SLM metal 3D printer laser calibration system based on two-dimensional PSD sensor

Abstract

The invention relates to a metal 3D printer laser spot position calibration system which comprises a two-dimensional PSD sensor, an XY motion system, a high-precision grating ruler or a magnetic grating ruler and corresponding software. The PSD sensor moves along with the XY movement system and coincides with the forming plane. The grating ruler or the magnetic grating ruler is arranged on the X axis and the Y axis respectively and integrated in the 3D printer or arranged outside the printer. According to the system, through coordinate superposition conversion of the PSD sensor and the grating ruler or the magnetic grating ruler, the position of a laser spot is accurately determined, and a calibration file is generated to calibrate the printing precision.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing (3D printing), and more precisely, belongs to the field of SLM (Selected Laser Melting) metal 3D printer equipment, and solves the problem of position calibration of the laser spot. Background Art

[0002] For SLM metal 3D printers, the powder spreading plane needs to coincide with the laser working plane (usually near the focal plane). The printing accuracy is mainly determined by the positioning accuracy of the laser spot.

[0003] The current solution is to use a laser to scan a pattern of predetermined size on photo paper (usually dark paper with an adhesive backing, which is sensitive to infrared lasers), then use two-dimensional or other methods to obtain the coordinate value of the actual output pattern, compare the difference between the two, obtain the calibration coefficient through calculation, and input it into the galvanometer control system to correct the deviation.

[0004] This technology has two disadvantages: (1) It is very slow and requires outputting the graphics on photographic paper before measuring, which is particularly unfriendly to large equipment with multiple lasers; (2) The operation is complicated, there are many processes, and the accuracy is poor. Applying photographic paper and secondary measurement will lead to errors. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the existing laser calibration solutions, to achieve automation and semi-automation, and to complete all calibration work on a single system without the need for photographic paper and auxiliary measuring equipment or consumables. The core component used is a PSD sensor, also known as a position sensitive detector. A two-dimensional PSD sensor is a photoelectric device that can detect the position information of a light spot in a two-dimensional plane (usually an xy plane). It can convert the position coordinates of the light spot into an electrical signal output, and its output signal is related to the position of the light spot on the sensor surface.

[0006] The system includes:

[0007] A 2D PSD sensor, an XY motion system with a high-precision scale, and a software system.

[0008] Preferably, the two-dimensional PSD sensor can convert the light spot position (x0, y0) into a digital signal or an analog signal and transmit it to the control system.

[0009] Preferably, the two-dimensional PSD sensor is mounted on an XY motion system.

[0010] Preferably, the XY motion system comprises two motion axes: an X motion axis and a Y motion axis.

[0011] Preferably, the X-axis and the Y-axis are each equipped with a grating scale or a magnetic scale (hereinafter referred to as "scale") with an accuracy of plus or minus 3 um.

[0012] Preferably, the X scale and the Y scale indicate the position (x, y) of the PSD sensor.

[0013] Preferably, the Y motion axis can utilize the Y motion axis of the SLM metal 3D printer, and the X motion axis can utilize the powder scraper holder of the SLM metal 3D printer, thereby realizing internal deployment of the machine and achieving fully automatic calibration during the printing process.

[0014] Preferably, the X / Y motion axis, the X / Y scale, and the PSD sensor can also be placed outside the device and put into the printer when in use, and taken out after the measurement and calibration are completed, so as to save costs.

[0015] Preferably, after obtaining the coordinates (x0, y0) and (x, y), the software system obtains the precise position (X, Y) of the light spot through a superposition algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a fully automatic solution deployed in the warehouse. In the figure: 1 galvanometer, 2 main warehouse, 3 laser beam, 4Y scale, 5 printer Y axis, 6 scraper holder, 7X scale, 8X motion axis motor, 9X motion axis, 10 2D PSD sensor, 11 lower warehouse.

[0018] Figure 2 This is the deployment plan outside the warehouse. In the figure: 2.1Y motion axis motor, 2.2Y motion axis synchronous belt, 2.3Y motion axis frame, 2.4Y scale. 2.5X motion axis motor, 2.6X scale, 2.7X motion axis synchronous belt, 2.8X motion axis frame, 2.9 2D PSD sensor, 2.10-1 linear guide, 2.10-2 spacer, 2.10-3 linear guide, 2.10-4 spacer, 2.11 bottom plate.

[0019] Beneficial effects:

[0020] 1. No need to make marks on the photo paper, it is fully electrified and does not require consumables such as photo paper.

[0021] 2. No need for a secondary measurement system to test the size, reducing errors.

[0022] 3. Fast speed, can be fully automatically controlled without human intervention.

[0023] 4. The accuracy of PSD sensor and scale is 1-5um, with high overall accuracy.

[0024] 5. Can be integrated into the printer.

[0025] 6. During the printing process, you can pause to calibrate the optical path.

[0026] 7. Regardless of the printing format of the equipment, the accuracy can be guaranteed. DETAILED DESCRIPTION

[0027] The content of the present invention can be more easily understood by selecting the following detailed description of the preferred implementation method of the present invention and the embodiments included. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. When there is a conflict, the definition in this specification shall prevail.

[0028] Specific implementation method 1: Deployment in the printer warehouse

[0029] like Figure 1 As shown, the light path reflected by the galvanometer is focused on the molding surface, and the PSD sensor coincides with the molding plane.

[0030] The position of the galvanometer is controlled by a program, thereby controlling the movement of the laser spot position.

[0031] The X-axis and Y-axis drive the PSD sensor to track the light spot position.

[0032] Generate the position (x0, y0) of the light spot on the PSD sensor.

[0033] The X scale, Y scale generates the position (x, y) of the PSD sensor.

[0034] Then the actual spot position (X, Y) is calculated as:

[0035] X=x+x0

[0036] Y=y+y0

[0037] Thus, a complete light spot position coordinate system is formed, which is converted into the correction file required by the galvanometer through software and sent to the device for execution.

[0038] During the SLM printing process, you can pause the printing and recalibrate the optical system without opening the chamber to ensure printing accuracy.

[0039] Specific implementation method 2: Deployment outside the printer

[0040] like Figure 2 As shown, each component is placed in a separate module. When in use, the module is placed on the molding surface of the printer, the data cable is connected, and after calibration, it is taken out for use.

[0041] After the module is placed in the printer, the position of the galvanometer is controlled by the program, thereby controlling the movement of the laser spot position.

[0042] The X-axis and Y-axis drive the PSD sensor to track the light spot position.

[0043] Generate the position (x0, y0) of the light spot on the PSD sensor.

[0044] The X scale, Y scale generates the position (x, y) of the PSD sensor.

[0045] Then the actual spot position (X, Y) is calculated as:

[0046] X=x+x0

[0047] Y=y+y0

[0048] Thus, a complete light spot position coordinate system is formed, which is converted into the correction file required by the galvanometer through software and sent to the device for execution.

[0049] This module can reduce costs to a certain extent and can be shared by multiple devices or promoted as a separate product.

Claims

1. A metal 3D printer laser spot position calibration system based on a two-dimensional PSD sensor, characterized in that: It includes a two-dimensional PSD sensor, an XY motion system with a high-precision scale, and a software system. It is used to solve the shortcomings of existing laser calibration solutions in SLM metal 3D printer equipment, such as slow speed, complex operation, and poor accuracy. It can realize automatic and semi-automatic calibration without the need for photo paper and auxiliary measuring equipment, and can complete all calibration work on one system.

2. The calibration system according to claim 1, characterized in that: The two-dimensional PSD sensor can convert the light spot position (x0, y0) into a digital signal or an analog signal and transmit it to the control system. The two-dimensional PSD sensor is installed on the XY motion system.

3. The calibration system according to claim 1, characterized in that: The XY motion system includes two motion axes: X motion axis and Y motion axis. The X motion axis and the Y motion axis are each equipped with a grating scale or a magnetic scale (hereinafter referred to as "scale") with an accuracy of plus or minus 1um, wherein the X scale and the Y scale are used to indicate the position (x, y) of the PSD sensor.

4. The calibration system according to claim 1, characterized in that: The Y motion axis can utilize the Y motion axis of the SLM metal 3D printer, and the X motion axis can utilize the powder scraper holder of the SLM metal 3D printer, so as to realize internal deployment of the machine and realize full automatic calibration during the printing process; the X / Y motion axis, the X / Y scale, and the PSD sensor can also be placed outside the device, put into the printer when in use, and taken out after the measurement and calibration are completed, so as to save costs.

5. The calibration system according to claim 1, characterized in that: After obtaining the coordinates (x0, y0) and (x, y), the software system obtains the precise position (X, Y) of the light spot through a superposition algorithm, and can convert it into a correction file required by the galvanometer and send it to the device for execution.

6. The calibration system according to claim 1, characterized in that: The light path reflected by the galvanometer is focused on the molding surface, and the PSD sensor coincides with the molding plane. The position of the galvanometer is controlled by the program, thereby controlling the movement of the laser spot position, and the X-axis and Y-axis drive the PSD sensor to track the spot position, and the actual spot coordinates are obtained by conversion.

7. The calibration system according to claim 1, characterized in that: Based on cost considerations, each component can be placed in an independent module. When in use, the module is placed on the molding surface of the printer and connected to the data cable. After calibration, it is taken out and put into use, so that multiple devices can share one calibration module.

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