Patent Application
20240102250
The present application claims priority under 35 U.S.C. § 119 to German Patent Application No. DE 10 2022 124 938.7, filed Sep. 28, 2022, the disclosure of which is incorporated by reference herein in its entirety.
A molding tool for producing three-dimensional products from a fiber-containing material and a method for regulating a temperature distribution in a molding tool for producing three-dimensional products are described.
Fiber-containing materials are increasingly used, for example, to produce packaging for food (e.g., trays, capsules, boxes, etc.) and consumer goods (e.g., electronic devices, etc.) as well as beverage containers. Everyday items, such as disposable cutlery and tableware, are also made from fiber-containing material. Fiber-containing materials contain natural fibers or artificial fibers. Recently, fiber-containing material is increasingly used that has or is made of natural fibers which can be obtained, for example, from renewable raw materials or wastepaper. The natural fibers are mixed in a so-called pulp with water and optionally further additives, such as starch. Additives can also have an effect on color, barrier properties, and mechanical properties. This pulp can have a proportion of natural fibers of, for example, 0.1 to 10 wt %. The proportion of natural fibers varies depending upon the method used for the production of packaging, etc., and the product properties of the product to be produced.
The production of fiber-containing products or three-dimensional products from a pulp generally takes place in several work steps. For this purpose, a fiber processing device has multiple stations or forming stations. In a forming station, for example, fibers can be suctioned in a cavity of an intake tool, thus forming a preform. For this purpose, the pulp is provided in a pulp supply, and the suction tool is at least partially immersed in the pulp with at least one suction cavity whose geometry essentially corresponds to the product to be manufactured. During the immersion, suction takes place via openings in the suction cavity, which are connected to a corresponding suction device, wherein fibers from the pulp accumulate on the surface of the suction cavity. The suctioned fibers or a preform can subsequently be brought into a pre-pressing tool via the suction tool, and the preform is pre-pressed. During this pre-pressing process, the fibers in the preform are compressed, and the water content of the preform is reduced. Alternatively, preforms can be provided by means of scooping, wherein a scoop tool is immersed in the pulp, and, during startup, fibers are deposited on mold parts of the scoop tool.
After this, preforms are pressed in a hot press to form finished products. In this process, preforms are inserted into a hot press tool which has, for example, a lower tool half and an upper tool half which are heated. In the hot press tool, the preforms are pressed in a cavity under heat input, with residual moisture being removed by the pressure and heat so that the moisture content of the preforms is reduced from about 60 wt % before hot pressing to, for example, 5-10 wt % after hot pressing. The steam produced during hot pressing is suctioned off during the hot pressing via openings in the cavities and channels in the hot press tool.
A hot press tool and a manufacturing method using the hot pressing process described above are known, for example, from DE 10 2019 127 562 A1.
With the above-described fiber forming devices, problems arise in particular in that, primarily in the case of products with relatively large mold depths (e.g., >50 mm), such as, for example, cups, bowls, etc., there are large temperature differences on the mold surfaces of the forming devices (cavity and associated mold part) of a molding tool for hot pressing (hot press tool). It should be noted here that—especially in the case of products with large mold depths—a so-called plate heater with which cavities and mold parts are heated only via a heatable tool plate is disadvantageous. One problem is that the required heat on the mold surfaces of the cavity and of a corresponding mold part, which is moved relative to the cavity in order to form a mold cavity and press the fiber-containing material accommodated therein, can be provided only via the tool bodies or tool plate(s) on which the cavities and mold parts are arranged. This means that the tool plate(s) must be heated very strongly, since the mold surfaces cool down strongly upon contact with moist, fiber-containing material and during pressing due to the water emerging from the fiber-containing material, because the water drains energy from the cavities and mold parts to evaporate. As a result, the tool plate for the cavity and the mold part is heated more strongly and thereby brought to temperatures which are significantly higher than required for pressing. In particular, a control for heating tool plates fails when the surface temperature of the mold surfaces is measured, because the surface temperature drops sharply cyclically due to the contact with moist material and water. It should also be noted here that the thermal energy stored in tool plates and also in the cavities and mold parts is delivered with a time delay.
Furthermore, the surface temperatures on the mold surfaces of cavities and mold parts can depend upon further, different factors, e.g., the number of forming devices per tool plate, the tool material or material pairing, the material used for the preforms, the moisture content thereof, the heat storage capacity of the forming devices, etc.
However, no possibility is known for providing a uniform temperature distribution on the mold surfaces of a molding tool—in particular, for three-dimensional products with large mold depths. Especially with hot press tools for products with large mold depths, forming devices (cavities and mold parts) are used, which can be replaceably connected to a tool plate. This makes it possible to use one tool plate for different forming devices and products. The heating is located within the tool plate and takes place via the contact surfaces between the forming devices and the tool plate. One disadvantage here is that the heating can also provide a different heat transfer in the case of different geometries of the forming devices, as a result of which the hot-pressing process requires an additional adjustment.
In addition, in the case of large mold depths for products having large heights—generally greater than 50 mm—there is a different local power requirement—in particular, also with regard to the position of the forming devices on a tool plate. Furthermore, jamming or the like can occur due to different thermal expansion (tool plate, forming devices).
In contrast, the object is to provide a uniform temperature distribution on the mold surfaces of forming devices of a molding tool—in particular, for products with large mold depths. Furthermore, the object is to provide an alternative to the prior art and to ensure improved production for a large number of different product geometries.
The aforementioned object is achieved by a molding tool for producing three-dimensional products from a fiber-containing material, having at least one first tool component and at least one second tool component, wherein the first tool component and the second tool component each have a tool body, wherein the tool body of the first tool component has at least one cavity, and the tool body of the second tool component has at least one mold part corresponding to the at least one cavity, wherein the at least one mold part and the at least one cavity can be moved relative to one another to form a mold space between corresponding surfaces of the at least one cavity and the at least one mold part and can be pressed in order to press a fiber-containing material that can be introduced into the mold space, and wherein the first tool component and/or the second tool component have at least one heating device, wherein the at least one heating device is arranged such that, as a result of the arrangement of the at least one heating device, at least one first heating circuit is formed in the tool body, and at least one second heating circuit is formed in the associated at least one cavity or at least one mold part.
Due to the arrangement of the at least one heating device and the formation of a first heating circuit and a second heating circuit, the temperatures in the tool body and an associated cavity or mold part can be controlled individually in order to achieve an optimal temperature for the production process without the tool components being heated too much or too little, in order to achieve an average temperature that represents a compromise. Here, different temperatures can be achieved, for example, in a tool body and the associated at least one forming device (cavity or mold part), wherein basic heating, e.g., in the range of 200 to 300° C., can take place via the tool plate. A tool plate can be heated to about 250° C., for example. The at least one forming device (cavity or mold part) can be heated, for example, in the range of 170 to 250° C. When the tool plate is heated to 250° C., the forming devices can be heated to 220° C., for example.
It is thus advantageously achieved that the temperature of the tool body is kept substantially constant during operation, as a result of which the expansion of the tool body does not change or changes only insignificantly during operation due to the thermal energy introduced, so that no jamming or the like occurs. Basic heating of the tool body can also be maintained in a standby mode, for example. In contrast, the forming devices themselves can be brought to a lower or higher temperature that is sufficiently high for the hot-pressing process. The temperature of the basic heating is adapted in this case to the required hot-pressing temperature on the mold surfaces, so that the heat delivered with a time delay from the tool body does not increase the surface temperature, or the surface temperature on the surfaces of the mold surfaces does not exceed the required hot-pressing temperature (e.g., 220° C.).
In further embodiments, the temperature of forming devices can be higher, such as a basic heating in a tool body, wherein there is generally no delivery of heat with a time delay from the forming devices into a tool body, since thermal energy is cyclically withdrawn from the forming devices by the evaporation of water stored in the fiber-containing material. The prevailing temperature difference can substantially compensate for the loss of thermal energy during the evaporation of water.
In further embodiments, the at least one heating device can have at least one heating element arranged asymmetrically in the tool body and in the associated at least one cavity or mold part. An asymmetrical arrangement is given, for example, when, e.g., a heating element designed as a heating cartridge lies largely in the tool body, wherein a small portion protrudes into the forming device. For this purpose, the forming devices (cavities, mold parts) have receptacles for the corresponding smaller portion of such a heating cartridge. The receptacles must always be adapted to the arrangement and design of the corresponding heating device.
In further embodiments, a symmetrical arrangement of the at least one heating device can be provided, wherein an individual temperature distribution can take place in this case in accordance with the design and arrangement within a tool body and the forming devices. An individual temperature distribution can be achieved in this case, for example, by the distance of a heating element from a surface or form surface. At larger distances between a heating element and a mold surface, for example, a delivery of heat with a time delay in a forming device can cause the surface temperature to be lower, as in an embodiment with a smaller distance. The temperature distribution in a tool body is also different from the temperature distribution in the forming devices, so that, in these embodiments, an individual temperature adjustment in the components of the molding tool can also be achieved by means of a symmetrical arrangement.
In further embodiments, an effective heating surface of the at least one heating element can have a larger surface area extension within the tool body relative to a surface area extension within the associated at least one cavity or mold part, so that a greater heat transfer takes place in the tool body, or an effective heating surface of the at least one heating element can have a larger surface area extension within at least one cavity or mold part relative to a surface area extension within the tool body, so that more heat is transferred into the forming devices which are cyclically cooled by the evaporation of water.
To form at least one first heating circuit in the tool body and at least one second heating circuit in the forming devices, in further embodiments, a heating element can have at least two heating zones which can provide different heating and are accordingly arranged such that a first heating zone is arranged in the tool body, and a second heating zone is arranged in an associated forming device.
In further embodiments, the at least one heating device can have at least one first heating element and at least one second heating element, wherein the at least one first heating element is arranged in the tool body, and the at least one second heating element is arranged in the associated at least one cavity or mold part. The first heating element and the second heating element can be separate heating elements which can be controlled independently of one another and can provide heating that differs from one another in order to produce different temperatures in a tool body and at least one associated forming device. The at least one first heating element is part of the first heating circuit, and the at least one second heating element is part of the second heating circuit.
In further embodiments, a molding tool can have several cavities and associated mold parts, wherein heating elements of the at least one heating device are arranged differently with respect to position and/or orientation relative to one another and/or to the associated cavities or mold parts. The position and orientation can relate, for example, to the orientation and distance to surfaces of the tool body and of the mold surfaces.
In further embodiments, at least one heating element of at least one heating device for a cavity or mold part can be arranged and/or controllable differently than at least one heating element of at least one heating device for a further cavity or mold part of a first tool component and/or a second tool component. Thus, not only a different heating of tool bodies and associated forming devices can be achieved, but individual forming devices can also be heated differently than other forming devices of an associated tool body. Furthermore, zones of a tool body can also be heated differently.
In further embodiments, the at least one first heating element and the at least one second heating element can have a different heating output from one another due to their configuration. For example, heating elements can have heating surfaces of different sizes and also different heating powers.
In further embodiments, a molding tool can additionally have at least one cooling device, wherein the temperature of the molding tool, and in particular of the at least one tool body, can be regulated during operation between a standby temperature and a maximum production temperature of a production temperature range via the at least one heating device and the at least one cooling device, wherein the standby temperature is less than a minimum production temperature. This allows simulation of cooling in a heating press mode, as is normally produced by contact with moist fiber material and during evaporation, so that, for example, heating in the forming devices can be maintained when no preforms are introduced, and the hot-pressing process is paused. This ensures that the heating control does not have to be adjusted or changed, for example. For example, in case of relatively short breaks of a few minutes (up to 60 minutes), this is one way of keeping the molding tool in a hot-pressing mode without switching off the heating.
Furthermore, the molding tool can have at least one sensor element for detecting the temperature of the tool body and/or of the at least one forming device (cavity, mold part) in order to control the at least one heating device in accordance with the detected temperature. For example, at least one sensor element can be provided which detects the surface temperature of the mold surfaces of the at least one forming device.
In further embodiments, the arrangement/orientation of the at least one heating device and of heating elements and their control for heating the corresponding components (tool bodies and forming devices) can be determined in advance in a simulation. The forming tool is then formed on the basis of the determined optimal arrangement.
The above-mentioned object is also achieved by a method for regulating a temperature distribution in a molding tool for producing three-dimensional products from a fiber-containing material, wherein preforms are pressed into products under pressure and temperature in the molding tool, wherein the molding tool has at least one first tool component and at least one second tool component, wherein the first tool component and the second tool component each have a tool body, wherein the tool body of the first tool component has at least one cavity, and the tool body of the second tool component has at least one mold part corresponding to the at least one cavity, wherein the at least one mold part and the at least one cavity are moved relative to one another in order to form a mold space between corresponding surfaces of the at least one cavity and the at least one mold part and are pressed in order to form a fiber-containing material that can be introduced into the mold space, wherein the first tool component and/or the second tool component have at least one heating device, wherein at least one first heating circuit is formed in the tool body, and at least one second heating circuit is formed in the associated at least one cavity or at least one mold part by the at least one heating device, and wherein the temperature of the tool body of the first tool component and/or of the second tool component and the temperature of the associated at least one cavity or at least one mold part are individually regulated by the at least one heating device.
The division into a first heating circuit and a second heating circuit allows for individually controlling and regulating the temperature. Individual regulation or control means here that the temperatures can be predefined and set independently of one another. During hot pressing, the surface temperature of the mold surfaces drops due to the contact with moist fiber-containing material and the evaporation of water. For example, the surface temperature can drop by approximately 100 to 130° C.—for example, 120° C. Direct heating, which is independent of the tool body, by way of, for example, a separate heating element in the at least one forming device allows for rapid reheating to the actually required extent, wherein the forming device is not heated in excess of, for example, an optimal hot-pressing temperature determined in advance. Compared to known embodiments in which only one heater is provided via one tool body, the advantage of faster heating is achieved in that the heat does not have to be supplied with a time delay from the tool body first, but is provided directly via the first heating device in the forming device.
In further embodiments, the at least one heating device can have at least one first heating element and at least one second heating element, and the at least one first heating element can be arranged in the tool body, and the at least one second heating element can be arranged in the associated at least one cavity or mold part, wherein the temperature in the tool body and the temperature in the at least one associated cavity or the at least one associated mold part are individually regulated via the at least one first heating element and the at least one second heating element. The at least one first heating element and the at least one second heating element can, for example, be heated differently.
In further embodiments, heating of the tool body of the first tool component and/or of the second tool component and of the associated at least one cavity or the at least one mold part can be controlled individually with respect to the provided temperature and heating duration via the at least one first heating element and the at least one second heating element. Thus, for example, not only the heating temperature can be set and adjusted differently, but the heating duration can be adjusted as well. Here, it can be prevented, for example, that forming devices overheat when the hot-pressing process is temporarily interrupted or a standby mode is activated in which no hot pressing and thus no cooling of the mold surfaces take place.
In further embodiments, several cavities and/or mold parts of the second heating circuit that are assigned to a tool body can be heated differently in order also to take account of an individual heat demand and to achieve the optimal temperature on the mold surfaces. Particular in the case of multi-cavity tools, the forming devices are thermally influenced depending upon the position on the tool body and their design, so that, for example, a different heating is required for forming devices at the edge than for forming devices in a central position on the tool body.
In further embodiments, a temperature distribution in a molding tool for three-dimensional products, and in particular products made of a fiber-containing material, is controlled, wherein preforms are pressed into finished products under pressure in the molding tool, wherein the molding tool has at least two forming devices [cavity and mold part] and at least two heating devices, wherein the at least two heating devices can be controlled differently to achieve a definable temperature distribution on form surfaces of the at least two forming devices, and/or the distance of one heating device of the at least two heating devices from at least one assigned mold surface of a forming device is greater or smaller than the distance of a further heating device of the at least two heating devices from at least one associated mold surface of a further forming device.
In further embodiments, the control and thus heating of the at least one heating device or the heating elements can differ from one another, and/or the heating elements can be at an unequal distance from the mold surfaces assigned to them. In this way, in the case of identical heating devices which, for example, cannot be controlled or heated differently, a desired temperature distribution can be achieved by means of the distance between the heating devices and the mold surfaces.
Furthermore, in addition or alternatively, the heating devices can be controlled or heated differently so that a uniform temperature distribution is established on the mold surfaces of the forming devices. In this way, it can be achieved, in particular, that all mold surfaces of a molding tool lie within a definable temperature range. Forming devices can be designed, for example, as a positive and/or negative of the products to be produced, and can extend into a tool plate of the molding tool or project away from a tool plate. To form products, negatives and positives of the forming devices are brought to one another so as to form cavities therebetween. Similarly, the arrangement and orientation of heating elements can be deliberately selected such that there is a non-homogeneous heat distribution on the surfaces of mold surfaces, e.g., in order to take account of the material thickness and therefore the correspondingly lower or greater heat requirement in the case of products having sections of different thickness.
Further features, embodiments, and advantages result from the following illustration of exemplary embodiments with reference to the figures.
In the drawings:
Exemplary embodiments of the technical teaching described herein are shown below with reference to the figures. Identical reference signs are used in the detailed description for identical components, parts, and processes. Components, parts, and processes which are not essential to the technical teachings disclosed herein or which are obvious to a person skilled in the art are not explicitly reproduced. Features specified in the singular also comprise the plural unless explicitly stated otherwise. This applies in particular to specifications such as “a” or “one.”
Pulp refers to an aqueous solution containing fibers, wherein the fiber content of the aqueous solution can be in a range of 0.1 to 10 wt %. In addition, additives such as starch, chemical additives, wax, etc., can be present. The fibers can, for example, be natural fibers, such as cellulose fibers, or fibers from a fiber-containing original material (for example, wastepaper). A fiber treatment plant offers the possibility of preparing pulp in a large quantity and providing several fiber processing devices 1000.
The fiber-processing device 1000 can be used for producing, for example, biodegradable cups 3000 and other products that have large heights (>50 mm). Since a fibrous pulp with natural fibers is used as the starting material for the products, the products manufactured in this way can themselves be used as a starting material for the manufacture of such products after their use, or they can be composted, because they can usually be completely decomposed and do not contain any substances that are harmful to the environment.
The fiber processing device 1000 shown in
The control unit 310 is in bidirectional communication with an HMI panel 700 via a bus system or a data connection. The HMI (human-machine interface) panel 700 has a display which displays operating data and states of the fiber processing device 1000 for selectable components or the entire fiber processing device 1000. The display can be designed as a touch display so that adjustments can be made manually by an operator of the fiber processing device 1000. Additionally or alternatively, further input means, such as a keyboard, a joystick, a keypad, etc., for operator inputs, can be provided on the HMI panel 700. In this way, settings can be changed, and the operation of the fiber processing device 1000 can be influenced.
The fiber processing device 1000 has a robot 500. The robot 500 is designed as a so-called 6-axis robot and is thus able, within its radius of action, to pick up parts, to rotate them, and to move them in all spatial directions. Instead of the robot 500 shown in the figures, other handling devices can also be provided that are designed to pick up and twist or rotate products and move them in the various spatial directions. In addition, such a handling device may also be otherwise configured, in which case the arrangement of the corresponding stations of the fiber processing device 1000 may differ from the embodiment shown.
A suction tool 520 is arranged on the robot 500. In the exemplary embodiment shown, the suction tool 520 has cavities, formed as negatives of the three-dimensional molded parts to be formed, such as of cups 3000, as suction cavities. The suction cavities can have, for example, a net-like surface on which fibers from the pulp are deposited during the suction. Behind the net-like surfaces, the suction cavities are connected to a suction device via channels in the suction tool 520. The suction device can be realized, for example, by a suction device 320. Pulp can be suctioned in via the suction device when the suction tool 520 is located within the pulp tank 200 in such a way that the suction cavities are at least partially located in the aqueous fiber solution—the pulp. A vacuum, or a negative pressure, for suctioning fibers, when the suction tool 520 is located in the pulp tank 200 and the pulp, can be provided via the suction device 320. For this purpose, the fiber processing device 1000 has corresponding means at the supply units 300. The suction tool 520 has lines for providing the vacuum/negative pressure from the suction device 320 in the supply units 300 to the suction tool 520 and the openings in the suction cavities. In the lines, valves are arranged which can be controlled via the control unit 310 and thus regulate the suction of the fibers. It is also possible for the suction device 320 to perform a “blow-out” instead of a suction, for which purpose the suction device 320 is switched to another operating mode in accordance with its design.
In the production of molded parts made of a fiber material, the suction tool 520 is immersed in the pulp, and a negative pressure/vacuum is applied to the openings of the suction cavities, so that fibers are suctioned out of the pulp and are deposited for example on the network of the suction cavities of the suction tool 520.
Thereafter, the robot 500 lifts the suction tool 520 out of the pulp tank 200 and moves it together with the fibers adhering to the suction cavities, which still have a relatively high moisture content of, for example, over 80 wt % water, to the pre-pressing station 400 of the fiber-processing device 1000, wherein the negative pressure is maintained in the suction cavities for the transfer. The pre-pressing station 400 has a pre-pressing tool with pre-pressing molds. The pre-pressing molds can be formed, for example, as a positive of the molded parts to be manufactured and, for receiving the fibers adhering in the suction cavities, have a corresponding size with regard to the shape of the molded parts.
During the production of molded parts, the suction tool 520 is moved, with the fibers adhering in the suction cavities, to the pre-pressing station 400 in such a way that the fibers are pressed into the suction cavities. The fibers are pressed together in the cavities, so that a stronger connection is thereby produced between the fibers. In addition, the moisture content of the preforms formed from the suctioned-in fibers is reduced, so that the preforms formed after the pre-pressing only have a moisture content of, for example, 60 wt %. To squeeze out water, flexible pre-pressing molds can be used, which are inflated, for example, by means of compressed air (process air), thereby pressing the fibers against the wall of a cavity of a further suction tool part. As a result of the “inflation,” both water is squeezed out, and the thickness of the sucked-in fiber layer is reduced.
During pre-pressing, liquid or pulp can be extracted and returned via the suction tool 520 and/or via further openings in pre-pressing molds or pre-pressing tool parts (cavities). The liquid or pulp discharged during suction via the suction tool 520 and/or during pre-pressing in the pre-pressing station 400 can be returned to the pulp tank 200.
After pre-pressing in the pre-pressing station 400, the thus produced preforms on the suction tool 520 are moved by the robot 500 to a hot-pressing station 600, which has a molding tool 610 for the final shaping and drying of the preforms to form three-dimensional products. For this purpose, the negative pressure is maintained at the suction tool 520 so that the preforms remain in the suction cavities. The preforms are transferred via the suction tool 520 to a lower tool body 622 of a first tool component of the molding tool 610, which can be moved along the production line and out of the hot-pressing station 600. If the lower tool body 622 is in its extended position, the suction tool 520 is moved to the lower tool body 622 in such a way that the preforms can be placed on forming devices or mold parts 624 of the lower tool body 622. Subsequently, an overpressure is produced via the openings in the suction tool 520 so that the preforms are actively deposited by the cavities in the suction tool, or the suction is ended, so that the preforms remain on the forming devices or mold parts 624 of the lower tool body 622 due to gravity. By providing overpressure at the openings of the suction cavities of the suction tool, pre-pressed preforms, which rest/adhere in the cavities of the suction tool, can be released and dispensed.
Thereafter, the suction tool 520 is moved away via the robot 500, and the suction tool 520 is dipped into the pulp tank 200 in order to suction further fibers for the production of molded parts from fiber-containing material.
After the transfer of the preforms, the lower tool body 622 of the molding tool 610 moves into the hot-pressing station 600. In the hot-pressing station 600, the preforms are pressed into finished products under heat and high pressure, for which purpose an upper tool body 632 of a second tool component 630 of the molding tool 610 is brought onto the lower tool body 622 via a press. The upper tool body 632 has cavities 634 corresponding to the forming devices or mold parts 624. After the hot-pressing operation, the lower tool body 622 and the upper tool body 632 are moved away relatively from one another, and the upper tool body 632 is moved along the fiber-processing device 1000 in the manufacturing direction, wherein, after hot pressing, the manufactured products are suctioned in via the upper tool body 632 and thus remain within the cavities. The manufactured products are thus brought out of the hot-pressing station 600 and deposited according to the method via the upper tool body 632 on a transport belt of a conveyor device 800. After deposition, the suction via the upper tool body 632 is ended, and the products remain on the transport belt. The upper tool body 632 moves back into the hot-pressing station 600, and a further hot-pressing operation can be carried out.
The fiber processing device 1000 further has a conveying device 800 with a transport belt. The manufactured products made of fiber-containing material can be placed on the transport belt after the final molding and the hot pressing in the hot-pressing station 600, and discharged from the fiber-processing device 1000. In further embodiments, after placing the products on the transport belt of the conveying device 800, further processing can take place, such as filling and/or stacking the products. The stacking can take place, for example, via an additional robot or another device. In further embodiments, a fiber processing device 1000 can have a camera 810 or the like for a visual inspection of the products.
The fiber processing device 1000 from
The molding tool 610 has a first tool component 620 and a second tool component 630. The first tool component 620 has a tool body 622, and the second tool component 630 has a tool body 632. Forming devices are arranged on the surfaces facing each other, or are connected to the tool bodies 622, 632. In the embodiment shown in
The forming devices (mold parts 624, cavities 634) are replaceably connected to the tool bodies 622, 632, so that different products can be produced with the molding tool 610 of a hot-pressing station 600. For example, the forming devices can be connected to the tool bodies 622, 632 by means of screws.
For heating the molding tool 610, a first heating element 625 is arranged in tool body 622, and a first heating element 635 is arranged in tool body 632. The first heating elements 625 and 635 can be designed, for example, as heating cartridges. The tool bodies 622, 632 and the forming devices (mold parts 624, cavities 634) connected thereto are heated via the heating elements 625 and 635. For this purpose, the components of the molding tool 610 consist of a thermally-conductive material, such as aluminum. The components of the molding tool 610 can have channels and openings for suctioning in and off water or water vapor, which escapes during a pressing (hot pressing) of moist preforms.
The embodiment according to the prior art shown in
Also, in the embodiment of
In still other embodiments, heating elements can be arranged such that only a portion of their effective heating surface is received in forming devices, so that, in terms of area, a greater heat transfer takes place in the region of the tool bodies 622, 632 than in the forming devices.
A first heating zone A is provided in the tool body 622 via at least one first heating element 625. A second heating zone B is provided per mold part 624 via at least one second heating element 626.
The division into two different heating zones A and B enables individual heating of the forming devices, taking into account the energy actually required for evaporating water according to the position on the tool body 622, 632 and the geometry of the product to be manufactured. It is thus also possible to produce different products in a hot-pressing process, because heating can be set individually on the mold surfaces of the forming devices.
In the example of
The heating power required can be determined before a hot-pressing process—for example, with the aid of a calculation program in a simulation.
When determining the heating for a molding tool 610, the shape and configuration of a product to be manufactured is decisive, wherein products having relatively large mold depths (e.g., >50 mm) require direct heating of the forming devices. In the case of direct heating, heating elements, which may be part of heating devices, are arranged relative to the mold surfaces of the forming devices such that they are at a definable distance from the mold surfaces. In the case of direct heating, heating devices and heating elements may also extend around a forming device and/or run, for example, parallel to side walls of the forming devices. In addition, indirect heating is generally provided via the associated tool body.
In addition, the maximum number of forming devices per available area of a tool body 622, 632 with respect to the amount of heat that can be provided when as short as possible hot-pressing times are achieved is to be determined. Not only the maximum occupancy of a tool surface that is greatest in terms of area, but also the cooling effect due to the preforms introduced is decisive here. It should be noted here that excessive cooling requires longer hot pressing.
When determining heating, a (first) estimation of the required drying energy can be carried out on the basis of product geometry, wall thickness, and target material of the products to be manufactured.
Thereafter, the design of the heating can be carried out. This can be done, for example, for a first tool component 622 (lower tool) and a second tool component 632 (upper tool), alone or for both together.
Suitable heating devices and heating elements can be selected here. For example, electrically-controllable heating cartridges can be selected, wherein a selection of heating cartridges (uniform or different types) can additionally take place—for example, depending upon the available installation space for placing the same (by taking into account wiring, steam, and air channels).
In a further step, a first, rough distribution of the heating cartridges or other heating devices/heating elements can take place. For this purpose, the distribution of heating devices/heating elements and their alignment and orientation in the tool can take place, for example, according to a heating concept based upon the storage mass of the tool material (in particular, of the tool material for the forming devices). Furthermore, it can be achieved that there be the same distances from the product surface, i.e., from the mold surfaces, if possible.
In a further step, an FEM Model can be constructed according to the specifications and assumptions, and a calculation of the temperature distribution and a possible deformation of the tools (forming devices and/or tool bodies 622, 632) can take place in accordance with a calculation model. For example, a dynamic calculation model can be used for this purpose.
In a further step, the results of the calculation of the temperature distribution and/or deformation are analyzed, and an optimization of the selection and distribution of the heating devices/heating elements (e.g., heating cartridges) is carried out. For example, distances can be increased and/or reduced, the alignment and/or orientation of heating devices/heating elements can be changed, and/or the heating power can be modified in order to achieve definable temperature distributions on all/selected mold surfaces.
Subsequently, in a further step, a fresh FEM calculation of the tool (forming devices and/or tool bodies 622, 632) can be carried out until the temperature gradients are globally below a definable value. Such a value can, for example, be in a range of 30° C. to 100° C. In one exemplary embodiment, the threshold for the temperature gradient is 50° C.
In a further step, the heating devices/heating elements (e.g., heating cartridges) can be divided into power zones (individually for the first tool component 620 and the second tool component 630; heating zone A, B). For example, an additional division into zones can take place with respect to the extension over the surface of a tool body 622, 632 (inside—outside and/or in a manner specific to forming devices for large products).
In a further step, a change in the specific heating powers can be carried out in the FEM model, and then a calculation of the temperature distribution and a possible deformation of the tools (forming devices and/or tool bodies 622, 632) can take place.
Iteration can take place in a further step until a temperature gradient of less than 5 to 30° C., and preferably less than 10° C., has been reached. The design of the heater can be restarted if a temperature gradient of less than 10° C. cannot be reached.
After reaching the predetermined temperature gradient, the specific heating power can be read out in a further method step, and the selection of devices, materials, etc., and the arrangement and control can be documented and adopted as default values for the heating control in a hot press, a molding tool 610, and/or a fiber-processing device 1000.
If a temperature gradient of less than 10° C. has already been reached in the first calculation, the preceding determination of the parameters and selection can be terminated and adopted as a default. Furthermore, several iteration steps can be carried out until the predetermined temperature gradient has been reached.
In further embodiments, a new calculation for a heating device and/or heating element type can automatically take place if staying below the required temperature gradient cannot be achieved in a definable number of steps for a selected heating device and/or heating element type. Furthermore, in further embodiments, the above change can take place for a possible adaptation of the heating line and/or alignment/orientation and/or distance between mold surfaces and heating devices/heating elements.
In further embodiments, temperatures, pressures, and product properties of the product manufactured or yet to be manufactured, and of preforms introduced into a molding tool 610 and its original material (pulp) can be monitored during operation of a molding tool 610 by means of sensors and measuring directions, and the control of the heating devices can be (automatically) adjusted in case of a change.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 124 938.7 | Sep 2022 | DE | national |
