AT526618A1 - Method and device for producing a hollow-walled component - Google Patents

Abstract

The invention relates to a method for producing a hollow-walled component with a reproducible residual wall thickness by determining at least one target value of a fluid volume flow to be generated by a fluid injection system during fluid-injected plastic injection molding, wherein an injection molding machine injects a plasticized material melt into a molding cavity; wherein a fluid injection system is provided to displace the melt from the interior of the component, which injects a fluid that generates the fluid volume flow (pressure/time profile), preferably gas or water, into the molding cavity via an injector arranged on the injection molding tool; and wherein at least one target value of the fluid volume flow (pressure/time profile) is determined on the basis of at least one process parameter and/or at least one machine parameter of the injection molding machine, wherein a relationship between the at least one process parameter and/or the at least one machine parameter and the fluid volume flow is derived in order to produce the reproducible residual wall thickness of the hollow-walled component; and the at least one target value of the fluid volume flow and/or the fluid pressure is redetermined based on the relationship.

Description

The invention relates to a method for producing a structural component made of thermoplastic material having at least one cavity in the interior. The invention further relates to a device which is provided for carrying out the method according to the invention, as well as a computer program product.

The hollow-walled structural components considered here are manufactured using the injection molding process, which usually comprises the following process steps: closing a configured injection molding tool, injecting a plasticized plastic melt into the closed injection molding tool, injecting at least one fluid into the closed injection molding tool to displace the plastic core from the interior of the hollow-walled structural component, opening the injection molding tool and demolding the cooled structural component.

Apart from the process steps mentioned above, the injection molding process can still be carried out according to one of the following process variants:

a) Inflation process

b) Secondary cavity

c) Mass back pressure

d) Special procedure with projectile

e) “Co-injection” (multi-component)

Furthermore, the process or process step of fluid injection must be considered separately depending on the type of fluid. The injection of a gaseous medium is attributed to the so-called "Gas Injection Technology" (GIT), whereas the use of an aqueous solution is assigned to the "Water Injection Technology" (WIT). In addition to the medium used, there are also other differences between the aforementioned technologies. For example, with regard to the regulation or control of the fluid injection

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electricity

In addition, in GIT, an inert gas (e.g. nitrogen) is usually compressed to 300 to 350 bar using a compressor and stored in a compressed gas cylinder. The gas stored in the compressed gas cylinder is then used to supply the control valves integrated into the process for the fluid-assisted injection molding process. To be more precise, the control valves regulate the gas supply to the closed injection molding tool based on a pressure profile that can be set, so that an appropriate gas volume flow is established. The gas is then injected into the molding component cavity via injectors mounted in the injection molding tool.

Unlike with GIT, with WIT the intended fluid volume flow is set on a WIT system. A pump is also provided for the actual regulation of the set fluid volume flow. For this purpose, a start signal for injecting the fluid (e.g. water) is transmitted to the WIT system during the injection molding process. The WIT system then opens an injector mounted in or on the injection molding tool and the fluid is pumped into the

Component cavity injected.

With regard to the quality of the injected structural components, the above-mentioned technologies always have the disadvantage that neither the GIT nor the WIT record the process fluctuations that usually occur during injection molding or compensate them as far as possible through active control. In other words, the respective fluid volume flow is always consistently controlled or adjusted according to a preselected pressure/time profile (GIT) or a preselected volume flow and/or pressure, time profile (WIT), without taking into account the process fluctuations that occur during injection molding. The quality of the structural components produced using the injection molding process can be significantly influenced by a large number of the numerous process and machine parameters.

be influenced.

quality of the manufactured components and the reproducibility of production.

In the course of this, useful software (tools) have already been developed in the past that not only make it possible to generally record and document process fluctuations during injection molding, but also actively compensate for these during the injection process. An example of such software is the "IQ-Weightcontrol" program (ENGEL). With the help of the software in question, for example, fluctuations in the lock closing behavior (affects the non-return valve of the injection unit) are recorded, whereupon the software actively shifts or adjusts the injection profile. In this way, the injection work can be kept almost constant. In contrast to the method according to the invention, however, only one process or machine parameter, such as the injection work, is actively recorded and redetermined if necessary.

Another, not insignificant cause of process fluctuations is fluctuations in material viscosity. Such fluctuations in material viscosity mean that the flow behavior of the material plasticized in the injection unit of an injection molding machine is always unsteady or has varying degrees of difficulty in flowing. This not only causes an unsteady closing behavior of the non-return valve during the injection process of the plasticized material, but also an “ACTUAL pressure curve” that deviates from a “TARGET pressure curve”. This in turn means that the actual injection performance inside the injection mold differs from the reference pattern and, as a result, an unsteady internal mold pressure is present. All in all, the process fluctuations lead to significant quality deficits compared to

the desired component quality of the manufactured components.

parts can be assumed.

Thus, all process fluctuations, such as viscosity, pressure, temperature and/or time deviations, result in the residual wall thickness of the component to be produced not being the same or, in other words, that the fluid injected into the injection molding tool presses different amounts of non-solidified core material (i.e. plastic core) out of the component.

Structural components that are manufactured using fluid injection technology (i.e. in particular for the production of closed tube geometries) have a higher torsional stiffness overall than conventional rib structures manufactured using injection molding (with the same wall thickness, the same material and the same mass). Based on this advantageous property, the various fluid injection technologies can be used accordingly for the production of hollow-walled structural components. However, if the remaining wall thickness of a component varies due to process fluctuations, the component stiffness will inevitably also vary. Falling below the required component stiffness can in turn lead to structural failure as a result of the loads that occur, i.e. the structural integrity is no longer present, which can be the case, for example, with a structural component.

part intended for a two-wheeler must be avoided at all costs.

Based on the disadvantages outlined above, the present invention is therefore based on the object of providing a reliable method for controlling or actively compensating for the numerous process fluctuations associated with fluid-assisted injection molding processes, thereby improving the quality of the

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According to the invention, in order to achieve the above-mentioned object, a method for producing a hollow-walled component with a reproducible residual wall thickness by determining at least one target value of a fluid volume flow to be generated by a fluid injection channel during fluid-injected plastic injection molding according to the features of claim 1 is provided, with preferred embodiments being the subject of the subclaims. A device according to the invention results from claim 21.

In general, the method according to the invention requires an injection molding machine that injects a plasticized material melt into a molding cavity. In order to displace the plasticized material melt from the interior of the component, a fluid injection system is also provided, which injects an auxiliary fluid that generates the fluid volume flow, which can be suitable gases or liquids such as water, into the molding cavity via an injector arranged in or on the injection mold. In this case, a target value of the fluid volume flow is determined on the basis of at least one process parameter and/or at least one machine parameter of the injection molding machine.

According to the invention, a relationship between the at least one process parameter and/or the at least one machine parameter and the fluid volume flow is derived in order to adjust the remaining wall thickness of the hollow-walled component. The at least one target value of the fluid volume flow and/or the fluid pressure is then re-determined based on the relationship.

Accordingly, in an advantageous embodiment of the method according to the invention, it is provided that the at least one process parameter and/or the at least one machine parameter is transmitted directly to the fluid injection system.

which calculates a new setpoint value of the fluid volume flow.

According to another variant of the method according to the invention, it is provided that the injection molding machine calculates the new target value of the fluid volume flow and/or the fluid pressure and transmits it to the fluid injection system.

According to another advantageous embodiment of the method according to the invention, the injection molding machine transmits the at least one process parameter and/or the at least one machine parameter to an external device, which calculates a new target value of the fluid volume flow and/or the fluid pressure based on the received parameter and transmits this to the fluid injection system

transmits.

Preferably, the injection molding machine is connected to the external device, wherein the external device is connected to the fluid injection system via an electronic interface

connected is.

The electronic interface enables information to be exchanged between the injection molding machine, the fluid injection system and/or the external device. The configuration of the system equipment can be connected as desired. In this way, the fluid injection technology or the fluid injection system can actively influence process fluctuations that occur during injection molding, for example by the injection molding machine informing the fluid injection system via the interface about deviations from the preset parameters during injection molding. Based on the preset parameters

actively increase the flow of human energy.

Furthermore, the process data (information) transmitted to the fluid system via the interface can also be used to actively adapt the fluid volume flow to be injected to recorded viscosity fluctuations, which are usually caused or influenced by numerous influencing factors. This adaptation can be carried out, for example, using special software which, based on the recorded process fluctuations during injection molding, actively adapts the fluid volume flow or a pressure/time profile underlying the process, so that the desired remaining wall thickness of a component to be manufactured can always be kept constant.

The interface is preferably a Euromap 62 interface, although other interfaces such as a bus interface, an Ethernet or wireless connection are also conceivable.

A special feature of the special software is that the software processes the recorded process parameters and/or machine parameters in parallel. For example, preferred actual machine parameters such as the torque during dosing, the mass or cylinder temperature, the injection pressure, the injection speed, the injection work, the internal mold pressure, the mass cushion, the mold temperature, the injection pressure curve and the associated integral thereof, the so-called flow number, the position of the plasticizing screw, the holding pressure, the holding pressure time, the hot runner temperature and the like can be processed in parallel in order to permanently adjust the fluid volume flow with a high degree of accuracy to

to adapt to process fluctuations. Based on the parameters to be processed, the special software determines

or an algorithm that adjusts the fluid volume flow or the pressure/time profile necessary to compensate for the process fluctuations that occur, so

It is also possible to easily implement or retrofit the software in existing systems in the form of an additional module. In this case, the additional module could be configured to store recorded process data in a targeted manner in a "cloud". The collected process data could be retrieved by an AI to create a self-learning system.

the.

In addition, the special software or additional module can be used to detect various changes (e.g. material wear) in the hardware of the fluid system. This in turn allows timely measures (i.e. before a machine downtime) to be initiated, such as a preventive alarm, automatic ordering of spare parts or the like.

In an alternative advantageous process control, the injection molding machine is connected directly to the fluid injection system or to components of the fluid injection system via the electronic interface.

Preferably, the components are control valves, pumps, injectors, nozzles, pneumatic control elements, hydraulic control elements and/or the like.

According to a further advantageous embodiment of the method according to the invention, it is provided that the fluid volume flow corresponds to a certain volume flow

profile and/or the fluid pressure corresponds to a certain pressure profile.

Yet another advantageous variant of the method provides that an assignment of the at least one process parameter and/or the at least one machine parameter during injection of the plasticized plastic melt is used as a variable.

According to an alternative advantageous method, the relationship is an assignment of the at least one process parameter and/or the at least one machine parameter during the plasticizing of the plastic to be cast

used as a size by the injection unit.

Alternatively, the quantity used here can represent the required torque of the plasticizing screw, a temperature range of the melt cylinder temperatures, the melt temperature of the plastic to be cast and/or the like.

Yet another advantageous embodiment of the invention provides that the relationship is an assignment of the at least one process parameter and/or the at least one machine parameter of the forming injection molding tool.

tool is used as a size.

Preferably, the variable used here represents at least one temperature value of the hot runner, a temperature of the tool wall, the tool-mold interior

pressure, measurements of wall thicknesses.

According to another advantageous embodiment, a relationship between a measured actual value curve and the associated setpoint volume flow curve and/or the pressure curve during fluid injection is determined in order to determine at least one derived variable and/or at least one of the parameters.

voices.

Advantageously, the aforementioned method variant can be designed such that the at least one derived variable and/or the at least one parameter is used for adjustments and/or for active changes to setting parameters of the fluid injection system and/or the injection molding machine.

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adapts or redefines the process parameters.

According to another advantageous variant of the method according to the invention, the injection molding machine preferably makes adjustments or active changes to the process parameters of the injection molding machine by means of the internal control and regulation parameters transmitted by the fluid injection system, wherein the transmitted internal control and regulation parameters are used to adjust and/or change the cylinder temperatures, to actively regulate the material viscosity, the holding pressure time, the holding pressure level, the back pressure, the switchover point, the dosing capacity, the

screw speed and/or the like are provided.

Furthermore, in an alternative variant of the method according to the invention,

It can be seen that the temperature of the fluid is actively adjusted.

Alternatively, the hollow-walled component may be a structural component for a two-wheeler.

In addition to the method according to the invention, the present invention is also directed to a device for controlling the remaining wall thickness during the production of a hollow-walled component, characterized in that the component is produced by means of the method according to one of the aforementioned method variants. According to the invention, the device comprises at least one injection molding tool with a shaping cavity; a compatible fluid injection system; and a controller that is set up or configured to carry out the method according to the invention

to execute.

Finally, the present invention relates to a computer program product comprising

send commands that, when the program is executed, cause the device

according to claim 21, the steps of the method according to one of claims 1 to 20 10

All in all, the present invention represents an excellent solution for achieving a reproducible residual wall thickness of the component with regard to the production of components made of thermoplastic and elastomeric plastics.

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Claims (1)

Method for producing a hollow-walled component with a reproducible residual wall thickness by determining at least one setpoint value of a fluid volume flow to be generated by a fluid injection system during fluid-injected plastic injection molding, wherein an injection molding machine injects a plasticized material melt into a molding cavity; wherein a fluid injection system is provided to displace the melt from the interior of the component, which injects a fluid, preferably gas and/or water, generating the fluid volume flow and/or the fluid pressure, into the molding cavity via an injector arranged on or in the injection mold; and wherein at least one setpoint value of the fluid volume flow is determined on the basis of at least one process parameter and/or at least one Machine parameters of the injection molding machine, characterized in that to produce the reproducible residual wall thickness of the hollow-walled component, a relationship between the at least one process parameter and/or the at least one machine parameter and the fluid volume flow is derived; and the at least one target value of the fluid volume flow and/or the fluid pressure is redetermined based on the relationship becomes. Method according to claim 1, characterized in that the at least one process parameter and/or the at least one machine parameter is transmitted directly to the fluid injection system, which generates a new Setpoint or a new setpoint profile of the fluid volume flow is calculated. Method according to claim 1, characterized in that the injection molding machine calculates the new setpoint value or the new setpoint value profile of the fluid volume flow and/or the fluid pressure and transmits it to the fluid injection system transmits. Method according to claim 1, characterized in that the injection molding machine transmits the at least one process parameter and/or the at least one machine parameter to an external device which determines the new setpoint or the new setpoint profile of the fluid volume flow and/or the fluid pressure is calculated and transmitted to the fluid injection system. Method according to claim 4, characterized in that the injection molding machine is connected to the external device, wherein the external device is an electronic interface is connected to the fluid injection system. Method according to one of claims 1 to 3, characterized in that the injection molding machine is connected directly to the fluid injection system or to components of the fluid injection system via an electronic interface. is bound. Method according to claim 6, characterized in that the components are control valves, pumps, injectors, nozzles, pneumatic Control elements, hydraulic control elements and/or the like. Method according to one of the preceding claims, characterized in that the fluid volume flow corresponds to a specific volume flow profile and/or the fluid pressure corresponds to a specific pressure and/or time profile, wherein the specific profiles can be linked in order to calculate the volume flow and the fluid pressure in a common volume flow profile. /pressure/time profile. Method according to one of the preceding claims, characterized in that the relationship is an assignment of the at least one process parameter and/or the at least one machine parameter in the Injection of the plasticized plastic melt is used as a size. Method according to claim 9, characterized in that the variable used is the pressure curve during the injection process, the integral of the pressure curve, the injection speed, the curve of the injection speed, 12. 13. 14. 15. the mass cushion, the position of the plasticizing screw and/or the like. Method according to one of claims 1 to 8, characterized in that an assignment of the at least one process parameter and/or the at least one machine parameter during the plasticizing of the plastic to be cast by the injection unit is used as a variable as the relationship becomes. Method for controlling the residual wall thickness according to claim 11, characterized in that the variable used is the required torque of the plasticizing screw, a temperature range of the melt cylinder temperatures, the melt temperature of the plastic to be cast and/or the like. chen represents. Method according to one of claims 1 to 8, characterized in that an assignment of the at least one process parameter and/or the at least one machine parameter of the shaping injection molding tool is used as a variable as the relationship. Method according to claim 13, characterized in that the variable used represents at least a temperature value of the hot runner, a temperature of the tool wall, the internal mold pressure, measurements of the wall thicknesses, in particular with ultrasound. Method according to one of claims 9 to 14, characterized in that a relationship between a measured actual value curve and the associated setpoint volume flow curve and/or the pressure curve during fluid injection is determined in order to determine at least one derived variable and/or to determine at least one of the parameters. 17. 18. 19. 20. 21. Method according to claim 15, characterized in that the at least one derived variable and/or the at least one parameter is used for adjustments and/or for active changes in setting parameters of the fluid injection system and/or the injection molding machine. Method for controlling the residual wall thickness according to one of the preceding claims, characterized in that the fluid injection system monitors a plurality of process parameters, in particular internal control and regulation parameters, and adjusts them in accordance with a detected change in the process parameters. parameters are adjusted or redefined. Method according to one of the preceding claims, characterized in that the injection molding machine makes adjustments or active changes to the process parameters of the injection molding machine by means of the internal control and regulation parameters transmitted by the fluid injection system, wherein the transmitted internal control and regulation parameters are provided for adjusting and/or changing the cylinder temperatures, for actively regulating and/or controlling the material viscosity, the injection speed, the holding pressure time, the holding pressure level, the back pressure, the switching point, the dosing capacity, the screw speed and/or the like. Method according to one of the preceding claims, characterized in that the temperature of the fluid is actively adjusted. Method according to one of the preceding claims, characterized in that the hollow-walled component is an automotive component, a media line or a component for a two-wheeler. Device for producing a hollow-walled component with reproducible residual wall thickness according to a method according to one of the preceding claims, characterized by: an injection molding tool with a forming cavity; a fluid injection system; and 23. a controller configured to carry out the method. Computer program product comprising instructions which, when executing the program, cause the device according to claim 21 to perform the steps of Method according to one of claims 1 to 20. Computer program product according to claim 22, characterized in that the commands, when executing the program, cause the results of a virtual, digital filling or production simulation to be delivered and compared with the residual wall thicknesses determined using the methods defined in claim 14 for determining the residual wall thickness and/or other measuring methods, such as computer tomography or X-rays, and then the production parameters of the injection molding machine and/or the Fluid injection system according to claims 7 to 13.