Printhead for a 3D printer, and method of operating the printhead

Abstract

The present invention relates to a print head (100) for a 3D printer, comprising an actuator arrangement (110) for controlling a piston (3) arranged in a housing (1) of the print head (100), a supply device (2) for a printable material (10), a flange (5) having a cooling arrangement (50) arranged in the housing (1) and in the supply device (2), a nozzle head (6) having heating elements (61, 63) for transforming the material (10) from a solid phase (10) via a plastic phase (11) to a liquid phase (12), and a nozzle (8) for ejecting the liquid phase (12) of the material (10) from the nozzle head (6). According to the invention, a kidney-shaped part (7) is arranged in the lower partial region (42) of the separate piston bush (4), the kidney-shaped part (7) having a centrally extending bore (70) for receiving the piston needle (32) of the piston (3) and having concentrically arranged openings (71) which form a fluid connection between a hollow chamber (40) arranged in the piston bush (4) and a melt chamber (81) arranged in the lower part (62) of the nozzle head (6). Furthermore, the invention relates to a method (200) for operating the nozzle head (100) according to the invention.

Description

Technical Field

[0001] The present invention relates to a print head for a 3D printer and to a method of operating the print head.

Background Art

[0002] A 3D printer for a material that is variable with respect to viscosity includes a solid phase of the material as a starting material, generates a liquid phase therefrom, and selectively applies this liquid phase to locations belonging to the object to be created. Such a 3D printer includes a print head in which the starting material is pre-treated so that printing preparation is completed. Further, means for causing relative movement between the print head and the working surface on which the object is to be generated is provided. At this time, only the working surface can move, or both the print head and the working surface can move.

[0003] The print head has a first operating state in which the liquid material exits therefrom and a second operating state in which the liquid material does not exit therefrom. The second operating state is taken, for example, when it is to be moved to another position of the working surface and the material should not be applied on the path thereto. Switching can be performed between these two operating states of the print head, for example, by turning on or off the feeding of the solid starting material.

[0004] The most widespread is the "Fused Deposition Modeling" (FDM) in which a filament made of a starting material is melted in an electrically heated extrusion nozzle and applied layer by layer to a platform. In the form of such a type of filament, the starting material becomes very expensive.

[0005] In Patent Document 1, it is proposed to supply the starting material in a granular form, convey it to a heated zone by a worm conveyor, and the starting material exits therefrom in a plasticized form. On the one hand, granules are clearly more convenient, and on the other hand, a mixture of different thermoplastic materials can be easily produced in such a manner.

[0006] Furthermore, a print head is known from Patent Document 2, in which the granules are plasticized via a piston and a heated section. When the piston presses on the granules, they are compressed and conveyed to a plasticizing zone in the lower region of the print head. At this time, a strong load is applied to the piston and the cylinder wall of the print head, generating a force that may lead to an increase in wear on the cylinder wall of the print head housing. Furthermore, a complex melting geometry with a heat conduction structure is disclosed, which injects the heat output of the heating member into the plasticized material to turn it into the liquid phase of the material.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem of the present invention is to provide a compact print head for a 3D printer and a method for operating the print head that enable a high dynamics and a stable printing process.

Means for Solving the Problems

[0009] Within the framework of the present invention, a print head for a 3D printer has been developed. Furthermore, a method for operating the print head has been developed.

[0010] The print head for a 3D printer includes an actuator device for controlling a piston, which is arranged in a housing of the print head, a supply device for a printable material, a flange having a cooling device, which is arranged on the housing and the supply device, a nozzle head having a heating member for converting a material from a solid phase through a plastic phase to a liquid phase, and a nozzle for discharging the liquid phase of the material from the nozzle head. According to the invention, a kidney-shaped part is arranged in a partial region below a separate piston bush. The kidney-shaped part has a bore extending centrally for receiving the piston needle of the piston. The kidney-shaped part has concentrically arranged openings, which form a fluid connection between a hollow chamber arranged in the piston bush and a melt chamber arranged in the lower part of the nozzle head.

[0011] The actuator device for controlling the piston may be, for example, an electric motor having a mechanical transmission mechanism or a hydraulic drive having a hydraulic pressure source. The electric motor as the actuator device has a lower weight compared to a hydraulic drive, which has the advantage of acting due to the high dynamics of the entire printer and the printing process. This is because only a low mass needs to be accelerated. The hydraulic drive has the advantage of achieving a high force when the piston is controlled.

[0012] The supply device for the printable material may in particular be intended as a supply for a material or starting material present as granules. The starting material may in particular be a thermoplastic material. By using granules as the starting material, it has been found that specific advantages are realized, particularly with regard to the cost of the starting material of the printer, compared to a print head using a filament made of a thermoplastic material.

[0013] When compared to a print head in which the particles are conveyed by a worm conveyor, the print head according to the invention can be configured to be even more compact. This in turn results in the print head being even simpler and easier to move. This is particularly advantageous when it is desired to move the print head very quickly, in particular at a speed of 100 mm / s or more.

[0014] The flange includes a cooling device, thereby enabling optimized thermal management in the region of the supply device, with the result that adhesion of the material or particles to the piston is avoided. Furthermore, the nozzle head has a heating member for converting the material, in particular the solid phase which is the particles, into the liquid phase. The heating device in the nozzle head has the advantage of acting for the precise injection of the thermal output into the material to be melted. Subsequently, the liquid phase or melt can be discharged through the nozzle of the nozzle head by piston movement.

[0015] A separate piston bush for guiding the piston enables the piston to be directly guided within the piston bush rather than within the housing or cylinder of the print head. Thereby, the resulting wear occurs directly inside the piston bush rather than directly on the inner wall of the housing or cylinder. The piston bush as a separate component offers the advantage of being replaceable when needed. Furthermore, the possibility is given to apply a piston and a piston bush adapted to each other under various different diameters, for example without other design changes such as in the flange or the nozzle head.

[0016] Furthermore, the piston bush has an upper partial region that penetrates into the flange and a lower partial region that penetrates into the nozzle head. Thereby, the upper partial region is arranged in the action region of the cooling zone of the flange cooling device, and the lower partial region is arranged in the action region of the heating zone of the nozzle head, thereby having the advantage that efficient energy discharge from the material inside the cooling zone or efficient energy supply to the material inside the heating zone is realized.

[0017] In the upper partial region of the piston bush, an opening or an opening cross-section that enables the supply of material from the supply device to the piston bush is arranged. In the lower region of the opening, a gate that is formed at an obtuse angle with respect to the inner surface of the piston bush is arranged. The region of this gate is hardened or, alternatively, produced as a separately hardened insert part. When the opening is closed by the piston, the material or granules are sheared by the piston at the gate, whereby a strong mechanical load acts on the corresponding part of the piston bush. There is an advantage that a longer service life and a quicker replacement of defective components are realized by means of a separate piston bush and by means of the hardened region of the gate.

[0018] Furthermore, the piston bush has a stopper between the upper and lower partial regions, and the flange and the nozzle head are separated from each other by this stopper. In this way, the piston bush and especially the stopper have the advantage of separating the cooled flange from the heated nozzle head, thereby preventing them from coming into contact with each other.

[0019] The piston includes a first piston portion for connecting to an actuator device and a piston head for connecting to the first piston portion and for accommodating a piston needle. The first piston portion is preferably configured as an aluminum hollow piston, whereby a coolant can be guided through the first piston portion, thereby achieving the advantage of piston cooling. The piston head has a lower surface on the side facing the nozzle, and the piston needle projects from the center of this lower surface. The difference between the virtual surface of the piston needle and the lower surface of the piston head forms the piston surface for generating pressure on the material. The lower surface of the piston head is cooled together by piston cooling, thereby locally reducing the viscosity of the melt or plastic material at the bottom of the piston. Thereby, it is prevented that the liquid melt can flow into the direction of the drive device, thereby not only preventing the piston from being clamped by the piston bush and becoming immovable, but also preventing the intrusion of the melt into the drive device. Furthermore, when retracted, the material can more easily separate from the bottom of the piston or the lower surface of the piston head, so that when the starting point or initial point of the piston is reached, the solid-phase material or granules can be easily refilled without the residual material adhering to the bottom of the piston. It is preferable that a temperature sensor is attached to the lower surface of the piston head or to the bottom of the piston. Based on the arrangement of the temperature sensor, piston position-dependent thermal management of the print head is possible, thereby enabling faster heating of the material without the melt contacting the lower surface of the piston head. Thereby, there is an advantage that the filling process of the print head can be accelerated. The piston head is preferably manufactured as a cylindrical component and made of a heat-resistant material. The combination of manufacturing the first piston portion from aluminum and the piston head from, for example, steel has proven to be preferable as the piston thus has an elastic upper region for receiving mechanical stress and a heat-resistant lower region in the region of the material to be heated. The piston needle partially penetrates or fully penetrates into the bore of the kidney-shaped part according to the piston position, thereby having the advantage that the piston needle is guided in the central bore of the kidney-shaped part.

[0020] The hollow chamber is arranged inside the piston bush and is formed by a volume part whose outer surface is formed by the inner surface of the piston bush, the outer surface of the piston needle, the upper surface of the kidney-shaped part, and the lower surface of the piston. Inside the hollow chamber, due to the movement of the piston, the material or granules are compressed through the lower surface or the piston surface of the piston head. During the compression of the material, the thermal management of the print head is adjusted so that the material is formed as a plastic phase rather than a liquid phase or melt being formed inside the hollow chamber. Thereby, there is an advantage that the plasticized material does not adhere to the lower surface of the piston. However, during compression, a part of the liquid phase or melt exits the melt chamber through the opening of the concentrically arranged kidney-shaped part by the piston needle entering the melt chamber and is pushed into the hollow chamber of the piston bush. At this time, each part of the melt is mixed with each part of the plastic phase. At this time, the melt releases energy to the plastic phase, thereby having the advantage that a more uniform material is generated. In this way, the kidney-shaped part is a mixer or a static mixer. This is because there is an advantage that no other moving parts are required other than the piston movement to mix the plastic phase with the liquid phase. Thus, the configuration of the kidney-shaped part acts for the blending action leading to improved mixing of the material or melt and the plasticized material. The kidney-shaped part guides the heating energy of the heating member to both the nozzle head and the piston needle, which acts for improved energy management when the melt is heated.

[0021] The kidney-shaped part may be manufactured as a separate component in the first embodiment or may be integrally formed with the piston bush in the second embodiment.

[0022] In a preferred development example of the present invention, during the compression process for producing the liquid phase of the material, the nozzle is closed, the piston needle sinks into the melt chamber, whereby a part of the liquid phase is pushed out from the upper region of the melt chamber through the opening of the kidney-shaped part into the hollow chamber of the piston bush, and thereby the pushed-out part of the liquid phase is mixed with the plastic phase in the hollow chamber (40).

[0023] During mixing, the melt releases energy to the plastic phase, thereby having the advantage of producing a more uniform material. The mixing is carried out in the mixing zone of the print head, and the mixing zone forms a mixer during the compression process together with each component arranged therein. This is because, in addition to the piston movement during compression, there is an advantage that no other moving parts are required for mixing the liquid phase and the plastic phase. During the holding process described later, the piston is stationary in the holding position, and the mixing described above is carried out without the movement of each component. Therefore, during the holding process of the compression process, the mixing zone can also be called a static mixer.

[0024] In a development example of the present invention, the print head has different state zones from the upper partial region of the piston bush through the kidney-shaped part to the nozzle, and these state zones represent the aggregation state of the material depending on its temperature T S At this time, the aggregation state of the material is variable from the solid phase through the plastic phase to the liquid phase across each state zone.

[0025] The state zones of the print head include a low-temperature zone where the material is in the solid phase, a plasticizing zone where the material is in the plastic phase, a melt zone and a process zone where the material is in the liquid phase respectively, and a mixing zone where the material is in the plastic phase and the liquid phase.

[0026] Furthermore, the cooling device on the flange and the piston cooling part integrated in the piston control the temperature T S Of the plastic phase of the material in the plasticizing zone, also in that case, to the glass transition temperature T gIt is intended to keep it below, and when it exceeds this glass transition temperature, the material will be plasticized and transition to the liquid phase.

[0027] This is synonymous with the piston bottom surface only contacting the solid phase of the material and not contacting the fully plasticized phase. The fully plasticized phase has a highly viscous adhesive consistency with a strong tendency towards surface adhesion. When the piston contacts such a phase, it may adhere to it, and as a result, for example, when the piston is retracted, the additional flow of new granules is hindered. There is an advantage in avoiding such an effect.

[0028] In one development example, the nozzle head includes two heating zones. In the first heating zone, a partial region of the plasticizing zone, a mixing zone, and a partial region of the melt zone are arranged, and the first heating member is arranged on the upper nozzle head so that heat energy can be injected into the material from the first heating member through the lower partial region of the piston bush, the kidney-shaped part, and the partial area of the upper nozzle head.

[0029] In one development example, heat energy can be injected from the first heating member through the kidney-shaped part to the piston needle inside the bore. The contact of the piston needle inside the bore additionally acts for heating the piston needle, and thereby there is an advantage in that the temperature of the melt is quickly increased to the required process temperature.

[0030] In the second heating zone, a partial region of the melt zone and a process zone are arranged, and the second heating member is arranged on the lower nozzle head so that heat energy can be injected from the second heating member through the lower nozzle head into the liquid phase of the material.

[0031] The placement of both heating zones on the nozzle head serves for more efficient heat management of the print head. This is because the thermal energy of the first heating zone serves for the preferred pre-plasticization of the material without the material transitioning into the liquid phase. Thereby, there is the advantage that the piston does not stick during compression and the print head functions without problems. Such an effect is optimized by the cooperative action with the cooling device of the flange. Furthermore, when the material in the plasticized phase is pre-plasticized and the piston is sent, the actuator device requires even lower force costs, whereby there is the advantage that a smaller actuator can be used for the feeding of the piston. This reduces the cost of the equipment and leads to improved dynamics of the print head. This is because the weight of the print head is reduced. Thereby, during so-called track control for creating the components, the print head can be accelerated and decelerated better. In the second heating zone, a melt is generated, and the thermal energy injected serves for a relatively constant melt temperature across the entire melt chamber. The melt temperature can be controlled within the second heating zone so that the material is not heated too strongly. Thereby, there is the advantage that the formation of decomposition products such as, for example, especially gases due to too high a heat load can be avoided, which, due to the pressure prevailing in the system, accelerates the further decomposition of the material and directly has a negative impact on its quality.

[0032] Regarding the state zone of the print head, during the compression process for producing the liquid phase of the material in the process zone, the nozzle is closed, the piston needle sinks into the melt chamber, whereby a part of the liquid phase is pushed out from the upper region of the melt chamber through the opening of the kidney-shaped part back from the melt zone to the mixing zone, whereby a part of the liquid phase from the melt zone is mixed with the plasticized phase from the plasticizing zone in the mixing zone. During mixing, the melt releases energy to the plastic phase, thereby producing a more homogeneous material. The mixing zone forms a mixer or static mixer during the compression process together with each component arranged therein. This is because, other than piston movement, there is an advantage that no other moving parts are required to mix the plastic phase with the liquid phase.

[0033] Inside the melt chamber, there is a pressure sensor for the pressure p of the liquid phase L and / or a temperature sensor for the temperature T L is arranged. The measurement of the pressure p L is a primary parameter for determining the discharge or expulsion of the melt from the outlet opening or the mass flow rate. The additional measurement of the temperature T L enables taking into account the temperature dependence of the viscosity of the material in determining the mass flow rate Q. By means of piston feed, the quantity to be metered can be accurately controlled. For the quality of the component or object to be manufactured, the control of the temperature T L in particular in the form of constant and accurate control is even more important to avoid thermal degradation of the material.

[0034] Furthermore, the actuator device and / or the piston are provided with a stroke measurement system for the position s of the piston, and / or a sensor for the force F exerted by the piston on the material, or a sensor for the hydraulic pressure p H exerted on the piston. The feed of the piston serves as a guide for the quantity of material to be discharged. This quantity can be controlled in particular through the stroke measurement system. Furthermore, the force F is directly correlated with the pressure of the material.

[0035] On the piston, in particular on the lower surface of the piston head of the piston, a temperature sensor for the temperature T K of the plastic phase of the material may be arranged. Based on such an arrangement of the temperature sensors, heat management of the print head dependent on the piston position is possible, thereby enabling faster heating of the material without the melt contacting the lower surface of the piston head. As a result, there is an advantage that the filling process of the print head can be accelerated or the time required for the filling process can be shortened.

[0036] Furthermore, a control and regulation unit may be provided for the active control of the actuator device for moving the piston according to the operating strategy to be executed for filling and printing, and for the active control of the temperature of the heating member of the nozzle head. Furthermore, an evaluation unit may be provided that evaluates the measured values of the sensors and transfers the results to the control and regulation unit for the active control of the actuator device and for the active control of the heating member. By detecting and evaluating the sensor values depending on each operating state, the functionality of the print head can be checked, and as a result, there is an advantage that defects and errors in the process can be indicated early. Furthermore, by detecting the sensor values, defined target values can be adjusted. It is also possible to calculate a correction factor and transmit it to the control and regulation unit. This correction factor can be added to the target value, for example, and as a result, there is an advantage that a desired constant discharge of the melt from the nozzle can be achieved. The active control of the heating member enables dynamic control of the temperature, which has the advantage of affecting both heating and cooling. For example, when the thermal energy of the first heating member is reduced by the control and regulation unit, the cooling at the flange continues, and this cooling extracts energy from the plastic phase of the material, thereby rapidly cooling the plastic phase.

[0037] Furthermore, the present invention relates to a method of operating a print head according to the present invention, the method including the following steps: - The hollow chamber is filled with printable material by a supply device, - Starting from the start position, the opening cross-section of the piston bush is closed by the movement of the piston in the direction of the nozzle, - The material is compressed, - The material is converted from a solid phase to a liquid phase, - Until the final position of the piston is reached or the component is completed, the liquid phase of the material is ejected from the nozzle to print a three-dimensional component, - The piston moves back to the start position, - From the step "filling" to "ejection of the liquid phase" is repeated until the end of the method.

[0038] Most of the compression and conversion processes are carried out simultaneously. This is because during both of these processes, thermal energy is injected into the print head through both heating zones.

[0039] Furthermore, at least closing, compression, conversion, and ejection can be carried out by the active control of the actuator device by the control and regulation unit, and the results of the evaluation unit from the measured values of the sensors are transferred to the control and regulation unit.

[0040] In a development example of the method of the present invention for operating the print head, the compression process includes the following steps: - The material is pre-compressed by the feed of the piston, - The nozzle is closed, - The material is compressed by the feed of the piston, - The piston is held in the holding position.

[0041] Pre-compression is carried out by force control or pressure control of the piston by the actuator device, and the target position of the piston bottom surface is in the first third of the plasticizing zone starting from the low-temperature zone. The granules are compressed by the piston feed in the plasticizing zone, and at the same time, in the melt zone, there is a melt between the hollow chamber and the nozzle. The plasticized granules are thereby pushed into the melt in the mixing zone. By the descent of the piston and, along with it, the descent of the piston needle in the direction of the nozzle, the melt has already been discharged from the nozzle, thereby realizing the advantage that any air or bubbles that may still be present are pushed out from the nozzle head. Thereby, the nozzle is emptied.

[0042] After reaching the target position of pre-compression, the nozzle of the print head is closed.

[0043] To compress the material, the piston is sent in a pressure-controlled manner by the actuator device until it reaches the defined peak pressure and, along with it, the peak pressure position. At this time, in one development example of the method of operating the print head, the nozzle is closed during compression, the piston needle sinks into the melt chamber, whereby a part of the liquid phase is pushed out so as to return from the upper region of the melt chamber through the opening of the kidney-shaped part to the mixing zone from the melt zone, whereby a part of the liquid phase is mixed with the plastic phase from the plasticizing zone in the mixing zone.

[0044] Then, during a pre-defined time period depending on the material, so to speak, the peak pressure position is held, and thus, the peak pressure position is also the holding position of the print head. In one development example of the method, the nozzle is closed during the holding of the piston at the holding position, the piston needle sinks into the melt chamber, whereby a part of the liquid phase is pushed out so as to return from the upper region of the melt chamber through the opening of the kidney-shaped part to the mixing zone from the melt zone, whereby a part of the liquid phase is mixed with the plastic phase from the plasticizing zone in the mixing zone.

[0045] The holding process expels residual air, and the melt is homogenized in the mixing zone C. As a result, there is an advantage that an improved energy flow is realized and a more uniform material is produced. The recirculating melt becomes plastic, and the proportion of granules pushed into the kidney-shaped part becomes molten. Thereby, mixing of the material occurs. The holding process described here further has the advantage of serving for the analysis of the print head and system checks. This is because the following effects can occur during the pressure measurement of the pressure. The pressure increase of the pressure in the melt would mean that the melt gasifies, for example because the temperature of the melt is too high. An overly high melt temperature is not desirable. This is because there is a possibility of generating air plasma, which leads to chemical disintegration. A significant pressure drop in the melt pressure could, for example, mean that the system of the print head is not airtight or that there is still too much air in the system. Such an effect can occur, for example, when the temperature management of the print head is not optimally adjusted and there is an excessive amount of low-temperature material in the hollow chamber.

[0046] This method has the advantage of enabling the realization of an invariant and constant track thickness from the first droplet.

[0047] The evaluation unit may be manufactured separately from the control and regulation unit or may be integrated therewith.

[0048] For yet another measure to improve the present invention, it will be described in detail below together with the description of the preferred embodiments of the present invention with reference to the drawings.

Brief Description of the Drawings

[0049]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

DETAILED DESCRIPTION OF THE INVENTION

[0050] FIG. 1 shows a print head 100 for a 3D printer, which includes an actuator device 110 arranged in the housing 1 of the print head 100 for controlling the piston 3, a supply device 2 for the printable material 10, a flange 5 having a cooling device 50 arranged in the housing 1 and the supply device 2, a nozzle head 6 having heating members 61, 63 for converting the material 10 from the solid phase 10 through the plastic phase 11 to the liquid phase 12, and a nozzle 8 for discharging the liquid phase 12 of the material 10 from the nozzle head 6. The print head 100 includes a separate piston bush 4 for guiding the piston 3.

[0051] The flange 5 internally cooled by the cooling device 50 acts to thermally isolate the heated lower region of the print head 100 from the actuator device 110 or the drive part of the piston 3.

[0052] The piston 3 includes a first piston part 31 for connecting the piston 3 to the actuator device 110 and a piston head 34 attached to the first piston part 31 and accommodating the piston needle 32 in the direction of the nozzle 8. On the piston 3 or on the lower surface 35 of the piston head 34, the temperature T of the plastic phase 11 of the material KA temperature sensor 36 for measuring is arranged. The lower surface 35 of the piston head 34 forms the piston bottom surface 35. The first piston portion 31 is preferably configured as an aluminum hollow piston, and this hollow piston has a hollow chamber configured as a cooling passage inside. At the lower end of the first piston portion 31, a piston cooling portion 33 cooled through a coolant system is arranged. The piston cooling portion 33 acts for the solidification of the materials 11, 12 at the piston bottom surface 35, thereby sealing the piston 3 in the direction of the actuator device 110, or thereby preventing the inflow of the molten liquid 12 of the liquid in the direction of the actuator device 110. Preferably, a coolant is used as the coolant, and the coolant passes through the housing 1 via a connection portion and a flexible pipe and is sent to the cooling connection portion 37 of the first piston portion 31. The cooling device 50 on the flange 5 also receives the supply of the coolant by the same coolant system.

[0053] When the materials 11, 12 are cooled at the piston bottom surface 35, the viscosity of the materials 11, 12 locally decreases, and thereby, when the piston 3 is pulled back, the materials can leave from here without drawing a thread. At this time, a space for the new material 10 is created.

[0054] FIG. 1 shows the piston 3 in an initial position for filling the print head 100 with the printable material 10 supplied to the print head 100 via the supply device 2.

[0055] The supply device 2 is configured in a funnel shape, and a material 10, which is preferably granular, is fed into the opening of the supply device 2 from above. The material 10 reaches, by gravity, the opening 21 or the opening cross-section of the piston bush 4. In the lower region of the supply device 2 above the opening cross-section 21, an air passage 20 is arranged. This air passage is loaded by an air impact by means of a pneumatic valve 22. The pneumatic valve 22 and the air passage 20 constitute a blowing device that loads the granules 10 with an air impact at intervals and throws them in the direction of the region of the supply device 2 located further above, so that the individual granule particles 10 are separated from each other. When the air flow is switched off, the granules 10 in the lower region of the supply device 2 fall into the piston bush 4 under the open opening cross-section 21. Thereby, the blowing device of the supply device 2 prevents the granule particles 10 from clogging and becoming immovable, thereby preventing the supply device 2 from being blocked, and thereby acting so that the piston bush 4 is reliably filled with the granules 10. Furthermore, a smaller diameter can be applied at the inlet of the supply device 2. The refilling process requires a back-blowing of the granules 10, thereby causing an effect that the granules float, so that as a result, they subsequently slide into the printing head 100. Blowing up is essential for automatic applications, and the granules 10 slide down due to the occurring gravitational impact or shock.

[0056] The piston bush 4 has an upper partial region 41 that penetrates into the flange 5 and a lower partial region 42 that penetrates into the upper partial region 60 of the nozzle head 6. A stopper 43 is arranged between the upper partial region 41 and the lower partial region 42 of the piston bush 4, whereby the flange 5 and the nozzle head 6 are separated from each other. The opening 21 or the opening cross-section is arranged in the upper partial region 41 of the piston bush 4, and has a gate 44 on the inner surface of the piston bush 4. The gate 44 causes the granules 10 to be sheared between the gate 44 and the piston bottom surface 35 by the piston 3 until the piston bottom surface 35 reaches a position below the gate 44 when the opening cross-section 21 is closed.

[0057] The piston bush 4 has an obtuse angle at the gate 44, and this obtuse angle is in the form of a sharp edge and is hardened. At this time, local hardening is preferred. The gate 44 may be formed by a separate insert in the form of a throw-away tip in an alternative embodiment. The designed form of the gate 44 has the advantage of acting to reduce the force required to shear the granules 10, thereby saving energy and reducing the likelihood of wear between the materials of the piston bush 4 and the piston 3. At this time, the edge of the gate 44 is extremely prone to wear.

[0058] According to the present invention, a kidney-shaped part 7 is arranged in a lower partial region 42 of the piston bush 4. The kidney-shaped part 7 has a bore 70 extending centrally for accommodating the piston needle 32 of the piston 3. The kidney-shaped part 7 has concentrically arranged openings 71 that form a fluid connection between a hollow chamber 40 arranged in the piston bush 4 and a melt chamber 81 arranged in a lower part 62 of the nozzle head 6. The hollow chamber 40 is arranged inside the piston bush 4 and is formed by the inner surface of the piston bush 4, the outer surface of the piston needle 32, the upper surface of the kidney-shaped part 7, and the lower surface 35 of the piston 3.

[0059] One preferred role of the kidney-shaped part 7 is in the heat conduction or energy transfer from the heating members 61, 63 of the nozzle head 6 to the liquid phase 12 or melt 12 of the material. This is achieved in particular by an increase in the contact surface with the hollow chamber 40 and, accordingly, with the plastic phase 11 of the material. Another role is in guiding the piston needle 32. The contact of the piston needle 32 inside the bore 70 additionally serves for heating the piston needle 32 to the required process temperature. The thermal energy of the first heating member 61 can be injected inside the bore 70 into the piston needle 32 via the kidney-shaped part 70. The final process temperature is only achieved in the nozzle head 6 towards the nozzle 8.

[0060] During the filling process of the printing head 100, the nozzle 8 is closed as required, and under the control of the piston 3 by the actuator device 110, the materials 10, 11, 12 arranged in the hollow chamber 40 and the melt chamber 81 are compressed by piston feeding.

[0061] During the compression process 230 for producing the liquid phase 12 of the material, the nozzle 8 is closed, and the piston needle 32 sinks into the melt chamber 81, so that a part of the liquid phase 12 is pushed out from the upper region of the melt chamber 81 through the opening 71 of the kidney-shaped part 7 and returns to the hollow chamber 40 of the piston bush 4, whereby the pushed-out part of the liquid phase 12 is mixed with the plastic phase 11 in the hollow chamber 40.

[0062] The nozzle head 6 includes the heating members 61, 63 of the printing head 100. The first heating member 61 is arranged on the upper nozzle head 60, and the second heating member 63 is arranged on the lower nozzle head 62. The upper nozzle head 60 has a partial area 64 on which the kidney-shaped part 7 is placed, and the partial area 64 is arranged between the upper nozzle head 60 and the lower nozzle head 62. In the area of the nozzle 8, a cooling ring 84 is arranged on the nozzle head 6. This cooling ring cools the component to be printed and thermally shields the component from the printing head 100.

[0063] The heating members 61, 63 of the nozzle head 6 heat the materials 10, 11, 12 in the hollow chamber 40, the kidney-shaped part 7, and the melt chamber 81 until the liquid phase 12 of the material reaches its process temperature and can be discharged from the nozzle 8. The melt chamber 81is configured to taper from the partial area 64 of the upper nozzle head 60 to the nozzle 8. The tapering of the melt chamber 81 enables an enhancement of the volumetric flow and prevents the deposition of material on the inner wall of the nozzle head 6. The smaller amount of material 12 or volume, compared to the cylindrical melt chamber 81, in the melt chamber 81 that tapers at the end optimizes the mixing process even further. Thereby, the piston needle 32 has to displace only a small volume in order to displace a part of the melt 12 through the opening 71 of the kidney-shaped part 7 from the melt chamber 81 back into the hollow chamber 40 during compression.

[0064] Furthermore, the print head 100 includes another sensor, and in the melt chamber 81, there are arranged a pressure sensor 83 for the pressure p L of the liquid phase 12 of the material and a temperature sensor 82 for the temperature T L of the material. Furthermore, another sensor is arranged in the actuator device 110, and there are provided a stroke measurement system 111 for the position s of the piston 3 and a sensor 112 for the force F exerted by the piston 3 on the materials 10, 11 or for the hydraulic pressure p H exerted on the piston 3. In an alternative embodiment, the sensors 111, 112 may be arranged on the piston 3 of the print head 100.

[0065] FIG. 2 shows a view of a part of the print head 100 according to the invention rotated by 90°, and there are shown the state zones A, B, C, D, E of the print head 100 filled with the materials 10, 11, 12 during operation, starting from the upper partial area 41 of the piston bush 4 through the kidney-shaped part 7 up to the nozzle 8. The state zones A, B, C, D, E represent the agglomeration state of the material 10 depending on its temperature T S and the agglomeration state of the material 10 can change from the solid phase 10 through the plastic phase 11 to the liquid phase 12 through the state zones A, B, C, D, E.

[0066] The temperature T of the materials 10, 11, 12 inside the print head 100 SOr the temperature profile is shown in the graph shown above the print head 100, and the temperature is shown over the stroke s, or over the length of the working area 120 of the print head 100.

[0067] The state zones A, B, C, D, E of the print head 100 include a low-temperature zone A where the material is in the solid phase 10, a plasticizing zone B where the material is in the plastic phase 11, a melt zone D and a process zone E where the material is in the liquid phase 12, respectively. Further, the state zone includes a mixing zone C where the material is in the plastic phase 11 and the liquid phase 12.

[0068] The cooling device 50 of the flange 5 and the piston cooling part 33 integrated with the piston 3 are intended to keep the temperature T of the plastic phase 11 of the material in the plasticizing zone B S below the glass transition temperature T in that case as well, and when this glass transition temperature is exceeded, the material 11 is plasticized and migrates to the liquid phase 12. The plasticizing zone B where the material is in the plastic phase 11 represents the state of the material or granules where the viscosity of the granules has already changed, thereby optimizing the compression process and the mixing process, but the plastic phase 11 of the granules has not yet migrated to the liquid phase 12. g Furthermore, the nozzle head 6 includes two heating zones 65, 66.

[0069] A partial region of the plasticizing zone B, the mixing zone C, and a partial region of the melt zone D are arranged in the first heating zone 65, and the first heating member 61 is arranged on the upper nozzle head 60, and heat energy can be injected from the first heating member 61 into the materials 10, 11, 12 through the lower partial region of the piston bush 42, the kidney-shaped part 7, and the partial area 64 of the upper nozzle head. A partial region of the melt zone D and the process zone E are arranged in the second heating zone 66, and the second heating member 63 is arranged on the lower nozzle head 62, and heat energy can be injected from the second heating member 63 into the liquid phase 12 of the material through the lower nozzle head 62.

[0070] As can be read from this graph, the temperature T of the materials 10, 11, 12 S continuously increases over the stroke s of the working area 120 of the print head 100. In the low temperature zone A, the action of the cooling device 50 of the flange 5 is dominant, whereby the granules 10 are only slowly heated over the stroke s. From the plasticizing zone B, the influence of the first heating zone 65 having the first heating member 61 increases, and the temperature curve rises significantly until it reaches the glass transition temperature T g and then the mixing zone C begins. The temperature T S has a low gradient in the mixing zone C and continues to rise until it reaches the melt zone D. There, the influence zone of the second heating zone 66 having the second heating member 63 begins, and after this heating member significantly raises the temperature T S of the melt 12, the process temperature of the melt 12 is reached in the process zone E, and a printable melt 12 is produced.

[0071] The temperature T S must be adjusted so that the granules 10 do not become clogged and immobile during filling, but can flow into the hollow chamber 40 so that shear of the materials 10, 11 at the gate 44 is possible with as little force cost as possible. At this time, the temperature management of the print head 100 is such that the cooling device 50 in the flange 5 injects a cooling temperature adjustment of about 40 °C into the piston bush 4 and thereby into the materials 10, 11, and the first heating member 61 of the first heating zone 65 injects a heating temperature adjustment of about 30 °C below the glass transition temperature T g or the melt temperature of the materials 10, 11, 12. Such an effect is supported by the piston cooling part 33. By cooling the materials 11, 12 at the piston bottom surface 35, the viscosity of the materials 11, 12 becomes locally low, whereby the material is peeled off without pulling a thread when the piston 3 is pulled back. At that time, when the piston 3 releases the opening cross-section 21 to the supply device 2, a space for the new material 10 is created.

[0072] The temperature sensor 36 on the bottom surface 35 of the piston measures the temperature T at the contact location between the piston 3 and the materials 10, 11, thereby enabling the calculation of the cooling output and heating output of the print head 100 so as not to exceed the glass transition temperature T of the material 10. Based on the arrangement of the temperature sensor 36 or temperature detector on the bottom surface 35 of the piston, the piston position-dependent control of the heating members 61, 63 and thus the adjustment of the temperature T are possible. Thereby, faster heating of the materials 11, 12 is achieved. In this way, the thermal management of the print head 100 also enables the processing of plastics having a low melting temperature of 60 to 80 °C or lower. K to measure, and thereby calculate the cooling output and heating output of the print head 100 so as not to exceed the glass transition temperature T of the material 10. g Based on the arrangement of the temperature sensor 36 or temperature detector on the bottom surface 35 of the piston, the piston position-dependent control of the heating members 61, 63 and thus the adjustment of the temperature T are possible. Thereby, faster heating of the materials 11, 12 is achieved. In this way, the thermal management of the print head 100 also enables the processing of plastics having a low melting temperature of 60 to 80 °C or lower. S to measure, and thereby calculate the cooling output and heating output of the print head 100 so as not to exceed the glass transition temperature T of the material 10.

[0073] During the compression process for producing the liquid phase 12 of the material in the process zone E, the nozzle 8 is closed. The nozzle 8 can be closed, for example, by a shut-off valve (not shown), or can be closed by positioning the print head 100 on the plate in the design space of the printer. Further, the nozzle 8 can also be closed by approaching the already printed area of the component 9. The piston needle 32 sinks into and further moves into the melt chamber 81 during the compression process, so that a part of the liquid phase 12 is pushed out from the melt zone D back to the mixing zone C, whereby in the mixing zone C, a part of the liquid phase 12 is mixed with the plasticized phase 11 from the plasticizing zone B. At this time, the liquid phase 12 from the melt zone D is pushed out to the mixing zone C so as to return from the upper region of the melt chamber 81 through the opening 71 of the kidney-shaped component 7 to the hollow chamber 40 of the piston bush 4.

[0074] Figure 3 shows a schematic diagram of a print head 100 according to the invention, having a control and regulation unit 113 for actively controlling an actuator device 110 for moving a piston 3, and an evaluation unit 114 configured to evaluate measured values of sensors 36, 82, 83, 111, 112 and transfer the results to the control and regulation unit 113 for active control of the actuator device 110 and for active control of heating members 61, 63. The control and regulation unit 113 is intended for active control of the actuator device 110 in accordance with an operating strategy to be executed for filling and printing, and for active control of the temperatures of the first heating member 61 and the second heating member 63. For the active control of the actuator device 110, reference is made to the sensor signals received by the evaluation unit 114 and the results calculated from the respective values. The pressure sensor 83 for the pressure p of the liquid phase 12, and the temperature sensor 82 for the temperature T L are arranged in the melt chamber 81. The stroke measurement system 111 for the position s of the piston 3, and the sensor 112 for the force F exerted by the piston 3 on the materials 10, 11 or for the hydraulic pressure p exerted on the piston 3 L is arranged on the actuator device 110 or the piston 3. H Furthermore, a temperature sensor 36 for the temperature T of the plastic phase 11 of the material is arranged on the piston 3. K

[0075] The signals s, F, p H , T K , T L , p L of the sensors 111, 112, 36, 82, 83, indicated by dashed arrows, are transmitted to the evaluation unit 114, subsequently evaluated there or in the cloud, and the results are transmitted as a control variable i to the control and regulation unit 113 in accordance with the operating strategy, and the actuator device 110 and the heating members 61, 63 are controlled accordingly.

[0076] Figure 4 shows a flowchart of a method 200 according to the present invention for operating the print head 100 according to the present invention, the method 200 including the following steps: - The hollow chamber 40 is filled 210 with printable material 10 by the supply device 2, - The opening cross-section 21 of the piston bush 4 is closed 220 by feeding or moving the piston 3 in the direction of the nozzle 8 starting from the start position 3a, - The material 10 is compressed 230, - The material is converted 240 from the solid phase 10 to the liquid phase 12, - The liquid phase 12 of the material is discharged 250 from the nozzle 8 to print a three-dimensional component 9 until the final position 3z of the piston 3 is reached or until the component 9 is completed, - The piston 3 moves back 260 to the start position 3a, - Steps 210 to 260 are repeated 270 until the end of the method 200. At least the closing 220, compression 230, conversion 240, and discharge 250 of the method 200 are performed by active control of the actuator device 110 by the control and regulation unit 113, and the results of the evaluation unit 114 from the measured values of the sensors 36, 82, 83, 111, 112 are transferred to the control and regulation unit 113.

[0077] Figure 5 shows a part of the print head 100 according to the present invention and two graphs 5a, 5b representing the pressure transition or pressure-force transition during the operation of the method 200 for operating the print head 100 or during various method steps. Figure 6 shows the different positions of the piston 3 in the various method steps or states shown in Figure 5 from the start position 3a of the piston bottom surface 35 to the final position 3z. During the execution of each method step, the cooling devices 50, 33 of the flange 5 and the piston 3 and the heating members 61, 63 are active, the melt chamber 81 and the kidney-shaped part 7 are filled with the melt 12, and in the lower partial region of the hollow chamber 40, the granules are still in the plastic phase 11.

[0078] A part of the illustrated print head 100 corresponds to the part of the print head 100 of the present invention shown in FIGS. 1 to 3, so the reference numerals in each of the above drawings are incorporated for the description of FIGS. 5 and 6, and new components and relationships, for example, the respective positions of the piston 3, are shown in FIGS. 5 and 6 with reference to the piston bottom surface 35.

[0079] FIG. 5 shows two curve transitions plotted on the first graph 5a above the stroke s that the piston 3 has advanced. The stroke s is measured by the actuator device 110 or a stroke measurement system 111 or stroke sensor 111 in the piston 3. The upper curve is for the force F exerted on the materials 10, 11 from the piston 3 or the hydraulic pressure p exerted on the piston 3 while the piston 3 is being sent by the actuator device 110 during the closing 220 and compression 230, H and represents the force-pressure transition. A force sensor or pressure sensor 112 is arranged on the actuator device 110 or the piston 3. The lower curve in the graph 5a represents the pressure transition of the melt pressure p in the melt chamber 81 L with respect to the stroke s of the piston 3 during the compression 230. A pressure sensor 83 for the pressure p L of the liquid phase 12 or the melt 12 is arranged in the melt chamber 81.

[0080] The second graph 5b shows a partial fragment of the lower curve in the first graph 5a, where again the pressure transition of the melt pressure p L in the melt chamber 81 is represented with respect to the stroke s of the piston 3 during the compression 230 (the curve transition from p c to p d ).

[0081] Figure 6a shows the start position 3a of the piston 3 during the filling process 210 of the print head 100, where the piston bottom surface 35 is positioned above the opening 21 of the piston bush 4. The filling process 210 is also called the replenishment process because it is a repeated procedure that can be arbitrarily repeated during the printing of the component 9. The position of the piston 3 shown in Figure 6a corresponds to the position of the piston 3 shown in Figure 1. The opening 21 or the opening cross-section 21 of the piston bush 4 is open, and the granules 10 can be introduced into the hollow chamber 40 of the piston bush 4 via the supply device 2. Subsequently, the piston 3 is controlled by the actuator device 110 to the position 3b shown in Figure 6b. At this time, the piston bottom surface 35 passes by the gate 44 of the piston bush 4, and the granules 10 protruding from the opening 21 into the hollow chamber 40 are sheared between the piston bottom surface 35 and the gate 44. Therefore, this position is called the shear position 3b. After the shearing, the opening cross-section 21 is closed 220. Force - pressure transition F, p H rises from the start position 3a to the shear position 3b, and the force consumption of the actuator device 110 is maximized at the gate 44 or the shear position 3b. This is because the actuator device 110 must apply a force to shear the granules 10. The force consumption can be reduced in relation to the properties of the piston bottom surface 35 and the preheating of the granules 10 by appropriate measures such as the optimization of the gate geometry. In contrast, the pressure transition p L of the melt 12 changes only slightly or hardly rises. This is because the nozzle 8 is still open and no pressure generation occurs in the melt chamber 81.

[0082] Subsequently, the piston 3 is moved by the actuator device 110 to the position 3c in a force-controlled or pressure-controlled manner. When the piston 3 moves, the force F exerted on the material or granules 10, 11 or the hydraulic pressure p exerted on the piston 3 H as well as the pressure p L in the melt 12 are measured. The sliding of the piston 3 pre-compresses the materials 10, 11, 12. Position 3c is defined by an increase in force or pressure, i.e., position 3c is adjusted, not directly, but rather the slope of the curve shown in graph 5a is adjusted. This slope transitions from a line with little or no increase (the region from position 3a to position 3c) to a curve where a predefined increase or predefined angle of increase is achieved and / or exceeded at the transition point p Lc ,F c ,p Hc and occurs at. Position 3c is in the first third of the plasticization zone B. The granules 10, 11 are compressed by the feed of the piston 3 in the plasticization zone B, and at the same time, there is a melt 12 in the melt zone D between the hollow chamber 40 and the nozzle 8. The plasticized granule 11 is thereby pushed into the melt 12 in the mixing zone C.

[0083] By the lowering of the piston 3 and, associated therewith, the lowering of the piston needle 32 in the direction of the nozzle 8, the melt 12 has already been discharged from the nozzle 8, thereby achieving that any air or bubbles that might still be present are pushed out of the nozzle head 6. Thereby the nozzle 8 is emptied.

[0084] Position 3c is given an allowable range from the process and material aspects, such that the position 3c of the piston 3 may vary slightly under the various filling processes of the print head 100 that are executed sequentially. Thus, position 3c is not a fixed point. If position 3c is within the predetermined allowable range, it is guaranteed that the filling process 210 has been successful, i.e., sufficient granules 10 have been introduced into the hollow chamber 40 and the melt chamber 81 is already filled with the melt 12. If the slope starts significantly before position 3c, for example, there is an excessive amount of high-viscosity or hard material 10, 11 in the region from the piston bottom surface 35 to the nozzle 8, and the mixing process in the mixing zone C may not be successful in some cases. If the slope starts significantly after position 3c, for example, in some cases, too little material 10 has been refilled.

[0085] After reaching position 3c, the nozzle 8 of the print head 100 is closed.

[0086] The preliminary compression 310 is complete, and for the compression 330, the piston 3 is sent in a pressure-controlled manner starting from position 3c to reach the pre-defined peak pressure p d until the piston bottom surface 35 moves to the position 3d shown in Fig. 6c. The peak pressure p d can be between approximately 100 and 300 bar, depending on the material 10 and requirements. During the compression process 330, the nozzle 8 is closed, the piston needle 32 sinks into the melt chamber 81, so that a part of the liquid phase 12 is pushed out from the upper region of the melt chamber 81 through the opening 71 of the kidney-shaped part 7 and returns from the melt zone D to the mixing zone C. Thereby, a part of the liquid phase 12 is mixed with the plastic phase 11 from the plasticizing zone B in the mixing zone C.

[0087] Then, during a pre-defined time period depending on the material, so to speak, the peak pressure position 3d to the holding position 3d is held. While the piston 3 is being held 340 at the holding position 3d, the nozzle 8 remains closed, the piston needle 32 sinks into the melt chamber 81, so that a part of the liquid phase 12 from the upper region of the melt chamber 81 is pushed out through the opening 71 of the kidney-shaped part 7 and returns from the melt zone D to the mixing zone C. Thereby, a part of the liquid phase 12 is mixed with the plastic phase 11 from the plasticizing zone B in the mixing zone C. At this time, the piston bottom surface 35 enters the first heating zone 65, the piston needle 32 enters the melt chamber 81, and during the holding, a part of the melt 12 flows from the melt chamber 81 of the nozzle head 6 through the opening 71 of the kidney-shaped part 7 into the plastic granular 10 therein so as to return to the mixing zone C. Thereby, the residual air is pushed out and the melt 12 is homogenized in the mixing zone C. Thereby, an improved energy flow is realized and more uniform materials 11, 12 are produced. The flowing-back melt 12 becomes plastic, and the proportion of the granules 11 pushed into the kidney-shaped part 7 becomes molten. Thereby, the mixing of the materials 11, 12 occurs. The holding process described here also serves to analyze the print head 100 and perform system checks. Pressure p L This is because the following effects can occur during the pressure measurement of. In the melt 12, pressure p L An increase in pressure means that the melt 12 gasifies, for example, because the temperature T L is too high. An overly high melt temperature T L is not desirable. There is a possibility of air plasma generation, which leads to chemical breakdown. A significant pressure drop in the melt pressure p L can mean, for example, that the system of the print head 100 is not airtight or that there is too much air still in the system. Such an effect can occur, for example, when temperature management of the print head 100 is not optimally adjusted and there is an excessive amount of low-temperature materials 10, 11 in the hollow chamber 40.

[0088] After the elapse of a predefined time period, the piston 3 moves back in a pressure-controlled manner by the actuator device 110 from the peak pressure position 3d to reach a target pressure p e of approximately 0 bar. The system is unloaded. Thereby, the melt 12 is depressurized and degassed, and thereby, especially in the process zone E, a pure melt 12 that is qualitatively of high value and has printing ability is generated. When the target pressure p e is reached, the target pressure position 3e shown in FIG. 6d is reached, and the piston bottom surface 35 is positioned outside the first heating zone 65 in the region of the stopper 43 of the piston bush 4. The pressure p d measured at this time at the peak pressure position 3d and the pressure p e at the target pressure position 3e, as well as the stroke s traveled between both points 3d, 3e, reveal the spring constant of the liquid phase 12 or the melt 12 of the material.

[0089] The spring constant is determined from the compressibility of the melt 12 and leads to a correction factor or form factor required for the precise control of the piston 3 by the actuator device 110. Based on the compressibility of the melt, for example, 1.2 volume units of the geometric piston stroke s by which the piston 3 advances corresponds to 1.0 volume unit of the volume of the melt 12 delivered. Without compressibility, the ratio should be 1:1.

[0090] Thereby, it is realized that the actuator device 110 can control the piston 3 in a controlled manner, and the spring constant enables, in particular, the actual discharge of the melt 12 to achieve the calculated exact volume flow rate of the melt 12 depending on the track speed of the moving print head 100 during printing. That is, at each printing position under each track speed of the print head 100, the required amount of the melt 12 is discharged toward the component 9 each time.

[0091] Next, the printing process 250 is prepared through an active decompression by pulling back the piston 3. At this time, the piston 3 is pulled back by about 1 to 2 millimeters depending on the determined spring constant, thereby realizing that the melt 12 does not come out when the nozzle 8 to the nozzle opening is subsequently opened. This will occur due to the influence of gravity based on the existing open system under the subsequent holding at position 3e. At the same time, the melt 12 is unloaded in the form of a spring.

[0092] Next, new printing preparation starts by compression. The entire system of the print head 100 is a compressible system as already explained, since the melt 12 can have a compression of, for example, about 20%. Therefore, the volume pushed out by the feed of the piston 3 does not correspond to the volume of the discharged material 12, and thus inaccurate and irregular discharges may occur. The volume of the melt 12 that can occur for the feed of the printing process 250 is defined by the target position 3e and the stroke up to the final position 3z shown in FIG. 6e. Based on the effects described above, the melt 12 is compressed during printing start. The compression of the melt 12 in the melt chamber 81 at the start of printing is generated partly through the friction at the nozzle opening of the nozzle 8 when the melt 12 is "pushed out", and partly through the resistance when the component 9 or the substrate support on which the component 9 is installed is printed on. The uniform discharge of the melt 12 is achieved by the intelligent control of the print head 100, and the asynchronous movement of the piston 3 adapted by the correction factor is performed by the use of an electronic transmission device in the actuator device 110. In particular, the correction factor obtained from the determined spring constant of the melt 12 interferes with the system so to speak. Therefore, the print head 100 according to the present invention has no limitation to a synchronous movement conforming to a normal NC system.

[0093] The printing process 250 is carried out in a pressure-controlled manner, and the pressure p of the melt 12 is constantly measured through the pressure sensor 83 in the nozzle head 6. L The measured pressure p L is the pressure generated by discharging the melt 12 towards the component 9 or the substrate support (when there is no component yet). Without such an effect of printing on the object, the back pressure at the nozzle 8 would not occur except for the frictional pressure, and therefore, too much material / melt 12 would be discharged from the nozzle 8. The printing process 250 is started by actively interfering with the melt 12 through the intelligent control and regulation of the piston 3. At that time, a "more" stroke is executed to compensate for the compressibility of the melt 12. In principle, too much melt 12 is pushed out from the nozzle 8 at this time, but in parallel with the interference with the melt 12, the pressure sensor 83 is read, and thereby corresponding pressure-dependent control can be performed. In such a case, it has been found that the electrically driven actuator device 110 is dynamic and very efficient.

[0094] During the printing process 250, the melt temperature T Sis continuously measured and the melt 12 in the heating zone 2 is controlled via the heating member 63 of the nozzle head 6 to the required target value of the process temperature in the region of the process zone E.

[0095] For the start of printing, the piston 3 is controlled by the actuator device 110 in accordance with the orbital speed of the print head 100, whereby the melt 12 is discharged from the nozzle 8. During the printing process, the control and regulation unit 113 of the print head 100 is activated and actively intervenes in the control of the actuator device 110, for example to add a target value by addition or an amount of the material 12 by addition, if necessary. For example, if a target value by addition is added, whereby more material 12 is discharged or extruded from the nozzle 8 than by continuous control, the result is an increase in the pressure p L also at the nozzle head 6. At this time, the target value by addition is an interfered value or an additional piston stroke that must be advanced in order to discharge the desired volume of the melt 12 according to the correction value determined from the spring constant. Thereby, a steady state is reached, whereby the amount of the melt 12 discharged towards the component 9 is kept constant.

[0096] By the feed of the piston 3 and as a result of the resulting pressure increase of the melt 12, the virtual "spring" of the melt 12 is compressed or becomes stiffer. The resulting engineering effect is servo-controlled by the control and regulation unit 113, whereby an exact amount of the melt 12 is subsequently discharged from the nozzle 8 during the printing process 250.

[0097] At this time, the use of the piston needle 32 acts for the favorable effect that it enables direct volume exclusion inside the melt 12 in the melt chamber 81, whereby a lower spring constant is achieved. The lower spring constant in turn enables high dynamics of the print head 100. This effect results from the more direct pressure transmission to the melt 12 by the piston needle 32. That is, when the piston 3 is pushed, not only the piston bottom surface 35 but also the piston needle 32 positioned closer to the nozzle 8 transmits a pressure impulse to discharge the melt 12 from the nozzle 8.

[0098] The printing process 250 can be executed at most until the piston bottom surface 35 reaches the position 3z, which is defined such that the piston bottom surface 35 does not reach a mechanical stopper but stops immediately before reaching the kidney-shaped part 7 as shown in FIG. 6e. Thereafter, the material 12 cannot be discharged, and the filling process 210 to the replenishment process described above is started again.

[0099] FIG. 7 shows a flowchart of the compression process 230 of the method 200 according to the invention for operating the print head 100 according to the invention.

[0100] The compression process 230 includes the following steps: - The materials 10, 11, 12 are pre-compressed 310 by pushing the piston 3, - The nozzle 8 is closed 320, - The materials 10, 11, 12 are compressed 330 by pushing the piston 3, - The piston 3 is held 340 at the holding position 3d.

[0101] Pre-compression 310 is carried out by force control or pressure control of the piston 3 by the actuator device 110. The target position 3c of the piston bottom surface 35 is at the first third of the plasticizing zone B starting from the low-temperature zone A. The granules 10, 11 are compressed by the feed of the piston 3 in the plasticizing zone B. At the same time, there is a melt 12 in the melt zone D between the hollow chamber 40 and the nozzle 8. The plasticized granules 11 are thereby pushed into the melt 12 in the mixing zone C. By the descent of the piston 3 and, accordingly, by the descent of the piston needle 32 in the direction of the nozzle 8, the melt 12 has already been discharged from the nozzle 8, thereby realizing that air or bubbles that may still exist are pushed out from the nozzle head 6. Thereby, the nozzle 8 is emptied.

[0102] After reaching the position 3c of the pre-compression 310, the nozzle 8 of the printing head 3 is closed 320.

[0103] For the compression 300 of the materials 10, 11, 12, the piston 3 is sent to a pressure control mode by the actuator device 11 until it reaches the defined peak pressure p d and, accordingly, the peak pressure position 3d or the holding position 3d. In one development example of the method 200 for operating the printing head 100, during the compression 330, the nozzle 8 is closed, the piston needle 32 sinks into the melt chamber 81, whereby a part of the liquid phase 12 is pushed out from the upper region of the melt chamber 81 through the opening 71 of the kidney-shaped part 7 back from the melt zone D to the mixing zone C, whereby a part of the liquid phase 12 is mixed with the plastic phase 11 from the plasticizing zone B in the mixing zone C.

[0104] Then, during a pre-defined time period depending on the material, so to speak, the peak pressure position 3d is held. Accordingly, the peak pressure position 3d is also the holding position 3d of the printing head 100.

[0105] In one development example of method 200, during the holding 340 of the piston 3 at the holding position 3d, the nozzle 8 is closed, the piston needle 32 sinks into the melt chamber 81, whereby a part of the liquid phase 12 is pushed out so as to return from the upper region of the melt chamber 81 through the opening 71 of the kidney-shaped part 7 to the mixing zone C from the melt zone D, whereby a part of the liquid phase 12 is mixed with the plastic phase 11 from the plasticizing zone B in the mixing zone C.

[0106] Residual air is pushed out by the holding process 340, and the melt 12 is homogenized in the mixing zone C. Thereby, an improved energy flow is realized, and there is an advantage that a more uniform material 12 is produced. The flowing-back melt 12 becomes plastic, and the proportion 11 of the granules pushed into the kidney-shaped part 7 becomes molten. Thereby, mixing of the materials 11 and 12 occurs. The holding process 340 described here also serves for the analysis and system check of the print head 100. Pressure p L This is because the following effects can occur during the pressure measurement of the pressure p. Pressure p in the melt 12 L An increase in pressure means that the melt 12 gasifies, for example because the temperature T of the melt 12 L is too high. An overly high melt temperature T L is not desirable. There is a possibility of generating air plasma, which leads to the chemical breakdown of the material 12. A significant pressure drop in the melt pressure p L can mean, for example, that the system of the print head 100 is not airtight or that there is still too much air in the system. Such an effect can occur, for example, when the temperature management of the print head 100 is not optimally adjusted and an excessive amount of the low-temperature material 10 is present in the hollow chamber 40.

Explanation of symbols

[0107] 1 Housing 2 Supply device 3 Piston 3d Holding position 4 piston bush 5 flange 6 nozzle head 7 kidney-shaped part 8 nozzle 10 material, solid phase 11 plastic phase 12 liquid phase 20 air passage 21 opening cross-section 22 air pressure valve 32 piston needle 40 hollow chamber 41 upper partial region 42 lower partial region 50 cooling device 60 upper nozzle head 62 lower nozzle head 61,63 heating member 64 partial region 65,66 heating zone 70 bore 71 opening 81 melt chamber 100 printing head 200 method 210 filling of the hollow chamber 220 closing of the opening cross-section of the piston bush 230 compression of the material 240 conversion of the material 250 discharge of the liquid phase 260 return movement of the piston 270 repetition of the step 310 preliminary compression of the material 320 closing of the nozzle 330 compression of the material 340 holding of the piston A, B, C, D, E state zones

Claims

1. A print head (100) for a 3D printer, comprising: an actuator device (110) for controlling a piston (3), disposed in a housing (1) of the print head (100); a supply device (2) for a printable material (10); a flange (5) having a cooling device (50), disposed on the housing (1) and the supply device (2); a nozzle head (6) having heating members (61, 63) for converting the material (10) from a solid phase (10) through a plastic phase (11) to a liquid phase (12); and a nozzle (8) for discharging the liquid phase (12) of the material (10) from the nozzle head (6). In the print head, a kidney-shaped part (7) is disposed in a lower partial region (42) of a separate piston bush (4), the kidney-shaped part (7) having a bore (70) extending centrally for receiving a piston needle (32) of the piston (3), the kidney-shaped part (7) having concentrically arranged openings (71), the openings forming a fluid connection between a hollow chamber (40) disposed in the piston bush (4) and a melt chamber (81) disposed in a lower part (62) of the nozzle head (6).

2. During a compression process (230) for producing the liquid phase (12) of the material, the nozzle (8) is closed and the piston needle (32) sinks into the melt chamber (81), whereby a part of the liquid phase (12) is pushed out from an upper region of the melt chamber (81) through the openings (71) of the kidney-shaped part (7) back into the hollow chamber (40) of the piston bush (4), whereby the pushed-out part of the liquid phase (12) is mixed with the plastic phase (11) in the hollow chamber (40). The print head (100) according to claim 1, characterized in that.

3. The printing head (100) has state zones (A, B, C, D, E) starting from an upper partial region (41) of the piston bush (4), passing through the kidney-shaped part (7) and reaching the nozzle (8), and the state zones (A, B, C, D, E) represent the agglomeration state of the material (10) depending on its temperature TS, and the agglomeration state of the material (10) is variable from a solid phase (10) to a plastic phase (11) and then to a liquid phase (12) across the state zones (A, B, C, D, E). The printing head (100) according to claim 1 or 2, characterized in that.

4. The state zones (A, B, C, D, E) of the printing head (100) include a low-temperature zone (A) where the material is in a solid phase (10), a plasticizing zone (B) where the material is in a plastic phase (11), a melt zone (D) and a process zone (E) where the material is in a liquid phase (12) respectively, and a mixing zone (C) where the material is in a plastic phase (11) and a liquid phase (12). The printing head (100) according to claim 3, characterized in that.

5. The nozzle head (6) includes two heating zones (65, 66), namely a first heating zone (65) and a second heating zone (66). The printing head (100) according to claim 4, characterized in that.

6. In the first heating zone (65), a partial region of the plasticizing zone (B), the mixing zone (C), and a partial region of the melt zone (D) are arranged, and a first heating member (61) is arranged on the upper nozzle head (60), and heat energy can be injected from the first heating member (61) to the material (10, 11, 12) through the lower partial region of the piston bush (42), the kidney-shaped part (7), and the partial area (64) of the upper nozzle head. The printing head (100) according to claim 5, characterized in that.

7. Heat energy can be injected from the first heating member (61) through the kidney-shaped part (7) to the piston needle (32) inside the bore (70). The printing head (100) according to claim 6, characterized in that.

8. The second heating zone (66) is arranged with a partial region of the melt zone (D) and the process zone (E), and a second heating member (63) is arranged on the lower nozzle head (62) so that thermal energy can be injected from the second heating member (63) through the lower nozzle head (62) into the liquid phase (12) of the material. The printing head (100) according to any one of claims 5 to 7, characterized in that.

9. In a method (200) of operating a printing head (100) according to any one of claims 1 to 8, The method (200) includes the following steps, The hollow chamber (40) is filled (210) with printable material (10) by the supply device (2), The opening cross-section (21) of the piston bush (4) is closed (220) by feeding the piston (3) in the direction of the nozzle (8) starting from the start position (3a), The material (10) is compressed (230), The material is converted (240) from the solid phase (10) to the liquid phase (12), The liquid phase (12) of the material is discharged (250) from the nozzle (8) to print the three-dimensional component (9) until the final position (3z) of the piston (3) is reached or until the component (9) is completed, The piston (3) makes a return movement (260) to the start position (3a), A method, characterized in that steps (210) to (260) are repeated (270) until the end of the method (200).

10. The compression process (230) includes the following steps, The material (10, 11, 12) is pre-compressed (310) by feeding the piston (3), The nozzle (8) is closed (320), The material (10, 11, 12) is compressed (330) by feeding the piston (3), A method (200) of operating a printing head (100) according to claim 9, characterized in that the piston (3) is held (340) at the holding position (3d).

11. During said compression (330), the nozzle (8) is closed and the piston needle (32) sinks into the melt chamber (81), whereby a part of the liquid phase (12) is pushed out so as to return from the upper region of the melt chamber (81) through the opening (71) of the kidney-shaped part (7) from the melt zone (D) to the mixing zone (C), whereby said part of the liquid phase (12) is mixed with the plastic phase (11) from the plasticizing zone (B) in the mixing zone (C), a method (200) for operating a print head (100) according to claim 10, characterized in that.

12. During the holding (340) of the piston (3) in said holding position (3d), the nozzle (8) is closed and the piston needle (32) sinks into the melt chamber (81), whereby a part of the liquid phase (12) is pushed out so as to return from the upper region of the melt chamber (81) through the opening (71) of the kidney-shaped part (7) from the melt zone (D) to the mixing zone (C), whereby said part of the liquid phase (12) is mixed with the plastic phase (11) from the plasticizing zone (B) in the mixing zone (C), a method (200) for operating a print head (100) according to claim 10, characterized in that.

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