AT504927A1 - DEFICIENCY DETECTION IN AN INJECTION MOLDING MACHINE - Google Patents

Description

1

The present invention relates to a method for driving a movable part of or for an injection molding machine.

Working with injection molding machines inevitably involves the need to drive movable parts of an injection molding machine or for an injection molding machine, that is, to accelerate or decelerate. Surprisingly, this has hitherto done without taking into account the fact that the inertia of the parts to be moved, that is, the resistance to which the parts oppose a change in their state of motion, may differ from time to time.

For example, in the course of an injection molding process usually a movable platen translationally on a fixed platen back and move away from this. In this case, the inertia (mass) of the movable platen differs depending on which mass has attached to the movable platen half mold.

There are also injection molding machines are known in which turntables with built tools translationally reciprocated and rotated. The turning takes place in most cases between two mechanical stops. This means that the exact position is not guaranteed by the drive of the turntable, but that the drive applies a certain force to the respective stop and thus holds the turntable in this position when closing the injection molding machine.

The factory default setting of the control of the turntable with fixed acceleration or braking ramps. These preset ramps are set when the turntable is empty or when a test block is set up.

Now uses the user a tool with a different moment of inertia than in the factory setting was established, it comes to a premature or delayed concerns (attacks) to the respective mechanical stop.

In the case of premature striking, it may lead to a deformation of the stop up to a permanent deformation. If the moment of inertia is lower than in the factory setting, the stop is approached at a very slow speed, which increases the cycle time of the injection molding process. 58733 - 36 / fr ···· ···· ····· * ····················································································· ··· · · · · · · · · · · · · · · · · · · 2

The same applies of course to the translatory movement.

Another example relates to handling parts used in handling, such as highly dynamic linear gantry robots. In these, it is necessary to comply with certain limits for speeds, accelerations and / or jerks due to the weight-saving and partially cantilevered construction and the tendency to oscillate.

In order not to prescribe overly conservative limits in areas in which the components are already subjected to less stress anyway, a method which reduces the speeds, accelerations and / or jerks substantially dependent on the start and target positions already exists in the prior art. This adjusts the limits of vibration tendency. However, this is based on a fixed (generally the maximum permissible) payload.

The object of the invention is to develop a generic method such that a more economical driving is made possible.

This object is achieved by a method having the features of claim 1.

Thus, in the example discussed, the movable platen determines the translational movement of the platen as a function of the actual total mass (mold platen and mold half).

In the example of the turntable discussed, the acceleration and braking ramps for the rotational or translational movement can be adapted to the respective actual moment of inertia or to the mass of the turntable together with the tool set up.

With regard to the discussed example from the handling area, the current load conditions can be taken into account. The handling parts can thus be controlled to their mechanical performance limits without the risk of being overloaded by certain applications.

More generally, in the present disclosure, the term "driving" may mean both deceleration and acceleration. Direct Determination of Inertia * ♦ ····· ···················································································· · ············ · 3 is a numerical determination of the value of inertia. Indirect determination of inertia numerically determines the value of such physical quantities (one or more) that vary depending on the actual inertia present. In these cases, the value of inertia itself is unknown.

If the driving of the movable part takes place translationally, at least over a distance section, its mass is to be determined as the inertia of the movable part.

If it comes to driving the movable part by rotation about an axis of rotation, the inertia in the form of the moment of inertia of the movable part with respect to the axis of rotation is to be determined.

In a combination of translation and rotation, it may be necessary to determine both mass and moment of inertia (ie, total inertia or generalized mass).

In itself, there are various ways to determine the inertia of the movable part directly or indirectly. On the one hand, it is possible to determine the inertia of the movable part from movement quantities and / or driving variables (for example force). The distance covered or the distance to be traveled, the speed, the acceleration, the jerk or the quantities derived therefrom can be used in isolation or in combination with each other.

It is also conceivable to determine the inertia of the movable part from operating variables of the drive unit driving the movable part. Depending on the type of drive unit, this may be the motor current, the hydraulic pressure, the speed or the like.

The determination of the inertia of the movable part can be carried out in each case by means of separate movements before driving. It is also possible to determine the inertia of the movable part during driving, for example at the beginning of the driving.

For example, in a turntable in Einrichtbetrieb by measuring the hydraulic pressure on the hydraulic motor or the current of a servomotor in the acceleration phases to a determination of the moment of inertia of the turntable including built-tool or at known moment of inertia of the turntable of • • • · ·· ··· · 4 separate moment of inertia of the built-up tool. Accordingly, the acceleration and deceleration ramps can be set steeper or flatter.

In particular, but not exclusively, with respect to this example, a particularly simple design provides (especially for electrically driven turntables) to determine the time or path for the actual acceleration operation. This is an example of indirect determination of the inertia of the movable part. Under an approximate neglect of the friction, the same time or the same way as for the acceleration is required for the braking operation. Thus, the timely and optimal timing of the initiation of the braking process can be determined. This results in the optimal slope of the ramps, so to speak automatically. The maximum possible slope can of course be limited.

Regardless of the way in which the inertia of the movable part is determined, it can be provided that, depending on the determined inertia, preferably continuously, parameters for a control or regulating device of the drive unit are determined. These or additionally determined parameters can be used to set desired movements of the travel and / or the speed and / or the acceleration of the movable part. These nominal curves can be used by the control device for controlling the movement of the movable part.

Various methods for determining the inertia of the movable parts are of course known to the person skilled in the art and therefore do not need to be explained in detail. In particular, algorithms for the electronic determination of the inertia as a function of measuring signals already belong to the prior art and can also be used in the present invention. Such algorithms can be found, for example, in the textbook "Applied Nonlinear Control, J.-J. Slotine, Prentice Hall (1991).

Further advantages and details of the invention will become apparent from the figures and the associated description of the figures. Showing:

Fig. 1 is a side view of an injection molding machine with as movable

Platen and turntable formed movable parts,

Fig. 2 shows a handling part for an injection molding machine in the form of a gantry robot and

Fig. 3 shows an embodiment of the method according to the invention. ·· ···· · ···· ·· · · · · · • · • · • · • · · # "··" * • · ♦ • · · 5

1 shows a known barless injection molding machine 13 with a fixed platen 2 and a movable platen 1 and with an injection unit 8 for introducing plastic into a mold cavity, which by a fixed platen 2 fixed to the mold half 4 and one of two on the movable platen 1 by means of a parallel to the platens 1, 2 pivotable rotary table 3 mounted mold halves 5, 5 'is formed. The movable platen 1 is horizontally displaceable on a frame 6.

The turntable 3 is formed pivotable by means of a motor 10. The pivot axis 11 extends at the upper edge of the movable platen 1. To the motor 10, a resolver 12 for measuring movement amounts of the turntable 3, such as the angle of rotation, the angular velocity, the angular acceleration, etc. connected.

Both the movable platen 1 and the turntable 3 are examples of movable parts, which can be driven by the method according to the invention.

FIG. 2 shows a perspective view of a portal robot 14 known per se, which can be used for handling in conjunction with an injection molding machine 13. The gantry robot 14 is arranged so that it can move along three axes X, V, Z. The gantry robot 14 represents an example of a movable part for an injection molding machine 13, which can be driven by the method according to the invention.

Fig. 3 shows a simple embodiment of the method according to the invention. Shown on the abscissa are the elapsed time t and on the ordinate either the speed v (if the movable part is a movable platen 1) or the rotational speed n (if the movable part is a turntable 3).

The solid curve 15 represents the speed v or the rotational speed n as a function of the time t in the event that the movable platen 1 or the turntable 3 is moved with known inertia. In other words, in the solid curve 15 only mold halves of known mass on the movable platen 1 and tools 5, 5 'with known mass on the turntable 3 are arranged. • · · · · · · · · · · · · · · · · · ···

The dashed line 16 shows the situation in the case where the mold halves mounted on the movable platen 1 and the tools 5, 5 'mounted on the turntable 3 have a lower mass than in the case of the solid curve 15. In this case, the target speed becomes or reaches the target speed at an earlier time. This is registered by a control device and not shown, and the movable part can be moved for a longer period with the target speed and the target speed before one of the illustrated acceleration ramp corresponding deceleration ramp must be driven.

Exactly opposite is the situation for the case of the dashed curve 17. In this case, the inertia of the movable part is greater than in the case of the solid curve 15. Therefore, more time is needed to get to the target speed and the target speed. This is registered by a control device, not shown, which therefore begins earlier than in the case of the solid curve 15 with the initiation of the braking ramp for the movable part.

Innsbruck, March 1, 2007

Claims (12)

················ ······ 1. A method for driving a movable part of or for an injection molding machine, characterized in that the inertia of the movable part is determined directly or indirectly and driving the movable member in response to the detected inertia. 2. The method according to claim 1, characterized in that the driving of the movable part takes place translationally at least over a distance section and the mass of the movable part is determined. 3. The method according to claim 1 or 2, characterized in that the movable part is rotated about an axis of rotation and the moment of inertia of the movable part is determined with respect to the axis of rotation. 4. The method according to any one of claims 1 to 3, characterized in that the inertia of the movable part of motion variables - such as covered path, speed, acceleration or jerk or derived variables, and / or driving variables, isolated or in combination - is determined , 5. The method according to any one of claims 1 to 4, characterized in that the inertia of the movable part of operating variables or nominal variables of the movable part driving drive unit - such as motor current, hydraulic pressure, speed or the like - is determined. 6. The method according to any one of claims 1 to 5, characterized in that the determination of the inertia of the movable part takes place during - preferably at the beginning of - the driving. 7. The method according to any one of claims 1 to 5, characterized in that the determination of the inertia of the movable part takes place by means of separate movements of the movable part before driving. 8. The method according to any one of claims 1 to 7, characterized in that, depending on the determined inertia, preferably continuously, parameters for a control or regulating device of the drive unit are determined. 58733 - 36 / fr ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 9. The method according to any one of claims 1 to 7, characterized in that determined in dependence on the determined inertia nominal curves for the path and / or the speed and / or acceleration of the movable part and a control or regulating device of the drive unit , 10. The method according to any one of claims 1 to 9, characterized in that as a movable part, a turntable (3) or parts of the closing unit of the injection molding machine (13), preferably the movable platen (1) are driven. 11. The method according to any one of claims 1 to 9, characterized in that as a movable part, a handling part, preferably a gantry robot (14), for an injection molding machine (13) is driven. 12. control or regulating device for an injection molding machine, characterized in that it is designed for carrying out a method according to one of claims 1 to 11. Innsbruck, March 1, 2007