3D printing apparatus and 3D printing method

Abstract

This invention relates to a three-dimensional printing apparatus and a three-dimensional printing method. The three-dimensional printing apparatus includes: a head having a nozzle surface with a plurality of nozzles for ejecting liquid; a robotic arm having a base and an arm supporting the head, and having a plurality of rotating parts extending from the base to the arm, wherein the position of the head relative to the base is changed by rotation of the rotating parts; and a cover having a fixed position relative to the base and covering the nozzle surface. The three-dimensional printing apparatus performs a covering action and a printing action. The covering action is an action in which the robotic arm positions the head at a position where the nozzle surface is covered by the cover. The printing action is an action in which the head ejects liquid from the workpiece while the robotic arm changes the position of the head relative to the workpiece to a position different from the position during the covering action. The yaw angle of the head during the covering action is different from the yaw angle of the head during the printing action.

Description

Technical Field

[0001] This invention relates to a three-dimensional printing apparatus and a three-dimensional printing method. Background Technology

[0002] A three-dimensional printing apparatus is known for printing on the surface of a three-dimensional workpiece by inkjet printing. For example, the apparatus described in Patent Document 1 has a robotic arm and a print head fixed to the top of the robotic arm.

[0003] In the printing apparatus described in Patent Document 1, there is a problem that the ink near the nozzle of the printhead becomes thickened or solidified due to the influence of external light or drying caused by external gas, which leads to nozzle blockage and consequently results in poor ejection.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2014-050832 Summary of the Invention

[0005] To address the above-mentioned issues, one embodiment of the three-dimensional printing apparatus of the present invention comprises: a head having a nozzle surface provided with a plurality of nozzles for ejecting liquid; a robotic arm having a base and an arm supporting the head, and having a plurality of rotating parts extending from the base to the arm, wherein the position of the head relative to the base is changed by rotation of the rotating parts; and a cover covering the nozzle surface. The three-dimensional printing apparatus performs a covering action and a printing action, wherein the covering action is an action by which the robotic arm positions the head at a position where the nozzle surface is covered by the cover, and the printing action is an action by which the head ejects liquid from the workpiece while the robotic arm changes the position of the head relative to the workpiece to a position different from the position during the execution of the covering action, wherein the yaw angle of the head during the execution of the covering action is different from the yaw angle of the head during the execution of the printing action.

[0006] One aspect of the three-dimensional printing method of the present invention uses the following components: a head having a nozzle surface with a plurality of nozzles for spraying liquid; a robotic arm having a base and an arm supporting the head, and having a plurality of rotating parts extending from the base to the arm, wherein the position of the head relative to the base is changed by rotation of the rotating parts; and a cover covering the nozzle surface. In the three-dimensional printing method, a covering action and a printing action are performed, wherein the covering action is the action of the robotic arm positioning the head at a position where the nozzle surface is covered by the cover, and the printing action is the action of the head spraying liquid onto the workpiece while the robotic arm changes the position of the head relative to the workpiece to a position different from the position during the execution of the covering action, wherein the yaw angle of the head during the execution of the covering action is different from the yaw angle of the head during the execution of the printing action. Attached Figure Description

[0007] Figure 1 A perspective view showing the outline of the three-dimensional printing apparatus according to the embodiment.

[0008] Figure 2 This is a block diagram illustrating the electrical structure of the three-dimensional printing apparatus according to the embodiment.

[0009] Figure 3 A three-dimensional diagram showing the outline structure of the head unit, including the head itself.

[0010] Figure 4 A perspective view showing the outline structure of the maintenance unit, including the cover.

[0011] Figure 5 A flowchart illustrating the operation of the three-dimensional printing apparatus according to the embodiment.

[0012] Figure 6 This is a side view of the robotic arm during the printing process.

[0013] Figure 7 This is a top view of a three-dimensional printing apparatus during the printing process.

[0014] Figure 8 A top view of the three-dimensional printing apparatus during the execution of the covering action. Detailed Implementation

[0015] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the dimensions and scales of the various parts in the drawings differ appropriately from actual dimensions, and some parts are shown schematically for ease of understanding. Furthermore, unless otherwise specified in the following description, the scope of the present invention is not limited to these embodiments.

[0016] For ease of explanation, the following description appropriately uses intersecting X-axis, Y-axis, and Z-axis. Furthermore, in the following description, one direction along the X-axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 and Y2 directions. Additionally, the opposite directions along the Z-axis are the Z1 and Z2 directions.

[0017] Here, the X, Y, and Z axes correspond to the coordinate axes of a universal coordinate system established within the space where the robotic arm 2, described later, is located. Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. A reference coordinate system based on the base of the robotic arm 2 is established to correspond with this universal coordinate system through calibration. In the following text, for ease of explanation, an example is given of using the universal coordinate system as the robotic arm coordinate system to control the movement of the robotic arm 2.

[0018] Additionally, the Z-axis does not have to be a vertical axis. Furthermore, although the X, Y, and Z axes are typically orthogonal, this is not a limitation, and there are cases where they are not orthogonal. For example, the X, Y, and Z axes only need to intersect each other at an angle between 80° and 100°.

[0019] 1. First Implementation Method

[0020] 1-1. Overview of a 3D printing apparatus

[0021] Figure 1 This is a perspective view showing an outline of the three-dimensional printing apparatus 1 according to the embodiment. The three-dimensional printing apparatus 1 is an apparatus that performs printing on the surface of a three-dimensional workpiece W by inkjet printing.

[0022] The workpiece W has a surface WF that becomes the object of printing. Figure 1 In the example shown, the workpiece W is an ellipsoidal rugby ball, and surface WF is curved. During printing, the workpiece W is supported as needed, for example by a predetermined mounting platform, robotic gripper, or conveyor belt. Furthermore, the shape or size of the workpiece W or surface WF is not limited to... Figure 1 The example shown is not an example of any particular method. Furthermore, the position or orientation of the workpiece W or surface WF during printing is not limited to any particular configuration, as long as printing is possible. Figure 1 The example shown is not for any position or orientation.

[0023] like Figure 1 As shown, the three-dimensional printing apparatus 1 includes a robotic arm 2, a head unit 3, a maintenance unit 4, a controller 5, a piping unit 10, and a wiring unit 11. These components will be briefly described in turn below.

[0024] Robotic arm 2 is the robotic arm that changes the position and orientation of head unit 3 in the general coordinate system. Figure 1 In the example shown, robotic arm 2 is a so-called six-axis vertical multi-joint robotic arm.

[0025] like Figure 1 As shown, the robotic arm 2 has a base 210 and an arm 220.

[0026] The base 210 is a platform that supports the arm 220. Figure 1 In the example shown, the base 210 is fixed to a mounting surface such as a floor surface or a base facing the Z1 direction by means of screws or the like. Furthermore, the mounting surface to which the base 210 is fixed can be a surface facing any direction, and is not limited to any particular direction. Figure 1 The example shown can also be a surface such as a wall, ceiling, or movable flatbed vehicle. Furthermore, in the following text, the case of viewing in a direction perpendicular to the mounting surface of the base 210, that is, viewing in the Z1 or Z2 direction in this embodiment, is sometimes referred to as "top view of the base 210", or simply "top view".

[0027] Arm 220 is a six-axis robotic arm having a base end mounted on base 210 and a tip that allows its position and orientation to change three-dimensionally relative to the base end. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, which are connected in this order.

[0028] Arm 221 is connected to base 210 via joint 230_1, allowing it to rotate about rotation axis O1. Arm 222 is connected to arm 221 via joint 230_2, allowing it to rotate about rotation axis O2. Arm 223 is connected to arm 222 via joint 230_3, allowing it to rotate about rotation axis O3. Arm 224 is connected to arm 223 via joint 230_4, allowing it to rotate about rotation axis O4. Arm 225 is connected to arm 224 via joint 230_5, allowing it to rotate about rotation axis O5. Arm 226 is connected to arm 225 via joint 230_6, allowing it to rotate about rotation axis O6.

[0029] Each of joints 230_1 to 230_6 is an example of a "rotating part," and is a mechanism that rotatably connects one of two adjacent components, the base 210 and the arms 221 to 226, to the other. Here, joint 230_1, the joint closest to the base 210 among joints 230_1 to 230_6, is an example of a "first rotating part." Furthermore, joint 230_6, the joint furthest from the base 210 among joints 230_1 to 230_6, is an example of a "second rotating part." Additionally, in the following text, each of joints 230_1 to 230_6 will sometimes be referred to as "joint 230."

[0030] Although Figure 1 Although not illustrated, each of the joints 230_1 to 230_6 is provided with a drive mechanism that causes one of the corresponding two adjacent components to rotate relative to the other. This drive mechanism may include, for example, a motor that generates a driving force for the rotation, a reducer that reduces and outputs the driving force, and a rotary encoder that detects the amount of motion, such as the angle of rotation. Furthermore, the assembly of these drive mechanisms for joints 230_1 to 230_6 corresponds to the description below. Figure 2 The arm drive mechanism 2a shown is illustrated.

[0031] Rotation axis O1 is a perpendicular axis to a mounting surface (not shown) on which the base 210 is fixed. Rotation axis O2 is a perpendicular axis to rotation axis O1. Rotation axis O3 is a parallel axis to rotation axis O2. Rotation axis O4 is a perpendicular axis to rotation axis O3. Rotation axis O5 is a perpendicular axis to rotation axis O4. Rotation axis O6 is a perpendicular axis to rotation axis O5.

[0032] Furthermore, for these rotating axes, "perpendicular" includes not only the case where the angle between the two rotating axes is strictly 90°, but also the case where the angle between the two rotating axes deviates from 90° within a range of approximately ±5°. Similarly, "parallel" includes not only the case where the two rotating axes are strictly parallel, but also the case where one of the two rotating axes is tilted relative to the other within a range of approximately ±5°.

[0033] On the uppermost arm 226 of the arm portion 220 of the robotic arm 2 described above, a head unit 3 is mounted as an end effector and is fixed in a fixed state by means of screws or the like.

[0034] Head unit 3 is an assembly having a head 3a that sprays ink, as an example of a "liquid," toward the workpiece W. In this embodiment, in addition to the head 3a, head unit 3 also includes a pressure regulating valve 3b, a curing light source 3c, and a distance sensor 3d. Further details regarding head unit 3 will be provided later. Figure 3 Let me explain.

[0035] The ink is not particularly limited, and examples include aqueous inks that dissolve color materials such as dyes or pigments in aqueous solvents, UV-curable inks that use curable resins, and solvent-based inks that dissolve color materials such as dyes or pigments in organic solvents. Curable inks are preferred. While the curable ink is not particularly limited, it can be any of the following types: thermosetting, photocurable, radiation-curable, and electron beam-curable, but photocurable types such as UV-curable are preferred. Furthermore, the ink is not limited to a solution and can also be an ink in which color materials are dispersed as a dispersion phase in a dispersant. Moreover, the ink is not limited to inks containing color materials; for example, it can be an ink that contains conductive particles such as metal particles used to form wiring as a dispersion phase, a transparent ink, or a treatment liquid for surface treatment of workpiece W.

[0036] A piping section 10 and a wiring section 11 are connected to the head unit 3. The piping section 10 includes piping or a piping assembly that supplies ink from an ink tank (not shown) to the head unit 3 via a supply pipe 10a. The supply pipe 10a is, for example, a flexible tube made of a rubber or elastomer material. The wiring section 11 includes wiring or a wiring assembly that supplies drive wiring 11a for driving electrical signals to the head unit 3a. The drive wiring 11a is, for example, made of various flexible electronic wiring. In addition to the supply pipe 10, the piping section 10 may also include other piping, such as piping for transporting ink discharged from the head unit 3. Furthermore, in addition to the drive wiring 11a, the wiring section 11 may appropriately include various wiring for transmitting other electronic signals, such as the control signal SI (described later), necessary for driving the head unit 3a.

[0037] Each of the piping section 10 and wiring section 11 is fixed in a position relative to the head unit 3 through connection with the head unit 3. Fixed position FX1 is a position within the end effector, specifically, the position of a connector (not shown) for connecting the piping section 10 and wiring section 11 to the head unit 3. Furthermore, each of the piping section 10 and wiring section 11 is fixed relative to the arm 220 of the aforementioned robotic arm 2 at fixed positions FX2, FX3, and FX4 by cable ties or the like. Fixed position FX2 is the position on the arm 224 described above. Fixed position FX3 is the position on the arm 223 described above. Fixed position FX4 is the position on the arm 222 described above. Thus, by partially fixing the piping section 10 and wiring section 11 to multiple positions on the arm 220, it is possible to maintain the positional relationship between the arm 220 and the piping section 10 and wiring section 11 within a predetermined range while sufficiently allowing the arm 220 to move. Additionally, although in Figure 1 The example illustrates a structure in which the winding paths of the piping section 10 and the wiring section 11 are the same, but it is also possible for the winding paths of the piping section 10 and the wiring section 11 to be different.

[0038] Maintenance unit 4 is a mechanism for performing maintenance on the head 3a of head unit 3. Figure 1 In the example shown, the maintenance unit 4 includes a housing 4a, a cover 4b, a support platform 4c, a suction mechanism 4d, and a wiping unit 4e. The housing 4a, like the base 210 of the robotic arm 2, is fixed to a mounting surface such as a floor or base facing the Z1 direction by screws or the like. Further details regarding the maintenance unit 4 will be provided later. Figure 3 To explain further. In addition, maintenance refers to the following concepts, including covering the nozzle surface F of the head 3a with the cover 4b, performing suction with the suction mechanism 4d, and wiping with the wiper part 4e.

[0039] Controller 5 is a robotic arm controller that controls the drive of robotic arm 2. The following is based on... Figure 2 The electrical structure of the stereolithography printing apparatus 1 is described in such a manner that a detailed description of the controller 5 is included.

[0040] 1-2. Electrical Structure of the Three-Dimensional Printing Apparatus

[0041] Figure 2 This is a block diagram illustrating the electrical structure of the three-dimensional printing apparatus 1 according to the embodiment. Figure 2 The diagram shows the electrical structural elements within the structural elements of the three-dimensional printing apparatus 1. For example... Figure 2 As shown, the stereolithography printing apparatus 1, in addition to having the features described above... Figure 1In addition to the structural elements shown, the system also includes a control module 6 that is communicatively connected to the controller 5, and a computer 7 that is communicatively connected to both the controller 5 and the control module 6. Before providing a detailed description of the controller 5, the control module 6 and the computer 7 will be described in turn.

[0042] in addition, Figure 2 The electrical structural elements shown can be appropriately divided, partially incorporated into other structural elements, or integrally formed with other structural elements. For example, some or all of the functions of controller 5 or control module 6 can be implemented by computer 7, or by other external devices such as PCs connected to controller 5 via networks such as LAN (Local Area Network) or the Internet.

[0043] The controller 5 has the function of controlling the drive of the robotic arm 2 and generating a signal D3 to synchronize the ink ejection action in the head unit 3 with the action of the robotic arm 2. Additionally, although the controller 5 in this embodiment also has the function of controlling the drive of the maintenance unit 4, this function can also be implemented by other devices such as the computer 7.

[0044] The controller 5 has a storage circuit 5a and a processing circuit 5b.

[0045] The storage circuit 5a stores various programs executed by the processing circuit 5b and various data processed by the processing circuit 5b. The storage circuit 5a may include, for example, a semiconductor memory comprising one or both of the following: volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory). Alternatively, part or all of the storage circuit 5a may also be included in the processing circuit 5b.

[0046] The path information Da is stored in the storage circuit 5a. The path information Da represents the path that the head unit 3 should move along and the orientation of the head unit 3 along that path. Here, the path information Da, as information representing the path and orientation, includes information representing the movement path and orientation of the head unit 3 when printing on the workpiece W, and information representing the movement path and orientation between the position of the head unit 3 during printing and the position during maintenance performed by the maintenance unit 4. The path information Da is determined, for example, based on the shape of the workpiece W, and is represented using coordinate values ​​from a reference coordinate system or a universal coordinate system. The shape of the workpiece W is obtained, for example, from CAD (computer-aided design) data representing the three-dimensional shape of the workpiece W. The path information Da described above is input from the computer 7 to the storage circuit 5a.

[0047] The processing circuit 5b controls the movement of the arm drive mechanism 2a of the robotic arm 2 based on the path information Da, and generates a signal D3. The processing circuit 5b may include, for example, one or more processors such as a CPU (Central Processing Unit). Alternatively, the processing circuit 5b may replace the CPU or include programmable logic devices such as an FPGA (Field-Programmable Gate Array) in addition to a CPU.

[0048] Here, the arm drive mechanism 2a is an assembly of the drive mechanisms of the joints 230_1 to 230_6 described above, and for each joint, it has a motor for driving the joint of the robotic arm 2 and an encoder for detecting the rotation angle of the joint of the robotic arm 2.

[0049] Processing circuit 5b performs inverse kinematics calculations, converting path information Da into motion quantities such as rotation angles and rotational speeds of each joint of the robotic arm 2. Furthermore, processing circuit 5b outputs control signals Sk1 based on the outputs D1 from each encoder of the arm drive mechanism 2a, so that the actual rotation angles and rotational speeds of each joint become the calculation results described above based on the path information Da. Control signals Sk1 control the drive of the motors in the arm drive mechanism 2a. Here, control signals Sk1 are corrected by processing circuit 5b as needed and based on the output from distance sensor 3d.

[0050] Furthermore, the processing circuit 5b generates a signal D3 based on the output D1 of at least one of the plurality of encoders from the arm drive mechanism 2a. For example, the processing circuit 5b generates a trigger signal as signal D3, the trigger signal containing a timing pulse from the output D1 of one of the plurality of encoders when it reaches a predetermined value.

[0051] The control module 6 is a circuit that controls the ink ejection action in the head unit 3 based on the signal D3 output from the controller 5 and the printing data from the computer 7. The control module 6 includes a timing signal generation circuit 6a, a power supply circuit 6b, a control circuit 6c, and a drive signal generation circuit 6d.

[0052] The timing signal generation circuit 6a generates a timing signal PTS based on signal D3. The timing signal generation circuit 6a is, for example, composed of a timer that starts generating the timing signal PTS upon detection of signal D3.

[0053] The power supply circuit 6b receives power from a commercial power supply not shown in the diagram and generates various predetermined potentials. These potentials are appropriately supplied to the control module 6 and various parts of the head unit 3. For example, the power supply circuit 6b generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head unit 3. Furthermore, the power supply potential VHV is supplied to the drive signal generation circuit 6d.

[0054] The control circuit 6c generates a control signal SI, a waveform specification signal dCom, a latch signal LAT, a clock signal CLK, and a switching signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. The waveform specification signal dCom is input to the drive signal generation circuit 6d, while the other signals are input to the switching circuit 3e of the head unit 3.

[0055] The control signal SI is a digital signal used to specify the operating state of the drive element of the head 3a of the head unit 3. Specifically, the control signal SI specifies whether to supply the drive signal Com (described later) to the drive element. By specifying this, for example, whether ink is ejected from the nozzle corresponding to the drive element, or the amount of ink ejected from the nozzle, is specified. The waveform specification signal dCom is a digital signal used to specify the waveform of the drive signal Com. The latch signal LAT and the exchange signal CNG specify the timing of ink ejection from the nozzle by specifying the drive timing of the drive element in conjunction with the control signal SI. The clock signal CLK is a clock signal that serves as a reference synchronized with the timing signal PTS.

[0056] The control circuit 6c described above includes, for example, one or more processors such as CPUs (Central Processing Units). Alternatively, the control circuit 6c can replace a CPU or include programmable logic devices such as FPGAs (field-programmable gate arrays) in addition to a CPU.

[0057] The drive signal generation circuit 6d is a circuit that generates drive signals Com for driving the drive elements of the head 3a of the head unit 3. Specifically, the drive signal generation circuit 6d includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 6d, the waveform specification signal dCom from the control circuit 6c is converted from a digital signal to an analog signal by the DA conversion circuit, and the analog signal is amplified by the amplification circuit using the power supply potential VHV from the power supply circuit 6b, thereby generating the drive signal Com. Here, the signal of the waveform contained in the drive signal Com that is actually supplied to the drive element is the drive pulse PD. The drive pulse PD is supplied to the drive element from the drive signal generation circuit 6d via the switching circuit 3e of the head unit 3.

[0058] Here, the switching circuit 3e is a circuit that switches whether to supply at least a portion of the waveform contained in the drive signal Com as a drive pulse PD based on the control signal SI.

[0059] Computer 7 has the function of supplying path information Da and other information to controller 5, and the function of supplying printing data and other information to control module 6. Computer 7 is, for example, a desktop or laptop computer with programs that implement these functions installed.

[0060] 1-3. Structure of the head unit

[0061] Figure 3 This is a perspective view showing the general structure of head unit 3, including head 3a. In the following description, intersecting a-axis, b-axis, and c-axis are used appropriately for ease of explanation. Furthermore, in the following description, one direction along the a-axis is the a1 direction, and the direction opposite to the a1 direction is the a2 direction. Similarly, the opposite directions along the b-axis are the b1 direction and the b2 direction. Furthermore, the opposite directions along the c-axis are the c1 direction and the c2 direction.

[0062] Here, the a-axis, b-axis, and c-axis correspond to the coordinate axes of the tool coordinate system set in the head unit 3, and their relative positions and orientations with the general coordinate system or robotic arm coordinate system described above change due to the movements of the robotic arm 2 described above. Figure 3 In the example shown, the c-axis is parallel to the rotation axis O6 described above. Furthermore, while the a-axis, b-axis, and c-axis are typically orthogonal to each other, this is not a limitation; for example, they only need to intersect at angles within the range of 80° to 100°. Additionally, the tool coordinate system is established to correspond with the reference coordinate system or the robot arm coordinate system through calibration. Moreover, the tool coordinate system is set, for example, with the center of the nozzle surface F described later as the reference (tool center point).

[0063] As mentioned above, head unit 3 includes a head 3a, a pressure regulating valve 3b, a hardening light source 3c, and a distance sensor 3d. These are... Figure 3 It is supported by the support body 3f, indicated by the double-dotted line. Additionally, although in Figure 3 In the example shown, the head unit 3 has one head 3a and one pressure regulating valve 3b, but this number is not limited to one. Figure 3 The example shown can also include more than two. Furthermore, the position of the pressure regulating valve 3b is not limited to arm 226; for example, it can be other arms or a position fixed relative to the base 210.

[0064] The support 3f is constructed of, for example, a metallic material and is essentially a rigid body. Furthermore, although in Figure 3 The support body 3f is a flat box shape, but the shape of the support body 3f is not particularly limited, but can be any shape.

[0065] The aforementioned support body 3f is mounted on the arm 226 described above. Therefore, the head 3a, pressure regulating valve 3b, hardening light source 3c, and distance sensor 3d are all supported together on the arm 226 by the support body 3f. Thus, the relative positions of the head 3a, pressure regulating valve 3b, hardening light source 3c, and distance sensor 3d relative to the arm 226 are fixed. Figure 3 In the example shown, a pressure regulating valve 3b is positioned at a c1 direction relative to the head 3a. A hardening light source 3c is positioned at a a2 direction relative to the head 3a. A distance sensor 3d is positioned at a a1 direction relative to the head 3a.

[0066] The head 3a has a nozzle face F and multiple nozzles N that open on the nozzle face F. Figure 3 In the example shown, the normal direction of the nozzle surface F is the c2 direction, and the plurality of nozzles N are divided into nozzle rows La and Lb arranged at intervals along the a-axis. Each of nozzle rows La and Lb is a collection of a plurality of nozzles N arranged in a straight line along the b-axis. Here, the elements associated with each nozzle N in nozzle row La and each nozzle N in nozzle row Lb in the first 3a are structurally approximately symmetrical with each other along the a-axis. Furthermore, the nozzle row direction DN, described later, is parallel to the b-axis.

[0067] Furthermore, in this embodiment, the nozzle surface F refers to a concept that includes both the surface formed by the nozzle plate and the surface formed by the fixing plate and the head cover. The nozzle plate is a plate-shaped component with nozzles N opened on it, made of materials such as silicon (Si) or metal. The fixing plate and head cover are components provided around the nozzle plate for purposes such as fixing and protecting it. Sometimes, the fixing plate and head cover are not provided depending on the head structure. Figure 3 The nozzle surface F shown is formed solely by the nozzle plate.

[0068] However, the positions of the multiple nozzles N in nozzle array La and the multiple nozzles N in nozzle array Lb along the b-axis can be either consistent or different. Furthermore, elements associated with each nozzle N in either nozzle array La or nozzle array Lb can be omitted. The following example illustrates a structure where the positions of the multiple nozzles N in nozzle array La and the multiple nozzles N in nozzle array Lb are consistent along the b-axis.

[0069] Although not shown in the figure, the head 3a has a piezoelectric element as a driving element and a cavity for collecting ink for each nozzle N. Here, the piezoelectric element causes a change in pressure in the cavity corresponding to the piezoelectric element, thereby causing ink to be ejected from the nozzle corresponding to the cavity. Such a head 3a is obtained by bonding together multiple substrates, such as silicon substrates, which have been appropriately processed by etching or the like, using adhesives or the like. Alternatively, a heater that heats the ink in the cavity can be used instead of the piezoelectric element as a driving element for ejecting ink from the nozzle.

[0070] As mentioned above, in the head 3a, ink is supplied to the ink tank (not shown) via the supply pipe 10a. Here, a pressure regulating valve 3b is provided between the supply pipe 10a and the head 3a.

[0071] The pressure regulating valve 3b is a valve mechanism that opens and closes according to the pressure of the ink in the head 3a. By opening and closing this valve, even if the positional relationship between the head 3a and the ink reservoir (not shown) described above changes, the pressure of the ink in the head 3a is maintained at a negative pressure within a predetermined range. Therefore, the meniscus of the ink formed in the nozzle N of the head 3a is stabilized. As a result, air bubbles are prevented from entering the nozzle N or ink overflowing from the nozzle N. Furthermore, the ink from the pressure regulating valve 3b is appropriately distributed to multiple parts of the head 3a via a branch channel (not shown). Here, the ink from the ink reservoir (not shown) is transported to the supply pipe 10a at a predetermined pressure by a pump or the like.

[0072] The curing light source 3c emits energy such as light, heat, electron beams, or radiation to cure or harden the ink on the workpiece W. For example, in the case where the ink has ultraviolet curing properties, the curing light source 3c is composed of a light-emitting element such as an LED (light-emitting diode) that emits ultraviolet light. In addition, the curing light source 3c may also appropriately include optical components such as lenses for adjusting the direction or range of energy emission.

[0073] Alternatively, the curing light source 3c may not completely harden or cure the ink on the workpiece W. In this case, for example, the ink irradiated by the energy from the curing light source 3c can be completely hardened or cured simply by the energy from the curing light source located on the mounting surface of the base 210 of the robotic arm 2. Furthermore, the curing light source 3c can be provided only as needed and may be omitted.

[0074] The distance sensor 3d is an optical displacement sensor that measures the distance between the head 3a and the workpiece W. In this embodiment, the distance sensor 3d outputs a signal corresponding to the distance between the head 3a and the workpiece W along the c-axis. Furthermore, the distance sensor 3d can be omitted as needed.

[0075] 1-4. Structure of the maintenance unit

[0076] Figure 4 This is a perspective view showing the outline structure of the maintenance unit 4, including the cover 4b. As mentioned above, Figure 4 The maintenance unit 4 shown has a housing 4a, a cover 4b, a support platform 4c, a suction mechanism 4d, and a wiping unit 4e.

[0077] The housing 4a is a box-shaped structure that supports the cover 4b, the support platform 4c, the suction mechanism 4d, and the wiping unit 4e. Furthermore, the shape of the housing 4a is not limited to... Figure 4 The example shown is not for any shape.

[0078] The cover 4b is a structure comprising a cover 4b1 that covers the nozzle surface F of the head 3a, a guide 4b2, and a force-applying mechanism 4b3. Figure 4In the example shown, the cover 4b is elongated. The cover 4b1 is an elastic cover made of rubber or an elastomer, which prevents the ink near the nozzle N of the head 3a from drying by covering the nozzle surface F of the head 3a. The cover 4b1 has an outer frame portion that abuts against the nozzle surface F of the head 3a, a bottom surface recessed in the Z2 direction relative to the outer frame portion, and a hole penetrating the cover 4b1. During the covering operation described later, in which the cover 4b covers the nozzle surface F of the head 3a, the outer frame portion abuts against the nozzle surface F of the head 3a in a manner that surrounds the nozzle N set on the horizontally positioned nozzle surface F. Furthermore, the bottom surface faces the nozzle surface F at this time. The hole has an opening at one end on the bottom surface of the recess and an opening at the other end connected to the suction mechanism 4d.

[0079] The force-applying mechanism 4b3 supports the cover 4b1 and applies force in the Z1 direction, and is constructed using an elastic body such as a spring or rubber. The guide part 4b2 is a component that restricts the movement of the cover 4b1 in a direction different from the Z direction. When the nozzle surface F of the head 3a abuts against the outer frame part described above, the elastic body of the force-applying mechanism 4b3 elastically deforms by contracting in the Z direction. Alternatively, the force-applying mechanism 4b3 can also be a mechanism such as a gas strut.

[0080] The cover 4b is supported by a support platform 4c. The support platform 4c is constructed by a top surface 4c1 on which the cover 4b is fixed, and multiple feet 4c2 that support the top surface 4c1. The top surface 4c1 is a plate-shaped component made of metal or the like, and the cover 4b and the wiper part 4e are fixed to the top surface 4c1 by screws or the like.

[0081] The suction mechanism 4d is a mechanism for depressurizing the space formed between the cover 4b and the nozzle surface F. By utilizing this depressurization, ink is drawn from the nozzle N of the head 3a when the nozzle surface F is covered by the cover 4b, thereby renewing the ink within the nozzle N. Although not shown, the suction mechanism 4d includes a pressure-reducing tank and a pressure-reducing pump 4d2. The pressure-reducing tank is, for example, a metal chamber with a depressurized internal space, and is disposed within the housing 4a described above. The pressure-reducing tank communicates with the hole in the cover 4b described above and with the pressure-reducing pump. The pressure-reducing pump is a mechanism for depressurizing the pressure-reducing tank by venting air from it. In addition, valves for pressure regulation or opening / closing are provided between the pressure-reducing tank and the cover 4b, and between the pressure-reducing tank and the pressure-reducing pump.

[0082] The wiping part 4e is a structure of a wiping device 4e1 disposed adjacent to the cover part 4b and having a function of wiping the nozzle surface F. Figure 4In the example shown, the wiper part 4e is elongated and arranged parallel to the cover part 4b. The wiper 4e1 is an elastic scraper-shaped component made of rubber or elastomeric material, which cleans the nozzle surface F of the head 3a by wiping it. The wiper 4e1 is fixed to the top surface 4c1 of the support platform 4c via the support body 4e2 and by screws or the like.

[0083] 1-5. Operation of the 3D printing apparatus 1

[0084] Figure 5 This is a flowchart illustrating the operation of the three-dimensional printing apparatus 1 according to the embodiment. Figure 5 As shown, firstly, the stereoscopic printing apparatus 1 determines whether a printing instruction has been received in step S1. This determination is performed, for example, by the processing circuit 5b determining whether a printing execution instruction has been received from the computer 7.

[0085] Upon receiving a printing instruction, the stereoscopic printing apparatus 1 performs a first movement in step S2. This first movement is an action that moves the head 3a to the starting position for the printing action described later, which is implemented by the processing circuit 5b controlling the drive of the robotic arm 2 based on path information Da.

[0086] Following step S2, the stereolithography printing apparatus 1 performs a printing operation in step S3. This printing operation involves printing ink onto the workpiece W using ink from the head 3a. This operation is implemented by the processing circuit 5b controlling the drive of the robotic arm 2 based on path information Da, and the control module 6 controlling the drive of the head 3a.

[0087] After step S3, or in the absence of a printing instruction, the stereoscopic printing apparatus 1 determines in step S4 whether an overlay instruction exists. This determination is performed, for example, by the processing circuit 5b determining whether an overlay instruction has been sent from the computer 7. Alternatively, the processing circuit 5b may determine that an overlay instruction exists if a predetermined time has elapsed without any printing instruction or overlay instruction from the computer 7.

[0088] In the absence of a cover instruction, the stereoscopic printing apparatus 1 returns to step S1 as described above. On the other hand, in the presence of a cover instruction, the stereoscopic printing apparatus 1 performs a second movement action in step S5. This second movement action is an action that moves the head 3a to the execution start position of the cover action described later, which is implemented by the processing circuit 5b controlling the drive of the robotic arm 2 based on the path information Da.

[0089] Following step S5, the stereolithography printing apparatus 1 performs a covering action in step S6. This covering action, for example, involves bringing the nozzle surface F of the head 3a into contact with the cover portion 4b and covering the nozzle surface F with the cover portion. This is performed by the processing circuit 5b controlling the drive of the robotic arm 2 based on path information Da. However, the covering action may sometimes include situations where the nozzle surface F and the cover portion 4b are not strictly in contact. This is true for cases where the nozzle surface F is separated from the cover portion 4b by a few millimeters, and for cases where ink or other substances are present between the nozzle surface F and the cover portion 4b.

[0090] Following step S6, the stereolithography printing apparatus 1 determines in step S7 whether an end instruction exists. This determination is performed, for example, by the processing circuit 5b determining whether an end instruction has been sent from the computer 7.

[0091] The stereolithography printing apparatus 1 returns to step S1 as described above if there is no end instruction, and ends the operation if there is an end instruction.

[0092] Figure 6 This is a side view of robotic arm 2 during the execution of the printing action in step S3. Figure 6 The example illustrates printing on surface WF of a workpiece W, where the workpiece W, being ellipsoidal in shape, is positioned such that its major axis AX is parallel to the X-axis. Here, the workpiece W is positioned at a location closer to the X2 direction than the robotic arm 2. Furthermore, in... Figure 6 In the pose of head 3a shown by the solid line, the a-axis is parallel to the X-axis, the b-axis is parallel to the Y-axis, and the c-axis is parallel to the Z-axis.

[0093] like Figure 6 As shown, during the printing operation, robotic arm 2 moves head 3a along the movement path RU. The movement path RU is a path along surface WF from position PS to position PE. The movement path RU is a straight line extending along the X-axis when viewed in the Z2 direction.

[0094] During the printing process, robotic arm 2 moves three of the six joints 230. Figure 6 In the example shown, during the printing operation, the robotic arm 2 aligns the rotation axes of joints 230_2, 230_3, and 230_5 parallel to the Y-axis and performs the movements of these joints. Thus, the head 3a can be stably moved along the movement path RU by the movement of the three joints 230.

[0095] Here, preferably, the robotic arm 2 controls the attitude of the head 3a according to the curvature of the surface WF, so that the spray direction of the ink from the head 3a relative to the surface WF is fixed. Therefore, it is preferable that the yaw angle and tilt angle of the head 3a in the movement path RU are fixed values. On the other hand, it is preferable that the pitch angle of the head 3a in the movement path RU varies. That is, it is preferable that the pitch angles of the head 3a at the first position P1 and the second position P2, which are any two points in the movement path RU, are different from each other. In addition, in this embodiment, the movement path RU is set such that the ejection direction vector of the ink droplets ejected by the head 3a includes a component that is always vertically downward. In other words, the vector in the c2 direction includes a component in the Z2 direction. With such a setting of the movement path RU, since the head 3a will not eject ink droplets in a direction that opposes gravity, the flight of the ink droplets is more stable.

[0096] The above printing process is used to print on the workpiece W.

[0097] Here, the yaw, roll, and pitch angles of the head are explained. The yaw, roll, and pitch angles of head 3a are represented as rotations around the c-axis, a-axis, and b-axis relative to an arbitrarily set reference attitude of head 3a. Furthermore, in the reference attitude of head 3a, the relationships between the a-axis, b-axis, c-axis, and the X-axis, Y-axis, and Z-axis are fixed in a unique form.

[0098] The yaw angle of the head in the first posture of head 3a is represented as the amount of rotation about the c-axis required for the posture change from the reference posture to the first posture. This amount of rotation about the c-axis refers to the absolute value of the angle between the a-axis in the reference posture and the a-axis in the first posture when viewed along the c-axis direction in the reference posture. Alternatively, the amount of rotation about the c-axis refers to the absolute value of the angle between the b-axis in the reference posture and the b-axis in the first posture when viewed along the c-axis direction in the reference posture.

[0099] Similarly, the head tilt angle in the first posture of head 3a is represented as the amount of rotation about the a-axis required for the posture change from the reference posture to the first posture. This amount of rotation about the a-axis refers to the absolute value of the angle between the b-axis in the reference posture and the b-axis in the first posture when viewed along the direction of the a-axis in the reference posture. Alternatively, the amount of rotation about the a-axis refers to the absolute value of the angle between the c-axis in the reference posture and the c-axis in the first posture when viewed along the direction of the a-axis in the reference posture.

[0100] Similarly, the pitch angle of the head in the first posture of head 3a is represented as the amount of rotation about the b-axis required for the posture change from the reference posture to the first posture. This amount of rotation about the b-axis refers to the absolute value of the angle between the a-axis in the reference posture and the a-axis in the first posture when viewed along the direction of the b-axis in the reference posture. Alternatively, the amount of rotation about the b-axis refers to the absolute value of the angle between the c-axis in the reference posture and the c-axis in the first posture when viewed along the direction of the b-axis in the reference posture.

[0101] use Figure 6 Let's further explain the yaw, roll, and pitch angles of head 3a. For example, let's set the reference attitude of head 3a as an attitude where the a-axis is parallel to the X-axis, the b-axis is parallel to the Y-axis, and the c-axis is parallel to the Z-axis. At this point... Figure 6 The yaw, roll, and pitch angles of head 3a, as shown by the solid line, are all 0°. On the other hand, Figure 6 The pitch angle of head 3a, indicated by the dashed line, is approximately 45°, while the yaw and roll angles are 0°. In other words, Figure 6 The pitch angles of head 3a, shown by the solid line, and head 3a, shown by the dashed line, are different.

[0102] Figure 7 This is a top view of the three-dimensional printing apparatus 1 during the printing process. Figure 7 In the posture of head 3a, shown by the solid line, axis a is parallel to the X-axis, axis b is parallel to the Y-axis, and axis c is parallel to the Z-axis. During the execution of the printing action, as... Figure 7 As shown, when viewed from above the base 210, the arrangement direction of the plurality of nozzles N of the head 3a, i.e., the nozzle array direction DN, is orthogonal to the scanning direction DS of the head 3a in the aforementioned movement path RU. Here, when viewed from above the base 210, if the imaginary line segment connecting the head 3a and the base 210 during the printing operation is defined as the first line segment L1, the angle θ1 between the nozzle array direction DN and the first line segment L1 is 90°. However, the angle θ1 is not limited to 90°; for example, it can be within the range of 70° to 110°. Furthermore, the first line segment L1 can be more strictly defined as the imaginary line segment connecting the center point of the nozzle surface F and the rotation axis O1 during the printing operation when viewed from above the base 210.

[0103] After the printing action is performed, the second movement described above is then performed, thereby achieving the desired result. Figure 7 As shown by the double-dotted line, head 3a moves onto cover 4b. Although in Figure 7 In the pose of head 3a, indicated by the double-dotted line, the c-axis is parallel to the Z-axis, but the angle between the a-axis and the X-axis is 45°, and the angle between the b-axis and the Y-axis is 45°.

[0104] Here, the reference attitude of head 3a is set as an attitude where the a-axis is parallel to the X-axis, the b-axis is parallel to the Y-axis, and the c-axis is parallel to the Z-axis. At this time, Figure 7 The yaw, roll, and pitch angles of head 3a, as shown by the solid line, are all 0°. On the other hand, Figure 7 The yaw angle of head 3a, indicated by the double-dotted line, is 45°, while the roll and pitch angles are 0°. In other words, Figure 7 The yaw angles of head 3a, shown by the solid line, and head 3a, shown by the double-dotted line, are different. In other words, the nozzle array direction DN of nozzle N, when viewed from any coordinate in the universal coordinate system towards the Z1 direction, is different during the printing action, after the movement action, or during the covering action. More specifically, the angle between the nozzle array direction DN during the printing action and the nozzle array direction DN after the movement action or during the covering action is 45°.

[0105] The second movement is primarily performed when joint 230_1 is moved. While joints 230_2, 230_3, and 230_5, used in the printing action described above, could also be moved, it is preferable not to move joints 230_4 and 230_6. In this case, the reproducibility of the robotic arm 2's movements during the printing action can be improved when the printing action is performed again.

[0106] Figure 8 A top view of the three-dimensional printing apparatus 1 during the execution of the covering action. (See attached image.) Figure 8 As shown, when viewed from above the base 210, if the imaginary line segment connecting the head 3a and the base 210 during the execution of the covering action is defined as the second line segment L2, the angle θ2 between the nozzle row direction DN and the second line segment L2 is 90°. However, the angle θ2 is not limited to 90°; for example, it can be within the range of 70° to 110°. Furthermore, the second line segment L2 can be more strictly defined as the imaginary line segment connecting the center point of the nozzle surface F and the rotation axis O1 during the execution of the covering action when viewed from above the base 210.

[0107] Here, when viewed from above the base 210, if the angle between the first line segment L1 and the second line segment L2 is set to θ3, the angles θ1, θ2, and θ3 satisfy the relationship |θ1-θ2| < θ3. Furthermore, from the viewpoint of reducing the twisting of the piping section 10 and the wiring section 11, it is preferable to make |θ1-θ2| as small as possible.

[0108] After the covering action is executed, the first movement action described above is performed as follows: Figure 8As shown by the double-dotted line, head 3a moves to the printing position described above. The first movement, like the second movement, is primarily performed when joint 230_1 is moved.

[0109] As described above, the stereolithography apparatus 1 includes a head 3a, a robotic arm 2, and a cover 4b. The head 3a has a nozzle surface F, on which multiple nozzles N are provided for ejecting ink, an example of a "liquid". The robotic arm 2 has a base 210 and an arm 220 that supports the head 3a. Joints 230_2 to 230_6, an example of "multiple rotating parts", are provided across the arm 220 from the base 210. Rotation of the joints 230_2 to 230_6 changes the position of the head 3a relative to the base 210. The cover 4b covers the nozzle surface F.

[0110] Furthermore, as described above, the stereolithography printing apparatus 1 performs the covering action in step S6 and the printing action in step S3. In the covering action of step S6, the robotic arm 2 positions the head 3a at the location covered by the nozzle surface F by the covered portion 4b. In the printing action of step S3, the robotic arm 2 changes the position of the head 3a relative to the workpiece W to a position different from the position during the covering action of step S6, and the head 3a ejects ink onto the workpiece W. Here, the yaw angle of the head 3a during the covering action of step S6 is different from the yaw angle of the head 3a during the printing action of step S3.

[0111] In the above-described 3D printing apparatus 1, since the nozzle surface F is covered by the cover portion 4b during the covering action in step S6, the ink thickening or curing on the nozzle surface F can be reduced even if the printing action in step S3 is not performed for a long time. As a result, clogging caused by ink from each nozzle N can be reduced. Furthermore, by making the yaw angle of the head 3a different during the covering action in step S6 and the printing action in step S3, the rotation amount of the joint 230_6 closest to the head among the multiple joints 230 of the robotic arm 2 can be reduced when the head 3a moves between the positions of these actions. As a result, damage caused by twisting of wiring associated with the head 3a can be reduced.

[0112] Here, the stereolithography printing apparatus 1 also includes a supply pipe 10a and a drive wiring 11a. The supply pipe 10a supplies ink to the head 3a, and the drive wiring 11a supplies an electrical signal to the head 3a to drive it. The supply pipe 10a and the drive wiring 11a are respectively disposed outside the arm portion 220. When each of such a supply pipe 10a and drive wiring 11a maintains a fixed yaw angle of the head 3a while repeatedly performing the printing action of step S3 and the covering action of step S6, there is a possibility of damage due to twisting. Therefore, when using such a supply pipe 10a or drive wiring 11a, the aforementioned effect caused by making the yaw angle of the head 3a different in the printing action of step S3 and the covering action of step S6 is more significant.

[0113] Furthermore, from the viewpoint of reducing damage caused by wiring twisting, as mentioned above, it is preferable that, when viewed from above the base 210, the angle between the first line segment L1 and the nozzle array direction DN during the printing operation of step S3 is set to θ1, the angle between the second line segment L2 and the nozzle array direction DN during the covering operation of step S6 is set to θ2, and the angle between the first line segment L1 and the second line segment L2 is set to θ3, the relationship |θ1-θ2|<θ3 is satisfied. Here, the nozzle array direction DN is the arrangement direction of the plurality of nozzles N when viewed from above the base 210. The first line segment L1 is an imaginary line segment connecting the head 3a and the base 210 during the printing operation of step S3 when viewed from above the base 210. The second line segment L2 is an imaginary line segment connecting the head 3a and the base 210 during the covering operation of step S6 when viewed from above the base 210.

[0114] When angles θ1, θ2, and θ3 satisfy the relationship described above, compared to the case where the yaw angle of head 3a is equal during the execution of the covering action in step S6 and the printing action in step S3, the rotation of joint 230_6 can be reduced when head 3a moves between the execution positions of the covering action in step S6 and the printing action in step S3.

[0115] In the 3D printing apparatus 1, it is preferable that when the two positions traversed by the head 3a during the printing operation in step S3 are designated as first position P1 and second position P2, the pitch angles at the first position P1 and the second position P2 of the head 3a are different from each other. In this case, even if the printing surface of the workpiece W is curved or the like, the posture of the head 3a relative to the object portion of the printing surface can be kept fixed. Therefore, it has the advantage of easily improving image quality regardless of the shape of the printing surface of the workpiece W.

[0116] Preferably, the printing action in step S3 includes changing the position of the head 3a relative to the workpiece W while maintaining the yaw angle and tilt angle of the head 3a at fixed values. In this case, it is possible to reduce the unevenness of ink density ejected from the head 3a onto the workpiece W during the execution of the printing action in step S3. As a result, it has the advantage of easily improving image quality.

[0117] Furthermore, as described above, the stereolithography printing apparatus 1 also performs the first movement action of step S2. In the first movement action of step S2, the robotic arm 2 moves its head 3a during the period from the end of the covering action in step S6 to the start of the printing action in step S3. Therefore, the transition from the covering action in step S6 to the printing action in step S3 can be implemented through the first movement action of step S2.

[0118] Furthermore, the amount of rotation of joint 230_6 during the execution of the first movement action in step S2 is smaller than the amount of rotation of joint 230_1 during the execution of the first movement action in step S2. Here, joint 230_1 is an example of a "first joint" and is the joint 230 closest to the base 210 among a plurality of joints 230. Joint 230_6 is an example of a "second joint" and is the joint 230 furthest from the base 210 among a plurality of joints 230. When joint 230_6 rotates, compared to the case where joint 230_1 rotates, it is easier for wiring components such as the supply tube 10a and drive wiring 11a associated with the head 3a to twist. Therefore, by making the rotation of joint 230_6 during the execution of the first movement in step S2 smaller than that of joint 230_1 during the execution of the first movement in step S2, the twisting of the wiring component in the first movement of step S2 can be reduced.

[0119] Furthermore, as described above, the stereolithography printing apparatus 1 also performs the second movement action of step S5. In the second movement action of step S5, the robotic arm 2 moves its head 3a during the period from the end of the printing action in step S3 to the start of the covering action in step S6. Therefore, the transition from the printing action in step S3 to the covering action in step S6 can be implemented through the second movement action of step S5.

[0120] Furthermore, the rotation amount of joint 230_6 during the execution of the second movement in step S5 is smaller than the rotation amount of joint 230_1 during the execution of the second movement in step S5. Therefore, the twisting of the wiring type in the second movement of step S5 can be reduced in the same way as the first movement in step S2 described above.

[0121] The change in the yaw angle of the head unit 3a during the execution of the first moving action in step S2 or the second moving action in step S5 is preferably 45° or more, and more preferably 90° or more. Thus, the greater the change in yaw angle, the further the position of the head unit 3 is from the position of the workpiece W during the execution of the covering action in step S6. Therefore, interference of the head unit 3 during operations such as setting or removing the workpiece W and adjusting the position of the workpiece W during the execution of the covering action can be suppressed.

[0122] Furthermore, as mentioned above, when the covering action in step S6 ends, the head 3a separates from the cover portion 4b along the normal direction of the nozzle surface F. Therefore, since the situation where the nozzle surface F remains in contact with the cover portion 4b while moving at the end of the covering action in step S6 is reduced, contamination of the nozzle surface F caused by ink adhering to the cover portion 4b is prevented.

[0123] From the same perspective, as mentioned above, at the start of the covering action in step S6, the head 3a approaches the cover portion 4b along the normal direction of the nozzle surface F. Therefore, since the situation where the nozzle surface F remains in contact with the cover portion 4b during movement at the start of the covering action in step S6 is reduced, contamination of the nozzle surface F caused by ink adhering to the cover portion 4b is prevented.

[0124] Furthermore, as mentioned above, it is preferable that the nozzle surface F is horizontal during the execution of the covering action in step S6. In this case, since the meniscus of the ink in each nozzle N is stabilized during the execution of the covering action in step S6, the ink near each nozzle N is less likely to become viscous compared to the case where the nozzle surface F is tilted relative to the horizontal plane.

[0125] As described above, the stereolithography printing apparatus 1 of this embodiment also includes a force application mechanism 4b3. During the execution of the covering action in step S6, the force application mechanism 4b3 applies force to the cover portion 4b toward the nozzle surface F. Therefore, the cover portion 4b can be stably and tightly attached to the nozzle surface F during the execution of the covering action in step S6.

[0126] Furthermore, as described above, the stereolithography printing apparatus 1 of this embodiment also includes a suction mechanism 4d. During the covering action in step S6, the suction mechanism 4d reduces pressure on the space formed between the cover portion 4b and the nozzle surface F. Therefore, ink that has become viscous or cured near the nozzle N can be removed by the action of the suction mechanism 4d.

[0127] Furthermore, as described above, the three-dimensional printing apparatus 1 of this embodiment also includes a wiping unit 4e. The wiping unit 4e is disposed adjacent to the cover 4b and wipes the nozzle surface F. Therefore, ink adhering to the nozzle surface F can be removed by the action of the wiping unit 4e. In particular, since the wiping unit 4e is disposed adjacent to the cover 4b, maintenance using both the cover 4b and the wiping unit 4e can be effectively implemented.

[0128] 2. Variations

[0129] The methods illustrated above can be modified in a variety of ways. Specific modifications applicable to the methods described above are illustrated below. Furthermore, two or more methods arbitrarily selected from the following examples can be appropriately combined without contradiction.

[0130] 2-1. Variation Example 1

[0131] While the structure of a six-axis vertical multi-axis robotic arm has been exemplified in the foregoing description, it is not limited to this structure. The robotic arm can be, for example, a vertical multi-axis robotic arm with axes other than six, or a horizontal multi-axis robotic arm. Furthermore, the arm portion of the robotic arm may have a telescopic mechanism in addition to a rotating portion consisting of a rotating mechanism. However, from the viewpoint of balancing print quality during printing operations with the degrees of freedom of the robotic arm's movement during non-printing operations, it is preferable that the robotic arm be a multi-axis robotic arm with six or more axes.

[0132] 2-2. Variation Example 2

[0133] Although the methods described above illustrate a structure for fixing the head relative to the robotic arm using screws or similar fastening mechanisms, this approach is not limited to that structure. For example, the head can also be fixed relative to the robotic arm by gripping it with a gripping mechanism such as a gripper that is mounted as an end effector of the robotic arm.

[0134] 2-3. Variation Example 3

[0135] Although the foregoing description illustrates a structure that uses one type of ink for printing, it is not limited to that structure and can also be applied to structures that use two or more types of ink for printing.

[0136] 2-4. Variation Example 4

[0137] The application of the three-dimensional printing apparatus of the present invention is not limited to printing. For example, the three-dimensional printing apparatus that sprays a solution of color material can be used as a manufacturing apparatus for forming color filters for liquid crystal display devices. Furthermore, the three-dimensional printing apparatus that sprays a solution of conductive material can be used as a manufacturing apparatus for forming wiring or electrodes for wiring substrates. In addition, the three-dimensional printing apparatus can also be used as a spray dispenser for applying liquids such as adhesives to workpieces.

[0138] Symbol Explanation

[0139] 1…3D printing apparatus; 2…robotic arm; 2a…arm drive mechanism; 3…head unit; 3a…head; 3b…pressure regulating valve; 3c…curing light source; 3d…distance sensor; 3e…switch circuit; 3f…support body; 4…maintenance unit; 4a…housing; 4b…cover; 4b1…cover; 4b2…guide; 4b3…force application mechanism; 4c…support platform; 4c1…top surface; 4c2…foot; 4d…suction mechanism; 4d2…pressure reducing pump; 4e…wiping unit; 4e1…wiper; 4e2…support body; 5…controller; 5a…storage circuit; 5b…processing Circuit; 6…Control module; 6a…Timing signal generation circuit; 6b…Power supply circuit; 6c…Control circuit; 6d…Drive signal generation circuit; 7…Computer; 10…Pipe section; 10a…Supply pipe; 11…Wiring section; 11a…Drive wiring; 210…Base; 220…Arm section; 221…Arm; 222…Arm; 223…Arm; 224…Arm; 225…Arm; 226…Arm; 230…Joint section (first rotating section; rotating section); 230_1…Joint section (rotating section); 230_2…Joint section (rotating section); 230_3…Joint section (rotating section); 230_4…Joint (Rotating Part); 230_5…Joint (Rotating Part); 230_6…Joint (Second Rotating Part); AX…Long Axis; CLK…Clock Signal; CNG…Exchange Signal; Com…Drive Signal; D1…Output; D3…Signal; DN…Nozzle Array Direction; DS…Scanning Direction; Da…Path Information; F…Nozzle Face; FX1…Fixed Position; FX2…Fixed Position; FX3…Fixed Position; FX4…Fixed Position; L1…First Segment; L2…Second Segment; LAT…Latch Signal; La…Nozzle Array; Lb…Nozzle Column; N… Nozzle; O1… Rotating axis; O2… Rotating axis; O3… Rotating axis; O4… Rotating axis; O5… Rotating axis; O6… Rotating axis; P1… First position; P2… Second position; PD… Drive pulse; PTS… Timing signal; RU… Movement path; S1… Step; S2… Step; S3… Step; S4… Step; S5… Step; S6… Step; S7… Step; SI… Control signal; Sk1… Control signal; VBS… Offset potential; VHV… Power supply potential; W… Workpiece; WF… Surface; dCom… Waveform specification signal; θ1… Angle; θ2… Angle.

Claims

1. A stereolithography apparatus characterized by, having: a head having a nozzle face provided with a plurality of nozzles that eject liquid; a robot arm having a base, and an arm portion that supports the head, and provided with a plurality of turning portions from the base to the arm portion, and changing the position of the head with respect to the base by turning of the turning portions; a cover portion that covers the nozzle face, the three-dimensional object printing apparatus performs a covering operation and a printing operation, wherein the covering operation is an operation of the robot arm to position the head at a position at which the nozzle face is covered by the cover portion, and the printing operation is an operation of the head to eject liquid to a workpiece while the robot arm changes the position of the head with respect to the workpiece to a position different from the position during the execution of the covering operation, when the amount of rotation of the head with respect to a reference attitude around an axis along the normal direction of the nozzle face is set as a yaw angle, the yaw angle of the head during the execution of the covering operation and the yaw angle of the head during the execution of the printing operation are different from each other, at the end of the execution of the covering operation, the head is separated from the cover portion along the normal direction of the nozzle face.

2. The three-dimensional object printing apparatus according to claim 1, wherein when two positions through which the head passes during the execution of the printing operation are set as a first position and a second position, the pitch angle of the head at the first position and the pitch angle of the head at the second position are different from each other.

3. The three-dimensional object printing apparatus according to claim 1 or 2, wherein the printing operation includes an operation of changing the position of the head with respect to the workpiece while maintaining the yaw angle and the roll angle of the head at a fixed value.

4. The three-dimensional object printing apparatus according to claim 1, wherein when the arrangement direction of the plurality of nozzles is set as a nozzle row direction, an imaginary line segment connecting the head during the execution of the printing operation and the base is set as a first line segment, the angle of the first line segment during the execution of the printing operation and the nozzle row direction is set as θ1, an imaginary line segment connecting the head during the execution of the covering operation and the base is set as a second line segment, the angle of the second line segment during the execution of the covering operation and the nozzle row direction is set as θ2, and the angle of the first line segment and the second line segment is set as θ3, the relationship of |θ1-θ2|<θ3 is satisfied in a plan view of the base.

5. The three-dimensional object printing apparatus according to claim 1, further performing a first movement operation, the first movement operation being an operation of the robot arm to move the head during a period from the end of the execution of the covering operation to the start of the execution of the printing operation. ​ In the plurality of turning portions, when a turning portion closest to the base portion is set as a first turning portion and a turning portion farthest from the base portion is set as a second turning portion, an amount of turning of the second turning portion across the execution of the first movement action is smaller than an amount of turning of the first turning portion across the execution of the first movement action.

6. The three-dimensional object printing apparatus according to claim 5, wherein a second movement action is further performed, the second movement action being an action of the robot arm moving the head during a period from an end of execution of the printing action to a start of execution of the covering action, an amount of turning of the second turning portion across the execution of the second movement action is smaller than an amount of turning of the first turning portion across the execution of the second movement action.

7. The three-dimensional object printing apparatus according to claim 6, wherein a change in a yaw angle of the head across the execution of the first movement action or the second movement action is 45° or more.

8. The three-dimensional object printing apparatus according to claim 7, wherein a change in a yaw angle of the head across the execution of the first movement action or the second movement action is 90° or more.

9. The three-dimensional object printing apparatus according to claim 1, wherein a suction mechanism that depressurizes a space formed between the cover portion and the nozzle face during execution of the covering action is further provided.

10. The three-dimensional object printing apparatus according to claim 1, wherein a wiper portion that is disposed adjacent to the cover portion and wipes the nozzle face is further provided.

11. The three-dimensional object printing apparatus according to claim 1, wherein a supply tube that supplies liquid to the head is further provided, the supply tube is disposed outside the arm portion.

12. A stereolithography apparatus characterized by, having: a head having a nozzle face provided with a plurality of nozzles that eject liquid; a robot arm having a base portion, and an arm portion that supports the head, and provided with a plurality of turning portions from the base portion to the arm portion, and the position of the head with respect to the base portion is changed by turning of the turning portions; a cover portion that covers the nozzle face, the three-dimensional object printing apparatus executes a covering action and a printing action, wherein the covering action is an action of the robot arm positioning the head at a position at which the nozzle face is covered by the cover portion, and the printing action is an action of the head ejecting liquid to a workpiece while the robot arm changes the position of the head with respect to the workpiece to a position different from the position during execution of the covering action, when a rotation amount of the head with respect to a reference attitude around an axis along a normal direction of the nozzle face is set as a yaw angle, the yaw angle of the head during execution of the covering action and the yaw angle of the head during execution of the printing action are different from each other, at the start of execution of the covering action, the head approaches the cover portion along the normal direction of the nozzle face.

13. A stereolithography apparatus characterized by comprising: having: a head having a nozzle face provided with a plurality of nozzles that eject liquid; a mechanical arm having a base portion, an arm portion that supports the head, and a plurality of turning portions provided from the base portion to the arm portion, and changing a position of the head with respect to the base portion by turning of the turning portions; a cover portion that covers the nozzle face, the three-dimensional object printing apparatus executes a covering operation and a printing operation, wherein the covering operation is an operation of the mechanical arm to position the head at a position at which the nozzle face is covered by the cover portion, and the printing operation is an operation of the head to eject liquid to a workpiece while the mechanical arm changes a position of the head with respect to the workpiece to a position different from a position during execution of the covering operation, when a rotation amount around an axis along a normal direction of the nozzle face with respect to a reference attitude of the head is set as a yaw angle, the yaw angle of the head during execution of the covering operation and the yaw angle of the head during execution of the printing operation are different from each other, the nozzle face during execution of the covering operation is horizontal.

14. A stereolithography apparatus characterized by, having: a head having a nozzle face provided with a plurality of nozzles that eject liquid; a mechanical arm having a base portion, an arm portion that supports the head, and a plurality of turning portions provided from the base portion to the arm portion, and changing a position of the head with respect to the base portion by turning of the turning portions; a cover portion that covers the nozzle face, the three-dimensional object printing apparatus executes a covering operation and a printing operation, wherein the covering operation is an operation of the mechanical arm to position the head at a position at which the nozzle face is covered by the cover portion, and the printing operation is an operation of the head to eject liquid to a workpiece while the mechanical arm changes a position of the head with respect to the workpiece to a position different from a position during execution of the covering operation, when a rotation amount around an axis along a normal direction of the nozzle face with respect to a reference attitude of the head is set as a yaw angle, the yaw angle of the head during execution of the covering operation and the yaw angle of the head during execution of the printing operation are different from each other, further having a force applying mechanism that applies a force to the cover portion toward the nozzle face during execution of the covering operation.

15. A stereolithography apparatus characterized by, having: a head having a nozzle face provided with a plurality of nozzles that eject liquid; a mechanical arm having a base portion, an arm portion that supports the head, and a plurality of turning portions provided from the base portion to the arm portion, and changing a position of the head with respect to the base portion by turning of the turning portions; a cover portion that covers the nozzle face, the three-dimensional object printing apparatus executes a covering operation and a printing operation, wherein the covering operation is an operation of the mechanical arm to position the head at a position at which the nozzle face is covered by the cover portion, and the printing operation is an operation of the head to eject liquid to a workpiece while the mechanical arm changes a position of the head with respect to the workpiece to a position different from a position during execution of the covering operation, When a rotation amount of the head around an axis in a normal line direction of the nozzle surface with respect to a reference posture of the head is set as a yaw angle, the yaw angle of the head during execution of the covering operation and the yaw angle of the head during execution of the printing operation are different from each other, a driving wiring that supplies an electric signal for driving the head to the head is further provided, the driving wiring is provided outside the arm portion.

16. A method of printing a three-dimensional object, the method comprising: The following components are used: a head having a nozzle surface provided with a plurality of nozzles that eject a liquid; a mechanical arm having a base portion and an arm portion that supports the head, and a plurality of turning portions provided from the base portion to the arm portion, and the position of the head with respect to the base portion is changed by turning of the turning portions; a cover portion that covers the nozzle surface, in the three-dimensional object printing method, a covering operation and a printing operation are executed, the covering operation is an operation in which the mechanical arm positions the head at a position at which the nozzle surface is covered by the cover portion, the printing operation is an operation in which the head ejects a liquid onto a workpiece while the mechanical arm changes the position of the head with respect to the workpiece to a position different from the position during execution of the covering operation, When a rotation amount of the head around an axis in a normal line direction of the nozzle surface with respect to a reference posture of the head is set as a yaw angle, the yaw angle of the head during execution of the covering operation and the yaw angle of the head during execution of the printing operation are different from each other, at the end of execution of the covering operation, the head is separated from the cover portion in the normal line direction of the nozzle surface.

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