Abstract: A method for separating and releasing a closed-form piece from a workpiece made of a brittle material is disclosed. A first pulsed laser-beam creates defects along the outline of the closed-form piece. A second laser-beam selectively heats the closed-form piece for a first time that is sufficient to initiate cracking between the defects. The heating is stopped for a period sufficiently long for the cracks to propagate completely between the defects. The second laser-beam is applied for a second time that causes melting and deformation of the closed-form piece. The deformation opens a gap between the closed-form piece and the rest of the workpiece, thereby allowing release of the closed-form piece.

Abstract: A method for separating and releasing a closed-form piece from a workpiece made of a brittle material is disclosed. A first pulsed laser-beam creates defects along the outline of the closed-form piece. A second laser-beam selectively heats the closed-form piece for a first time that is sufficient to initiate cracking between the defects. The heating is stopped for a period sufficiently long for the cracks to propagate completely between the defects. The second laser-beam is applied for a second time that causes melting and deformation of the closed-form piece. The deformation opens a gap between the closed-form piece and the rest of the workpiece, thereby allowing release of the closed-form piece.

Abstract: An apparatus for producing an object by stereolithography is provided with a tank (1) receiving a bath of liquid or powdery material which can be solidified by action of electromagnetic radiation. In known manner the apparatus comprises a support (4) for positioning the object relative to the surface (3) of the bath and a device (8) for solidifying a layer of the material (3) adjacent to the surface using electromagnetic radiation. In order to allow a precise adjustment of the layer thickness the apparatus comprises a supplying device (51) for supplying the solidifiable material (3), the supplying device extending transversely across the tank and having a discharge opening (53) at its bottom side in operational position, a channel extending in the interior thereof and communicating with the discharge opening (53), the channel being connected at one point with a pump (63) through a conduit (62).

Abstract: In a method for calibrating the deflection control of a laser beam a light-sensitive medium (5) is exposed to a laser beam (2) at predetermined positions for generating a test pattern (20), thereafter digitized partial pictures of pattern portions (21) of the test pattern (20) are produced and the digitized partial pictures are composed to a digitized overall picture of the test pattern (20). The correction data for the control (4) for deflecting the laser beam (2) are calculated on the basis of a comparison of actual positions of the laser beam (2) on the digitized overall picture with predetermined desired coordinates.

Abstract: When producing an object by subsequent solidification of material layers 1 at places corresponding to the object there is a problem of limited production speed because the scanning speed or laser power of the light beam scanning the material layer 1 cannot be increased at will, if the light beam 4 used for solidification is focused as required for exact resolution. According to the invention this problem is solved by providing a variable focusing device 8 in the light beam 4, whereby the focus of the light beam 4 can be varied during the solidification of the layer 1. Thus, a different focus, laser power and scanning speed can be used in different regions of the layer 1.

Abstract: An apparatus for producing an object using stereolithography includes a container, a bath of a liquid or powder material filling the container and having a free surface, the material being solidifiable under the action of electromagnetic radiation, a support for positioning the object relative to the free surface of the bath so as to form a layer of the material adjacent to the free surface, a device for solidifying the layer using electromagnetic radiation, a wiper device extending along a first direction across the free surface and drive means for moving the wiper device across the free surface along a second direction.