DE102022112316A1 - Injection unit, molding machine with such an injection unit and method for checking an injection unit - Google Patents

Abstract

Injection unit for a molding machine (2) comprising - at least one injection cylinder (3), - an injection screw (5) mounted to be displaceable axially along a longitudinal axis (4) in at least one injection cylinder (3), - an injection screw (5) arranged in at least one injection cylinder (3) and a non-return valve (6) connected to the injection screw (5) so that it can move axially, in order to prevent a backflow of a plasticized material in at least one injection cylinder (3) against a conveying direction of the injection screw (5) to form a mass cushion in front of the non-return valve (6), - at least a control or regulating unit (7) which is designed to control or regulate an axial movement of the injection screw (5) and- at least one sensor (8) for determining an axial position of the injection screw (5), the axial position of the injection screw (5) is a measure of the volume of the mass cushion, the at least one control or regulating unit (7) is designed to apply a force to the injection screw (5) axially in the conveying direction in order to build up pressure on the mass cushion, the control or regulating unit (7) being designed to, on the basis of the measured values of the at least one sensor (8) a reduction in the mass cushion caused by wear of the non-return valve (6).

Description

The present invention relates to an injection unit for a molding machine with the features of the preamble of claims 1 and 4, a molding machine with such an injection unit, a method for checking at least one injection unit, and a computer program product and a computer-readable storage medium for checking at least one injection unit.

Molding machines can be understood to mean injection molding machines, transfer presses, presses and the like. Forming machines in which the plasticized mass is fed to an open mold are also entirely conceivable.

The state of the art is outlined below using an injection molding machine. The same applies in general to shaping machines.

• - wenigstens einen Einspritzzylinder,
• - eine im wenigstens einen Einspritzzylinder axial entlang einer Längsachse verschiebbar gelagerte Einspritzschnecke und
• - eine im wenigstens einen Einspritzzylinder angeordnete und mit der Einspritzschnecke axial bewegungsschlüssig verbundene Rückstromsperre, um zur Bildung eines Massepolsters vor der Rückstromsperre ein Rückströmen einer plastifizierten Masse im wenigstens einen Einspritzzylinder entgegen einer Förderrichtung der Einspritzschnecke zu verhindern.

Generic injection units for injection molding machines include

• - at least one injection cylinder,
• - an injection screw mounted in the at least one injection cylinder so as to be displaceable axially along a longitudinal axis and
• - A non-return valve arranged in at least one injection cylinder and connected to the injection screw in an axially movement-locking manner in order to prevent a backflow of a plasticized material in the at least one injection cylinder against a conveying direction of the injection screw to form a mass cushion in front of the non-return valve.

Corresponding injection units familiar from the prior art can thus push out a plasticized mass, which is located in the injection cylinder, via an axial movement of the injection screw along a longitudinal axis of the injection screw. This usually happens via an injection side of the injection cylinder, which is often designed as an injection nozzle.

In order to be able to feed plasticized mass to the injection cylinder, it is known from the prior art to plasticize it via the injection screw - more precisely: by rotating the injection screw - and to convey it along the longitudinal axis of the injection screw into an antechamber of the screw, from which then via the injection movement of the injection screw pushes the plasticized mass out of the injection cylinder.

In order to allow the plasticized mass to be conveyed along the injection screw, but to prevent the plasticized mass from flowing back out of the injection cylinder during the injection movement or the ejection movement, non-return valves are provided.

Since the non-return valve in the injection cylinder is a moving component and is continuously in contact with the plasticized material flowing past, the non-return valve is exposed to friction, which friction inevitably leads to wear.

It is known from the prior art that non-return valves represent a wearing part of the injection unit and have to be replaced at a specified service interval, since after a given time they can no longer guarantee the required process accuracy due to wear.

Even if, during the continuous wear of the non-return valve, process parameters of the injection molding machine can be adjusted to counteract the growing inaccuracy caused by wear, there is a limit at which it is no longer possible to counteract the wear by adjusting process parameters of the injection molding machine and the non-return valve must be exchanged.

Consequently, there is an effort from the prior art to be able to determine an exact present state of the non-return valve in order to be able to determine the process parameter or a service interval more precisely.

It is also known (e.g. through the EP 2 000 281 A1 or the DE 10 2017 004 374 A1 ), to deduce wear of the non-return valve from the process parameters recorded during the production cycle of the injection molding machine (such as a load moment of a plasticizing screw), with the process parameters then being adapted to the increasing wear.

However, this has the disadvantage that the process parameters can only be tracked to an already existing process deviation. It is therefore not the actual wear that is measured, but a deviation that is declared as wear (however, it could also be caused by other parameters, such as a change in the setting parameters).

Furthermore, these methods have the disadvantage that the ongoing process (through For example, changing material qualities, material contamination or temperature deviations) Measurement inaccuracies arise, which only lead to acceptable conclusions about wear of the non-return valve through expensive and complex control strategies, as is the case, for example, with the DE 10 2019 128 177 A1 or the DE 10 2018 007 641 A1 is described.

For example, it is from the AT521585A1 It is known to monitor the non-return valve via ultrasonic sensors, which are arranged on the injection cylinder, and to estimate a size and/or wear of the non-return valve from the measurement results of the ultrasonic sensor. However, this makes it necessary to arrange complex and expensive measuring sensors on the injection cylinder, which also have a short service life due to the high thermal stresses. In order to increase the service life of the sensors, temperature-resistant sensors could be used, which, however, are many times more complex and therefore more expensive.

The object of the invention is therefore to provide an injection unit, a method, a shaping machine, a computer program product and a computer-readable storage medium, with which wear on the non-return valve can be easily detected and/or can be detected early before it influences the production cycle and/or as little as possible little impairment of the production process is metrologically accessible and / or by simple means - is detectable - preferably inexpensive.

Regarding the injection unit for a molding machine, this object is solved by the features of claim 1 and/or claim 4. Furthermore, protection is sought for a molding machine with an injection unit according to the invention.

With regard to the method, the stated object is achieved by the features of claims 16 and/or 17, with regard to the computer program product with the features of claims 18 and/or 19 and with regard to the computer-readable storage medium with the features of claim 20.

Advantageous embodiments are defined on the basis of the dependent claims.

Molding machines can be understood to mean injection molding machines, transfer presses, presses and the like. Forming machines in which the plasticized mass is fed to an open mold are also entirely conceivable.

A device according to the invention, a method according to the invention, a computer program product according to the invention and/or a computer-readable storage medium according to the invention can be used and subsequently installed through their use in already known variants of the prior art, such as described in the introduction to the description.

• - wenigstens einen Einspritzzylinder,
• - eine im wenigstens einen Einspritzzylinder axial entlang einer Längsachse verschiebbar gelagerten Einspritzschnecke,
• - eine im wenigstens einen Einspritzzylinder angeordnete mit der Einspritzschnecke axial bewegungsschlüssig verbundene Rückstromsperre, um zur Bildung eines Massepolsters vor der Rückstromsperre ein Rückströmen einer plastifizierten Masse im wenigstens einen Plastifizierzylinder entgegen einer Förderrichtung der Einspritzschnecke zu verhindern,
• - wenigstens eine Steuer- oder Regeleinheit, die dazu ausgebildet ist, eine axiale Bewegung der Einspritzschnecke zu steuern oder zu regeln und
• - wenigstens einen Sensor zur Ermittlung einer axialen Position der Einspritzschnecke, wobei die axiale Position der Einspritzschnecke ein Maß für das Volumen des Massepolsters ist,

wobei die wenigstens eine Steuer- oder Regeleinheit dazu ausgebildet ist, die Einspritzschnecke axial in Förderrichtung mit einer Kraft zu beaufschlagen, um einen Druck auf den Massepolster aufzubauen, und auf Basis der Messwerte des wenigstens einen Sensors auf eine sich durch Verschleiß der Rückstromsperre hervorgerufene (insbesondere volumenmäßige und/oder massemäßige) Verringerung des Massepolsters zu schließen.In a first variant of the invention, this is done in that the injection unit comprises the following:

• - at least one injection cylinder,
• - an injection screw mounted in at least one injection cylinder so that it can be displaced axially along a longitudinal axis,
• - a non-return valve arranged in at least one injection cylinder and connected to the injection screw in an axially non-moving manner in order to prevent a backflow of a plasticized material in the at least one plasticizing cylinder against a conveying direction of the injection screw to form a mass cushion in front of the non-return valve,
• - at least one control or regulating unit which is designed to control or regulate an axial movement of the injection screw and
• - at least one sensor for determining an axial position of the injection screw, the axial position of the injection screw being a measure of the volume of the mass cushion,

wherein the at least one control or regulating unit is designed to apply a force to the injection screw axially in the conveying direction in order to build up pressure on the mass cushion, and on the basis of the measured values of the at least one sensor to a wear of the non-return valve (in particular close volumetric and / or mass moderate) reduction of the mass cushion.

In this way, the tightness of a non-return valve can be determined quickly and inexpensively, it being possible to infer wear and tear of the non-return valve from the tightness of the non-return valve.

Provision can preferably be made for the control or regulating unit to be designed to output a signal which is representative of the tightness of the non-return valve on the basis of the measured values of the at least one sensor.

Provision can be made for the control or regulating unit to be designed on the basis of the measured values of the at least one sensor to determine radial wear of the non-return valve, preferably a distance (changed due to wear) between an inner surface of the at least one injection cylinder and the non-return valve arranged therein.

• - wenigstens einen Einspritzzylinder,
• - eine im wenigstens einen Einspritzzylinder axial entlang einer Längsachse verschiebbar gelagerte Einspritzschnecke,
• - eine im wenigstens einen Einspritzzylinder angeordnete und mit der Einspritzschnecke axial bewegungsschlüssig verbundene Rückstromsperre, um zur Bildung eines Massepolsters vor der Rückstromsperre ein Rückströmen einer plastifizierten Masse im wenigstens einen Einspritzzylinder entgegen einer Förderrichtung der Einspritzschnecke zu verhindern,
• - wenigstens einer Steuer- oder Regeleinheit, die dazu ausgebildet ist, eine axiale Bewegung der Einspritzschnecke zu steuern oder zu regeln und
• - wenigstens ein Sensor zur Ermittlung einer axialen Position der Einspritzschnecke,

wobei die wenigstens eine Steuer- oder Regeleinheit dazu ausgebildet ist, während einer ersten Druckphase die Einspritzschnecke axial in Förderrichtung mit einer Kraft zu beaufschlagen, um einen Druck auf den Massepolster aufzubauen, und die Steuer- oder Regeleinheit dazu ausgebildet ist,

• - die Einspritzschnecke während einer anschließenden ersten Rückzugsphase axial entgegen der Förderrichtung zu verschieben,
• - die Einspritzschnecke während einer wiederum anschließenden zweiten Druckphase axial in Förderrichtung mit einer Kraft zu beaufschlagen, um einen Druck auf den Massepolster aufzubauen, und
• - mithilfe des wenigstens einen Sensors axiale Positionen und/oder eine Veränderung zwischen den axialen Positionen der Einspritzschnecke während der ersten Druckphase und der zweite Druckphase zu ermitteln und daraus einen Verschleiß der Rückstromsperre zu bestimmen.

Alternatively or additionally, in a second variant of the invention, it can be provided that the injection unit comprises the following:

• - at least one injection cylinder,
• - an injection screw mounted in at least one injection cylinder so as to be displaceable axially along a longitudinal axis,
• - a non-return valve arranged in at least one injection cylinder and connected to the injection screw in an axially non-moving manner in order to prevent a backflow of a plasticized material in the at least one injection cylinder against a conveying direction of the injection screw to form a mass cushion in front of the non-return valve,
• - at least one control or regulating unit which is designed to control or regulate an axial movement of the injection screw and
• - at least one sensor for determining an axial position of the injection screw,

wherein the at least one control or regulating unit is designed to apply a force to the injection screw axially in the conveying direction during a first pressure phase in order to build up pressure on the mass cushion, and the control or regulating unit is designed to do this,

• - to move the injection screw axially against the conveying direction during a subsequent first retraction phase,
• - to apply a force to the injection screw during a subsequent second pressure phase, axially in the conveying direction, in order to build up pressure on the mass cushion, and
• - Using the at least one sensor to determine axial positions and/or a change between the axial positions of the injection screw during the first pressure phase and the second pressure phase and to determine wear on the non-return valve therefrom.

The change in the position of the injection screw is therefore to be assigned as a change in the mass cushion (the change in its mass or volume, so to speak).

Accordingly, an axial position of the injection screw can be determined during a first pressure phase. Then, in a first withdrawal phase, the injection screw is withdrawn and a further (plasticized) mass is fed to the mass cushion via the non-return valve. With the build-up of a second subsequent pressure phase, the non-return valve closes again and pressure is built up on the mass cushion, which is now enlarged, and an axial position of the injection screw can again be measured.

From these two axially measured positions during the pressure phases and the knowledge of the retraction movement of the injection screw, conclusions can now be drawn as to how large the mass cushion is and should be, provided that the non-return valve has closed in good time and is not showing any wear.

If the mass cushion now increases in the second pressure phase (compared to a reference measurement, for example), it can be concluded that the non-return valve is worn, since it obviously allows a higher mass flow to the mass cushion due to the wear during the retraction phase, which means that the mass cushion increases.

Both variants of the invention are based on the fact that wear on the non-return valve can be detected by skillfully controlling the injection screw and observing the position of the injection screw.

The fact that the injection screw is controlled (pressurization or displacement) is of course to be understood as meaning that drives of the injection screw are controlled in such a way that the corresponding pressure application or displacement of the injection screw occurs.

It can preferably be provided that the control or regulating unit is designed to displace the injection screw axially counter to the conveying direction during a second retraction phase and preferably to apply a force axially in the conveying direction during a subsequent third pressure phase in order to apply pressure to the compound cushion exercise. The second withdrawal phase is preferably carried out after the second pressure phase.

For the purposes of the invention, phases being carried out consecutively mean that the phases are carried out directly after one another or that there is a time interval during which optio nal further process steps can be carried out.

It should be noted that the invention is not limited to two or three compression phases or withdrawal phases. In fact, by carrying out a plurality (of compression and retraction phases, that is to say more than two or three retraction phases), the accuracy of the wear detection can be improved according to the second variant of the invention.

Provision can be made for the control or regulating unit to be designed to displace the injection screw by a definable distance axially counter to the conveying direction during the first retraction phase and/or during the second retraction phase. This definable distance can, for example, be freely selectable, in which case a greater measurement accuracy could particularly preferably be provided in terms of measurement technology if the distance by which the injection screw is retracted axially along its longitudinal axis is selected to be greater.

Alternatively or additionally, it can also be provided that the control or regulation unit is designed to move the injection screw during the first retraction phase and/or during the second retraction phase in a definable period of time and/or at a definable speed and/or in a definable movement profile to move axially against the conveying direction.

It is preferably provided that the control or regulation unit is designed to output a signal representative of a response behavior, preferably for axial wear of the non-return valve, based on the measured values of the at least one sensor, with this response behavior, for example in the case of a ring non-return valve, being meaningful for is axial wear.

In the context of the present document, a mass cushion is to be understood as a mass which is present in the injection cylinder when the non-return valve is closed—preferably completely—between the injection screw and a discharge opening of the at least one injection cylinder. The position of the injection screw thus becomes a measure of the volume of the mass cushion that is built up in front of the non-return valve.

It can be provided, for example, that the injection screw can be driven in rotation about its longitudinal axis, with which a plasticization of a material to be plasticized can preferably be carried out. Injection screws, which can be moved axially and in rotation, usually work cyclically, with the plasticizable material first being plasticized by the rotating movement and then pushed out of the at least one injection cylinder by an axial movement and preferably injected into a mold cavity.

It can be provided that the non-return valve is designed as a ring non-return valve, with a blocking ring being movable axially between a first stop position on at least two webs angularly offset with respect to the longitudinal axis and a second stop position on a circumferential pressure ring.

However, the invention can also be used with other types of non-return valves (e.g. ball non-return valves).

• - die Einspritzschnecke axial in Förderrichtung mit einer Kraft zu beaufschlagen, um einen Druck auf den Massepolster aufzubauen und auf Basis der Messwerte des wenigstens einen Sensors auf die sich durch Verschleiß der Rückstromsperre hervorgerufene Verringerung des Massepolsters zu schließen und/oder
• - während einer ersten Druckphase die Einspritzschnecke axial in Förderrichtung mit einer Kraft zu beaufschlagen, um einen Druck auf den Massepolster aufzubauen, die Einspritzschnecke während der anschließenden ersten Rückzugsphase axial entgegen der Förderrichtung zu verschieben, die Einspritzschnecke während der anschließenden zweiten Druckphase axial in Förderrichtung mit einer Kraft zu beaufschlagen, um einen Druck auf den Massepolster aufzubauen und mithilfe des wenigstens einen Sensors die axialen Positionen und/oder die Veränderung zwischen den axialen Positionen der Einspritzschnecke während der ersten Druckphase und der zweite Druckphase zu ermitteln und daraus den Verschleiß der Rückstromsperre zu bestimmen

Provision is preferably made for the injection unit to have at least one injection nozzle, with the control or regulating unit being designed to carry out the following steps when the injection nozzle is closed:

• - apply a force to the injection screw axially in the conveying direction in order to build up pressure on the mass cushion and, on the basis of the measured values of the at least one sensor, to conclude the reduction in the mass cushion caused by wear of the non-return valve and/or
• - during a first pressure phase, to apply a force to the injection screw axially in the conveying direction in order to build up pressure on the mass cushion, to displace the injection screw axially counter to the conveying direction during the subsequent first retraction phase, to axially displace the injection screw in the conveying direction during the subsequent second pressure phase Applying force to build up pressure on the mass cushion and using the at least one sensor to determine the axial positions and/or the change between the axial positions of the injection screw during the first pressure phase and the second pressure phase and from this to determine the wear on the non-return valve

A closed injection nozzle can be produced, for example, by a sprue that has solidified in a previous production cycle. It is also conceivable that shut-off nozzles or the like are used.

It can be provided that the control or regulating unit is designed to reduce the wear of the non-return valve in one to carry out a separate test cycle in the production cycle.

Provision can thus be made for a test cycle to be carried out before or after a production cycle in order to determine wear and tear on the non-return valve. As an alternative or in addition, it can also be provided that the production or the production cycle is interrupted by one or more test cycles, with the non-return valve being checked sporadically or at predetermined times during operation. Particularly preferably, it could also be provided that if there is a deviation in a process parameter (greater or smaller than a specifiable limit value or outside a tolerance range) during a production cycle of the shaping machine (e.g. automatically and/or with the consent of an operator), a change is made to a test cycle in order to Check wear of the non-return valve.

Provision is preferably made for the control or regulating device to be designed to output a message if the wear determined by the control or regulating unit exceeds and/or falls below a definable limit value.

Limit values can be determined, for example, through tests and stored in the control or regulation unit. These limit values can be specified, for example, as ranges in which the measured values may scatter and an acceptable measurement inaccuracy and/or random scatter is taken into account. As an alternative or in addition, these limit values can also be defined via calculations, simulations or also through empirical values. It is also quite conceivable that limit values can be set individually by an operator (for example depending on the area of use of the products). The limit values can be stored in the control or regulation unit as functions, numbers, tolerance bands or also as a graph.

Configurations are also conceivable in which limit values are stored in external storage systems or also, for example, in the analysis unit, with the limit values being able to be called up by the control or regulation unit. It would thus also be possible to change or adapt limit values in an external storage system or the analysis unit independently of the control or regulation unit.

Provision can be made for the control or regulating unit to be designed to output the message in the form of an alarm and/or to output the message in the form of a change in a control signal for the injection unit. A message can, for example, be provided in a wide variety of forms for an operator, an operator or a cooperating control or regulation unit, such as a visual signal, a control signal, digital signals, signals stored in a cloud or the like.

It can be provided that a process parameter, a process time or a process speed is adjusted by the control or regulation unit when a message is present, for example to detect wear and tear on the non-return valve and to take this into account, so that the wear has no effect on the process quality .

Particularly preferably, it can also be provided that the injection unit is shut down when a message is present.

Provision is preferably made for the control or regulating unit to be connected or connectable to a display device for displaying a state of the non-return valve and/or a state of the at least one injection cylinder. It can also be provided that the display device is designed to be structurally separate from the control or regulation unit and is in signal-conducting connection with it.

• - auf Basis der Messwerte des wenigstens einen Sensors auf eine sich durch Verschleiß der Rückstromsperre hervorgerufene Verringerung des Massepolsters zu schließen und/oder
• - aus den axialen Positionen und/oder der Veränderung der axialen Positionen der Einspritzschnecke einen Verschleiß der Rückstromsperre zu bestimmen.

Provision is preferably made for the control or regulation unit to have a control unit and an analysis unit, which are preferably connected to one another via a remote data transmission connection, the analysis unit being designed to

• - to conclude on the basis of the measured values of the at least one sensor a reduction in the mass cushion caused by wear of the non-return valve and/or
• - to determine wear of the non-return valve from the axial positions and/or the change in the axial positions of the injection screw.

It can be provided that the function of the control unit, the evaluation unit, the display device and/or the control or regulation unit is taken over by a central control or regulation unit of the shaping machine. However, it is also possible for the control unit, evaluation unit, display device and/or the control or regulation unit to be connected or connectable to the injection unit via a LAN, WLAN and/or a remote data transmission connection (e.g. Internet). Mixed forms are also conceivable, with certain functions according to the invention of the control unit, evaluation unit and/or open-loop or closed-loop control unit on the shaping machine be realized (eg control of the injection screw) and certain other functions according to the invention (eg calculation of wear) are realized remotely from the molding machine.

Also conceivable is an embodiment in which the control unit, evaluation unit, display unit and/or the control or regulation unit are formed by structurally and/or spatially separate computing units, which computing units are in signal-conducting connection with one another. An embodiment is also conceivable in which resources are shared by the control unit, evaluation unit and/or the control or regulation unit.

For example, it could also be provided that measured values generated by the sensor on the molding machine or the injection unit are processed or evaluated at a central evaluation point (in this context an evaluation unit and/or a control or regulation unit), with a display (e.g. of wear) provided in a portal accessible from anywhere. In the opposite direction, of course, there is also the possibility of sending signals from the central evaluation point to the shaping machine or the injection unit.

Provision can also be made for data for a visualization, ie a screen display or the like for the operator, to be calculated as part of the evaluation. It can be provided, for example, that during an analysis of the control or regulation unit, data for the visualization is calculated, which can then be forwarded to the shaping machine and/or the peripheral device via a data transmission connection and displayed there on a screen for the operator to see can become. These can, for example, visualize the non-return valve and/or wear.

With regard to a method according to the invention for checking at least one injection unit of a molding machine, it can be provided that an injection screw that is mounted in at least one injection cylinder so that it can be displaced axially along a longitudinal axis is subjected to a force in the conveying direction, with an injection screw that is arranged in the at least one injection cylinder and being axially non-moving with an injection screw connected non-return valve, a backflow of a plasticized mass in the at least one injection cylinder against a conveying direction of the injection screw is prevented in order to form a mass cushion in front of the non-return valve, with an axial position of the injection screw being observed during the application of force, with a movement indicative of a reduction in the mass cushion the injection screw indicates wear on the non-return valve.

• - die Einspritzschnecke während einer anschließenden ersten Rückzugsphase axial entgegen der Förderrichtung verschoben wird,
• - die Einspritzschnecke während einer wiederum anschließenden zweiten Druckphase axial in Förderrichtung mit einer Kraft beaufschlagt wird, um einen Druck auf den Massepolster aufzubauen und
• - mithilfe einer Messung axialer Positionen und/oder einer Veränderung zwischen den axialen Positionen während der ersten Druckphase und der zweiten Druckphase ein Verschleiß der Rückstromsperre bestimmt wird.

Alternatively or additionally, in a method according to the invention, it can be provided that an injection screw mounted in at least one injection cylinder so that it can be displaced axially along a longitudinal axis is subjected to a force in the conveying direction, with a backflow being prevented by a non-return valve arranged in at least one injection cylinder and connected to the injection screw in an axially non-moving manner a plasticized mass is prevented in at least one injection cylinder against a conveying direction of the injection screw in order to form a mass cushion in front of the non-return valve, wherein during a first pressure phase the injection screw is subjected to a force axially in the conveying direction in order to build up pressure on the mass cushion, wherein

• - the injection screw is displaced axially against the conveying direction during a subsequent first retraction phase,
• - The injection screw is subjected to a force axially in the conveying direction during a subsequent second pressure phase in order to build up pressure on the mass cushion and
• - Wear of the non-return valve is determined using a measurement of axial positions and/or a change between the axial positions during the first pressure phase and the second pressure phase.

• - eine in wenigstens einem Einspritzzylinder axial entlang einer Längsachse verschiebbar gelagerten Einspritzschnecke zur Beaufschlagung mit einer Kraft in Förderrichtung anzusteuern, um einen Druck auf ein Massepolster aufzubauen, wobei durch eine im wenigstens einen Einspritzzylinder angeordnete und mit der Einspritzschnecke axial entlang der Längsachse bewegungsschlüssig verbundene Rückstromsperre ein Rückströmen einer plastifizierten Masse im wenigstens einen Einspritzzylinder entgegen einer Förderrichtung der Einspritzschnecke verhindert wird, um den Massepolster vor der Rückstromsperre zu bilden, und
• - Messwerte in Bezug auf eine axiale Position der Einspritzschnecke während der Kraftbeaufschlagung entgegenzunehmen und bei einer für eine Verringerung des Massepolsters indikativen Bewegung der Einspritzschnecke auf einen Verschleiß der Rückstromsperre zu schließen.

With regard to a computer program product according to the invention, it can be provided that the computer program product comprises instructions which, when the program is executed by a computer, cause the computer to

• - to control an injection screw, which is mounted in at least one injection cylinder so that it can be displaced axially along a longitudinal axis, for the application of a force in the conveying direction in order to build up pressure on a mass cushion, with a non-return valve arranged in at least one injection cylinder and connected to the injection screw in a non-moving manner along the longitudinal axis Backflow of a plasticized mass is prevented in at least one injection cylinder against a conveying direction of the injection screw in order to form the mass cushion in front of the non-return valve, and
• - Receive measured values in relation to an axial position of the injection screw during the application of force and, in the event of a movement of the injection screw indicative of a reduction in the mass cushion, to conclude wear of the non-return valve.

• - eine in wenigstens einem Einspritzzylinder axial entlang einer Längsachse verschiebbar gelagerten Einspritzschnecke während einer ersten Druckphase zur Beaufschlagung mit einer eine Kraft in Förderrichtung anzusteuern, um einen Druck auf ein Massepolster aufzubauen, wobei durch eine im wenigstens einen Einspritzzylinder angeordnete und mit der Einspritzschnecke axial bewegungsschlüssig verbundene Rückstromsperre ein Rückströmen einer plastifizierten Masse im wenigstens einen Einspritzzylinder entgegen einer Förderrichtung der Einspritzschnecke verhindert wird, um den Massepolster vor der Rückstromsperre zu bilden,
• - die Einspritzschnecke während einer anschließenden ersten Rückzugsphase zur axialen Verschiebung entgegen der Förderrichtung anzusteuern,
• - die Einspritzschnecke während einer wiederum anschließenden zweiten Druckphase zur axialen Beaufschlagung in Förderrichtung mit einer Kraft anzusteuern, um einen Druck auf den Massepolster aufzubauen, und
• - Messwerte in Bezug auf eine axiale Position der Einspritzschnecke entgegenzunehmen und auf Basis axialer Positionen und/oder einer Veränderung zwischen den axialen Positionen während der ersten Druckphase und der zweite Druckphase einen Verschleiß der Rückstromsperre zu bestimmen.

Alternatively or additionally, in a computer program product according to the invention, it can be provided that the computer program product comprises instructions which, when the program is executed by a computer, cause the computer to

• - to control an injection screw mounted in at least one injection cylinder so that it can be displaced axially along a longitudinal axis during a first pressure phase for the application of a force in the conveying direction in order to build up pressure on a mass cushion, with an injection screw arranged in at least one injection cylinder and connected to the injection screw in an axially non-moving manner non-return valve prevents a plasticized mass from flowing back in the at least one injection cylinder against a conveying direction of the injection screw, in order to form the mass cushion in front of the non-return valve,
• - to control the injection screw during a subsequent first retraction phase for axial displacement against the conveying direction,
• - driving the injection screw during a subsequent second pressure phase for axial loading in the conveying direction with a force in order to build up pressure on the mass cushion, and
• - to receive measured values in relation to an axial position of the injection screw and to determine wear of the non-return valve on the basis of axial positions and/or a change between the axial positions during the first pressure phase and the second pressure phase.

• 1 ein erstes Ausführungsbeispiel einer Rückstromsperre,
• 2 ein zweites Ausführungsbeispiel einer Rückstromsperre,
• 3 ein beispielhaftes Messergebnis,
• 4 ein drittes Ausführungsbeispiel einer Rückstromsperre,
• 5 ein viertes Ausführungsbeispiel einer Rückstromsperre,
• 6 ein beispielhaftes Messergebnis,
• 7 eine Formgebungsmaschine und
• 8 ein Ausführungsbeispiel einer Anordnung aus einer Formgebungsmaschine und einer Berechnungseinheit.

Further advantages and details of the invention result from the figures and the associated description of the figures. show:

• 1 a first embodiment of a non-return valve,
• 2 a second embodiment of a non-return valve,
• 3 an example measurement result,
• 4 a third embodiment of a non-return valve,
• 5 a fourth embodiment of a non-return valve,
• 6 an example measurement result,
• 7 a shaping machine and
• 8th an embodiment of an arrangement of a shaping machine and a calculation unit.

1 shows a first embodiment of a non-return valve 6, which is designed as a ring non-return valve.

The annular non-return valve is arranged at a front axial end of an injection screw 5 , the non-return valve 6 being connected to the injection screw 5 in an axially non-moving manner along the longitudinal axis 4 of the injection screw 5 .

The non-return valve 6 has a locking ring 9 which can be positioned axially between a first stop position (as in 1 shown), in which the locking ring 9 rests against the angularly offset webs 10 of the non-return valve, and a second stop position (as in 2 shown), in which the locking ring 9 rests against a peripheral pressure ring 11, is movable.

The injection screw 5 is arranged together with the non-return valve 6 inside the injection cylinder 3, which is closed in a front area by the flange 17.

The flange 17 also carries an injection nozzle 12, which is only symbolically indicated here. It would be possible, for example, to use a needle shut-off nozzle which can be opened or closed actively (for example via actuation using a control or regulating unit 7). In the present exemplary embodiment, the injection nozzle 12 is closed via a solidified sprue.

During production by means of the shaping machine 2, a material to be plasticized is now plasticized via a rotational movement of the injection screw 5, which in this exemplary embodiment also serves for plasticizing.

The plasticized material is then conveyed by the injection screw 5 via the locking ring 9 in a first stop position (more precisely: through the locking ring 9) and via the webs 10 into the screw antechamber 14.

In a subsequent injection movement, the injection nozzle 12 is opened and the injection screw 5 moves along its conveying direction (in 2 indicated by the arrow) in the direction of the injection nozzle 12, with a pressure building up in the screw antechamber 14, which pushes the locking ring 9 into a second stop position, in which the locking ring 9 bears against the pressure ring 11.

In this second stop position of the locking ring 9 , the plasticized mass is prevented from flowing back in the injection cylinder 3 against the conveying direction of the injection screw and a mass cushion is built up in the screw antechamber 14 in front of the injection screw 5 .

When the injection nozzle 12 is open, the mass cushion would be pushed out of the screw antechamber 14, i.e. the plasticized mass in the screw antechamber 14 would be discharged in the conveying direction via the axial movement of the injection screw 5 along the longitudinal axis 4 and fed via the injection nozzle 12, for example, to a mold 20 of a molding machine 2.

Since the locking ring 9 of the non-return valve 6 is subject to friction - among other things between the inner surface of the injection cylinder 3 and the radial outer surface of the locking ring 9 - radial wear 18 occurs as a result of the formation of a gap 15 .

This radial wear 18 means that the non-return valve no longer seals completely in a second stop position, as well as through the 2 can be seen.

In order to detect this radial wear 18 according to the invention, it can be provided that when the injection nozzle 12 is closed, a pressure is built up on a mass cushion present in the screw antechamber 14 via an axial movement of the injection screw 5 along the longitudinal axis 4 and via a position sensor 8 of the injection screw 5 the position of the injection screw 5 is observed.

This procedure can be carried out with the injection nozzle 12 closed for better and simpler metrological detection.

Such an exemplary measurement method is in 3 shown.

So shows 3 a measurement of the axial position of the injection screw 5, with the injection screw 5 being subjected to a force axially in the conveying direction at a point in time t ₀ , with the non-return valve 5 closing first and then a mass cushion being formed in the screw antechamber 14 until the mass cushion is removed by the impact of the Force is loaded with a defined pressure via the injection screw 5 and an equilibrium of forces is established, as shown in the curve in 3 can be seen (start of the time span Δt).

It can also be seen that the measurements were carried out with the injection nozzle 12 closed and the antechamber 14 thus sealed off.

As shown in this diagram, the test was carried out with an intact non-return valve 6, which can be recognized by the solid black line, and with a worn non-return valve 6, which is represented by the dashed line.

It can be seen that the intact non-return valve 6 seals after the application of force and formation of the mass cushion, with the injection screw 5 remaining in its position x ₁ for the period of time Δt, whereas the worn non-return valve 6 does not seal completely and plasticized material from the screw antechamber continues to flow contrary to the The conveying direction of the injection screw 5 exits, resulting in a movement of the injection screw 5 by Δx in the time period Δt.

Wear of the non-return valve can now be determined by this measuring method, whereby even a size of the wear can be calculated, for example, using the following formula: $$v_{ScHnecke}=a_0\frac{A_0}{{\mathrm{<figure-callout\; id="2"\; label="A\; S"\; filenames="DE102022112316A1\_0007.png,DE102022112316A1\_0008.png"\; state="\{\{state\}\}">A</figure-callout>}}_S}\sqrt{\frac{2}{\rho }\left({\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="DE102022112316A1\_0006.png"\; state="\{\{state\}\}">p</figure-callout>}}_1-p_2\right)}$$

über das Verhältnis A₀ zu A_s (wobei A_s die innere Querschnittsfläche des Plastifizierzylinders darstellt und A₀ den Blendenquerschnitt der Sperre) der vorliegende Blendenquerschnitt berechnet werden. Das Druckgefälle (p₁-p₂) zwischen den Punkten vor und nach der Rückstromsperre 5 ist dabei als bekannte Größe aus der Messung einzusetzen.So can about the screw speed ${\text{v}}_{\text{Snail}}\left(=\frac{\Delta \text{x}}{\Delta \text{t}}\right)$

The existing orifice cross-section can be calculated via the ratio A ₀ to A _s (where A _s represents the inner cross-sectional area of the plasticizing cylinder and A ₀ represents the orifice cross-section of the barrier). The pressure drop (p ₁ -p ₂ ) between the points before and after the non-return valve 5 is to be used as a known variable from the measurement.

The density ρ and the substance-specific density flow coefficient α ₀ represent known material quantities.

This calculation can even be used to calculate an (at least average) gap size of the gap 15 between the non-return valve 6 and the inner surface of the plasticizing cylinder 3 - since it can be assumed that the non-return valve 5 is coaxial with the inner surface of the plasticizing cylinder 3.

4 shows a further exemplary embodiment of a non-return valve 6, the area of axial wear of the non-return valve 6 being shown in a detailed view. Here is in 4 an intact non-return valve 6 shown and in 5 a worn one.

So it can be seen how in the 4 and 5 the blocking ring 9 of the non-return valve 6 is in a first stop position, with the blocking ring 9 resting against the webs 10 of the non-return valve 6 and a flow cross-section 16 being released in a rear region of the blocking ring 9, so that material plasticized by the injection screw 5 can flow through the flow cross-section 16 and can be fed to the screw antechamber 14 in the front area via the webs 10 .

Due to the high prevailing pressures and a rotational movement of the plasticized mass caused by the plasticization, the locking ring 9 is pressed against the webs 10 with high forces, the locking ring 9 at the same time mostly performing a rotational movement which is caused by the flow of the plasticized mass.

This application of the locking ring 9 to the web 10 paired with the relative movement of the locking ring 9 to the webs 10 (due to the rotational movement) leads to abrasion on the webs 10 and the locking ring 9, which leads to axial wear of the non-return valve 6.

Furthermore, wear is also caused in the second stop position of the locking ring 9, in which the locking ring 9 is pressed against the pressure ring 11 of the non-return valve 6, which (albeit to a lesser extent) influences the axial wear of the non-return valve 6.

If now the axial wear of the non-return valve 6 increases, the closing times of the non-return valve change, since the blocking ring 9 has to cover a greater distance, resulting in inaccuracies in the ongoing process of the shaping machine.

Furthermore, as is clear from the difference between 4 and 5 it can be seen that the axial wear increases the flow cross section 16.

Given constant process parameters of the molding machine 2 , this enlargement of the flow cross section 16 leads to an increase in the mass cushion and thus in the plasticized mass that is injected or fed to a mold 20 . This increasing enlargement thus has a direct influence on the process quality of the shaping machine 2.

Such axial wear can now be compensated for by a determination as in 6 using a diagram shown as an example, a mass cushion being built up in the screw antechamber 14 and being subjected to an axial movement along the longitudinal axis 4 of the injection screw 5 via the injection screw 5 with a force so that the non-return valve 6 closes.

If the non-return valve 6 is now closed and the mass cushion is pressurized with the force via the injection screw 5, an axial position of the injection screw 5 can be measured, which is indicative of the size of the mass cushion.

The injection screw 5 is then retracted by a defined length counter to the conveying direction in a retraction phase and thus the mass cushion with further plasticized mass (which flows into the screw antechamber 14 when the non-return valve 6 is open) is enlarged.

After the withdrawal by a defined time or length, pressure is again exerted on the enlarged mass cushion in a pressure phase via a force along the conveying direction and the longitudinal axis 4 with the injection screw 5 and again during the pressure phase with the help of a position of the injection screw 5 a size of the mass cushion determined. This procedure can be repeated as often as you like.

This procedure can now be used to determine whether there is axial wear on a non-return valve 6, with the mass cushion also increasing as a result of the increase in axial wear, since the flow cross section 16 has increased.

So is in 6 to see how the measured values of intact non-return valves (identified by ΔV ₁ ) differ significantly from a measured value of a worn non-return valve (identified by ΔV ₂ ).

7 shows a molding machine 2 with an injection unit 1, the injection unit 1 shown in this exemplary embodiment having an injection screw 5, which is also used to plasticize a material to be plasticized (and thus also forms the plasticizing unit 19 of the molding machine).

The injection screw 5 is mounted in the injection cylinder 3 so that it can be displaced axially along a longitudinal axis 4 .

The injection screw 5 is axially connected to the non-return valve 6 so that it cannot move, in order to be able to form a mass cushion in front of the non-return valve 6 and to prevent a plasticized mass from flowing back in at least one injection cylinder 3 against a conveying direction of the injection screw 5 .

In the 7 The molding machine 2 shown has an injection unit 1 and a clamping unit 21 which are arranged together on a machine frame 22 .

The clamping unit 21 has a stationary platen 23 , a movable platen 24 and a face plate 25 .

In contrast to the horizontal three-platen machine shown, the clamping unit 21 could also be designed as a two-platen machine or as a vertical machine.

The movable platen 24 can be moved relative to the machine frame 22 via a drive device 26 . Such a drive device 26 can have a toggle lever mechanism, for example.

Mold halves of a shaping tool 20 can be clamped or mounted on the fixed platen 23 and the movable platen 24 (shown in phantom).

This in 7 Shaping tool 20 shown closed has at least one cavity. An injection channel leads to the cavity, via which a plasticized mass of the plasticizing unit 19 can be supplied.

The injection unit 1 of this exemplary embodiment has an injection cylinder 3 and an injection screw 5 arranged on the injection cylinder 3 . This injection screw 5 can be rotated about its longitudinal axis 4 and can be moved axially along the longitudinal axis 4 in the conveying direction.

These movements are driven by a drive unit 27 shown schematically. This drive unit 27 preferably comprises a rotary drive for the rotary movement and a linear drive for the axial injection movement.

The plasticizing unit 19 (and thus the injection unit 1) is connected to a control or regulating unit 7 in terms of signals. Control commands are issued to the plasticizing unit 19 by the control or regulating unit 7 .

The control or regulation unit 7 can be connected to an operating unit and/or a display device 13 or can be an integral part of such an operating unit.

8th shows an exemplary embodiment of an arrangement made up of a shaping machine 2, which is designed as an injection molding machine in this exemplary embodiment, and a calculation unit 28, with the calculation unit 28 being implemented as a central server 29 (e.g. cloud server) which accesses publicly usable servers 29.

The calculation unit 28 shown in this exemplary embodiment can, for example, take over the function of the control or regulation unit 7 . However, it could also be provided that the function of the control or regulation unit 7 is taken over by the machine control 35 .

The shaping machine 2 is connected to the central server 29 via a data transmission unit 30, the data transmission unit 30 having a data transmission connection 31, an edge computing device 32 and a firewall 33.

The symbol of the firewall 33 is intended to clarify measures which serve in particular for information security and machine security and take into account the fact that the calculation unit 28 is not in the direct sphere of influence of the operator of the shaping machine 2 . A firewall 33 is of course part of such measures.

The edge computing device 32 directs central data from the shaping machine 2 to a calculation unit 28 and from there back to the shaping machine 2.

An additional operator portal 34 can be provided, which is connected to the central server 29 . This enables an operator to access the calculation unit 28 via the central server 29 and thus to process data of the shaping machine 2 from any device that allows the portal 34 to be called up to take over or to trigger them via the portal 34 can be provided.

reference list

1

injection unit

2

shaping machine

3

injection cylinder

4

longitudinal axis

5

injection screw

6

non-return valve

7

control or regulation unit

8th

sensor

9

locking ring

10

web

11

pressure ring

12

injector

13

display device

14

snail vestibule

15

gap

16

flow cross-section

17

flange

18

radial wear

19

plasticizing unit

20

molding tool

21

locking unit

22

machine frame

23

fixed platen

24

movable mold platen

25

faceplate

26

drive device

27

drive unit

28

calculation unit

29

central server

30

data transfer unit

31

data transmission connections

32

Edge computing device

33

firewall

34

operator portal

35

machine control

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was 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.

Patent Literature Cited

• EP 2000281 A1 [0012]
• DE 102017004374 A1 [0012]
• DE 102019128177 A1 [0014]
• DE 102018007641 A1 [0014]
• AT 521585 A1 [0015]

Claims (20)

Injection unit for a molding machine (2) comprising - at least one injection cylinder (3), - an injection screw (5) mounted to be displaceable axially along a longitudinal axis (4) in at least one injection cylinder (3), - an injection screw (5) arranged in at least one injection cylinder (3) and non-return valve (6) connected to the injection screw (5) so that it can move axially, in order to prevent a backflow of a plasticized material in at least one injection cylinder (3) against a conveying direction of the injection screw (5) in order to form a mass cushion in front of the non-return valve (6), - at least a control or regulating unit (7) which is designed to control or regulate an axial movement of the injection screw (5) and - at least one sensor (8) for determining an axial position of the injection screw (5), the axial position the injection screw (5) is a measure of the volume of the mass cushion, the at least one control or regulating unit t (7) is designed to apply a force to the injection screw (5) axially in the conveying direction in order to build up pressure on the mass cushion, characterized in that the control or regulating unit (7) is designed to do this on the basis of the measured values of the at least one sensor (8) to conclude that there is a reduction in the mass cushion caused by wear of the non-return valve (6). injection unit claim 1 , wherein the control or regulating unit (7) is designed to output a signal representative of the tightness of the non-return valve (6) on the basis of the measured values of the at least one sensor (8). Injection unit according to one of the preceding claims, wherein the control or regulating unit (7) is designed to, on the basis of the measured values of the at least one sensor (8), a radial wear of the non-return valve (6), preferably a distance between an inner surface of the at least one Injection cylinder (3) and the non-return valve (6) arranged therein. Injection unit for a molding machine (2), in particular according to one of the preceding claims, comprising - at least one injection cylinder (3), - an injection screw (5) mounted in the at least one injection cylinder (3) so that it can be displaced axially along a longitudinal axis (4), - an in at least one injection cylinder (3) and which is connected to the injection screw (5) in an axially non-moving manner (5), - at least one control or regulating unit (7) which is designed to control or regulate an axial movement of the injection screw (5) and - at least one sensor (8) for determining an axial position of the injection screw (5), wherein the at least one control or regulation unit (7) is designed to, during a first en pressure phase to apply a force to the injection screw (5) axially in the conveying direction in order to build up pressure on the mass cushion, characterized in that the control or regulating unit (7) is designed to - the injection screw (5) during a subsequent first to shift the retraction phase axially counter to the conveying direction, - to apply a force to the injection screw (5) during a subsequent second pressure phase axially in the conveying direction in order to build up pressure on the mass cushion, and - with the aid of the at least one sensor (8), axial positions and /or to determine a change between the axial positions of the injection screw (5) during the first pressure phase and the second pressure phase and to determine wear on the non-return valve (6) therefrom. injection unit claim 4 , wherein the control or regulating unit (7) is designed to displace the injection screw (5) axially against the conveying direction during a second retraction phase and preferably to apply a force axially in the conveying direction during a subsequent third pressure phase in order to apply pressure to build up the mass cushion. injection unit claim 4 or 5 wherein the control or regulating unit (7) is designed to move the injection screw (5) during the first retraction phase and/or the second retraction phase by a predeterminable distance axially counter to the conveying direction. Injection unit according to at least one of Claims 4 until 6 , wherein the control or regulating unit (7) is designed to output a signal representative of a response behavior, preferably for axial wear, of the non-return valve (6) on the basis of the measured values of the at least one sensor (8). Injection unit according to at least one of the preceding claims, wherein the non-return valve (6) is designed as a ring non-return valve, with a locking ring (9) axially between a first stop position at at least two in Relative to the longitudinal axis angularly offset webs (10) and a second stop position on a rotating pressure ring (11) is movable. Injection unit according to at least one of the preceding claims, wherein the injection unit (1) has at least one injection nozzle (12), the control or regulating unit (7) being designed to carry out the following steps when the injection nozzle (12) is closed: - apply a force axially to the injection screw (5) in the conveying direction in order to build up pressure on the mass cushion and, on the basis of the measured values of the at least one sensor (8), to conclude the reduction in the mass cushion caused by wear of the non-return valve (6). and or - to apply a force to the injection screw (5) axially in the conveying direction during a first pressure phase in order to build up pressure on the mass cushion, to displace the injection screw (5) axially counter to the conveying direction during the subsequent first retraction phase, to displace the injection screw (5) during to apply a force axially in the conveying direction during the subsequent second pressure phase in order to build up pressure on the material cushion and, with the aid of the at least one sensor (8), to determine the axial positions and/or the change between the axial positions of the injection screw (5) during the first pressure phase and to determine the second pressure phase and from this to determine the wear of the non-return valve (6). Injection unit according to at least one of the preceding claims, characterized in that the control or regulating unit (7) is designed to check the wear of the non-return valve (6) in a test cycle separate from a production cycle. Injection unit according to at least one of the preceding claims, characterized in that the control or regulation unit (7) is designed to issue a message if the wear determined by the control or regulation unit (7) exceeds and/or falls below a predeterminable limit value. injection unit claim 11 , characterized in that the control or regulating unit (7) is designed to output the message in the form of an alarm and/or to output the message in the form of a change in a control signal for the injection unit (5). Injection unit according to at least one of the preceding claims, characterized in that the control or regulating unit (7) is connected to a display device (13) for displaying a state of the non-return valve (6) and/or a state of the at least one injection cylinder (5) or is connectable. Injection unit according to at least one of the preceding claims, characterized in that the control or regulating unit (7) has an activation unit and an analysis unit, which are preferably connected to one another via a remote data transmission connection, the analysis unit being designed to - on the basis of the measured values of the at least a sensor (8) to detect a reduction in the mass cushion caused by wear of the non-return valve (6) and/or - from the axial positions and/or the change in the axial positions of the injection screw (5) to infer wear of the non-return valve (6). determine. Molding machine with at least one injection unit (1) according to at least one of the preceding claims. Method for checking at least one injection unit (1) of a molding machine (2), preferably according to one of Claims 1 until 14 , wherein an injection screw (5) which is mounted in at least one injection cylinder (3) so that it can be displaced axially along a longitudinal axis (4) is subjected to a force in the conveying direction, with an injection screw (5) arranged in at least one injection cylinder (3) and a non-return valve (6) connected in an axially non-locking manner to prevent a backflow of a plasticized mass in at least one injection cylinder (3) against a conveying direction of the injection screw (5) in order to form a mass cushion in front of the non-return valve (6), characterized in that an axial position of the Injection screw (5) is observed during the application of force, with indicative of a reduction in the mass cushion movement of the injection screw (5) wear of the non-return valve (6) is concluded. Method for checking at least one injection unit (1) of a molding machine (2), preferably according to one of Claims 1 until 14 , wherein an injection screw (5) which is mounted in at least one injection cylinder (3) so that it can be displaced axially along a longitudinal axis (4) is subjected to a force in the conveying direction, with an injection screw (5) arranged in the at least one injection cylinder (3) being axially non-return valve (6) connected in a non-moving manner, a backflow of a plasticized mass in at least one injection cylinder (3) against a conveying direction of the injection screw (5) is prevented, around a mass pole ter before the non-return valve (6), wherein during a first pressure phase the injection screw (5) is subjected to a force axially in the conveying direction in order to build up pressure on the material cushion, characterized in that - the injection screw (5) during a subsequent is displaced axially counter to the conveying direction during the first retraction phase, - during a subsequent second pressure phase, a force is applied axially in the conveying direction to the injection screw (5) in order to build up pressure on the mass cushion, and - with the aid of a measurement of axial positions and/or a change wear of the non-return valve (6) is determined between the axial positions during the first pressure phase and the second pressure phase. Computer program product, comprising instructions that cause a computer to run the program, - to control an injection screw (5) which is mounted in at least one injection cylinder (3) so that it can be displaced axially along a longitudinal axis, for the application of a force in the conveying direction, in order to build up pressure on a mass cushion, with an injection screw (5 ) a non-return valve (6) connected axially along the longitudinal axis (4) in a non-moving manner to prevent a backflow of a plasticized mass in at least one injection cylinder (3) against a conveying direction of the injection screw (5) in order to form the mass cushion in front of the non-return valve (6), and - Receive measured values in relation to an axial position of the injection screw (5) during the application of force and, in the event of a movement of the injection screw (5) indicative of a reduction in the mass cushion, to conclude wear of the non-return valve (6). Computer program product, comprising instructions that cause a computer to run the program, - an injection screw (5) which is mounted in at least one injection cylinder (3) so that it can be displaced axially along a longitudinal axis (4) during a first pressure phase for the application of a force in the conveying direction, in order to build up pressure on a mass cushion, with an injection screw (5) in the at least one backflow stop (6) arranged in the injection cylinder (3) and connected to the injection screw (5) so that it can move axially, a backflow of a plasticized mass in at least one injection cylinder (3) against a conveying direction of the injection screw (5) is prevented in order to prevent the mass cushion in front of the backflow stop (6 ) to build, - to control the injection screw (5) during a subsequent first retraction phase for axial displacement against the conveying direction, - to control the injection screw (5) during a subsequent second pressure phase for axial loading in the conveying direction with a force in order to build up pressure on the mass cushion, and - to receive measured values in relation to an axial position of the injection screw (5) and to determine wear of the non-return valve (6) on the basis of axial positions and/or a change between the axial positions during the first pressure phase and the second pressure phase. Computer-readable storage medium on which a computer program product Claim 18 and/or 19 is stored.

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