manufacturing facility

Abstract

Production facility with - an injection unit (2) suitable for molding processes, in particular injection molding processes, which includes a mass cylinder (3) and an injection actuator (4), - a hydraulic system (5) for moving the injection actuator (4), - an access control device (6) which is designed to output an access signal upon detection of access by a person to the production plant (1) and / or of access for a person to the production plant (1), and - an electronic control unit (7) which is designed to operate the hydraulic system (5) in at least one production mode and in at least one safety mode, wherein the control unit (7) is designed to switch from the at least one production mode to the at least one safety mode when the access security device (6) outputs the access signal, wherein the control unit (7) is designed to operate the hydraulic system (5) in the at least one safety mode such that the hydraulic system (5) at least partially, preferably completely, counteracts an axial movement of the injection actuator (4) caused directly or indirectly by an action of a molding compound (31) present in the mass cylinder (3) on the injection actuator (4).

Description

The present invention relates to a manufacturing installation according to the features of the preamble of claim 1 and to a method for operating a manufacturing installation.Manufacturing installations are known which have the following features:an injection unit suitable for molding processes, in particular injection molding processes, which includes a master cylinder and an injection actuator,a hydraulic system for moving the injection actuator,an access safety device which is designed to output an access signal when a person is detected to access the manufacturing system and / or an access possibility for a person to the manufacturing system, andan electronic control unit which is configured to operate the hydraulic system in at least one production mode and in at least one safety mode,wherein the control unit is configured to switch from the at least one manufacturing mode to the at least one security mode when the access security device outputs the access signal.The relevant safety regulations define that measures must be taken when the manufacturing facility is active, but the access safety device is in an open configuration-that is, there is access possibility for persons-or the access safety device detects access of a person. These measures aim at the injection actuator not performing any movement which would cause injection of the plasticized molding compound subjected to high temperatures and pressures into the mounted molding tool. This is because the escape of the molding compound under the prevailing pressures can lead to injuries or death if a person were hit by the molding compound.Known measures for preventing any injection movement are, for example, to switch an injection valve in such a way that the hydraulic fluid is discharged to tank, or to isolate an accumulator from the rest of the hydraulic system.In many cases, this results in the injection actuator performing a slight rearward movement while the manufacturing plant is operated in at least one safety mode. One reason for this is that plasticizing of the molding compound generally continues even in at least one safety mode and more plasticized molding compound thus accumulates in the master cylinder than in normal production operation. On the other hand, the molding material itself may also undergo expansion, especially when it contains dissolved gases for foaming or the like, for example.As a result, the situation thus changed must be taken into account when the manufacturing operation (at least one manufacturing mode) is to be resumed. The changed position of the injection actuator generally leads to the plasticized molding compound being ejected into the open in a controlled manner and being redosed from the plasticizing process. The starting material for the plasticized mass is, of course, lost. This also applies to the time and the work effort required in the described procedure.In the worst case, the molding compound that is too large for the mold is injected when the manufacturing operation is resumed, which may lead to damage to the mold or even destruction of the mold.It is an object of the invention to avoid the loss of material, time and labor and damage while simultaneously complying with the safety regulations.With respect to the production plant, this object is achieved by the features of claim 1, namely in that the control unit is configured to operate the hydraulic system in the at least one safety mode such that the hydraulic system counteracts at least partially, preferably completely, an axial movement of the injection actuator caused directly or indirectly by an action of a plasticized molding compound present in the master cylinder on the injection actuator.With regard to the method, the object is achieved by the features of claim 15, namely by a hydraulic systemthe production facility is operated in a safety mode if access to the production facility and / or an access possibility to the production facility is detected, andoperating in safety mode in such a way that it counteracts at least partially, preferably completely, an axial movement of the injection actuator caused directly or indirectly by an action of a molding compound present in a master cylinder on an injection actuator.Protection is also sought for the use of a production plant according to the invention in the method according to the invention.A basic idea of the invention is the realization that the hydraulic system can be operated in such a way that the rearward movement of the injection actuator is also at least partially avoided in the at least one safety mode. The described undesirable consequences therefore do not occur from the outset.A central aspect is that the hydraulic system, although it is in the at least one safety mode, can maintain a pressure for the injection actuator, so that on the one hand no advancing movement takes place, but the mentioned rearward movement is not carried out or is carried out only to such a small extent that the mentioned consequences, in particular the need for spraying out and re-dosing, do not occur.The injection unit suitable for injection molding processes generally has a plasticizing screw which is arranged rotatably and linearly displaceably in the compound cylinder. The rotational movement and usually also a heating of the mass cylinder thermally and shear loads the plastic material present, for example, as granules and thus changes over to a plastic state. During this, the plasticizing screw executes a certain retraction movement, so that the plasticized molding compound collects in the plasticizing cylinder in the screw antechamber. This process is referred to as dosing.By means of an axial feed movement, the plasticized molding compound is subsequently injected into a mold cavity of a tool mounted on the molding machine and thus primary molded.However, other configurations of an injection unit suitable for an injection molding process are also conceivable. For example, an extruder (i.e. a plasticizing screw without an axial degree of freedom of movement) could also feed one or more injection pistons (so-called "shot pots" or "shot pots").Other molding processes are known that are somewhat similar to injection molding processes, wherein an injection actuator exerts a pressure on a plasticized or liquid molding compound, which pressure can lead to the injection actuator performing undesired movements when switching to the safety mode. These other shaping processes and naturally injection molding processes themselves are summarized under the term shaping processes in the context of the present invention.Access safety devices are known per se and consist, for example, of a protective grille and a closed protective door which are connected to the control unit via a safety circuit (closed configuration, access possibility not being possible). If the protective door is opened (open configuration, access possibility is given), the corresponding safety circuit also opens and the control unit automatically switches to the at least one safety mode because it is possible for persons to be located in the region of the shaping installation.The opening of the safety circuit can be understood here as the access signal output by the access safety device. The access signal can therefore be realized not only as an active signal, but also as the omission of a continuous signal.The access safety device collectively refers to those devices that are intended to control the access of persons to those areas where dangers may occur due to the shaping process.In addition to the aforementioned protective grille and doors, light barriers and light curtains, for example, can be used for this purpose. Another example would be a nozzle guard for an injection nozzle, which is a guard plate, by means of which persons in the vicinity of the injection nozzle are to be protected from being hit by molding compound emerging under extreme pressure.Within the scope of the invention, the access protection device can be understood to mean that at least the possibility is provided of detecting access of a person to the manufacturing facility and / or the possibility of access of a person to the manufacturing facility and, if this occurs, outputting the access signal.The production plant is to be understood as a production cell or part of a production cell in which the mentioned injection molding process is carried out.The electronic control unit can preferably be a central machine control of the production plant and / or of the shaping machine. Of course, it is also conceivable for the electronic control unit to be implemented separately from the machine by one or more computer servers arranged on the machine or remote from the machine-realized centrally or by distributed computing.In most cases, the control unit will perform controls and regulations of a wide variety of machine parameters. In principle, however, it is also possible to provide a separate control unit for the invention, which only takes care of the functions according to the invention.In this sense, the at least one safety mode can be understood as belonging to the hydraulic system. Naturally, in many real cases, the rest of the shaping installation will also be influenced by the at least one safety mode. As mentioned, the operation of the hydraulic system according to the invention is a core aspect of the invention. The same applies analogously to the at least one production mode.The at least one production mode is to be understood as the mode in which the production plant produces molded parts, namely automatically, semi-automatically or theoretically also guided by an operating person.This is not provided at the moment in the at least one safety mode. Rather, in at least one safety mode, no injection movement by the injection actuator should be possible. The relevant safety regulations generally specify further safety measures which are to be observed, for example at least one of the following:It is to be ensured that the injection nozzle is closed or that all the injection nozzles are closed.It is to be ensured that the molding compound is not discharged, in particular injected, from the master cylinder.The powers of the existing drives-preferably of all drives-are limited to respective (relatively low) maximum powers.In principle, however, it is also conceivable within the scope of the invention that there are one or more safety modes which are only distinguished from the at least one production mode in that they realize the reaction according to the invention against the rearward movement of the injection actuator.The invention can be used both in existing production plants (as retrofit), for example by installing the interconnection line listed below together with associated components, and in newly produced production plants.The facts, features and effects explained in connection with the prior art can also occur and / or be used in connection with the invention.Advantageous further developments of the invention are defined in the dependent claims.For moving the injection actuator, a hydraulic piston-cylinder unit may be provided, preferably wherein the piston is rotatable relative to the cylinder.Due to the rotation of the piston, rotation of the injection actuator in the master cylinder can be realized particularly easily.For the rotation of the injection actuator, a separate metering drive can be provided, which is designed, for example, as a hydraulic motor. The hydraulic motor can be supplied by the hydraulic system according to the invention or by a separate hydraulic system.In particularly preferred embodiments, the metering drive transmits a rotational movement to the piston rotatably mounted in the cylinder, and the rotational movement is transmitted from the piston to the plasticizing screw mounted thereon.In principle, other embodiments are also conceivable, wherein recourse is not made to a piston-cylinder unit. For example, a hydraulic motor could be used, the output movements of which are converted into a linear movement via a mechanism, for example a spindle or a toothed rack. However, embodiments with a piston-cylinder unit are preferred.The injection actuator may include a plasticizing screw and / or an injection plunger.The hydraulic system may include at least one of:at least one pump together with a pump motor for driving the at least one pump,at least one pressure accumulator and preferably a blocking slide, by means of which the at least one pressure accumulator can be decoupled from the rest of the hydraulic system,an injection valve which is designed for carrying out an injection movement in order to release, shut off and / or meter a first hydraulic fluid flow provided for the injection actuator,a brake valve which is designed to release, shut off and / or meter a second flow of hydraulic fluid which is pushed out of the piston-cylinder unit during the injection movement, and / ora low-pressure volume, preferably a tank.The brake valve can preferably be used meaningfully in the case of injection units which realize particularly fast injection movements. The brake valve produces an additional degree of freedom for the control or regulation of the injection movement, which can be used for a particularly precise regulation, as is advantageous with particularly fast movements.Of course, a plurality of pump motors can also be present, which drive one or more pumps jointly on a shaft or separately.The control unit can preferably be designed to operate in at least one safety modelimiting a rotational speed of the at least one pump motor to a maximum rotational speed,activating the at least one blocking slide for decoupling the at least one pressure accumulator from the rest of the hydraulic system,activating the injection valve in such a way that there is a hydraulic connection between the injection actuator and the low-pressure volume, preferably wherein there is a fluid connection between the injection actuator and the low-pressure volume when a further valve is switched, and / oractivating the brake valve in such a way that there is a fluid connection between the piston-cylinder unit and the low-pressure volume.As mentioned, a basic aspect of the at least one safety mode is that advancing movements of the injection actuator are to be avoided, since they can lead to hazardous situations for persons in the area of the production plant.A hydraulic connection is understood to mean a connection which can become a fluid connection under certain pressure and / or switching conditions, but does not have to be present as such at all times. For example, a prestressed or switchable further valve can be present, so that the fluid connection is only released when a pressure in the hydraulic fluid exceeds a maximum pressure or the further valve is switched.The hydraulic system can include an interconnection line which is configured such that, in the at least one safety mode, there is a fluid connection between a pressure side of a pressure source, preferably the at least one pump, and the injection actuator, preferably via the injection valve.At least one, preferably all, of the following can be provided in the interconnection line:a diaphragm for defining a maximum hydraulic fluid volume flow,a volume flow switching valve, preferably a volume flow control valve, and / ora pressure regulating valve.By means of a separate volume flow control valve for the volume flow and / or a separate pressure control valve, the volume flow or the pressure at the injection actuator can be controlled particularly well, as a result of which the risk of an undesired feed movement in at least one safety mode can be kept particularly low.A ram pressure line can preferably branch off from the interconnection line, which leads into the low-pressure volume and in which a further valve is arranged, which is switchable.The further valve is to be understood as a separate valve from the injection valve.The further valve can be switched when a pressure in the hydraulic system becomes too high, for example when a pressure threshold value is exceeded.In particularly preferred embodiments, however, the brake valve can function as the further valve.Particularly preferably, the dynamic pressure line branches off from the interconnection line on the actuator side with respect to the orifice, the volume flow control valve and / or the pressure control valve.Particularly preferably, the ram pressure line branches off from the interconnection line on the pump side with respect to the injection valve.A position sensor provided for detecting a position of the injection actuator and / or of the piston of the piston-cylinder unit may be present, the measurement signals of which position sensor can be fed to the control unit.The control unit can particularly preferably be designed to actuate the hydraulic system, preferably the pump motor, on the basis of the measurement signals of the position sensor in order to increase or decrease the pressure at the injection actuator, in order to at least partially counteract a change in position of the injection actuator caused by the action of the plasticized molding compound present in the master cylinder.This need not be a classic control because the (active) retraction of the injection actuator need not necessarily be provided.Nevertheless, a P, PI and / or PID control law can of course be used for this purpose, wherein preferably conservative amplification factors are selected.The injection unit can have a closure nozzle which is designed to prevent the escape of plasticized molding compound from the barrel, wherein a closure nozzle position sensor is preferably provided, the measurement signals of which can be fed to the control unitThis allows a further check to be made that the injection actuator is not performing an injection movement. This is because if the shutter position sensor detects that the shutter nozzle is closed, injection of the molding compound cannot be performed physically.The access safety device can have at least one of the following: a protective grille, a protective wall and / or a protective door and / or a light barrier and / or a light curtain and / or a nozzle guard.The manufacturing plant may comprise a shaping machine and the injection unit may be part of the shaping machine.Forming machines are understood to mean, for example, injection molding machines, transfer molding machines or presses.Further advantages and details of the invention are evident from the figures and the associated description of the figures. The following are shown: FIG. 1 schematically shows an exemplary embodiment of an injection unit, FIG. 2 schematically shows an exemplary embodiment of a hydraulic system, FIG. 3 schematically shows a further exemplary embodiment of a hydraulic system, and FIG. 4 schematically shows an exemplary embodiment of a production plant according to the invention.FIG. 1 schematically shows an injection unit 2, as can be used in injection molding machines.A plasticizing worm is arranged rotatably and axially displaceably in a compound cylinder 3.The plasticizing screw can be driven axially by means of a piston-cylinder unit including a piston 8 and a cylinder 9.The piston 8 is rotatably mounted together with the plasticizing screw, so that a metering drive 29 can transmit a rotational movement to the piston 8 and further to the plasticizing screw.The piston-cylinder unit together with the plasticizing screw together form the injection actuator 4 within the meaning of the invention.The starting material, for example a plastic granulate, can be introduced into the master cylinder 3 via a hopper 30, wherein it is plasticized by shearing and the action of heat-preferably the master cylinder is heated from the outside. The plasticized molding material 31 is then present in the barrel 3 upstream of the plasticizing screw.The direct emergence of the plasticized molding compound 31 can be prevented or controlled by means of a closure nozzle 23, but it is also conceivable in principle that a closure nozzle 30 is not present.By monitoring the position of the closure nozzle 23 by means of a closure nozzle position sensor 24, a further check can take place that the injection actuator 4 does not execute an injection movement. This is because if the shutter nozzle position sensor 24 detects that the shutter nozzle 23 is closed, physically no plasticized molding compound 31 can escape from the master cylinder 3 and possibly pass into the molding tool which is not fully closed.In preferred embodiments, the position-monitored closure nozzle 23 is integrated into the safety concept of the production plant 1 via at least one safety circuit.For injection, the piston 8 can be pushed hydraulically forwards (on the left in FIG. 1 ) in the cylinder 9. This pushes the plasticized molding compound 31 out of the barrel 3 and, for example, injects it into a molding tool, in which the molding compound is primary molded.As a result, further molding compound is plasticized by the rotation of the plasticizing screw, so that sufficient plasticized molding compound 31 is available for a further injection molding process. This is referred to as dosing or dosing.During metering, the injection actuator 4 usually performs a slow rearward movement (i.e. to the right in FIG. 1 ) because the dynamic pressure in the plasticized molding compound 31, visualized as an arrow to the right, slightly exceeds the counterforce exerted by the piston 8, visualized as an arrow to the left.If the manufacturing system 1 is switched into the at least one safety mode, for example because a safety door is opened as shown in FIG. 4, it must be ensured that no injection movement takes place, wherein in the prior art the piston 8 is usually simply relieved by draining the hydraulic fluid to the tank.However, this can lead to the aforementioned retraction movement also continuing, even if, for example, the feeding of granulate is interrupted because the pressure in the hydraulic system 5 and the friction in the cylinder 9 are too low. This undesired retraction movement can also be referred to as screw flights.FIG. 2 schematically shows an embodiment of a hydraulic system 5 as may be used to drive the piston-cylinder unit, which are part of the injection actuator, and which is capable of at least partially preventing the undesired retraction movement in the at least one safety mode.The hydraulic system 5 has the following components:at least one pump 10 together with a pump motor 11 for driving the at least one pump 10,at least one pressure accumulator 12 and a blocking slide 13, by means of which the at least one pressure accumulator 12 can be decoupled from the rest of the hydraulic system 5,an injection valve 14, which is designed to perform an injection movement in order to release, shut off and / or meter a first hydraulic fluid flow provided for the injection actuator 4,a brake valve 15 which is designed to release, shut off and / or meter a second flow of hydraulic fluid pushed out of the piston-cylinder unit during the injection movement, and / ora low-pressure volume in the form of at least one tank, which is visualized by the usual symbol.The pressure accumulator 12 can preferably be designed as a bubble accumulator which has a gas-filled bubble in a pressure vessel. Pressurized hydraulic fluid compresses the gas-filled bladder so that the pressure is stored in the compressed gas.The pressure accumulator 12 is preferably dimensioned and used in such a way that the pressure required for the injection movement comes substantially completely from the pressure accumulators 12 and the pump 10 is used substantially only to charge the pressure accumulator 12 in the at least one production mode. Of course, a similar procedure can also be implemented with a plurality of pressure accumulators 12.A position sensor 22 for detecting the position of the piston 8 and thus of the injection actuator 4 is provided.A connecting line 16 makes it possible to connect that chamber in the cylinder 9 which is pressurized for carrying out the injection movement (in contrast to FIG. 1, the chamber acting to the right) to the pressure side of the pump 10 via the injection valve 14.The following is provided in the interconnection line 16:a diaphragm 17 for defining a maximum hydraulic fluid volume flow,a volume flow control valve 18 and / ora pressure control valve 19.A ram pressure line 20 branches off from the interconnection line 16, which ram pressure line opens into the low-pressure volume and in which a further switchable valve 21 is arranged, so that a fluid connection is produced between the interconnection line 16 and the low-pressure volume when the further valve 21 is switched, for example because the pressure in the hydraulic system 1 becomes too high. For detecting the pressure, a pressure sensor, not shown, can of course be provided. The further valve 21 can also be referred to as a dynamic pressure cartridge, that is to say it can be a cartridge valve and / or a seat valve.In this exemplary embodiment, the dynamic pressure line 20 branches off from the interconnection line 16:actuator-side with respect to the orifice 17, the volume flow control valve 18 and the pressure control valve 19 andpump side with respect to the injection valve 14.The control unit 7 is schematically shown. It is in signal connection with the various influenceable elements of the hydraulic system, namely for example the pump motor 11, the pump 10 (if it is an adjustable pump), the injection valve 14, the brake valve 15, the blocking slide 13, the position sensor 22, the volume flow control valve 18, the pressure control valve 19 and all further controllable valves which are drawn in FIG. 2 and the protective door 26 shown in FIG. 4.When the control unit 7 changes to the at least one safety mode, it first triggers the followinglimiting a rotational speed of the at least one pump motor 11 to a maximum rotational speed,activating the at least one blocking slide 13 for decoupling the at least one pressure accumulator 12 from the rest of the hydraulic system 5 (position shown),activating the injection valve 14 (for example by supplying current) so that the hydraulic connection exists between the injection actuator 4 and the low-pressure volume (position shown), wherein a fluid connection exists between the injection actuator 4 and the low-pressure volume via the interconnection line 16 and the dynamic pressure line 20 when the further valve 21 is switched, andactivating the brake valve 15 so that there is a fluid connection between the piston-cylinder unit and the low-pressure volume (position shown).As mentioned, the control unit 7 is signal-connected to the position sensor 22 and can thus detect when an undesired retraction movement of the piston 8 and thus of the injection actuator 4 takes place.In the switching position shown in FIG. 2, the control unit 7 can actuate the pump motor 11, the pump 10, the pressure regulating valve 19, the volume flow regulating valve 18 and the injection valve 14 in such a way that this retraction movement is at least partially, preferably completely counteracted.In other words, the control unit in this exemplary embodiment is designed to actuate the hydraulic system 5, preferably the at least one pump 10, on the basis of the measurement signals of the position sensor 22 in order to increase or decrease the pressure at the injection actuator 4 (here in particular the pressure in the chamber acting to the right in the cylinder 9) in order to at least partially counteract a change in position of the injection actuator 4 caused by the action of the plasticized molding compound 31 present in the master cylinder 3.At the same time, in the present example, all safety requirements are fulfilled because the following measures are taken:The volume flow directed to the cylinder 9 cannot become too large because of the orifice 17.The pressure in the chamber of the cylinder 9 acting to the right can be relieved by opening the further valve 21 if a pressure threshold value or the like is exceeded.An unwanted injection movement of the piston 8 or of the injection actuator 4 can thereby be reliably prevented.FIG. 3 schematically shows a further exemplary embodiment of a hydraulic system 5.In contrast to FIG. 2, the brake valve 15, which is spring-loaded in any case, takes over the function of the further valve 21, as a result of which the interconnection of the injection valve 14 and of the brake valve 15 makes do with fewer connections and the hydraulic block containing the injection valve 14 and the brake valve 15 can be of simpler design.The remaining components, elements and functions described in connection with FIG. 2 are likewise present in the exemplary embodiment according to FIG. 3.FIG. 4 schematically shows an exemplary embodiment according to the invention of a production plant 1 according to the invention.The injection unit 2 is similar to that of FIG. 1, wherein the shutter nozzle position sensor 24 and some reference numerals are no longer drawn for reasons of clarity, wherein the corresponding elements including the shutter nozzle position sensor 24 are of course still present.In addition, in the manufacturing plant 1 according to FIG. 4, a closing unit 28 is provided, for example, with mold clamping plates that can be moved relative to one another. A molding tool to be mounted thereon is indicated by dashed lines.In order to carry out the production process in the at least one production mode, the molding tool can be closed by means of the mold clamping plates and the molding compound 31 plasticized in the metering process can be injected by the injection movement into at least one mold cavity in the molding tool, as a result of which the plasticized molding compound 31 is primary molded and a molded part is produced after cooling of the latter.In the configuration schematically illustrated in FIG. 4, the injection unit 2 together with the closing unit 28 forms a shaping machine 27, here specifically an injection molding machine.Provided around the manufacturing installation 1 is an access safety device 6, which is known per se and which in this exemplary embodiment has a protective wall 25 and a protective door 26, the latter being connected by signals to the control unit as mentioned.If the protective door 26 is opened, for example because a person in the safety area wants to remove a jammed molded part, the control unit 7 automatically switches into at least one safety mode and performs the functions explained in connection with FIG. 2 in order firstly to prevent the injection actuator 4 from performing an injection movement and secondly to prevent the injection actuator 4 from performing an undesired retraction movementThe hydraulic system 5 in FIG. 4 can be designed for this purpose, for example, as in FIG. 2 or FIG. 3.Further exemplary embodiments are conceivable. For example, the pressure source used to prevent the screw retraction motion could also be a pressure accumulator 12. For example, the connection line 16 could also be connected hydraulically to the cylinder 9 via a valve separate from the injection valve 14. In addition, the function of the orifice could be fulfilled, for example, by a passive spring-loaded valve.List of reference numbers:1 Production plant 2 Injection unit 3 Master cylinder 4 Injection actuator 5 Hydraulic system 6 Access safety device 7 Control unit 8 Piston 9 Cylinder 10 Pump 11 Pump motor 12 Pressure accumulator 13 Blocking slide 14 Injection valve 15 Brake valve 16 Interconnection line 17 Orifice 18 Volume flow control valve 19 Pressure control valve 20 Dynamic pressure line 21 Further valve 22 Position sensor 23 Closure nozzle 24 Closure nozzle position sensor 25 Protective grid 26 Protective door 27 Moulding machine 28 Closure unit 29 Metering motor 30 Hopper 31 Plasticized moulding compound

Claims

Manufacturing plant comprising - an injection unit (2) suitable for shaping processes, in particular injection moulding processes, which includes a master cylinder (3) and an injection actuator (4), - a hydraulic system (5) for moving the injection actuator (4), - an access securing device (6) which is designed to emit an access signal on detection of access of a person to the manufacturing plant (1) and / or an access possibility for a person to the manufacturing plant (1), and - an electronic control unit (7) which is designed to operate the hydraulic system (5) in at least one manufacturing mode and in at least one safety mode, wherein the control unit (7) is designed to switch from the at least one manufacturing mode into the at least one safety mode when the access safety device (6) emits the access signal, characterized in that the control unit (7) is designed to switch over from the at least one manufacturing mode into the at least one safety mode, operating the hydraulic system (5) in the at least one safety mode in such a way that the hydraulic system (5) counteracts at least partially, preferably completely, an axial movement of the injection actuator (4) caused directly or indirectly by an action of a molding compound (31) present in the master cylinder (3) on the injection actuator (4).Production plant according to claim 1, wherein a hydraulic piston-cylinder unit is provided for moving the injection actuator (4), preferably wherein the piston (8) is rotatable relative to the cylinder (9).Production plant according to one of the preceding claims, wherein the injection actuator (4) contains a plasticizing screw and / or an injection piston.Production plant according to one of the preceding claims, wherein the hydraulic system (5) has at least one of the following: - at least one pump (10) together with a pump motor (11) for driving the at least one pump (10), - at least one pressure accumulator (12) and preferably a blocking slide (13), by means of which the at least one pressure accumulator (12) can be decoupled from the remainder of the hydraulic system (5), - an injection valve (14) which is designed for carrying out an injection movement in order to release, shut off and / or meter a first hydraulic fluid flow provided for the injection actuator (4), - a brake valve (15) which is designed for releasing, shutting off and / or metering a second hydraulic fluid flow pushed out of the piston-cylinder unit during the injection movement, and / or - a low-pressure volume, preferably a tank.Production plant according to claim 4, wherein the control unit (7) is designed to - limit a rotational speed of the at least one pump motor (11) to a maximum rotational speed in the at least one safety mode, - actuate the at least one blocking slide (13) for decoupling the at least one pressure accumulator (12) from the rest of the hydraulic system (5), - actuate the injection valve (14) in such a way that a hydraulic connection exists between the injection actuator (4) and the low-pressure volume, preferably wherein a fluid connection exists between the injection actuator (4) and the low-pressure volume when a further valve (21) is switched, and / or - actuate the brake valve (15) in such a way that a fluid connection exists between the piston-cylinder unit and the low-pressure volume.Production plant according to one of the preceding claims, wherein the hydraulic system (5) contains an interconnection line (16) which is set up such that, in the at least one safety mode, there is a fluid connection between a pressure side of a pressure source, preferably the at least one pump (10), and the injection actuator (4), preferably via the injection valve (14).Production plant according to claim 6, wherein at least one of the following is provided in the interconnection line (16): - a diaphragm (17) for defining a maximum hydraulic fluid volume flow, - a volume flow switching valve, preferably a volume flow control valve (18), and / or - a pressure control valve (19).Production plant according to claim 6 or 7, wherein a ram pressure line (20) branches off from the interconnection line (16), which ram pressure line opens into the low-pressure volume and in which a further valve (21) is arranged, which valve can be switched.The manufacturing plant according to claim 4 and claim 8, wherein the brake valve (15) functions as the further valve (21).Production plant according to one of the preceding claims, wherein a position sensor (22) provided for detecting a position of the injection actuator (4) and / or of the piston (8) of the piston-cylinder unit is present, the measurement signals of which can be fed to the control unit (7).Production plant according to claim 10, wherein the control unit (7) is configured to control the hydraulic system (5), preferably the pump motor (11), on the basis of the measurement signals of the position sensor (22) for increasing or decreasing the pressure at the injection actuator (4) in order to at least partially counteract a change in position of the injection actuator (4) caused by the action of the plasticized molding compound (31) present in the master cylinder (3).Production plant according to one of the preceding claims, wherein the injection unit (2) has a closure nozzle (23) which is designed to prevent escape of plasticized molding compound (31) from the molding cylinder (3), wherein preferably a closure nozzle position sensor (24) is provided, the measurement signals of which can be fed to the control unit (7).Production plant according to one of the preceding claims, wherein the access safety device (6) has at least one of the following: a protective grille (25), a protective wall and / or a protective door (26) and / or a light barrier and / or a light curtain and / or a nozzle guard.Production plant according to one of the preceding claims, wherein the production plant (1) has a shaping machine (27) and the injection unit (2) is part of the shaping machine (27).Method for operating a manufacturing installation, in particular according to one of the preceding claims, wherein a hydraulic system (5) - of the manufacturing installation (1) is operated in a safety mode if access to the manufacturing installation (1) and / or an access possibility to the manufacturing installation (1) is detected, and - is operated in the safety mode in such a way that it counteracts an axial movement of the injection actuator (4) caused directly or indirectly by an action of a molding compound (31) present in a mass cylinder (3) on an injection actuator (4).Use of a production plant according to one of Claims 1 to 14 in a method according to Claim 15.

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