DE102022134640A1 - Print head unit and method for layer-by-layer construction of molded parts - Google Patents

Abstract

The invention relates to a system for applying a printing fluid comprising a print head unit (101) comprising an arrangement of printing modules (102) and a pressure fluctuation compensation module (106), characterized in that the print head and the pressure fluctuation compensation module (106) are coupled, and to a method for producing models using the above-mentioned system.

Description

The invention relates to a print head unit and its use in a method for producing three-dimensional models by means of layer build-up technology.

In the European patent specification EP 0 431 924 B1 describes a method for producing three-dimensional objects from computer data. A thin layer of particle material is applied to a construction platform using a recoater, and the particle material (generally fluid) is selectively printed with a binder material using a print head. The particle area printed with the binder bonds and solidifies under the influence of the binder and, if necessary, an additional hardener. The construction platform is then lowered by one layer thickness in a construction cylinder and provided with a new layer of particle material, which is also printed as described above. These steps are repeated until a certain, desired height of the object is reached. A three-dimensional object (molded part) is created from the printed and solidified areas.

This object, made from solidified particle material, is embedded in loose particle material after its completion and is then freed from it. This is done using a vacuum cleaner, for example. What remains is the desired objects, which are then freed from the remaining powder, for example by brushing.

In known print heads or systems with multiple components in printing systems for building models layer by layer, the printing fluid is often not distributed evenly and uniformly. Problems arise, particularly due to the moment of inertia during the movement processes, and the delivery of the printing fluid or its availability at the nozzles can be disrupted.

It was therefore an object of the present invention to reduce or completely avoid the disadvantages of the prior art.

It was therefore a further object of the present invention to provide a system in which the pressure fluid is present substantially uniformly in each subunit and/or can be present and/or dispensed at the same pressure.

Brief summary of the invention

In one aspect, the invention relates to a system for applying a printing fluid comprising a print head unit (101) comprising an arrangement of printing modules (102) and a pressure fluctuation compensation module (106), characterized in that the print head and the pressure fluctuation compensation module (106) are coupled.

In one aspect, the invention relates to a pressure fluctuation compensation module.

In one aspect, the invention relates to a method for producing 3D molded parts in which all known steps of an additive printing process are carried out and in which a system as described above is used.

Short description of the characters

• 1 shows an aspect of the invention, which represents a print head unit 101, which is essentially characterized in that an arrangement of printing modules 102 are connected to a circulating pressure fluid supply by means of pressure fluid connection lines 105 via pressure homogenization elements 103 and 104.
• 2a illustrates an example of an aspect of the invention which is a pressure fluctuation compensation module.
• 2 B illustrates an example of an aspect of the invention which represents another pressure fluctuation compensation module.
• 3 shows an example of an aspect of the invention, illustrating the fluid supply of the print head unit with the included print modules.
• 4 shows an example of a system according to the invention in which a cleaning fluid can be used.

Detailed description of the invention

According to the invention, an object underlying the application is achieved by a system according to claim 1 and/or by a pressure fluctuation compensation module according to claim 16 and/or by a printing device according to claim 20 and/or by a method according to claim 21. Further preferred aspects are described in the subclaims.

In the following, some terms of the revelation will be explained in more detail.

For the purposes of the disclosure, “layer construction processes” or “3D printing processes” or “3D processes” or “3D printing” are all processes known from the prior art that enable the construction of components in three-dimensional shapes and that can be used with the processes described below. components and devices are compatible.

“Binder jetting” in the sense of the disclosure means that powder is applied layer by layer to a construction platform, the cross sections of the component on this powder layer are printed with one or more liquids, the position of the construction platform is changed by one layer thickness from the last position and these steps are repeated until the component is finished. Binder jetting also refers to layer construction processes that require an additional process component such as layer-by-layer exposure, e.g. with IR or UV radiation.

In the "high-speed sintering process" as defined in the disclosure, a thin layer of plastic granulate, such as PA12 or TPU, is applied to a construction platform (construction field), which is preferably heated. An inkjet print head then moves over a large area of the platform and wets the areas of the construction field with electromagnetic radiation, e.g. infrared light-absorbing ink (absorber), where the prototype is to be created. The construction platform is then irradiated with (e.g. infrared) light. The wetted areas absorb the heat, causing it to melt and bond with the underlying powder layer. The unprinted powder, however, remains loose. After sintering, the construction platform lowers by one layer thickness. This process is repeated until the construction of a component is complete. The sintered parts are then cooled in a controlled manner in the construction space before they can be removed and unpacked. In one variation, a so-called detailing agent can be printed in addition to the absorber, which serves to cool the areas printed with it. A variant of the high-speed sintering process is also called |Fusion-Jet process|[CS1]|[CS2], where the print head sprays a heat-absorbing liquid (often referred to as a "fusing agent", which corresponds to the absorber) onto a layer of the particle material. Immediately after printing, a heat source (infrared light) is used. The areas to which the "fusing agent" was applied are heated more than the powder without this liquid. This way, the required areas are fused together. A further additive is then used, which is also called a "detailing agent" and is used for insulation. This selective impression is made around the areas on which the "fusing agent" or absorber" was printed. This additive is intended to promote sharp edge formation. This goal is to be achieved by making the temperature differences between the printed and unused powder more significant. Such a process can also include processes known as multijet fusion or selective absorption sintering.

“Laser sintering process” within the meaning of the disclosure is a 3D printing process in which the particulate material is selectively solidified by means of a laser.

“3D molded part”, “molded body” or “component” within the meaning of the disclosure are all three-dimensional objects produced by means of the method according to the invention and/or the device according to the invention which have dimensional stability.

“Build space” is the geometric location in which the particulate material fill grows during the build process by repeated coating with particulate material or through which the fill passes in the case of continuous principles. In general, the build space is limited by a floor, the build platform, by walls and an open top surface, the build level. In the case of continuous principles, there is usually a conveyor belt and limiting side walls. The build space can also be designed by a so-called job box, which is a unit that can be moved in and out of the device and allows batch production, whereby a job box is moved out after the process has been completed and a new job box can be moved into the device immediately, so that the production volume and thus the device performance is increased.

All flowable materials known for 3D printing can be used as “building material” or “particle material” or “powder” or “powder fill” within the meaning of the disclosure, in particular in powder form, as a slip or as a liquid. These can be, for example, sand, ceramic powder, glass powder, and other powders made of inorganic or organic materials such as metal powder, plastics, wood particles, fiber materials, cellulose and/or lactose powder as well as other types of organic, powdery materials. The particle material is preferably a dry, free-flowing powder, but a cohesive, cut-resistant powder can also be used. This cohesiveness can also result from the addition of a binder material or an auxiliary material such as a liquid. The addition of a liquid can lead to the particle material in the form of a slip being freely flowable. In general, particle material within the meaning of the disclosure can also be referred to as fluids.

In the present application, particulate material and powder are used synonymously.

The “particle material application” is the process of creating a defined layer of powder. This can be done either on the build platform (build field) or on an inclined plane relative to a conveyor belt in the case of continuous principles. The application of particulate material is also referred to as "coating" or "recoating".

"Selective liquid application" or "selective binder application" can be carried out in the sense of the disclosure after each application of particle material or, depending on the requirements of the molded body and in order to optimize the molded body production, also irregularly, for example several times in relation to one application of particle material. In this case, a cross-sectional image through the desired body is printed.

Any known 3D printing device that includes the required components can be used as a "device" for carrying out a method according to the disclosure. Common components include coaters, build field, means for moving the build field or other components in continuous processes, job boxes, dosing devices and heating and irradiation means and other components known to those skilled in the art, which are therefore not described in more detail here.

The "building material" according to the disclosure is always applied in a "defined layer" or "layer thickness" which is individually adjusted depending on the building material and process conditions. It is, for example, 0.05 to 5 mm, preferably 0.07 to 2 mm.

A "coater blade" within the meaning of the disclosure is a substantially flat metallic component or one made of another suitable material that is located at the outlet opening of the coater and through which the fluid is released onto the construction platform and smoothed out. A coater can have one or two or more coater blades. A coater blade can be an oscillating blade that performs oscillations in the sense of a rotary movement when it is excited. Furthermore, this oscillation can be switched on and off by a means for generating oscillations. Depending on the arrangement of the outlet opening, the coater blade within the meaning of the disclosure is arranged "substantially horizontally" or "substantially vertically".

“Coolant” as used in the disclosure is a means capable of cooling a radiator unit or a fluid dispensing means, for example by means of water or another liquid or a gas blower stream.

The "heating phase" in the sense of the disclosure characterizes a heating of the device at the beginning of the method. The heating phase is completed when the actual temperature of the device reaches a steady-state value.

The "cooling phase" in the sense of the disclosure refers to the time required to cool the particle material so that the components contained therein do not experience any noticeable plastic deformation when removed from the construction space, or the "cooling time" in the sense of the disclosure is the period of time that must be waited for before molded bodies produced by the sintering process can be removed from the construction space without being damaged. The cooling time is usually the minimum time required when the outside of the construction space is cooled to the maximum and is usually specified in such a way that the hottest place in the construction space volume is safely below the heat distortion temperature of the material used.

The "absorber" or "IR absorber" in the sense of this disclosure is a medium that can be processed with an inkjet print head or with another device that works in a matrix-like manner and that promotes the absorption of radiation for local heating of the building material. The absorber can also be in particle form, such as black toner. Absorbers can be applied uniformly or selectively in different amounts. The absorber can be applied, for example, as a mixture of absorbers with different absorption maxima, or different absorbers can be applied independently of one another, e.g. one after the other, alternately or in a predetermined sequence. When applied in different amounts, the strength in the building material can thus be controlled and different strengths can be achieved selectively, for example in the molded part to be produced and the casing surrounding it. The range of strength extends from a strength like that of the component itself to a strength that is only insignificantly higher than that of the building material without an absorber print. This makes it possible to regulate the temperature in the construction area/construction space and, if desired, to easily remove the jacket used for temperature regulation around the manufactured component.

“Absorption” in the sense of this disclosure refers to the absorption of thermal energy from radiation by the building material. Absorption depends on the type of absorber and/or powder and the wavelength of the radiation.

“Energy input means” in the sense of this disclosure means a source for inputting energy into the construction space and/or the particle material and/or the areas printed with absorbers. This can be, for example, an energy source for tempering or heating particle material, even before the absorber is introduced. However, it could also be an irradiation of the construction area with fixed or movable radiation sources. If the If a radiation source is used for solidification after the absorber has been introduced, the absorber is preferably matched to the type of radiation and preferably optimized. This should result in different levels of heating of "activated" and non-"activated" powder. "Activated" means that the absorber impression increases the temperature in these areas compared to the other areas in the build space and the particle material areas not printed with absorber.

In the context of this disclosure, "IR heating" specifically means irradiation of the construction area with an IR radiator. The IR radiator can be static or moved over the construction area using a moving unit. By using the absorber, the IR heating in the construction area leads to temperature increases of varying degrees.

An "IR radiator" within the meaning of this disclosure is a source of infrared radiation. Glowing wires in quartz or ceramic housings are usually used to generate the radiation. Depending on the materials used, different wavelengths of radiation result. The wavelength of this type of radiator also depends on the power.

An "overhead lamp" or "overhead radiator" or "radiator unit" or "radiator unit" or "radiation unit" or "radiant heater" or "construction field heater" in the sense of the disclosure is a radiation source that is mounted above the construction field. The wavelength of the emitted electromagnetic radiation is stationary and its radiation output can be regulated. It is a unit that emits electromagnetic radiation of a specific spectrum. It can contain individual radiators or a number of radiators. It can optionally cover essentially the entire construction field and be mounted at one position in the device, or it can be smaller than the construction field and can be movable across the construction field.

"Sintering" or "melting" in the sense of this disclosure is the term for the partial coalescence of the particles in the powder. In this system, sintering is associated with the build-up of strength.

For the purposes of this disclosure, the term “sintering window” refers to the difference in temperature between the melting point occurring when the powder is first heated and the solidification point occurring during subsequent cooling.

For the purposes of this disclosure, the “sintering temperature” is the temperature at which the powder first melts and bonds.

"Edge area" within the meaning of the disclosure is the area of a radiator unit that is located at the edge of the radiator unit and can be separated from the interior area. The edge area and interior area form the total area of the radiator unit in terms of its surface on which the radiator units are mounted.

“Interior area” within the meaning of the disclosure is the area of a radiator unit that is located inside the radiator unit and can be demarcated from the edge area.

“3D printer” or “printer” or “3D printing machine” within the meaning of the disclosure refers to the device in which a 3D printing process can take place. A 3D printer within the meaning of the disclosure has an application means for building material, e.g. a fluid such as a particle material, and a solidification unit, e.g. a print head or an energy input means such as a laser or a heat lamp. Other machine components known to the person skilled in the art and components known in 3D printing are combined with the machine components mentioned above depending on the specific requirements in the individual case. Alternatively, the term “device” can be chosen.

“Construction area” is the level or, in a broader sense, the geometric location on or in which a particulate material fill grows during the construction process by repeated coating with particulate material. The construction area is often limited by a floor, the “construction platform”, by walls and an open covering area, the construction level.

The process “printing” or “3D printing” within the meaning of the disclosure refers to the combination of the processes of material application, selective solidification or printing and adjusting the working height and takes place in an open or closed process or construction space.

A "receiving plane" within the meaning of the disclosure is the plane onto which building material is applied. According to the disclosure, the receiving plane is always freely accessible in one spatial direction by a linear movement.

"Spreading" or "applying" or "laying down" in the sense of the disclosure means any manner in which the particulate material is distributed. For example, a larger amount of powder can be placed at the start position of a coating run and distributed or spread into the layer volume by a blade or a rotating roller.

“Coater” or “recoater” or “material application agent” in the sense of the disclosure is the use unit by means of which a fluid is applied to the construction field. This can consist of a fluid storage container and a fluid application unit, whereby according to the present invention the fluid application unit comprises a fluid outlet and a "squeegee device". This squeegee device could be a coating blade. However, any other conceivable suitable squeegee device could also be used. Rotating rollers or a nozzle are also conceivable, for example. The material can be supplied freely via storage containers or extruder screws, pressure application or other material conveying devices.

The "print head" or "means for selective solidification" in the sense of the disclosure is usually made up of various components. These can include printing modules. The printing modules have a large number of nozzles from which the "binder" is ejected in droplet form onto the construction field in a controlled manner. The printing modules are aligned relative to the print head. The print head is aligned relative to the machine. This allows the position of a nozzle to be assigned to the machine coordinate system. The plane in which the nozzles are located is usually referred to as a nozzle plate. Another means for selective solidification can also be one or more lasers or other radiation sources or a heat lamp. Arrays of such radiation sources, such as laser diode arrays, can also be considered. In the sense of the disclosure, it is permissible for the introduction of selectivity to take place separately from the solidification reaction. For example, a selective treatment of the layer can be carried out via a print head or one or more lasers and the solidification can be started using other layer treatment means. In one embodiment, the particle material is printed with an IR absorber and then solidified with an infrared source. One or more printing modules can be mounted in a special arrangement in a "print head" in an assembly. The assembly as a whole serves to wet a surface - in this case a particle material on the construction field - with liquid (printing fluid) according to the DOD principle.

“Printing module” or “fluid dosing means” within the meaning of the disclosure refers to a unit for applying a liquid to a surface by means of the so-called ink-jet process according to the DOD principle.

"Layer treatment agents" in the sense of the disclosure are all agents that are suitable for achieving a certain effect in the layer. These can be the aforementioned units such as the print head or laser, but also heat sources in the form of IR radiators or other radiation sources such as UV radiators. Means for de- or ionization of the layer are also conceivable. What all layer treatment agents have in common is that their effective zone is distributed linearly across the layer and that they must be guided over the construction field like the other layer units such as the print head or coater in order to reach the entire layer.

“Drop-on-demand” or “DOD” or “DOD principle” in the sense of the disclosure refers to a method of applying a liquid to a surface, whereby the liquid is only active at the locations where the application is desired.

“Sintering emitter unit” or “sintering unit” or “sintering lamp” in the sense of the disclosure refers to the device with the aid of which particle material surfaces wetted with IR acceptor are specifically heated above the melting temperature using electromagnetic radiation. A “sintering unit” in the sense of this disclosure is the energy input means that can heat the process powder (particulate building material) above its sintering temperature. It can be stationary. In preferred embodiments, it is moved across the building field.

“Radiation converters” within the meaning of the disclosure refer to elements which, when exposed to electromagnetic radiation of a specific spectrum, change this spectrum in essential properties of the distribution of wavelength intensities.

The term "peak wavelength" in the sense of the disclosure refers to the wavelength of electromagnetic radiation in an approximate Planckian spectrum that has the highest intensity and obeys Wien's displacement law. In the case of emitters that do not follow the Planckian distribution, the peak wavelength can also refer to the wavelength that has the highest intensity.

For the purposes of the disclosure, “overflow” refers to the additional space required when an aggregate is moved on a linear axis completely across the construction field from one end to the other without creating shading on the construction field.

The "coupling" of cooling circuits or of a cooling circuit with a cooling part in the sense of the disclosure is when two functionally different parts have a coupling point or connection point at which a heat exchange can take place. For example, according to the disclosure, a closed air cooling circuit is coupled with a liquid-based cooling circuit and thus the air cooling circuit, which can absorb heat from, for example, a radiation converter, Heat is transferred to the liquid-based cooling circuit and then transported to the environment directly or possibly via another coolant, whereby the temperature at the radiation converter, for example, can be set or maintained at a target temperature when a control circuit is used.

A "closed" air cooling circuit in the sense of the disclosure means that the air in this circuit is essentially circulated in this circuit and no air is supplied from outside. In a particular embodiment, this circuit is sealed in such a way that no contaminants, such as particles of the building material, can penetrate into this circuit and thus no maintenance of this circuit is necessary.

An “air cooling circuit” within the meaning of the disclosure is an air circulation in a tube system of the sintering unit, wherein the air or gas is circulated, for example, by means of other means such as fans.

A “liquid-based cooling circuit” within the meaning of the disclosure is a closed circuit whose coolant is a liquid, such as water, oil or other known liquid coolants.

“Surface enlargement” in the sense of the disclosure is any means that increases a surface for cooling purposes, such as fins, ribs, etc. to increase the cooling capacity.

“Cooling part” within the meaning of the disclosure is a heat exchanger.

An “arrangement of printing modules” within the meaning of the disclosure is a plurality of printing heads, e.g. at least two or 3 to a plurality or 4 to 20 printing heads, which can be arranged in an articulated or unarticulated manner and connected to one another.

A "pressure fluctuation compensation module" in the sense of the disclosure is a means that is suitable for compensating pressure fluctuations and that is directly or indirectly connected to the printing fluid or to the line system of the print heads and/or the print heads and/or is coupled to them and can bring about pressure compensation. A pressure fluctuation compensation module can be designed as a 3-chamber module. Further details are described in the figures.

A “pressure sensor” within the meaning of the disclosure is a means that can register pressure differences or a pressure change and can pass these on to another unit, such as a control system or a controlled system.

A “system for applying a printing fluid” within the meaning of the disclosure is an arrangement of means suitable for applying printing fluids and may include print heads, line systems, sensors, actuators, etc.

A “pressure homogenization element” within the meaning of the disclosure serves to compensate for pressure differences and to connect pressure modules.

A "pressure fluid supply system" in the sense of the invention is a device that provides pressure fluid for an arrangement of printing modules. It can be given the task of keeping this supply at a temporally and/or spatially constant level in terms of volume flow and/or temperature during a printing process.

A “circulating pressure fluid supply” means a system for supplying an arrangement of pressure modules with pressure fluid, whereby the fluid is conveyed in a circuit.

A “printing fluid” in the sense of the invention is a liquid which serves to wet a surface to be printed, preferably by means of an arrangement of printing modules.

The invention and its disclosure are described below.

In one aspect, the invention relates to a system for applying a printing fluid comprising a print head unit (101) comprising an arrangement of printing modules (102) and a pressure fluctuation compensation module (106), characterized in that the print head and the pressure fluctuation compensation module (106) are coupled.

In a preferred system, the pressure fluctuation compensation module (106) is a 3-chamber module.

The system according to the disclosure may comprise pressure sensors and control loops at suitable locations in the system, wherein the system preferably comprises at least two pressure sensors.

Furthermore, the system according to the disclosure can comprise pumps, control circuits, regulating circuits and pressure sensors in a coupled manner, wherein in a preferred embodiment in the system the two pressure sensors on the pressure fluctuation compensation module (106) are connected to two controlled, preferably speed-controlled pumps in the pressure fluid supply system (301).

In a preferred embodiment, the system according to the disclosure may comprise a temperature control unit which comprises a cooling and/or a heating element and which comprises at least two temperature sensors, preferably three temperature sensors.

In a preferred system, the two pressure sensors on the pressure fluctuation compensation module (106) are connected to two speed-controlled pumps in the pressure fluid supply system (301).

In a further preferred system, the arrangement of pressure modules (102) are connected to a circulating pressure fluid supply by means of pressure fluid connection lines (105) via pressure homogenization elements (103) and (104).

In a further preferred system, the pressure fluid is evenly distributed across all pressure modules (102), preferably the pressure differences occurring between the pressure modules (102) will not exceed a value of ± 2 mBar, preferably 1 mBar.

A preferred system is characterized in that the pressure fluid connection lines (105) to the individual pressure fluid metering means (102) are designed to be substantially identical and/or the connection elements on the pressure homogenization elements (103) and (104) are designed to be substantially identical, preferably in length and diameter.

Another preferred system is designed such that the ratio of the total flow resistance of the parallel-connected pressure modules to the flow resistance of the pressure homogenization element is greater than 50:1.

In a preferred system, the pressure module(s) are operated with a pressure difference of the volume flow of 50 - 150m bar.

Another preferred system is designed such that the pressure homogenization elements (103) and (104) are connected via a shut-off valve (114).

In another preferred system, a pressure fluctuation compensation module (106) is attached to the pressure homogenizing elements (103) and (104).

In a further preferred system according to the disclosure, the pressure in the system and the temperature of the pressure fluid flowing through it are measured by means of measuring instruments (107) and (108).

Another preferred system is characterized in that the print head unit (101) has a print head unit coolant (115), preferably the volume flow of the coolant is monitored by means of measuring instruments such as temperature and volume flow sensors (110) and regulated by means of a control valve (111).

In a further aspect, the disclosure relates to a pressure fluctuation compensation module (106) through which a pressure fluid is guided on the way to the print head unit (101), characterized by substantially mutually coupled chambers (203) and (204), which are separated from one another by movable membranes (206) and (207), preferably comprising a third chamber (205).

A preferred pressure fluctuation compensation module (106) according to the disclosure is characterized in that the third chamber (205) is filled with a medium (208) other than the pressure fluid, preferably this medium is a gas such as air, preferably the third chamber (205) is subjected to overpressure or underpressure.

In a preferred pressure fluctuation compensation module (106) according to the disclosure, sensors (107) and (108) are attached to the pressure fluctuation compensation module in the compensation chambers containing pressure fluid for measuring pressure and temperature.

Another preferred pressure fluctuation compensation module (106) according to the disclosure is characterized in that chambers (203) and (204) each have a gas-filled intermediate chamber (205) which is in communication with a third chamber (210) which has a compensation membrane (211) and the compensation membrane (211) is not in direct contact with the pressure fluid.

In a further aspect, the disclosure relates to a printing device for an additive manufacturing process comprising a system as described above and/or a pressure fluctuation compensation module as described above.

In a further aspect, the disclosure relates to a method for producing 3D molded parts in which all known steps of an additive printing process are carried out and in which a system as described above and/or a pressure fluctuation compensation module as described above is used.

It was advantageously possible to achieve a uniform release of pressure fluid by using a pressure fluctuation compensation module, even at high travel speeds. This ensures that a printing device can be operated at high process speeds and at the same time the pressure fluid is available at each printing module in the desired manner in a predetermined volume and can essentially be released in the desired amount in order to guarantee the quality of the molded part produced.

• In 1 ist ein bevorzugtes System mit Druckkopfeinheit nach der Offenbarung dargestellt. 1 zeigt eine Druckkopfeinheit 101, die im Wesentlichen dadurch gekennzeichnet ist, dass eine Anordnung von Druckmodulen 102 mittels Druckfluidanschlussleitungen 105 über Druckhomogenisierungselemente 103 und 104 mit einer Umlaufdruckfluidversorgung verbunden sind. Die Druckhomogenisierungselemente haben die Aufgabe, entlang einer oder mehrerer dimensionalen Ausdehnungen befindlicher Druckmodule 102, diese mit einem Druckfluid zu versorgen, wobei durch ihre Anordnung und Ausführung dafür gesorgt wird, dass das Druckfluid über alle Druckmodule hinweg gleichmäßig verteilt wird, indem die Strömungswiderstände der einzelnen Druckmodule mit ihren jeweiligen Anschlusselementen möglichst gleich und groß gegenüber dem Strömungswiderstand der Druckhomogenisierungselemente gehalten werden.

Further description of the revelation and further examples:

• In 1 a preferred system with print head unit according to the disclosure is shown. 1 shows a print head unit 101, which is essentially characterized in that an arrangement of pressure modules 102 are connected to a circulating pressure fluid supply by means of pressure fluid connection lines 105 via pressure homogenization elements 103 and 104. The pressure homogenization elements have the task of supplying pressure modules 102 located along one or more dimensional extensions with a pressure fluid, whereby their arrangement and design ensure that the pressure fluid is evenly distributed across all pressure modules by keeping the flow resistances of the individual pressure modules with their respective connection elements as equal and large as possible compared to the flow resistance of the pressure homogenization elements.

Differences in the volume flow must under no circumstances lead to pressure differences between the pressure modules that exceed a value of ± 1 mBar, as this would lead to variations in the masses of the drops emitted and thus to fluctuations in the absorption of the surface to be exposed. This would result in a different amount of energy being introduced onto the surface to be sintered, which would result in variations within the molded body to be created.

In order to achieve this, the pressure homogenization element is designed such that the cross-section through which the fluid flows is in any case large in relation to the pressure fluid connection line 105 to the pressure modules.

The lengths of the various pressure fluid connection lines 105 to the individual pressure fluid dosing means 102 should continue to be as identical as possible, as should the connection elements to the pressure homogenization elements 103 and 104.

These relationships are evident from the following equations: According to the Hagen-Poiseuille law, pressure losses arise due to friction losses between the flowing liquid and the inner wall of the pipe (Wolfgang Kümmel, Technical Fluid Mechanics, 2007, p. 98) $$p_1-p_2=\Delta p_v=\frac{\mathrm{8th}\cdot \eta \cdot l\cdot \dot{V}}{\pi \cdot r^4}$$

With the volume flow through the pipe V, the inner radius of the pipe r, length of the pipe I, dynamic viscosity η and the pressures p.

The pipe resistance R _pipe is the pressure difference Δp _v divided by the volume flow V: $$R_{ROHr}=\frac{\Delta p_v}{\dot{V}}=\frac{\mathrm{8th}\cdot \eta \cdot l}{\pi \cdot r^4}in\left[\frac{\frac{kG}{s}}{m^4}\right]$$

The pipe resistance and the resulting pressure differences are therefore dependent on the pipe's inner diameter to the fourth power. Thus, by choosing the right pipe diameter, an advantageous pressure distribution in the device can be achieved.

The resistance using the example of a commercially available pressure module when using a pressure fluid with a typical viscosity of approx. 12 mPas is approximately: $$R_{DruckkOpe}=\frac{\Delta p_{DruckkOpe}}{\dot{V}}=\frac{10kPa}{150\frac{ml}{min}}=4.0\cdot {10}^9\frac{\frac{kG}{s}}{m^4}$$

Using the electro-hydraulic analogy ( Horst-W. Grollius, Fundamentals of Hydraulics, 2012, p. 39-40 ), a simulation of the fluid system can be generated using electrical equivalent circuits. The voltage corresponds to the pressure difference Δp and the current to the volume flow Q=V. Using this analogy, a relationship between electrical and hydraulic resistance R in a pipe with radius r and length I can be defined.

The ratio of the total flow resistance of the parallel-connected pressure modules to the flow resistance of the pressure homogenization element must be better than (greater than) 50:1.

State-of-the-art pressure modules are operated with a volume flow that corresponds to a pressure difference of 50 to 150 mBar.

In an exemplary design with 5 pressure modules on a pipe with a length of approx. 1 meter, the simulation shows that this results in a minimum pipe diameter of > 10 mm if the pressure difference across all pressure modules is to be < 1 mBar.

The pressure homogenization elements can be connected via a shut-off valve 114. This can make it easier to start up the print head unit and change individual pressure modules by reducing the differential pressure on the pressure modules when the valve is opened. This makes it easier to replace the pressure fluid in the pressure fluid lines and the pressure homogenization elements with another fluid, which can also be a gas or ambient air.

The print head unit is further characterized in that a pressure fluctuation compensation module 106 is attached to the pressure homogenization elements, through which the pressure fluid is guided in both the forward flow 112 and the return flow 113. Furthermore, the applied pressure and the temperature of the pressure fluid flowing through are measured by means of measuring instruments 107 and 108 attached to the main pressure fluid supply of the print head unit.

The print head unit can have a print head unit coolant 115, which can provide thermal shielding of the print head unit from the environment. This also ensures a uniform temperature distribution across the dimensional extent of the print head unit. The coolant can be a network or tubes through which the cooling fluid flows. The volume flow of the coolant can then be monitored using measuring instruments such as temperature and volume flow sensors 110 and regulated using a control valve 111.

In 2a an example of a pressure fluctuation compensation module is shown. The pressure fluctuation compensation module 106 through which the pressure fluid is guided on the way to the print head unit 101 essentially consists of chambers 203 and 204 coupled to one another, which are separated from one another by movable membranes 206 and 207. If necessary, a third chamber 205, which is filled with a different medium, can be inserted between the two chambers filled with pressure fluid. This different medium 208 can also be a gas such as air. The intermediate chamber can be subjected to an overpressure or underpressure, which can be controlled by means of the inlet valve 209. In this way, the restoring force acting on the membranes can be controlled in a targeted manner. The damping constant of the pressure fluctuation compensation module can thus be adjusted to the requirements and can be adapted depending on the viscosity and compressibility of the pressure fluid, as well as the number of pressure modules and the arrangement of the units in the device.

The module's job is to minimize pressure fluctuations in the pressure fluid supply system, which can occur due to pump pulsations, supply line vibrations or pressure fluid dosing by the pressure modules. Above all, the coupling enables them to compensate for pressure fluctuations due to accelerations caused by translational movements of the printing system. To ensure this to the best extent possible, the pressure compensation module is located next to the print head, which represents a new aspect. If acceleration occurs in the direction of the line, the inertia of the pressure fluid in the lines and the print head unit leads to pressure fluctuations within the pressure fluid supply and thus in the pressure modules connected to it. This would result in uncontrolled leakage of pressure fluid from the pressure modules. However, since these are intended to release pressure fluid in a controlled manner, this would result in a loss of quality.

Only minimizing the forces that occur, e.g. by means of a very flat acceleration curve, could prevent this unhindered leakage. However, this would involve an undesirable, strong reduction in speed in the translational movement of the printing system and a not inconsiderable increase in the necessary travel distances. Reducing the number of printing modules, which reduces the printing performance of the device, and thus reducing the volume of printing fluid in the device would also help to minimize the fluctuations.

Preferably, sensors 107 and 108 are mounted on the pressure fluctuation compensation module in the compensation chambers containing the pressure fluid for measuring pressure and temperature, with which the pressure fluid supply can be regulated.

In 2 B An alternative, advantageous embodiment of a pressure fluctuation compensation module 106 is described. In this case, the gas-filled intermediate chamber 205 2a modified in that it is divided into the two chambers 203 and 204, which are partially filled with gas for this purpose. The gas content can be varied using the valves 209. The two chambers are fluidically connected by means of a third chamber 210. In the third chamber there is a compensating membrane 211. The membranes 206 and 207 are thus replaced by a membrane 211, which does not separate the liquids from the gas, but rather the two gas volumes above the liquids. Only one membrane is therefore required and the device can be manufactured more cost-effectively and is less prone to errors.

Furthermore, the new compensation membrane 211 is no longer in direct contact with the pressure fluid. This means that it is no longer necessary to use membrane material that is chemically resistant to the pressure fluid, which significantly increases the choice of materials. This enables advantageous adaptation to the vibration behavior and a more cost-effective design.

Another advantage is the possibility of making access to the membrane 211 easier due to the external design of chamber 210. Due to the lack of fluid contact, it can be changed without protective equipment and in a much shorter time. Since the membrane is generally a wearing part, this also significantly reduces maintenance costs.

3 shows an example of a fluid supply for the print head unit 101 with the included print modules 102. The print head unit is mounted on a linear axis so that it can move in one direction. The supply lines can be guided by means of a supply chain 303 as shown. The change in position does not have to be limited to one dimension.

The pressure fluid supply is provided by the device 301. It consists of two speed-controlled pumps for each supply direction, a fluid heater and a filter. A reservoir with a level indicator contains the supply of pressure fluid, from which a quantity can be withdrawn by means of the feed pump. The measured values of the sensors 107 and 108 in the inlet and return chambers of the pressure fluctuation compensation module 106 are used to generate constant pressure states at the pressure modules 102 by controlling the speed of the pumps via a control loop.

The temperature of the printing fluid is also regulated to a constant value by means of a fluid heater based on the measured values of the temperature sensors. The temperature control device 302, which is used to control the temperature of the print head unit, is designed here by way of example using a feed pump and a recooler.

High-frequency control of the units ensures that the pressure of the pressure fluid at the pressure modules remains constant over time during operation, even when they are subjected to accelerated movement. To enable high-frequency control, the measuring instruments for the pressure in the pressure fluid supply and return lines 107 and 108 should have a high sampling rate. Measurement frequencies > 50 values per second should be used, especially for recording the pressure measurements. In addition, the measurement accuracy should be selected to be high enough. A measurement tolerance of < ± 1 mBar appears to be sensible in practice.

Experiments have shown that conventional ink circulation systems cannot be operated with accelerations of > 0.5 m/s ² of the ink dosing system mounted on a linear axis, even with greater effort, due in part to a control system that is too slow. Limiting the acceleration to smaller values means that acceleration ramps must be provided for the axis movements. In addition, a longer settling time is required for the pressure control during the movement until reliable dosing of the fluid can begin.

In conventional systems based on the state of the art, it is therefore necessary to reduce the stable working area of the device or to use longer axis systems, which increases the dimensions of the device against economic aspects, since the production capacity of the device per area is significantly smaller. The printing process is also slowed down, since the linear axes mean a longer path back per layer produced.

In thermal processes, energy consumption is also higher because a larger process volume has to be heated for a longer period of time in relation to the production volume. This is clearly reflected in the costs per unit of volume produced.

When measuring the temperature, it should also be ensured that the temperature sensors are mainly in thermal contact with the pressure fluid and not with the device itself. To do this, it is advantageous to insulate them from the carrier using a material that is a poor thermal conductor. A more precise measurement of the temperature also enables improved control of the heating or cooling systems.

Preferably, the temperature sensors are installed in the pressure fluctuation compensation module or in the print head unit itself, which means a shortening of the control path and thus contributes to a higher accuracy of the temperature of the pressure fluid during dosing. The temperature sensors can also be integrated into the pressure sensors. In addition, the temperature of the nozzle plate of a print module can also be used as the control temperature, which is possible, for example, with the Seiko RCA-1536M in combination with the AEWA APMB3 dosing control.

$${\text{P}}_{\text{differential}}=\left|{\text{P}}_{\text{supply}}\right|+\left|{\text{P}}_{\text{return}}\right|$$

In one aspect, a control system can also be provided. In one embodiment, the two pressure sensors on the pressure fluctuation compensation module are connected to two speed-controlled pumps in the pressure fluid supply system 301. The speed of both pumps is controlled via two PID controllers, with the two sensor values P _supply , the pressure on the supply line, and P _return , the pressure on the return line, serving as the input signal: $${\text{P}}_{\text{meniscus}}=\left|{\text{P}}_{\text{supply}}-{\text{P}}_{\text{return}}\right|$$

$${\text{P}}_{\text{differential}}=\left|{\text{P}}_{\text{supply}}\right|+\left|{\text{P}}_{\text{return}}\right|$$

P _meniscus refers to the negative pressure applied to the fluid dosing medium and P _differential refers to the differential pressure within the fluid supply system, which is followed by the circulation speed of the pressure fluid. These two parameters also represent the controlled variable.

The speed control of the feed pump is therefore based on the input value P _differential , whereas the control of the return pump uses P _meniscus as the input value. Both controls work in parallel.

The situation is similar with the temperature control devices: Most pressure fluids have an optimal operating point, which is usually above the ambient temperature, e.g. between 20-50°C, preferably 35°C. At this temperature, the viscosity of the pressure fluid then corresponds to the manufacturer's specifications for the pressure fluid dosing medium. The heating element in 301 is used for this purpose. The sensor value of the temperature sensor T _supply in the inlet of the pressure fluctuation compensation module acts as the input value for the control.

In the return line of the fluid system there is a second temperature sensor T _return which can be used to determine the temperature of the printing fluid flowing back from the print head unit.

A third temperature sensor 110 T _cooling is located in the coolant circuit and is used to regulate the cooling capacity of the print head unit cooling system to a preset value, which preferably corresponds to that of the printing fluid temperature control.

The cooling circuit is thermally coupled to the pressure fluid circuit via the contact between the print head unit coolant and the pressure fluid dosing medium, which must be taken into account when controlling both the heating element in 301 and the cooling element 302. The coolant is preferably switched off as long as the heating element preheats the pressure fluid. A further sensor Q _cooling , preferably integrated in 110 in the coolant circuit, can be used to limit the volume flow of the coolant by means of a further control circuit if T _return < T _supply . As long as the return temperature of the pressure fluid is lower than the inlet temperature, the cooling capacity can be reduced. This can prevent heating and cooling elements from working against each other or, in the worst case, oscillating.

In 4 describes a further preferred aspect of the disclosure in which a cleaning fluid may be used to clean various portions or components of the device; this cleaning may be carried out at least partially during operation.

In 4 are designed with reference numbers 402 and 403 as a three-way ball valve, manually or externally operated (rotary actuator). Three/two-way valves or coupled two/two-way valves can be used, which can be switched electromagnetically, pneumatically or externally operated. If these are manually switched, they are operated via locking couplers. A circuit is installed between the pressure fluctuation compensation device and the pressure compensation device, whereby this is possible in the forward and return flow.

• Beide Ventile 402, 403 werden annähernd zeitgleich geschaltet und koppeln so das Umlauffluidsystem ab. Dadurch wird ein Spülsystem 401 mit den Druckmodulen verbunden. Es wird ein positiver Druck mittels Pumpe 406 an Zulauf (50 - 500 mBar = Maximum Strömungswiderstand im Druckmodul) angelegt. Daraufhin kann ein Reinigungsfluid aus den Druckdüsen der Druckfluidfluiddosiermittel 102 strömen und reinigt diese. Der Hauptanteil an Reinigungsfluid fließt zurück über einen Rücklauf in das Reinigungsfluidabfallbehältnis 405. Dann werden beide Ventile 402, 403 wieder zurück geschaltet auf das Umlauffluidsystem. Die Druckfluidfluiddosiermittel 102 und die Druckhomogenisierungsmittel 103 und 104 sind nun gereinigt.

A first functionality with a simplified process can be implemented as follows:

• Both valves 402, 403 are switched almost simultaneously and thus decouple the circulating fluid system. This connects a flushing system 401 to the pressure modules. A positive pressure is applied to the inlet using pump 406 (50 - 500 mBar = maximum flow resistance in the pressure module). A cleaning fluid can then flow out of the pressure nozzles of the pressure fluid dosing means 102 and cleans them. The majority of cleaning fluid flows back via a return line into the cleaning fluid waste container 405. Then both valves 402, 403 are switched back to the circulating fluid system. The pressure fluid dosing means 102 and the pressure homogenization means 103 and 104 are now cleaned.

• Die Regelung der Pumpendrehzahlen von Druckfluidförder- und -rücklaufpumpen wird ausgesetzt, Zulaufventil 402 auf Reinigungsfluid gestellt und Rücklaufventil 403 auf Tintenumlaufsysstem belassen. Nun wird mittels der Reinigungsfluidförderpumpe 406 das Reinigungsfluid durch die Druckhomogenisiermittel und Druckfluiddosiermittel gepumpt, wobei aufgrund der ausgeschalteten Rückförderpumpe im System ein Überdruck entsteht, der 150 mBar in handelsüblichen Druckfluiddosiermitteln nicht übersteigen darf. Somit wird Reinigungsfluid mitsamt Verunreinigungen durch die Düsen der Druckfluiddosiermittel gedrückt und diese somit von Schmutz befreit. Anschließend wird Rücklaufventil 403 auf den Reinigungsfluidkreis geschaltet und überschüssiges Reinigungsfluid in das dafür vorgesehene Reinigungsfluidabfallbehältnis 405 befördert. Zum Schluss kann das Druckfluidfördersystem samt Regelung wieder aktiv geschaltet werden. Die Düsen der Druckfluiddosiermittel 102 sind nun gereinigt.

In a second mode of operation, the nozzles of the pressure fluid dosing means 102 can be cleaned as follows:

• The regulation of the pump speeds of the pressure fluid feed and return pumps is suspended, the inlet valve 402 is set to cleaning fluid and the return valve 403 is left on the ink circulation system. The cleaning fluid feed pump 406 is now used to pump the cleaning fluid through the pressure homogenization means and pressure fluid dosing means, whereby an overpressure is created in the system due to the return pump being switched off, which must not exceed 150 mbar in commercially available pressure fluid dosing means. In this way, cleaning fluid, including impurities, is pressed through the nozzles of the pressure fluid dosing means, thus freeing them of dirt. The return valve 403 is then switched to the cleaning fluid circuit and excess cleaning fluid is conveyed to the cleaning fluid waste container 405 provided for this purpose. Finally, the pressure fluid feed system and control can be activated again. The nozzles of the pressure fluid dosing means 102 are now cleaned.

• Während des geregelten Betriebs wird Zulaufventil 402 vom Druckfluidzulauf auf den Reinigungsfluidzulauf geschaltet. Das Ventil im Rücklauf 403 verbleibt zunächst in der Ausgangsstellung und mit dem Druckfluidkreislauf verbunden. Reinigungsfluidpumpe 406 wird nun aktiv. Sie fängt an, das Reinigungsfluid durch das Druckhomogenisierelement 103 zu pumpen, durch welches das Reinigungsfluid auch die Druckfluiddosiermittel 102 erreicht und diese durchströmt und reinigt. Mittels der nach wie vor aktiven Regelung an der Fluidrückförderpumpe im Rücklauf wird das Reinigungsfluid durch das Druckhomogenisierelement 104 aus den Druckfluiddosiermitteln 102 in den Rücklauf des Fluidsystems befördert. Hier wird nun zeitversetzt auch Rücklaufventil 403 aktiv, wodurch das Reinigungsfluid aus dem System entweichen kann und in das Reinigungsfluidabfallbehältnis 405 gelangt. Gleichzeitig schaltet Ventil 402 wieder zurück auf den Druckfluidkreislauf. Somit wird den Druckhomogenisierelementen 103 und 104, sowie dem Druckfluiddosiermittel 102 wieder Druckfluid zugeführt. Sobald nach einiger Zeit das Druckfluid alle angeschlossenen Elemente vollständig durchströmt hat, wird auch Rücklaufventil 403 wieder auf das Druckfluidsystem zurückgeschaltet, sodass sich das System wieder im Ausgangszustand befindet. Während der gesamten Zeit des Ablaufs bleiben alle Regelungen aktiv, sodass sich im System nur minimale Druckschwankungen ergeben und somit sichergestellt ist, dass kein Fluid aus den Druckfluiddosiermitteln 102 ungewollt austritt.

In a third mode of operation, cleaning of the pressure homogenizing elements 103, 104 and of the pressure fluid dosing means 102 can be carried out as follows:

• During controlled operation, inlet valve 402 is switched from the pressure fluid inlet to the cleaning fluid inlet. The valve in the return line 403 initially remains in the starting position and is connected to the pressure fluid circuit. Cleaning fluid pump 406 is now activated. It begins to pump the cleaning fluid through the pressure homogenization element 103, through which the cleaning fluid also reaches the pressure fluid dosing means 102 and flows through and cleans them. By means of the still active control on the fluid return pump in the return line, the cleaning fluid is conveyed through the pressure homogenization element 104 from the pressure fluid dosing means 102 into the return line of the fluid system. Here, return valve 403 is also activated with a time delay, allowing the cleaning fluid to escape from the system and into the cleaning fluid waste container 405. At the same time, valve 402 switches back to the pressure fluid circuit. Pressure fluid is thus again supplied to the pressure homogenization elements 103 and 104, as well as to the pressure fluid metering device 102. As soon as the pressure fluid has completely flowed through all connected elements after some time, the return valve 403 is also switched back to the pressure fluid system so that the system is back in its original state. During the entire process, all controls remain active so that only minimal pressure fluctuations occur in the system and it is thus ensured that no fluid escapes from the pressure fluid metering devices 102 unintentionally.

List of reference symbols

101

Print head unit tempered by cooling medium

102

Pressure module/pressure fluid dosing agent

103

Pressure homogenizing element inlet

104

Pressure homogenizing element return

105

Pressure module fluid supply

106

Pressure fluctuation compensation module

107

Measuring instruments temperature and pressure pressure fluid supply

108

Measuring instruments temperature and pressure pressure fluid return

109

Coolant supply

110

Measuring instruments temperature and volume flow coolant return

111

Volume flow control coolant supply

112

Pressure fluid supply

113

Pressure fluid return

114

Connection with shut-off valve

115

Printhead unit coolant

201

Pressure fluid line to the print head unit

202

Pressure fluid line from the print head unit

203

Pressure fluid chamber inlet

204

Pressure fluid chamber return

205

Chamber compensating fluid

206

First membrane

207

Second membrane

208

Intermediate chamber

209

Inlet valve to the intermediate chamber

210

Gas fluid chamber

211

Compensating membrane

301

Pressure fluid supply system with heating device [COMMENT: Heating device still in the description]

302

Printhead unit cooling system

303

Supply chain

401

Supply and return lines for flushing fluid

402

Valve in the supply line for switching between flushing fluid and pressure fluid

403

Valve in the return line for switching between flushing fluid and pressure fluid

404

Cleaning fluid container

405

Cleaning fluid waste container

406

Cleaning fluid pump

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed 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 accepts no liability for any errors or omissions.

Cited patent literature

• EP 0431924 B1 [0002]

Cited non-patent literature

• Horst-W. Grollius, Fundamentals of Hydraulics, 2012, pp. 39-40 [0099]

Claims (10)

System for applying a printing fluid comprising a print head unit (101) comprising an arrangement of printing modules (102) and a pressure fluctuation compensation module (106), characterized in that the print head and the pressure fluctuation compensation module (106) are coupled. System according to Claim 1 , wherein the pressure fluctuation compensation module (106) is a 3-chamber module, preferably wherein the system has at least two pressure sensors, or/and wherein the two pressure sensors on the pressure fluctuation compensation module (106) are connected to two speed-controlled pumps in the pressure fluid supply system (301), or/and wherein the system has a temperature control unit which has a cooling and/or a heating element and which has at least two temperature sensors, preferably three temperature sensors, or/and wherein the two pressure sensors on the pressure fluctuation compensation module (106) are connected to two speed-controlled pumps in the pressure fluid supply system (301), or/and wherein the arrangement of pressure modules (102) is connected to a circulating pressure fluid supply by means of pressure fluid connection lines (105) via pressure homogenization elements (103) and (104), preferably wherein the pressure fluid is evenly distributed across all pressure modules (102), preferably the Pressure differences that occur between the pressure modules (102) do not exceed a value of ± 2 mBar, preferably 1 mBar, and/or wherein the pressure fluid connection lines (105) to the individual pressure fluid metering means (102) are designed to be substantially identical and/or the connection elements on the pressure homogenization elements (103) and (104) are designed to be substantially identical, preferably in length and diameter. System according to one of the preceding claims, wherein the ratio of the total flow resistance of the parallel-connected pressure modules to the flow resistance of the pressure homogenization element is greater than 50:1. System according to one of the Claims 1 - 3 , wherein the pressure module or modules are operated with a pressure difference of the volume flow of 50 - 150m bar, preferably wherein the pressure homogenization elements (103) and (104) have a connection via a shut-off valve (114), and/or wherein a pressure fluctuation compensation module (106) is attached to the pressure homogenization elements (103) and (104). System according to one of the preceding claims, wherein the pressure in the system and the temperature of the pressure fluid flowing through are measured by means of measuring instruments (107) and (108). System according to one of the preceding claims, wherein the print head unit (101) has a print head unit coolant (115), preferably the volume flow of the coolant is monitored by means of measuring instruments such as temperature and volume flow sensors (110) and controlled by means of a control valve (111). Pressure fluctuation compensation module (106) through which a pressure fluid is passed on the way to the print head unit (101), characterized by substantially mutually coupled chambers (203) and (204) which are separated from one another by movable membranes (206) and (207), preferably comprising a third chamber (205). Pressure fluctuation compensation module (106) according to Claim 7 , wherein the third chamber (205) is filled with a medium (208) other than the pressure fluid, preferably this medium is a gas such as air, preferably the third chamber (205) is subjected to overpressure or underpressure, preferably wherein sensors (107) and (108) are attached to the pressure fluctuation compensation module in the compensation chambers containing the pressure fluid for measuring pressure and temperature, and/or wherein chambers (203) and (204) each have a gas-filled intermediate chamber (205) which are connected to a third chamber (210) which has a compensation membrane (211) and the compensation membrane (211) is not in direct contact with the pressure fluid. Printing device for an additive manufacturing process comprising a system according to one of the Claims 1 - 6 and/or a pressure fluctuation compensation module according to one of the Claims 7 - 8th having. Method for producing 3D molded parts, in which all known steps of an additive printing process are carried out and in which a system according to one of the Claims 1 - 6 and/or a pressure fluctuation compensation module according to one of the Claims 7 - 8th is used.