Electron Beam Fabrication of Injection Mold Tooling With Conformal Cooling

Electron Beam Fabrication of Injection Mold Tooling With Conformal Cooling
Channels by Ada V. Villalon.

Fast mold cooling is necessary in order to achieve high production rates, as cooling time represents a significant portion of the total cycle time - sometimes up to 80%. However, an inappropriate cooling rate can result in deformations if the part is ejected when it is still soft. Poorly designed cooling channels can also result in uneven cooling that produces warpage or other defects.

Some of the most important factors that affect the cooling of a mold are listed:

• Flow of coolant.

• Temperature increase of the coolant.

• Chemical composition of the coolant.

• Layout and sizing of cooling channels.

• Thermal conductivity of mold parts.

The heat contained in the molten plastic is transferred to the mold cavity, and it has to be removed so that the plastic can return to its solid form prior to ejection. The heat removal takes place mostly through the cooling medium. Some factors such as high flow pressures (in the order of 0.4-0.5 Mpa), large cross sections of channels and turbulent flow are highly desired in order to remove the heat from the mold efficiently.