Stereolithography Device Having A Heating Unit

Abstract

A stereolithography device having a trough (2) for accommodating free-flowing, photopolymerizable material, a construction platform (4) suspended above the trough bottom on a lifting unit (6), and having a heating unit for heating the photopolymerizable material in the trough. The heating unit has a transparent, electrically conductive layer (33), which covers the entire area of at least the exposure region above the trough bottom, and which is provided outside the exposure region on opposing sides of the layer with electrical contacts (20) extended over the opposing sides, which are connected to a controlled electrical supplier to enable heating of the entire area of photopolymerizable material above the trough bottom in the exposure region by current flow through the layer.

Claims

1. A stereolithography device having a trough (2) for accommodating free-flowing, photopolymerizable material, which has a transparent trough bottom (3) at least in an exposure region provided for exposures, an exposure unit (8), which is arranged below the trough, for exposing a surface having a predefined contour for the layer to be formed in each case inside the exposure region, a construction platform (4) suspended above the trough bottom on a lifting unit (6), on which the first layer cured by exposure is to be formed suspended thereon, a control unit, which is configured to cause successive exposures each having predefined contour by way of the exposure unit and to adapt the position of the construction platform above the trough bottom successively in each case after the exposure of a further layer, and having a heating unit for heating the photopolymerizable material in the trough, characterized in that the heating unit has a transparent, electrically conductive layer (33), which covers the entire area of at least the exposure region above the trough bottom, and which is provided outside the exposure region on opposing sides of the layer with electrical contacts (20) extended over the opposing sides, which are connected to a controlled electrical supplier to enable heating of the entire area of photopolymerizable material above the trough bottom in the exposure region by current flow through the layer.

2. The stereolithography device according to claim 1, characterized in that the electrically conductive coating (33) is applied to a transparent plastic film as a carrier film (35), which is in turn arranged above the trough bottom.

3. The stereolithography device according to claim 1, characterized in that the trough bottom is formed in the exposure region by a transparent plastic carrier film, above which the electrically conductive layer lies.

4. The stereolithography device according to claim 1, characterized in that firstly a transparent silicone layer (32) is applied above the trough bottom (3), the electrically conductive layer (33) is applied above this, and a transparent plastic protective film (37) is applied above this to cover the electrically conductive coating.

5. The stereolithography device according to claim 1, characterized in that the electrically conductive layer (33) lies above the trough bottom (3), above which a transparent silicone layer (32) is arranged, which is finally covered by a plastic protective film (37) arranged above it for the cover.

6. The stereolithography device according to claim 1, characterized in that a temperature sensor is arranged on the electrically conductive layer (33) in heat conductive contact therewith, this sensor being connected to a controller, which is configured to control the current flow through the electrically conductive coating so that a desired temperature or a desired chronological temperature curve is caused in the region of the electrically conductive coating above the trough bottom.

7. The stereolithography device according to claim 2, characterized in that films made of polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), or polyfluoroethylene propylene (FEP) are plastic carrier films (35) for the electrically conductive coating.

8. The stereolithography device according to claim 4, characterized in that the plastic protective films (37) are films made of polytetrafluoroethylene (PTFE) or polyfluoroethylene propylene (FEP).

9. The stereolithography device according to claim 1, characterized in that the material of the electrically conductive layer has indium tin oxide (ITO), tin oxide doped with fluorine (SnO2:F), tin oxide doped with aluminum (ZnO2:Al), aluminum zinc oxide (AZO), tin oxide doped with antimony (SnO2:Sb), graphene or other electrically conductive carbon compounds, electrically conductive polymers, or suitable metallic compounds.

10. The stereolithography device according to claim 1, characterized in that the electrically conductive transparent coating is implemented so that it has a sheet resistance in the range of 1-1000 Ω/□.

11. The stereolithography device according claim 1, characterized in that electrical heating units are also provided on the trough bottom in the region outside the exposure region.

12. The stereolithography device according to claim 11, characterized in that the electrically conductive transparent layer (33) extends beyond the exposure region above the trough bottom (3).

Description

[0029] The invention will be explained hereafter on the basis of exemplary embodiments in conjunction with the drawings, in which:

[0030] FIG. 1 shows a schematic illustration of components of a stereolithography device according to the invention,

[0031] FIG. 2 shows a cross-sectional view through a trough bottom of a stereolithography device according to a first embodiment together with an enlarged detail view,

[0032] FIG. 3 shows a cross-sectional view through a trough bottom of a stereolithography device according to a second embodiment together with an enlarged detail view,

[0033] FIG. 4 shows a cross-sectional view through a trough bottom of a stereolithography device according to a third exemplary embodiment together with an enlarged detail view,

[0034] FIG. 5 shows an exploded view of the trough bottom from FIG. 3.

[0035] FIG. 1 schematically shows individual components of a stereolithography device (however, without carrier and housing parts). The stereolithography device has a trough 2 having transparent trough bottom 3, into which free-flowing photopolymerizable material 1 is poured. In the photopolymerizable material 1 (during the buildup of the first layer on a construction platform 4), this construction platform 4 is lowered into the photopolymerizable material 1 until the underside of the construction platform 4 is located at a predefined distance to the trough bottom, so that just the desired layer thickness of photopolymerizable material remains between the construction platform and the trough bottom. After curing of the first layer on the construction platform 4, it is raised, photopolymerizable material is reintroduced from the outside into the exposure region (if the photopolymerizable material is not sufficiently liquid to flow by itself into the exposure region, a squeegee blade movable in relation to the trough bottom can be used to push photopolymerizable material into the exposure region). The construction platform 4 having the layer already formed thereon is subsequently lowered into the photopolymerizable material 1 until the underside of the last-formed layer has the distance to the trough bottom which is equal to the desired layer thickness for the layer, which is to be cured next, made of photopolymerizable material. These steps are successively repeated with formation of successive layers, each having predefined contour, until the sequence of the layers results in the desired molded body.

[0036] For the controlled raising and lowering of the construction platform 4, it is suspended on a controllable lifting unit 6.

[0037] An exposure unit 8 is arranged below the trough 2, which is oriented from below on an exposure region on the trough bottom 3. The exposure unit 8 is implemented for the purpose of generating a desired pattern of individually activated image elements in the exposure region under the control of a control unit, wherein the shape of the layer to be cured results from the exposed image elements. The exposure unit 8 can have, for example, a light source and a field having a large number of micromirrors, which are individually pivotable by a control unit to either expose or not expose the associated image element in the exposure region. In addition, the intensity of the exposed image elements can also be controlled in a location-dependent manner as desired by turning the individual micromirrors on and off.

[0038] The trough bottom 3 is implemented as transparent at least in the exposure region, for example, by a thin glass pane. The term transparent for the trough bottom and for the electrically conductive layer to be described in greater detail hereafter means that they are light-transmissive to a certain extent, nearly complete light transmissivity does not have to be provided for this purpose. Any possible attenuation of the electromagnetic waves used for the exposure in the material of the trough bottom or the electrically conductive layer can be taken into consideration beforehand by increasing the illumination intensity or the illumination duration accordingly.

[0039] FIG. 2 shows a schematic cross-sectional view through a trough bottom 3 and a heating unit applied thereon in the exposure region and also an enlarged detail view from the cross section. The trough bottom has a glass plate 31, on which a transparent silicone layer 32 is applied. A plastic carrier film 35 is laid on the silicone layer 32, which has an electrically conductive, transparent coating 33 on its underside. The plastic carrier film 35 can be, for example, a film made of polypropylene, polytetrafluoroethylene, polyfluoroethylene propylene, or polyethylene. The electrically conductive transparent coating can consist, for example, of indium tin oxide. A transparent plastic protective film 37 is in turn applied to the transparent plastic carrier film 35. However, such a transparent plastic protective film 37 can also be omitted in the present exemplary embodiment, since the electrically conductive, transparent layer 33 is already covered and protected by its plastic carrier film 35.

[0040] It is to be noted that the cross-sectional views as in FIG. 2 are only schematic and are not to scale, i.e., the relative layer thicknesses are not to be realistically shown thereby. Furthermore, the transparent, electrically conductive layer 33, which is shown as relatively thin, is illustrated by a black line for reasons of illustration, which is only to make it better visible and is meant solely symbolically. In fact, all layers in the layer composite should be transparent.

[0041] FIG. 3 shows a cross section of a second exemplary embodiment corresponding to FIG. 2, which differs from that from FIG. 2 in that the transparent silicone layer 32 and the transparent plastic carrier film 35 having the electrically conductive, transparent layer 33 on their underside have exchanged their positions, i.e., the plastic carrier film 35 lies with the electrically conductive, transparent layer 33 directly on the transparent trough bottom 31.

[0042] FIG. 4 shows a cross-sectional view of a third exemplary embodiment, corresponding to the two preceding exemplary embodiments in FIGS. 1 and 2, which differs from the second exemplary embodiment in FIG. 3 in that the electrically conductive transparent layer 33 is not applied to a plastic carrier film 35 as in FIG. 3, but rather the electrically conductive, transparent layer 33 is applied directly to the transparent glass plate 31, and the transparent silicone layer 32 directly follows the electrically conductive, transparent layer 33, and the transparent plastic protective film 37 follows thereon.

[0043] FIG. 5 shows the structure of the trough bottom having heating unit of the second exemplary embodiment in an exploded view, i.e., the transparent trough bottom and the layers following thereon are lifted off of one another. In FIG. 5, the electrical contacting of the electrically conductive, transparent layer 33 is shown. This is performed by two opposing strips 20 of a thin metallic conductor, wherein these band-shaped metallic conductor strips lie directly on the opposing edge strips of the electrically conductive, transparent layer 33. Each of the two metal strips 20 is connected to an electrical line, which, together with an electrical supplier having controller (not shown), form a power circuit, to generate a desired heating power by way of controlled current flow through the electrically conductive, transparent layer 33.

[0044] To control the electrical power to be supplied by the electrical supplier, a temperature sensor can be arranged on the electrically conductive, transparent layer 33 in heat conductive contact with the electrically conductive, transparent layer 33, to detect its temperature. The temperature sensor is provided with a controller, which is in turn connected to the controllable electrical supplier in order to control its power, so that a desired temperature is set on the electrically conductive, transparent layer 33.