Definition

With filling: it means that the internal cooling rate of the injection blank is different from that of the outer cooling layer, which is inconsistent with the internal shrinkage rate after cooling. With filling is the phenomenon in which the green color is not a broken section, like the onion, the internal and external light color. The bigger the color difference is, the more serious the phenomenon is. Specific circumstances can refer to the following picture.

 

 

Reason

1, The difference between mold temperature and material temperature is too large during the filling process, which is caused by the rapid cooling of the external contact to the cold mold, while the internal remains soft and the internal and external shrinkage is different.

 

2, In mold filling, another part of material will be pressed into the blank, which is inconsistent with the temperature and shrinkage of the first entry material.

 

3. The with filling indicates that there is a great internal stress in the injection blank, and this part of the internal stress is one of the main reasons for the cracking of the solid during the subsequent solvent degrease process.

 

Improvement Measures

1) Increasing thermal conductivity. According to Fourier law of thermal conductivity dQ=-λdA•dt/dn, thermal conductivity can be improved by increasing the heat conductivity area A and the thermal conductivity λ.

 

To improve the heat conduction area of cemented carbide powder during mold filling and degrease, the powder loading rate must be improved, which need to increase the loading (reduce the proportion of dynamic components).

 

And the proportion of dynamic components in the melt will be increased by improving the thermal conductivity, which need to increase the dynamic proportion of flow.

 

2) Reducing the injection temperature and increasing the mold temperature. It can reduce the phenomenon of uneven temperature and improve uneven shrinkage.