METHOD FOR PRODUCING A THREE-DIMENSIONAL GLASS OBJECT AND GLASS FIBRES SUITABLE FOR THEREFOR

Abstract

Known methods of producing a three-dimensional glass object comprise the step of shaping of a glass fiber, wherein the glass fiber provided with a protective sheath is fed continuously to a heating source, the protective sheath is removed under the influence of heat, and the glass fiber is softened. In order to facilitate the production of filigree or optically distortion-free and transparent glass objects as much as possible, and also enable the adjustment of optical and mechanical properties with high spatial resolution, in one aspect the glass fiber has a protective sheath with a layer thickness in the range of 10 nm to 10 μm.

Claims

1-16. (canceled)

17. A method of producing a three-dimensional object from quartz glass, comprising: shaping a glass fiber; wherein the glass fiber is provided with a protective sheath and is continuously fed to a heating source; wherein the protective sheath is removed under the influence of the heating source, and the glass fiber is softened; and wherein the protective sheath of the glass fiber has a layer thickness in the range of 10 nm to 10 μm.

18. The method according to claim 17, wherein the protective sheath of the glass fiber has a layer thickness of less than 1 μm.

19. The method according to claim 17, wherein the glass fiber is fed to the heating source at a feed rate of at least 450 mm/min.

20. The method according to claim 17, wherein the glass fiber has a diameter in the range of 50 μm to 300, and is wound on a take-up reel and is fed to the heating source by unwinding from the take-up reel.

21. The method according to claim 17, wherein a longitudinal section of the glass fiber, in which the protective sheath has been removed, has a length in the range of 0.5 to 2 cm.

22. The method according to claim 17, wherein the protective sheath consists only of the components carbon, silicon, hydrogen, nitrogen, and oxygen.

23. The method according to claim 17, wherein the protective sheath has a decomposition temperature of less than 400° C.

24. The method according to claim 17, wherein the protective sheath consists of an organic material, of polysaccharides or surfactants, of cationic surfactants, or of a polyether polymer, polyethylene glycol, polyalkylene glycol, polyethylene oxide or polyalkylene oxide.

25. The method according to claim 17, characterized in that the protective sheath is produced from one or more fluorine-free silanes or from fluorine-free surfactants, or cationic fluorine-free surfactants.

26. The method according to claim 17, wherein the protective sheath is produced on the glass fiber by dipping or roller coating.

27. A glass fiber for the manufacture of a three-dimensional object from glass, wherein the glass fiber is provided with a protective sheath having a layer thickness in the range of 10 nm to 10 μm.

28. The glass fiber according to claim 27, wherein the protective sheath has a layer thickness in the range of of less than 1 μm.

29. The glass fiber according to claim 27, wherein the glass fiber has a diameter in the range of 50 μm to 300 μm.

30. The glass fiber according to claim 27, wherein the glass fiber is wound on a take-up reel with a minimum winding diameter of less than 30 cm.

31. The glass fiber according to claim 27, wherein the protective sheath contains an organic material with a decomposition temperature of less than 400° C.

32. The glass fiber according to claim 27, wherein the protective sheath consists of an organic material, of polysaccharides or of surfactants, of cationic surfactants, or of a polyether polymer, polyethylene glycol, polyalkylene glycol, polyethylene oxide or polyalkylene oxide.

Description

EXEMPLARY EMBODIMENTS

[0050] The invention will be explained in more detail below with the aid of an exemplary embodiment and a drawing. In detail, the figures show schematic diagrams of the following.

[0051] FIG. 1: a first embodiment of the experimental set-up for carrying out tests on build-up welding using glass filaments according to the invention,

[0052] FIG. 2: a microscope image of a preliminary build-up welding test using a reference glass fiber,

[0053] FIG. 3: a microscope image of a preliminary build-up welding test using a glass fiber according to the invention, and

[0054] FIG. 4: a further embodiment of the experimental set-up for carrying out tests on build-up welding using glass filaments according to the invention.

PRELIMINARY TESTS

[0055] To examine the handling characteristics, weldability and general behavior, preliminary build-up welding tests were performed on quartz glass fibers with different protective sheaths. Results are shown in the microscope images of FIGS. 2 and 3. The scale bars 25 each denote a length of 1 mm.

[0056] In these tests, quartz glass fibers with a diameter of 220 μm and with a standard plastics sheath with a thickness of approx. 62.5 μm were employed as reference fibers “R”, and they were performed with quartz glass fibers with the same diameter but with a thin sheath according to the invention (glass fibers 2). The sheath has a thickness of less than 50 nm. Its composition and production will be explained in more detail below.

[0057] The quartz glass fibers (R; 2) were each placed directly on a quartz glass sheet and affixed with adhesive tape. An oxyhydrogen heating torch was used in each case as the heating source for softening the quartz glass fibers and burning off the coatings. The oxyhydrogen torch provided the heat needed to melt the quartz glass fibers and at the same time oxygen for the pyrolysis of the protective sheath because of hyperstoichiometric oxygen in the oxyhydrogen flame.

Observations and Results:

[0058] It was shown that the reference glass fiber “R” always moved and twisted under the influence of the heating torch. This can be explained by the gases arising, as well as non-axial stresses caused by the non-uniform burning off of the coating. For this reason, the ends of the fiber were fastened to the quartz glass sheet with adhesive tape before welding, in order to at least limit this movement.

[0059] This behavior was not displayed by the glass fibers 2 with the thin coating. This glass fiber 2 was significantly easier to handle during welding and also did not have to be secured.

[0060] Both types of fiber were able to be welded on to the substrate 7. Despite being secured, however, the reference glass fibers R could not be welded on to the substrate 7 in a straight line. The waviness of the welded fibers was 5 mm per 120 mm welded length for the reference glass fiber, and in the case of the glass fiber 2 according to the invention a highly rectilinear weld was obtained without significant waviness.

[0061] The bright reflections 26 on the image of FIG. 2 make the twisting of the reference glass fiber on the base clear. The black dots 27 additionally show that more bubbles formed along the welded length in the reference glass fiber R than in the glass fiber 2 according to the invention. For every 5 cm length, twenty-one bubbles were counted in the reference glass fiber R.

[0062] FIG. 3 shows the result of the welding test using the glass fiber 2 according to the invention. This shows a rectilinear course along the welded length and, in addition, a low number of only six bubbles for a 5 cm length.

[0063] FIG. 1 is a diagram of the experimental set-up for carrying out the additive manufacture of a glass object 1 by build-up welding using a glass fiber 2 that has been determined to be suitable with the aid of the preliminary tests.

[0064] Here, the glass fiber 2 wound on a winding reel with a minimum diameter of 30 cm is unwound from the winding reel continuously by means of a fiber-guiding system (not shown in the figure) and fed through a guide sleeve 24 to a melting zone 6a, in which a defocused laser beam 3 acts as a heating source. Peaks in heat distribution are compensated by the defocusing, which is indicated in the figure as a broken line around the laser beam 3. Ideally, the laser beam 3 is approximately twice as wide at the point of impingement as the diameter of the glass fiber 3 to be melted, so that both the glass fiber 3 and the surrounding region, and in particular the substrate 7, are heated.

[0065] The glass fiber's longitudinal axis 21 here forms an angle of approx. 90 degrees with the main extension direction 31 of the laser beam 3. A CO.sub.2 laser with a maximum output power of 120 W is used as the laser. The laser beam 3 melts the end of the glass fiber 2 continuously, and it heats the protective sheath 22 of the glass fiber so that this is thermally decomposed. In addition, it softens the surface of the substrate 7, thus promoting adhesion between molten glass of the glass fiber 2 and the glass substrate 7. The heating zone produced by the laser beam 3 is indicated schematically in FIG. 1 by the region 6b shaded in grey.

[0066] A suction tube 5 projects as close as possible to the melting zone 6a. The platform consisting of a glass substrate 7 lies on a digitally controlled translation stage (indicated by the x-y-z system of coordinates 4) and is displaceable in all spatial directions.

[0067] The glass fiber 2 has a circular cross-section and a diameter of 220 μm. It is provided with a very thin sheath 22 having a thickness of less than 100 nm.

[0068] The (thin) layer 22 is produced by drawing the glass fiber 2 through a 10% aqueous solution of cetyltrimethylammonium chloride.

[0069] The layer 22 has a decomposition temperature of less than 400° C. It is so thin that it can be completely burnt off rapidly and efficiently online, immediately upstream of the melting zone 6a, while the glass fiber 2 is continuously fed further to the melting zone 6a.

[0070] This allows a high processing speed. The glass fiber feed rate to the melting zone 6a is adjusted to a value in the range of 300 to 600 mm/min such that the 22 is always completely removed before the glass fiber 2 reaches the melting zone 6a, and in addition such that the longitudinal portion 23 in which the sheath 22 has already been completely removed has a length of less than 2 cm. As a result, mechanical damage to the uncoated glass fiber 2 is prevented.

[0071] In addition, owing to the low layer thickness of the sheath 22, only a few combustion products are obtained, which can be readily removed by means of the suction 5. This allows bubble-free fusion of the glass fiber 2 with the substrate 7.

[0072] The result of the welding of glass fiber 2 and substrate 7 is a three-dimensional glass object 1 without defects and bubbles.

[0073] FIG. 4 is a diagram of a variation of the experimental set-up for carrying out the additive manufacturing of a glass object. The same reference numerals as in FIG. 1 are used here to denote identical or equivalent components of the set-up.

[0074] In contrast to the set-up of FIG. 1, the glass fiber's longitudinal axis 21 here forms a somewhat more acute angle of 45 degrees with the main extension direction 31 of the laser beam 3. As a result of the different orientation of the laser beam 3 compared to FIG. 1, the heating region 6b also displays a different extension and a different focus. It covers a larger region of the glass fiber 2 and thus brings about a more effective heating of glass fiber 2 and protective sheath 22 at the same temperature.

[0075] In this case too, the suction tube 5 is brought as close as possible to the melting zone 6a.