DE102017221658A1 - Method and apparatus for generatively producing a workpiece by melt stratification with structural reinforcement by embedding a tangled polymeric thread - Google Patents

Abstract

The invention relates to a method for the generative production of a workpiece (200) according to the melt-layer method, wherein the workpiece to be produced (200) is constructed in layers of plastic (K). According to the invention, during the construction of the workpiece (200), at least one entangled polymer thread (P) is embedded in the layers (210) which partially also penetrates into the respectively previously produced layer (210b) and thereby interconnects the layers (210).
The invention further relates to a device (100) suitable for carrying out this method.

Description

The invention relates to a method and a device for the additive production of a workpiece according to the melt layer method.

Generative or additive manufacturing of workpieces of all kinds is becoming increasingly important. A common method of generative production is the melt layer method or melt stratification (also referred to as FFF method or as Fused Filament Fabrication). In this method, the workpiece to be manufactured, quasi-original, is built up from a plastic, in particular a thermoplastic, computer-controlled (for example based on CAD data of the workpiece). The z. B. as a thread (filament) provided plastic is heated until it has reached a liquid or semi-liquid state, and discharged through at least one nozzle of a printhead. The production of the workpiece takes place in individual working planes, which are each traversed line by line with the print head, so that a layered or layered structure results. The deposited plastic cools, hardens and combines with the previously applied plastic.

In workpieces which are produced by means of such a 3D printing process, a pronounced anisotropy results. In other words, the manufactured workpiece has different mechanical properties depending on the direction. Within a layer, the strength and impact resistance are comparatively high. Perpendicular to the layers or layers, the strength and impact resistance are significantly lower, so that the workpiece fails under mechanical stress mostly at the interfaces between the layers or layers.

In the WO 2016/083797 A1 is a filled with sized glass flakes plastic for the printing of workpieces described. Angled glass flakes protruding over the surface of a first printed layer provide a rough surface so that a second printed layer applied to the first layer has better adhesion.

In the DE 10 2014 110 505 A1 It is proposed to use pulverulent solid particles as adhesion promoters, which are sprinkled on a previously applied polymer composition, which has left the extrusion die in particular immediately before.

In the US 2016/0012935 A1 is described a method for generative production of a three-dimensional object and a starting material usable therefor. The feedstock includes a fiber embedded in a matrix material having a central filament and outwardly projecting structures therefrom. To form the three-dimensional object, the starting material can be applied through an extrusion die. Thereafter, before the matrix material solidifies, the structures, which are initially folded, can expand radially outward, forming a framework which reinforces the matrix material and improves the surface area for deposition of the next layer.

The invention has for its object to provide a method and apparatus for the generative production or production of a workpiece according to the melt-layer method, which do not have at least one associated with the prior art disadvantage or at least only reduced.

The object is achieved by the claimed with the independent claims invention. Further developments and embodiments of the invention will become apparent for all subject matter of the dependent claims, the following description of the invention and the figures.

The inventive method provides that during the (layered) structure of the workpiece, ie when manufacturing the workpiece or even during the printing process, in the layers produced thereby, at least in some of the layers, at least one confused polymer thread is embedded, the sections also penetrates into the previously generated layer and thereby connects these layers or the respective layers together.

For the construction of the workpiece, a meltable thermoplastic material is preferably used. However, a thermoset (eg a synthetic resin) can also be used. The plastic may have reinforcing fibers, in particular short fibers and / or long fibers formed from common fiber materials.

The at least one tangled polymer thread is characterized by a random orientation (see below) and is over the interface between the layer currently being produced and the layer previously produced in sections (ie in sections with respect to the linear longitudinal extent of the thread) embedded both layers. On the one hand, the polymer thread or the polymer threads on the one hand cause a better cohesion of the layers over the boundary surfaces and, on the other hand, a reinforcement within the layers. By this structural reinforcement of the workpiece, an improvement in the strength perpendicular to the layers or layers is achieved and eliminates or at least reduces existing anisotropy. Furthermore, but also in other directions, the compressive strength, shear strength, bending strength and the like are improved. A polymer thread can be introduced anywhere in the workpiece or only in particularly stressed areas. It is also possible to use a plurality of differently formed polymer threads.

It is preferably provided that the polymer thread is confused only when embedding or immediately before by a thermal treatment or heat treatment. The following properties are used: The polymer thread used, in particular a thermoplastic polymer thread (see below), originally has a strong orientation of the molecular chains in the yarn longitudinal direction. If such a polymer thread is thermally treated or heat-treated, the orientation of the molecular chains is lost and the molecular chains change into a disordered state. The originally oriented, straight polymer thread confuses and transitions into a tangled or looped state with random orientation. The temperature chosen for the thermal treatment must be high enough so that the straight or stretched shape of the polymer thread is lost and the polymer thread is in a confused state, but on the other hand not be so high that the polymer thread dissolves and thereby the intended Gain effect is lost. In order to prevent this, the polymer thread can only be heated in sections during the thermal treatment only superficially (that is to say not continuously) and / or (for example by pulsed heating).

The polymer thread used is preferably formed from a thermoplastic material and is in particular a polyamide thread, z. As a nylon thread or an aramid thread. The polymer thread may have a diameter of a few microns to several tenths of a millimeter. The polymer thread is preferably endless, whereby pieces of thread which, for example, have a length of at least 20 mm and preferably at least 50 mm, can also be used.

It is preferably provided that a polymer thread formed from thermoplastic material is heated to a temperature above the melting temperature of its thermoplastic material, in particular to a temperature just above the melting temperature, for example to a temperature which is 5 K to 10 K above the melting temperature ,

Preferably, the plastic for the layered structure of the workpiece by (at least) a nozzle (Extrudierdüse) is applied, wherein the polymer thread can be discharged through the same nozzle. The polymer thread can be added or admixed in the print head (see below) to the heated or molten plastic (extrusion compound) for the workpiece structure. The thermal treatment of the polymer thread can then be carried out by the heated or molten plastic. The tangled polymeric filament is then laid down randomly within the currently generated or extruded topmost layer. The previously produced layer can be heated by means of a heating device arranged upstream of the nozzle and in particular melted, so that the tangled polymer thread (over the interface) can penetrate and be embedded in the previously produced or extruded layer in sections and thus finally in both (superimposed or mutually generated) layers is embedded and holds them together. The heating device can be operated with flame, hot air, hot gas, infrared or preferably laser.

The polymer thread can also be deposited separately on the layer previously produced by a depositing device located upstream of the nozzle and can then be embedded in the next layer produced or extruded with the subsequent nozzle. The previously produced layer and the polymer thread deposited thereon can be heated by means of a heating device (see above) arranged upstream of the nozzle, before the next layer is applied through the nozzle. The polymer thread is thermally treated and confused. Furthermore, the surface of the previously produced layer can also be melted, so that the polymer thread can partially penetrate into this (lower) layer when tangled and thus ultimately embedded in both layers and holds them together.

• - einen Druckkopf, mit dem das zu fertigende Werkstück schichtweise, d. h. Schicht für Schicht, aus Kunststoff aufgebaut werden kann; und
• - eine Einrichtung zur Zuführung (Zuführeinrichtung) wenigstens eines Polymerfadens, der während des Aufbaus des Werkstücks in die mit dem Druckkopf erzeugten Schichten eingebettet wird, wie vorausgehend erläutert, wobei diese Einrichtung bevorzugt eine Ablegeeinrichtung aufweist;
• - sowie optional eine Erwärmungseinrichtung für den Polymerfaden, die insbesondere für eine pulsierende bzw. abschnittsweise Erwärmung des Polymerfadens ausgelegt ist;
• - sowie optional eine Schneideinrichtung, mit der der Polymerfaden abgetrennt werden kann;
• - sowie optional eine Steuereinrichtung, die zumindest den Druckkopf, die Zuführeinrichtung für den Polymerfaden, die Erwärmungseinrichtung und/oder die Schneideinrichtung steuern kann, insbesondere verfahrensgemäß steuern kann.

The device according to the invention (3D printer) for the additive production of a workpiece according to the melt layer method comprises at least the following components:

• - A print head with which the workpiece to be produced in layers, ie layer by layer, can be made of plastic; and
• - means for feeding (feeding) at least one polymer thread which is embedded in the layers produced by the print head during the construction of the workpiece, as previously explained, this device preferably having a laying device;
• - And optionally a heating device for the polymer thread, which is designed in particular for a pulsating or sectionary heating of the polymer thread;
• - and optionally a cutting device with which the polymer thread can be separated;
• - And optionally a control device which can control at least the printhead, the feed device for the polymer yarn, the heating device and / or the cutting device, in particular according to the method can control.

The invention can be used in particular in the manufacture of a motor vehicle component. In particular, motor vehicle components produced according to the invention can also have a good crash performance.

• - an den Grenzflächen zwischen den Schichten werden die Steifigkeit, Festigkeit und Schlag- bzw. Bruchzähigkeit erhöht;
• - herstellungsbedingte Anisotropien werden beseitigt oder zumindest verringert, wodurch die mechanischen Werkstückeigenschaften verbessert werden und die Werkstück- bzw. Bauteilkonstruktion, insbesondere die Auslegung und Berechnung, vereinfacht wird - mitunter können sogar nahezu isotrope Werkstück- bzw. Bauteileigenschaften erzielt werden;
• - lokale lastpfadgerechte Verstärkung ist möglich, wodurch sowohl beanspruchungsgerechte Werkstück- bzw. Bauteilaufbauten ermöglicht werden als auch sehr hohe Leichtbaugrade erzielbar sind;
• - erweitertes Anwendungsspektrum für entsprechend hergestellte Bauteile, insbesondere im Automobilbau, vorzugsweise auch als Ersatz bzw. Surrogat für konventionell hergestellte Metallteile (bspw. Druckgussteile) und Kunststoffteile (bspw. Spritzgussteile).

The invention offers the following advantages (no exhaustive enumeration):

• at the interfaces between the layers, the rigidity, strength and impact strength are increased;
• - production-related anisotropies are eliminated or at least reduced, whereby the mechanical workpiece properties are improved and the workpiece or component construction, in particular the design and calculation, is simplified - sometimes even almost isotropic workpiece or component properties can be achieved;
• - Local load-path-oriented reinforcement is possible, whereby both stress-appropriate workpiece or component structures are made possible and very high levels of lightweight can be achieved;
• - Extended range of applications for appropriately manufactured components, especially in the automotive industry, preferably also as a substitute or surrogate for conventionally produced metal parts (eg., Diecasting) and plastic parts (eg injection molded parts).

• 1 veranschaulicht eine erste Ausführungsmöglichkeit des erfindungsgemäßen Verfahrens und zeigt eine entsprechende erste Vorrichtung.
• 2 veranschaulicht eine zweite Ausführungsmöglichkeit des erfindungsgemäßen Verfahrens und zeigt eine entsprechende zweite Vorrichtung.

The invention is explained in more detail below by way of example and not by way of limitation with reference to the schematic figures. The features shown in the figures and / or explained below may, even independently of specific combinations of features, be general features of the invention and further develop the invention accordingly. Furthermore, further embodiments of the invention can be formed from the features of the illustrated or explained embodiments of the invention.

• 1 illustrates a first embodiment of the method according to the invention and shows a corresponding first device.
• 2 illustrates a second embodiment of the method according to the invention and shows a corresponding second device.

1 shows a device 100 for the generative production of a workpiece 200 according to the melt-layer method. The device 100 has a printhead 120 on that via a nozzle (extruding nozzle) 125 molten plastic K ausbringt or extruded while the workpiece 200 layered or layered. The layer thickness of the generated layers 210 is, for example, in a range of 0.005 mm to ≥ 1.0 mm (greater than or equal to one point zero millimeters). To build up the workpiece 200 is in particular a meltable thermoplastic K (first plastic) used. Plastic K can be reinforcing fibers F respectively. The printhead 120 is a delivery system 130 for the plastic material K assigned. The printhead 120 is movable on a carrier or portal system 110 attached or stored.

The device 100 also has a feeder 140 for a polymer thread formed from plastic (second plastic), in particular thermoplastic material P on. The polymer thread P becomes during the construction of the workpiece 200 along with the plastic K through the nozzle 125 deployed (internal supply) and experiences by the heated or molten plastic K a thermal treatment that causes confusion of the polymer thread P leads. The tangled polymer thread P is section by section in the currently generated top layer 210a embedded and is partially in the previously generated lower layer 210b embedded so that the tangled polymer thread P the successively generated layers 210a . 210b connects with each other. This is very well recognizable in the detailed presentation. The polymer thread P is so confused by the thermal treatment that loops and turns arise, depending on the location in the upper layer 210a or in the lower, previously generated layer 210b be embedded. The device 100 also has a in the direction of travel R the nozzle 125 upstream heating device 150 on, with the previously generated layer 210b heated and melted so that the tangled polymer thread P easier to penetrate through the surface and be embedded. The heating device 150 is on the printhead 120 attached or forms with the printhead 120 a structural unit.

In the 2 embodiment shown differs from the in 1 embodiment shown essentially by that the feeder 140 is adapted to the polymer thread P separately through one of the nozzles 125 upstream depositing device 145 directly on the previously produced workpiece layer 210b store (external feed). The endless polymer thread P is from a semi-finished roll 141 deducted. The role 141 and the depositing device 145 are components of the feeder or of the delivery system 140 , With one of the nozzle 125 upstream heating device 150 can the previously generated layer 210b and the polymer thread deposited thereon P to be heated. The heating device 150 on the one hand has the task of the polymer thread P at least locally or in sections, even at changing preferred speeds, to bring the correct temperature (above the melting range), so that this confused and yet the reinforcing effect is maintained. The heating device 150 on the other hand has the task of the previously generated layer 210b melt so that the tangled polymer thread P can penetrate. The depositing device 145 and the heating device 150 are on the printhead 120 attached or form with the printhead 120 a structural unit.

LIST OF REFERENCE NUMBERS

100

device

110

Portal, carrier system

120

printhead

125

jet

130

Feeding system (for plastic)

140

Feeding device (for polymer thread)

141

role

145

laying device

150

heater

200

workpiece

210

Layer, location

F

reinforcing fibers

K

plastic

P

polymer thread

R

traversing

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

• WO 2016/083797 A1 [0004]
• DE 102014110505 A1 [0005]
• US 2016/0012935 A1 [0006]

Claims (10)

Method for the generative production of a workpiece (200) according to the melt-layer method, wherein the workpiece (200) to be produced is built up in layers of plastic (K), characterized in that during the construction of the workpiece (200) into the layers ( 210) at least one entangled polymer thread (P) is embedded, which also partially penetrates into the respectively previously produced layer (210b) and thereby connects the layers (210) to one another. Method according to Claim 1 , characterized in that the polymer thread (P) is confused only when embedding or immediately before by a thermal treatment. Method according to Claim 1 or 2 , characterized in that the polymer thread (P) is formed from a thermoplastic material and in particular is a polyamide thread. Method according to Claim 2 and 3 , characterized in that the polymer yarn (P) is heated in the thermal treatment to a temperature above the melting temperature of the thermoplastic material. Method according to one of the preceding Claims 1 to 4 , characterized in that the plastic (K) for the construction of the workpiece (200) by a nozzle (125) is applied and the polymer thread (P) through the same nozzle (125) is applied. Method according to Claim 5 , characterized in that the previously generated layer (210b) is heated by means of a heating device (150) located upstream of the nozzle (125). Method according to one of the preceding Claims 1 to 4 , characterized in that the plastic (K) for the construction of the workpiece (200) through a nozzle (125) is applied and the polymer thread (P) separately through a nozzle (125) upstream deposition device (145) on the previously produced layer (210b). Method according to Claim 7 , characterized in that the previously produced layer (210b) and the polymer thread (P) deposited thereon are heated by a heating device (150) upstream of the nozzle (125) before the next layer (210a) is applied through the nozzle (125) , Apparatus (100) for generatively producing a workpiece (200) by the melt-layer method, comprising: - A printhead (120), with which the workpiece to be manufactured (200) layer by layer of plastic (K) can be constructed; and - Means (140) for feeding at least one polymer thread (P), which during the construction of the workpiece (200) in the print head (120) generated layers (210) can be embedded. Device after Claim 9 , characterized in that the means (140) for feeding the polymer thread (P) has a printing device (145) upstream of the print head (120).

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