KR20100052654A - Mold structure of rapid heating and cooling cycle system - Google Patents

Abstract

PURPOSE: A mold structure for rapid heating and cooling is provided to improve quality and productivity without generating weld lines and to minimize heat loss when heating. CONSTITUTION: A mold structure for rapid heating and cooling comprises a lower mold, an upper mold(102'), a rapid heating unit, a heating hole, heating passages(107), a cooling space(110), a rapid cooling unit, a cooling hole(108), and a cooling line(109). The upper mold seals a resin in a molding space by covering the top of the molding space. The rapid heating unit applies heat to the upper and lower molds and heats the molds. The heating hole penetrates through the bottom of the upper mold and the bottom surface of the molding space. The heating passages transfer heat by connecting the rapid heating unit and the heating hole. The cooling space is used as a heat insulating space. The cooling space is used in cooling the cooling water pathway. The rapid cooling unit supplies cooling water to the upper and lower molds. The cooling hole discharges the cooling water to the cooling space. The cooling line supplies the cooling water by connecting the rapid cooling unit and the cooling hole.

Description

MOLD STRUCTURE OF RAPID HEATING AND COOLING CYCLE SYSTEM}

The present invention relates to a rapid heating and rapid cooling device for dies, and more particularly, to prevent weld lines in a molded product when molding a plastic product, and to obtain a product with a high gloss surface at the same time. It is about the provision of.

When the molten resin of the injection molding machine is filled into the cavity which is the product shape of the mold, the molten resin forms two or more molten resin flow leading ends, and the two or more flow leading parts are completely combined while being filled or recombined with the filling raw material. The weld line is called a weld line because the fusion lines such as cuts are generated on the surface of the molded article because they do not fuse.

Plastic products are used to mold various types of products or other parts. In spite of the same product, weld lines such as sharp color differences or fine lines are formed in the molding process.

The cause of the weld line is a lack of flow of the resin injected into the mold, so that the joint becomes clear, and thus the appearance of the weld line is deteriorated, and the strength of the molded product is lowered.

In order to prevent the weld line from being generated or to make the weld line very weak, the mold of the high temperature and high pressure may be rapidly cooled while allowing the resin to easily flow from the high temperature and high pressure to the weld line.

On the other hand, such rapid heating and rapid cooling injection molding is also used for high gloss injection molding. High gloss injection molding is a molding method in which a mold is preheated to a predetermined temperature in plastic injection and then injected by injecting plastic resin raw material and cooling before removing the injection product from the mold. More specifically, by increasing the surface temperature of the mold, which is the shape of the product, above the thermal deformation temperature of the plastic raw material, the raw material is filled, and after the completion of the packing process, the temperature of the mold is rapidly lowered to cool the resin to form an appearance of the injected product. It is a new method that prevents weld lines from being formed and improves the degree of transfer to achieve high gloss.

As described above, methods for rapid heating and rapid cooling of the mold have been developed and used, and the representative ones of these methods are as follows.

First, the upper and lower molds constituting the mold are opened, and propane gas is ignited from the outside of the mold to heat the mold surface to rapidly increase the temperature of the mold. . In addition, the cooling of the mold is configured to cool rapidly by installing a cooling circuit on the outside of the mold, but due to the characteristics of injection molding requiring a short cycle, propane is combined with a separate controller for controlling the propane gas and the mold in conjunction. It has the disadvantage of requiring additional means for controlling the gas.

Second is a structure to perform the heating and cooling of the mold at the same time by using a cooling circuit used for cooling the mold. In this case, it is a system that circulates hot water or steam at high temperature and high pressure during rapid heating to heat the mold, and circulates cooling water to cool rapidly when cooling. In such a system, since hot water and cold water must be circulated together using a single line, a separate system for control is required, as well as many additional facilities for producing, supplying and circulating hot water or steam at high temperature and high pressure. As a result, the installation cost is excessive compared to the effect.

Accordingly, the present invention provides a device for rapid heating and rapid cooling of a mold for injection molding a plastic product at a simple yet low cost by inventing to solve the problems as described above to reduce the rapid heating and rapid cooling cycle of the mold injection The purpose of the present invention is to prevent weld lines from being formed and to contribute to the improvement of product productivity as well as the quality.

Furthermore, it has a predetermined cooling space under the mold which is utilized as an adiabatic space during heating and a cooling water passage during cooling, and minimizes heat loss during heating to use a conventional technique at a desired injection temperature. There is a characteristic that can be reached in a faster time than when heated.

On the other hand, when cooling, a large amount of coolant flows through a predetermined space, thereby lowering the temperature of the mold in a faster time than the mold cooling system having a large number of narrow tube-type coolant passages, which is an injection molding product. Can be taken out.

As described above, the present invention is characterized by having a cooling space which is an empty space in the lower part of the mold, and separately provided with a water supply passage used for heating and a cooling space used for cooling, the heating passage is for heating purposes only. The cooling space is used only for cooling purposes.

In the case where the heating and cooling passages are provided in the form of a plurality of narrow circular pipes of the related art passing through the inside of the mold, the heating and cooling flow is more than a certain speed because the flow rate of the fluid during heating and cooling was limited. Difficult to do In addition, when foreign matters are inserted into the narrow passage, the amount of flow per predetermined time is reduced, and thus heating and cooling operations are not easy.

In detail, when heating, the mold is generally made of a metal having good thermal conductivity, so if there is no separate insulation device when heating, heat loss occurs, and it takes a lot of time to raise the mold to the desired injection temperature. Additional cost as much as heat loss is needed.

In addition, the cooling can be produced in the injection molding product of the desired quality to perform the cooling operation within a short time, as described above, in the case of the tubular passage there is a limit to the flow rate of the coolant, it is difficult to shorten the overall finished product molding time. This likewise raises the problem of cost loss.

Therefore, in order to improve this problem, the present invention produces a cooling space that occupies a large space rather than a narrow circular pipe. The cooling space is empty when heated, and has an effect of minimizing heat loss from the mold to the outside during the heating process due to the air present therein. On the contrary, during cooling, the cooling water is injected to pass through the cooling space, so that the temperature can be lowered for a short time to take out the finished product. After the cooling process is over and the heating process is repeated, the coolant remaining in the cooling space injects air into the cooling space and draws the cooling water out of the cooling space. As a result, air is injected into the cooling space in preparation for heating again, and the cooling space serves as an adiabatic space.

The present invention provides a device for rapid heating and rapid cooling of a mold for injection molding a plastic product at a simple and low cost to reduce the rapid heating and rapid cooling cycle of the mold so that weld lines are not generated in the product to be molded. It is an invention having various effects such as not only improving productivity but also contributing to quality improvement.

In addition, since the cooling space of the shape that occupies a large space rather than a narrow circular pipe shape is manufactured, due to the air present in the interior, it exhibits the effect of minimizing the heat loss from the mold to the outside during the heating process. On the contrary, when cooling, the cooling water is injected to pass through the cooling space, thereby lowering the temperature in a short time, thereby allowing the finished product to be taken out.

Hereinafter, with reference to the drawings, the preferred configuration and operation of the present invention for achieving the above object will be described based on specific embodiments. Like reference numerals refer to like elements.

In the present invention, by providing a device 100 for rapid heating and rapid cooling of the mold for injection molding the plastic material product to shorten the molding cycle while preventing the creation of the weld line to contribute to the productivity and quality of the product It is characterized by.

Referring to Figure 1, which is a simplified schematic diagram showing a rapid heating and rapid cooling apparatus to which the technique of the present invention is applied, the rapid heating and rapid cooling apparatus 100 of the present invention for achieving the object of the present invention is intended to be injection molded The rapid heating means 104 and the rapid cooling means 105 are formed in the mold bodies 103 and 103 'constituting the upper and lower molds 102 and 102' forming the molding space 101 having the same shape as the product. It is provided integrally.

The upper and lower molds 102 and 102 'constituting the molding space 101 are symmetrical with respect to the interface where the upper and lower molds 102 and 102' contact. That is, in the case of the lower mold 102 ', the molding space 101 is in the upper portion, whereas in the case of the upper mold 102, the molding space 101 is in the lower portion. In addition, in the case of the cooling space 110 which will be described later, the lower mold 102 'is provided at the bottom, whereas in the case of the upper mold 102, the molding space 101 is present at the top. That is, the upper and lower molds 102 and 102 'having the same structure, the molding space 101 has a structure facing each other. Hereinafter, even when one mold is described as an example, the structure described is a common (symmetrical) structure of the upper and lower molds.

The rapid heating means 104 forms a plurality of heating holes 106 in the longitudinal direction of the mold body 103 to pass through the bottom surface of the molding space 101 on one side of the mold body 103, the heating hole In the 106, a heating passage 107, such as a heating pipe that receives heat from a heating device such as a cartridge heater that generates high heat upon receiving power and is transferred to a mold, is incorporated.

The rapid cooling means 105 forms a plurality of cooling holes 108 in the lower portion of the heating hole 106 formed in the mold body 103, the cooling hole 108 has a circulation pump and supply and drain lines Branch is connected to the cooling line 109 is configured to circulate the cooling water. The heating hole 106 formed in the mold body 103 is preferably in a position as close as possible to the molding space 101 to help rapid cooling of the moldings injected into the molding space 101.

The rapid heating means 104 is mainly used an electric heater that directly heats the mold with electricity such as a cartridge heater, but may also use a method of supplying heat through a fluid such as water. That is, instead of a heating passage 107 such as a heating pipe in which a heating wire is wound, using a pipe through which water or steam passes, the rapid heating means 104 is used as a boiler or a hot water supply device to supply hot steam or hot water. The mold can be heated.

When the mold is heated by supplying the hot water, the heating hole 106 and the heating passage 107 in the upper portion of the cooling space 110 are unnecessary, and the mold is heated by supplying hot water to the cooling space 110 to be described below. This can make the mold structure simpler. That is, the cooling hole performs two functions of supplying and discharging hot water when heated and supplying and discharging cooling water during cooling. Likewise, the cooling line connects both the rapid cooling means and the rapid heating means and the cooling hole to supply hot water during heating and cooling water for cooling.

In particular, the use of hot water is less efficient and less efficient than using steam. In general, since the injection temperature of the mold is higher than the boiling point of water under 1 atm, the process of phase change to steam causes heating by the corresponding latent heat to increase fuel costs, and the efficiency of steam is difficult to recycle.

In order not to undergo the process of phase change to steam, the water is heated under high pressure to prevent water from undergoing phase change by using the phase change characteristic of increasing the phase change temperature (evaporation temperature) when water is heated under high pressure. Preheating the mold by closed circulation of hot water above ℃ reduces the fuel cost as much as the latent heat of evaporation, and it is enough to heat up the hot water after it has been circulated to heat it by a smaller temperature difference between the water temperature and the target temperature. It is effective.

In addition, due to the occurrence of pressure drop, which is another problem of the conventional steam system, since the temperature is also lowered, the production and consumption of steam is increased and time is consumed in order to adjust the mold to a desired temperature.

In order to solve this problem, when using high temperature water, the pressure change is small and the temperature is mostly transmitted as it is, thereby allowing the mold to reach the desired temperature in a short time. As a result, it is possible to solve the shortcomings of the conventional steam heating method using high pressure and high temperature water.

In order to generate hot water, a large pressure is required. In the phase equilibrium of water, for example, the saturated steam pressure corresponding to, for example, 160 ° C. is about 6.18 bar, so a pressure of at least 6.18 bar or more must be maintained at 160 ° C. You can get it. Therefore, when adopting a method of heating the mold with water, a pressing means (not shown) is required separately.

Next, referring to FIG. 2, FIG. 2 is an enlarged perspective view of the lower mold 102 ′ of FIG. 1 and illustrates a cooling space 110 in the mold connected to the cooling line 109 in a dotted line. The upper mold 102 also has the same symmetry.

The cooling space 110 is an empty space provided in the inside of the mold, and may include a support member (see FIG. 3) in the form of a partition wall or a column according to a selection. As described above, when the heating space is filled with air, the cooling space 110 serves as a heat insulating space to prevent heat from being taken out. In particular, the heating passage 107 is to pass through the mold close to the molding space 101 so that heat is transferred to the molding space 101 as much as possible, the air in the cooling space 110 heats toward the opposite side of the molding space 101 This prevents the loss from occurring.

On the other hand, in the case of cooling, water (cooling water) having a large heat capacity is injected into one side of the cooling line 109 into the cooling space 110 in a preferable direction, and the cooling water which has circulated in the opposite direction to the cooling line 109 is cooled. Will be discharged. The amount of movement of the cooling water per unit time is larger than that of the conventional thin pipe type tube, and thus, the temperature drop per unit time is greatly increased, thereby reducing the overall process. Since the inlet and outlet of the cooling water are irrespective of the direction, the cooling water is injected from the opposite direction to allow the cooling circulation.

The cooling space 110 is provided at the lower portion (the upper portion of the upper mold 102) of the mold 102 ', and is an empty space having a rectangular shape as described above. If the coolant simply flows out, the heat transfer may not be performed smoothly, and thus may not be sufficiently cooled. Accordingly, a cylinder for forming a vortex may be further provided in the middle of the cooling space 110 according to a selection. In the case of a cylinder or a general square column, an additional cooling effect can be obtained because vortices are formed around the column and water is delayed at regular intervals.

3 is a side cross-sectional view of the mold 102 shown in FIG. The direction in which the heating passage 107 extends and the direction in which the cooling line 109 extends may be the same or may extend perpendicularly. In FIG. 3, the heating passage 107 and the cooling line 109 are illustrated to be perpendicular to each other for convenience of description.

The cooling space 110 is in the form of an empty space located at the lower portion of the mold 102 '(upper portion of the upper mold 102). Since the mold is subjected to a large pressure during the injection molding, there is a risk that the mold 102 is recessed or damaged into the cooling space 110, which is an empty space in the mold 102. Therefore, it is possible to install the support member 111 in the form of a partition or column in the middle in accordance with the selection to withstand the pressurized force. In particular, in the case of the support member 111 of the pillar shape of the support member can achieve an additional cooling effect due to the vortex formation as mentioned above.

When ejecting the product after the mold is preheated (quickly heated) after filling the resin and then completing the injection and rapidly cooling the mold, the ejector pin 112 is generally provided so that the product easily comes off the mold. do. The ejector pin 112 extends up and down from the bottom surface opposite to the molding space 101 of the mold to the molding space 101. Pressing the head of the ejector pin 112 toward the molding space 101 to push out the product is easy to take out. Unlike a mold 102 according to an exemplary embodiment of the present invention, since a general mold does not have an empty space such as the cooling space 110, the ejector pin is formed by forming a plurality of thin tubes in the mold in the vertical direction. In the direction to release the product from the mold.

On the other hand, the mold 102 according to the embodiment of the present invention includes a cooling space 110 that is an empty space at the bottom of the mold, and the cooling space 110 is filled with the cooling water during cooling, so that the ejector pin 112 If there is no pipe or passage to protect the water directly, there is a risk of damage, such as corrosion and erosion depending on the material, there is a risk that the ejector pin 112 bent or missing if the flow rate of the cooling water is faster. Accordingly, the ejector pin 112 repeatedly inserted into the support member 111 may be used to protect the ejector pin 112. Optionally, instead of the support member 111, a sleeve tube thinner than the support member may be separately provided so that the ejector pin 112 may penetrate the cooling space 110 without problems.

When using the support member 111 or the sleeve tube, the O-ring 116 is provided so that water does not seep through the gap, so that the O-ring 116 has an upper connection 114 and a lower connection of the cooling space 110. It is wrapped around (115). O-ring 116 is made of a material that can be elastic and waterproof, mainly rubber material is used.

The cooling space inlet and the cooling space outlet which are the inlet and outlet of the coolant are irrespective of the direction, and the cooling hole 108 corresponds to this, and the positions of the inlet and outlet may be changed. In the cooling process, the cooling water is injected into the cooling space inlet, and the cooling water rapidly cools the mold 102, and the temperature rises to exit the cooling space outlet. After the cooling process is finished, the finished product is taken out, and the cycle of heating again is repeated. Since there may be cooling water remaining in the cooling space 110 before the heating process starts, air is injected into the cooling space inlet to push the cooling water to the cooling space outlet. To this end, an air injection device (not shown) is separately required.

After the cooling water is completely removed from the cooling space 110, the cooling space inlet 117 and the cooling space outlet 118 are sealed and the cooling space 110 is maintained in the air-filled state. To be able to play a role.

4 is a graph showing the relationship of time versus temperature during the rapid heating and rapid cooling cycles. The size of the mold also varies according to the size of the finished product, and if the size of the mold is changed, there is a difference in time required for heating and cooling. The horizontal axis is the time (seconds) axis, and the vertical axis is the temperature (absolute temperature K units) axis.

It can be seen that the temperature rises rapidly from about 0 seconds to 10 seconds to rise from 340K to about 460K. By having a cooling space 110 that acts as an adiabatic space, the temperature rises steeply during heating. In the 10 second to 12 second time interval, the temperature is kept substantially constant, in which the resin is injected into the mold. As described above, in order to prevent the formation of the weld line caused by the insufficient flow of the resin injected into the mold, the mold is rapidly cooled by allowing the resin to flow easily from the high temperature and high pressure state to the weld line. Is given. 12 seconds to 25 seconds is a cooling process, in which the temperature is drastically lowered to allow the resin to harden in a mold having a predetermined shape.

In this cooling process, the cooling water flows to the bulky cooling space 110, thereby lowering the temperature in a shorter time. In general, since it takes a short time to take out the product, more products can be manufactured, thereby improving productivity.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments, and may be manufactured in various forms, and the general knowledge in the art to which the present invention pertains. Those skilled in the art will understand that the present invention may be implemented in other specific forms without changing the technical spirit or essential features of the present invention. The embodiments described above are exemplary in all respects and are not limited to the limited forms. .

1 is a simplified configuration diagram showing a rapid mold heating and rapid cooling apparatus to which the technique of the present invention is applied.

FIG. 2 is an enlarged perspective view of the lower mold 102 of FIG. 1 showing a dotted line of the cooling space 110 in the mold connected to the cooling line 109.

3 is a side cross-sectional view of the mold 102 shown in FIG.

4 is a graph showing the relationship of time versus temperature during the rapid heating and rapid cooling cycles.

Claims (6)

A lower mold having a molding space shaped like a product for injection molding; An upper mold which is paired with a lower mold and has the same size and closes an upper portion of the molding space to seal the resin in the molding space; Rapid heating means for preheating the mold by applying heat to the upper and lower molds; A heating hole provided to pass through a bottom surface of a molding space provided in the lower mold and a lower portion of the upper mold; A heating passage connecting the rapid heating means and the heating hole to transfer heat; An empty space provided inside each mold, the cooling space being positioned at an upper portion of the upper mold and a lower portion of the lower mold, and acting as a heat insulation space as an empty space when heating, and used as a cooling water passage during cooling; Rapid cooling means for supplying cooling water to the upper and lower molds; A cooling hole positioned at an upper portion of the upper mold and a lower portion of the lower mold and supplying and discharging cooling water to the cooling space; Rapid cooling and rapid cooling mold apparatus comprising a; cooling line for supplying cooling water by connecting the rapid cooling means and the cooling hole. The method of claim 1, An ejector pin penetrating the cooling space and extending from the bottom of the cooling space to the bottom of the molding space, and pushing the product out of the molding space when the force is applied from the bottom to the molding space; A sleeve tube in the form of a hollow tube surrounding the ejector pin; Rapid heating and rapid cooling mold apparatus further comprises an O-ring to prevent the cooling water from entering both ends of the sleeve tube in contact with the cooling space. According to claim 2, Rapid heating and rapid cooling mold apparatus further comprises a support member in the form of a partition or column in the cooling space. According to claim 3, The support member is provided with a part of the structure inside the hollow tube to receive the ejector pin therein, and further comprises an O-ring to prevent the cooling water from entering both ends in contact with the cooling space Rapid heating and rapid cooling mold apparatus, characterized in that. 5. The rapid heating and rapid cooling mold apparatus according to claim 4, wherein the rapid heating means is a cartridge heater or a hot water supply device. A lower mold having a molding space shaped like a product for injection molding; An upper mold which is paired with a lower mold and has the same size and closes an upper portion of the molding space to seal the resin in the molding space; A hot water supply device for preheating the mold by supplying hot water to the upper and lower molds; An empty space provided inside each mold, which is located above the upper mold and below the lower mold, is used as a hot water passage when heated, used as a cooling water passage when cooled, and includes a support member in the form of a partition or column. Cooling space; Rapid cooling means for supplying cooling water to the upper and lower molds; A cooling hole positioned at an upper portion of the upper mold and a lower portion of the lower mold, and supplying and discharging cooling water to the cooling space and at the time of heating, cooling the hot water; A cooling line connecting the rapid cooling means, the rapid heating means and the cooling hole, and supplying cooling water when heating the hot water; An ejector pin penetrating the cooling space and extending from the bottom of the cooling space to the bottom of the molding space, and pushing the product out of the molding space in contact with the product when a force is applied from the bottom to the molding space; A sleeve tube in the form of a hollow tube surrounding the ejector pin; Rapid heating and rapid cooling mold apparatus comprising a; O-ring to prevent the cooling water from entering both ends of the sleeve tube in contact with the cooling space.

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