DE102017207737A1 - Apparatus and method for 3D printing a workpiece of a rubbery non-thermoplastic material - Google Patents

Abstract

Apparatus and method for 3D printing a workpiece of a rubbery non-thermoplastic material, comprising an extruder 1 having a component supply port 2 and a nozzle 3, an actuator 4 communicating with the extruder 1, and a control unit 5 for Controlling the extruder 1 and the actuator 4 such that a plurality of material layers 6, 7 are applied for forming a workpiece 8 to be printed.

Description

The present invention describes an apparatus and method for 3D printing a workpiece from a rubbery non-thermoplastic material, whereby a highly reproducible printing process and a high quality printed material can be obtained.

From the DE 10 2015 103 377 A1 For example, a printhead and extruder die for 3D printing is known, wherein a printhead for use in an extruder is used to make three-dimensional workpieces with a 3D printing process. In this method, the workpiece is built by applying a material, this material is solid at room temperature, is liquefied before application and solidifies again after cooling by cooling. It is thus the material is a thermoplastic material.

However, such materials have the disadvantage that they are not temperature resistant and also change the material properties with changing temperature also. This is true, for example, for the viscosity, which decreases significantly above the melting point.

As a result, it can not be guaranteed that the material properties will remain constant over a wide temperature range with changing environmental conditions.

It is an object of the invention to provide an apparatus and a method for 3D printing a workpiece from a rubbery non-thermoplastic material which realize a highly producible printing operation of a high quality printed material. In particular, the printed material should have substantially constant material properties over a predetermined temperature range.

The object is solved according to the features of the independent claims. The dependent claims relate to advantageous embodiments and further developments of the invention.

The apparatus for 3D printing a workpiece of a rubbery non-thermoplastic material according to the present invention may include an extruder having a material supply port and a nozzle. Furthermore, the device may include an actuator that communicates with the extruder. In addition, the apparatus may include a control unit for controlling the extruder and the actuator such that multiple layers of material may be applied to form a workpiece to be printed.

The extruder can be operated with different nozzles, wherein, for example, an automatic nozzle changer can be provided, so that depending on the print task different nozzles with different shapes and opening cross sections can be automatically selected.

The components used for printing can be fed to the extruder separately via material supply ports, which are then mixed in the extruder. When mixing with, for example, a screw, a shear energy is supplied to the components, which can lead to heating of the components, which then can promote the further vulcanization process.

After the application of material to an already applied material layer occurs due to the material properties and the temperature of the already applied material layer to a self-vulcanization, with a high-quality printed workpiece with highly reproducible material properties can be obtained.

A radiant heater may be provided on the extruder, which may be movable with the extruder and may be controlled via the control unit. As a result, the already printed material layer can be heated to promote self-vulcanization when applying the new material layer. The radiant heating can also be arranged in a different component than the extruder, but it should be ensured that the slowest possible, gentle, extensive and deep heating of the already applied material layer is ensured immediately before the application of the next layer of material.

Further, the extruder may have an internal temperature sensor for measuring the temperature of the rubbery material. The internal temperature sensor may be arranged such that the temperature of the rubbery material flowing to and / or out of the nozzle can be measured. Furthermore, an outside temperature sensor can be provided which detects the temperature of a material layer already applied and heated by the radiant heater, and the control unit can control the heating device such that a setpoint temperature Tset of the already applied material layer is reached immediately before the application of the next material layer. Furthermore, a heater in the Extruder be provided to bring the exiting material to a predetermined temperature.

By, for example, the aforementioned measures, the material emerging from the nozzle in its properties can be optimally brought to the required temperature to enter with the also optimally preheated already applied material after applying a self-vulcanization such that a high-quality workpiece can be achieved. The crosslinking of the different material layers takes place chemically by vulcanization. In such a treatment or the degradation of rubber, for example, a splitting of the long rubber molecules takes place in order to reduce the hardness of the rubber or make it more easily deformable. It is therefore advantageous to machine the rubber mechanically, for example, by means of the screw present in the extruder and to treat it chemically by means of appropriate decomposition means.

The temperature of the components involved is usually at room temperature, wherein the components are heated in the extruder by the shear energy, for example by the screw (as mentioned above).

The material properties of the components and the mixing process are adjusted such that the material emerging from the nozzle has a predetermined viscosity. This viscosity may be between 20 and 70 ME (ML1 + 4 @ 100 ° C), preferably between 30 and 40 ME (ME = Mooney unit).

The rubbery material may be a non-thermoplastic elastomer formed such that its viscosity substantially does not change in a temperature range of from 19 ° C (room temperature) to 120 ° C. This can be obtained a printed workpiece, which is very high quality.

The temperature of the already applied material layer can be brought to 30 to 60 ° C, preferably to 40 to 60 ° C by radiation heating immediately before applying the next layer of material. Furthermore, the material emerging from the nozzle may have a temperature of 60 to 80 ° C.

By the aforementioned temperatures, the beginning of an optimal self-vulcanization of the material in a sufficiently short time interval of, for example, 2 to 3 minutes can be achieved. As a result, it is possible to apply the next material layers relatively quickly without fear of flow or escape of the newly applied or already applied material. Care is taken to ensure that the viscosity of the mixture is also adjusted so that it does not flow or flow away during curing or during self-vulcanization. This also filigree shapes can be formed with appropriate overhangs.

The first component can be 0-100 phr (0-100 phr) natural rubber, 0-100 phr styrene butadiene rubber, 0-50 phr butadiene rubber, 0-2 phr masticating agent, 0-30 phr process additive, 0-40 phr active filler. 50 phr, 0-50 phr inactive filler, 0-20 phr plasticizer, 0-2 phr processing aid, 0-5 phr aging inhibitor, 0-8 phr metal oxides, and / or 0.1-5 phr crosslinking reagent ,

Preferably, the first component may contain natural rubber at 50-100 phr. Preferably, the first component may contain styrene butadiene rubber with 0-30 phr. Preferably, the first component may contain butadiene rubber with 0-30 phr. Preferably, the first component may contain process additive at 5-30 phr. Preferably, the first component may contain active filler with 0-20 phr.

The second component can be natural rubber with 0-100 phr, styrene butadiene rubber with 0-100 phr, butadiene rubber with 0-50 phr, masticating agent with 0-2 phr, process additive with 0-30 phr, active filler with 0-50 phr, inactive filler with 0-60 phr, 0-20 phr plasticizer, 0-2 phr processing aid, 0-5 phr aging inhibitor, 0-8 phr metal oxides, and / or 0.1-5 phr accelerator.

Preferably, the second component may contain natural rubber at 50-100 phr. Preferably, the second component may contain styrene butadiene rubber with 0-30 phr. Preferably, the second component may contain butadiene rubber with 0-30 phr. Preferably, the second component may contain process additive at 5-30 phr. active filler containing 0-20 phr. Preferably, the second component may contain inactive filler at 20-60 phr.

By the aforementioned selection of components, the aforementioned positive properties of the workpiece can be achieved. In particular, this makes it possible to achieve an optimum viscosity adapted to the workpiece, optimized processing times can be achieved and the desired self-vulcanization, which proceeds in a short time and is of high quality, can be achieved in an optimum manner.

Possible and preferred physical properties of the workpiece, for example, a density in g / cm ³ from 0.9 to 1.4, a Tear strength S2 rod in N / mm ² from 9 to 24, an elongation at break S2 rod in% from 200 to 700, a hardness in Shore A of 35 to 85, an abrasion in mm ³ from 50 to 350 and / or a resilience in% of 20 to 60 be.

The aforementioned preferred physical properties can be achieved by the starting components (the first and second components), the corresponding mixing operation and / or the printing application process. In this case, in particular, the respective temperatures, as mentioned above, may be of importance.

The control unit may be arranged to control the extruder such that the material exits at a predetermined mass flow of 1 to 2 kg / h for a fine nozzle and 10 to 20 kg / h for a coarse nozzle. A fine nozzle can be specified by having its cross section in the range of 1-5 mm. A coarse nozzle can be specified by having a cross section in the range of 10-20 mm.

Furthermore, a method of 3D printing a workpiece from a rubbery non-thermoplastic material using the aforementioned apparatus can be realized in the present invention.

As already mentioned above, it is possible to separate the printing material into two components before printing, or to store them separately. In the first component, for example, sulfur is provided as crosslinker, and in the second component an accelerator. Separately, both components can be stored for an extremely long time. However, should it be necessary to mix all of the recipe ingredients (the first and second components), then shelf life would be one to two days, for example.

Since the start of the vulcanization of the two components begins as soon as the components are mixed, it is of great importance for the quality of the workpiece that the aforementioned boundary conditions are met. The vulcanization or the chemical reaction of the two components and also the already applied material layers and the newly applied material layer can be done for example at room temperature or only at a slightly elevated temperature. As mentioned above, the temperature of the contact surface between the already applied material and the newly newly applied material will preferably be in a range between 30 to 80 ° C. This temperature range can result from the fact that the temperature of the already applied material layer, for example, at 30 to 60 ° C, preferably at 40 to 60 ° C, is or is brought, and the temperature of the material emerging from the nozzle a Tsoll of example 60th to 80 ° C has.

The components or component components used are optimally selected and adjusted such that an optimized self-vulcanization can take place at the abovementioned temperatures.

In particular, it is not necessary to work with greatly elevated temperatures, namely, as usual, with temperatures above 100 ° C.

figure

The figure shows an example of a device according to the invention in a schematic representation.

An extruder 1 has a component supply port 2 on. The component supply port may be a port for a first component 13 and a connector for a second component 14 exhibit. These two components 13 . 14 can in the extruder 1 be mixed over a screw, not shown, or it will be two components 13 . 14 supplied with a corresponding shear energy.

To detect a temperature within the extruder, an internal temperature sensor 10 be provided. This indoor temperature sensor 10 may be arranged such that the temperature of the rubber-like material flowing to the nozzle and / or emerging from the nozzle is measured. The position of the internal temperature sensor shown in the figure can also be chosen differently, for example in the flow direction just before a nozzle 3 or possibly even on or in the nozzle 3 ,

Furthermore, a heating device 12 be provided, which is also shown only schematically. This heater 12 For example, it may be provided on an inner wall of the extruder. But it is also possible to heat the screw, not shown, in which case the heater 12 would be provided on or in the screw.

In conjunction with the extruder 1 standing, can radiant heating 9 be provided, which is provided such that, for example, an IR (infrared) radiation in the direction of an already applied material layer 6 is aligned. By this radiant heating, the already applied material layer 6 just before applying one next material layer 7 be brought to the appropriate temperature to achieve the desired chemical reaction (self-vulcanization). As a result, the workpiece to be printed can have the desired high quality.

To check the preheating temperature of the already applied material layer 6 can be an outside temperature sensor 11 be provided, for example, via a laser measuring the temperature of the already applied material layer 6 can capture. About a control unit 5 can then by means of the detected temperature by the outside temperature sensor 11 the radiant heating 9 be controlled such that the desired temperature of the already applied material layer 6 just before applying the next layer of material 7 is set.

The control unit 5 can also have an actuator 4 such that the extruder at the desired speed in the feed direction (in the figure, for example, to the left) is moved. Furthermore, the control unit may be the actuator 4 such that a three and / or four and / or five-fold movement of the extruder 1 is performed. Furthermore, the control unit 5 To control a nozzle changer (not shown), which during the 3D printing different nozzles 3 for example, from a nozzle magazine (not shown) to the extruder or to an outlet opening (not shown) of the extruder 1 to meet different requirements for 3D printing.

The control unit 5 can the mixing process and / or the material application via the screw, not shown, the movement of the actuator 4 , the heater 12 , the radiant heating 9 and / or adjust the speed of the extruder screw (not shown) such that a workpiece 8th has the required properties (as mentioned above).

In summary, with the device according to the invention, the method according to the invention and the special rubber mixtures, a 3D printing can be carried out which particularly advantageously permits low-temperature self-vulcanization of the applied material layers. Furthermore, by using a non-thermoplastic rubber-like material, a very high workpiece quality can be achieved, the material properties of which remain constant over a wide temperature range.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102015103377 A1 [0002]

Claims (20)

Device for 3D printing a workpiece made of a rubber-like non-thermoplastic material, with an extruder (1) having a component supply port (2) and a nozzle (3), an actuator (4) associated with the extruder (1), a control unit (5) for controlling the extruder (1) and the actuator (4) such that a plurality of material layers (6, 7) are applied for forming a workpiece (8) to be printed. Device after Claim 1 , wherein a radiant heater (9) is provided, which is movable with the extruder (1) and is controlled by the control unit. Device after Claim 1 or 2 wherein the extruder (1) comprises an internal temperature sensor (10) for measuring the temperature of the rubbery material. Device according to at least one of Claims 1 - 3 wherein the internal temperature sensor (10) is arranged such that the temperature of the rubbery material flowing to the nozzle (3) and / or exiting from the nozzle (3) is measured. Device according to at least one of Claims 1 - 4 , wherein an outside temperature sensor (11) is provided which detects the temperature of an already applied and by the radiant heater (9) heated material layer (6) and the control unit (5) controls the heater (9) such that a target temperature Tset of already applied Material layer (6) is achieved. Device according to at least one of Claims 1 - 5 wherein the control unit (5) controls the extruder (1) such that the material emerging from the nozzle (3) has a predetermined viscosity. Device according to at least one of Claims 1 - 6 wherein the control unit (5) via a rotational speed of the extruder screw of the extruder (1) controls a shear energy introduced into the material such that the material emerging from the nozzle (3) has a predetermined viscosity. Device according to at least one of Claims 1 - 7 , wherein the extruder (1) has a heating device (12) which is controllable via the control unit (5) and brings the material emerging from the nozzle (3) to a predetermined temperature. Device according to at least one of Claims 1 - 8th , wherein the viscosity of the material emerging from the nozzle (3) is between 20 and 70 ME (ML1 + 4 @ 100 ° C), preferably between 30 and 40 ME (ME = Mooney unit). Device according to at least one of Claims 1 - 9 wherein the rubbery material is an elastomer (non-thermoplastic) and is formed such that its viscosity substantially does not change in a temperature range of from 19 ° C (room temperature) to 120 ° C. Device according to at least one of Claims 1 - 10 , wherein the temperature of the already applied material layer (6) by the radiant heater (9) immediately before the application of the next layer of material (7) to 30-60 ° C, preferably brought to 40-60 ° C. Device according to at least one of Claims 1 - 11 , wherein the temperature of the material emerging from the nozzle (3) has a Tset of 60-80 ° C. Device according to at least one of Claims 1 - 12 wherein the material consists of two components, which are supplied via the material supply port (2), wherein the components are mixed before the feeding or only after the feeding in the extruder (1). Device according to at least one of Claims 1 - 13 wherein a first component (13) comprises 0-100 phr (0-100 phr) natural rubber, 0-100 phr styrene butadiene rubber, 0-50 phr butadiene rubber, 0-2 phr masticating agent, 0-30 phr process additive 0-50 phr filler, 0-50 phr inactive filler, 0-20 phr plasticizer, 0-2 phr processing aid, 0-5 phr aging inhibitor, 0-8 phr metal oxides, and / or 0.1 crosslinking reagent Contains -5 phr. Device after Claim 14 wherein the first component (13) preferably contains natural rubber with 50-100 phr, styrene butadiene rubber with 0-30 phr, butadiene rubber with 0-30 phr, process additive with 5-30 phr and / or active filler with 0-20 phr. Device according to at least one of Claims 1 - 15 wherein a second component (14) is 0-100 phr natural rubber, 0-100 phr styrene butadiene rubber, 0-50 phr butadiene rubber, 0-2 phr masticating agent, 0-30 phr process additive, 0-50 phr active filler 0-50 phr inactive filler, 0-20 phr plasticizer, 0-2 phr processing aid, 0-5 phr aging inhibitor, 0-8 phr metal oxides, and / or 0.1-5 phr accelerator. Device after Claim 16 , wherein the second component (14) preferably natural rubber with 50-100 phr, styrene butadiene rubber with 0-30 phr, butadiene rubber with 0-30 phr, process additive with 5-30 phr, active filler with 0-20 phr, and / or inactive filler with 20-60 phr. Device according to at least one of Claims 1 - 17 in that the control unit (5) controls the extruder (1), the extruder screw, the radiant heater (9), the heating device (12) and / or the actuator (4) in such a way that the workpiece (8) has a density of 0.9 -1.4 g / cm ³ , a tensile strength - S2 rod of 9-24N / mm ² , an elongation at break of 200-700%, a hardness of 35-85Shore A, an abrasion of 50-350mm ³ and / or a back-parallel elasticity of 20-60%. Device according to at least one of Claims 1 - 18 in which the control unit (5) controls the extruder (1) such that the material has a predetermined mass flow of 1-2 kg / h for a fine nozzle (3) and 10-20 kg / h for a coarse nozzle (3). exit, wherein the cross section of the fine nozzle (3) in the range of 1-5 mm and the large nozzle (3) in the range of 10-20 mm. A method of 3D printing a workpiece of a rubbery, non-thermoplastic material using a device according to at least one of Claims 1 - 19 ,

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