Advanced mold cooling technology, in addition to recent hot-selling water transport technology, there are many other technologies that are unfamiliar to everyone, but has been put into production. The most representative ones are: pulse cooling technology, CO2 gas cooling technology and nano fluid cooling technology.
This article will focus on pulse cooling technology, CO2 gas cooling technology and conformal cooling technology analysis.

Pulse cooling technology

Pulse cooling technology was first developed by Brunel University in UK, and later Pennsylvania State University of United States conducted an in-depth study of this technology. In recent years, with advancement of technology, pulse cooling technology has been continuously developed and perfected. After long-term technical accumulation, CITO Company of United States has taken lead in designing complete sets of equipment for pulse cooling technology and successfully commercialized it.
Traditional cooling technology mainly controls temperature of mold by controlling temperature of coolant, while pulse cooling technology controls temperature of mold by changing flow rate. Heat generated during injection molding process changes with time, like a pulse signal, fluctuating. According to this feature, pulse cooling technology achieves purpose of adjusting mold temperature by controlling flow rate of coolant to corresponding pulse input. During pulse cooling process, flow rate of coolant is adjusted according to temperature of mold, as shown below. Compared with traditional cooling technology, temperature of pulse-cooled coolant is always low, which ensures a large temperature difference with mold temperature, enhances convective heat transfer between coolant and mold, and greatly improves cooling efficiency of mold. According to statistics, pulse cooling technology is 10%~30% more efficient than ordinary cooling technology, and can significantly improve quality of parts. Pulse cooling equipment is complicated. In order to make cooling uniform, partition cooling is required, and a thermocouple needs to be installed in each area to monitor temperature of mold at any time, which increases difficulty of its application.

CO2 gas cooling technology

C02 gas cooling technology was first developed by injection molding companies in United States. Low temperature CO2 was used as a medium to cool injection mold. Later, many injection molding companies in foreign countries developed C02 cooler.
C02 gas cooling technology uses a low temperature CO2 gas to cool mold. This technology must be used in a mold made of porous material. CO2 gas is introduced into a certain part of mold, shunt is guided, and then other parts of mold are cooled. Schematic diagram of its cooling principle is as follows:

Advantages of CO2 cooling technology:

First, structure of mold is effectively simplified. It does not require a special demolding mechanism. It only needs to open exhaust passage between plastic parts and mold contact wall, and CO2 gas can quickly blow out plastic parts.
In addition, CO2 cooling technology is more efficient than conventional cooling technology. According to structural characteristics of mold, it is divided into different zones, air inlet and exhaust port are respectively set, and then cooled separately. A thermocouple is installed on cavity surface of each area for temperature monitoring, and then controlled according to temperature result of galvanic feedback. Since C02 has a very low temperature (-78℃), temperature of cooling water of mold is generally 8℃, and temperature of most of cavity surface is 100℃ or more. Compared with water, CO2 has a larger surface area than cavity. Temperature difference and cooling efficiency are greatly improved.
Finally, compared with traditional liquid cooling medium, CO2 has good permeability and fluidity in porous metal mold, which can fully cool all parts of mold without leaving a cooling dead angle, avoid warping deformation of plastic parts due to uneven cooling.

Conformal cooling technology

Conformal cooling technology is a new high-efficiency mold cooling technology that has been developed with development of rapid prototyping technology. In 1997, Professor Sachs of Massachusetts Institute of Technology first proposed conformal cooling technology at SFF conference. In 1998, Jacobs in UK conducted a large number of experiments to systematically study effects of conformal cooling technology on quality, performance and production efficiency of products during injection molding. Later, Dalgarno and some scholars used new molding method to prepare conformal cooling water channel based on research results of predecessors.
Design idea of conformal cooling technology is to change cooling water channel with change of cavity structure, and cooling water channel always maintains a certain distance from surface of cavity. As shown below. Aboved Schematic diagram of two cooling technologies Compared with traditional cooling technology, advantages of conformal cooling technology are mainly reflected in following aspects:
(1) Cooling is more uniform. Traditional cooling channels are limited by processing technology and are generally designed to be straight. Due to irregular surface of cavity, distance between cooling water channel and cavity is different, which results in uneven cooling of mold, and produced product is prone to warpage or poor mechanical properties. However, conformal cooling water channel can be consistent with length of cavity, changes with structural change of cavity to uniformly and efficiently cool plastic parts, thereby greatly improving quality of plastic parts.
(2) High molding efficiency. Mold must be opened to make temperature of all parts of plastic parts below mold opening temperature. Conventional cooling technology makes cooling of plastic parts uneven, cooling time required for some parts is short, while cooling time of some parts is long. In this way, total cooling time is invisibly lengthened. Conformal cooling technology is evenly cooled, and simultaneous cooling can be achieved, which greatly improves molding efficiency.
Studies have shown that conformal cooling technology can increase molding efficiency of mold by more than 30%.