DE102017221687A1 - Method and device for the generative production of a workpiece by melt stratification with structural reinforcement by local punching and compaction of the layers - 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), punched cuts (S) are made, which have a closed punching contour and penetrate a plurality of layers (210) of the workpiece (200) and compact the punched slugs (B) produced thereby.
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 construction of the workpiece, ie when manufacturing the workpiece or even during the printing process, punch cuts are punched or punched into the workpiece, which have a closed punch contour and multiple (previously generated) layers of the already manufactured Penetrate workpiece, and that the resulting punched slugs are compacted.

When punching or punching a multiple layers penetrating incision with closed cutting line or punching contour is generated. Preferably, the die cuts penetrate at least two, particularly preferably at least three and in particular at least five layers. The number of punched layers can also be varied. The area enclosed by the cutting line or punching contour (= slug cross-sectional area) is preferably <1 cm ² , particularly preferably <0.5 cm ² and in particular <0.25 cm ² . The plastic material located within the cutting line or punching contour, which as it were consists of a plurality of superimposed layer pieces, is referred to as a punching slug. The compression or compression of the stamped casing reduces air pockets and improves the adhesion at the interfaces (between the layer pieces). In addition, an offset between the layer pieces and the surrounding layers is generated in the direction of layering. Furthermore, plastic flow processes over the layers or layer pieces occur along the cutting or stamping surfaces time. Optionally, reinforcing fibers contained in the plastic material can be shifted in such a way that they finally extend beyond the boundary surfaces and bridging occurs. As a result of the compression or compression of the stamped casing, a local stiffening or reinforcing effect is achieved which, in particular, also considerably improves the cohesion of the layers.

The reinforcing structures produced according to the invention at the corresponding locations or positions by local punching and compacting of the layers thus bring about a structural reinforcement of the workpiece without additional reinforcing elements, whereby an improvement in the strength perpendicular to the layers or layers is achieved by existing anisotropy eliminate or reduce. Furthermore, but also in other directions, the compressive strength, shear strength, flexural strength and the like are improved. Such reinforcing structures can be introduced anywhere in the workpiece or only in particularly stressed areas.

Preferably, the introduction or punching of the punched cuts and compressing the punched slugs thereby produced directly or immediately after the placement of the plastic by at least one nozzle, so that the top layer (or line) is not cured and thus in a still mouldable state the underlying layers or layer pieces is pressed.

At the corresponding points, the introduction of a stamped cut and the compacting of the stamping blank thus produced are preferably carried out in one operation, in particular by means of a tool which has a cutting or punching punch and a compacting or pressing punch guided in the interior of the punching punch. The punch has an annular cutting edge, d. H. a blade with ring-like closed cut line, on and works in the form of a cookie cutter (for cookies) or a Apfelentkerners. Preferably, the punch and the punch are moved separately, z. B. by individual drives, in particular provided that the punch is weggesteuert and the ram is force-controlled. The punch can be heated to facilitate penetration into the already cured layers. Optionally, the workpiece can also be heated at the relevant point, for example by means of hot air.

During the construction of the workpiece, the punched cuts are preferably placed offset one above the other. That is, the positions for the punch cuts are varied in the layered or layered structure of the workpiece and from layer to layer, for example, according to a predetermined pattern.

• - einen Druckkopf, mit dem das zu fertigende Werkstück schichtweise, d. h. Schicht für Schicht, aus Kunststoff aufgebaut werden kann; und
• - einen Werkzeugkopf mit (wenigstens) einem Werkzeug (Stanz-Press-Werkzeug), welches einen Stanzstempel mit ringartiger Schneide und einen im Inneren des Stanzstempels geführten Pressstempel aufweist, wobei mit dem Werkzeug während des Aufbaus bzw. beim Fertigen des Werkstücks (also noch während des Druckvorgangs) Stanzschnitte in das Werkstück eingebracht und die dabei erzeugten Stanzbutzen verdichtet werden können;
• - gegebenenfalls eine Heizeinrichtung für den Stanzstempel und/oder ein Heißluftgebläse (Heißluftfön) zur lokalen Erwärmung des Werkstücks;
• - sowie gegebenenfalls noch eine Steuereinrichtung, die den Druckkopf und den Werkzeugkopf 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
• - A tool head with (at least) a tool (punch-press tool), which has a punch with ring-like cutting edge and a guided inside the punch punch, wherein the tool during assembly or when manufacturing the workpiece (ie still during the printing process) punched cuts introduced into the workpiece and the resulting punching slugs can be compressed;
• - If necessary, a heater for the punch and / or a hot air blower (Heißluftfönse) for local heating of the workpiece;
• - And possibly also a control device that can control the printhead and the tool head, in particular according to the method can control.

The punch and / or the punch of the tool may have a lubricious and / or non-stick coating, in particular a Teflon coating or the like. As a result, on the one hand good guidance of the press ram in the punch can be achieved and, on the other hand, the adhesion of plastic can be prevented. The punch and / or the punch can be made of hardened steel or ceramic. For the print head and the tool head separate carrier systems or portal systems are preferably provided, on which the heads are mounted or stored, so that the print head and the tool head are autonomously moved or moved.

The invention can be used in particular in the manufacture of a motor vehicle component. The motor vehicle components produced according to the invention can in particular 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 Werkstückkonstruktion (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 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 design (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 correspondingly manufactured components, especially in the automotive industry, preferably also as a replacement for conventionally produced metal parts (eg., Diecasting) and plastic parts (eg injection molded parts).

• 1 veranschaulicht das erfindungsgemäße Verfahren und zeigt eine erfindungsgemäße Vorrichtung zur Ausführung des Verfahrens.
• 2 zeigt mögliche Stanzgeometrien, die mit einem zur Vorrichtung der 1 gehörenden Werkzeug erzeugbar sind.

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.

• 1 illustrates the method according to the invention and shows an apparatus according to the invention for carrying out the method.
• 2 shows possible punching geometries, the one with the device of 1 belonging tool can be generated.

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 emits (extruded) and thereby the workpiece 200 layered or layered. The layer thickness of the layers 210 is, for example, in a range of 0.005 mm to> 1.0 mm. To build up the workpiece 200 is in particular a thermoplastic K used. Plastic K may comprise reinforcing fibers, in particular short and / or long fibers formed from common fiber materials. The printhead 120 is a delivery system 130 assigned to the plastic material. The device 100 also has a tool head 150 on, in the direction of travel R the printhead 120 is downstream and in particular in the immediate vicinity of the print head 120 is arranged. The printhead 120 is movable on a first portal system 110 and the tool head 150 is movable on a separate second portal system 140 attached.

With the tool head 150 be during the ongoing production of the workpiece 200 consecutively several layers 210 cutting through cuts S into the workpiece 200 introduced, in particular before the topmost, immediately before deposited layer (or line or web) 210 is cured, and the case generated punching B compressed or compressed. This is very well recognizable in the detailed presentation. The tool head 150 is this with at least one tool 151 equipped with a punch 152 with ring-like cutting edge and one inside the punching punch 152 guided punch 153 having. The punch 152 and the press stamp 153 can be moved separately, including single drives 154 . 155 into the tool head 150 are installed.

The punch 152 is driven away at the intended locations in a defined (lower) end position and stopped. The punching or introduction of the die cuts S done without counter die. Then the press stamp 153 force-controlled (downwards) moves and compresses or compresses the stamped joint B which is almost inside the punch 152 located. Subsequently, the press stamp 153 and the punch 152 individually or jointly moved back (up). The punch 152 can be heated. The tool head 150 Furthermore, a device, such as. A hot air blower, for local heating of the workpiece 200 at the punching station.

The punch 152 of the tool 151 has an annular cutting edge or punching edge, which generates a closed cutting or punching contour. 2 shows in axial plan view possible cutting or punching geometries. In the illustration on the top left is also the form-adapted, inside the punch 152 guided press punches 153 shown.

LIST OF REFERENCE NUMBERS

100

device

110

Portal, carrier system

120

printhead

125

jet

130

feed

140

Portal, carrier system

150

tool head

151

Tool

152

punch

153

press die

154

drive

155

drive

200

workpiece

210

Layer, location

B

slug

K

plastic

R

traversing

S

chad

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 manufactured is constructed in layers of plastic (K), characterized in that during the construction of the workpiece (200) punched cuts (S) are introduced , which have a closed punching contour and penetrate a plurality of layers (210) of the workpiece (200), and the resulting punched slugs (B) are compacted. Method according to Claim 1 , characterized in that the introduction of a punched cut (S) and the compacting of the stamping (B) produced thereby takes place in one operation, by means of a tool (151), which a punch (152) and a guided inside the punch (152) Compression stamp (153). Method according to Claim 2 , characterized in that the punch (152) and the press ram (153) are moved separately, the punch (152) being controlled away and the press ram (153) is force-controlled. Method according to Claim 2 or 3 , characterized in that the punch (152) is heated. Method according to one of the preceding claims, characterized in that the punched cuts (S) penetrate at least two, preferably at least three and in particular at least five layers (210). Method according to one of the preceding claims, characterized in that the positions for the punched cuts (S) from layer (210) to layer (210) are varied. 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 - A tool head (150) with a tool (151), which has a punch (152) with ring-like blade and a punch inside the punch (152) guided punch (153), whereby during the construction of the workpiece (200) punched cuts (S ) can be introduced into the workpiece (200) and the punched slugs (B) produced thereby can be compacted. Device (100) according to Claim 7 , characterized in that the punch (152) and / or the punch (153) have a sliding and non-stick coating. Device (100) according to Claim 7 or 8th , characterized in that the punch (152) is formed of hardened steel or ceramic. Device (100) according to one of Claims 7 to 9 , characterized in that separate portal systems (110, 140) are provided for the print head (120) and the tool head (150).

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