CN106903311A - A kind of electromagnetic induction selective laser fusing powder bed on-line heating system and method - Google Patents

Abstract

An electromagnetic induction laser selective melting powder bed online heating system and method, the system includes a powder bed in a laser selective melting forming room, a metal electromagnetic induction coil is arranged above the powder bed, the metal electromagnetic induction coil is connected to an intermediate frequency or high frequency heating power supply, and the intermediate frequency Or the high-frequency heating power supply is connected to the central controller through the control line, the metal electromagnetic induction coil is fixed on the non-metallic high-temperature-resistant support, the non-metallic high-temperature-resistant support is connected to the three-dimensional mobile support, and the three-dimensional mobile support is fixed in the laser selective melting and forming room. An infrared thermometer is installed above the metal electromagnetic induction coil, and a mobile powder spreading device is provided on the powder bed. The three-dimensional mobile support, infrared thermometer, and mobile powder spreading device are all connected to the central controller through the control line. On-line heating of the surface of the powder bed can be realized to reduce the temperature gradient in the forming area. When the heating temperature is high enough, the online annealing of the fabricated parts can be realized during the SLM forming process.

Description

An electromagnetic induction laser selective melting powder bed online heating system and method

technical field

The invention belongs to the technical field of additive manufacturing, and in particular relates to an electromagnetic induction laser selective melting powder bed on-line heating system and method.

Background technique

Due to the outstanding advantages of laser selective melting (SLM) in the preparation of high-performance and high-precision complex parts, it has become one of the hot spots in the field of additive manufacturing technology research. The core feature of laser selective melting technology is layer-by-layer processing, so as to realize the free forming of parts, and realize the shape-controlled manufacturing of parts according to the use requirements of parts.

In the laser selective melting metal forming, the high-energy laser beam scans the metal powder, which will cause the printing material to experience a process of rapid heating, melting and sudden cooling and solidification. The change is to cause the increase of residual stress, which is one of the main reasons for the warping, cracking and deformation of printed parts. Heating the bottom of the forming platform (generally <400°C) or preheating the metal powder (at a lower temperature) through electromagnetic coils or resistance wires can alleviate the internal stress accumulation inside the part to a certain extent, suppress surface cracks, and reduce Forming defects, improve the problem of warping deformation.

The method of heating the bottom of the forming platform can better achieve a uniform temperature field, thereby reducing the temperature gradient in the entire forming area, but there is a problem that the temperature in the forming height direction is limited. As the height of the formed part increases, the distance between the processing plane and the heating device becomes farther, resulting in poorer heating effect of the forming plane. Although the metal powder preheating method can also reduce the forming temperature gradient and reduce the stress to a certain extent, it has the problems of limited heating temperature and energy waste, and it cannot completely solve the warping deformation in SLM forming. question.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned prior art, the object of the present invention is to provide an electromagnetic induction laser selective melting powder bed on-line heating system and method, which can realize on-line heating on the surface of the powder bed, thereby reducing the temperature gradient in the forming area. When the heating temperature When it is high enough, online annealing can be realized on the fabricated parts during the SLM forming process, and at the same time, the energy density requirement of the laser body can be reduced, thereby improving the work efficiency.

In order to achieve the above object, the technical scheme that the present invention takes is:

An electromagnetic induction laser selective melting powder bed online heating system, comprising a powder bed 1 in a laser selective melting forming chamber 10, a metal electromagnetic induction coil 3 is arranged above the powder bed 1, a metal electromagnetic induction coil 3 and an intermediate frequency or high frequency heating power supply 6 connections, the intermediate frequency or high frequency heating power supply 6 is connected to the central controller 8 through the control line, the metal electromagnetic induction coil 3 is fixed on the non-metal high temperature resistant support 2, the non-metal high temperature resistant support 2 is connected to the three-dimensional mobile support 5, and the three-dimensional The mobile bracket 5 is fixed in the laser selective melting forming room 10, the infrared temperature measuring instrument 7 is arranged above the metal electromagnetic induction coil 3, the powder bed 1 is equipped with a mobile powder spreading device 9 matched with it, the three-dimensional mobile bracket 5, infrared temperature measurement Instrument 7, mobile powder spreading device 9 are all connected on the central controller 8 by control circuit.

The coil of the metal electromagnetic induction coil 3 is provided with a high temperature resistant insulating protective layer 4, which is any material, coating or coating that can protect laser scanning and prevent short circuits.

The metal electromagnetic induction coil 3 is any shape or size that can meet the requirements of heating the powder bed 1, the material to be processed or the workpiece to be printed from above the powder bed 1, and allowing the laser to pass through the gap between the coils for scanning and printing. metal coil.

The coil section of the metal electromagnetic induction coil 3 is circular or rectangular.

The outer structure shape of described metal electromagnetic induction coil 3 comprises back-shaped electromagnetic induction coil 11, S-shaped electromagnetic induction coil 12, vortex electromagnetic induction coil 13, spiral electromagnetic induction coil 14, circular electromagnetic induction coil 15 and square Electromagnetic induction coil 16.

The three-dimensional moving bracket 5 realizes the movement of the metal electromagnetic induction coil 3 in X, Y, and Z directions in the laser selective melting forming chamber 10 .

The infrared thermometer 7 measures the temperature of the powder bed 1 or the printed workpiece through the gap between the metal electromagnetic induction coils 3 .

The mobile powder spreading device 9 adopts a material or mechanism capable of completing the powder spreading work under the electromagnetic induction alternating magnetic field and high temperature environment.

A heating method based on the above-mentioned electromagnetic induction laser selective melting powder bed online heating system includes the following steps:

Step 1: After the laser selective melting equipment is turned on and the processing preparations are completed, the central controller 8 controls the three-dimensional mobile support 5 to hover above the powder bed 1 at a position higher than the mobile powder spreading device 9, while the central controller 8 Control mobile powder spreading device 9 to complete a powder spreading work;

Step 2: According to processing requirements, use software to divide the powder bed 1 into two types of areas according to the shape and size of the metal electromagnetic induction coil 3 and the scanning range of the laser. The first type of area is: when the metal electromagnetic induction coil 3 and the powder bed 1. When adjusting to the corresponding heating position and ensuring uniform heating, the laser passes through the gap between the metal electromagnetic induction coil 3 for scanning and processing. This area is called A area; the second type of area is: in the powder bed 1 All areas to be processed except A area, this area is called B area;

The third step: through the central controller 8 to control the three-dimensional mobile support 5 to drive the metal electromagnetic induction coil 3 to descend and move left and right, so that the metal electromagnetic induction coil 3 and the powder bed 1 maintain a corresponding heating distance, and the metal electromagnetic induction coil 3 and the powder bed 1 maintain a corresponding heating distance. The two areas of the powder bed 1 divided by the software correspond to each other, that is, to ensure that the metal electromagnetic induction coil 3 is located so that the laser passes through the gap between the coils to process the A area of the powder bed 1, so that the B area of the powder bed 1 is block;

Step 4: Turn on the intermediate frequency or high frequency heating power supply 6 through the central controller 8, the powder bed 1, the material to be processed or the workpiece to be printed generate heat in the alternating magnetic field, and the temperature rises; the target temperature is detected by the infrared thermometer 7, And feed back the detection data to the central controller 8, and the central controller 8 heats the powder bed 1, the processed material or the printed workpiece to the target temperature by adjusting the intermediate frequency or high frequency heating power supply 6;

Step 5: Turn on the equipment laser through the central controller 8, first process the A area of the powder bed 1, after the A area is processed, the central controller 8 controls the three-dimensional mobile support 5 to drive the non-metal high temperature resistant support 2 to electromagnetically induce the metal The coil 3 moves in the horizontal plane of the powder bed 1, so that the laser can pass through the gap between the coils of the metal electromagnetic induction coil 3 and scan to a part of the B area on the powder bed 1, and this part of the B area is converted into the A area that the laser can scan and process. , and then the central controller 8 turns on the laser to pass through the gap between the metal electromagnetic induction coils 3 to complete the scanning process. Similarly, the central controller 8 continuously moves the metal electromagnetic induction coil 3 in the horizontal plane, so that the laser gradually moves the powder bed 1 All areas to be processed are scanned;

Step 6: Control the three-dimensional mobile support 5 through the central controller 8 to drive the non-metal high temperature resistant support 2 to raise the metal electromagnetic induction coil 3 to a certain height, and the central controller 8 controls the mobile powder spreading device 9 to complete once under the metal electromagnetic induction coil 3 powdering work;

Step 7: Repeat steps 4, 5, and 6 until the entire printing process is completed;

Step 8: After the temperature of the laser selective melting forming chamber 10 and the workpiece to be printed is lowered to room temperature, turn off the protection device and the power supply of the equipment. So far the whole processing process is over.

The beneficial effects of the present invention are:

(1) The metal electromagnetic induction coil 3 is used to heat the powder bed 1 online above the forming platform, which ensures continuous heating of the powder bed 1 during the SLM forming process.

(2) Control the metal electromagnetic induction coil 3 to move horizontally and two-dimensionally above the powder bed 1 through software, so that the laser beam can pass through the gap between the metal electromagnetic induction coils 3 to process the processing area on the powder bed 1 successively, so that the laser beam Processing does not interfere with the process of online heating of the powder bed 1 by the metal electromagnetic induction coil 3 .

(3) When the heating temperature of the metal electromagnetic induction coil 3 to the powder bed 1 reaches a certain temperature, the online annealing of the fabricated part in SLM forming can be realized.

(4) The increase in the temperature of the powder bed 1 during the SLM forming process helps to reduce the energy density of the laser beam for powder melting, which can increase the laser scanning speed, scanning layer thickness or scanning spacing, etc., thereby improving work efficiency.

(5) The three-dimensional moving support 5 realizes the three-dimensional movement of the metal electromagnetic induction heating ring 3 by driving the non-metallic high-temperature-resistant support 2 , ensuring that it can complete the heating of the entire printing action platform 1 .

(6) The non-metal high temperature resistant bracket 2 can not only realize the supporting connection function, but also fix the metal electromagnetic induction coil 3 on it, so as to complete the adjustment of the coil spacing of the metal electromagnetic induction coil 3 .

(7) The high temperature resistant insulating protective layer 4 can prevent the laser from scanning the metal electromagnetic induction coil 3 by mistake to a certain extent, and at the same time, it can also play an insulating and protective role.

(8) According to actual needs, the coil section of the metal electromagnetic induction coil 3 can be circular or rectangular as required, and its outer structural shape can be the following six types: back-shaped electromagnetic induction coil 11, S-shaped electromagnetic induction coil 12, vortex Shaped electromagnetic induction coil 13, spiral electromagnetic induction coil 14, circular electromagnetic induction coil 15, rectangular electromagnetic induction coil 16.

(9) The heating method using electromagnetic induction eddy current heating is not only suitable for commonly used metal materials, but also suitable for SLM forming heating such as conductive or magnetic non-metallic materials, polymer materials, and composite materials.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

FIG. 2 is a schematic diagram of the installation of the metal electromagnetic induction coil 3 and the non-metal high temperature resistant bracket 2 of the embodiment.

FIG. 3 is a schematic diagram of the zigzag electromagnetic induction coil 11 .

FIG. 4 is a schematic diagram of the S-shaped electromagnetic induction coil 12 .

FIG. 5 is a schematic diagram of the vortex electromagnetic induction coil 13 .

FIG. 6 is a schematic diagram of the helical electromagnetic induction coil 14 .

FIG. 7 is a schematic diagram of the circular electromagnetic induction coil 15 .

FIG. 8 is a schematic diagram of the rectangular electromagnetic induction coil 16 .

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, an electromagnetic induction laser selective melting powder bed online heating system includes a powder bed 1 in a laser selective melting forming chamber 10, a metal electromagnetic induction coil 3 is arranged above the powder bed 1, a metal electromagnetic induction coil 3 and The medium-frequency or high-frequency heating power supply 6 is connected, the medium-frequency or high-frequency heating power supply 6 is connected to the central controller 8 through the control line, the metal electromagnetic induction coil 3 is fixed on the non-metallic high-temperature-resistant support 2, and the non-metallic high-temperature-resistant support 2 is connected on the three-dimensional On the mobile support 5, the three-dimensional mobile support 5 is fixed in the laser selective melting forming room 10, and the three-dimensional mobile support 5 realizes the movement of the metal electromagnetic induction coil 3 in the three directions of X, Y and Z in the laser selective melting forming room 10, and the metal An infrared thermometer 7 is arranged above the electromagnetic induction coil 3. The infrared thermometer 7 measures the temperature of the powder bed 1 or the printed workpiece through the gap between the metal electromagnetic induction coils 3. Device 9, the mobile powder spreading device 9 adopts a material or mechanism that can satisfy the powder spreading work under the electromagnetic induction alternating magnetic field and high temperature environment. As a preferred solution, the material of the mobile powder spreading device 9 in this embodiment is a ceramic scraper , its height dimension should be a little smaller as far as possible, just can reduce the ascending distance of metal electromagnetic induction coil 3 or need not move upwards when spreading powder like this, three-dimensional mobile support 5, infrared thermometer 7, mobile powder spreading device 9 all pass control Line is connected on the central controller 8.

As shown in Figure 2, the coil of the metal electromagnetic induction coil 3 is equipped with a high temperature resistant insulating protective layer 4, and the high temperature resistant insulating protective layer 4 is any material, coating or coating that can protect laser scanning and prevent short circuits , As a preferred solution, the high temperature resistant insulating protective layer 4 in this embodiment is a ceramic sleeve.

As shown in Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, and Fig. 8, the metal electromagnetic induction coil 3 can meet the requirements of heating the powder bed 1, the processed material or the printed workpiece from above the powder bed 1, Let the laser pass through the gap between the coils to scan and print metal coils of any shape or size. As a preferred solution, the coil cross section of the metal electromagnetic induction coil 3 can be circular or rectangular as required, and its outer structure The shape can be the following six types: back-shaped electromagnetic induction coil 11, S-shaped electromagnetic induction coil 12, vortex electromagnetic induction coil 13, spiral electromagnetic induction coil 14, circular electromagnetic induction coil 15, square electromagnetic induction coil 16, and above The six kinds of coils are only several preferred solutions of the metal electromagnetic induction coil 3, not all of them, as long as they can be suitable for all kinds of electromagnetic induction coils of the heating method of the present invention, no matter how their shape, structure and size change, no matter their coil cross-section is Circles, rectangles, ovals, etc. all belong to the category of the metal electromagnetic induction coil 3 .

A heating method based on the above-mentioned electromagnetic induction laser selective melting powder bed online heating system includes the following steps:

Step 1: After the laser selective melting equipment is turned on and the processing preparations are completed, the central controller 8 controls the three-dimensional mobile support 5 to hover above the powder bed 1 at a position higher than the mobile powder spreading device 9, while the central controller 8 Control mobile powder spreading device 9 to complete a powder spreading work;

Step 2: According to processing requirements, use software to divide the powder bed 1 into two types of areas according to the shape and size of the metal electromagnetic induction coil 3 and the scanning range of the laser. The first type of area is: when the metal electromagnetic induction coil 3 and the powder bed 1. When it is adjusted to the corresponding heating position and uniform heating can be ensured, the laser passes through the gap between the metal electromagnetic induction coil 3 coils (including the high temperature resistant insulation protection layer 4) for scanning and processing. This area is called A area; The second type of area is: all the areas to be processed on the powder bed 1 except for the A area, this area is called the B area;

The third step: through the central controller 8 to control the three-dimensional mobile support 5 to drive the metal electromagnetic induction coil 3 to descend and move left and right, so that the metal electromagnetic induction coil 3 and the powder bed 1 maintain a corresponding heating distance, and the metal electromagnetic induction coil 3 and the powder bed 1 maintain a corresponding heating distance. The two areas of the powder bed 1 divided by the software correspond to each other, that is, to ensure that the metal electromagnetic induction coil 3 is located so that the laser passes through the gap between the coils to process the A area of the powder bed 1, so that the B area of the powder bed 1 is block;

Step 4: Turn on the intermediate frequency or high frequency heating power supply 6 through the central controller 8, the powder bed 1, the material to be processed or the workpiece to be printed generate heat in the alternating magnetic field, and the temperature rises; the target temperature is detected by the infrared thermometer 7, And feed back the detection data to the central controller 8, and the central controller 8 heats the powder bed 1, the processed material or the printed workpiece to the target temperature by adjusting the intermediate frequency or high frequency heating power supply 6;

Step 5: Turn on the equipment laser through the central controller 8, first process the A area of the powder bed 1, after the A area is processed, the central controller 8 controls the three-dimensional mobile support 5 to drive the non-metal high temperature resistant support 2 to electromagnetically induce the metal The coil 3 moves in the horizontal plane of the powder bed 1, so that the laser can pass through the gap between the metal electromagnetic induction coil 3 coils (including the high temperature resistant insulation protection layer 4) and scan to a part of the B area on the powder bed 1, the part of the B area Converted to the A area where the laser can scan and process, then the central controller 8 turns on the laser to pass through the gap between the metal electromagnetic induction coil 3 coils to complete the scanning process. Similarly, the central controller 8 continuously moves the metal electromagnetic induction coil 3 in the horizontal plane , so that the laser gradually scans all the areas to be processed on the powder bed 1;

Step 6: Control the three-dimensional mobile support 5 through the central controller 8 to drive the non-metal high temperature resistant support 2 to raise the metal electromagnetic induction coil 3 to a certain height. During this process, the intermediate frequency or high frequency heating power supply 6 is turned off or maintained according to actual needs Open, when the height of the mobile powder spreading device 9 is small, according to the actual heating demand, when the distance between the metal electromagnetic induction coil 3 and the powder bed 1 is relatively large, there is no need to move the metal electromagnetic induction coil 3 upward; the central controller 8 controls the mobile powder spreading The device 9 completes a powder spreading work under the metal electromagnetic induction coil 3;

Step 7: Repeat steps 4, 5, and 6 until the entire printing process is completed;

Step 8: After the temperature of the laser selective melting forming chamber 10 and the workpiece to be printed is lowered to room temperature, turn off the protection device and the power supply of the equipment, and the entire processing process is over.

Claims (9)

1. a kind of electromagnetic induction selective laser fusing powder bed on-line heating system, including selective laser is melted in working chamber (10) Powder bed (1), it is characterised in that：Powder bed (1) top is provided with metal electromagnetic induction coil (3), metal electromagnetic induction coil (3) and in Frequency or high-frequency heating power (6) connection, intermediate frequency or high-frequency heating power (6) are connected by control circuit and central controller (8), Metal electromagnetic induction coil (3) is fixed on nonmetallic high temperature resistant support (2), and nonmetallic high temperature resistant support (2) is connected to three-dimensional On mobile support (5), the mobile support (5) of three-dimensional is fixed in selective laser fusing working chamber (10), metal electromagnetic induction coil (3) infrared radiation thermometer (7) is provided with above, powder bed (1) is provided with the mobile power spreading device (9) coordinated with it, the mobile support of three-dimensional (5), infrared radiation thermometer (7), mobile power spreading device (9) are connected on central controller (8) by control circuit.

2. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： High-temperature insulation protective layer (4), high-temperature insulation protective layer are installed on the coil of described metal electromagnetic induction coil (3) (4) it is that any one can protect laser scanning and the material, coating or the plated film that prevent short circuit.

3. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： Described metal electromagnetic induction coil (3) is to meet from powder bed (1) top heating powder bed (1), machined material or be printed Workpiece, allows laser to be passed through from gap between coil, is scanned any shape of printing or the wire coil of size.

4. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： The coil section of described metal electromagnetic induction coil (3) is circular or rectangle.

5. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： Described metal electromagnetic induction coil (3) external structure shape includes three-back-shaped electromagnetic induction coil (11), S-shaped electromagnetic induction coil (12), spiral type electromagnetic induction coil (13), spirality electromagnetic induction coil (14), circular electromagnetic induction coil (15) and square Electromagnetic induction coil (16).

6. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： The mobile support (5) of described three-dimensional realizes metal electromagnetic induction coil (3) in X, Y, Z in selective laser fusing working chamber (10) Three movements in direction.

7. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： Described infrared radiation thermometer (7) is through clearance measurement powder bed (1) between metal electromagnetic induction coil (3) or by printing workpiece temperature Degree.

8. powder bed on-line heating system is melted in a kind of electromagnetic induction selective laser according to claim 1, it is characterised in that： Described mobile power spreading device (9) is used and disclosure satisfy that the completion powdering work under electromagnetic induction alternating magnetic field and hot environment Material or mechanism form.

9. the heating means of powder bed on-line heating system are melted in a kind of electromagnetic induction selective laser according to claim 1, It is characterised in that it includes following steps：

The first step：After the start of selective laser melting unit, and complete to process preparation, controlled by central controller (8) The mobile support (5) of three-dimensional hovers over position of powder bed (1) top higher than mobile power spreading device (9), while central controller (8) is controlled The mobile power spreading device (9) of system completes a powdering job；

Second step：According to process requirements, with software by powder bed (1) according to the shape and size of metal electromagnetic induction coil (3) with And the sweep limits of laser is divided into two class regions, first kind region is：When metal electromagnetic induction coil (3) and powder bed (1) are adjusted Whole to corresponding heating location, and when can guarantee that uniform heating, laser enters through gap metal electromagnetic induction coil (3) coil The region of row scanning machining, this kind of region is referred to as a-quadrant；Equations of The Second Kind region is：Institute on powder bed (1) in addition to a-quadrant Need machining area, this kind of region is referred to as B regions；

3rd step：Carried out down by the three-dimensional mobile support (5) drive metal electromagnetic induction coil (3) of central controller (8) control Drop and left and right translation motion so that metal electromagnetic induction coil (3) heating distance corresponding with powder bed (1) holding, and metal electricity Magnetic induction coil (3) is corresponding with two regions of powder bed (1) that software is divided, i.e.,：Ensure metal electromagnetic induction coil (3) institute The position at place causes laser through the a-quadrant of gap processing powder bed (1) its coil so that the B regions of powder bed (1) are hidden Gear；

4th step：Intermediate frequency or high-frequency heating power (6), powder bed (1), machined material or quilt are opened by central controller (8) Printing workpiece heat in alternating magnetic field, temperature rises；Target temperature is detected by infrared radiation thermometer (7), and by detection data Feed back to central controller (8), central controller (8) by adjust intermediate frequency or high-frequency heating power (6) by powder bed (1), added Work material or by printing workpiece heat to target temperature；

5th step：By central controller (8) open equipment laser, first processing powder bed (1) a-quadrant, treat a-quadrant be processed After complete, the three-dimensional mobile support (5) of central controller (8) control drives nonmetallic high temperature resistant support (2) by metal electromagnetic induction line Circle (3) is moved in the horizontal plane in powder bed (1) so that laser can be through between metal electromagnetic induction coil (3) coil A part of B regions in gap scanning to powder bed (1), part B regions are converted to laser can be with the a-quadrant of scanning machining, then Central controller (8) opens laser and completes scanning machining through gap metal electromagnetic induction coil (3) coil, similarly, leads to Cross central controller (8) constantly movement metal electromagnetic induction coil (3) in the horizontal plane so that laser is progressively by powder bed (1) All scanning is completed in all regions to be processed；

6th step：Three-dimensional mobile support (5) is controlled to drive nonmetallic high temperature resistant support (2) by metal by central controller (8) Electromagnetic induction coil (3) rises certain altitude, and the mobile power spreading device (9) of central controller (8) control is in metal electromagnetic induction line Circle (3) lower section completes a powdering job；

7th step：Fourth, fifth, six steps are repeated, until entirely printing process is completed；

8th step：After being reduced to room temperature after selective laser fusing working chamber (10) and by printing workpiece temperature, protection device is closed And device power supply (DPS), so far whole process terminate.