DE102014011335A1 - Shaping machine with negative mold protection - Google Patents

Abstract

Shaping machine, in particular injection molding machine, with a first machine part, a second, relative to the first machine part movable machine part, a drive unit for moving the second movable machine part between an activity position and a retracted position and a control or regulating device (5) for controlling or regulating the drive unit (4), wherein in the control or regulating device (5) _(to P) at least one setpoint value profile of a parameter (P) of the drive unit (4) is deposited, and with an actual value (P _ist) of the same parameter (P) of the drive unit (4 ), characterized in that the desired value curve (P _soll ) corresponds to a parameter (P) during a return movement of the second machine part from the activity position to the retracted position and by the control or regulating device (5), the return movement of the second machine part at one of desired value progression (P _soll) by more than a settable n deviation value (A) deviating actual value P _is ) is sustainable.

Description

The invention relates to a molding machine, in particular injection molding machine, with a first machine part, a second, relative to the first machine part movable machine part, a drive unit for moving the second movable machine part between an activity position and a retracted position and a control or regulating device for controlling or regulating the Drive unit, wherein in the control or regulating device at least one desired value course of a parameter of the drive unit is stored and is comparable to an actual value of the same parameter of the drive unit.

In forming machines, there are a variety of machine parts that perform relative to each other movements. These often have an activity position that directly fulfills the actual purpose of the respective machine part for the entire shaping machine. In a core pull, this is, for example, the retracted position of the core pull in the tool, in which the core pull forms part of the cavity in the tool. In an ejector, this is, for example, the ejection position in which the molded part produced is ejected. These activity movements of the movable machine parts usually run very precisely controlled.

Another example of such parts of forming machines are the mold platens, wherein the fixed platen forms the first machine part, the movable platen forms the second machine part and the activity position of a closed position (injection and holding active) corresponds to the mold platens and the tool.

In the following, the problem of the prior art with respect to this third example (closing unit) will now be described, the same disadvantages apply mutatis mutandis to core pullers, ejector or the like and are to be understood accordingly.

Closing units for molding machines (injection molding machines, transfer molding presses or the like) generate in the closing movement a recorded in data sheets or the name of the machine corresponding closing force. A closing force deviation is precisely defined. For the injection process, it must be guaranteed by the closing unit or closing side that the set value is actually reached in order to obtain a cleanly shaped molded part, in particular a plastic part. For this purpose, the closing force is monitored with a variety of sensors, these sensors and the monitoring is designed depending on the locking system used.

Furthermore, the same sensor technology or a separate sensor system for the so-called shape protection is used to make the system sensitive when closing. That is, in the movement of the platen a possibly occurring obstacle should be detected as quickly as possible to immediately slow down the drive, stop and / or shut down completely.

An example of such a protection method comes from the EP 0 096 183 B1 out. In this case, the pressure curve is monitored during the closing process, wherein the closing operation is always stopped when the hydraulic pressure in the pressure curve is above the measured normal value by a predetermined amount.

A similar method for monitoring an injection process in an injection molding machine is from the AT 004 744 U1 known. In this case, the position or the speed of the injection piston or the injection screw or the pressure in the plastic is constantly monitored and triggered when exceeding a predetermined deviation from the normal value, a reaction.

Another similar procedure comes from the EP 1 343 621 B1 at least one relevant process parameter and a possible quantity error of the melt in the mold cavity is corrected by influencing the flow conditions at the end of the injection phase or in the first section of the embossing phase at still liquid melt. It is also stated that full speed control is possible for the entire cycle. It is written in it but only generally by a mold opening speed and no further details are given.

Basically, the currently known security systems for the closing movement (form protection) are already quite good. After the injection process, however, the mold is still open and the part removed from the mold. The necessary forces or the resulting forces in the tool can be very different. This also depends on the locking system or the tool design. No special value is specified or standardized for the opening or tearing forces involved. This can lead to the fact that in the case of operating cases in which abruptly high forces are built up during the opening movement (if, for example, the slide remains hanging), in the worst case the tool breaks off from the mold clamping plate. Such a high tearing force can occur especially when too much was injected. Especially with electrically driven toggle locking units accelerated when the server engine accelerates to relieve the toggle. When the plate movement then starts the engine is already at a high speed and does not recognize an opening resistance or not in time.

The object of the present invention is to provide a comparison with the prior art improved molding machine, in particular clamping unit, core puller or ejector. In particular, the safety of the system should be ensured during an entire cycle.

This is achieved by a shaping machine having the features of claim 1. Accordingly, it is provided that the desired value curve corresponds to a parameter in a retraction movement of the second, movable machine part from the activity position to the retracted position and by the control or regulating device the retraction movement of the second, movable machine part at an actual value deviating from the desired value by more than an adjustable deviation value is persistent. Thus, the basic idea of the invention resides in the fact that, for example, in the case of closing units, there is also an adjustable form protection during opening.

In the following, the advantages of the present invention with regard to a closing unit are explained, wherein the same advantages or variants are to be understood mutatis mutandis for core pullers, ejector or the like.

Especially in the case of very rigid tools, the locking stroke is low in a toggle-type machine. That is, when opening still acts at the time of tearing a very high leverage. In extreme cases, the opening force at the point of mold separation can reach more than 50% of the closing force. This can have negative effects on the machine, break tool mounting screws, break the lever attachment, or break the slanted bolts for the slides in the tool. This can be prevented by the present invention. Another advantage of the negative form protection is the increased safety when using magnetic platens, which currently have to be monitored with elaborate own proximity limit switches. The negative mold protection can also be used for process monitoring, as it can lead to increased tearing forces when overmoulded (depending on the shape design). Even with parts that are difficult to demold, the negative form protection can be used as an additional parameter for process monitoring.

In general, the parameter of the drive unit can be either pressure, torque, force and / or speed. Preferably, it is also provided that the parameter or parameters can be detected by at least one sensor. The sensors, preferably in the form of highly sensitive piezoelectric sensors, can also provide a negative value in the control and limit the forces over a certain path when opening as when closing (closing). The form protection path when closing is normally only as long as the component thickness until shortly before the plate installation (0.1 to 0.2 mm). When opening this shape protection path of plate system is adjustable up to 5 mm opening. It should generally correspond to the slide actuation path. However, the monitoring need not be based on such sensors, but may also be integrated into the control itself or carried out via a pressure relief valve.

An advantage of the opening movement monitoring is also that changes in the lubrication conditions in the tool or in the slide are detected. For stacking tools, the sequence of opening the different parting planes could be monitored. An economic advantage lies in the fact that in most machines a sensor for the general form protection already exists and therefore there would be no additional costs. It is only the application software (control or regulating device) to expand accordingly.

In principle, the deviation value can be entered manually, read in by machine or calculated. It is preferably provided that the adjustable deviation value for the parameter of the drive unit is stored in the control or regulating device. It is particularly preferred that the deviation value of the parameter deviates from the desired value curve by a maximum of 15%, preferably a maximum of 10%. Of course, this deviation value can also be dependent on the opening travel (retraction path) and, depending on the position, vary along the opening travel.

If a pressure or a force is monitored as a parameter, the sequence in the control or regulating device may be as follows: The mold is opened with a predetermined velocity profile, wherein the force in the rapid traverse cylinder during the opening phase between two positions compared to a previously determined monitoring curve (setpoint curve) is monitored. If the actual value of the force exceeds the monitoring curve by an adjustable tolerance (deviation value), an error is output and the opening movement is aborted.

If the negative shape protection is monitored by velocity, this can be done as follows: The shape is opened with a given velocity profile, whereby the velocity during the opening phase is monitored between two positions with respect to a previously determined reference curve (setpoint curve). When driving with increased power demand, the speed changes. If the reference curve is undershot, an error is output and the opening movement is aborted. For the speed measurement, a smoothing constant can exist. An additional parameter is used to set the minimum speed to be monitored during initialization. At the same time, the minimum speed limits the monitoring curve downwards.

To have not only the particular advantages of the invention when opening the mold platens, of course, can also be provided that in the control and regulating device also a setpoint course for a closing movement (activity movement) is deposited, wherein the control or regulating device, the closing movement of the movable mold clamping plate (second machine part) at a one of the setpoint value by more than an adjustable deviation deviating actual value is sustainable.

When the invention is applied to a core pull, it is preferably provided that the first machine part is a cylinder of a core pull and the second machine part is a piston of a core pull, wherein the active position is the position of the core pull retracted into a tool and the return movement is the return of the core pull equivalent.

Alternatively, if the invention is used with the aid of an ejector, it is preferably provided that the first machine part is an ejector ram of an ejector and the second machine part is an ejector guide of an ejector, wherein the activity position is the ejection position of the ejector and the retraction movement corresponds to the retraction of the ejector.

In general, the drive unit can be based on a hydraulic system. For more precise movement possibilities, however, it is preferably provided that the drive unit has at least one electric motor.

Further details and advantages of the present invention will be explained in more detail below with reference to the description of the figures with reference to the exemplary embodiments illustrated in the drawings. Show:

1 schematically an injection molding machine,

2 a schematic setpoint curve with deviations and

3 a value course when hitting an obstacle.

For the description of the figures also applies again that the invention is explained with reference to the closing unit of a forming machine, wherein all features, advantages and movement information mutatis mutandis apply to the other embodiments (core pull, ejector) of the invention.

In 1 is generally and schematically a closing unit 1 a molding machine, in particular an injection molding machine shown. It is on the frame 7 a fixed platen 2 (first machine part) attached. Also the front plate 9 is with the frame 7 firmly connected. In between is a movable platen 3 (second, movable machine part) on the frame 7 movably mounted, this movement via an only schematically indicated drive unit 4 (For example, a motor-driven toggle lever system) takes place. At the mold clamping plates 2 and 3 are the mold halves 8th , which together form the tool, fastened or clamped. In the 1 are the mold clamping plates 2 and 3 in the closed position SS (activity position). About the drive unit 4 becomes the movable platen 3 between the closed position SS and an open position OS (retraction position) reciprocated. The closing movement S (activity movement) and the opening movement Ö (withdrawal movement) are illustrated by the arrows. Schematically is further the control or regulating device 5 represented, in the at least one setpoint course P _{soll of} a parameter P of the drive unit 4 is deposited. For this setpoint course P _soll , an adjustable deviation value A is also stored. Furthermore, the control or regulating device with the drive unit 4 assigned sensor 6 connected to the control or regulating device 5 an actual value P _is delivered.

As in 2 As can be seen, this parameter P can be either a measured or determined pressure p, a measured or determined torque D, a measured or determined force K (in Newtons) or a measured or determined speed v. In 2 By way of example, a setpoint course P _{soll is represented} in a percentage value of the parameter P along a time axis t. The two deviations A form a tolerance or envelope curve around the setpoint curve P _soll .

In 3 Now this setpoint course P _{soll is shown} without concrete deviations A. In addition, however, a concrete actual value P _ist (in this case the concrete actual pressure p _ist ) is drawn. Furthermore, the concrete actual speed v _{ist of} the tool is also shown. Accordingly, at the beginning of the opening movement Ö, the actual pressure p _is briefly increased, after which he falls off. At the same time the actual speed v _{ist is} smaller. In this area, the actual pressure p _is relatively accurate to the setpoint course P _soll . After approx. 0.12 seconds, however, the tool hits an obstacle H or the mold can not be opened as desired. This results in a sudden increase in actual pressure p _is causing it _to strongly from the setpoint curve P differs. As soon as a deviating deviation value A, not shown here, is exceeded, the further opening movement Ö is stopped or the speed is further throttled, as in FIG 3 seen. By this speed throttling thus a shape protection is realized when opening.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0096183 B1 [0007]
• AT 004744 U1 [0008]
• EP 1343621 B1 [0009]

Claims (9)

Shaping machine, in particular injection molding machine, with - a first machine part, - a second, relative to the first machine part movable machine part, - a drive unit for moving the second, movable machine part between an activity position and a retraction position and - a control or regulating device ( 5 ) for controlling or regulating the drive unit ( 4 ), wherein in the control device ( 5 ) at least one desired value course (P _soll ) of a parameter (P) of the drive unit ( 4 ) and with an actual value (P _ist ) of the same parameter (P) of the drive unit ( 4 ), characterized in that the desired value course (P _soll ) corresponds to a parameter (P) during a return movement of the second machine part from the activity position to the retracted position and by the control device ( 5 ) The retracting movement of the second machine part _soll) deviates by more than an adjustable offset value (A) value _is P) is stoppable at a (the desired value progression P. Molding machine according to claim 1, characterized in that the parameter (P) of the drive unit ( 4 ) Pressure (p), torque (D), force (K) and / or speed (v). Shaping machine according to claim 1 or 2, characterized in that the parameter (P) by a sensor ( 6 ), preferably by a piezoelectric sensor, can be detected. Forming machine according to one of claims 1 to 3, characterized in that the adjustable deviation value (A) for the parameter (P) of the drive unit ( 4 ) in the control device ( 5 ) is deposited. Shaping machine according to one of claims 1 to 4, characterized in that in the control and regulating device ( 5 ) also a desired value course (P _soll ) for an activity movement from the retreat position to the activity position is stored, wherein the control or regulating device ( 5 ) The activity of movement of the second movable machine part _should) (by more than an adjustable offset value (A) deviating actual value P _ist) can be stopped at a (the desired value progression P. Molding machine according to one of claims 1 to 5, characterized in that the shaping machine a closing unit ( 1 ), wherein the first machine part a fixed platen ( 2 ) and the second machine part a relative to the fixed platen ( 2 ) movable platen ( 3 ), wherein the activity position a closed position (SS) of the platens ( 2 . 3 ) and the retraction position an open position (OS) of the platens ( 2 . 3 ) and the return movement is an opening movement (Ö) between the closed position (SS) and the open position (OS). Molding machine according to one of claims 1 to 5, characterized in that the first machine part is a cylinder of a core pull and the second machine part is a piston of a core pull, wherein the activity position is the retracted into a tool position of the core pull. Shaping machine according to one of claims 1 to 5, characterized in that the first machine part is an ejector ram of an ejector and the second machine part is an ejector of an ejector, wherein the activity position is the ejection position of the ejector. Shaping machine according to one of claims 1 to 8, characterized in that the drive unit ( 4 ) has an electric motor.

Images