Additive manufacturing apparatus and method
This invention concerns a laser solidification apparatus for building objects by layerwise solidification of powder material. The apparatus including a build chamber containing a build platform, a device for depositing layers of powder material on to the build platform, an optical unit for directing a laser beam to selectively solidify areas of each powder layer and a spectrometer for detecting characteristic radiation emitted by plasma formed during solidification of the powder by the laser beam. The invention also relates to a spectrometer for detecting characteristic radiation generated by interaction of the metal with the or a further laser beam. The spectra recorded using the spectrometer may be used for feedback control during the solidification process.
1. A method of calibrating a selective laser solidification apparatus comprising a build chamber containing a build platform, a device for depositing layers of powder material on to the build platform, and an optical scanner comprising an optical train for directing a laser beam to selectively solidify areas of each powder layer and a detector arranged to detect electromagnetic radiation collected through the optical train, the method comprising locating in the build chamber a calibrated artefact, the calibrated artefact having a plurality of calibration features thereon; operating the optical scanner to irradiate a plurality of locations on the calibrated artefact with the laser beam in which a field of view of the detector includes at least one of the irradiated locations and at least one calibration feature of the plurality of calibration features; using the detector to capture an effect of the irradiation of the calibrated artefact with the laser beam; and determining an offset of the laser beam from a desired position from signals generated by the detector and a known location of the at least one calibration feature.
2. The method according to claim 1 , wherein the calibration feature comprises a three-dimensional geometrical feature having varying height in a direction perpendicular to a plane of the layers when the calibration artefact is located in the build chamber.
3. The method according to claim 1 , wherein the known location is a known location relative to other ones of the calibration features.
4. The method according to claim 1 , comprising generating an image of the calibration artefact from signals from the detector.
5. The method according to claim 4 , where the detector is a camera.
6. The method according to claim 1 , wherein the calibration artefact is located on the build platform.
7. The method according to claim 1 , comprising locating the calibration artefact in the build chamber such that the calibration artefact remains in place in the build chamber during a build of an object and the irradiation of the calibrated artefact with the laser beam is carried out during the build.
8. The method according to claim 1 , comprising altering a programmed control of the optical scanner based on the determined offset.
9. The method according claim 1 , comprising altering a programmed control of the optical scanner based on the offsets determined for each calibration feature of the plurality of calibration features of the calibration artefact.