DE102023200536A1 - Process for specific injection molding of plastic components for household appliances, as well as injection molding machine - Google Patents

Abstract

The invention relates to methods for injection molding a plastic part 10 by means of an injection molding machine 1, comprising the following steps: a) equipping the injection molding machine 1 with an injection molding tool 2 that delimits a mold cavity 6, wherein the injection molding tool 2 has a first tool half 3 and a separate second tool half 5, wherein the injection molding tool 2 is closed by bringing the tool halves 3, 5 together and thereby delimiting the at least one mold cavity 6, b) providing plastic material 9 that has a first temperature within the processing window of the plastic material, c) heating the mold cavity 6 to a second temperature within the processing window of the plastic material and keeping the injection molding tool 2 in the closed state at the second temperature, d) injecting plastic material 9 that has the first temperature with an injection molding nozzle 4 of the injection molding machine 1 into the closed, heated injection molding tool 1 at an injection pressure of less than 90 kg/cm2 to fill the mold cavity 6, wherein during injection the plastic material 9 flows out of an elongated nozzle slot 21 of the injection molding nozzle 4 and the plastic material 9 is injected in the form of a flat ribbon-shaped melt strand through the nozzle slot 21 into the mold cavity 6 of the injection molding tool 2. The invention further relates to an injection molding machine 1 for carrying out the method.

Description

One aspect of the invention relates to a method for injection molding plastic components. Another aspect relates to an injection molding machine.

When injection molding thermoplastics, the plastic melt is transported from the plasticizing unit of the injection molding machine through the sprue system into the mold cavity or cavities. In classic injection molding tools, the sprue system is not thermally insulated from the rest of the tool. This means that both the tool and the sprue system inside it are tempered to temperatures well below the processing temperatures of the plastic.

This causes the thermoplastic material to solidify in the sprue system during the production of a component. This results in some disadvantages for this type of sprue system. The sprue usually has to be separated from the component. This can be done either by additional functional elements in the tool or manually or mechanically after demolding. After the sprue has been separated, a mark can remain on the component.

Some of the raw material does not flow into the product and must either be recycled or disposed of. In addition, the sprue increases the shot volume, meaning more plastic has to be plasticized than is ultimately present in the product. This can play a role both in terms of energy and in terms of the necessary machine performance.

In a hot runner system, the sprue system is thermally separated from the rest of the tool and heated separately so that the plastic melt in the sprue system remains permanently flowable. This means that the plastic in the sprue system does not solidify and no sprue remains on the component. Furthermore, longer flow paths can be achieved with the hot runner systems because the pressure loss in the sprue system is not increased by cooling the melt and the associated increase in viscosity.

The disadvantage is the higher investment costs, since the tool has to be specially designed to accommodate a hot runner system, the hot runner system itself incurs costs and the machines for controlling or regulating the system also have to be adapted.

In household appliance technology, relatively large tools are often required for injection molding, either because the components to be manufactured are relatively large or because several components are to be manufactured with one tool. This means that high pressures are required when injecting the plastic melt in hot runner systems in order to be able to bring the melt to the required places in the tool while it is still liquid. This in turn results in very high clamping forces in order to be able to hold the tool.

If smaller tools are used, the pressures are reduced but the cycle times for production are increased.

Furthermore, efforts are also being made to reduce the wall thickness of the components being manufactured. However, this often means that the injection pressures have to be increased in order to be able to get the melt to all parts of the mold cavity before it solidifies.

It is an object of the present invention to provide an injection molding method and an injection molding machine with which the production of plastic parts is improved.

This object is achieved by a method and an injection molding machine according to the independent claims.

1. a) Insbesondere Bestücken der Spritzgießmaschine mit einem Spritzgießwerkzeug, das zumindest eine Formkavität begrenzt, wobei das Spritzgießwerkzeug eine erste Werkzeughälfte, insbesondere eine erste Formplatte, und eine dazu separate zweite Werkzeughälfte, insbesondere eine weitere Formplatte, vorzugsweise eine Auswerferplatte, aufweist, wobei durch ein Aneinanderbringen der Werkzeughälften das Spitzgießwerkzeug geschlossen wird und dadurch die zumindest eine Formkavität begrenzt wird;
2. b) Bereitstellen von Kunststoffmaterial, insbesondere eine Kunststoffschmelze, das eine erste Temperatur innerhalb des Verarbeitungsfensters des Kunststoffmaterials aufweist,
3. c) Erwärmen der mindestens einen Formkavität auf eine zweite Temperatur innerhalb des Verarbeitungsfensters des Kunststoffmaterials und Halten des Spritzgießwerkzeugs im geschlossenen Zustand auf der zweiten Temperatur;
4. d) Einspritzen von Kunststoffmaterial, das die erste Temperatur aufweist, mit zumindest einer Spritzgießdüse der Spritzgießmaschine in das geschlossene erhitzte Spritzgießwerkzeug bei einem Einspritzdruck von weniger als 90 kg/cm2, um die zumindest eine Formkavität zu füllen, wobei beim Einspritzen das Kunststoffmaterial aus einem länglichen Düsenschlitz der Spritzgießdüse ausläuft und die Kunststoffschmelze in Form eines flachbandförmigen Schmelzstrangs durch den Düsenschlitz in die zumindest eine Formkavität des Spritzgusswerkzeugs eingespritzt wird.

One aspect of the invention relates to a method for injection molding at least one plastic part, in particular a household appliance plastic part, by means of an injection molding machine, preferably comprising the following steps:

1. a) In particular, equipping the injection molding machine with an injection molding tool which delimits at least one mold cavity, wherein the injection molding tool has a first tool half, in particular a first mold plate, and a separate second tool half, in particular a further mold plate, preferably an ejector plate, wherein by bringing the tool halves together the injection molding tool is closed and thereby the at least one mold cavity is delimited;
2. b) providing plastic material, in particular a plastic melt, which has a first temperature within the processing window of the plastic material,
3. c) heating the at least one mold cavity to a second temperature within the processing window of the plastic material and holding the injection mold in the closed state at the second temperature;
4. d) injecting plastic material having the first temperature with at least one Injection molding nozzle of the injection molding machine into the closed heated injection mold at an injection pressure of less than 90 kg/cm2 in order to fill the at least one mold cavity, wherein during injection the plastic material flows out of an elongated nozzle slot of the injection molding nozzle and the plastic melt is injected in the form of a flat ribbon-shaped melt strand through the nozzle slot into the at least one mold cavity of the injection mold.

This type of injection molding process enables an improved manufacturing process, particularly for plastic parts for household appliances. Unlike with hot runner systems, the mold halves are heated, which is not the case with hot runner systems, so the injected plastic melt can be kept flowing for longer in the mold cavity. This means that even very thin components can be manufactured better and the mold cavities can then be completely filled. In order to avoid distortion caused by high injection pressures when the mold halves are heated, the process uses a particularly advantageous geometry of the nozzle opening, namely the nozzle slot, of the injection molding nozzle.

The nozzle opening is the end of the injection molding nozzle from which the plastic material flows out in the direction of the mold cavity. This is because, unlike with nozzle openings of the injection molding nozzle that are round or circular in cross-section, a significantly lower injection pressure can be set and yet a highly flowable plastic melt can be introduced and this plastic melt can also be introduced into the mold cavity with the corresponding required, in particular larger, amount per time interval. This shape of the cavity-side nozzle opening can also achieve a more extensive and even distribution of the plastic material into the mold cavity. It is precisely this flat strip shape that enables these advantages. It has also surprisingly been shown that the interaction between the heating of the tool halves, especially in the area of the, preferably entire, mold cavity, and the specific, namely flat strip-like strand from the injection molding nozzle enables a very precise and complete production of even thin-walled components with lower injection pressures and relatively short cycle times.

In one embodiment, step c) is carried out as follows: heating the at least one mold cavity to the second temperature within the processing window of the plastic material and keeping the injection mold in the closed state at the second temperature by circulating a first tempering medium through one or more channels that are formed in at least one of the mold halves. This achieves rapid and precise heating on the one hand, and enables homogeneous and locally targeted heating of the mold halves on the other. In particular, the tempering medium is heated to a third temperature. The first tempering medium can preferably be liquid or gaseous. The first tempering medium can preferably be an oil.

In one embodiment, after step d), a step e) is carried out as follows: cooling the at least one mold cavity of the filled closed injection mold to a, in particular fourth, temperature below the first temperature until at least one molded plastic part in the interior of the injection mold is at least partially solidified.

In particular, the cooling in step e) is carried out by circulating a, in particular second, tempering medium, which has a, in particular fifth, temperature, through the at least one channel. The tempering medium can preferably be liquid or gaseous. This achieves cooling that is very tailored to requirements. This makes it possible to avoid uncontrolled, too fast or too slow cooling. In particular, the cooling is metered and homogeneous across the mold cavity.

In particular, a thermoplastic material is injected as the plastic material.

In one embodiment, the nozzle-side tool half and/or the tool half remote from the nozzle are made, in particular entirely, of aluminum or an aluminum alloy. This means that the tool halves are lighter in weight compared to steel or the like. This metal makes it very advantageous to temper the tool half, particularly quickly. This applies to both heating and cooling. However, these metals in particular can be subject to distortion due to high injection pressures, which is advantageously counteracted by reducing the injection pressures through the specific geometry of the injection molding nozzle, i.e. by creating the flat-band-like melt strand.

In one embodiment, in step d), the injection of plastic material at the first temperature is carried out at an injection pressure which is less than 78 kg/cm2, in particular less than 58 kg/cm2, in particular at an injection pressure between 17 and 52 kg/cm2. These injection pressures are particularly advantageous for the proposed concept of the tool halves made of the above-mentioned metal, the heating of the tool halves and the creation of the flat-band-like melt strand in order to produce thin-walled components quickly, precisely and completely. The short cycle times and very low component rejects as well as reduced post-processing of the produced components are also further advantages here.

In one embodiment, at least the first tempering medium is heated to at least one temperature within the processing window of the plastic material or higher. In particular, it is heated to a temperature greater than or equal to 150°C, in particular greater than or equal to 200°C, in particular greater than or equal to 300°C.

In one embodiment, the second temperature can be set equal to the first temperature. However, the second temperature can also be set higher than the first temperature. The fifth temperature can be set lower than the third temperature. It is also possible for the fifth temperature to be set lower than the lowest temperature of the processing window of the plastic material. It is also possible for the fourth temperature to be set lower than the lowest temperature of the processing window of the plastic material.

In one embodiment, the second temperature is set at least 18°C higher than the first temperature. In one embodiment, the fifth temperature is set at least 18°C lower than the fourth temperature.

In particular, a mineral oil is used as the second tempering medium. This is preferably tempered to a fifth temperature of at most 42°C. In particular, it is tempered to a temperature of less than or equal to 32°C.

In one embodiment, the housing of the injection molding nozzle is cooled in the area of the nozzle slot.

In one embodiment, heat is supplied to the plastic melt during solidification in the mold cavity by heating a nozzle core of the injection molding nozzle relative to a housing of the injection molding nozzle in the sprue area of the injection molding machine. This is done in such a way that when the injection molded plastic part is demolded, the sprue is torn off along the nozzle slot due to the temperature gradient between the solidified plastic part and the plastic melt in the sprue area. This also achieves a very targeted and clean separation.

• f) Öffnen des Spritzgießwerkzeugs durch Trennen der düsenseitigen Werkzeughälfte von der düsenfernen Werkzeugplatte, und
• g) Auswerfen des zumindest einen, wenigstens teilweise verfestigten gegossenen Kunststoffteils durch Betätigung von Auswerfer-Stiften der düsenfernen Werkzeughälfte.

In particular, after step d), in particular after step e), the following further steps are carried out:

• f) opening the injection mould by separating the nozzle-side mould half from the mould plate remote from the nozzle, and
• g) Ejecting the at least one, at least partially solidified molded plastic part by actuating ejector pins of the mold half remote from the nozzle.

In one embodiment, the first tempering medium and the second tempering medium are circulated through the same channel or one or more other channels, in particular selectively, in response to an opening or a closing of at least one valve of the injection molding machine.

• - während der Einspritzung bei einem Einspritzdruck von weniger als 90kg/m2 eines Kunststoffmaterials, das bei einer ersten Temperatur innerhalb des Verarbeitungsfensters des Kunststoffmaterials liegt, ein erstes Temperierungsmedium, das eine dritte Temperatur von mindestens einer Temperatur innerhalb des Verarbeitungsfensters des eingespritzten Kunststoffmaterials hat, in der zumindest einen Formkavität zu zirkulieren, um die zumindest eine Formkavität auf eine zweite Temperatur zu erhitzen, und
• - für eine mindestens teilweise Verfestigung des zumindest einen gegossenen Kunststoffteils im Inneren des Spritzgießwerkzeugs, ein zweites Temperierungsmedium zu zirkulieren, das eine fünfte Temperatur hat, die eingestellt ist, um die zumindest eine Formkavität des gefüllten geschlossenen Spritzgießwerkzeugs auf eine vierte Temperatur unterhalb der ersten Temperatur abzukühlen.

A further aspect of the invention relates to an injection molding machine with an injection molding tool that has a nozzle-side tool half and a tool plate remote from the nozzle, wherein the tool halves delimit at least one mold cavity in the closed state of an injection molding tool. At least one channel for a tempering medium to flow through is formed in at least one tool half. The at least one channel is designed in particular to

• - during the injection at an injection pressure of less than 90 kg/m2 of a plastic material which is at a first temperature within the processing window of the plastic material, a first tempering medium which has a third temperature of at least one temperature within the processing window of the injected plastic material is circulated in the at least one mold cavity in order to heat the at least one mold cavity to a second temperature, and
• - for at least partial solidification of the at least one molded plastic part inside the injection mold, to circulate a second tempering medium having a fifth temperature which is set to cool the at least one mold cavity of the filled closed injection mold to a fourth temperature below the first temperature.

The injection molding machine further comprises at least one injection molding nozzle for introducing a molten plastic material, in particular in particular a plastic melt, into at least one of the mold cavities. The injection molding nozzle has an elongated nozzle slot from which the plastic melt is injected in the form of a flat ribbon-shaped melt strand through the nozzle slot of the injection molding nozzle into at least one mold cavity of the injection molding tool.

The advantages that can be achieved in this way have already been explained in the process. In particular, the process and the injection molding machine also make it possible to reduce the clamping forces for holding the mold halves to around 30% to 40% compared to conventional injection molding methods (reference value is 100%), reduce the injection pressures to 30% to 40%, reduce cycle times to 60%, reduce energy consumption to 60%, and increase production capacity by over 100%.

In particular, a rear side of at least one of the mold halves is traversed by one or more open channels. In this example, the one or more open channels are only completely closed for the circulation of a temperature control medium when the mold halves are arranged in their final position in an injection molding machine.

Preferably, a cross-sectional area of the nozzle slot is between 40 mm ² and 60 mm ² , in particular between 45 mm ² and 55 mm ² . In particular, this cross-sectional area is rectangular. In particular, a value of a length to width ratio of this cross-sectional area is greater than or equal to 2.5, in particular greater than or equal to 3, in particular less than or equal to 5. The slot shape thus also makes it possible to achieve relatively large surface cross-sections of this nozzle opening. This means that more material can be applied per unit time.

In particular, at least one tool half is formed with a carbon-based material layer, at least in some areas on at least its inner side, which faces the other tool half. In particular, the material layer is a coating. This increases the rigidity, especially when the tool half is made of aluminum or an aluminum alloy. The carbon-based material layer can be made up of an amorphous carbon-hydrogen network. Graphite and diamond bonds can be formed between the carbon atoms. It is also possible for a hydrogen-free, carbon-based material layer to be formed, in which the number of diamond bonds is higher. This further increases the hardness of the material layer.

In particular, both tool halves have a rear side facing the other tool half and a front side facing away from the other tool half. In particular, the rear side of at least one tool half has at least one channel for the tempering medium integrated therein. A channel has an inlet and an outlet.

With regard to the wall thicknesses of the plastic components to be produced, these can be reduced by up to 35% with the proposed method and the proposed injection molding machine compared to conventional injection molding methods. For example, the wall thicknesses of covers, such as a front, in particular plate-like, flap, on a washing machine can be reduced from 3 mm to at least 2.5 mm, in particular to less than or equal to 2 mm. For example, the wall thicknesses of front covers of a porthole on a door of a washing machine or a tumble dryer or a washer-dryer can be reduced from 3 mm to at least 2.7 mm, in particular to less than or equal to 2.5 mm. Other plate-like or tub-like components, in particular as household appliance plastic parts, again of a larger type, can be produced, for example, with wall thicknesses of less than or equal to 1.7 mm, which with previous technology could only be produced with wall thicknesses equal to or greater than 2 mm.

In one embodiment, the at least one channel in a tool half is designed to circulate a second tempering medium having a fifth temperature for at least partial solidification of the at least one injection-molded plastic part in the interior of the injection mold, wherein this fifth temperature is set such that the at least one mold cavity of the filled closed injection mold is cooled to a fourth temperature below the first temperature.

In one embodiment, the injection molding machine has at least one heating device. This is in particular for heating a feed device of the injection molding machine for the supply of plastic material at a point upstream of the tool halves to a temperature within the processing window of the plastic material. In one embodiment, the injection molding machine has at least one pump for conveying at least one tempering medium. In one embodiment, the injection molding machine has a valve device for controlling a switching of the circulation between the first and second tempering medium. The device has at least one valve.

In one embodiment, the injection molding machine has a control unit. This is used in particular to control the components of the machine. In particular, the manufacturing process is controlled with it.

In one embodiment, the injection molding nozzle has a heatable nozzle core. The injection molding nozzle in particular has a housing that accommodates the nozzle core. The injection molding nozzle in particular has a preferably tapered nozzle channel with the front nozzle opening facing the mold cavity. This nozzle opening is the nozzle slot. This nozzle channel is formed in particular between the housing and the nozzle core. In particular, the injection molding nozzle also has a distribution channel for the plastic melt. This is formed between a feed channel for the plastic melt and the nozzle channel. In one embodiment, the nozzle core can be heated separately from the housing and therefore in particular also independently of the housing, in particular by a heater.

In one embodiment, the nozzle core of the injection molding nozzle is movably mounted in the housing to close the nozzle slot. The housing can be cooled in the area of the nozzle slot.

The information “top”, “bottom”, “front”, “back”, “horizontal”, “vertical”, “depth direction”, “width direction”, “height direction” indicates the positions and orientations that apply when the machine is used and positioned as intended.

Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also to be regarded as encompassed and disclosed by the invention that are not explicitly shown and explained in the figures, but which emerge and can be produced from the explained embodiments through separate combinations of features. Embodiments and combinations of features are also to be regarded as disclosed that therefore do not have all the features of an originally formulated independent claim.

• 1 eine schematische Schnittdarstellung eines Ausführungsbeispiels einer erfindungsgemäßen Spritzgießmaschine;
• 2 eine schematische Schnittdarstellung eines Ausführungsbeispiels einer Spritzgießdüse der Spritzgießmaschine;
• 3 eine schematische Frontansicht auf einen Düsenschlitz der Spritzgießdüse; und
• 4 ein vereinfachtes Ablaufdiagramm eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens.

Embodiments of the invention are explained in more detail below using schematic drawings. They show:

• 1 a schematic sectional view of an embodiment of an injection molding machine according to the invention;
• 2 a schematic sectional view of an embodiment of an injection molding nozzle of the injection molding machine;
• 3 a schematic front view of a nozzle slot of the injection molding nozzle; and
• 4 a simplified flow diagram of an embodiment of a method according to the invention.

In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

In 1 An embodiment of an injection molding machine 1 is shown in a schematic sectional view. The arrangement, size and shape of the components are by no means to be understood as exhaustive but merely as examples in order to demonstrate the basic structure of the injection molding machine 1 and to explain the process to be carried out with it.

The injection molding machine 1 has an injection molding tool 2. The injection molding tool 2 has a first tool half 3. This tool half 3 is a nozzle-side tool half. This means that it is closer to at least one injection molding nozzle 4 of the injection molding machine 1 than another tool half 5 of the injection molding tool 2. The two separate tool halves 3 and 5 form in particular the central components of the injection molding tool 2. In the 1 In the closed state of this injection molding tool 2, the tool halves 3 and 5 are placed against one another. The plastic melt or the molten plastic material can then be injected into at least one mold cavity 6 that is formed as a result, and the shape for the plastic part to be produced is thereby predetermined. The nozzle-side tool half 3 can represent a mold plate. The further tool half 5 remote from the nozzle can be an ejector plate. In one embodiment, at least one channel 7 can be formed in the tool half 3. At least one tempering medium, for example a liquid or gaseous tempering medium, can be passed through this at least one channel 7 as intended. As a result, at least the tool half 3 can be specifically heated. In particular, it can be heated at least in the area of the surface delimiting the mold cavity 6. In particular, it can be completely heated. In one embodiment, the further tool half 5 has at least one channel 8. The channel 8 is designed to pass through at least one tempering medium, which can in particular be gaseous or liquid. This also allows this further tool half 5 to be specifically heated. This too can be specifically heated at least in the area of the surface with which the at least one mold cavity 6 is delimited. In particular, the further tool half 5 can be completely tempered by this tempering medium that flows in the channel 8. The channel 7 and/or the channel 8 can be formed inside the respective tool half 3 or 5. However, they can also be formed in some areas only on a rear side 3a and/or 5a facing away from the other tool half 3, 5. In this regard, they can be open at least in some areas towards this rear side 3a and/or 5a. It is possible that the at least one channel 7 and/or the at least one channel 8 is only finally closed for the circulation of a temperature control medium when the two tool halves 3, 5 are arranged in their final position in the injection molding machine 1.

The at least one channel 7 and/or the at least one channel 8 from which in 1 for the sake of clarity, only one cross-sectional area is provided with the reference number, is designed in particular to heat the mold cavity 6 to a specific temperature, in particular a second temperature, during the injection of a plastic melt 9, which represents a heated plastic material. In the exemplary embodiment, this plastic material 9 is injected with the at least one injection molding nozzle 4 with an injection pressure of less than 90 kg/m ² . This plastic material 9 has a first temperature within the processing window of the plastic material 9. The mold cavity 6 is tempered to the second temperature in particular by circulating a first tempering medium in the channel 7 and/or the channel 8. This first tempering medium has in particular a third temperature, which has at least one temperature within the processing window of the injected plastic material 9. However, the third temperature can also be higher.

On the other hand, the at least one channel 7 and/or the at least one channel 8 are also provided or are designed and intended to circulate a tempering medium, in particular a second tempering medium, for at least partial solidification of the at least one injection-molded plastic part 10 inside the injection molding tool 2. This second tempering medium can have a fifth temperature. This is set in such a way as to cool the at least one mold cavity 6 of the filled, closed injection molding tool 2 to a fourth temperature. This fourth temperature is in particular below the first temperature. The injection molding nozzle 4 is designed to introduce the plastic melt or the plastic material 9 into the at least one mold cavity 6. The injection molding nozzle 4 is specifically configured. It has an elongated nozzle slot as a nozzle opening on the mold cavity side, from which this plastic melt or the plastic material 9 is injected in the form of a flat strip-shaped strand through the nozzle slot into at least this one mold cavity 6 of the injection molding tool 2.

The injection molding machine 1 can also have an ejector system 11. This can be used to open the two adjacent mold halves 3 and 5 when they are closed. The adjacent mold halves 3 and 5 are separated using the ejector system 11. In particular, the mold half 5 remote from the nozzle is pushed away from the mold half 3 near the nozzle. The plastic part 10 produced can then be ejected.

In particular, the tool half 3 is made at least in part from aluminum or an aluminum alloy. In particular, the tool half 5 remote from the nozzle is made from aluminum or an aluminum alloy.

It is also possible for the tool half 3 to be formed from a specific material at least in some areas on an inner side 3b. This can be different from the base material of the tool half 3. This specific material can be a carbonized material layer. This material layer can be a coating. This material layer 12 has a higher hardness than the base material, in particular aluminum or the aluminum alloy, of the tool half 3. In one embodiment, an inner side 5b of the tool half 5 remote from the nozzle can also be designed accordingly. Here too, in particular, a carbonized material layer 13 can then be formed. It can be provided that this material layer 12 and/or 13 is formed over the entire inner side 3b and/or the entire inner side 5b. In this context, the inner side 3b can be formed by the surface by which the mold cavity 6 is delimited, in particular also additionally formed by the rear side 3a. The same can be provided for the inner side 5b.

In addition, the injection molding machine 1 can have a feed device 14. This is used to feed the plastic material or the plastic melt 9 to the injection molding tool 1, in particular with a conveyor unit 14a, such as a spindle or a conveyor screw. The injection molding machine 1 can also have a heating device 15. This can be used to heat, in particular melt, the plastic granulate, which can be fed to the feed device 14 via an introduction device 16.

In particular, the injection molding machine 1 can also have at least one pump 17. This pump is used to convey the first tempering medium and/or the second tempering medium.

In addition, the injection molding machine 1 also has a control unit 18. This is used to control at least some of the components of the injection molding machine 1.

In particular, it also controls the process for producing a plastic component, which is explained below.

In addition, 1 a sprue area 19 of the injection molding machine 1 is shown.

In 2 An example of the injection molding nozzle 4 is shown in a schematic sectional view. This has a housing 20. The injection molding nozzle 4 has an elongated nozzle slot 21. The plastic melt emerges from this in the form of a flat-band-shaped melt strand. The plastic melt is therefore injected in the form of such a flat-band-shaped melt strand through the nozzle slot 21 into at least one mold cavity 6 of the injection molding tool 2.

In one embodiment, the injection molding nozzle 4 has a nozzle core 22.

It is possible that the housing 20 has at least one cooling channel 23.

Furthermore, it can be provided that a feed channel 24 is formed, via which the plastic material 9 is fed into a preferably existing distribution channel 25 of the injection molding nozzle 4.

In 3 a plan view of the injection molding nozzle 4, in particular of the nozzle slot 21, is shown schematically. The nozzle slot 21 can be seen. It has a rectangular shape here. In particular, the cross-sectional area of this nozzle slot 21 is between 40 mm2 and 60 mm2. The nozzle slot 21 has a length l and a width b.

In 4 a schematic flow diagram is shown, by means of which the method for injection molding at least one plastic part 10, in particular a household appliance plastic part, is explained.

1. a) Bestücken der Spritzgießmaschine 1 mit einem Spritzgießwerkzeug 2, das zumindest eine Formkavität 6 begrenzt, wobei das Spritzgießwerkzeug 2 eine erste Werkzeughälfte 3 und eine dazu separate zweite Werkzeughälfte 5 aufweist, wobei durch ein Aneinanderbringen der Werkzeughälften 3, 5 das Spitzgießwerkzeug 2 geschlossen wird und dadurch die zumindest eine Formkavität 6 begrenzt wird,
2. b) Bereitstellen von Kunststoffmaterial 9, das eine erste Temperatur innerhalb des Verarbeitungsfensters des Kunststoffmaterials aufweist,
3. c) Erwärmen der mindestens einen Formkavität 6 auf eine zweite Temperatur innerhalb des Verarbeitungsfensters des Kunststoffmaterials und Halten des Spritzgießwerkzeugs 2 im geschlossenen Zustand auf der zweiten Temperatur,
4. d) Einspritzen von Kunststoffmaterial 9, insbesondere eines thermoplastischen Materials, das die erste Temperatur aufweist, mit zumindest einer Spritzgießdüse 4 der Spritzgießmaschine 1 in das geschlossene erhitzte Spritzgießwerkzeug 1 bei einem Einspritzdruck von weniger als 90 kg/cm2, um die zumindest eine Formkavität 6 zu füllen, wobei beim Einspritzen das Kunststoffmaterial 9 aus einem länglichen Düsenschlitz 21 der Spritzgießdüse 4 ausläuft und das Kunststoffmaterial 9 in Form eines flachbandförmigen Schmelzstrangs durch den Düsenschlitz 21 in die zumindest eine Formkavität 6 des Spritzgusswerkzeugs 2 eingespritzt wird.

The procedure involves the following steps:

1. a) equipping the injection molding machine 1 with an injection molding tool 2 which defines at least one mold cavity 6, wherein the injection molding tool 2 has a first tool half 3 and a separate second tool half 5, wherein the injection molding tool 2 is closed by bringing the tool halves 3, 5 together and thereby defining the at least one mold cavity 6,
2. b) providing plastic material 9 having a first temperature within the processing window of the plastic material,
3. c) heating the at least one mold cavity 6 to a second temperature within the processing window of the plastic material and keeping the injection mold 2 in the closed state at the second temperature,
4. d) Injecting plastic material 9, in particular a thermoplastic material having the first temperature, with at least one injection molding nozzle 4 of the injection molding machine 1 into the closed heated injection molding tool 1 at an injection pressure of less than 90 kg/cm2 in order to fill the at least one mold cavity 6, wherein during injection the plastic material 9 flows out of an elongated nozzle slot 21 of the injection molding nozzle 4 and the plastic material 9 is injected in the form of a flat ribbon-shaped melt strand through the nozzle slot 21 into the at least one mold cavity 6 of the injection molding tool 2.

The plastic material 9 is provided as a plastic melt and injected.

Preferably, step c) is carried out as follows: heating the at least one mold cavity 6 to a second temperature within the processing window of the plastic material 9 and keeping the injection mold 2 in the closed state at the second temperature by circulating a first tempering medium having a third temperature through at least one channel 7, 8 which is formed in at least one of the tool halves 2, 5, in particular integrated.

Preferably, after step d), a step e) is carried out as follows: cooling the at least one mold cavity 6 of the filled closed injection molding tool 2 to a, in particular fourth, temperature below the first temperature until at least one injection-molded plastic part 10 is at least partially solidified in the interior of the injection molding tool 2.

Preferably, the cooling in step e) is carried out by circulating a, in particular second, tempering medium, which has a, in particular fifth, temperature, through the at least one channel 7, 8.

Preferably, in step d), the injection of plastic material 9 at the first temperature is carried out at an injection pressure which is less than 78 kg/cm2, more preferably less than 58 kg/cm2, and even more preferably at an injection pressure between 17 and 52 kg/cm2.

Preferably, at least the first tempering medium is heated to at least one temperature within the processing window of the plastic material (9) or higher, in particular to at least 150°C, or at least 200°C, or at least 300°C, wherein the first tempering medium is preferably an oil.

Preferably, the second temperature is set equal to or higher than the first temperature. In particular, the fifth temperature is set lower than the third temperature, optionally the fifth temperature is set lower than the lowest temperature of the processing window of the plastic material. In particular, the fourth temperature is set lower than the lowest temperature of the processing window of the plastic material.

Preferably, the second temperature is set 18 °C or more higher than the first temperature, and/or the fifth temperature is set 18 °C or more lower than the fourth temperature.

Preferably, a liquid medium, in particular a mineral oil, is used as the second tempering medium, which is tempered to a fifth temperature of 42 °C or below, optionally equal to or below 32 °C.

Preferably, the housing 20 of the injection molding nozzle 4 is cooled at least in the region of the nozzle slot 21.

Preferably, heat is supplied to the plastic material 9 during solidification in the mold cavity 6 by heating a nozzle core 22 of the injection molding nozzle 4 relative to a housing 20 of the injection molding nozzle 4 in the sprue area 19, so that the sprue is torn off along the nozzle slot 21 when the injection molded plastic part 10 is demolded due to the temperature gradient between the solidified plastic part 10 and the plastic material 9 in the sprue area 19.

• f) Öffnen des Spritzgießwerkzeugs 2 durch Trennen der düsenseitigen Werkzeughälfte 3 von der düsenfernen Werkzeughälfte 5; und
• g) Auswerfen des zumindest einen, wenigstens teilweise verfestigten gegossenen Kunststoffteils 10 durch Betätigung von Auswerferelementen des Auswerfersystems 11 der düsenfernen Werkzeughälfte 5.

Preferably, the following steps are carried out following step d):

• f) opening the injection molding tool 2 by separating the nozzle-side tool half 3 from the nozzle-remote tool half 5; and
• g) Ejecting the at least one, at least partially solidified molded plastic part 10 by actuating ejector elements of the ejector system 11 of the tool half 5 remote from the nozzle.

List of reference symbols

1

Injection molding machine

2

Injection molding tool

3

Tool half

3a

back

3b

inside

4

Injection molding nozzle

5

Tool half

5a

back

5b

inside

6

Mold cavity

7

channel

8th

channel

9

Plastic material

10

Plastic part

11

Ejector system

12

Material layer

13

Material layer

14

Feeding device

14a

Conveyor unit

15

Heating device

16

Insertion device

17

pump

18

Control unit

19

Gate area

20

Housing

21

Nozzle slot

22

Nozzle core

23

Cooling channel

24

Feed channel

25

Distribution channel

l

Length

b

Width

x

Width direction

y

Altitude direction

z

Depth direction

A

Longitudinal axis

Claims (15)

Method for injection molding at least one plastic part (10) by means of an injection molding machine (1), comprising the following steps: a) equipping the injection molding machine (1) with an injection molding tool (2) which delimits at least one mold cavity (6), wherein the injection molding tool (2) has a first tool half (3) and a separate second tool half (5), wherein the injection molding tool (2) is closed by bringing the tool halves (3, 5) together and thereby delimiting the at least one mold cavity (6), b) providing plastic material (9) which has a first temperature within the processing window of the plastic material, c) heating the at least one mold cavity (6) to a second temperature within the processing window of the plastic material and keeping the injection molding tool (2) in the closed state at the second temperature, d) injecting plastic material (9) which has the first temperature with at least one injection molding nozzle (4) of the injection molding machine (1) into the closed, heated Injection molding tool (1) at an injection pressure of less than 90 kg/cm2 to fill the at least one mold cavity (6), wherein during injection the plastic material (9) flows out of an elongated nozzle slot (21) of the injection molding nozzle (4) and the plastic material (9) is injected in the form of a flat-band-shaped melt strand through the nozzle slot (21) into the at least one mold cavity (6) of the injection molding tool (2). Procedure according to Claim 1 , characterized in that step c) is carried out as follows: heating the at least one mold cavity (6) to a second temperature within the processing window of the plastic material (9) and holding the injection molding tool (2) in the closed state at the second temperature by circulating a first tempering medium, which has a third temperature, through at least one channel (7, 8) which is formed in at least one of the tool halves (2, 5), in particular integrated. Procedure according to Claim 1 or 2 , characterized in that after step d) a step e) is carried out as follows: cooling the at least one mold cavity (6) of the filled closed injection molding tool (2) to a, in particular fourth, temperature below the first temperature until an at least partial solidification of the at least one injection-molded plastic part (10) in the interior of the injection molding tool (2). Procedure according to Claim 3 , characterized in that the cooling in step e) is carried out by circulating a, in particular second, tempering medium, which has a, in particular fifth, temperature, through the at least one channel (7, 8). Method according to one of the preceding claims, characterized in that a thermoplastic material is injected as the plastic material (9). Method according to one of the preceding claims, characterized in that the nozzle-side tool half (3) and/or the nozzle-remote tool half (5) are made of aluminum or an aluminum alloy. Method according to one of the preceding claims, characterized in that in step d) the injection of plastic material (9) at the first temperature is carried out at an injection pressure which is less than 78 kg/cm2, more preferably less than 58 kg/cm2, and even more preferably at an injection pressure between 17 and 52 kg/cm2. Method according to one of the preceding claims, characterized in that at least the first tempering medium can be heated to at least one temperature within the processing window of the plastic material (9) or higher, in particular to at least 150°C, or at least 200°C, or at least 300°C, wherein the first tempering medium is preferably an oil. Method according to one of the preceding claims, characterized in that the second temperature is set equal to or higher than the first temperature, and/or the fifth temperature is set lower than the third temperature, optionally the fifth temperature is set lower than the lowest temperature of the processing window of the plastic material and/or the fourth temperature is set lower than the lowest temperature of the processing window of the plastic material. Method according to one of the preceding claims, characterized in that the second temperature is set 18 °C or more higher than the first temperature, and/or the fifth temperature is set 18 °C or more lower than the fourth temperature. Method according to one of the preceding claims, characterized in that a liquid medium, in particular a mineral oil, is used as the second tempering medium, which is tempered to a fifth temperature of 42 °C or below, optionally equal to or below 32 °C. Method according to one of the preceding claims, characterized in that the housing (20) of the injection molding nozzle (4) is cooled at least in the region of the nozzle slot (21). Method according to one of the preceding claims, characterized in that heat is supplied to the plastic material (9) during solidification in the mold cavity (6) by heating a nozzle core (22) of the injection molding nozzle (4) relative to a housing (20) of the injection molding nozzle (4) in the sprue area (19), so that the sprue is torn off along the nozzle slot (21) when the injection molded plastic part (10) is demolded due to the temperature gradient between the solidified plastic part (10) and the plastic material (9) in the sprue area (19). Method according to one of the preceding claims, characterized in that the following steps are carried out following step d): f) opening the injection molding tool (2) by separating the nozzle-side tool half (3) from the nozzle-remote tool half (5); and g) ejecting the at least one, at least partially solidified molded plastic part (10) by actuating ejector elements (11) of the nozzle-remote tool half (5). Injection molding machine (1) with an injection molding tool (2) which has a nozzle-side tool half (3) and a nozzle-distant tool half (5), wherein the tool halves (2, 5) delimit at least one mold cavity (6) in the closed state of an injection molding tool (3), wherein at least one of the tool halves (2, 5) is traversed by at least one open channel (7, 8), wherein the at least one channel (7, 8) is only finally closed for the circulation of a tempering medium when the tool halves (2, 5) are arranged in their end position in the injection molding machine (1), wherein the at least one channel (7, 8) is designed to - during the injection at an injection pressure of less than 90 kg/m2 of a plastic material (9) which is at a first temperature within the processing window of the plastic material (9), a first tempering medium which has a, in particular third, temperature equal to or higher than a temperature within of the processing window of the injected plastic material (9) to circulate in the at least one mold cavity (6) in order to heat the at least one mold cavity (6) to a second temperature, and - for at least partial solidification of the at least one injection-molded plastic part (10) inside the injection mold (2), to circulate a second tempering medium which has a, in particular fifth, temperature which is set to cool the at least one mold cavity (6) of the filled closed injection mold (2) to a, in particular fourth, temperature below the first temperature, and - with at least one injection molding nozzle (4) for introducing a plastic material (9) into the at least one mold cavity 6), wherein the injection molding nozzle (4) has an elongated nozzle slot (21) from which the plastic material (9) in the form of a flat-band-shaped melt strand flows through the nozzle slot (21) into at least one mold cavity (6) of the injection molding tool (2).

Images