A schlieren system for in-situ/online monitoring of a spatter in a large-area melt pool, wherein the schlieren system is configured to monitor spatter phenomena in the large-area melt pool on a selective laser melting build workbench, the selective laser melting build workbench comprising a powder reservoir (4), a build platform (5), and a powder collection bin (7) arranged in sequence on a bottom surface (12a) of a printing chamber (12) in a powder scraping direction y, as well as a laser emitter (13) arranged above the build platform (5), the laser emitter (13) is configured to be controlled by a laser galvanometer motor controller (22), and to project an emitted laser beam (21) onto a designated position area of the build platform (5) according to laser scanning path information outputted from a laser path planner (23), and to scan along a laser scanning path;
- and the schlieren system comprising an optical source for generating an initial optical beam (19c), and an optical beam guiding system comprising a plane mirror designated as a fifth plane mirror (9), an optical path deflecting mirror (17), and a reflector group;
- wherein
- the fifth plane mirror (9) is configured to guide any of guiding optical beams (19a) reflected by the reflector group, and after the any of the guiding optical beams reflected by the reflector group has been reflected by the fifth plane mirror (9), schlieren optical beams (19b) are formed, wherein the schlieren optical beams pass through a sputtering area in close proximity to an upper surface of the build platform (5) in a left-right direction x and reach a sixth plane mirror (6), wherein the left-right direction x is perpendicular to the powder scraping direction y and parallel to the bottom surface;
- a projection length of the fifth plane mirror (9) in the powder scraping direction y is denoted as L1, wherein L1 is greater than or equal to a length L2 of the sputtering area in the powder scraping direction y;
- the sixth plane mirror (6) is configured to guide the schlieren optical beams (19b) to be reflected to a lens group (3) and focus on a camera (2), a projection length L3 of the sixth plane mirror (6) in the powder scraping direction y is greater than or equal to L2, and the fifth plane mirror (9) and the sixth plane mirror (6) are respectively arranged on a left/right side of the build platform (5) in the left-right direction x;
- the reflector group comprises at least two reflectors configured to pivot to change directions of the at least two reflectors, the at least two reflectors are arranged on a mounting plane, and mirror surfaces of the at least two reflectors are configured to pivot around pivot axes perpendicular to the mounting plane;
- the at least two reflectors, the optical path deflecting mirror (17), and the fifth plane mirror (9) are arranged on an identical side of the build platform (5), and when the at least two reflectors are pivoted to a guiding angle, the mirror surfaces of the at least two reflectors face the optical path deflecting mirror (17) and direct reflected optical beams toward the fifth plane mirror (9), and the guiding optical beams (19a) reflected by the at least two reflectors to the fifth plane mirror (9) are parallel;
- the optical path deflecting mirror (17) is configured to be pivotable around an axis (18) perpendicular to the mounting plane to a working position relatively parallel to one of the at least two reflectors in the reflector group, wherein the one of the at least two reflectors in the reflector group has been pivoted to the guiding angle, wherein the initial optical beam (19c) is reflected to the one of the at least two reflectors in the reflector group, and a projection distance from the axis (18) of the optical path deflecting mirror (17) to the build platform (5) in a direction of the any of the guiding optical beams (19a) is less than or equal to a projection distance from a pivot axis of any of the at least two reflectors to the build platform (5);
- and
- a synchronous controller (24), wherein the synchronous controller (24) is in a signal connection with the laser path planner (23);
- after receiving the laser scanning path information, the synchronous controller synchronously sends the laser scanning path information to the laser galvanometer motor controller (22) and an optical path deflecting mirror galvanometer motor controller (25), and the optical path deflecting mirror galvanometer motor controller (25) being configured to pivot a mirror surface of the optical path deflecting mirror (17) to the working position, wherein the any of the guiding optical beams (19a) reflected by the at least two reflectors is reflected by the fifth plane mirror (9) and passes through the designated position area, wherein the at least two reflectors are pivoted to the guiding angle;
- wherein
- the at least two reflectors are arranged in a following manner according to a position of the mounting plane:
- the mounting plane is a side wall (12b) of the printing chamber (12) on a left or right side adjacent to the fifth plane mirror (9) in the powder scraping direction y, the side wall is parallel to the powder scraping direction y and forms an inclination angle greater than 0° but less than 180° with the bottom surface (12a), wherein the guiding angle is an angle αI of the mirror surface of each of the at least two reflectors pivoted to the powder scraping direction y, wherein the angle αI is greater than 0° but less than or equal to 45°;
- and an order of the guiding angles of the mirror surfaces of the at least two reflectors is opposite to an order of projection distances from the pivot axes of the at least two reflectors along the guiding optical beams (19a) to the bottom surface;
- a projection length of a union set of the guiding optical beams (19a) in the powder scraping direction y is greater than or equal to L1;
- when observing in the powder scraping direction y, projection distances from the pivot axes of the at least two reflectors to an extension surface of the powder collection bin (7) in the left-right direction x are less than projection distances from the axis (18) to the extension surface of the powder collection bin (7) in the left-right direction x;
- when observing in the direction of the any of the guiding optical beams, projection distances from the pivot axes of the at least two reflectors to the build platform (5) are greater than or equal to the projection distance from the axis (18) of the optical path deflecting mirror (17) to the build platform (5), a mirror surface of the fifth plane mirror (9) is parallel to the powder scraping direction y, and the guiding optical beams (19a) and the schlieren optical beams (19b) are symmetrical relative to a normal vector of the mirror surface of the fifth plane mirror (9);
- and
- the mounting plane is the bottom surface, the mirror surface of the fifth plane mirror (9) is perpendicular to the bottom surface, and the guiding optical beams (19a) and the schlieren optical beams (19b) are symmetrical relative to the normal vector of the mirror surface of the fifth plane mirror (9), and the direction of the any of the guiding optical beams is identical to the powder scraping direction y, the guiding angle is an angle αII of a mirror surface of each of the at least two reflectors pivoted to the left-right direction x, wherein the angle αII is greater than 0° but less than or equal to 45°;
- an order of the guiding angles of the mirror surfaces of the at least two reflectors is opposite to an order of projection distances from the pivot axes of the at least two reflectors along the guiding optical beams (19a) to an extension body of the build platform (5) in the left-right direction x, and a projection length of a union set of the guiding optical beams (19a) onto the fifth plane mirror (9) in the left-right direction x is greater than or equal to a projection length L4 of the fifth plane mirror (9) in the left-right direction x;
- in the direction of the any of the guiding optical beams, a projection distance from the extension body of the build platform (5) in the left-right direction x to the pivot axes of the at least two reflectors is greater than or equal to a projection distance from the extension body of the build platform (5) in the left-right direction x to the axis (18) of the optical path deflecting mirror (17);
- when being observed in the left-right direction x, an extension part of the build platform in the powder scraping direction y on the bottom surface is farther away from the reflector group, but the extension part of the build platform (5) in the powder scraping direction y on the bottom surface is more adjacent to the axis (18) of the optical path deflecting mirror (17);
- or when being observed in the left-right direction x, the extension part of the build platform in the powder scraping direction y on the bottom surface is more adjacent to the reflector group, but the extension part of the build platform (5) in the powder scraping direction y on the bottom surface is farther away from the axis (18) of the optical path deflecting mirror (17);
- the optical path deflecting mirror galvanometer motor controller (25) is configured to control a selected one of the at least two reflectors in the reflector group, when being pivoted to the guiding angle, the selected reflector is configured so that the guiding optical beams (19a) after being reflected by the fifth plane mirror (9) are directed to pass through the designated position area corresponding to the laser scanning path;
- the optical path deflecting mirror galvanometer motor controller (25) controls the selected reflector to be pivoted to the guiding angle, and sends a motor rotation instruction according to a difference between a complementary angle of a guiding angle of the selected reflector and an angle of the mirror surface of the optical path deflecting mirror (17) relative to a direction of the any of the guiding optical beams, wherein the optical path deflecting mirror (17) is pivoted to be parallel to a mirror surface of the selected reflector being pivoted to the guiding angle.