THREE-DIMENSIONAL PRINTING DEVICE FOR A SMALL GLASS OBJECT

Abstract

The invention proposes a device for three-dimensional printing of a glass object, by applying and solidifying successive layers of a material constituting the glass, in locations corresponding to the section of the object to be produced in the corresponding layer, by means of a laser producing a beam whose wavelength allows the direct fusion in the core of the material.

The device comprises: means for supplying the material to a support on which the successive layers are formed; means for thermal regulation of the successive layers for holding their temperature during the production of the object and for cooling them after the production of the object; a central unit controlling the laser.

The printing device comprises means for servo-controlling the power and the speed of the laser in real time.

Claims

1. A device for three-dimensional printing of an object made of glass, by applying and solidifying successive layers of a material constituting the glass, in locations corresponding to the section of the object to be produced in the corresponding layer, by means of a laser, said device comprising: means for supplying the material to a support on which the successive layers are formed; means for thermal regulation of the successive layers for holding their temperature during the production of the object and for cooling them after the production of the object; a central unit controlling the laser; said laser producing a beam whose wavelength allows the direct fusion of the material in its core, said printing device being characterized in that it comprises means for servo-controlling the power and speed of the laser in real time.

2. The printing device according to claim 1, characterized in that said thermal regulation means are controlled by the central unit and hold the layers of the object at a holding temperature comprised between the glass transition temperature of the material (Tg) minus 100° C. and the softening temperature of the material (Tr).

3. The printing device according to claim 1, characterized in that said thermal regulation means comprise a heating system of the support heating the first layer, each layer n being heated by contact with the lower layer n-1.

4. The printing device according to claim 1, characterized in that said thermal regulation means comprise a system for heating the ambient air around the object.

5. The printing device according to claim 4, characterized in that the servo-control means comprise a brightness sensing and measuring device sensing and measuring the light produced in the vicinity of the fusion point and transmitting information to the central unit.

6. The printing device according to claim 1, characterized in that the beam of the laser reaches said locations corresponding to the section of the object to be produced in the corresponding layer, by means of a set of orientable mirror or orientable mirrors controlled by the central unit and deflecting the outgoing rays of the laser in the direction of the location to be aimed at.

7. The printing device according to claim 1, characterized in that the means for supplying the material consist of a distributor of glass powder adapted to pour a dose of matter onto the entire surface forming the support in the initial phase and then onto each fused layer.

8. The printing device according to claim 1, characterized in that the support is mobile in vertical translation with respect to a horizontal work table of the device, said support being situated at the same level as the work table when the first layer of material is applied, then descends by one notch after each layer formation, the height of one notch corresponding to the thickness of the layer formed so that the next application of material is performed on a work surface located at the same level as the work table.

9. The printing device according to claim 1, characterized in that the object has a spatial resolution of less than one millimeter.

10. The printing device according to claim 1, characterized in that the laser beam is of the type of laser whose wavelength is chosen in the infrared or the UV range so that the beam is absorbed all along its path in the part.

11. The printing device according to claim 10, characterized in that the laser is of the CO laser type whose wavelength is between 1 and 12 μm.

12. A printing method for printing a glass object in three dimensions by means of a printing device as described in claim 1, characterized in that it comprises the following steps: a) checking the position of the support which must be at the same level as that of a work table; b) heating the support to the holding temperature; c) applying a first layer of material to the support; d) fusing the first layer of the material by the laser under supervision of servo-control means of the laser; e) descending the support by one notch; f) applying an additional layer of material over the previous layer; g) fusing the additional layer of the material by the laser under supervision of the servo-control means of the laser; h) descending the support by one notch; i) repeating the steps f) to h) until the object is completed; j) cooling the object according to a material-specific diagram.

Description

BRIEF DESCRIPTION OF FIGURES

[0093] Further characteristics and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference is made to the single attached drawing in which:

[0094] FIG. 1 is a schematic view of a device for three-dimensional printing of a glass object according to the invention;

[0095] FIG. 2 shows the laser fusion of glass powder;

[0096] FIG. 3 is a diagram of the brightness control system.

DETAILED DESCRIPTION OF THE INVENTION

[0097] The printing device as illustrated in FIG. 1 comprises a container 1 open at the top and comprising a vertically movable support 2. This support 2 is intended to support the object 3 to be formed and defines a printing area.

[0098] This support 2 is arranged at a certain height so that each layer being solidified rests on a work surface 18 integrated in a surface of a work table 4 having an opening at the level of the container 1. The container 1 is arranged under the work table 4, so that its upper edge is flush with the work table 4.

[0099] More precisely, in the initial phase, the support 2 is arranged flush with the surface of the work table 4. The first layer of the object 3 can be produced directly on the support 2. Then the support 2 descends by one notch, corresponding to the thickness of the first layer produced. The first layer then forms a work surface that is flush with the surface of the work table 4. Then, the second layer of the object 3 can be produced at the level of this work surface 18. And so on.

[0100] A distributor 7 for glass powder 6 is arranged above the work table 4. This distributor 7 comprises a reservoir filled with glass powder 6, which is the material used to form the glass object 3.

[0101] The distributor 7 initially pours a dose of powder onto the work table 4, and in particular onto the support 2.

[0102] Then a brush 5 or a roller performs a horizontal pass over the work table 4 so as to distribute the glass powder evenly on the support 2.

[0103] A laser beam 15 is then directed towards the support 2 to cause the fusion glass powder 6 to enter the locations appropriate to the pattern of the first layer of the object 3 to be formed.

[0104] Once this first layer is fused, the support 2 descends by one notch, and the distributor 7 pours a new dose of glass powder 6 onto the work table 4, and in particular onto the work surface 18 formed by the previous layer of glass powder 6.

[0105] The brush 5 completes its pass, and then the laser beam 15 is switched on again to cause the fusion glass powder 6 to enter the locations appropriate to the pattern of the second layer of the object 3 to be formed.

[0106] Once this second layer is fused, the support 2 descends by one notch, and all the above operations are repeated n times, until the object 3 is completed.

[0107] The support 2 is preferably made of a non-thermally insulating material, for example metal. The support 2 is mobile in vertical translation, for example by means of cylinders.

[0108] Underneath the support 2, a heating system is installed, so that the support 2 is heated to a predefined temperature. In this example, it is an induction device 14. The preset temperature must be close to the glass transition temperature of the glass powder 6, so that the powder 6 is heated and starts to fuse via the support 2.

[0109] A second heating system is set up, this time above the work table 4, i.e. above the support 2, so as to heat the upper layer of the object 3 being produced. This reduces the potential temperature difference that may exist between the lower layer of the object 3 and the upper layer of the object. In this example, it is a retractable radiative heating 11.

[0110] These heating systems allow the object being created to be held at a holding temperature between the glass transition temperature minus 100° C. and the softening temperature of the glass. Such a holding temperature allows to limit the temperature gradient between the fusion point and the adjacent points. It also allows to limit the temperature gradient during the controlled cooling of the object after its creation.

[0111] In order to obtain a homogeneous temperature inside the object 3 being created and outside, the support 2, the work table 4, the distributor 7 and the various heating systems 14, 11 can be positioned within a thermal enclosure 17, thus isolated from the outside. This enclosure 17 defines a chamber in which the temperature is homogeneous at all points. The environment in which the object 3 is built is thus homogeneous from a thermal point of view, and this allows to preheat each powder bed, and each new stratum of the object 3, as it is created, to the desired holding temperature.

[0112] The laser 8 is arranged outside the enclosure 17, as it is not designed to withstand such temperatures.

[0113] The laser 8 is arranged above the enclosure 17, and emits a beam 15 whose optical path is redirected towards the support 2, via an orientable mirror 10. The different orientations of the mirror 10 allow the beam 15 to follow a precise path on the powder layer in order to make a section of the object 3.

[0114] Indeed, the object 3 has been previously modelled using a software, and a central unit (electronic board) controls the movements of the mirror 10 so that the beam 15 follows the path foreseen in the model.

[0115] The beam 15 passes through a specific window 16 provided in the upper wall of the enclosure 17. This window 16 may consist of a lens 16 which allows the beam 15 to converge on a precise point at the level of the work surface 18.

[0116] The central unit 9 also controls the movements of the brush 5 and the support 2.

[0117] In addition, means for servo-controlling the power and the speed of the laser are installed. They comprise an optical sensor 12 that captures the light produced by the fusion point. This sensor 12 is positioned above the support 2, and aims at the area where the object 3 is created.

[0118] This optical sensor 12 sends the information to the central unit 9, which processes it, and which then adjusts in real time the power of the laser 8 and its speed, so that the fusion is optimal at any point of the object 3 being created.

[0119] Once the object 3 is created, it must be cooled in a certain way, in order to avoid its embrittlement at the time of cooling. The cooling of the object 3 is predefined, and follows a specific temperature curve, with or without threshold, depending on the composition of the glass used.

[0120] For this purpose, the device comprises, for example, a thermocouple 13 which is positioned in contact with the object 3 and which measures the temperature of the object 3 during the cooling.

[0121] This thermocouple 13 sends the measured temperature to the central unit 9, which then adjusts in real time the various heating systems 14, 11 in order to regulate the temperature within the enclosure 17 and within the object 3, so that it follows the imposed curve.

[0122] It is also possible to anneal the object 3, also according to a predefined temperature curve, so as to reinforce its mechanical properties. This annealing is enabled via the heating systems 14, 11, and is controlled by the central unit 9 and the thermocouple 13.

Example of 3D Printing According to the Invention

[0123] The 3D printing device according to the invention was able to produce 3D objects with the following parameters: [0124] using soda-lime glass in microbeads [0125] grain size between 100 μm and 200 μm [0126] glass transition temperature Tg of the glass above 500° C. [0127] softening temperature of the glass Tr around 600° C. [0128] holding in temperature at 550° C. [0129] interval between each layer set to 0.6 mm: this interval corresponds to the thickness of one layer for the object 3 and to the height of one notch for the support 2 [0130] interval between each passage line of the laser on the printing surface set at 0.7 mm [0131] printing speed of the laser of 15 mm/s [0132] power of the laser beam of 1.6 W [0133] laser type: CO laser [0134] laser wavelength: from 5.6 to 6.2 μm [0135] lens converging in ZnSe arranged in the optical path of the laser beam [0136] control via a minitronics v1.1 type electronic board with embedded software [0137] holding temperature threshold at 550° C., then slow descending in temperature

[0138] FIG. 2 shows the laser fusion of glass powder.

[0139] The glass powder 6 in FIG. 1 is shown here as a thick first layer, to improve the clarity of the diagram, with cold powder areas 20, and hot areas 21-22-23. The beam 15 of the laser is aimed at the upper surface of this glass powder layer, and moves progressively from left to right, according to the large horizontal arrow. To the left, glass is already fused and solid. The closer you get to the fusion point 23 on the right, the hotter the glass becomes. This temperature rise is illustrated by the small points. The more points, the higher the temperature. A fusion bath 22 is visible around the fusion point 23. During the 3D printing, the fusion bath 22 moves with the movement of the laser beam 15. The same applies to the fusion point 23.

[0140] There is a contact area 25 between the hot glass of the fusion bath 22 and the cold glass powder 20. The fusion bath 22 comes therefore continuously into contact with cold glass beads 20, which disrupt the fusion process. In fact, the so-called cold glass beads 20 are present on the front and the periphery of the fusion bath 22 and are not fused. They are considered disruptive and can cause the reflection or the absorption of the laser beam 15, as illustrated by the small oblique arrows.

[0141] The heat emanating from the fusion point 23 is captured by a brightness sensing and measuring device 12 at the periphery of the fusion. This device 12 corresponds, for example, to the optical sensor. It is arranged above the fusion bath 22 and slightly upstream of the laser beam 15, so as to point to each new fusion area each time the beam 15 advances. It points precisely to the front of the fusion bath 22, which here corresponds to the right side of the fusion bath 22, and which also corresponds to the front of the fusion point 23, since this is also where the reflections of the laser can occur and disturb the fusion. It is therefore essential to know the exact temperature at this point in order to be able to adjust the laser parameters until the desired temperature is reached in the program. The area that fuses takes on a certain color with a certain light intensity depending on its temperature. The sensor senses the light intensity emitted by the fusion bath, so that the actual temperature can be deduced.

[0142] FIG. 3 illustrates schematically the servo-control of the laser.

[0143] The brightness sensing and measuring device 12 senses the light emitted from the front of the fusion point 23. It sends this light signal (a) to an instrumentation electronics 26 to condition the measured signal. This electronics 26 allows to convert this signal into a measured brightness data (b) and sends it to a brightness controller 28 which belongs to the central unit 9.

[0144] At the same time, the control electronic board 27 of the printer provides data (c) to the brightness controller 28 to control the laser 8. In particular, it sends a desired light intensity data, which is a function of a desired temperature at the front of the fusion bath 22.

[0145] This brightness controller 28 analyzes and compares the input data (b) and (c) emitted from the optical sensor 12 on the one hand, and from the control board 27 on the other hand. Based on the measured difference between the data, it will adjust the power of the beam 15 and the speed (d) of the laser 8 in real time and control them at the output, in order to control the ongoing fusion, so that the measured light intensity is as close as possible to the desired light intensity, i.e. the measured temperature is as close as possible to the desired temperature.

[0146] The laser 8 therefore sends its beam 15 with a power and a speed controlled in real time.

[0147] The brightness control system operates in a closed loop with respect to a desired light intensity (i.e., a desired temperature) and provides a power and speed adjustment to drive the laser 8.

[0148] The embodiments shown in the cited figures are only possible examples, in no way limiting, of the invention which, on the contrary, encompasses the variations of shapes and designs within the reach of the person skilled in the art.