Abstract
Device (1) for a system for layer-by-layer construction of a body (K) from a substance (S) which can be hardened by radiation, comprising a vat (3) having a vat base (2) for receiving the substance (S) which can be hardened by radiation, comprising a building platform (4) which is arranged above the vat base (2) and which is height-adjustable in relation to the vat base (2) and comprising a sensor (5) cooperating with the vat base (2), wherein the vat base (2) is configured to be at least partially flexible, wherein a chamber (6) is provided wherein the chamber (6) is delimited by an underside of the vat base (2), wherein the sensor (5) is adapted to detect a volume change of the chamber (6) and to provide a sensor signal from which a sign of the volume change can be determined.
Claims
1. Device for a system for layer-by-layer construction of a body (K) from a substance (S) which can be hardened by radiation, comprising: a vat having a vat base being configured to be at least partially flexible, wherein the vat is configured for receiving the substance (S) which can be hardened by radiation, a building platform which is arranged above the vat base and which is height-adjustable in relation to the vat base, and a sensor cooperating with the vat base, and a chamber that is delimited by an underside of the vat base, wherein the sensor is adapted to detect a volume change of the chamber and to provide a sensor signal from which a sign of the volume change can be determined, wherein the sensor is adapted to quantitatively detect a measured, variable directly or indirectly proportional to the volume of the chamber or to the volume change and to provide the measured variable as a sensor signal, wherein the sensor is a pressure sensor or a flow sensor such that the pressure sensor is adapted to detect a pressure and/or a pressure change of a compressible medium (M) received in the chamber, wherein the pressure change corresponds to the volume change, and such that the flow sensor is adapted and arranged to detect a change in an amount of the substance enclosed in the chamber of a fluid received in the chamber, wherein the change in the amount of the substance corresponds to the volume change, wherein the sensor is adapted to provide a detected pressure and/or a detected pressure change and/or a detected change in the amount of substance as a measured variable and sensor signal.
2. (canceled)
3. (canceled)
4. Device according to one of claim 1, wherein the sensor is connected to a processing unit which is adapted to process the sensor signal provided by the sensor.
5. Device according to claim 4, wherein the sensor is connected, via the processing unit to (i) a first drive unit for adjusting the height of the building platform and/or (ii) to a control unit for irradiation by a radiation source of the substance (S) which can be hardened by radiation, and wherein the processing unit is adapted to control (i) the a first drive unit for the height-adjustable building platform and/or (ii) the control unit for the radiation source depending on the sensor signal provided by the sensor.
6. Device according to claim 1, wherein the chamber is connected to at least one adjustable pressure source for setting a resting pressure in the chamber and/or an adjustable heating device for setting a temperature in the chamber and/or an adjustable process substance source for the adjustable supply of a process medium (Mi) for the at least local manipulation of the solidification process of the substance (S) which can be hardened by radiation into the chamber and/or an air flow source for producing an air flow in the chamber.
7. Device according to claim 4, wherein the sensor is connected via the processing unit to (i) the adjustable pressure source and/or (ii) the adjustable heating device and/or (iii) the adjustable process substance source and/or iv) the air flow source, and wherein the processing unit is adapted to control (i) the pressure source and/or (ii) heating device and/or (iii) the process substance source and/or (iv) the air flow source depending on the sensor signal provided by the sensor.
8. Device according to claim 1, wherein the vat base is at least partially permeable to radiation and includes a flexible, tensioned foil.
9. Device according to claim 1, wherein the vat base is configured to be semi-permeable, permeable for a process medium (Mi).
10. Device according to claim 1, wherein at least a part of the vat base rests on a carrier plate which is at least partially permeable to radiation.
11. Device according to claim 10, wherein the carrier plate is configured to be permeable for a process medium (Mp) or comprises elevations resting on the vat base for passage of a process medium (Mp) between the elevations.
12. Device according to claim 1, further comprising a doctor blade which is movable in the vat on the vat base.
13. Device according to claim 12, wherein the sensor is connected to a second drive unit of the doctor blade via a processing unit and the processing unit is adapted to control the second drive unit of the doctor blade depending on the sensor signal provided by the sensor.
14. Device according to claim 1, wherein the vat base is an operable cover of a chamber housing of the chamber.
15. Method for the layer-by-layer construction of a body (K) from a substance (S) which can be hardened by radiation and which is received in a vat having a vat base, in which for each layer (K1, . . . Kn) of the body (K) to be formed from a building platform which is height adjustable in relation to the vat base, the method comprising the steps of: moving the building platform into a height above the vat base wherein the height defines a distance between the building platform or the last-formed layer (Kn) of the body (K) to the vat base selectively hardening the substance (S) by means of a radiation source to form the layer (Kn+1) of the body (K) moving the building platform away from a rest position of the vat base to create space for the formation of a next layer (Kn+2) between the hardened layer (Kn+1) of the body (K) and the vat base, wherein the vat base is configured to be at least partially flexible; detecting at least one process parameter by a sensor cooperating with the vat base, detecting by the sensor a volume change of a chamber and providing a sensor signal from which a sign of the volume change is determined, wherein the chamber is delimited by an underside of the vat base, and wherein the volume of the chamber is varied by process-dependent deflections of the vat base from the rest position, wherein the sensor quantitatively detects a measured variable directly or indirectly proportional to the volume of the chamber or to the volume change and provides the measured variable as a sensor signal, and wherein the sensor is a pressure sensor or a flow sensor, wherein the pressure sensor detects a change in the pressure of a compressible medium (M) in the chamber as a measured variable, such that the change in the pressure corresponds to the volume change, or wherein the flow sensor detects a change in the amount of substance of the amount of substance of a fluid enclosed in the chamber as a measured variable, such that the change in the amount of substance corresponds to the volume change.
16. (canceled)
17. (canceled)
18. Method according to claim 15, wherein the sensor signal provided by the sensor is processed in a processing unit connected to the sensor and at least one process parameter is set depending on the sensor signal provided by the sensor.
19. Method according to claim 18, wherein the processing unit compares the detected measured variable provided as the sensor signal with a predicted value and/or compares the behaviour of detected measured variables with a behaviour of a plurality of predicted values and sets the at least one process parameter depending on the difference between the measured variable and the predicted value and/or between the behaviour of the measured variables and the behaviour of the plurality of predicted values.
20. Method according to claim 19, wherein changes in the measured variable detected by the sensor and provided as the sensor signal are processed in a processing unit connected to the sensor in a simulation model of the plurality of predicted values of the construction process and at least one process parameter is set depending on at least one detected measured value of the measured variable and/or on the change in detected measured values as specified by the simulation model.
21. Method according to claim 19, wherein the predicted value and/or the plurality of predicted values is or are calculated depending on at least one process parameter by the processing unit.
22. Method according to claim 20, wherein the simulation model takes into account at least one set process parameter as an input value.
23. Method according to claim 18, wherein based on the sensor signal provided by the sensor, determining the height of the building platform and/or of the last-hardened layer (Kn) of the body (K) in relation to the rest position of the vat base and/or a motion speed of the building platform and/or the size of an area of the last-hardened layer (Kn) of the body (K) as a process parameter in the processing unit when the vat base is deflected from the rest position by movements of the building platform.
24. Method according to claims 18 to 23, wherein depending on the sensor signal provided by the sensor, controlling as one or more process parameters (i) a height adjustment of the building platform by means of a first drive unit for the budding platform, in which the first drive unit is connected to the building platform and to the processing unit, and/or (ii) an irradiation of the substance (S) which can be hardened by radiation by the processing unit by means of a control unit for the radiation source, in which the control unit is connected to the processing unit and the radiation source.
25. Method according to claim 18, wherein depending on the sensor signal provided by the sensor, setting as one or more processing parameters by the processing unit (i) a resting pressure in the chamber by means of at least one adjustable pressure source that is connected to the chamber and the processing unit and/or (ii) a temperature in the chamber by means of at least one adjustable heating device that is connected to the chamber and the processing unit and/or (iii) a supply of a process medium (Mp) into the chamber by means of at least one adjustable process substance source that is connected to the chamber and the processing unit and/or (iv) an air flow in the chamber by means of at least one air flow source that is connected to the chamber and the processing unit.
26. Method according to claim 18, further comprising the step of determining at least one process parameter in the processing unit from the sensor signal provided by the sensor wherein in the at least one process parameter is selected from the group consisting of (i) a release of a last-hardened layer (Kn) of the body (K), which layer (Kn) adheres to the vat base, from the vat base; (ii) a release height; (iii) a release speed of a last-hardened layer (Kn) of the body (K), which layer (Kn) adheres to the vat base, from the vat base; (iv) a touching of the vat base; (v) a contact pressure of a doctor blade which is movable in the vat, on the vat base; (vi) a body (K) incorrectly released from the building platform; (vii) a vat ageing; (viii) an unexpected adhesion of the body (K) on the vat base when supplying an inhibitor medium (Mi) into the chamber and onto the substance (S) which can be hardened by radiation; (ix) a fill level of the substance (S) which can be hardened by radiation in the vat; (x) a provision of the vat and (xi) a crack or hole in the vat base or in the chamber.
27. Method according to claim 18, wherein depending on the sensor signal provided by the sensor, setting a negative pressure deflecting the vat base away from the building platform in the chamber by the processing unit for the release of a last-hardened layer (Kn) of the body (K), which layer adheres to the vat base, during movement of the height-adjustable building platform away from the resting position of the vat base.
28. Method according to claim 18, wherein depending on the sensor signal provided by the sensor, setting an excess pressure to deflect at least a portion of the vat base towards the building platform in the chamber by the processing unit before a touching of the building platform or of the last-hardened layer (Kn) of the body (K) on the vat base.
29. Method according to claim 18, further comprising the steps of: moving the height-adjustable building platform with a last-hardened layer (Kn) of the body (K), which layer adheres to the building platform and to the vat base, away from a rest position of the vat base, determining a release of the last-hardened layer (Kn) of the body (K), which layer adheres to the vat base, from the vat base in the processing unit by means of the sensor, moving the height-adjustable building platform into a height (Zx+1) above the rest position of the vat base which height defines a distance between the last-hardened layer (Kn) of the body (K) to the rest position of the vat base in the extent of at least the thickness of the layer (Kn+1) of the body (K), which layer is to be newly formed, and selectively hardening the substance (S) by means of the radiation source by irradiation to form the new layer (Kn+1) of the body (K).
30. Method according to claim 18, wherein an inhibitor medium (Mi) is supplied via the chamber to the substance (S) which can be hardened by radiation and the height-adjustable building platform with a last-hardened layer (Kn) of the body (K), which layer adheres to the building platform, is moved into a height (Zx+1) above the rest position of the vat base which height defines a distance between the last-hardened layer (Kn) of the body (K) to the rest position of the vat base in the extent of at least the thickness of the layer (Kn+1) of the body (K), which layer is to be newly formed, whilst at the same time as the movement of the height-adjustable building platform the substance (S) which can be hardened by radiation is hardened selectively by means of the radiation source by irradiation to form the new layer (Kn+1) of the body (K).
31. Method according to claim 18, wherein an inhibitor medium (Mi) is supplied via the chamber to the substance (S) which can be hardened by radiation and the height-adjustable building platform with a last-hardened layer (Kn) of the body (K), which layer adheres to the building platform, is moved into a height (Zx+1) above the rest position of the vat base which height defines a distance between the last-hardened layer (Kn) of the body (K) to the rest position of the vat base in the extent of at least the thickness of the layer (Kn+1) of the body (K), which layer is to be newly formed, and then the substance (S) which can be hardened by radiation is hardened selectively by means of the radiation source by irradiation to form the new layer (Kn+1) of the body (K).
Description
[0052] The invention will be explained in further detail hereinafter with reference to preferred, non-restrictive exemplary embodiments with reference to the drawings. In the figures:
[0053] FIG. 1 shows a device according to the invention with a pressure sensor and a vat base without carrier plate;
[0054] FIG. 2 shows a device according to the invention with a pressure sensor and a vat base with carrier plate;
[0055] FIG. 3 shows a carrier plate with elevations resting on the vat base;
[0056] FIG. 4 shows the device from FIG. 1 with an at least partially formed body adhering to the vat base;
[0057] FIG. 5 shows the device from FIG. 2 with an at least partially formed body adhering to the vat base;
[0058] FIGS. 6a to 6d show the device from FIG. 2 in each case with an adjustable pressure source, an adjustable heating device, an adjustable process substance source (inhibitor source) and an air flow source;
[0059] FIG. 7 shows the device from FIG. 1 with an inhibiting layer;
[0060] FIG. 8 shows the device from FIG. 2 with an inhibiting layer;
[0061] FIG. 9 shows the device from FIG. 7 with a partially depleted inhibiting layer;
[0062] FIG. 10 shows the device from FIG. 9 with an even more severely depleted inhibiting layer;
[0063] FIG. 11 shows the device from FIG. 8 with a partially depleted inhibiting layer;
[0064] FIG. 12 shows a device according to the invention in which the vat base is an openable, in particular removable cover of a chamber housing of the chamber;
[0065] FIG. 13 shows the device from FIG. 1 with a doctor blade on the vat base;
[0066] FIG. 14 shows the device from FIG. 1 with a building platform touching the vat base;
[0067] FIG. 15 shows the device from FIG. 1 with a negative pressure in the chamber which deflects the vat base away from the building platform;
[0068] FIG. 16 shows the device from FIG. 2 with an excess pressure in the chamber which deflects the vat base towards the building platform;
[0069] FIG. 17 shows the device from FIG. 1 with a body incorrectly released partially from the building platform;
[0070] FIGS. 18a to 18c shows a release process of the last-hardened layer of the body from the vat base in three exemplary states;
[0071] FIG. 19 shows diagrams with exemplary behaviours (courses) of the volume of the chamber, the pressure in the chamber and the height of the building platform above the vat base for the release process shown in FIGS. 18a to 18c in the case of a substantially closed chamber;
[0072] FIGS. 20a and 20b show a release process of the last-hardened layer of one of three bodies from the vat base in two exemplary states;
[0073] FIG. 21 shows diagrams with exemplary behaviours (courses) of the pressure in a substantially closed chamber and the height of the building platform above the vat base for the release process shown in FIGS. 20a and 20b;
[0074] FIG. 22 shows a body adhering to the vat base;
[0075] FIGS. 23a to 23c show diagrams with exemplary behaviours (courses) of the height of the building platform above the vat base and with the exposure time; and
[0076] FIG. 24 shows a device according to the invention with a flow sensor instead of a pressure sensor.
[0077] In the depicted figures, parts of the device which do not serve the description of the respective figure are omitted for the sake of clarity.
[0078] Those parts of the description which relate to a pressure measurement or detection of the pressure in the chamber should be understood under the condition that the sensor is a pressure sensor and the chamber is substantially closed. For explanations relating to the tightness of the substantially closed chamber, reference is made to the preceding description.
[0079] For the sake of clarity, most exemplary embodiments are shown and described in connection with a substantially closed chamber and a pressure sensor. If instead of a pressure measurement, a measurement of the flow of a quantity of substance is intended and possible, a flow sensor which is arranged in an inlet/outlet of the chamber for a fluid can naturally be used instead of the pressure sensor. Accordingly, those exemplary embodiments which are certainly shown and described in connection with a pressure sensor, which can however also be implemented in connection with a flow sensor, are valid for designs using a flow sensor as well.
[0080] FIG. 1 shows a device 1 for a system for layer-by-layer construction of a body K which is shown, for example, in FIG. 4 from a substance S which can be hardened by radiation, comprising a vat 3 having a vat base 2 for receiving the substance S which can be hardened by radiation. The vat base 2 is shown in its rest position, substantially flat. The device 1 also comprises a height-adjustable building platform 4, which is height-adjustable in relation to the vat base 2 and which is arranged above the vat base 2, and a sensor 5 cooperating with the vat base 2. The height-adjustable building platform 4 is adjustable in the direction indicated by the double arrow H, i.e. in the height, upwards and downwards in relation to the vat base 2 or generally in relation to the vat 3. The vat base 2 is configured to be flexible, at least partially in a subregion 13. A chamber 6 which is closed in FIG. 1 is provided below the vat 3 in order to cooperate with a sensor 5 configured as pressure sensor 5a. In another embodiment shown in FIG. 24, the chamber 6 can comprise an opening 34 for the inlet or outlet of a fluid received in the chamber 6, wherein the sensor 5 is then a flow sensor 5b. The chamber 6 is delimited from an underside of the vat base 2. Thus, the vat base 2 is a part of a chamber housing 7 of the chamber 6. The sensor 5 can detect a volume change of the chamber 6 and provide a sensor signal from which a sign of the volume change can be determined. The sensor 5 can in particular quantitatively detect a measured variable directly or indirectly proportional to the volume of the chamber or to the volume change of the chamber and provide the measured variable as sensor signal. In the example shown in FIG. 1, the sensor 5 is a pressure sensor 5a for detecting a pressure or a pressure change corresponding to the volume change of a compressible medium M received in the chamber 6. The chamber 6 is in this case configured to be closed. In another embodiment (FIG. 24) the sensor 5 can be a flow sensor 5b which is provided to detect a change in the amount of substance of the amount of substance contained in the chamber 6 of a fluid received in the chamber 6, wherein the change in the amount of substance corresponds to the volume change. The fluid can be a liquid or a gas and accordingly compressible or incompressible. For example, the sensor 5 is adapted to provide a detected pressure, a detected pressure change or a detected change in the amount of substance as a measured variable and sensor signal.
[0081] In the example shown in FIG. 1, a compressible medium M, for example, air is received in the chamber 6, wherein the sensor 5 is a pressure sensor 5a which is adapted to detect the pressure of the compressible medium M received in the chamber 6. Preferably the pressure sensor 5a is received in the chamber 6. In a special embodiment the pressure sensor 5a can also be configured as a sound transducer. The sensor 5 can be connected to a processing unit 8 which is adapted to process the sensor signal provided by the sensor 5, in particular the pressure detected by the pressure sensor 5a or the change in the amount of substance detected by the flow sensor 5b. The sensor 5 can be connected via the processing unit 8 to a drive unit 9 for the height-adjustable building platform 4 and/or to a control unit 10 for a radiation source 11 which is provided for irradiating the substance S which can be hardened by radiation. The processing unit 8 is adapted to control the drive unit 9 for the height-adjustable building platform 4 and/or the control unit 10 for the radiation source 11 depending on the sensor signal provided by the sensor 5. In other exemplary embodiments not shown, the processing unit 8 can also be connected only to the drive unit 9 for the height-adjustable building platform 4 or only to the control unit 10 for the radiation source 11 and be configured for the control thereof. The separating force required to separate the body K from the vat base 2, and which is introduced through the height-adjustable building platform 4 deflects the vat base 2 and thereby produces a volume change in the chamber 6. If the chamber 6 is closed for use with a pressure sensor 5a, the volume change brings about a pressure change in the chamber 6. If, on the other hand, the chamber 6 is partially open for use with a flow sensor 5b, the volume change brings about a flow (an inflow or outflow) of the fluid received in the chamber 6 for pressure equalization with the surroundings or with another chamber. With increasing radiation energy (product of exposure time and exposure intensity), which is introduced by the radiation source 11, the generated layer of the body K adheres more strongly to the vat base 2. An excessive exposure energy can be determined by comparing the predicted minimal pressure (=separation pressure) or flow with the actual separation pressure or flow. The drive unit 9 can, for example, comprise a controllable electric motor, in particular a step motor, which is in engagement with a height-adjustable rod 12 and is connected to the building platform 4 via the rod 12. The vat base 2 is at least partially permeable to radiation, i.e. at least partially permeable for the radiation emitted by the radiation source 11 onto the vat base 2, for example, light. Preferably the vat base 2 comprises a flexible tensioned foil 13a. The foil 13a is provided in the flexible subregion 13. Favourably the foil 13a is configured to be at least partially permeable to radiation, in particular permeable to light. In the example shown in FIG. 1, the foil 13a is tensioned between fixed edge parts 14 of the vat base 2. If, as in the example shown in FIG. 1, the radiation source 11 is arranged outside, in particular below the chamber 6, the chamber base 7a of the chamber housing 7 is expediently configured to be at least partially permeable to radiation, in particular permeable to light. An exemplary radiation cone B can be identified in FIG. 1.
[0082] FIG. 2 shows the device 1, wherein at least a part of the vat base 2, in particular the flexible subregion 13, particularly preferably the foil 13a, rests on a carrier plate 15 which is at least partially permeable to radiation, in particular transparent. In the depicted rest position the carrier plate 15 thus supports an underside of the foil 13a. The foil 13a or the vat base 2 is shown substantially flat in this rest position. The carrier plate 15 can be configured to be permeable for a process medium Mp, in particular an inhibitor medium Mi and/or comprise elevations 16 resting on the vat base 2 for the passage of a process medium Mp, in particular inhibitor medium Mi, between the elevations 16. The elevations 16 resting on the vat base 2 can in particular rest on the flexible subregion 13 of the vat base 2, preferably on the foil 13a. The process medium Mp or inhibitor medium Mi, for example, oxygen, is received in the chamber 6.
[0083] If a closed vat construction enables a negative volume change of the chamber 6, e.g. due to a slight sagging of the vat 3, more precisely of the vat base 2, an increase in the pressure can be detected. As a result, for example, the fill level of the hardenable, e.g. photosensitive substance S in the vat 3 can be deduced. Furthermore, the zero position of the vat base 2 relative to the carrier plate 15 can be measured, since a specific collision of the carrier plate 15 with the flexible vat base 2 after its separation from a body K results in a measurable pressure gradient.
[0084] FIG. 3 shows a section of a carrier plate 15 with elevations 16 which rest on the vat base 2. Between the elevations 16 there extend recesses 17 in which the process medium Mp, for example, the inhibitor medium Mi can flow. The recesses 17 can, for example, be formed as groove-shaped indentations between strip-shaped elevations 16. If the carrier plate 15 is additionally configured to be permeable for the process medium Mp, in particular inhibitor medium Mi, channels, not shown, can be provided in the carrier plate 15 for conducting the process medium Mp, in particular inhibitor medium Mi. The carrier plate 15 can also be configured to be porous.
[0085] FIG. 4 shows the device 1 with an at least partially formed body K. The body K comprises a plurality of layers K1 to Kn which were formed by local hardening of the hardenable substance S with radiation. The body K adheres with the layer K1 formed as the first layer on the building platform 4 and—in the situation depicted before release—with the last formed layer Kn on the vat base 2, in particular on the foil 13a. In the depicted state the building platform 4 has already been moved a small distance upwards, i.e. in the positive z direction and away from the vat 3, with the result that the foil 13 is deflected from its rest position at least in a subregion. As a result of the deflection, the volume of the chamber 6 is enlarged. This corresponds to a positive sign (“+”) of the volume change. Consequently (at constant temperature and constant amount of substance, i.e. closed chamber), the pressure in the chamber 6 decreases. The pressure sensor 5a is adapted to detect this pressure change and transmit a corresponding signal to the processing unit 8. Likewise, a flow sensor 5b cooperating with a partially open chamber 6 (not shown in FIG. 4) can detect a change in the amount of substance in the chamber 6, which change in the amount of substance corresponds with the increase in the volume of the chamber 6. In particular, in the case of the open chamber 6 fluid is sucked into the chamber 6 due to the deflection of the foil 13a. The flow sensor 5b can also transmit a corresponding signal to the processing unit 8. For the sake of clarity, in FIG. 4 and in subsequent figures, the processing unit 8, the drive unit 9 and the control unit 10 are not shown.
[0086] Unlike FIG. 4, a carrier plate 15 is provided in FIG. 5 on which the vat base 2, in particular the foil 13a can rest. As can be seen in the depicted situation with deflected vat base 2, the vat base 2, more precisely the foil 13a, rests only loosely on the carrier plate 15 and can be raised therefrom under the action of an adhering body K. As a result of the indentations 17 in the carrier plate 15, a pressure equalization can take place inside the chamber 6, i.e. between the space between carrier plate 15 and foil 13a on the one hand and the chamber 6 underneath the carrier plate 15 on the other hand. The deflection of the vat base 2 thus results in a pressure change which can be detected by the pressure sensor 5a or a change in the amount of substance which can be detected by the flow sensor 5b. Also in FIG. 5 instead of the pressure sensor 5a in the closed chamber 6, a flow sensor 5b can be provided in a partially open chamber 6 (not shown in FIG. 5).
[0087] FIG. 6a shows in simplified form the device 1 in which the chamber 6 as closed chamber 6 is connected, for example, to at least one adjustable pressure source 18 for setting a resting pressure in the chamber 6 and the pressure sensor 5a is connected via the processing unit 8 to the adjustable pressure source 18.
[0088] FIG. 6b shows the device 1 in which the chamber 6, for example, is connected to an adjustable heating device 19 (or generally to a heat exchanger) to set a temperature in the chamber 6 and the pressure sensor 5a is connected via the processing unit 8 to the adjustable heating device 19. In this example, the chamber 6 comprises an inlet 27 and an outlet 28. The inlet 27 and the outlet 28 can each be closed by a valve 29, 30, in particular a magnetic valve in each case. The heating device 19 is arranged in a supply line 31 between a compressor 32 and the valve 29 upstream of the inlet 27. In order to change the temperature in the chamber 6, the compressor 32 can be activated at least temporarily in order to suck, e.g. ambient air through the orifice 33. At the same time, the valves 29, 30 are opened to approximately the same extent so that compressible medium can emerge from the chamber 6 through the outlet 28 and be replaced by the compressible medium flowing subsequently through the inlet 27, wherein the after-flowing medium has been heated immediately previously in the heating device 19. As a result of the mixing of the compressible medium in the chamber 6, a uniform temperature is rapidly established as a result of the flow. In this case, it can be favourable if a device is provided for measuring the temperature in the chamber 6 and is optionally connected to the processing unit 8. The heating device 19 is therefore used, for example, for indirect heating of the hardenable substance S. As soon as a desired temperature is reached, the valves 29, 30 are closed again. When evaluating the pressure changes detected by the pressure sensor 5a, the state of the valves 29, 30 (i.e. closed or open or partially open) is taken into account to be able to correctly assign the cause for the pressure changes.
[0089] FIG. 6c shows in simplified form the device 1 in which the chamber 6 is connected, for example, to an adjustable process substance source 20, in particular inhibitor source 20a, for the adjustable supply of a process medium Mp, in particular inhibitor medium Mi, into the chamber 6 and the pressure sensor 5a is connected via the processing unit 8 to the adjustable process substance source 20, in particular inhibitor source 20a. The process substance source 20 is used for at least local manipulation of the solidification process of the substance S which can be hardened by radiation in the vat 3. Since in this case, the vat base 2 can be at least slightly permeable for the process medium Mp, this variant can manage only with an inlet and without an outlet. If the sensor 5 is designed as a flow sensor 5b, it can be arranged in a connecting line between the process substance source 20 and the chamber 6. In this case, the volume change is concluded by means of mass balance; this is proportional to the difference between inflowing and outflowing medium.
[0090] FIG. 6d shows in simplified form the device 1 in which the chamber 6 is connected, for example, to an air flow source 21 to produce an air flow in the chamber 6 and the pressure sensor 5a is connected via the processing unit 8 to the air flow source 21. The air flow source 21 is used, for example, for mixing the compressible medium M received in the chamber 6. As in FIG. 6c, a flow sensor 5b arranged in a connecting line between the air flow source 21 and the chamber 6 can also be used as sensor 5.
[0091] Naturally the chamber 6 of the device 1 can be connected to a plurality of the adjustable pressure source 18 the adjustable heating device 19, the adjustable process substance source 20 and the air flow source 21. The processing unit 8 is preferably adapted to control the pressure source 18 and/or the heating device 19 and/or the process substance source 20 and/or the air flow source 21 depending on the sensor signal provided by the sensor 5. Furthermore, the processing unit 8 can preferably be adapted to control one or more members of the group consisting of inlet valve 29, outlet valve 30 and compressor 32.
[0092] FIG. 7 shows the device 1 with an inhibiting layer I formed by the inhibitor medium Mi. The inhibiting layer I is formed in the depicted example between the vat base 2 and the hardenable substance S. For this purpose the inhibitor medium Mi is introduced through an access (not shown in FIG. 7) into the chamber 6. In order to be able to supply the inhibitor medium Mi to the hardenable substance S, the vat base 2, in particular the foil 13a is preferably configured to be semi-permeable, for the inhibitor medium Mi or generally permeable for a process medium Mp. The inhibitor medium Mi or the inhibiting layer I formed thereby reduces the adhesive force by means of which the last formed layer Kn of the body K adheres to the vat base 2, in particular to the foil 13a. Preferably the inhibitor medium Mi or the inhibiting layer I prevents such an adhesion. The example shown in FIG. 7 can also be implemented with a flow sensor 5b in a partially open chamber 6 instead of the pressure sensor 5a in the closed chamber 6. In this case, the delta of the inflowing and outflowing medium corresponds to the volume change.
[0093] A temperature control of the chamber 6 is used, for example, to accelerate the diffusion process of the inhibitor medium Mi through the semi-permeable layer (foil 13a) but also the heating of the hardenable substance S in the vat 3. The temperature in the chamber 6 influences the temperature of the substance S and therefore the viscosity and the reactivity of the hardenable substance S to radiation.
[0094] Unlike FIG. 7, in FIG. 8 a carrier plate 15 is provided on which the vat base 2, in particular the foil 13a, can rest. In this case, it is expedient if the carrier plate 15 is configured to be permeable for the inhibitor medium Mi or generally a process medium Mp and/or comprises elevations 16 resting on the vat base 2 for passage of the inhibitor medium Mi or process medium Mp between the elevations 16.
[0095] FIG. 9 shows the device 1 in which the inhibiting layer I underneath the body K is partially depleted. This is indicated by the upwards curvature of the foil 13a and therefore by the thinner configuration of the inhibiting layer I underneath the body K.
[0096] In the example shown in FIG. 10, the inhibiting layer I is completely depleted underneath the body K which is why the last-formed layer Kn of the body K adheres to the vat base 2, in particular to the foil 13a, in an undesirable manner.
[0097] The situations according to FIG. 9 and FIG. 10 can be distinguished by the different deflections of the foil 13a and the resulting different changes in the volume by means of the volume change detected by the sensor 5. If the sensor 5 is a pressure sensor 5a cooperating with a closed chamber 6, the different changes of the pressure in the chamber 6 can be distinguished by means of the pressure change detected by the pressure sensor 5a. The processing unit 8 can therefore signal, for example, a deficiency of inhibitor medium Mi or preferably independently provide for a timely replenishment or distribution of the inhibitor medium Mi into/in the chamber 6, e.g. by controlling a corresponding inhibitor source 20. Unlike FIG. 9, a carrier plate 15 is provided in FIG. 11, on which the vat base 2, in particular the foil 13a can rest. As a result of the elevations 16 and indentations 17, the carrier plate 15 does not make any change to the fundamental operating mode as described above with regard to the distribution of the inhibitor medium Mi.
[0098] FIG. 12 shows the device 1 in an embodiment in which the vat base 2 is an openable, in particular removable cover 22 of the chamber housing 7 of the chamber 6. In this variant the chamber 6 is only closed by incorporation of the vat 3 into the system. In this case, the chamber housing 7 consists of a chamber base 7a, side parts 7b and a chamber upper part 7c. The vat base 2 as cover 22 of the chamber housing 7 can form the chamber upper part 7c and the side parts 7b as in the example shown in FIG. 12. Thus, the cover 22 is placed on the chamber base 7a which is formed by a support surface of the system. The support surface forming the chamber base 7a is here at the same time part of the machine housing of a production machine. In another embodiment, the cover 22 can only form the chamber upper part 7c and is placed on the side parts 7b and on the chamber base 7a. Alternatively to the closed chamber 6 shown as an example in FIG. 12, the chamber 6 can be configured to be partially open in order to cooperate with a flow sensor 5b.
[0099] FIG. 13 shows the device 1 with a movable doctor blade 23 in the vat 3 on the vat base 2, in particular on the foil 13a. Preferably the sensor 5, i.e. the pressure sensor 5a or the flow sensor 5b is connected via the processing unit 8 to a drive unit 24 of the doctor blade 23. In the example shown in FIG. 13, the drive unit 24 of the doctor blade 23 is a rod 25 received displaceably in the vat 3 which rod 25 is moved by a motor 26 controlled by the processing unit 8. The processing unit 8 is, for example, adapted to control the drive unit 24 (motor 26) of the doctor blade 23 depending on the sensor signal detected by the sensor 5, i.e. the pressure in the chamber 6 detected by the pressure sensor 5a or the change in the amount of substance in the chamber 6 detected by the flow sensor 5b.
[0100] FIG. 14 shows the device 1 in a state in which the building platform 4 lowered in the negative z-direction touches the vat base 2, in particular the foil 13a. Touching is understood to be a contact of the vat base 2 or the foil 13a by the building platform 4 or by the last-hardened layer Kn of the body K without significant deflection or with minimal deflection of the vat base 2 or the foil 13a. Any further lowering of the building platform 4 would result in a volume change in the chamber 6 (i.e. a reduction in the volume and a resulting increase in the pressure in a closed chamber 6 or a resulting reduction in the amount of the fluid in the partially open chamber 6) which can be measured by the sensor 5 (pressure sensor 5a or flow sensor 5b).
[0101] FIG. 15 shows the device 1 in a state in which a negative pressure which deflects the vat base 2 away from the building platform 4 was established in the chamber 6 by the processing unit 8 for the release of a last-hardened layer Kn of the body K, which layer adheres to the vat base 2, from the vat base 2, in particular during a movement of the height-adjustable building platform 4 away from the rest position of the vat base 2. In the example shown in FIG. 15 the building platform 4 had already been moved a short distance upwards in the positive Z direction. The negative pressure in the chamber 6 is set depending on the pressure detected by the sensor 5 in particular pressure sensor 5a in the chamber 6. For this purpose, the pressure sensor 5a is connected via the processing unit 8 to a compressor 32 connected to the chamber 6. The compressor 32 can preferably be operated in both directions, i.e. to produce an excess pressure or a negative pressure in the chamber 6, as soon as the valve 29 in front of the inlet 27 is opened. The negative pressure is indicated in FIG. 15 by vertically downward-directed arrows. In order to produce the negative pressure in the chamber 6, this is configured to be closed or at least closable.
[0102] FIG. 16 shows the device 1 in a state in which before the building platform 4 or the last-hardened layer Kn of the body K touches the vat base 2, an excess pressure deflecting the vat base 2 towards the building platform 4 was established in the chamber 6 by the processing unit 8. In the example shown in FIG. 16, the building platform 4 was already moved a short distance downwards in the negative Z direction to touch the vat base 2. The setting of the excess pressure in the chamber 6 is made depending on the pressure detected by the sensor 5, in particular pressure sensor 5a, in the chamber 6. For this purpose, the pressure sensor 5a is connected via the processing unit 8 to a compressor 32 connected to the chamber 6. The excess pressure brings about an upward curvature of the foil 13a. As a result, when using a carrier plate 15, a touching can also be used in order to detect by means of the pressure sensor 5a a touch time by means of a sudden increase in pressure. In order to produce the excess pressure in the chamber 6, this is configured to be closed or at least closable.
[0103] At the beginning of the production of a body K, the building platform 4 is lowered so far that it is located in the region of a layer thickness (preferably 10 μm-300 μm) above the vat base 2. The subsequent exposure of the first layer K1 of the body K to be produced is usually carried out with increased energy input in order to ensure a secure adhesion of the layer K1 to the building platform 4. Due to, for example, the accuracy of the height positioning of the building platform 4, the ageing of the vat and due to differences in the vat production, the distance between the building platform 4 and the vat base 2 can vary so that the adhesion of the first layer K1 cannot always be guaranteed. An active touching of the vat base by the building platform 4 shown in FIG. 16 is therefore appropriate and prevents the problems listed above. For this purpose, the pressure in the chamber 6 is increased by means of the compressor 32 or a pressure source 18 (see FIG. 6a) so that a slight convex curvature of the vat base 2, as in FIG. 16, is produced. The building platform 4 then moves in the direction of the vat base 2, i.e. downwards. As soon as the building platform 4 touches the curved vat base 2, the pressure in the chamber 6 increases further. The building platform 4 can be moved further in the direction of the vat base 2 until the pressure no longer varies, then the vat base 2 rests on the carrier plate 15 and is pressed flat. A further movement in the negative Z direction results, for example, in a step loss in the step motor or in damage to the vat 3.
[0104] FIG. 17 shows an error case in which a body K has undesirably become partially released from the building platform 4. Such an error case can be detected with the sensor 5 (pressure sensor 5a or flow sensor 5b) since a further movement of the building platform 4 downwards in the negative Z direction results in a premature reduction in volume (pressure increase or reduction in the amount of substance) in the chamber 6. The prematureness of the volume reduction can be determined and identified from the predicted height of the body K on the basis of the layers K1-Kn already produced and the path of the building platform 4 notified by the step motor compared to the time of the volume reduction detected by the sensor 5.
[0105] FIGS. 18a to 18c show how the curved vat base 2 is released from the last-hardened layer Kn of the body K wherein the height of the building platform 4 is varied (Z1<Z2<Z3). In FIG. 18a the building platform 4 has already been move a short distance in the positive z direction. In FIG. 18b the building platform 4 has been moved further in the positive z direction and a partial separation has already taken place. In FIG. 18c the building platform 4 has been moved a little further in the positive z direction and the vat base 2 has been completely released from the body K at this time point and returned into its rest position. As a result, the volume of the chamber 6 has reduced which corresponds to a negative sign (“−”) of the volume change.
[0106] FIG. 19 shows time profiles of the volume of the chamber 6, of the sign of the volume change of the volume, of the pressure change in the chamber 6 resulting from the volume change, when the chamber 6 is closed, and of the z position or height of the building platform 4 in relation to the rest position of the vat base 2 during a layer generation monitored by the sensor 5, in particular pressure sensor 5a. Initially, the hardenable, for example, light-hardening substance S is hardened with a desired cross-sectional shape to form a layer Kn. Then the hardened layer Kn, which has formed between the vat base 2 and the previously generated layer Kn−1 must be separated from the vat base 2. From t.sub.start, the building platform 4 is moved from z.sub.x in the positive Z direction. As a result of the flexible design of the vat base 2, this is deformed concavely in the Z direction and the volume in the chamber 6 increases from the normal volume V.sub.norm (cf. FIG. 18a shortly thereafter). The positive volume change (sign “+” or “1”) results in a proportional pressure reduction starting from p.sub.norm, this is detected by the pressure sensor 5a. Depending on cross-sectional shape, layer thickness, material and many other factors, the generated layer Kn separates from the vat base 2 as soon as the height z.sub.sep (at the time t.sub.sep) has been reached (cf. FIG. 18c). The curved vat base 2 moves abruptly back into its planar original shape (rest position). Depending on the design and material of the vat base 2, a damped vibration can occur. The transition of the vat base 2 into the rest position results in a rapid negative volume change (sign “−” or “−1”) which results in V.sub.norm and therefore in a measurable pressure change from p.sub.sep to p.sub.norm. The release time or separation time t.sub.sep can thus, for example, be identified by means of the sign change of the volume change from “1” to “−1” during the separation process (the sign of the volume change can optionally be determined as the reverse sign of the pressure change). As a result, the separation process, i.e. the raising of the building platform 4 can be ended and the building platform moved from z.sub.sep to z.sub.x+1 (lowered). At t.sub.disp a displacement of material occurs which concavely curves the vat base 2 and reduces the volume of the chamber 6 so that the measured pressure increases. At the time tend the Z position z.sub.x+1 at which the new layer should be generated is reached. The pressure in the chamber p.sub.disp is greater than p.sub.norm. Thus, the irradiation, for example exposure is only initiated at time t.sub.next. This ensures that the material displacement which is characterized by a planar vat base 2 and a resulting chamber pressure p.sub.norm is completed. The exposure time is shown by chequered rectangles in the diagram of the Z position. Knowledge of the separation time t.sub.sep is very valuable in terms of process technology since without this a prospective separation height z.sub.sep must be assumed and this must be exposed with sufficient certainty (margin) in order to achieve a separation in each case. This has the result that the building platform 4 (without knowledge of the separation time t.sub.sep) is frequently moved further in the positive Z direction although the layer Kn has already been released from the vat base 2. In this case, several seconds per layer are moved to no avail. Usual bodies to be generated consist of more than 1000 layers so that the print job is increased appreciably without knowledge of the separation time t.sub.sep.
[0107] FIGS. 20a and 20b show a process of separation of three bodies K from the vat base 2, wherein in FIG. 20b the body K shown furthest right has already been separated from the vat base 2 and in the region underneath the body K shown furthest right the vat base 2 has returned into its rest position. By means of the volume change (pressure change or change in amount of substance) detected by the sensor 5 (pressure sensor 5a or flow sensor 5b) in the chamber 6, it can be ascertained whether individual bodies K have not yet been released.
[0108] FIG. 21 shows time profiles of the pressure change and of the Z position or height of the building platform 4 in relation to the rest position of the vat base 2 during a layer generation monitored by the sensor 5, in particular pressure sensor 5a. In this case, at time t.sub.sep1 the body K shown furthest right is released from the vat base 2, at time t.sub.sep2 the body K shown in the middle is released from the vat base 2 and at time t.sub.sep3 the body K shown furthest left is released from the vat base 2. The three local minima in the time profile of the pressure change are the release pressures p.sub.sep1, p.sub.sep2 p.sub.sep3 of the three generated bodies K. The exposure time is shown in the diagram of the Z position by chequered rectangles.
[0109] FIG. 22 shows a static force model of the separation process for a possible calculation of the desired volume change with which the actual volume changes can be compared. As a result, the generated bodies K can be assigned to the individual separation times.
[0110] Allowance is made for the pulling force F.sub.obj, the restoring force of the deflected vat base 2 F.sub.vat, the weight force of the poured-in resin as hardenable substance S ρ.sub.RV.sub.Rg, as well as the forces produced by the pressure difference in the machine space (A.sub.vat−A.sub.Obj)p.sub.atm and in the vat chamber 6 A.sub.vatp.sub.vat:
[0111] It holds that:
[00001]
[0112] The known forces are on the right-hand side of the equation through knowledge of the material properties and the fill level as well as by measurement of the pressure. Machine space can be understood as a general space in the machine, this can also be the installation space.
[0113] Since the shape and position of A.sub.obj is known, F.sub.vat can be approximately calculated/predicted with the aid of the Z height and the material properties of the foil 13a. The pulling force F.sub.obj can be concluded as a result. This influences the object quality and can result in undesired release from the building platform 4. In a control circuit it can also serve as a reference variable with the pulling speed as control variable.
[0114] Furthermore, the foil curvature due to the deflection can be calculated as a result of the known parameters. The resulting desired volume change can be compared by means of the sensor data with an actual volume change which is obtained as follows:
[0115] The change of state of the chamber is obtained from:
[00002]
[0116] Wherein it holds for the volume that V.sub.2=V.sub.1+ΔV.sub.ist, as a result the actual volume change can be calculated
[00003]
[0117] An excessive deviation between desired and actual volume (ΔV.sub.ist<ΔV.sub.soll) indicates a reduction in the stiffness of the vat whereby the ageing of the vat or the quality of the vat 3 can be assessed.
[0118] The device and the method thus make it possible to model the desired deformation of the flexible vat base 2 with the aid of the known position of the building platform 4 and the known hardening positions, e.g. in the form of an exposure matrix and to compare the resulting desired pressure change (desired volume change) with the actual pressure change (volume change). Deviations indicate inter alia a change in the stiffness of the vat whereby the ageing of the vat or the quality of the vat 3 can be assessed.
[0119] FIGS. 23a to 23c show relationships of the height adjustment of the building platform 4 with the exposure time of the hardenable substance S for three process sequences. The exposure time is shown by chequered rectangles in the diagrams.
[0120] FIG. 23a shows in particular a process in which the exposure of the hardenable substance S is carried without using an inhibiting layer I separate from the movement of the building platform 4 (asynchronous mode without inhibiting layer I). In this case, the building platform 4 moves upwards in the positive Z direction to separate the generated layer from the vat base 2. As a result of the measured values of the sensor 5 (pressure sensor 5a or flow sensor 5b), the separation of the generated layer from the vat base 2 is identified and the raising of the building platform 4 is ended. The building platform 4 is lowered again and after a displacement waiting time the next layer is exposed. The measured values of the sensor 5 (pressure sensor 5a or flow sensor 5b) are used in the asynchronous process with vat 3 without inhibiting layer I to identify the release time and to set the pulling speed by maximum permissible volume change per time unit.
[0121] FIG. 23b shows in particular a process in which the exposure of the hardenable substance S and the movement of the building platform 4 upwards by the height of a layer thickness take place simultaneously (synchronous mode with inhibiting layer I). The pressure sensor 5a and the flow sensor 5b can be used here to monitor the fill level of the vat 2 and/or the depletion of the inhibiting layer and thus enable a suitable control of the pressure in the chamber 6, a supply of inhibitor medium into the chamber 6 and an adaption of the temperature in the chamber 6.
[0122] FIG. 23c shows in particular a process in which the exposure of the hardenable substance S takes place after the movement of the building platform 4 upwards by the height of a layer thickness using an inhibiting layer I (asynchronous mode with inhibiting layer I).
[0123] FIG. 24 shows a device 1 according to the invention similar to the device 1 from FIG. 1 wherein unlike the device 1 from FIG. 1 instead of the pressure sensor 5a which cooperates with a closed chamber 6, a flow sensor 5b is provided which cooperates with a partially open chamber 6. The partially open chamber 6 comprises an opening 34 serving as an inlet and an outlet for fluid. Thus, in the case of a volume change of the chamber 6, the fluid enclosed or contained in the chamber 6 can flow in or flow out through the opening 34. This fluid flow through the opening 34 is detected by the flow sensor 5b. The person skilled in the art will understand that in some exemplary embodiments shown in the figures, in particular depending on the process steps carried out by the device 1, the closed chamber 6 with the pressure sensor 5a can be replaced by a partially open chamber 6 with the flow sensor 5b.
