Pulse cooling technology of the hottest mold

Pulse cooling technology of mold

pulse cooling is a process method that can quickly heat the mold. The example of manufacturing the upper shell shows that in addition to heat dissipation, if other process methods on the injection molding machine can be optimized, a lot of time can be saved

market saturation, price decline and cost pressure are driving the rationalization reform of injection molding

adjust the forming cycle

the time of the forming cycle is a factor for adjustment. The potential can be seen by decomposing the molding cycle time into time intervals. Wieder Co., Ltd., located in Schweinfurt, Germany, first saw this additional potential in terms of cooling time, provided that it was able to successfully continue to allow the molten material to dissipate heat freely in the mold. According to annealing experts, this can save up to 50% of the cycle time. In the two-component injection molding of the upper shell of Siemens Leipzig factory, the time saved is even longer

of course, in addition, it is also necessary to reduce the working time of the machine. Therefore, wieder calculated the potential of saving time in an analysis commissioned by Siemens. Machine manufacturer ferromatik Milacron and robot device manufacturer Wittmann also participated in this project. Finally, the goal of producing 55000 upper casings per week proposed by Siemens was successfully achieved

wieder company reduced the heat dissipation time from 9.8s to 3.5s through pulse current cooling. However, this is achieved because parallel processes such as post pressing and plasticizing time are also shortened. In addition, the movement of the die, including the time to take out the workpiece, is also shortened. The final cycle time is 7.8s without changing the geometry of the injection molded part In order to approach the time of free heat dissipation, only the route of the cooling cycle circuit is changed in the mold. Here, only half of the existing cooling channel is used. They are selected in this way, that is, on the other hand, the heat reaches the nearest flow channel before the dry operation time (empty cycle); On the other hand, the heat transfer to the farthest runner must be completed within the cycle time. In order to do both, it is not always advantageous to put them behind the die groove as much as possible. In the production of pc/abs (polycarbonate/acrylonitrile, butadiene, styrene copolymer), the distance in the two mold groove mold of the upper shell is generally larger

new way of thinking

according to these changes, a way of thinking different from ordinary flow cooling is produced. According to wieder, in flow cooling, a constant flow of heat flow is the starting point. This is not the case during pulse cooling. It is based on the heat flow that decreases with time. The heat flow reaches the maximum in a short time after injection molding. It is measured by using a built-in sensor to measure the temperature of the mold groove 3 rather relying on its own continuous efforts. If it is impossible to install a sensor inside, a temperature sensitive element can be used to measure the temperature in the return flow of coolant. In both cases, the opening time of the cooling circuit valve should be calculated accordingly. These times correspond to the distribution of the percentage of heat that needs to be conducted

the correlation between thermal conductivity and temperature of pulse rapid cooling system is considered to be the reason why the heat flow decreases with time. According to wieder, in the case of polyamide 6.6, the heat flow will differ by 30%. This correlation can be used in pulse cooling. In pulse cooling, the flow of coolant is interrupted repeatedly, which occurs in a short periodic time interval to produce a serrated temperature curve. On the other hand, if there is no heat to conduct, stop the flow

in this way, the generation of condensed water can be avoided. Usually, the inlet temperature of the coolant will produce condensed water. The inlet temperature is 15 ° C when injecting the upper casing, which is significantly lower than that of ordinary flow measurement. Thus, a very high temperature drop for the mold groove wall is achieved, so as to realize faster heat dissipation from the mold. The temperature of the mold groove wall is maintained at a certain level by means of sensors

mold temperature control

and the temperature of the whole mold is controlled by a box type adjusting device. Its function is that although the inlet temperature is low, it can keep the temperature of the two half molds in balance. According to wieder, if the temperature difference between the two half molds rises, the rapid heat conduction of pulse cooling will be at the cost of significantly increased mold wear

therefore, temperature experts suggest that the first step should be to analyze the heat flow of the mold. Through the analysis, we can know whether the work and cost of pulse cooling are worth it. The thinner the part wall is, the greater the possibility that the common sheet metal damage of this change is in the process of transportation. Wieder has proved this not only in the upper shell, but also in the injection molding of bumpers and beverage cups

at the fakuma exhibition, the automation expert gosewehr demonstrated pulse cooling on the booth. The company exhibited a high-speed robot for taking out parts. It uses standard process methods for injection molding on the high-speed machine of DEMAG Ergotech, which can shorten the cycle time. The goal of this project is to shorten the cycle time to less than 7S, thereby reducing the investment recovery time to less than 6 months