Printhead for a 3D printer and method of filling the printhead

Abstract

The 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) with a cooling arrangement (50), arranged in the housing (1) and in the supply device (2), a nozzle head (6) with heating elements (61, 63) for converting the material from a solid phase (10) 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, the solid phase (10) of the material comprises granular particles (10) and the supply device (2) comprises a blowing device (25) for peeling the granular particles (10) from one another. The invention further relates to a method (210) for filling a print head (100), wherein a heatable cavity (40) of the print head (100) is filled with printable material (10) by means of a supply device (2).

Description

Technical Field

[0001] The present invention relates to a print head for a 3D printer and to a method of filling 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 work surface on which the object is to be produced is provided. At this time, only the work surface can move, or both the print head and the work 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 necessary to move to another position on the work surface and the material should not be applied along the path thereto. Switching can be performed, for example, by turning on or off the feeding of the solid starting material between these two operating states of the print head.

[0004] The most widespread is the "Fused Deposition Modeling" (FDM) method 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 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. The supply of the granules is carried out via a funnel-shaped inlet, but the granule particles can only slide inside the funnel based on gravity, and may become clogged and immobile during this process.

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 that enables obstruction-free filling and thereby a stable printing process, and also to provide a method for filling the print head.

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 filling 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 the housing of the print head, a supply device for 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 the material from a solid phase to a liquid phase, and a nozzle for discharging the liquid phase of the material from the nozzle head. According to the present invention, the solid phase of the material contains granular particles, and the supply device has a blowing device for separating the granular particles from each other.

[0011] Thereby, the blowing device of the supply device prevents the granular particles from clogging and becoming immovable, thereby preventing the supply device from being blocked, and thereby having the advantage of acting so that the print head is reliably filled with granules. Furthermore, a smaller diameter can be applied at the inlet of the supply device, thereby having the advantage of being able to embody a compact print head.

[0012] The actuator device for controlling the piston may be, for example, an electric motor having a mechanical transmission mechanism or a hydraulic drive unit having a hydraulic pressure source. The electric motor as the actuator device has a lower weight compared to the hydraulic drive unit, thereby having 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 unit has the advantage of realizing a high force when the piston is controlled.

[0013] The supply device for the printable material may be particularly intended as a supply unit for the material or starting material present as granules. The starting material may particularly be a thermoplastic material. By using granules as the starting material, it has been found that specific advantages are realized particularly with respect to the cost of the starting material of the printer compared to a print head using a filament made of a thermoplastic material.

[0014] When compared with a print head in which the granules are conveyed by a worm conveyor, the print head according to the present invention can be configured more compactly. This ultimately leads to the print head being simpler and easier to move. This is particularly advantageous when it is desired to move the print head at a very high speed, particularly at a speed of 100 mm / s or more.

[0015] The flange includes a cooling device, thereby achieving optimized heat management in the area of the supply device, and as a result, there is an advantage that adhesion of materials or granules to the piston is avoided. Furthermore, the nozzle head has a heating member for converting the material, particularly the solid phase which is granules, into the liquid phase. The heating device in the nozzle head has the advantage of acting for the precise injection of heat output to the material to be melted. Subsequently, the liquid phase or melt can be discharged through the nozzle of the nozzle head by piston movement.

[0016] The print head includes a separate piston bush for guiding the piston, and this piston bush enables the piston to be directly guided within the piston bush rather than being guided within the housing or cylinder of the print head. Thereby, there is an advantage that the possible wear occurs not directly on the inner wall of the housing or cylinder but inside the piston bush. The piston bush as a separate component provides the advantage of being replaceable when necessary. Furthermore, there is a possibility that pistons and piston bushes adapted to each other can be applied under various different diameters without other design changes, for example, in the flange or nozzle head.

[0017] In one development example, the blowing device includes a pneumatic valve and an air passage. In one development example, the air passage is arranged in the housing part of the supply device and communicates above the opening cross-section of the flange in the lower region of the supply device.

[0018] In a preferred development example of the present invention, the air passage can be loaded by an air impact by the pneumatic valve, and the air impact acts on the granular particles in the lower region so that they are separated from each other.

[0019] Furthermore, the present invention relates to a method for filling a print head according to the present invention, and the heatable hollow chamber of the print head is filled with a printable material by a supply device.

[0020] Filling the hollow chamber with printable material by the supply device includes at least the following steps: - Granular particles are introduced into the print head through the opening of the supply device, - An air impact is generated to separate the granular particles from each other.

[0021] In one development example, the introduction of the granular particles is carried out manually or automatically, and the granular particles slide into the lower region of the supply device under the influence of gravity.

[0022] In a preferred development example of the method, the generation of the air impact is carried out at intervals, and the granular particles are thrown up in the area of the air impact and, when falling again, impact the granular particles located below it to stimulate them to slide into the heated hollow chamber of the print head.

[0023] An efficient refill process requires back-blowing into the granules, which results in the effect of the granules floating, so that the granules subsequently slide into the print head. Throwing up or blowing up is essential for automatic applications and has the advantage that the granules slide down due to the resulting gravitational impact or impact. If necessary, clogged and immobile granules can also be separated by an air impact, which has the advantage of avoiding the downtime of the print head.

[0024] In the upper partial region of the piston bush, there are arranged openings or opening cross-sections enabling the supply of material from the supply device to the piston bush. In the lower region of the opening, there is arranged a gate formed at an obtuse angle with respect to the inner surface of the piston bush. 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 relevant part of the piston bush. There is the advantage that a longer service life and a quicker replacement of defective components are achieved by means of a separate piston bush and by the hardened region of the gate.

[0025] The piston includes a first piston part for connection to the actuator device and a piston head for connection to the first piston part and for accommodating the piston needle. The first piston part is preferably configured as an aluminum hollow piston, whereby there is the advantage that a coolant can be guided through the first piston part, thereby achieving 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 surface of the piston. Thereby, it is prevented that the liquid melt can flow into the direction of the drive device, whereby there is the advantage that not only is the piston jammed and immobile in the piston bush, but also the intrusion of the melt into the drive device is prevented. Furthermore, when retracted, the material more easily detaches from the bottom surface 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, easy refilling with solid-phase material or granules is possible without residual material adhering to the bottom surface of the piston. Preferably, a temperature sensor is attached to the lower surface of the piston head or the bottom surface of the piston. Based on the arrangement of the temperature sensors, 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. This has the advantage of enabling faster filling processes of the print head. The piston head is preferably manufactured as a cylindrical component and from a heat-resistant material. A combination where the first piston part is made of aluminum and the piston head is made of, for example, steel has been found to be preferred as the piston thus has an elastic upper region for receiving mechanical stress and a heat-resistant lower region in the area of the material to be heated. The piston needle partially penetrates or completely passes through the bore of the kidney-shaped part depending on the piston position, thereby having the advantage that the piston needle is guided in the central bore of the kidney-shaped part.

[0026] The kidney-shaped part has concentrically arranged openings that form fluid connections between a hollow chamber arranged in the piston bush and a melt chamber arranged in the lower part of the nozzle head.

[0027] The hollow chamber is arranged inside the piston bush and is formed by a volume whose outer surfaces are 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, materials or granules are compressed through the lower surface of the piston head or the piston surface. During the compression of the material, the thermal management of the printing head is adjusted such that the material is formed in 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 openings of the kidney-shaped parts arranged concentrically 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 of producing a more uniform material. Thus, 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 from the nozzle head to both the melt and the piston needle, which acts for improved energy management when the melt is heated.

[0028] 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.

[0029] The printing head has different state zones starting from the upper partial region of the piston bush and reaching the nozzle via the kidney-shaped part, and these state zones represent the agglomeration state of the material depending on its temperature T S At this time, the agglomeration state of the material varies from the solid phase through the plastic phase to the liquid phase across each state zone.

[0030] The state zones of the printing head include a low-temperature zone where the material is in a solid phase, a plasticizing zone where the material is in a plastic phase, a melting liquid zone and a process zone where the material is in a liquid phase respectively, and a mixing zone where the material is in a plastic phase and a liquid phase.

[0031] The cooling device on the flange and the piston cooling part integrated into the piston are intended to keep the temperature T of the plastic phase of the material in the plasticizing zone S below the glass transition temperature T g in this case as well. When the glass transition temperature is exceeded, the material is plasticized and will transition to a liquid phase.

[0032] 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 adhesiveness. When the piston contacts such a phase, it may adhere to it, and as a result, for example, the additional flow of new granules is hindered when the piston is retracted. There is an advantage in avoiding such an effect.

[0033] In the melting liquid chamber, a pressure sensor for the pressure p L of the liquid phase and / or a temperature sensor for the temperature T L are arranged. The measurement of the pressure p L is a primary parameter for determining the discharge or ejection of the melting liquid from the outlet opening or the mass flow rate. The additional measurement of the temperature T L makes it possible to also take into account the temperature dependence of the viscosity of the material when determining the mass flow rate Q. By means of the 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 a particularly constant and accurate form of 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 the hydraulic pressure p exerted on the piston. H A sensor is provided for this. The feed of the piston serves as a guide for the amount of material to be discharged. This amount can be controlled, in particular, through the stroke measurement system. Furthermore, the force F is directly correlated with the pressure of the material.

[0035] Furthermore, on the piston, in particular on the lower surface of the piston head of the piston, a temperature sensor for the temperature T of the plastic phase of the material K is arranged. Based on such an arrangement of the temperature sensor, thermal management of the print head depending 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 is 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 print head.

[0037] Furthermore, an evaluation unit is provided that is configured to evaluate the measured values of the sensors and transfer 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 sensor values depending on respective operating states, the functionality of the print head can be checked, which has the advantage of being able to display defects and errors in the process at an early stage. Furthermore, by detecting the sensor values, the defined target values can be adjusted. It is also possible that a correction factor is calculated and transmitted to the control and regulation unit. There is an advantage that this correction factor can be added to, for example, the target value, thereby realizing a desired constant discharge of the melt from the nozzle. 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 to proceed, and this cooling takes energy from the plastic phase of the material, thereby rapidly cooling the plastic phase.

[0038] Regarding yet another measure for improving 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

[0039]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0040] Figure 1 shows a print head 100 for a 3D printer, which includes an actuator device 110 arranged in a housing 1 of the print head 100 for controlling a piston 3, a supply device 2 for a printable material 10, a flange 5 having a cooling device 50 and arranged 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. The print head 100 includes a separate piston bush 4 for guiding the piston 3.

[0041] The flange 5 internally cooled by the cooling device 50 serves to thermally isolate the heated lower region of the print head 100 from the actuator device 110 or from the drive part of the piston 3.

[0042] 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 a 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, a temperature sensor 36 for measuring the temperature T of the plastic phase 11 of the material is arranged. The lower surface 35 of the piston head 34 forms the piston bottom surface 35. The first piston part 31 is preferably configured as an aluminum hollow piston, which has a hollow chamber configured as a cooling passage inside. At the lower end of the first piston part 31, a piston cooling part 33 cooled through a coolant system is arranged. The piston cooling part 33 acts to prevent 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 preventing the inflow of the liquid melt 12 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 part and a flexible pipe and is sent to the cooling connection part 37 of the first piston part 31. K ​ The cooling device 50 on the flange 5 also receives the supply of the coolant by the same coolant system.

[0043] When the materials 11, 12 are cooled at the piston bottom surface 35, the viscosity of the materials 11, 12 locally decreases, whereby when the piston 3 is pulled back, the materials leave therefrom without drawing a thread. At this time, a space for the new material 10 is created.

[0044] 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.

[0045] The supply device 2 is configured in a funnel shape, and the material 10, preferably in granules, is introduced into the opening 23 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 24 of the supply device 2 above the opening cross-section 21, an air passage 20 of the blowing device 25 for separating the granular particles 10 from each other is arranged. The air passage 20 is loaded by an air impact 26 by means of an air pressure valve 22. The blowing device 25 includes the air pressure valve 22 and the air passage 20, and the granules 10 are loaded by air injection at intervals and are thrown in the direction of the region of the supply device 2 located further above, whereby the individual granular particles 10 are separated from each other. When the blowing device 25 is turned off, the granules 10 in the lower region 24 of the supply device 2 fall into the hollow chamber 40 of the piston bush 4 under the opened opening cross-section 21. Thereby, the blowing device 25 of the supply device 2 prevents the granular particles 10 from clogging and becoming immovable, thereby preventing the blockage of the supply device 2, and thus acts to reliably fill the piston bush 4 with the granules 10. Further, a smaller diameter can be applied at the inlet of the supply device 2.

[0046] The piston bush 4 has an upper partial region 41 that projects into the flange 5 and a lower partial region 42 that projects 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. When the opening cross-section 21 is closed, 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.

[0047] 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, whereby energy can be saved and the tendency of wear in the materials of the piston bush 4 and the piston 3 is reduced. At this time, the edge of the gate 44 is extremely prone to wear.

[0048] A kidney-shaped part 7 is arranged in the lower partial region 42 of the piston bush 4, and the kidney-shaped part 7 has a bore 70 extending centrally for accommodating the piston needle 32 of the piston 3. Furthermore, 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 the 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.

[0049] One preferred role of the kidney-shaped part 7 is the heat conduction or energy transfer from the heating members 61, 63 of the nozzle head 6 to the liquid phase 12 or the melt 12 of the material. This is achieved in particular by the expansion of the contact surface with the hollow chamber 40 and, accordingly, with the plastic phase 11 of the material. Another role is the guidance of 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 final process temperature is achieved for the first time in the nozzle head 6 towards the nozzle 8.

[0050] During the filling process of the print head 100, the nozzle 8 is closed as required, and the materials 10, 11, 12 arranged in the hollow chamber 40 and the melt chamber 81 are compressed by piston feed under the control of the piston 3 by the actuator device 110.

[0051] The nozzle head 6 includes the heating members 61, 63 of the print 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 which 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 print head 100.

[0052] 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 81 is configured to taper from the partial area 64 of the upper nozzle head 60 to the nozzle 8.

[0053] 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 of the liquid phase 12 of the material L and a temperature sensor 82 for the temperature T L of the material. Yet another sensor is arranged in the actuator device 110, including 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.

[0054] The print head includes an evaluation unit (not shown) configured to evaluate the measured values of the sensors 36, 82, 83, 111, 112 and transfer the results to the control and regulation unit 113 for the active control of the actuator device 110 and for the active control of the heating members 61, 63. The control and regulation unit 113 is intended for the active control of the actuator device 110 to move the piston 3 in accordance with the operating strategy to be executed for filling and printing, and is also intended for the 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, the reference is the sensor signal received by the evaluation unit and the results calculated from the respective values. The pressure sensor 83 for the pressure p L 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 H exerted on the piston 3 are arranged on the actuator device 110 or on the piston 3. Furthermore, on the piston 3, a temperature sensor 36 for the temperature T K of the plastic phase 11 of the material is arranged.

[0055] Signals s, F, p of sensors 111, 112, 36, 82, 83 H , T K , T L , p L are transmitted to the evaluation unit, and subsequently evaluated there or in the cloud, and the result is transmitted as a control quantity to the control and regulation unit 113 in accordance with the operation strategy, and the actuator device 110 and the heating members 61, 63 are controlled accordingly.

[0056] FIG. 2 shows another view of the print head 100 according to the present invention. Based on the present invention, the solid phase 10 of the material contains granular particles 10, and the supply device 2 has a blowing device 25 for separating the granular particles 10 from each other. The blowing device 25 includes a pneumatic valve 22 and an air passage 20. The air passage 20 is arranged in the housing portion 27 of the supply device 2 and communicates above the opening cross-section 21 of the flange 5 in the lower region 24 of the supply device 2. The air passage 20 can be loaded with an air impact 26 by the pneumatic valve 22. The air impact 26 acts on the granular particles 10 in the lower region 24 so that they are separated from each other. The supply device 2 is configured in a funnel shape, and the granular particles 10 are introduced into the opening 23 of the supply device 2 from above. The material 10 reaches, by gravity, up to the opening cross-section 21 of the flange 5, or up to the piston bush 4, or up to the opening cross-section 21 of the piston bush 4. In the lower region 24 of the supply device 2 above the opening cross-section 21 of the flange 5, the air passage 20 of the blowing device 25 is arranged. The air passage 20 is loaded with an air impact 26 by the pneumatic valve 22. The blowing device 25 includes the pneumatic valve 22 and the air passage 20, and the granules 10 are loaded by the air impact at intervals and are thrown in the direction of the region of the supply device 2 located further above, whereby the individual granular particles 10 are separated from each other. When the blowing device 25 is turned off, the granules 10 in the lower region 24 of the supply device 2 fall into the hollow chamber 40 of the piston bush 4 under the open opening cross-section 21. Thereby, the blowing device 25 of the supply device 2 prevents the granular 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. The refilling process requires the back blowing of the granules 10, whereby an effect of floating the granules occurs, as a result of which this subsequently slips into the printing head 100. Blowing up is essential for automatic applications, and the granules 10 slip due to the generated gravitational impact or impact.

[0057] FIG. 3 shows a view in which a part of the printing head 100 according to the present invention is rotated by 90°, and the state zones A, B, C, D, E of the printing head 100 filled with the materials 10, 11, 12 during operation are shown from the upper partial region 41 of the piston bush 4 through the kidney-shaped part 7 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 to the plastic phase 11 and then to the liquid phase 12 through the state zones A, B, C, D, E.

[0058] The temperature T of the materials 10, 11, 12 inside the printing 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.

[0059] The state zones A, B, C, D, E of the print head 100 include the low-temperature zone A where the material is in the solid phase 10, the plasticizing zone B where the material is in the plastic phase 11, the melt zone D and the 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.

[0060] The cooling device 50 of the flange 5 and the piston cooling part 33 integrated into the piston 3 are for keeping the temperature T of the plastic phase 11 of the material in the plasticizing zone B S below the glass transition temperature T g in that case as well, and when exceeding this glass transition temperature, the material 11 will be plasticized and transition 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 transitioned to the liquid phase 12.

[0061] Furthermore, the nozzle head 6 includes two heating zones 65, 66. 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 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 to 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.

[0062] In the second heating zone 66, a partial region of the melt zone D and the process zone E are arranged, and the 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.

[0063] As can be read from this graph, the temperature T of the materials 10, 11, 12 S continuously rises 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, so that 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. Then, 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.

[0064] The temperature T S should be adjusted so that the granules 10 do not become clogged and immobile during filling and can flow into the hollow chamber 40 with as little force cost for shearing of the materials 10, 11 at the gate 44 as possible. At this time, the temperature management of the print head 100 is such that the cooling device 50 on 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. This effect is supported by the piston cooling section 33. The cooling of the material 11, 12 at the piston bottom surface 35 makes the material 11, 12 locally less viscous, so that when the piston 3 is pulled back, the material peels off from it without stringing, creating space for new material 10 when the piston 3 releases the opening cross section 21 to the supply device 2.

[0065] The temperature sensor 36 on the piston bottom surface 35 detects the temperature T K , thereby determining the glass transition temperature T g Based on the arrangement of the temperature sensor 36 or the temperature detector on the piston bottom surface 35, a piston position-dependent control of the heating elements 61, 63 and thus the temperature T S It is possible to adjust the heating temperature of the print head 100, thereby realizing a more rapid heating of the materials 11, 12. In this way, the thermal management of the print head 100 also allows the processing of plastics with low melting temperatures, below 60 to 80°C.

[0066] 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 by positioning the print head 100 on a plate in the design space of the printer. In addition, the already printed areas of the component 9 can be approached, thereby closing the nozzle 8. The piston needle 32 sinks into the melt chamber 81 during the compression process and moves further into it, so that a part of the liquid phase 12 is displaced from the melt zone D back to the mixing zone C, where it is mixed with the plastic phase 11 from the plasticization zone B. The liquid phase 12 from the melt zone D is then displaced from the upper region of the melt chamber 81 through the opening 71 in the kidney-shaped part 7 back to the hollow chamber 40 of the piston bush 4 and into the mixing zone C.

[0067] Figure 4 shows a flowchart of a method 200 for operating the print head 100 according to the present invention, and this method 200 includes the following steps: - The hollow chamber 40 is filled 210 with the 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 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 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 the active control of the actuator device 110 by the control and regulation unit 113, and the results of the evaluation unit from the measured values of the sensors 36, 82, 83, 111, 112 are transferred to the control and regulation unit 113.

[0068] 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.

[0069] 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. Therefore, the reference numerals in each of the above drawings are incorporated for the explanation of FIGS. 5 and 6. 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.

[0070] FIG. 5 shows two curve transitions plotted on the stroke s of the piston 3 advanced in the first graph 5a. The stroke s is measured by the actuator device 110 or a stroke measurement system 111 or a 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 The force-pressure transition is represented, and the force sensor or pressure sensor 112 is arranged in 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 with respect to the stroke s of the piston 3 during the compression 230. The pressure sensor 83 for the pressure p of the liquid phase 12 or the melt 12 is arranged in the melt chamber 81. L L

[0071] The second graph 5b shows a partial fragment of the lower curve in the first graph 5a. Here too, the pressure transition of the melt pressure p 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 L to p c to p d ).

[0072] 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.

[0073] Subsequently, the piston 3 is moved to the position 3c in a force-controlled or pressure-controlled manner by the actuator device 110. 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. Position 3c is defined by a force increase or a pressure increase, i.e., position 3c is adjusted such that, rather than a direct point, the gradient of the curve shown in graph 5a is adjusted. This gradient changes from a line with little or no increase (the region from position 3a to position 3c) to a curve increase (position 3c) where a predefined increase or a predefined angle of increase is achieved and / or exceeded at the transition point p Lc ,F c ,p Hc and occurs at Hc . Position 3c is in the first third of the plasticizing zone B. The granules 10, 11 are compressed by the feed of the piston 3 in the plasticizing zone B, and at the same time there is 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. By the lowering of the piston 3 and, associated therewith, the lowering of the piston needle 32 in the direction of the nozzle 8, it is achieved that the melt 12 is already discharged from the nozzle 8, whereby any air or bubbles that may still be present are pushed out of the nozzle head 6. Thereby the nozzle 8 is emptied.

[0074] Position 3c is given a tolerance 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 carried out successively. Thus, position 3c is not a fixed point. If position 3c is within a predetermined tolerance 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 melt 12. If the gradient starts, for example, well before position 3c, there is an excess of highly viscous 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 have been successful in some cases. If the gradient starts, for example, well after position 3c, there may have been refilled with too little material 10 in some cases.

[0075] After reaching position 3c, the nozzle 8 of the print head 100 is closed.

[0076] The preliminary compression is completed, and for compression 230, the piston 3 is sent in a pressure-controlled manner starting from position 3c to reach the pre-defined peak pressure p d before the bottom surface 35 of the piston 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 as required.

[0077] Next, during a pre-defined time period that depends on the material, the peak pressure position 3d is held, so to speak. At this time, the bottom surface 35 of the piston enters the first heating zone 65, the piston needle 32 enters the melt chamber 81, and while being held, 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 granules 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 11 of the granules 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 check the system. This is because the following effects can occur during the pressure measurement of the pressure p L . An increase in the pressure p L in the melt 12 would mean that the melt 12 gasifies, for example, because the temperature T L is too high. A melt temperature T L that is too high is not desirable. There is a possibility of generating air plasma, which leads to chemical disintegration. A significant pressure drop in the melt pressure p L could 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 could occur, for example, when the 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.

[0078] After the lapse of a pre-defined time period, the piston 3 is moved back in a pressure-controlled manner by the actuator device 110 from the peak pressure position 3d to reach an approximately zero-bar target pressure p e until reaching. The system is unloaded. Thereby, the melt 12 is depressurized and degassed, and thereby, especially in the process zone E, a pure melt 12 of high quality and printing ability is generated. The target pressure p e When reached, the target pressure position 3e shown in FIG. 6d is reached, and the piston bottom surface 35 is positioned in the region of the stopper 43 of the piston bush 4 outside the first heating zone 65. The pressure p at the peak pressure position 3d measured at this time d and the pressure p at the target pressure position 3e e The pressure difference between them, and the stroke s traveled between both points 3d, 3e clarify the spring constant of the liquid phase 12 or the melt 12 of the material.

[0079] The spring constant is obtained from the compressibility of the melt 12 and leads to a correction factor or form factor required for the accurate 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 advanced by the piston 3 correspond to 1.0 volume unit of the discharged volume of the melt 12. Without compressibility, the ratio should be 1:1.

[0080] Thereby, it is realized that the actuator device 110 can control the piston 3 in a controlled manner, and the spring constant enables the actual discharge of the melt 12 to achieve the calculated accurate volume flow rate of the melt 12, especially 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.

[0081] Next, the printing process 250 is prepared through active decompression by pulling back the piston 3. At this time, the piston 3 is retracted by about 1 to 2 millimeters depending on the determined spring constant, thereby realizing that the molten liquid 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 molten liquid 12 is load-reduced in the form of a spring.

[0082] Next, new printing preparation starts by compression. The entire system of the print head 100 is a compressible system as already described, since the molten liquid 12 can have a compression of, for example, about 20%. Therefore, the volume displaced by the feed of the piston 3 does not correspond to the volume of the ejected material 12, and for this reason, inaccurate and irregular ejection may occur. The volume of the molten liquid 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 molten liquid 12 is compressed during printing start. The compression of the molten liquid 12 in the molten liquid chamber 81 at the start of printing is generated partly through the friction at the nozzle opening of the nozzle 8 when the molten liquid 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. The uniform ejection of the molten liquid 12 is realized 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 determined from the determined spring constant of the molten liquid 12 interferes with the system so to speak. Therefore, the print head 100 according to the present invention does not have the limitation to a synchronous movement according to a normal NC system.

[0083] The printing process 250 is executed in a pressure control manner, and the pressure p of the molten liquid 12 is constantly measured through the pressure sensor 83 in the nozzle head 6. L The measured pressure p LIt is the pressure generated by discharging the melt 12 toward the component 9 or the base material 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, the stroke is executed "more" to compensate for the compressibility of the melt 12. In principle, too much melt 12 is extruded from the nozzle 8 at this time, but the pressure sensor 83 is read in parallel with the interference with the melt 12, 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.

[0084] During the printing process 250, the melt temperature T S is continuously measured and the melt 12 is controlled through the heating member 63 of the nozzle head 6 in the heating zone 2 to match the required target value of the process temperature in the region of the process zone E.

[0085] For printing start, the piston 3 is controlled by the actuator device 110 according to 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 adjustment 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 the amount of the material 12 by addition when necessary. For example, when a target value by addition is added, whereby more material 12 is discharged or extruded from the nozzle 8 than by continuous control, as a result, the pressure p at the nozzle head 6 LIt also increases. At this time, the target value by addition is the interfered value, or an additional piston stroke that must be advanced in order to discharge the melt 12 of the desired volume according to the correction value obtained from the spring constant. Thereby, a set state is reached, whereby the amount of the melt 12 discharged toward the component 9 is kept constant.

[0086] By the feed of the piston 3 and as a result of the pressure increase of the melt 12, the virtual "spring" of the melt 12 contracts or becomes more rigid. The resulting engineering effect is servo-controlled by the control and regulation unit 113, whereby an accurate amount of the melt 12 is discharged from the nozzle 8 during the subsequent printing process 250.

[0087] The use of the piston needle 32 at this time acts for the favorable effect that this enables direct volume exclusion inside the melt 12 in the melt chamber 81, whereby an even lower spring constant is achieved. The low spring constant enables, in turn, a high dynamics of the print head 100. This effect results from the even more direct pressure transmission to the melt 12 by the piston needle 32. That is, when the piston 3 is advanced, not only the piston bottom surface 35 but also the piston needle 32 positioned closer to the nozzle 8 transmit a pressure impulse in order to discharge the melt 12 from the nozzle 8.

[0088] 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 just before reaching the kidney-shaped part 7 as shown in FIG. 6e. Thereafter, the material 12 can no longer be discharged, and the filling process 210 or the replenishment process described above is started again.

[0089] FIG. 7 shows a flowchart of the method according to the invention for filling 210 the print head according to the invention, wherein the heatable hollow chamber 40 of the print head 100 is filled with the printable material 10 by the supply device 2.

[0090] Filling 210 of the hollow chamber 40 with the printable material 10 by the supply device 2 includes the following steps: - The granular particles 10 are fed 310 into the print head 100 through the opening 23 of the supply device 2, - An air impact 26 for separating the granular particles 10 from each other is generated 320.

[0091] The feeding 310 of the granular particles 10 is performed manually or automatically, and the granular particles 10 slide into the lower region 24 of the supply device 2 under the influence of gravity.

[0092] The generation 320 of the air impact 26 is performed at intervals, whereby the granular particles 10 are thrown up in the region of the air impact 26 and, when falling again, impact the granular particles 10 located thereunder to stimulate them to slide into the heated hollow chamber 40 of the print head 100.

Explanation of reference numerals

[0093] 1 Housing 2 Supply device 3 Piston 5 Flange 6 Nozzle head 8 Nozzle 10 Material, solid phase 12 Liquid phase 20 Air passage 21 Opening cross-section 22 Pneumatic valve 23 Opening 24 Lower region 25 Blowing device 26 Air impact 27 Housing part 40 Hollow chamber 50 Cooling device 61, 63 Heating member 100 Print head 210 Method 310 Feeding of granular particles 320 Generation of air impact

Claims

1. A print head (100) for a 3D printer, comprising: an actuator device (110) arranged in a housing (1) of the print head (100) for controlling a piston (3); a supply device (2) for a 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 from a solid phase (10) 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, the solid phase (10) of the material includes granular particles (10), and the supply device (2) has a blowing device (25) for separating the granular particles (10) from each other. The blowing device (25) includes a pneumatic valve (22) and an air passage (20). The air passage (20) is arranged in a housing portion (27) of the supply device (2) and communicates above an opening cross-section (21) of the flange (5) in a lower region (24) of the supply device (2). A print head characterized by this.

2. The air passage (20) can be loaded by an air impact (26) by the pneumatic valve (22), and the air impact (26) acts on the granular particles (10) in the lower region (24) so that they are separated from each other. The print head (100) according to Claim 1, characterized by this.

3. In a method (210) of filling the print head (100) according to Claim 1 or 2, a heatable hollow chamber (40) of the print head (100) is filled with a printable material (10) by the supply device (2). A method characterized by this.

4. The filling (210) of the hollow chamber (40) with the printable material (10) by the supply device (2) includes at least the following steps: granular particles (10) are introduced (310) into the print head (100) through an opening (23) of the supply device (2); An air impact (26) for separating the granular particles (10) from each other is generated (320). The method (210) according to Claim 3, characterized by this.

5. The input (310) of the granular particles (10) is carried out manually or automatically, and the granular particles (10) slide into the lower region (24) of the supply device (2) under the influence of gravity. The method (210) according to claim 4 is characterized by this.

6. The generation (320) of the air impact (26) is carried out at intervals. When the granular particles (10) are thrown up in the region of the air impact (26) and fall, they impact on the granular particles (10) located below them, thereby stimulating them to slide into the heated hollow chamber (40) of the printing head (100). The method (210) according to claim 5 is characterized by this.

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