TEMPERATURE CONTROL AND TRANSFER DEVICE FOR A 3D PRINTER, FOR TRANSFERRING AT LEAST ONE PLASTIC FILAMENT FROM A SOLID STATE TO A MELTED, VOCUSTIC PRINTING MATERIAL

Description

[0001] The invention relates to a tempering and transfer device for a 3D printer for converting at least one plastic filament from a solid state into a molten, viscous printing material. Furthermore, the invention relates to a 3D printer with such a device.

[0002] Such temperature control and transfer devices for 3D printers are known as hotends (see, for example, the Wikipedia entry "Prusa i3," accessed on August 7, 2021). CN 204 566 689 U discloses a multicolor 3D printer with exactly one nozzle (single nozzle). CN 205 310 843 U discloses a nozzle with two guide channels that run separately to an outlet. CN 205 326 302 U discloses a nozzle with a merging section in which two inlet channels merge to form one outlet channel. CN 205 951 287 U discloses a two-color print head for a 3D printer. EP 3 663 073 A1 discloses a tempering and transfer device for a 3D printer, for transferring at least one plastic filament from a solid state into a molten, viscous printing material, with a printing nozzle for dispensing the printing material and a base body.The base body comprises at least one filament channel with an inlet for feeding the at least one plastic filament and an outlet for discharging the printing material toward the print nozzle, as well as a heating receptacle for a heating unit. The heating receptacle is adjacent to a melt volume of the filament channel in which, during operation of the device, molten printing material is present by means of the heating unit. The base body is made of a metal with a thermal conductivity coefficient of less than 100 W / (mK). The filament channel is in thermally conductive connection to at least one heat sink for heat dissipation via an inlet-side cooling channel section of the filament channel. WO 2021 / 173618 A2 discloses various designs of hotends.

[0003] It is an object of the present invention to further develop a tempering and transfer device of the type mentioned at the outset in such a way that additional material classes can be used for the base body.

[0004] This object is achieved according to the invention by a temperature control and transfer device having the features specified in claim 1. According to the invention, it was recognized that by designing a temperature control and transfer device, also known as a hotend, for a base body metal made of a significantly lower thermal conductivity coefficient compared to aluminum, which is a standard material in the prior art, the possibility is created to select material classes not based on optimizing thermal conductivity, but rather based on other requirements. For example, a base body made of a food-safe metal can be used that complies, for example, with EU Regulations 1935 / 2004 and / or 2023 / 2006 with regard to manufacturing specifications. The hotend can then be used for applications in the food industry and / or medical technology. The base body material can be processed using laser beam melting.

[0005] The base body of the tempering and transfer device can be manufactured in one piece.

[0006] The filament channel is thermally connected to at least one heat sink for heat dissipation via an inlet-side cooling channel section. At least one such heat sink has proven effective for dissipating heat from the inlet-side cooling channel section to the environment. The heat sink is designed to direct cooling air to the cooling channel section.

[0007] The temperature control and transfer device can be connected to a heat conduction interruption component of a nozzle head of the 3D printer. The heat conduction interruption component can ensure extensive thermal decoupling of the temperature control and transfer device from upstream plastic filament guide components of the 3D printer. The material of the heat conduction interruption component has a thermal conduction coefficient that is usually less than 100 W(nK) and can be even lower. The material of the base body, on the one hand, and the material of the heat conduction interruption component, on the other hand, can have thermal conduction coefficients that differ by no more than 50%, no more than 20%, no more than 10%, or even no more than 5%. In particular, the material of the base body can have the same thermal conduction coefficient as the material of the heat conduction interruption component.

[0008] The base body can represent a component of the temperature control and transfer device, which is manufactured separately from the heat conduction interruption component and is mechanically connected to it.

[0009] A design of the base body according to claim 2 has proven particularly successful. The base body metal can be stainless steel. The carbon content of the base body metal can be in the range of 2%. The base body metal can contain chromium. The base body metal can contain nickel. The base body metal can contain molybdenum. The base body metal can be V2A or V4A stainless steel, in particular a steel with the material designation 1.4404 or 1.4452 or 1.4541.

[0010] A filament channel wall thickness design according to claim 3 results in the filament channel as a whole being able to quickly reach ambient temperature even if it is made of a material with a comparatively low thermal conductivity coefficient. The wall thickness of the filament channel between the inlet and outlet can be a maximum of 0.3 mm or a maximum of 0.2 mm. This wall thickness is usually greater than 0.01 mm. In the area of ​​an inlet connection, the wall thickness can also be higher.

[0011] The heat sink may comprise a plurality of cooling fins.

[0012] Active cooling according to claim 5 increases the cooling performance, allowing heat to be effectively dissipated from the inlet-side cooling channel section. The filament channel can then be effectively cooled on the inlet side, reducing thermal stress on the inlet-side components and, in particular, preventing unwanted filament melting there.

[0013] An embodiment of the heat sink according to claim 6 can ensure particularly effective heat transfer.

[0014] A spacing design according to claim 7 results in effective heat transfer between the heating unit and the melt volume, ensuring effective heating of the melt volume even when using a base metal with a low thermal performance coefficient. The distance between the melt volume and the heating unit receiving volume can be a maximum of 0.4 mm, a maximum of 0.3 mm, or a maximum of 0.2 mm. This distance is usually greater than 0.01 mm.

[0015] 3D printing of the base body of the device according to claim 8 enables, in particular, an optimized design of the plastic filament guide channels and / or an optimization of the desired heat transfer between the heating unit and the melt volume. Furthermore, it is possible to achieve inlet channel connections with a high temperature gradient to the melt volume, which in turn simplifies the cooling requirements of a print head comprising the temperature control and transfer device.

[0016] A sensor holder according to claim 9 facilitates coupling of the temperature sensor.

[0017] The advantages of a 3D printer according to claim 10 correspond to those already explained above with reference to the temperature control and transfer device. The same applies to the advantages of the plastic component produced with such a 3D printer.

[0018] An embodiment of the invention is explained in more detail below with reference to the drawing, in which: Fig. 1Main components of a 3D printer in the area of ​​a print head, to which a Fig. 1 schematically illustrated tempering and transfer device for transferring a plastic filament into a molten printing material, which is also referred to as a hotend; Fig. 2 a perspective view of the hotend shown in more detail and including a cooling fin arrangement; Fig. 3 a rear view of the hotend, seen from direction III in Fig. 2 ; Fig. 4 in a view from one of the Fig. 3 opposite direction a longitudinal section through the hotend along two filament channels running in a base body of the hotend; and Fig. 5 in one of the Fig. 4 corresponding sectional view of a base body of the hotend without a Figuren 1 bis 4 pressure nozzle shown.

[0019] Fig. 1 shows a printing nozzle head or print head 1 of a 3D printer 2 not otherwise shown. The 3D printer 2 is used in particular for applications in the food industry and / or medical technology.

[0020] The print head 1 has a temperature control and transfer device 3 for converting at least one plastic filament from a solid state into a molten, viscous printing material. Such a temperature control and transfer device is also referred to as a hotend.

[0021] The Hotend 3 is used in the version according to Fig. 1 For converting two plastic filaments from a solid state into a molten, viscous printing material, with the ability to select between the two plastic filaments. This can be used for a material change if a plastic component is to be manufactured from different plastic types, or for seamless 3D printing, where printing is carried out using the other plastic filament while one plastic filament is changed. Different filament types can have different plastic materials, different material qualities, or even different material colors.

[0022] In a version of the hotend not shown, this is used to transfer exactly one plastic filament from the solid state into the molten printing material.

[0023] The plastic filaments are not shown in the drawing and are fed into two inlet channel connections 4, 5 of a base body 6 of the hotend 3. The inlet channel connections 4, 5, also referred to as inlets, open via filament guide channels 6a, 6b (see Fig. 4 ) in the base body 6 and an outlet channel section 7 (outlets 7a, 7b, cf. Fig. 4 ) of the base body 6 into a print nozzle 8. The print nozzle 8 represents a component that can be detachably connected to the base body 6 of the hotend 3. The print nozzle 8 is used to dispense the print material during 3D printing.

[0024] Fig. 2 shows details of the hotend 3. End walls 9, 10 of the inlets 4, 5 provide connection points for a heat conduction interruption component 11 (cf. Fig. 1 ) of the nozzle head 1, which is also referred to as heatbreak and via which a substantial thermal decoupling of the hotend 3 to upstream plastic filament guide components takes place.

[0025] Upstream of the hotend 3 there is also a print head heat sink 12 (cf. Fig. 1 ) of the print head 1, which can be actively cooled by a fan.

[0026] The base body 6 of the hotend 3 also has a heating element 13 (cf. Fig. 2 ) for one in the Fig. 1 non-visible heating unit 13a (cf. Fig. 2 ) in the form of a heating cartridge. Furthermore, the base body 6 has a sensor receptacle 14 for a temperature sensor, of which Fig. 3 a signal cable section 15 is visible.

[0027] A channel course of the filament channels 6a, 6b between the inlets 4, 5 and the outlets 7a, 7b of the base body 6 is shown in the Fig. 5 The two filament channels 6a, 6b do not merge on the outlet side in the base body 6, but only further along in the print nozzle 8. Accordingly, there is no common channel for the filaments in the base body 6 of the hotend 3.

[0028] The base body 6 is made of a metal with a thermal conductivity coefficient of less than 100 W / (mK). This metal is a food-safe material in accordance with the specifications of EC Regulation 193 / 2004 and the manufacturing specifications of EC Regulation 2023 / 2006. The metal is a high-alloy steel, namely stainless steel. Stainless steel has a carbon content in the range between 0.5% and 5%, for example 2%. Stainless steel has a chromium content in the range between 10% and 25%, for example 17%. Stainless steel has a nickel content in the range between 10% and 15%, for example 12%. Stainless steel has a molybdenum content in the range between 1% and 5%, for example 2%. The stainless steel can be stainless steel with the material number 1.4404.

[0029] A wall thickness WS of the filament channels 6a, 6b between the respective inlets 4, 5 and the respective outlets 7a, 7b, apart from the direct inlet area, is at most 0.4 mm, for example 0.2 mm.

[0030] The filament channels 6a, 6b are thermally connected to heat sinks 18, 19 for heat dissipation from the interior of the filament channels 6a, 6b to the outside via inlet-side cooling channel sections 16, 17, which extend from the inlets 4, 5 to the heater receptacle 13. The heat sinks 18, 19 are each formed by a plurality of cooling fins 20. Each of the heat sinks 18, 19 has twenty cooling fins 20. Depending on the design of the heat sinks 18, 19, the number of cooling fins 20 can also vary, for example, in the range between two and one hundred.

[0031] As can be seen from the perspective view Fig. 2 As can be seen, at least some of the cooling fins 20 of the heat sinks 18, 19 are mechanically connected to one another. The heat sinks 18, 19 are designed and shaped such that cooling air is guided from the outside to the cooling channel sections 16, 17 of the filament channels 6a, 6b.

[0032] The heat sinks 18, 19 have fan connections through which cooling air can be supplied to the heat sinks 18, 19 from the outside, for example via corresponding air ducts emanating from the fan of the print head heat sink 12. In total, the hotend 3 has two fan connections 21, which can be connected, for example, in the Fig. 3 are visible.

[0033] Active cooling of the heat sinks 18, 19 can be ensured via the fan connectors 21.

[0034] The heat sinks 18, 19 each represent monolithic components of the base body 6.

[0035] Fig. 5shows a highlighted melting area 22 of the base body 6 of the hotend 3. In the channel sections of the filament channels 6a, 6b located in the melting area 22, molten printing material is present during operation of the hotend 3 by means of the heating unit in the heating holder 13. The two filament channels 6a, 6b have a total melting volume SV1 + SV2 in the sections located in the melting area 22 that is less than 100 mm 3 .

[0036] A distance between the melt volumes SV1, SV2 and a heating unit receiving volume of the heating holder 13 is at most 0.5 mm.

[0037] The melt volumes SV1 and SV2 are limited upstream of the filament channels 6a, 6b by areas in which these filament channels 6a, 6b are directly coupled to the heating element 13. Downstream, the melt volumes SV1, SV2 of the filament channels 6a, 6b are limited by the respective outlets toward the printing nozzle 8.

[0038] Between the respective inlet 4, 5 and the beginning of the melting region 22, the channel sections of the filament channels 6a, 6b have a constant cross-section. Within the melting region 22, i.e., in the respective melt volume SV1, SV2, the adjacent channel sections of the filament channels 6a, 6b taper continuously in cross-section.

[0039] In the inlet-side channel sections of the filament channels 6a, 6b, a channel diameter in the range between 1.80 mm and 2.0 mm can be present. The channel diameter can be, in particular, 1.85 mm. In the area of ​​the outlets 7a, 7b, a channel diameter in the range between 0.5 mm and 0.8 mm can be present. The channel diameter there can be, in particular, 0.7 mm.

[0040] Between the inlets 4, 5 and the outlets 7a, 7b, the filament channels 6a, 6b run without abrupt changes of direction and, in particular, have no 90° deflection.

[0041] The outlet channel sections, through which the outlets 7a, 7b open into the print nozzle 8, are arranged vertically in an operating position of the hotend 3.

[0042] The base body 6 of the hotend 3 is entirely manufactured using 3D printing.

[0043] The temperature sensor in the sensor holder 14 serves during operation to monitor a temperature of the printing material in the area of ​​a print nozzle holder 24 for the print nozzle 8.

[0044] When 3D printing with the 3D printer 2, the type of plastic filament to be loaded into the two inlets 4, 5 is first selected. The 3D printer is started up via a central control unit 25, and the heating unit, monitored by the temperature sensor, heats the melting area 22 until the plastic filament to be used is present as molten, viscous printing material in the melting volume SV1 or SV2. The 3D printer 2 is now ready for use, and the plastic component can be printed layer by layer, as usual, using an xyz relative displacement control between the nozzle head 1 and a carrier for the plastic component to be produced.

[0045] A corresponding filament feed can be used to control which filament channel 6a, 6b is used to feed the plastic filament to the print nozzle 8. Due to the very small total melt volume SV1 + SV2, only a small dead volume is available in the event that a material change actually occurs during the filament channel change, which may not be used for component construction.

[0046] The unused filament strand can be retracted due to the channel sections of the filament channels 6a, 6b with a constant cross-section in order to prevent unwanted melting.

[0047] A temperature difference between the pressure nozzle holder 24 of the base body 6 on the one hand and the end walls 9, 10 of the inlets 4, 5 can be in the range of 100° C.

Claims

1. Temperature control and transformation device (3) for a 3D printer (2), for transforming at least one plastic filament from a solid state into a melted viscous printing material, - having a printing nozzle (8) for dispensing the printing material, - having a base body (6), -- having at least one filament channel (6a, 6b) with an inlet (4, 5) for supplying the at least one plastic filament and with an outlet (7a, 7b) for dispensing the printing material to the printing nozzle (8), -- having a heating receptacle (13) for a heating unit (13a), wherein the heating receptacle (13) is adjacent to a melting volume (SV1 + SV2) of the filament channel (6a, 6b), in which printing material melted by means of the heating unit (13a) is present during operation of the device (3), - wherein the base body (6) is manufactured from a metal having a coefficient of thermal conduction of less than 100 W / (mK), - wherein the filament channel (6a, 6b) is in thermally conductive connection to at least one cooling body (18, 19) for heat dissipation via an inlet-side cooling channel section (16, 17) of the filament channel (6a, 6b), - wherein the cooling body is configured such that cooling air is guided towards the cooling channel section.

2. Device according to Claim 1, characterised in that the base body (6) is made from high-alloy steel.

3. Device according to Claim 1 or 2, characterised in that the filament channel has a wall thickness of no more than 0.4 mm between the inlet and the outlet.

4. Device according to one of Claims 1 to 3, characterised in that the cooling body comprises a plurality of cooling fins.

5. Device according to Claim 4, characterised in that the cooling body (18, 19) is actively cooled.

6. Device according to Claim 4 or 5, characterised in that the cooling body (18, 19) is a monolithic component of the base body (6).

7. Device according to one of Claims 1 to 6, characterised by a distance between the melting volume (SV1 + SV2) and a heating unit receiving volume of the heating receptacle (13), which is no more than 0.5 mm.

8. Device according to one of Claims 1 to 7, characterised in that the base body (6) is manufactured by 3D printing.

9. Device according to one of Claims 1 to 8, characterised in that the base body (6) has a sensor receptacle (14) for a temperature sensor.

10. 3D printer (2) having a device (3) according to one of Claims 1 to 9.