EP-4739486-A1 - 3D PRINTER

EP4739486A1EP 4739486 A1EP4739486 A1EP 4739486A1EP-4739486-A1

Abstract

The invention specifies a 3D printer (1), which has a print head (6) for extruding a transparent ink strand (8), and has a transparent printing plate (10) for depositing the extruded ink strand (8). The 3D printer (1) also has an imaging apparatus (20), which provides a pattern formed at least from straight strips (22), and an optical recording device (14), which is designed to record an image (30) of the pattern and also of the deposited ink strand (8) during the designated printing operation by the 3D printer (1) from a bottom side (18) of the printing plate (10). The 3D printer (1) also has a controller (12), which is designed to derive at least one variable, which is characteristic of the printing operation, from the image (30) recorded by means of the recording device (14).

Inventors

GROLL, Jürgen
LAMBERGER, Zan
LANG, Gregor
Schrüfer, Stefan
SCHUBERT, DIRK WOLFRAM

Assignees

Friedrich-Alexander-Universität Erlangen-Nürnberg, in Vertretung des Freistaates Bayern
Julius-Maximilians-Universität Würzburg, in Vertretung des Freistaates Bayern

Dates

Publication Date: 20260513
Application Date: 20240712

Claims (11)

1. 3D printing device (1 ), comprising - a print head (6) for extruding a transparent ink strand (8), - a transparent printing plate (10) for depositing the extruded ink strand (8), - an imaging device (20) providing a pattern formed at least from rectilinear stripes (22), - an optical detection device (14) which is designed to detect an image (30) of the pattern and of the deposited ink strand (8) from an underside (18) of the printing plate (10) during the intended printing operation of the 3D printing device (1), and - a control device (12) which is designed to derive at least one variable characteristic of the printing operation from the image (30) captured by means of the capture device (14).
2. 3D printing device (1) according to claim 1, wherein the imaging device (20) is formed by a plate (24) printed with the pattern.
3. 3D printing device (1) according to claim 1, wherein the imaging device (20) is formed by a screen on which the pattern is displayed.
4. 3D printing device (1) according to one of claims 1 to 3, wherein the control device (12) is configured to infer a width, a curvature and/or a height of the deposited ink strand (8) based on an optical distortion of the pattern in the image (30).
5. 3D printing device (1) according to one of claims 1 to 4, wherein the stripes (22) of the pattern are set at an angle of at least approximately 45° to a main printing direction (32).
6. 3D printing device (1) according to claim 4 or 5, wherein the control device (12) is configured to infer a throughput and/or a printing speed as a characteristic variable from the width and the curvature and/or the height of the deposited ink strand (8).
7. 3D printing device (1) according to claim 5 or 6, wherein the control device (12) is configured to infer a spreading behavior of an ink used for the ink strand (8) based on a temporal progression of the width, the curvature and/or the height of the deposited ink strand (8).
8. 3D printing device (1) according to one of claims 1 to 7, wherein the control device (12) is configured to detect, in a calibration mode, a plurality of calibration strands (34) which are arranged on the printing plate (10) or a carrier to be placed thereon and which have a known cross-sectional geometry, and to use them to compensate for measurement deviations.
9. 3D printing device (1) according to claim 8, wherein the calibration strands (34) are formed from a material with a comparable refractive index and/or comparable viscosity as the ink.
10. 3D printing device (1) according to one of claims 1 to 9, comprising a radar sensor which is designed to detect at least locally the width, curvature and/or height of the deposited ink strand (8) during the intended printing operation of the 3D printing device (1) and to supply it to the control device (12) as a characteristic variable for determining the throughput and/or the printing speed.
11. Method for operating a 3D printing device (1), wherein according to the method - a transparent ink strand (8) is extruded by means of a print head (6) of the 3D printing device (1) and deposited on a transparent printing plate (10), - an imaging device (20) providing a pattern formed at least from rectilinear stripes (22) is provided, - an image (30) of the pattern and of the deposited ink strand (8) is captured from an underside (18) of the printing plate (10), and - at least one value characteristic of the printing operation is derived from the captured image (30).

Description

Description 3D printing device The invention relates to a 3D printing device. 3D printing devices were originally used for prototype production, or at best for small series production. The primary aim was to avoid costly processes such as injection molding, as these require costly injection molding tools. The simplest form of such "rapid prototyping" processes is so-called "Fused Deposition Modeling" (FDM), in which thermoplastic material is usually melted and deposited in strands in strips and layers using an extruder nozzle on a usually heated plate, usually in a heated room. With suitable process control, a three-dimensional construct with a resolution in the sub-millimeter range can be produced by fusing the strands together. The coordinates are usually provided to the 3D printing device on the basis of CAD models, which are converted into layered paths, the so-called G-codes, using so-called slicer software. Since the development of this "bottom-up" concept, numerous other 3D printing processes have been developed. Other classes of materials are also used here, such as photo-crosslinkable resins, which are then solidified into a component using stereolithography. The use of such manufacturing methods is also increasingly being sought for the production of larger series than small series, but also for individual components. Due to the gradual progress in manufacturing, these manufacturing methods are also summarized under the term "additive manufacturing". In the field of regenerative medicine, intensive research is also being carried out into the adaptation of additive manufacturing processes in order to be able to artificially produce tissue or even organs. In so-called biofabrication, living cells are printed together with biocompatible materials to form three-dimensional constructs with defined pore sizes. In order to enable cell survival and the maturation of a tissue, hydrogel-forming materials are used in particular, which are primarily intended to imitate the natural extracellular matrix of native tissue. For example, biomaterials based on collagen, gelatin, fibrin, hyaluronic acid, alginate and silk proteins or synthetic polymers such as PEGDA or POx and various blends and chemically modified variants thereof are used. The FDM process is often used in biofabrication because, in contrast to the inkjet process, for example, which is also used for printing cells, a wider range of materials can be processed and 3D constructs can be produced in a relatively short time. In order to process the materials, however, they must first be brought into a liquid, malleable state - e.g. melt, hydrogel or precursor solution - in order to then retain a defined 3D shape after a phase transition. The flow properties (or rheological properties) of the materials to be processed are of significant importance, both in processing and in the shape retention of the product. The main characteristic is usually the so-called viscosity. This describes the relationship between shear stress and shear rate. The shear stress is the stress that must be applied to deform a liquid at a certain shear velocity or shear rate. "Low viscosity" therefore means that low stresses must be used to deform a fluid. These are then thin fluids, whereas an increasing viscosity (i.e. increasing to higher values) ("high viscosity") describes an increase in "thickness" or "thickness". If there is a linear relationship between shear stress and shear rate, the viscosity is independent of the shear rate and is therefore constant - this is referred to as Newtonian flow behavior, which applies to water and many oils, for example. More complex systems, such as plastic melts, high molecular weight and concentrated solutions or multiphase systems such as suspensions, on the other hand, often do not exhibit Newtonian behavior, since their viscosity is often dependent on the shear rate or other factors such as time-dependent structural changes in the material. Polymer melts and highly concentrated solutions usually exhibit shear-thinning behavior, i.e. their viscosity decreases with increasing shear rate. Physical hydrogels can be destabilized under high shear stress and converted into a liquid state of aggregation, which allows them to be processed in an extrusion printing process. Such hydrogels or their precursors (i.e. aqueous solutions) that are loaded with cells and can be converted into a gel immediately after printing (by self-assembly or targeted cross-linking using ions or irradiation, for example) are referred to below as "bioinks". The printing resolution depends on the dimensional stability of the deposited strand, which should ideally spread as little as possible, i.e. flow apart. How far (or strongly) the strand can spread depends on the relationship between (temporal) throughput, viscosity and the speed of gelation. The difficulty in process optimization in the bioprinting process therefore lies in systematically recording the interplay of t