METHOD FOR CONTROLLING A MACHINE FOR PROCESSING PLASTICS

Abstract

The invention relates to a method that serves to control a machine (10) for processing plastics and other plasticisable materials such as powdered and/or ceramic substances. The machine has a mould opening and closing unit (12) for opening and closing an injection mould (14) having at least one mould cavity (16) for producing an injection moulded part (18) corresponding to the shape of the mould cavity (16), an injection moulding unit (20) having means for plasticising and for injection of the plasticisable material in the mould cavity (16) and has a machine control (22) which is connected to an expert knowledge source (34) and if required can be operated by the operator by means of an interactive contact. Information concerning the geometry of the injection moulded part (18) and/or the mould cavity (16) and the sprue geometry (24) are provided to the machine control (22), in order to calculate at least one injection process taking the geometric information into consideration. Because an injection process is calculated, taking into consideration the geometric information, at least one progressive volume growth profile of the injection moulded part (18) in the filling direction of the mould cavity (16) is calculated, and taking into consideration the progressive volume growth profile at least one injection process is calculated, a simplified, fast and effective parameterisation of the injection moulding machine is made possible, the operator is relieved by the implemented expert knowledge and the quality of the injection moulded part (18) is improved.

Claims

1.-10. (canceled)

11. A method for controlling a machine for processing plastics and other plasticisable materials, wherein the machine comprises a mold opening and closing unit configured for opening and closing an injection mold comprising at least one mold cavity configured for manufacturing a molding that corresponds to the shape of the at least one mold cavity, an injection molding unit configured for plasticising and for injecting a plasticisable material into the at least one mold cavity, a machine controller that is in communication with an expert knowledge and is configurable to be interactively influenced by an operating person, wherein the method comprises the steps of: providing geometric information, on at least one of the geometry of the molding or the geometry of the mold cavity that receives the molding, to the machine controller, providing information on the sprue geometry to the machine controller, calculating at least one step-by-step volume growth profile of the molding in the direction of filling the mold cavity, taking into account the geometric information, wherein the volume growth profile of the molding is calculated layer by layer, beginning from at least one sprue point, wherein a particular distance covered by a conveying device, or a particular volume, is associated with each layer, wherein the calculation of the at least one step-by-step volume growth profile of the molding is performed before a first injection procedure for manufacture of a molding is carried out, wherein the volume growth profile is calculated taking into account at least one of the items of information in respect of the total injection volume or the thickest and thinnest wall thickness of the molding or the wall thickness ratios or flow path ratios, and wherein at least one injection procedure is calculated, taking into account the step-by-step volume growth profile and on an assumption of a material front that flows at constant speed.

12. A method according to claim 11, wherein the at least one of the items of information is to be found in the expert knowledge.

13. A method according to claim 11, wherein the calculation of the volume growth profile is carried out with the same volume step each time.

14. A method according to claim 11, wherein for calculating the volume growth profile, information from the expert knowledge is categorized into classes and distinguishable by at least one of the following criteria: mold classes for injection molds, filling time classes during the injection procedure for manufacturing the molding, flow path/wall thickness ratios in the molding, material classes, holding pressures in relation to minimum and maximum wall thicknesses in the molding, wherein a classifier classifies the molding on the basis of these criteria in order to make information from the expert knowledge accessible for the purpose of calculation.

15. A method according to claim 14, wherein the classifier classifies the molding interactively with an operating person.

16. A method according to claim 11, wherein the volume growth profile is calculated by at least one integration method.

17. A method according to claim 11, comprising at least one of the steps of: displaying the geometric data at a display/operating device, identifying at least one sprue point in relation to an axis of injection, identifying mold characteristics.

18. A method according to claim 17, wherein the identifying at least one sprue point in relation to an axis of injection is conducted with reference to a display.

19. A method according to claim 11, wherein material information on the material to be processed is provided to the machine controller as a further information, at least one of predetermined by the operating person or selected as information from the expert knowledge, and is used for standardizing the volume growth profile, and wherein the at least one injection procedure is calculated taking into account the material information.

20. A method according to claim 11, wherein at least one setpoint parameterization for an injection curve is determined on the assumption of a material front that flows at a flow front speed that is as constant as possible.

21. A method according to claim 20, wherein the at least one setpoint parameterization is determined on the assumption of the material front flowing at a constant volume growth rate.

22. A method according to claim 11, wherein a setpoint parameterization for an injection curve is adapted to parameters delimiting the injection molding unit.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0034] The disclosure is explained in more detail below with reference to an exemplary embodiment represented in the attached Figures, in which:

[0035] FIG. 1 shows a schematic illustration of an injection molding machine and associated machine controller with a display/operating device,

[0036] FIG. 2 shows a flow chart for control and parameterization of the machine,

[0037] FIG. 3a shows a schematic illustration of a molding, with sprue,

[0038] FIG. 3b shows a schematic illustration of a molding, with sprue, and

[0039] FIG. 4 shows the display/operating device with volume growth profile and parameter input.

DETAILED DESCRIPTION

[0040] The disclosure is now explained in more detail by way of example, with reference to the attached drawings. However, the exemplary embodiments are only examples, which are not intended to restrict the inventive concept to a particular arrangement. Before the disclosure is described in detail it should be pointed out that it is not restricted to the respective structural parts of the device and the respective method steps, since these structural parts and methods may vary. The terms used here are merely intended to describe particular embodiments and are not used restrictively. Moreover, where the singular or the indefinite article is used in the description or the claims, this also refers to a plurality of these elements unless the overall context unambiguously indicates otherwise.

[0041] In the context of the disclosure, the following definitions are used: [0042] A volume growth profile describes the increase in volume over time or over the path of a conveying device. [0043] An injection procedure is the procedure required for manufacture of a particular molding of which the geometric data form the basis for calculating the volume growth profile. [0044] A parameterized injection curve is an injection procedure that is determined by parameters calculated using the method and that makes it possible to manufacture the particular molding on the respective injection molding machine, using the machine controller.

[0045] FIG. 1 shows a schematic illustration of a machine 10 for processing plastics and other plasticisable materials such as ceramic or powder materials. The machine 10 has a mold opening and closing unit 12, for opening and closing an injection mold 14 having at least one mold cavity 16 for manufacturing a molding 18 that corresponds to the shape of the mold cavity 16, and an injection molding unit 20. In FIG. 1, the injection mold 14 is shown open, and the molding 18 has been ejected from the mold cavity 16, where appropriate with its sprue 26. Plasticisable material is supplied to the mold cavity 16 by way of a sprue geometry 24. Any peripherals 32, such as cooling devices or removal devices, are connected to the machine 10 and/or the machine controller 22.

[0046] Associated with the machine 10 is a machine controller 22 that is in communication by way of networks, for example, with an expert knowledge unit 34 in the form of for example databases.

[0047] The expert knowledge unit 34 comprises for example data in relation to materials to be processed, such as the specific density of the solid and fluid material, the melting point, the flow index, the maximum shear rate and/or in general the pressure/temperature behavior as the materials cool from fluid to solid, data in relation to injection molding knowledge on characteristic process sequences, such as data for the filling time for particular classes of mold, in conjunction with flow path/wall thickness ratios in the molding, coupled with particular classes of mold, and holding pressures in relation to minimum and maximum wall thicknesses of the molding and/or data on the static and dynamic properties of the kinematics of the machine. In principle, however, there may also be other data in the expert knowledge unit 34, which may serve to describe an injection molding procedure, the associated equipment and/or materials. In principle, it is also conceivable for the expert knowledge unit 34 to be in the machine controller 22 itself.

[0048] For interactive contact between the machine controller 22 and the operating person, a display/operating device 28 is provided, which takes the form for example of a screen with keyboard, a (multi-)touch screen or indeed other suitable devices such as voice input.

[0049] FIG. 2 shows the sequence of the method. At the start of the method, in step 110, the machine controller 22 receives information on the geometry of the molding 18 and its arrangement, as the mold cavity 16 in the mold and the sprue geometry 24. The geometric data may come from the most diverse sources, for example a CAD program or a 3D scan of a 3D prototype printed beforehand, for example. In principle, it is also conceivable for the expert knowledge unit 34 already to contain geometric data and/or for these to be stored or storable there.

[0050] Preferably, in a further exemplary embodiment, in step 110 material data on the material to be processed are provided, which the operating person for example predetermines or selects from the expert knowledge unit 34. For example, a material class or the exact material are selected from a material database of the expert knowledge unit 34. The machine controller 22 uses this and machine component data, such as the installed injection and plasticising module/screw, any plasticization models available for this purpose for different screw geometries, and any data on the peripherals 32, to calculate adjustment values for the machine 10, such as the screw speed, back pressure and temperature adjustment for the cylinder heating and mold temperature control.

[0051] Preferably, in step 120 the geometric data of the molding 18 are displayed at the display/operating device 28. This allows the operating person to identify, simply and intuitively, at least one sprue point in relation to the axis of injection. In principle, it is also conceivable for the machine controller 22 to calculate a suggestion for the sprue point, for example on the basis of knowledge of the geometric relationship between the cavity system and the mold. Further interactive operations by the operating person are preferably identifying mold characteristics, such as whether the mold is a multiple-cavity mold with a hot-runner system or a mold with multiple sprues. Depending on the case, the method first considers only one cavity and thereafter calculates the number of further cavities, by simple adding up or by an offset. In the case of multiple sprues, each individual sprue point is considered separately and added on until a contiguous volume composed of the different sprue points is reached. As soon as the material fronts are in contact, further consideration is carried out as though there were only one sprue point. In respect of any dynamic pressure losses, a cross sectional area is for example added.

[0052] The volume growth profile is calculated in step 130. FIGS. 3a and 3b schematically show geometries of moldings 18. With the aid of the geometric data of the molding 18, the volume growth profile is calculated layer by layer, beginning at a sprue point. The geometry of the molding 18 is built up layer by layer, or step by step. For example, in FIG. 3a the volume of the molding 18 is built up, beginning at the sprue point, in layers 36 until it reaches the base of the molding. Then build-up continues radially in relation to the sprue point 26. In FIG. 3b, beginning at the sprue point 26, both sidesto left and right of the sprue point 26are built up evenly.

[0053] It has shown to be advantageous to perform the calculation of the step-by-step volume growth profile of the molding before a first injection procedure for manufacture of a molding is carried out. As a result, possible sources of error can be reliably eliminated at the start of the injection procedure, and the molding proving procedure can be further shortened. At the same time, the expert knowledge required for operating the machine can be reduced to an even greater extent.

[0054] Preferably, the layer-by-layer calculation of the volume growth profile is carried out in each case with the same volume step 30, according to FIGS. 3a and 3b.

[0055] Further preferably, the volume growth profile is calculated by at least one integration method, for example by a numerical integration method such as the trapezoidal rule.

[0056] To generate the volume growth profile, there can be used information comprising the total injection volume or the thickest and thinnest wall thicknesses of the molding or the wall thickness ratios or flow path ratios, wherein this information is preferably to be found in the expert knowledge unit.

[0057] In order to make calculation of the volume growth profile reproducible and where appropriate to make it faster, it is possible to utilize a classifier, which uses and classifies information from the expert knowledge unit and/or information predetermined by the operating person. This information may be categorized into classes and distinguished, for example by at least one of the following criteria: [0058] Mold classes for injection molds, [0059] filling time classes, during the injection procedure for manufacturing the molding 18, [0060] flow path/wall thickness ratios in the molding 18, [0061] material classes, [0062] holding pressures in relation to minimum and maximum wall thicknesses in the molding 18.

[0063] The classifier, preferably interactively with an operating person, classifies the molding 18 on the basis of these criteria in order to make relevant information from the expert knowledge unit accessible for the purpose of calculation.

[0064] To mention only a few non-restrictive examples, it is thus possible for selection classes to be for example different wall thickness flow ratios of for example more than 200, or maximum filling times of for example less than 0.2 s.

[0065] In step 140, on the assumption of a material front that flows at constant speed, preferably at least one injection procedure is calculated.

[0066] Preferably, the volume growth profile of the molding 18 is calculated layer by layer, preferably beginning from at least one sprue point, wherein a particular distance s covered by a conveying device such as a conveying screw, or a particular volume V, is associated with each layer 36.

[0067] In a further preferred exemplary embodiment, in step 150 the injection procedure is adapted by parameters 42 delimiting the injection molding unit 20, such as maximum speeds and/or accelerations at which the machine 10 can be operated so that the machine 10 is not overdriven. Further, the minimum/maximum desired filling time is adapted using for example a quadratic or sinusoidal interpolation of the speed values possible for the machine, for example by a recursive method. The parameters 42 can be adapted, for example according to FIG. 4, by the operating person at the display/operating device 28.

[0068] In principle, interactive control with an operating person is always advantageous, since in that case the system can prompt the person operating it for further input, or also inform them of the results obtained, if there are for example malfunctions, if information is missing, or even if the result is that a volume growth profile of this kind is not performable, or not performable in that way, on the machine in question. Likewise, the operating person can intervene in a targeted manner, for example to identify a sprue point or direction of flow.

[0069] It is self-evident that this description can be subject to a great variety of modifications, amendments and adaptations, which belong within the scope of equivalents to the accompanying claims.