CN116021766B - Robot-assisted laser additive manufacturing system and control method thereof - Google Patents
Robot-assisted laser additive manufacturing system and control method thereof Download PDFInfo
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- CN116021766B CN116021766B CN202310020688.9A CN202310020688A CN116021766B CN 116021766 B CN116021766 B CN 116021766B CN 202310020688 A CN202310020688 A CN 202310020688A CN 116021766 B CN116021766 B CN 116021766B
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- 239000011199 continuous fiber reinforced thermoplastic Substances 0.000 abstract description 12
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention discloses a robot-assisted laser additive manufacturing system and a control method thereof, and belongs to the technical field of additive manufacturing. The invention can realize that the printing unit at the tail end of the mechanical arm is placed on a printing plane or the surface of a formed part in the whole processing process by jointly controlling the movement of the position changing machine and the mechanical arm, is perpendicular to the point on the composite filament to be deposited, effectively avoids the torsion and breakage of a cable of the control element at the tail end of the mechanical arm due to the fact that the rotation of a joint exceeds the rotation angle range, simultaneously prevents the collision between the printing unit and the formed part, meets the requirement of controlling the printing unit at the tail end of the mechanical arm to continuously move to any point on the part manufactured by the additive under the condition that the position changing machine rotates to avoid redundant actions, ensures the forming continuity of the composite filament, improves the strength and the surface precision of the part for preparing the continuous fiber reinforced thermoplastic resin composite material, and ensures that the additive manufacturing process is faster, flexible and efficient.
Description
Technical Field
The invention belongs to the technical field of additive manufacturing, and particularly relates to a robot-assisted laser additive manufacturing system and a control method thereof.
Background
The continuous fiber reinforced thermoplastic resin composite material has the advantages of high strength, long service life, corrosion resistance, environment friendliness, recyclability and the like, is widely applied to the fields of aerospace, transportation, high-precision processing equipment and the like, and is gradually developed into a substitute material which can replace the traditional plastics and metals.
Additive manufacturing (additive manufacturing, AM) technology (also known as 3D printing technology) is a novel manufacturing technology developed in the late 80 s of the 20 th century, which mainly builds a three-dimensional digital model through a computer, and performs layer-by-layer accumulation forming by means of materials to finally obtain a formed part. The additive manufacturing technology can form parts with complex structures, various materials and individual customization without a die, and the traditional design and manufacturing approach of high-end equipment is overturned by the powerful support of the innovation of the design, so that a great number of product concepts are revolutionarily changed, and the technology has become a transition for supporting the manufacturing industry in China from transformation to an innovative driving development mode. Additive manufacturing technology for continuous fiber reinforced thermoplastic composites has become a hot spot area of research and development in both domestic and foreign academia and industry.
In order to meet the requirement of rapid manufacturing of large-size complex continuous fiber reinforced thermoplastic resin composite material parts, a multi-degree-of-freedom industrial robot is introduced into a robot-assisted laser additive manufacturing technology of additive manufacturing equipment, multi-degree-of-freedom additive manufacturing can be realized, and the method is an emerging field which is rapidly developed.
Like conventional additive manufacturing systems, robot-assisted laser additive manufacturing systems require the generation of the information flow required to control an object from a CAD three-dimensional digital model of the part. However, the information flow of the robot-assisted laser additive manufacturing system involves controlling the robot end printing unit (print head/deposition head) or other additive manufacturing related control elements according to a specified strategy, and on the other hand involves controlling the movement of the robot end printing unit along a specified processing path under conditions of limit and collision constraints meeting joint requirements, while the specific programming language and command communication protocol of the introduced industrial robot are different, so that the information flow of the control object of the robot-assisted laser additive manufacturing system is different from that of the conventional three-axis additive manufacturing system.
Typical industrial robots, such as six-axis robotic arm robots, cannot move to every point in the workspace in a continuous print path without performing redundant actions (stopping printing-cutting the composite filament-lifting the end printing unit-adjusting the end printing unit pose within a defined workspace) due to the limitations of the range of angles of rotation of the joints, the constraints of collision avoidance of the robotic arm with the forming part.
Therefore, there is a need for a motion control method of a robot-assisted laser additive manufacturing system, which can avoid the continuous tool path when the end printing unit is lifted and jumped as much as possible, and meet the requirement that the end printing unit of the robot can move to any point in the working space in a continuous printing path, so that the working space of the robot is effectively utilized, and the additive manufacturing is flexibly and efficiently performed.
Disclosure of Invention
In view of the above-mentioned drawbacks or improvements of the prior art, the present invention provides a robot-assisted laser additive manufacturing system and a control method thereof, which aim to implement a continuous composite filament forming path by processing information flows required for control generated from a three-dimensional digital model, and controlling the movement of a mechanical arm and a positioner in combination, so as to avoid lifting and jumping of an end printing unit as much as possible.
To achieve the above object, according to one aspect of the present invention, there is provided a robot-assisted laser additive manufacturing system including: the device comprises an upper computer control unit, a lower computer control unit, a mechanical arm, a positioner and a printing unit; the upper computer control unit comprises a three-dimensional digital model slicing system and a printing unit control system;
the model slicing system is used for slicing the three-dimensional digital model of the part into multiple layers in a self-adaptive manner, generating printing path information of each slice layer according to an optimal filling strategy and deriving a corresponding Gcode text file;
The printing unit control system is used for processing at least one rotary motion control code for controlling the tail end of the mechanical arm in the Gcode text file around the direction of the rotary shaft, adding a positioner control code to control the positioner to rotate, obtaining a substitute Gcode text file, and converting the substitute Gcode text file into a text file which can be read by the manufacturing system; wherein, the control code can realize the continuous printing movement of the printing unit by jointly controlling the movement of the positioner and the mechanical arm;
The lower computer control unit is used for receiving the text file output by the printing unit control system, controlling the mechanical arm, the printing unit and the positioner to cooperatively move, and realizing continuous additive manufacturing;
the printing unit is connected to the tail end of the mechanical arm and is used for providing a semi-molten composite filament;
The position changing machine is arranged below the mechanical arm, the surface of the position changing machine is rigidly connected with a printing platform, and the position changing machine is used for receiving the composite filament formed by the printing unit and finally bonding and stacking the composite filament layer by layer to form a high-density part.
Further, the lower computer control unit is a PLC control module.
Further, the printing unit comprises a wire feeding unit, a laser unit and a compression roller unit; the wire feeding unit is connected to the tail end of the mechanical arm and is used for feeding out continuous fiber composite filaments and limiting the feeding-out part to a position below the compression roller unit; the laser unit is connected to the tail end of the mechanical arm and is used for heating the sent continuous fiber composite filament to a semi-molten state higher than the glass transition temperature of the resin and lower than the decomposition temperature of the resin through laser; the compression roller unit is connected to the tail end of the mechanical arm and is used for generating pressure to flatten the continuous fiber composite filament which is not solidified after being heated by the laser beam into a strip shape.
Further, the system also includes a sacrificial abrasive article; the path of the printing unit follows the surface contour of the sacrificial grinder for forming complex curved parts.
Further, the press roller unit is provided with a freely rotating roller, and the surface of the roller is always parallel to the surface of the printing platform, the surface of the sacrificial grinding tool or the surface of the molded part in the molding process.
Further, the system also comprises an air supply pipe; the air supply pipe is used for supplying protective gas to the vicinity of the yarn feeding unit, and the protective gas inhibits the continuous fiber composite filament from burning when the continuous fiber composite filament is heated by the laser unit.
Further, the system also includes a filament storage tray for storing continuous fiber composite filament stock.
The invention also provides a control method based on the robot-assisted laser additive manufacturing system, which comprises the following steps:
S1, a model slicing system in an upper computer control unit slices a three-dimensional digital model of a part into multiple layers in a self-adaptive manner, print path information of each slice layer is generated according to an optimal filling strategy, and a corresponding Gcode text file is derived;
s2, the printing unit control system processes at least one rotary motion control code for controlling the tail end of the mechanical arm to rotate around the rotating shaft direction in the Gcode text file, and adds a positioner control code to control the positioner to rotate so as to obtain a substitute Gcode text file, and converts the substitute Gcode text file into a text file which can be read by the manufacturing system; wherein, the control code can realize the continuous printing movement of the printing unit by jointly controlling the movement of the positioner and the mechanical arm;
s3, the lower computer control unit receives control information of the upper computer printing unit control system and transmits the control information to the mechanical arm, the positioner and the printing unit, so that continuous additive manufacturing is realized.
In general, the above technical solution conceived by the present invention can achieve the following advantageous effects compared to the prior art.
The invention can realize that the printing unit at the tail end of the mechanical arm is placed on a printing plane or the surface of a formed part in the whole processing process by jointly controlling the movement of the position changing machine and the mechanical arm, is perpendicular to the point on the composite filament to be deposited, effectively avoids the cable (such as a power line of a laser unit or a guide tube of the composite filament) of the control element at the tail end of the mechanical arm from twisting and breaking due to the fact that the rotation of a joint exceeds the rotation angle range, simultaneously prevents the printing unit from colliding with the formed part, and meets the requirement of controlling the printing unit at the tail end of the mechanical arm to continuously move to any point on the part manufactured by the additive under the condition that the position changing machine rotates to avoid redundant actions (stopping printing-cutting the composite filament, lifting the printing unit at the tail end and adjusting the pose of the printing unit in a limited working space), ensures the continuity of the forming of the composite filament, and improves the strength and the surface precision of the prepared continuous fiber reinforced thermoplastic resin composite material part, so that the additive manufacturing process is faster, flexible and efficient.
Drawings
FIG. 1 is a schematic diagram of a robotic-assisted laser additive manufacturing system constructed in accordance with a preferred embodiment of the invention that can generate print path information and manufacture parts;
FIG. 2 is a schematic diagram of a robot-assisted laser additive manufacturing system coordinate system;
FIG. 3 is a schematic diagram of a forming process of a robot-assisted laser additive manufacturing system for preparing a continuous fiber reinforced thermoplastic resin composite;
FIG. 4 is a top view of a manipulator base coordinate system and an positioner origin coordinate system rotated by an angle θ relative to a world coordinate system;
FIG. 5 is a flow chart of steps of a method of motion control of a robot-assisted laser additive manufacturing system;
FIG. 6 is a schematic illustration in space of a print unit path generated by the slicing system in accordance with the preferred embodiment 1 of the present invention;
FIG. 7 is a schematic diagram of the principle of jointly controlling the movement of the positioner and the robot arm end printing unit, using the rotation of the positioner to replace the rotation of the robot arm end printing unit;
fig. 8 is a schematic view of a print unit path in space with a control robot arm end rotational motion control code processed by a print unit control system and with an positioner control code added to control positioner rotation in accordance with a preferred embodiment 1 of the present invention.
FIG. 9 is a schematic illustration in space of a print unit path generated by the slicing system in accordance with preferred embodiment 2 of the present invention;
FIG. 10 is a schematic view of a print unit path in space with a control robot arm end rotational motion control code processed by a print unit control system and with an positioner control code added to control positioner rotation in accordance with preferred embodiment 2 of the present invention.
FIG. 11 is a three-dimensional digital model of a wrench part according to preferred embodiment 3 of the invention
FIG. 12 is a schematic illustration in space of a print unit path generated by the slicing system in accordance with preferred embodiment 3 of the present invention;
FIG. 13 is a schematic view of a print unit path in space with a control robot arm end rotational motion control code processed by a print unit control system and with an positioner control code added to control positioner rotation in accordance with preferred embodiment 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
A robot-assisted laser additive manufacturing system comprises a mechanical arm 110, a positioner 120, a printing unit 130, a wire storage disc 140, an upper computer control unit 150, a lower computer control unit 160 and a system coordinate system. FIG. 1 is a schematic diagram of a robotic-assisted laser additive manufacturing system constructed in accordance with a preferred embodiment of the invention that can generate print path information and manufacture parts;
A robot arm 110, preferably a six-axis or seven-axis robot arm, further preferably a six-axis robot arm, the end of which is mounted with a printing unit 130; further, the end printing unit 130 thereof may be controlled by a control signal transmitted from the lower computer control unit 160 so as to move at an arbitrary speed with reference to the robot arm base coordinate system 201 by: x direction, Y direction, Z direction, X direction, Y direction, Z direction, and any combination thereof.
The positioner 120 is arranged below the mechanical arm 110, preferably a two-degree-of-freedom or three-degree-of-freedom positioner, further preferably a two-degree-of-freedom positioner, and is provided with a printing platform 121 on the surface thereof, and a printing unit 130 at the tail end of the mechanical arm 110 forms a part 123 on the printing platform 121; further, the printing platform 121 of the positioner 120 can be controlled by the control signal transmitted from the lower computer control unit 160 to move at any speed with reference to the origin coordinate system 202 of the positioner in the following manner: the + - θz direction of rotation about the Z axis, the + - θy direction of rotation about the Y axis at different speeds, may be synchronized or stationary with the speed of movement of the end printing unit 130 of the robotic arm 110 and maintained at any angle as desired for a particular application.
The printing platform 121 is rigidly connected to the positioner 120 for receiving the composite filaments 141 formed by the end printing unit 130 of the robotic arm 110 and eventually stacking the formed part 123 layer by layer without relative movement to the positioner 120, preferably a stainless steel or aluminum alloy plate.
The printing unit 130 comprises a laser unit 131, a wire feeding unit 132 and a compression roller unit 133, wherein the laser unit 131 is hinged to the mechanical arm 110, the laser emitting end of the laser unit is opposite to the discharge end of the composite filament 141 in a gap between the wire feeding unit 132, the laser unit is used for heating the composite filament 141 to a molten state higher than the glass transition temperature of resin and lower than the decomposition temperature of resin through laser, the compression roller unit 133 is connected to the mechanical arm 110, and the compression roller unit 133 is used for being matched with the printing platform 121 of the positioner 120 to flatten the composite filament 141 with adhesiveness, which is conveyed by the wire feeding unit 132, into a strip shape so as to bond the composite filament into a high-density part 123 layer by layer.
The filament storage disk 140 may store a limited length of composite filament 141 stock, the composite filament 141 being a continuous fiber composite filament.
The upper computer control unit 150 comprises a three-dimensional digital model slicing system 151 and a printing unit control system 152; the model slicing system 151 slices the three-dimensional digital model (such as STL model file) of the part into multiple layers in a self-adaptive way, then generates the printing path information of each slice layer according to the optimal filling strategy and derives the corresponding Gcode text file; the printing unit control system 152 converts the Gcode text file derived by the slicing system 151 into a substitute Gcode text file, processes at least one rotational motion control code for controlling the end of the mechanical arm around the direction of the rotation axis instead of the Gcode text file, and adds a positioner control code to control the rotation of the positioner, the control code can control the movement of the positioner 120 and the mechanical arm 110 by combining to realize continuous printing movement of the printing unit 130, and converts the substitute Gcode text file into a text file readable by the robot-assisted laser additive manufacturing system, and then transmits the text file to the lower computer control unit 160;
The lower computer control unit 160, preferably a PLC control module, can receive the control information of the upper computer printing unit control system 152 and transmit the control information to the mechanical arm 110, the positioner 120, and the printing unit 130, so as to implement the additive manufacturing process.
The system coordinate system comprises a mechanical arm base coordinate system 201, a positioner origin coordinate system 202 and a mechanical arm tail end coordinate system 203; the robot arm base coordinate system 201 is a reference coordinate system of the manufacturing system 101, the positioner origin coordinate system 202 is a coordinate system determined according to the intersection point of the rotation axes of the positioner 120, and the robot arm end coordinate system 203 is a coordinate system established according to a point near the end of the press roller unit 133 in the printing unit 130; when the mechanical arm 110 and the positioner 120 are placed, a plane formed by X, Y axes of the mechanical arm base coordinate system 201 is parallel to a plane formed by X, Y axes of the positioner origin coordinate system 202; at the initial time of printing, the origin coordinate system 202 of the positioner and the tail end coordinate system 203 of the mechanical arm need to ensure the set initial relative positions; further, at the initial time of the printing start, the relative pose relationship of the manipulator base coordinate system 201, the positioner origin coordinate system 202, and the manipulator end coordinate system 203 is known, and the relative pose of the sacrificial mold 122 and the positioner origin coordinate system 202 is fixed and known. Fig. 2 is a schematic diagram of a robot-assisted laser additive manufacturing system coordinate system.
The invention provides a process for preparing a continuous fiber reinforced thermoplastic resin composite material by a robot-assisted laser additive manufacturing system. The process drives the continuous fiber feeding unit 132 and the compression roller unit 133 to spatially move through the robot arm 2, the laser beam generated by the laser unit 131 is used for heating the composite filament 141 to a semi-molten state and flattening the composite filament into a strip shape under the action of the compression roller unit 133 so as to bond the composite filament into a high-density part 123 layer by layer, and fig. 3 is a schematic diagram of a forming process of a continuous fiber reinforced thermoplastic resin composite material prepared by a robot-assisted laser additive manufacturing system. From the above process principle, it is apparent that the end printing unit 130 of the robot arm 110 can only be moved forward along the wire feeding direction of the wire feeding unit 132, and in order to secure the strength and surface accuracy of the continuous fiber reinforced thermoplastic resin composite material part 123, the end printing unit 130 thereof needs to follow a continuous cutter path as much as possible to secure the continuity of the composite filament 141, and the end printing unit 130 of the robot arm 110 is placed on the printing plane 17 or the surface of the formed part 123, perpendicular to the point on the composite filament 141 to be deposited, throughout the process.
Therefore, the invention provides a robot-assisted laser additive manufacturing system motion control method. The rotary motion of the positioner printing platform 121 is utilized to compensate the posture change of the end printing unit 130, so that the continuous cutter path is implemented under the condition that the end printing unit 130 is lifted and jumped as far as possible, and the requirement that the robot end printing unit 130 can move to any point in the working space in the continuous printing path is met. Fig. 4 is a top view of the robot arm base coordinate system 201 and the positioner origin coordinate system 202 rotated by an angle θ with respect to the world coordinate system.
Fig. 5 is a flowchart of steps of a method for controlling the motion of a robot-assisted laser additive manufacturing system, comprising the steps of:
Step S1: the model slicing system 151 in the upper computer control unit 150 slices the three-dimensional digital model (such as STL model file) of the part into multiple layers in a self-adaptive way, then generates the printing path information of each slice layer according to the optimal filling strategy and derives the corresponding Gcode text file;
Step S2: the printing unit control system 152 converts the Gcode text file derived by the slicing system 151 into a substitute Gcode text file, and the substitute Gcode file processes at least one rotational motion control code for controlling the end printing unit 130 of the robot arm 110 about the direction of the rotation axis, and adds a control code for the positioner 120 to control the rotation of the positioner 120, which can realize the motion of continuous printing by the printing unit 130 by jointly controlling the movements of the positioner 120 and the robot arm 110.
Step S3: the printing unit control system 152 converts the text file replacing the Gcode into a text file which can be read by the robot-assisted laser additive manufacturing system, and then transmits the text file to the lower computer control unit 160, and the lower computer control unit 160 receives the control information of the upper computer printing unit control system 152 and transmits the control information to the mechanical arm 110, the positioner 120 and the printing unit 130 so as to realize the additive manufacturing process.
Further, when the mechanical arm 110 and the positioner 120 are placed, a plane whisker formed by X, Y axes of the mechanical arm base coordinate system 201 is parallel to a plane formed by X, Y axes of the positioner origin coordinate system 202; at the initial time of printing start, the positioner origin coordinate system 202 and the arm end coordinate system 203 should be ensured at the set initial relative positions.
Further, the print path information generated in step S1 does not need to be planar sliced and stacked in the z-direction as in conventional FDM printing, and the path information thereof may form a three-dimensional curved surface and may be stacked in any direction.
The method of control proposed by the present invention will be described in detail with reference to examples.
[ Example 1]
Three lines of path information in the Gcode text file derived for the model slicing system 151 in the upper computer control unit 150
G1 X930.58 Y-40.97
G1 X1180.58 Y-40.97
G1 X1180.58 Y59.03
The path information is interpreted as moving 250mm forward to the X axis and then 100mm forward to the Y axis. If only the mechanical arm 110 executes the corresponding tool path information, the robot-assisted laser additive manufacturing system according to the present invention prepares the continuous fiber reinforced thermoplastic resin composite material forming process principle, and the path information executed by the end printing unit 130 of the mechanical arm 110 is that
p1 X930.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00
p2 X1180.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00
p2 X1180.58 Y-40.97Z872.91 A-90.00B0.00 C-180.00
p3 X1180.58 Y59.03 Z872.91 A-90.00B0.00 C-180.00
Wherein X, Y, Z is the coordinate position of the robot arm end coordinate system 203 at the end of the printing unit 130 relative to the robot arm base coordinate system 201, A, B, C is the euler angle of the robot arm end coordinate system 203, the path includes an attitude change of the printing unit 130 at p 2 (a-180.00-a-90.00 indicates that the robot arm 110 end printing unit 130 rotates 90 ° counterclockwise around the Z axis of the robot arm end coordinate system 203), the printing unit needs to rotate 90 ° counterclockwise around the Z axis direction of itself, the final generated track is p 1-p2-p3, and the schematic diagram of the path information in space is shown in fig. 6. If similar posture changes are made a plurality of times, the cable of the end control element of the robot arm 110 (such as the power line of the laser unit 131 or the guide tube of the composite filament 141) may be twisted and broken by the joint rotation beyond the rotation angle range, or the collision of the printing unit 130 with the formed part 123 may be caused. To avoid the above problems, a scheme is generally adopted in which printing is stopped-cutting the composite filament 141-raising the end printing unit 130-adjusting the pose of the end printing unit 130 in a defined working space to restart printing, but this method causes the composite filament to be cut unevenly and a positioning error, which may cause a decrease in the strength and surface accuracy of the composite material part.
The invention adopts the scheme that the Gcode text file exported by the slicing system 151 is converted into a substitute Gcode text file by the printing unit control system 152, and the substitute Gcode file processes at least one rotary motion control code for controlling the printing unit 130 at the tail end of the mechanical arm 110 around the rotation axis direction, and adds a control code of the position shifter 120 to control the position shifter 120 to rotate. Fig. 7 is a schematic diagram showing the principle of jointly controlling the movement of the positioner 120 and the end printing unit 130 of the mechanical arm 110, and replacing the rotation of the end printing unit 130 of the mechanical arm 110 with the rotation of the positioner 120. At the initial moment of rotation of the positioner 120, the position-changing machine origin coordinate system 202 is SOT, and the position of the mechanical arm tail end coordinate system 203 relative to the current position-changing machine origin coordinate system 202 is at a point P s (s, t); when the positioner rotates θ, the positioner origin coordinate system 202 is rotated and converted to XOY, and the position of the arm end coordinate system 203 is rotated to a point P e (x, y) along with the positioner origin coordinate system 202. The relative position between the mechanical arm end coordinate system 203 and the origin coordinate system 202 of the positioner is kept unchanged (i.e. s=x; t=y) in the whole rotation process of the positioner 120, the euler angle of the mechanical arm end coordinate system 203 is unchanged, that is, the posture of the printing unit 130 is unchanged, and finally the motion track of the printing unit 130 at the end of the mechanical arm 110 is an arc P sPe. The alternate path information generated for this example is
p1 X930.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00E10.00 E20.00
p2 X1180.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00E10.00 E20.00
p3 X1009.52 Y-209.83Z872.91 A-180.00B0.00 C-180.00E10.00 E2-90.00
p4 X1109.52 Y-209.83Z872.91 A-180.00B0.00 C-180.00E10.00 E2-90.00
Wherein X, Y, Z is the coordinate position of the robot arm end coordinate system 203 at the end of the printing unit 130 relative to the robot arm base coordinate system 201, A, B, C is the euler angle of the robot arm end coordinate system 203, and E 1、E2 is the two rotation angles of the positioner 120. When the positioner rotates (E 20.00—E2 -90.00 indicates that the positioner printing platform 121 rotates 90 degrees clockwise around the Z axis), the position point of the tail end coordinate system 203 of the mechanical arm of the printing unit 130 rotates along with the origin coordinate system 202 of the positioner, the posture of the printing unit 130 is unchanged, the finally generated track is p 1-p2-p3-p4, and the schematic diagram of the path information in space is shown in fig. 8. The control code can realize continuous printing movement of the printing unit 130 by jointly controlling the movement of the positioner 120 and the mechanical arm 110, and the gesture of the printing unit 130 at the tail end of the mechanical arm 110 is unchanged in the whole process.
Finally, the printing unit control system 152 converts the text file replacing the Gcode into a text file readable by the robot-assisted laser additive manufacturing system, and transmits the text file to the lower computer control unit 160, and the lower computer control unit 160 receives the control information of the upper computer printing unit control system 152 and transmits the control information to the mechanical arm 110, the positioner 120 and the printing unit 130, so as to realize the additive manufacturing process that the actual forming path is p 1e-p3-p4 in fig. 8, which is equivalent to the required path p 1-p2-p3 in fig. 7.
[ Example 2]
Three lines of path information in the Gcode text file derived for the model slicing system 151 in the upper computer control unit 150
G1 X930.58 Y-40.97
G1 X1180.58 Y-40.97
G1 X930.58 Y-40.97
The path information is interpreted as moving 250mm positive to the X-axis and then 250mm negative to the X-axis. If only the mechanical arm 110 executes the corresponding tool path information, the robot-assisted laser additive manufacturing system according to the present invention prepares the continuous fiber reinforced thermoplastic resin composite material forming process principle, and the path information executed by the end printing unit 130 of the mechanical arm 110 is that
p1 X930.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00
p2 X1180.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00
p2 X1180.58 Y-40.97Z872.91 A0.00 B0.00 C-180.00
p3 X930.58 Y-40.97Z872.91 A0.00 B0.00 C-180.00
The path includes the posture change of the printing unit 130 at the point P 2 (a-180.00-a 0.00 indicates that the printing unit 130 at the tail end of the mechanical arm 110 rotates 180 ° anticlockwise around the Z axis of the tail end coordinate system 203 of the mechanical arm), the printing unit needs to rotate 180 ° anticlockwise around the Z axis direction of the printing unit, the finally generated track is P 1-p2-p3, and the schematic diagram of the path information in space is shown in fig. 9.
The alternative path information generated by the scheme adopted by the invention is that
p1 X930.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00E10.00 E20.00
p2 X1180.58 Y-40.97Z872.91 A-180.00B0.00 C-180.00E10.00 E20.00
p3 X840.66 Y-38.77Z872.91 A-180.00B0.00 C-180.00E10.00 E2-180.00
p4 X1090.66 Y-38.77Z872.91 A-180.00B0.00 C-180.00E10.00 E2-180.00
When the positioner rotates (E 20.00—E2 -180.00 indicates that the positioner printing platform 121 rotates 180 degrees clockwise around the Z axis), the position point of the tail end coordinate system 203 of the mechanical arm of the printing unit 130 rotates along with the origin coordinate system 202 of the positioner, the posture of the printing unit 130 is unchanged, the finally generated track is p 1-p2-p3-p4, and the schematic diagram of the path information in space is shown in fig. 10. The control code can realize continuous printing movement of the printing unit 130 by jointly controlling the movement of the positioner 120 and the mechanical arm 110, and the gesture of the printing unit 130 at the tail end of the mechanical arm 110 is unchanged in the whole process.
Finally, the printing unit control system 152 converts the text file replacing the Gcode into a text file readable by the robot-assisted laser additive manufacturing system, and transmits the text file to the lower computer control unit 160, and the lower computer control unit 160 receives the control information of the upper computer printing unit control system 152 and transmits the control information to the mechanical arm 110, the positioner 120 and the printing unit 130, so as to realize the additive manufacturing process that the actual forming path is p 1e-p3-p4 in fig. 10, which is equivalent to the required path p 1-p2-p3 in fig. 9.
[ Example 3]
The model slicing system 151 in the upper computer control unit 150 slices the three-dimensional digital model of the wrench part shown in fig. 11 into a plurality of layers, then generates print path information of each slice layer according to an optimal filling strategy and derives a corresponding Gcode text file, and the print path information of each slice layer is shown in fig. 12.
The print unit control system 152 converts the Gcode text file derived by the slicing system 151 into a substitute Gcode text file, and the substitute Gcode file processes a rotational movement control code for controlling the end print unit 130 of the robot arm 110 in the direction of the rotation axis, and adds a control code for the positioner 120 to control the rotation of the positioner 120, which can realize a movement for continuous printing by the print unit 130 by controlling the movements of the positioner 120 and the robot arm 110 in combination.
The printing unit control system 152 converts the substitute Gcode text file into a text file that can be read by the robot-assisted laser additive manufacturing system, and then transmits the text file to the lower computer control unit 160, and the lower computer control unit 160 receives the control information of the upper computer printing unit control system 152 and transmits the control information to the mechanical arm 110, the positioner 120 and the printing unit 130, so that the actual forming path is the additive manufacturing process shown in fig. 13, which is equivalent to the required path in fig. 11.
In general, the above technical solutions conceived by the present invention, compared with the prior art, enable the following beneficial effects to be obtained:
The invention provides a motion control method of a robot-assisted laser additive manufacturing system, which can realize that an end printing unit 130 of a mechanical arm 110 is placed on a printing plane 17 or the surface of a formed part 123 in the whole processing process and is perpendicular to a point on a composite filament 141 to be deposited by jointly controlling a positioner 120 and the mechanical arm 110 to move. The cable of the tail end control element of the mechanical arm 110 (such as a power line of the laser unit 131 or a guide tube of the composite filament 141) is effectively prevented from being twisted and broken due to joint rotation exceeding a rotation angle range, and meanwhile, the collision between the printing unit 130 and the formed part 123 is prevented, under the condition that the rotation of the positioner 120 is utilized to avoid redundant actions (stopping printing-cutting the composite filament 141-lifting the tail end printing unit 130-adjusting the pose of the tail end printing unit 130 in a limited working space), the requirement of controlling the tail end printing unit 130 of the mechanical arm 110 to continuously move to any point on the part 123 subjected to additive manufacturing is met, the forming continuity of the composite filament 141 is ensured, and the strength and the surface precision of the part 123 prepared by the continuous fiber reinforced thermoplastic resin composite material are improved, so that the additive manufacturing process is faster, flexible and efficient.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (8)
1. A robot-assisted laser additive manufacturing system, comprising: the device comprises an upper computer control unit, a lower computer control unit, a mechanical arm, a positioner and a printing unit; the upper computer control unit comprises a three-dimensional digital model slicing system and a printing unit control system;
the model slicing system is used for slicing the three-dimensional digital model of the part into multiple layers in a self-adaptive manner, generating printing path information of each slice layer according to an optimal filling strategy and deriving a corresponding Gcode text file;
The printing unit control system is used for processing at least one rotary motion control code for controlling the tail end of the mechanical arm in the Gcode text file around the direction of the rotary shaft, adding a positioner control code to control the positioner to rotate, obtaining a substitute Gcode text file, and converting the substitute Gcode text file into a text file which can be read by the manufacturing system; wherein, the control code can realize the continuous printing movement of the printing unit by jointly controlling the movement of the positioner and the mechanical arm;
The lower computer control unit is used for receiving the text file output by the printing unit control system, controlling the mechanical arm, the printing unit and the positioner to cooperatively move, and realizing continuous additive manufacturing;
the printing unit is connected to the tail end of the mechanical arm and is used for providing a semi-molten composite filament;
The position changing machine is arranged below the mechanical arm, the surface of the position changing machine is rigidly connected with a printing platform, and the position changing machine is used for receiving the composite filament formed by the printing unit and finally bonding and stacking the composite filament layer by layer to form a high-density part.
2. The robot-assisted laser additive manufacturing system of claim 1 wherein the lower computer control unit is a PLC control module.
3. The robot-assisted laser additive manufacturing system of claim 2 wherein the printing unit comprises a wire feed unit, a laser unit, and a pressure roller unit; the wire feeding unit is connected to the tail end of the mechanical arm and is used for feeding out continuous fiber composite filaments and limiting the feeding-out part to a position below the compression roller unit; the laser unit is connected to the tail end of the mechanical arm and is used for heating the sent continuous fiber composite filament to a semi-molten state higher than the glass transition temperature of the resin and lower than the decomposition temperature of the resin through laser; the compression roller unit is connected to the tail end of the mechanical arm and is used for generating pressure to flatten the continuous fiber composite filament which is not solidified after being heated by the laser beam into a strip shape.
4. The robot-assisted laser additive manufacturing system of claim 2 further comprising a sacrificial grinder; the path of the printing unit follows the surface contour of the sacrificial grinder for forming complex curved parts.
5. A robot-assisted laser additive manufacturing system according to claim 3, wherein the press roll unit is provided with freely rotating rollers, the roller surfaces being always parallel to the printing platform surface, the sacrificial grinding tool surface or the surface of the molded part during the molding process.
6. A robot-assisted laser additive manufacturing system according to claim 3, further comprising an air feed tube; the air supply pipe is used for supplying protective gas to the vicinity of the yarn feeding unit, and the protective gas inhibits the continuous fiber composite filament from burning when the continuous fiber composite filament is heated by the laser unit.
7. A robot-assisted laser additive manufacturing system according to any of claims 1-6, further comprising a filament storage tray for storing continuous fiber composite filament stock.
8. A control method based on the robot-assisted laser additive manufacturing system of any one of claims 1-7, comprising:
S1, a model slicing system in an upper computer control unit slices a three-dimensional digital model of a part into multiple layers in a self-adaptive manner, print path information of each slice layer is generated according to an optimal filling strategy, and a corresponding Gcode text file is derived;
s2, the printing unit control system processes at least one rotary motion control code for controlling the tail end of the mechanical arm to rotate around the rotating shaft direction in the Gcode text file, and adds a positioner control code to control the positioner to rotate so as to obtain a substitute Gcode text file, and converts the substitute Gcode text file into a text file which can be read by the manufacturing system; wherein, the control code can realize the continuous printing movement of the printing unit by jointly controlling the movement of the positioner and the mechanical arm;
s3, the lower computer control unit receives control information of the upper computer printing unit control system and transmits the control information to the mechanical arm, the positioner and the printing unit, so that continuous additive manufacturing is realized.
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| CA2914512A1 (en) * | 2013-06-05 | 2014-12-11 | Markforged, Inc. | Methods for fiber reinforced additive manufacturing |
| WO2016081496A1 (en) * | 2014-11-17 | 2016-05-26 | Markforged, Inc. | Multilayer fiber reinforcement design for 3d printing |
| WO2019059803A1 (en) * | 2017-09-25 | 2019-03-28 | Siemens Aktiengesellschaft | Additive manufacturing technique for manufacturing articles with composite structures |
| CN114193768A (en) * | 2021-12-13 | 2022-03-18 | 武汉理工大学 | Multi-filament forming device |
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| US9149988B2 (en) * | 2013-03-22 | 2015-10-06 | Markforged, Inc. | Three dimensional printing |
| US11440255B2 (en) * | 2018-09-14 | 2022-09-13 | MRI. Materials Resources LLC | Additive manufacturing under generated force |
| US11167483B2 (en) * | 2019-04-10 | 2021-11-09 | Northrop Grumman Systems Corporation | Methods and apparatus for fabrication of 3D integrated composite structures |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2914512A1 (en) * | 2013-06-05 | 2014-12-11 | Markforged, Inc. | Methods for fiber reinforced additive manufacturing |
| WO2016081496A1 (en) * | 2014-11-17 | 2016-05-26 | Markforged, Inc. | Multilayer fiber reinforcement design for 3d printing |
| WO2019059803A1 (en) * | 2017-09-25 | 2019-03-28 | Siemens Aktiengesellschaft | Additive manufacturing technique for manufacturing articles with composite structures |
| CN114193768A (en) * | 2021-12-13 | 2022-03-18 | 武汉理工大学 | Multi-filament forming device |
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