Deep ribs (also known as deep ribs or deep reinforcing ribs) cool extremely quickly during the injection molding process. However, they are also most prone to absorbing heat from the mold, leading to subsequent issues like difficulty in filling, surface defects, and stress concentration. The core idea behind “rapid cooling” of deep ribs is “accelerating heat removal” and “optimizing filling conditions”, rather than letting them cool naturally. This involves optimizing the cooling channel design.
Mold Design and Material Level (The Most Fundamental and Effective Solution)
This is the primary and long-term effective solution for addressing the cooling challenges of deep ribs.
I. Optimizing Cooling Channel Design
Surrounding Cooling: Design cooling channels as close as possible around the mold core and cavity corresponding to the deep ribs, forming an efficient “heat exchanger.” The closer the cooling channels are to the ribs and the more reasonable the channel diameter, the higher the cooling efficiency.
Conformal Cooling: For very deep or complex ribs, traditional drilled cooling channels cannot get close enough. 3D printing (Metal Additive Manufacturing) or methods like drilling and then inserting splitted segments can be used to create conformal cooling channels that highly match the shape of the ribs. This is currently the most advanced and effective method, significantly improving cooling uniformity and efficiency.
Baffle Cooling or Bubbler Cooling: Insert cooling baffles or bubbler tubes inside the core corresponding to the deep rib, directly guiding coolant to the root of the rib for intense cooling.
II. Using High Thermal Conductivity Mold Materials
Mold Steel: Use Beryllium Copper alloy (BeCu) or high thermal conductivity steel (such as some proprietary hot-work tool steels) to make inserts in the area corresponding to the deep ribs. The thermal conductivity of these materials is 3-5 times that of ordinary P20 or H13 steel, enabling them to rapidly draw heat away from the ribs.
Heat Conduction Pins: Embed smaller beryllium copper or tungsten copper pins inside particularly slender cores (the steel that forms the ribs) to directly conduct heat from the tip to the cooling channels at the rear.
III. Venting System Optimization
Although venting does not directly cool, the end of deep ribs is extremely prone to trapped air. The compressed hot air can act like an “insulating layer,” preventing the melt from contacting the cold mold wall and potentially causing burns. Creating effective venting slots at the end of the ribs allows air to escape quickly, enabling the melt to fully contact the mold wall for heat exchange. This is a prerequisite for achieving effective cooling.