of equipment but also influences its maintenance. Over time, the mold becomes wear out, and the quality of the products from it is affected in terms of strength and accuracy. The lifespan of molds is limited due to thermal wear, pressure needle wear, and impact wear. Current molds usually last for a short period. Among these reasons, thermal wear has the largest impact on the damage of molds.
Thermal Wear
Mold surface temperature is an important factor affecting die casting process. It directly affects surface roughness, casting strength, surface hardness and product performance of the cast parts. Temperature of mold surface increases with the use times, and under the same process, if the surface temperature of the mold is too high, the service life of the mold will be greatly reduced. When the die temperature is above 150℃, the surface of the die will undergo oxidation, teaming and decomposition of carbide. This will seriously affect the mechanical properties of the mold, making it difficult to cast quality castings for the equipment. Improper temperature control will lead to defects in the casting structure, such as pores, coarse grains, cold separation of cutting edges, thin cores and full filling of the mold cavity. Therefore, effective control of the mold temperature is an important measures to reduce the damage of molds.
Pressure Needle Wear
The pressure needle is an essential part of the die casting machine. The function of the pressure needle is to fill the molten metal into the die cavity and control the filling speed and pressure. It is directly related to the filling quality and batch cycle of the casting. Generally, after metal liquid is filled into die cavity, pressure needle will experienced resistance due to pressing metal liquid, forming metal fracture. Under the action of gravity, pressure and structural stress, metal fracture will cause adverse friction between pressure needle and die cavity, resulting in damage such as wear and jam. Therefore, in order to reduce the damage caused by pressure needle, relatively high quality materials should be used to extend the life of the pressure needle.
Impact Wear
With the increasing number of times of injection, the metal adhesion of the molten metal at the end of the nose plate will become stronger, which will cause the gate to jam, and at the same time, a large number of metal droplets will attach to the end face of the nozzle plate, causing uneven temperature on the nozzle plate surface. Because of the greater difference between the temperature of the two sides, the internal stress of the nozzle plate is increased, and the impact force will be strengthened and will cause the cavity to wear or even crack. Therefore, the nozzle plate needs to be cleaned in time, and cleaning should be careful to avoid scratching the surface of the nozzle plate and causing further damage.
Methods to Prevent Mold Damage
1. To improve the die structure, try to reduce the temperature of hot and cold areas. This can help to reduce the thermal stress damage caused by different expansion coefficients of material.
2. Use appropriate materials and heat treatment to make die components have good wear resistance and reduce size change after heat treatment.
3. Improve die materials and coating technology. The advantages of a good coating can reduce the wear of the mold.
4. Strengthen maintenance and repair, carry out effective heat treatment for the molds, and do repairs on time.
5. Improve the filling mode and appropriate reduce the filling speed.
In conclusion, mold damage can be a great hindrance to productivity and quality of products, manufacturers must keep a close eye on the molds and improve their maintenance methods to prevent further damage. Basic steps like using the correct materials and heat treatment, improvements in coating technology, and keeping molds clean can go a long way in preventing mold damages.
