摘要：
A method of operation for an apparatus for the layer by layer manufacture of 3D objects from particulate material, the apparatus comprising a thermal sensor (72), a stationary heat source (20) positioned above a build bed surface (12) of each layer, and one or more further heat sources; wherein the method comprises a warm up process (300) followed by a build process (400), and each process comprises processing a plurality of layers, wherein each layer is processed by a layer cycle (100, 200) comprising the steps (a) to (d) of: (a) distributing a layer of particulate material by moving a distributor (32) over a build area, the layer providing the build bed surface (12) of the build area; (b) heating the build bed surface (12) using the stationary heat source (20), or a first heat source (LI) by moving the first heat source (LI) over the build bed surface (12) while operating the first heat source (LI); (c) heating the build bed surface (12) by moving the first heat source (LI), or a second heat source (L2), over the build bed surface (12) while operating it; and (d) measuring the temperature of the build bed surface (12) at least once after one or more of steps (a) to (c), using the thermal sensor (72); wherein the layer cycle comprises, during one or more of steps (a) to (c), heating the build bed surface (12) with the stationary heat source (20) to a target layer temperature (T3(target)) between the solidification temperature and the melting temperature of the particulate material; and wherein the layer cycle (200) of the build process (400) further comprises, between the steps (b) and (c) of heating, a step of: (b2) depositing absorption modifier in the form of radiation absorber over one or more layer-specific regions (50); and/or depositing absorption modifier in the form of absorption inhibitor over a surrounding area surrounding the one or more layer-specific regions (50), such that the step (c) of heating causes the layer-specific region (50) of each build layer to melt so as to form a cross section of one or more 3D objects.
权利要求：
1. A method of operation for an apparatus for the layer by layer manufacture of 3D obj ects from particulate material, the apparatus comprising a thermal sensor (72), a stationary heat source (20) positioned above a build bed surface (12) of each layer, and one or more further heat sources; wherein the method comprises a warm up process (300) followed by a build process (400), and each process comprises processing a plurality of layers, wherein each layer is processed by a layer cycle (100, 200) comprising the steps (a) to (d) of: (a) distributing a layer of particulate material by moving a distributor (32) over a build area, the layer providing the build bed surface (12) of the build area; (b) heating the build bed surface (12) using the stationary heat source (20), or a first heat source (L1) by moving the first heat source (L1) over the build bed surface (12) while operating the first heat source (L1); (c) heating the build bed surface (12) by moving the first heat source (L1), or a second heat source (L2), over the build bed surface (12) while operating it; and (d) measuring the temperature of the build bed surface (12) at least once after one or more of steps (a) to (c), using the thermal sensor (72); wherein the layer cycle comprises, during one or more of steps (a) to (c), heating the build bed surface (12) with the stationary heat source (20) to a target layer temperature (T3(target)) between the solidification temperature and the melting temperature of the particulate material; and wherein the layer cycle (200) of the build process (400) further comprises, between the steps (b) and (c) of heating, a step of: (b2) depositing absorption modifier in the form of radiation absorber over one or more layer-specific regions (50); and/or depositing absorption modifier in the form of absorption inhibitor over a surrounding area surrounding the one or more layer-specific regions (50), such that the step (c) of heating causes the layer-specific region (50) of each build layer to melt so as to form a cross section of one or more 3D objects.
2. The method of claim 1, wherein the stationary heat source (20) is operated in response to the one or more temperature measurements measured at step (d) and based on the target layer temperature (T3(target)).
3. The method of claim 1 or claim 2, wherein the stationary heat source (20) is operated continuously throughout the layer cycle (100) and wherein the step (b) of heating the build bed surface (12) is carried out by the first heat source (L1) so as to preheat the build bed surface (12) to a preheat temperature between the solidification temperature and the melting temperature of the particulate material.
4. The method of any preceding claim, wherein the step (c) of heating is carried out by the second heat source (L2).
5. The method of any preceding claim, wherein the warm up process (300) further comprises a calibration routine for a thermal control component, the thermal control component configured to contribute to control the temperature of the build bed surface (12), wherein the calibration routine is carried out over a subset of the plurality of layers and comprises the layer cycle steps of the warm up process (300), and further comprises, between the steps (b) and (c) of heating, the step of: (b2) depositing an amount of absorption modifier in the form of radiation absorber over one or more layer-specific regions (50); and/or depositing an amount of absorption modifier in the form of absorption inhibitor over a surrounding area surrounding the one or more layer-specific regions (50); wherein the step (c) of heating causes each layer-specific region (50) to heat up more than the surrounding area; and, after processing of the subset of layers, - determining a calibration outcome for the thermal control component; and - applying the calibration outcome to the thermal control component for the remaining layers of the plurality of layers.
6. The method of claim 5, wherein the thermal control component is one or more of the thermal sensor (72), the first heat source (L1), the second heat source (L2), and the stationary heat source (20), wherein the calibration routine is a corresponding one or more of: - an alignment correction routine (300_1) for the measurement position of the thermal sensor (72), wherein the thermal sensor (72) comprises an array of a plurality of individually controllable pixels to be aligned with the build bed surface (12); - a distortion correction for the measurement position and/or scale of the thermal sensor (72), wherein the thermal sensor (72) comprises an array of a plurality of individually controllable pixels to be aligned with the build bed surface (12); - a thermal calibration routine (300_3) for the measurement scale of the thermal sensor (72); - a calibration routine (300 2, 300 4) for the input power profile of the first heat source (L1); - a calibration routine (300_2, 300_4) for the input power profile of the second heat source (L2); and - a calibration routine (300_5) for the input power profile of the stationary heat source (20).
7. The method of claim 5 or claim 6, wherein the thermal control component is the thermal sensor (72), and wherein step (c) of the layer cycle of the calibration routine (300_3) for the thermal sensor (72), comprises: operating the first heat source (L1) at a fusing power input so as to cause the particulate material of the layer-specific region (50) to melt; wherein the one or more measured temperatures of step (d) of the calibration routine layers are used to determine a set point for the temperature scale of the thermal sensor (72) based on a thermal characteristic of the particulate material, and to calibrate the thermal sensor (72) to a set point, and wherein the subsequent measurements by the thermal sensor (72) in step (d) of the layer cycle (100) of the warm up process (300) are calibrated temperature measurements.
8. The method of claim 5 or claim 6, wherein the thermal control component is the thermal sensor (72), and further wherein: - the step (b2) comprises depositing an amount of radiation absorber and wherein the amount of radiation absorber is more than that deposited over the layer-specific region (50) of the preceding layer, such that, during the step (c) of heating, the amount of radiation absorber causes the particulate material of each layer-specific region (50) to absorb more energy than the layer-specific region (50) of the preceding layer; wherein the step (d) comprises measuring the temperature of the one or more layer-specific regions (50) after the step (c) of heating; - repeating steps (a) to (d) at least until the particulate material of at least one of the layer-specific regions (50) starts to melt; wherein, based on a characteristic in the layer by layer evolution of the measured temperatures, the calibration outcome is a calibrated temperature measurement scale for the temperature measurements generated by the thermal sensor (72); and wherein the calibration outcome is applied during step (d) of the layer cycle (100, 200) for the remaining layers of the plurality of layers, such that subsequent temperature measurements are calibrated temperature measurements.
9. The method of claim 7 or claim 8 when dependent on claim 2, wherein the stationary heat source (20) is operated based on calibrated temperature measurements measured at step (d) and based on the target layer temperature (T3(target)).
10. The method of any one of claims 5 to 9, wherein each layer of the calibration routine comprises a set of sublayers, wherein each sublayer is processed according to the same steps of that layer, and wherein the measured temperature at step (d) is an average temperature based on the respective temperatures measured within the layer-specific region (50) of one or more of the sublayers of that layer.
11. The method of any preceding claim, wherein the step (a) of distributing each layer is initiated after a first time interval from initiating the step (c) of heating of the previous layer, and wherein the step (c) of heating each layer is initiated after a second time interval from initiating the step (a) of distributing the layer; and wherein the first and second time interval are the same for each layer of the plurality of layers; and wherein the step (b) of heating each layer is initiated after a third time interval from initiating the step (a) of distributing the layer, and wherein the third interval is the same for each layer of the plurality of layers.
12. The method of any preceding claim, wherein the speed of moving the distributor (32) at step (a) and of moving the first heat source (L1) and, where present, the second heat source (L2) over the build bed surface (12) at steps (b) and (c) or heating is the same constant speed for each layer.
13. The method of any preceding claim, wherein the stationary heat source comprises an array of individually operable heater elements positioned above the build bed surface (12), and wherein the thermal sensor comprises an array of individual sensor pixels, wherein measuring the temperature at step (d) of the layer cycle comprises: - determining a zonal temperature for each of a plurality of zones of the build bed surface (12) as measured by a subset of the sensor pixels; and - determining a zonal temperature difference between each zonal temperature and the target layer temperature; wherein the step of heating each layer by the stationary heat source comprises heating each zone by operating one or more corresponding heater elements of the array of individually operable heating elements in response to the determined zonal temperature difference.
14. The method of any preceding claim, wherein the step (b) of heating is carried out by the first heat source (L1) and the steps (a), (b) and (c) of the warm up process (300) and the build process (400) are carried out in a first direction for each of the plurality of layers, wherein for at least the build process (400), the speed of moving the distributor (32) and of moving the first heat source (L1) and, where present, the second heat source (L2) over the build bed surface (12) is the same constant speed for each layer along the first direction; and wherein the step (a) of distributing each layer is initiated after a first time interval from initiating the step (c) of heating of the previous layer, and wherein the step (c) of heating each layer is initiated after a second time interval from initiating the step (a) of distributing the layer; and wherein the first and second time interval are the same for each layer of the plurality of layers; and wherein the step (b) of heating each layer is initiated after a third time interval from initiating the step (a) of distributing the layer, and wherein the third interval is the same for each layer of the plurality of layers.
15. The method of claim 14 when dependent on claim 11, wherein for the warm up process (300), the speed of moving the distributor (32) and of moving the first heat source (L1) and, where present, the second heat source (L2) over the build bed surface (12) is the same constant speed for each layer along the first direction and the first, second and third time intervals are the same as for the build process (400).