Forming machine with a plasticizing unit

Abstract

Forming machine with: a plasticizing unit, wherein the plasticizing unit comprises: - a feeding device for feeding a plastic granulate to a plasticizing cylinder (21) - a plasticizing cylinder (21) in which a screw (22) is rotatably arranged for plasticizing plastic granules - a dosing drive (14) for rotating the screw (22) - a tempering device for tempering a wall (21a, 21b) of the plasticizing cylinder (21), wherein the tempering device has at least two tempering zones (40, 41, 42, 43) for tempering different sections of the wall (21a, 21b) of the plasticizing cylinder (21) - a temperature measuring device (40a, 41a, 42a, 43a) for detecting a temperature of the plasticizing cylinder (21) and / or a melt produced from plasticized plastic granulate in the plasticizing cylinder (21) for the at least two tempering zones (40, 41, 42, 43) and / or for the screw antechamber - a measuring device (14a, 15a) for detecting a torque exerted on the screw (22) by the metering drive (14) and / or a rotational speed of the screw (22) and / or a back pressure exerted on the screw (22) by the melt and / or a metering stroke of the screw (22) and with a control device (60) which is connected to the dosing drive (14), the tempering device, the temperature measuring device (40a, 41a, 42a, 43a) and the measuring device (14a, 15a) characterized in that the control device (60) is designed to control - the tempering device for tempering the different sections of the wall of the plasticising cylinder and / or - the dosing drive (14) depending on the - torque and / or speed and / or dynamic pressure and / or a metering stroke of the screw (22) detected by the measuring device (14a, 15a, 16a) and / or a temperature measured by the temperature measuring device (40a, 41a, 42a, 43a) using an energy-balancing model of the plasticizing process and that the energy-balancing model of the plasticizing process is composed of interconnected submodels, wherein one submodel is designed as a drive model describing the dosing drive, one submodel is designed as a thermal model describing the tempering device, and one submodel is designed as a process model describing the plasticizing process of the plastic granulate.

Description

[0001] The present invention relates to a forming machine having the features of the preamble of claim 1 or claim 2.

[0002] A generic molding machine is disclosed in JP 2013-224017 A. Using a model-based approach for the temperature profile along the plasticizing cylinder, a supposedly optimal solution for the temperature profile is calculated. While the temperature differences are kept as small as possible, various influencing variables on the temperature profile are not taken into account. Control variables other than the temperature control device are not considered at all, so that a different temperature profile than desired may occur. Other similar solutions known from the prior art are disclosed in JP 2007076328 A, JP 2001225372 A, JP 2001260193 A, AT 256 440 B, and DE 10 2010 024 267 A1.

[0003] Furthermore, EP 2 700 488 A1 discloses a molding machine whose plasticizing cylinder can be heated by heating devices. Said heating devices are monitored with regard to a difference between the heating energy during injection molding and the heating energy in the stationary state. In particular, an energy difference between the plasticizing cylinder and the heating bands is measured via several sensors or the energy consumption of the heating bands. This energy difference is used to determine whether the heating energy of the heating bands is currently being absorbed by the plasticizing cylinder or is not currently required.

[0004] The object of the invention is to provide a generic forming machine in which the disadvantage discussed above does not occur.

[0005] This object is achieved by a forming machine having the features of claim 1 or claim 2. Advantageous embodiments of the invention are defined in the dependent claims.

[0006] The energy required for plasticizing the plastic granules is largely (approximately 75%) provided by the drive energy of the dosing motor, and only a small portion (approximately 25%) is provided by the heating energy provided by the temperature control device (for this purpose, the temperature control device can, for example, have heating bands). The invention offers several advantages over the prior art: - Fluctuations in torque can be recorded and taken into account - a higher dynamic of the process control is possible by intervening in the drive power - the back pressure can be taken into account, e.g. in the form of the back pressure curve over a dosing stroke (i.e. over the distance in which an axially movable screw moves away from the injection nozzle of the plasticising cylinder during the production of the melt from the plastic granulate due to the melt cushion forming at the screw tip) - Varying and therefore not readily known environmental influences such as moisture in the plastic granulate can be taken into account (these influences can be determined, for example, via the required torque) - the melt temperature in the screw antechamber can be measured

[0007] According to a first variant of the invention, the interaction of the individual models leads to an automatic optimization of the plasticizing process of the forming machine through optimally coordinated energy input sources (by balancing the energy input, optimizing / minimizing the losses - e.g. motor efficiency, thermal losses) and through an automatic adjustment of the parameters (speed, heating / cooling capacity, back pressure).

[0008] According to the invention, the energy-balancing model of the plasticizing process is composed of interconnected submodels, with one submodel being designed as a drive model describing the metering drive and one submodel being designed as a thermal model describing the thermal flows of the plasticizing cylinder. Furthermore, the energy-balancing model has a further submodel in the form of a process model describing the plasticizing process.

[0009] The process model sets the boundary conditions for subsequent optimizations. These can be divided into the following areas: Maximum permissible plasticizing time: • Determination of the maximum possible time for the plasticizing process from the cycle analysis

[0010] Material properties: • For example, an operator can select the plastic granulate used from a list. This way, the material properties are known and can be implemented in the process model. • The process model then contains the limit values ​​or optimal processing parameters depending on the material, such as maximum speeds, temperature ranges or profiles of the cylinder, etc., and also the material properties (enthalpy diagrams, compressibility, viscosity, etc.). The limit values ​​for the maximum permissible speeds also depend on added additives such as colorants, fibers, etc. • The energy introduced into the melt can be determined by measuring the melt temperature in the screw antechamber and determining the mass via the dosing stroke

[0011] The control device can be configured to operate the temperature control device for controlling the temperature of the different sections of the wall of the plasticizing cylinder and the cooling device for cooling the plastic granules in a coupled manner. In a minimal variant, the coupling can be implemented between the cooling device and the temperature control zone located adjacent to the cooling device. Thus, heating by this temperature control zone only occurs when higher temperatures are required, which reduces the energy consumption of the cooling device. This coupling can be taken into account in the thermal model.

[0012] The control device can be configured to deactivate the temperature control device in an axial region of the plasticizing cylinder depending on the position of the screw. For this purpose, the control device uses the position of the screw detected by a displacement sensor.

[0013] The control device can be configured to control the temperature control device and / or the dosing drive depending on an operating state (e.g., heating, automatic operation, interrupted automatic operation, manual operation, preheating state, etc.) of the forming machine. For example, it is not always necessary to continue operating the temperature control device during an interruption in the operation of the forming machine. However, it may be appropriate to maintain the temperature during short interruptions and to set a reduced temperature level during longer interruptions.

[0014] It can be provided that the control device is designed to control the tempering device and / or the dosing drive depending on the material properties of the supplied plastic granulate.

[0015] According to the second variant of the invention, only incorrect settings are reported without actively adjusting the parameters: For example, the control device can be configured to generate a user-visible message if the temperature difference between adjacent tempering zones reaches or exceeds a specified limit. If the temperature difference exceeds the limit, even though this is not caused by a difference in heating power between the adjacent tempering zones, a corresponding message can be useful, for example, to reduce an excessive screw speed.

[0016] Suggested changes to adjustable parameters such as speed, temperature, and / or back pressure are given to the operator. Parameter windows for permissible settings can also be displayed.

[0017] Particularly preferred examples of a molding machine according to the invention are an injection molding machine or an extruder for processing plastic.

[0018] Embodiments of the invention are discussed with reference to the figures. Fig. Figure 1 shows a schematic representation of an example of an energy-balancing model of the plasticizing process, which consists of a thermal model, a process model and a drive model, which are described in more detail below. Fig. Figure 2 shows the physical basis of the energy-balancing model of the plasticizing process, where the energy required for plasticizing is supplied via the tempering device (approx. 25% heating energy Q therm ) and the shearing caused by the rotation of the screw 22 (approx. 75% drive energy E diss ) is introduced into the plastic granulate to be plasticized.

[0019] The formula for the enthalpy change Δh of the plastic granulate or melt and thus the process model is: Δh=Ediss+Qtherm Q therm ... heating energy E diss ... dissipation energy Δh... Enthalpy change mc V ϑ0... Enthalpy Material

[0020] In order to obtain a further controllable intervention option in the energy balance of the plasticizing process, it is possible to install a controllable gravimetric dosing unit for the supplied mass m.

[0021] Fig. 3 shows an example of an injection unit of a molding machine according to the invention.

[0022] The heating energy Q His introduced into the plastic granulate or melt via individual tempering zones 40, 41, 42, 43 distributed along the plasticizing cylinder 21. The number of these tempering zones 40, 41, 42, 43 can be as large as desired. One or more temperature measuring devices 40a, 41a, 42a, 43a are provided to measure the temperature in the tempering zones 40, 41, 42, 43. The temperature measuring devices can be arranged in any position in front of, behind, or in the middle of the respective tempering zone 40, 41, 42, 43. The control of the tempering zones 40, 41, 42, 43 to the desired setpoint is carried out using a model-based approach based on a thermal model, which in turn is a sub-area of ​​the energy-balancing model of the plasticizing process. The melt temperature can also be measured directly, e.g., using an ultrasonic sensor, as described in DE 10 2015 010 589 of the applicant.

[0023] The thermal model is formed, for example, by the following formula: Qtherm=QH−QV−QK Q H ... heating energy Q V ... heat loss Q K ... cooling energy Q SK ... cooling energy snail

[0024] Optionally, a screw cooling system can be installed to keep the screw at a desired temperature.

[0025] To prevent the plastic granules from melting in the feed device (e.g., filling opening or hopper) and blocking it, it is often necessary to cool this area. For this purpose, the feed device can be designed as a cooling device for cooling the plastic granules. This, in turn, influences the material temperature, the temperature profile of the plasticizing cylinder, and thus also the plasticizing process. In this exemplary embodiment, cooling is achieved by means of a cooling jacket 32 ​​in which, for example, a cooling coil 32 through which water flows is located. The temperature in the area of ​​the filling opening is recorded by a sensor 31a. The control of the cooling is also a component of the energy balance-based model of the plasticizing process and is taken into account in the thermal model, thus minimizing energy losses during cooling.

[0026] However, the far greater energy input into the plastic granulate occurs via shear and thus via the drive energy E introduced by the screw A The drive energy is supplied to the screw by the metering drive 14. Additionally, the torque and speed of the metering drive 14 are recorded via measuring devices 14a. The supplied drive energy depends on the plastic granulate, the back pressure, the temperature of the plasticizing cylinder, the screw geometry, and the required speed or the desired metering time. Using a model-based approach and communication between the individual submodels, the supplied energy can be optimally controlled. A further submodel (drive model) is available for controlling the metering drive 14, which represents a subsection of the energy balance-based model of the plasticizing process.

[0027] The drive model is formed, for example, by the following formula: Ediss=EA(η) EA(η)=EAelec E diss ... dissipation energy E A ... drive energy E St ... dynamic pressure energy E Aelek ... electrical drive energy n ges ... overall drivetrain efficiency

[0028] The back pressure sets the counterforce for the plasticizing process. The back pressure is set and regulated via the injection block 15. The back pressure is measured in the pressure chamber 51 using a measuring device 15a. The back pressure energy is determined by the back pressure and the distance traveled by the screw during the plasticizing process. By changing the back pressure, the plasticizing process and the energy input of the metering drive can be influenced. This also makes it possible to regulate the back pressure depending on the screw position, which is recorded by position sensors 16, 16a.

[0029] The control system 60 contains the energy balance-based model of the plasticizing process. This includes a thermal model, a drive model, and a process model. These submodels influence each other through various parameters and are interconnected. Thus, a connection and interaction between these submodels also occurs in the control system 60. This interaction enables better process control, as all parameters can be optimally adjusted. By connecting these models, an energy-optimized plasticizing process is achieved.

[0030] Using the obtained limit values ​​or setting ranges of the parameters from the process model, the energy balance-based overall model now minimizes the losses of the energy input sources within the permissible setting ranges. List of reference symbols: 11 Carrier plate 12 cylinder plate 13 injection pistons 14 Dosing drive 14a Torque and speed measuring devices 15 Injection block pressure measuring device 15a Pressure measuring device 16 + 16a Position measuring device screw position 21 plasticizing cylinders 21a Outer wall of the plasticizing cylinder 21b Wall section of the plasticizing cylinder Wall section of the plasticizing cylinder 21c Inner wall of the plasticizing cylinder 22 snail 22a Snail vestibule 23 Nozzle 24 Melt temperature sensor 31 Cooling device 31a Temperature measuring device Cooling device 32 Cooling coil, through which a medium, e.g. water, flows 40, 41, 42, 43 Tempering zone consisting of heating bands 40a, 41a, 42a, 43a Temperature measuring devices 51 hydraulic pressure chamber for injection pressure and back pressure 52 hydraulic pressure chamber for screw retraction 60 Control device of the forming machine

Claims

[1] Forming machine with: a plasticizing unit, wherein the plasticizing unit comprises: - a feeding device for feeding a plastic granulate to a plasticizing cylinder (21) - a plasticizing cylinder (21) in which a screw (22) is rotatably arranged for plasticizing plastic granules - a dosing drive (14) for rotating the screw (22) - a tempering device for tempering a wall (21a, 21b) of the plasticizing cylinder (21), wherein the tempering device has at least two tempering zones (40, 41, 42, 43) for tempering different sections of the wall (21a, 21b) of the plasticizing cylinder (21) - a temperature measuring device (40a, 41a, 42a, 43a) for detecting a temperature of the plasticizing cylinder (21) and / or a melt produced from plasticized plastic granulate in the plasticizing cylinder (21) for the at least two tempering zones (40, 41, 42, 43) and / or for the screw antechamber - a measuring device (14a, 15a) for detecting a torque exerted on the screw (22) by the metering drive (14) and / or a rotational speed of the screw (22) and / or a back pressure exerted on the screw (22) by the melt and / or a metering stroke of the screw (22) and with a control device (60) which is connected to the dosing drive (14), the tempering device, the temperature measuring device (40a, 41a, 42a, 43a) and the measuring device (14a, 15a) characterized by , that the control device (60) is designed to control - the tempering device for tempering the different sections of the wall of the plasticising cylinder and / or - the dosing drive (14) depending on the - torque and / or speed and / or dynamic pressure and / or a metering stroke of the screw (22) detected by the measuring device (14a, 15a, 16a) and / or a temperature measured by the temperature measuring device (40a, 41a, 42a, 43a) using an energy-balancing model of the plasticizing process and that the energy-balancing model of the plasticizing process is composed of interconnected submodels, wherein one submodel is designed as a drive model describing the dosing drive, one submodel is designed as a thermal model describing the tempering device, and one submodel is designed as a process model describing the plasticizing process of the plastic granulate. [2] Forming machine with: a plasticizing unit, wherein the plasticizing unit comprises: - a feeding device for feeding a plastic granulate to a plasticizing cylinder (21) - a plasticizing cylinder (21) in which a screw (22) is rotatably arranged for plasticizing plastic granules - a dosing drive (14) for rotating the screw (22) - a tempering device for tempering a wall (21a, 21b) of the plasticizing cylinder (21), wherein the tempering device has at least two tempering zones (40, 41, 42, 43) for tempering different sections of the wall (21a, 21b) of the plasticizing cylinder (21) - a temperature measuring device (40a, 41a, 42a, 43a) for detecting a temperature of the plasticizing cylinder (21) and / or a melt produced from plasticized plastic granulate in the plasticizing cylinder (21) for the at least two tempering zones (40, 41, 42, 43) and / or for the screw antechamber - a measuring device (14a, 15a) for detecting a torque exerted on the screw (22) by the metering drive (14) and / or a rotational speed of the screw (22) and / or a back pressure exerted on the screw (22) by the melt and / or a metering stroke of the screw (22) and with a control device (60) which is connected to the dosing drive (14), the tempering device, the temperature measuring device (40a, 41a, 42a, 43a) and the measuring device (14a, 15a) characterized by , that the control device (60) is designed to, with respect to - the tempering device for tempering the different sections of the wall of the plasticising cylinder and / or - the dosing drive (14) depending on the - torque and / or speed and / or dynamic pressure and / or a metering stroke of the screw (22) detected by the measuring device (14a, 15a) and / or a temperature measured by the temperature measuring device (40a, 41a, 42a, 43a) using an energy-balancing model of the plasticizing process to detect incorrect settings and preferably to issue a message and that the energy-balancing model of the plasticizing process is composed of interconnected submodels, wherein one submodel is designed as a drive model describing the dosing drive, one submodel is designed as a thermal model describing the tempering device, and one submodel is designed as a process model describing the plasticizing process of the plastic granulate. [3] Molding machine according to claim 1 or 2, wherein the feeding device comprises a cooling device (31) for cooling the plastic granulate. [4] Shaping machine according to the preceding claim, wherein the control device (60) is designed to operate the tempering device for tempering the different sections of the wall (21a, 21b) of the plasticizing cylinder (21) and the cooling device (31) for cooling the plastic granulate in a coupled manner. [5] Shaping machine according to at least one of the preceding claims, wherein the control device (60) is designed to switch off the tempering device in an axial region of the plasticizing cylinder (21) depending on a position of the screw (22). [6] Shaping machine according to at least one of the preceding claims, wherein the control device (60) is designed to control the tempering device and / or the dosing drive (14) depending on an operating state of the shaping machine. [7] Shaping machine according to at least one of the preceding claims, wherein the control device (60) is designed to control the tempering device and / or the dosing drive (14) depending on material properties of the supplied plastic granulate. [8] Shaping machine according to at least one of the preceding claims, wherein the control device (60) is designed to generate a message visible to a user if the temperature difference between adjacent tempering zones (40, 41, 42, 43) reaches or exceeds a predetermined limit value. [9] Shaping machine according to at least one of the preceding claims, wherein the control device (60) is designed to estimate, using an observer, whether a temperature profile desired by a user can be achieved with the current actuators of the shaping machine. [10] Shaping machine according to at least one of the preceding claims, wherein the control device (60) is designed to control a back pressure depending on a position of the screw (22), preferably in the form of a back pressure curve over a metering stroke of the screw (22).

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