Printing device

Abstract

The present disclosure provides a printing device that improves print quality in a printing device using a robot. The printing device has a head including a first nozzle row in which a plurality of nozzles that eject a first ink are arranged, and a second nozzle row in which a plurality of nozzles that eject a second ink are arranged, and a robot that changes the position and attitude of the head with respect to a workpiece, the robot having an arm portion having a tip end at which the head is supported, a base end, and a plurality of joints, and a base portion connected to the base end, the brightness of the second ink being lower than the brightness of the first ink, the distance between the tip end and the base end at a second timing at which the second ink is to be ejected from the second nozzle row to a predetermined position on the workpiece being smaller than the distance between the tip end and the base end at a first timing at which the first ink is to be ejected from the first nozzle row to the predetermined position.

Description

Technical Field

[0001] This disclosure relates to a printing apparatus. Background Technology

[0002] A printing apparatus using an inkjet method employing a robot such as a multi-jointed robot is known. For example, the apparatus described in Patent Document 1 includes a head that serves as an inkjet head and a robot that holds the head.

[0003] When printing with multiple colors of ink, generally, the printing head is equipped with multiple nozzle rows for each color of ink. Patent Document 1 does not describe the configuration of these multiple nozzle rows when printing with multiple colors of ink. In printing apparatuses that use a robot to move the printing head, when printing with multiple colors of ink, it is desirable to achieve an appropriate configuration of the multiple nozzle rows to obtain good print quality.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-215438 Summary of the Invention

[0005] To address the above-mentioned issues, one aspect of the printing apparatus disclosed herein includes: a head comprising a first nozzle array with a plurality of nozzles for ejecting a first ink and a second nozzle array with a plurality of nozzles for ejecting a second ink; a robot having an arm and a base, the arm having a tip, a base end, and a plurality of joints, the base being connected to the base end, the head being supported on the tip, the robot causing the position and orientation of the head relative to a workpiece to change, the brightness of the second ink being lower than the brightness of the first ink, and when a first timing is set for ejecting the first ink from the first nozzle array to a predetermined position on the workpiece, and a second timing is set for ejecting the second ink from the second nozzle array to the predetermined position, the distance between the tip and the base end under the second timing is less than the distance between the tip and the base end under the first timing.

[0006] Another aspect of the printing apparatus disclosed herein includes: a head comprising a first nozzle array of a plurality of nozzles for ejecting a first ink and a second nozzle array of a plurality of nozzles for ejecting a second ink; a robot having an arm and a base, the arm having a tip, a base end and a plurality of joints, the base being connected to the base end and the head being supported on the tip, the robot causing the head to change position and orientation relative to a workpiece, the brightness of the second ink being lower than that of the first ink, and the distance between the second nozzle array and the base end being longer than the distance between the first nozzle array and the base end. Attached Figure Description

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

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

[0009] Figure 3 This is a perspective view showing the outline structure of the head unit used in the first embodiment.

[0010] Figure 4 This diagram is used to explain the printing operation of the printing apparatus according to the first embodiment.

[0011] Figure 5 A diagram representing the state of the robot at the first timing point.

[0012] Figure 6 This diagram illustrates the distance between the tip and base of the robot's arm during the first timing.

[0013] Figure 7 A diagram representing the state of the robot at the second timing.

[0014] Figure 8 This diagram illustrates the distance between the tip and base of the robot's arm during the second timing.

[0015] Figure 9 A graph showing the relationship between the distance between the top and bottom of the arm and the rotation angle of the robot's joints.

[0016] Figure 10 This is a diagram used to illustrate the printing operation in the second embodiment.

[0017] Figure 11 This is a block diagram illustrating the electrical structure of the printing apparatus according to the third embodiment.

[0018] Figure 12 This is a perspective view showing the outline structure of the head unit used in the third embodiment.

[0019] Figure 13 This diagram is used to explain the printing operation of the printing apparatus according to the third embodiment.

[0020] Figure 14 This is a perspective view showing the outline structure of the head unit used in the fourth embodiment.

[0021] Figure 15 This is a diagram used to illustrate the movement path of the head in the fourth embodiment. Detailed Implementation

[0022] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the dimensions and scales of the parts in the drawings may differ appropriately from actual dimensions, and some parts may be shown schematically for ease of understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description.

[0023] For simplicity, the following description uses intersecting X-axis, Y-axis, and Z-axis as appropriate. Furthermore, in the following description, one direction along the X-axis is the X1 direction, and the opposite direction is the X2 direction. Similarly, opposite directions along the Y-axis are the Y1 and Y2 directions. Additionally, opposite directions along the Z-axis are the Z1 and Z2 directions.

[0024] Here, the X, Y, and Z axes correspond to the coordinate axes of a world coordinate system set in the space containing the robot 2 (described later). Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. Within this world coordinate system, a base coordinate system is established based on the position of the base 210 of the robot 2 (described later) through calibration. For convenience, the following example illustrates the use of the world coordinate system as the robot coordinate system to control the movements of the robot 2.

[0025] Additionally, the Z-axis does not have to be vertical. Furthermore, while 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 can intersect each other at an angle between 80° and 100°.

[0026] 1. First Implementation Method

[0027] 1-1. Overview of Printing Equipment

[0028] Figure 1 The diagram shows a perspective view of the printing apparatus 1 according to the first embodiment. The printing apparatus 1 is an apparatus that performs printing on the surface of a workpiece W by inkjet printing.

[0029] The workpiece W has a surface WF that becomes the object of printing. Figure 1 In the example shown, the workpiece W is a cuboid, and surface WF is a plane. During printing, the workpiece W is supported as needed, for example by a predetermined mounting platform, robotic arm, or conveyor belt. Furthermore, the shape or size of the workpiece W or surface WF is not limited to... Figure 1The examples shown are arbitrary. For instance, the surface WF can have curved or buckled portions, and the workpiece W can be a thin sheet material such as paper or cloth. Furthermore, the position or orientation of the workpiece W or the surface WF during printing is not limited to any particular type, as long as printing is feasible. Figure 1 The example shown is arbitrary.

[0030] like Figure 1 As shown, the printing apparatus 1 includes: a robot 2, a head unit 3, a controller 5, a piping unit 10, and a wiring unit 11. These components will now be briefly described in turn.

[0031] Robot 2 is the robot that changes the position and orientation of head unit 3 in the world coordinate system. Figure 1 In the example shown, robot 2 is a so-called six-axis vertical jointed robot.

[0032] like Figure 1 As shown, robot 2 has a base 210 and an arm 220.

[0033] The base 210 is a pedestal 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 threaded fastening or the like. However, 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 examples shown could also be surfaces such as walls, ceilings, or movable trolleys.

[0034] Arm 220 is a six-axis robotic arm having a base end EB mounted on a base 210 and a tip ET that allows for three-dimensional changes in position and orientation relative to the base end EB. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, also referred to as links. These arms are connected together in the order of arms 221, 222, 223, 224, 225, and 226.

[0035] 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.

[0036] Joints 230_1 to 230_6 are mechanisms that rotatably connect one of two adjacent components of the base 210 and arms 221 to 226 relative to the other. In the following text, joints 230_1 to 230_6 will sometimes be referred to as "joint 230". Here, the base end EB is one end of the arm 220 whose position in the basic coordinate system does not change even when joint 230 rotates, and the tip ET is the other end of the arm 220 whose position in the basic coordinate system changes due to rotation of joint 230_6. The base end EB can be defined, for example, as the intersection of the boundary between the base 210 and arm 221 and the rotation axis O1. Furthermore, the tip ET can be defined, for example, as the intersection of the end face of arm 226 furthest from arm 225 or the surface extending from that end face and the rotation axis O6.

[0037] Although Figure 1 Although not illustrated, joints 230_1 to 230_6 are each equipped with a drive mechanism that rotates one of the corresponding two components relative to the other. This drive mechanism may include, for example, a motor that generates the driving force for the rotation, a speed 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 [described later]... Figure 2 The arm drive mechanism 2a shown is illustrated.

[0038] 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.

[0039] Furthermore, regarding these rotating axes, the term "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, the term "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°.

[0040] On the top end ET of the arm 220 of the robot 2 described above, a head unit 3 is installed as an end effector in a fixed state by means of thread fixing or the like.

[0041] Head unit 3 is an assembly having a head 3a that ejects multiple inks of different brightness toward the workpiece W. In this embodiment, head unit 3, in addition to the head 3a, also includes a pressure regulating valve 3b and an energy emission section 3c. Further details regarding head unit 3 will be provided later. Figure 3 Let me explain.

[0042] In this embodiment, a case is illustrated using four inks: a first ink, a second ink, a third ink, and a fourth ink, each with different brightness levels. The brightness of these inks, from highest to lowest, is listed as the first ink, the third ink, the fourth ink, and the second ink. In full-color printing, typically, these four inks are yellow ink, magenta ink, cyan ink, and black ink. In this case, the first ink is yellow ink, the second ink is black ink, and one of the third and fourth inks is magenta ink, while the other is cyan ink. Here, the brightness can, for example, conform to CIE L as specified by the International Commission on Illumination (CIE). * a * b * The color space is defined by its luminance. In this embodiment, CIE L... * a * b * The brightness values ​​for the color space are 83 for yellow ink, 54 for magenta ink, 56 for cyan ink, and 11 for black ink. Furthermore, the brightness values ​​of inks can be obtained, for example, by applying the ink to a medium such as printing paper to create a predetermined color mark, and then measuring the color mark using a colorimeter. Here, the comparison of the brightness values ​​of multiple inks can be performed by creating color marks for each of the multiple inks on the same medium using the same amount of ink, and then comparing the values ​​obtained by measuring the color marks of the multiple inks.

[0043] Such inks are, for example, liquid media in which color materials such as dyes or pigments are dissolved or dispersed in a solvent. While each ink can be any of the following: water-based inks that dissolve color materials such as dyes or pigments in aqueous solvents, curable inks using curable resins such as UV-curable inks, and solvent-based inks that dissolve color materials such as dyes or pigments in organic solvents, curable inks are preferred. Although curable inks are not particularly limited, and can be, for example, any of the following: thermosetting, photocurable, radiation-curable, and electron beam-curable inks, photocurable inks such as UV-curable inks are preferred. Furthermore, inks containing color materials are not limited to yellow inks, magenta inks, blue-green inks, and black inks; for example, white inks, gray inks, light blue-green inks, and light magenta inks can also be used.

[0044] The head unit 3 is connected to a piping section 10 and a wiring section 11. The piping section 10 is a piping assembly that supplies ink from an ink tank (not shown) to the head unit 3. The wiring section 11 is a wiring or wiring assembly that supplies electrical signals for driving the head 3a.

[0045] Controller 5 is a robot controller that controls the drive of robot 2. The following is based on... Figure 2 The electrical structure of the printing apparatus 1 will be described in a manner that includes a detailed description of the controller 5.

[0046] 1-2. Electrical Structure of the Printing Equipment

[0047] Figure 2 Here is a block diagram illustrating the electrical structure of the printing apparatus 1 according to the first embodiment. Figure 2 The diagram shows the electrical structural elements within the structural elements of the printing apparatus 1. For example... Figure 2 As shown, in the printing apparatus 1, in addition to having the aforementioned Figure 1 In addition to the structural elements shown, it 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.

[0048] in addition, Figure 2 The various electrical structural elements shown can be appropriately divided, partially included in other structural elements, or integrally formed with other structural elements. For example, part or all of the function of controller 5 or control module 6 can be implemented by computer 7, or by other external devices such as PC (personal computer) connected to controller 5 via a network such as LAN (Local Area Network) or the Internet.

[0049] The controller 5 has the function of controlling the drive of the robot 2 and generating a signal D3 to synchronize the ink ejection action in the head unit 3 with the action of the robot 2.

[0050] The controller 5 has a storage circuit 5a and a processing circuit 5b.

[0051] 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 be included in the processing circuit 5b.

[0052] The storage circuit 5a stores path information Da. 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. Path information Da is generated, for example, using information obtained through direct instruction or online instruction, and CAD (computer-aided design) data representing the shape of the workpiece W. Path information Da is represented, for example, using coordinate values ​​from a base coordinate system or a world coordinate system. The path information Da can be input from the computer 7 into the storage circuit 5a.

[0053] The processing circuit 5b controls the movement of the arm drive mechanism 2a of the robot 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 CPUs (Central Processing Units). Alternatively, the processing circuit 5b may replace the CPU or include programmable logic devices such as FPGAs (Field-Programmable Gate Arrays) in addition to the CPU.

[0054] Here, the arm drive mechanism 2a is an assembly of the drive mechanisms of the aforementioned joints 230_1 to 230_6, and for each joint 230, it has a motor for driving the joint 230 and an encoder for detecting the rotation angle of the joint 230.

[0055] Processing circuit 5b performs inverse kinematics calculation, converting path information Da into motion quantities such as rotation angles and rotational speeds of each joint 230 of robot 2. Then, processing circuit 5b outputs control signals Sk1 based on the outputs D1 of each encoder from arm drive mechanism 2a, in a manner that makes the actual rotation angles and rotational speeds of each joint 230 the motion quantities based on the aforementioned calculation results of path information Da. Control signals Sk1 are signals used to control the drive of the motors of arm drive mechanism 2a. Here, control signals Sk1 are corrected by processing circuit 5b as needed, based on the output from a distance sensor (not shown).

[0056] Furthermore, the processing circuit 5b generates a signal D3 based on the output D1 from at least one of the plurality of encoders from the arm drive mechanism 2a. For example, the processing circuit 5b generates a trigger signal, including a timing pulse from the output D1 of one of the plurality of encoders, which is set to a predetermined value, as signal D3.

[0057] The control module 6 is a circuit that controls the ink ejection action of the independent nozzle N of the head unit 3 based on the signal D3 output from the controller 5 and the printing data Img 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.

[0058] 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 begins generating the timing signal PTS upon detection of signal D3. The timing signal PTS, for example, includes pulses defined based on output D1.

[0059] 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 a bias potential VBS. The bias potential VBS is supplied to the head unit 3. Furthermore, the power supply potential VHV is supplied to the drive signal generation circuit 6d.

[0060] The control circuit 6c generates the printing data signal SI, the waveform specification signal dCom, the latch signal LAT, the clock signal CLK, and the conversion 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.

[0061] The printing data 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 printing data signal SI specifies whether to supply the drive signal Com (described later) to the drive element based on printing data. This specification specifies, for example, whether ink is ejected from the nozzle corresponding to the drive element, or the amount of ink ejected from the nozzle. 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 conversion signal CNG are used in conjunction with the printing data signal SI and specify the timing of ink ejection from the nozzle by specifying the driving timing of the drive element. The clock signal CLK is a clock signal that is synchronized with the timing signal PTS and serves as a reference.

[0062] The control circuit 6c described above includes, for example, one or more processors such as CPUs. Alternatively, the control circuit 6c may replace a CPU or include programmable logic devices such as FPGAs in addition to a CPU.

[0063] The drive signal generation circuit 6d is a circuit that generates drive signals Com for driving the various 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 DA conversion circuit converts the waveform specification signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 6b, thereby generating the drive signal Com. Here, the signal of the waveform actually supplied to the drive element in the waveform contained in the drive signal Com 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.

[0064] Here, the switching circuit 3e is a circuit that includes a switching element 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 printed data signal SI.

[0065] The computer 7 has the function of supplying path information Da and other information to the controller 5, and the function of supplying printing data Img and other information to the control module 6. In addition to these functions, the computer 7 in this embodiment also has the function of controlling the drive of the energy emission unit 3c. The computer 7 is, for example, a desktop or laptop computer with programs that implement these functions installed.

[0066] 1-3. Structure of the head unit

[0067] Figure 3 Here is a perspective view showing the outline structure of the head unit 3 used in the first embodiment. For convenience, the following description will appropriately use the intersecting a-axis, b-axis, and c-axis. 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.

[0068] 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. The robot 2's movements change its relative position and orientation with respect to the world coordinate system or robot coordinate system. Figure 3 In the example shown, the c-axis is parallel to the aforementioned rotation axis O6. Furthermore, while the a-axis, b-axis, and c-axis are typically orthogonal, this is not a limitation; they can intersect at angles between 80° and 100°. Additionally, the tool coordinate system and the base coordinate system or robot coordinate system are established through calibration. Moreover, the tool coordinate system is set, for example, with the center of the ejection surface FN (described later) as the reference (TCP: tool center point).

[0069] As described above, head unit 3 includes a head 3a, a pressure regulating valve 3b, and an energy emission section 3c. These components are all... Figure 3 The support is shown as 3f with double-dotted lines. 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 the head unit 3; for example, it can be the arm 226, or it can be a position fixed relative to the base 210.

[0070] The support 3f is made of, for example, a metallic material and is a solid rigid body. Figure 3 In the example shown, the support body 3f is a flat plate extending in a direction orthogonal to axis a. In this embodiment, a head 3a is mounted on the surface of the support body 3f facing the a1 direction. On the other hand, an energy emission part 3c is mounted on the surface of the support body 3f facing the a2 direction. Furthermore, the shape of the support body 3f is not limited to... Figure 3 The example shown is arbitrary; for example, it could also be box-shaped, etc.

[0071] The aforementioned support body 3f is mounted on the arm 226. Therefore, the head 3a, pressure regulating valve 3b, and energy emission section 3c are supported on the arm 226 in a contained manner by the support body 3f. Thus, the relative positions of the head 3a, pressure regulating valve 3b, and energy emission section 3c with respect to the arm 226 are fixed. Figure 3 In the example shown, a pressure regulating valve 3b is positioned in the c1 direction relative to the head 3a. An energy emission section 3c is positioned in the a2 direction relative to the head 3a.

[0072] The head 3a has an ejection surface FN and a plurality of nozzles N that are open on the ejection surface FN. The ejection surface FN is a nozzle surface with the nozzles N open, for example, it is formed by the surface of a nozzle plate on a plate-shaped member made of a material such as silicon (Si) or metal, in which the nozzles N are provided as through holes.

[0073] exist Figure 3 In the example shown, the normal direction of the ejection surface FN is the c2 direction, and the plurality of nozzles N are divided into a first nozzle column L1, a second nozzle column L2, a third nozzle column L3, and a fourth nozzle column L4. These nozzle columns face the a1 direction and are arranged side by side with intervals between them in the order of the first nozzle column L1, the third nozzle column L3, the fourth nozzle column L4, and the second nozzle column L2.

[0074] The first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 are each a collection of multiple nozzles N arranged linearly along the b-axis. In this embodiment, the nozzle density of each nozzle N in each nozzle array along the b-axis is 300 npi (number of nozzles per inch). However, the invention is not limited to this; lower nozzle densities are possible, but from the viewpoint of print quality or efficiency, a nozzle density of 25 npi or higher is preferred. Furthermore, to achieve such a nozzle density, the nozzles N can be staggered in each nozzle array. Here, the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 eject different types of ink. Specifically, the first nozzle array L1 ejects a first ink. The second nozzle array L2 ejects a second ink. The third nozzle array L3 ejects a third ink. The fourth nozzle array L4 ejects a fourth ink. Since any ink is ejected in the c2 direction under ideal conditions, the c2 direction can also be expressed as the ejection direction.

[0075] Although not illustrated, 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 within the cavity corresponding to the piezoelectric element, thereby ejecting ink from the nozzle corresponding to that cavity. Such a head 3a is obtained, for example, by using an adhesive or the like to bond together multiple substrates, such as silicon substrates, that have been appropriately processed by etching. Alternatively, a heater that heats the ink within the cavity can be used instead of the piezoelectric element as the driving element for ejecting ink from the nozzles. With this structure, the presence or absence of ink ejection, or the amount of ink ejected, can be independently controlled for each nozzle N via the aforementioned control module 6, thus forming an image generated by the ink.

[0076] As described above, ink is supplied to the ink tank (not shown) via the supply pipe 10a in the head 3a above. Here, the pressure regulating valve 3b is located between the supply pipe 10a and the head 3a.

[0077] 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 aforementioned ink reservoir (not shown) 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 entering the nozzle N or ink overflowing from the nozzle N is prevented. Furthermore, the ink from the pressure regulating valve 3b is appropriately distributed to multiple locations in the head 3a via a branched flow path (not shown). Here, the ink from the ink reservoir (not shown) is transferred to the supply pipe 10a at a predetermined pressure using a pump or head difference, etc. Additionally, although not shown, the pressure regulating valve 3b has an ink flow path and a pressure regulating structure for each type of ink, so that the pressure of each of the four inks can be individually adjusted.

[0078] The energy emitting unit 3c emits energy such as light, heat, electron beams, or radiation to harden or cure the ink on the workpiece W. For example, if the ink has ultraviolet curability, the energy emitting unit 3c is composed of a light-emitting element such as an LED (light emitting diode) that emits ultraviolet light. In addition, the energy emitting unit 3c may also appropriately include optical components such as lenses for adjusting the direction or range of energy emission.

[0079] Here, the energy emitting section 3c includes an emission surface FL that emits the energy, and is arranged such that the emission surface FL faces the c2 direction. Furthermore, as described above, since the energy emitting section 3c is arranged in the a2 direction relative to the head 3a, the distance DL2 between the second nozzle array L2 and the emission surface FL is greater than the distance DL1 between the first nozzle array L1 and the emission surface FL.

[0080] Alternatively, the energy emission section 3c may not completely harden or cure the ink on the workpiece W. In this case, for example, the ink irradiated by the energy emission section 3c may be completely hardened or cured by the energy from a curing light source that is separately provided on the mounting surface of the base 210 of the robot 2.

[0081] 1-4. Printing Operation of the Printing Unit

[0082] Figure 4 This is a diagram used to explain the printing operation of the printing apparatus 1 according to the first embodiment. Figure 4 The example illustrates printing on a predetermined area RP of the surface WF of a workpiece W, which is positioned in the Y2 direction relative to the base 210 of the robot 2 when viewed along the Z-axis. Furthermore, the predetermined area RP is positioned in the X2 direction relative to the base 210 of the robot 2 when viewed along the Y-axis.

[0083] During the printing process, robot 2 causes the head 3a to change its position and orientation while simultaneously ejecting ink from the head 3a. The changes in the position and orientation of the head 3a are implemented based on path information Da. Thus, the head 3a maintains a predetermined orientation relative to the surface WF while moving along the movement path RU. Furthermore, the movement of the head 3a along the movement path RU can be performed multiple times each time different colors of ink are ejected, or all ink ejection can be performed in parallel during a single movement of the head 3a along the movement path RU.

[0084] The movement path RU is the path from position PS to position PE. Position PS is the position relative to the predetermined area RP in the X1 direction when viewed in the Z2 direction. Position PE is the position relative to the predetermined area RP in the X2 direction when viewed in the Z2 direction. During the period from position PS to the predetermined area RP, head 3a accelerates until it reaches a predetermined speed. During the period when head 3a is on the predetermined area RP, head 3a moves at a fixed speed at that predetermined speed. During the period from the predetermined area RP to position PE, head 3a decelerates in a manner that allows it to stop at position PE. Here, the predetermined area RP is the area that crosses from position PR1 to position PR2 along the movement path RU.

[0085] exist Figure 4 In the example shown, the movement path RU appears as a straight line when viewed in the Z2 direction. In this embodiment, during the execution of the printing action, the robot 2 moves the head 3a linearly along the movement path RU by manipulating four or more of the six joints 230, including joints 230_2, 230_3, and 230_5. Furthermore, the robot 2 moves the head 3a in a direction away from the base 210. Here, the aforementioned a1 direction is forward of the head 3a in the direction of movement. Therefore, the energy emission section 3c is located rearward relative to the head 3a in the direction of movement. Thus, energy from the energy emission section 3c can be applied to ink that has just been sprayed from the head 3a onto the surface WF.

[0086] Alternatively, the workpiece W can be positioned in the X2 direction relative to the base 210 of the robot 2, with its position aligned with the base 210 along the Y-axis. In this case, the movement path RU is a straight line along the X-axis when viewed in the Z2 direction. Furthermore, in this case, the robot 2 performs the printing action by moving three of the six joints 230. More specifically, during the printing action, the robot 2 sets the rotation axes of joints 230_2, 230_3, and 230_5 to be parallel to the Y-axis and moves these joints 230. Through the movement of these three joints 230, the head 3a can move stably along the movement path RU.

[0087] Furthermore, during the printing process, since the aforementioned a1 direction is forward in the direction of movement of the head 3a, these nozzle rows are arranged relative to the base 210 from near to far in the order of the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2. Therefore, when the first ink, the second ink, the third ink, and the fourth ink are ejected at the same position on the surface WF, the posture of the robot 2 at the timing of each ink ejection is different.

[0088] Here, regarding the timing of the ejection of the first ink, the second ink, the third ink, and the fourth ink at the same position on surface WF, the ejection timing of the first ink is referred to as "first timing", the ejection timing of the second ink is referred to as "second timing", the ejection timing of the third ink is referred to as "third timing", and the ejection timing of the fourth ink is referred to as "fourth timing". The following explanation will use the first timing and the second timing as examples.

[0089] Figure 5 Let represent the state of robot 2 under the first timing. Figure 6This diagram illustrates the distance DA between the tip ET and base EB of the arm 220 of robot 2 during the first timing. Figure 5 as well as Figure 6 The example illustrates a state where the timing for ejecting the first ink from the first nozzle array L1 to position PR2 is set to a first timing. Additionally, in... Figure 5 as well as Figure 6 For ease of explanation, the robot 2 and the head unit 3 are schematically illustrated.

[0090] like Figure 5 as well as Figure 6 As shown, under the first timing, the nozzle rows are arranged from near to far relative to the base 210 in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2. Therefore, the distances between these nozzle rows and the base end EB, from smallest to largest, are: DN1 between the first nozzle row L1 and the base end EB, DN3 between the third nozzle row L3 and the base end EB, DN4 between the fourth nozzle row L4 and the base end EB, and DN2 between the second nozzle row L2 and the base end EB. Furthermore, in this embodiment, distance DN1 is set as the shortest horizontal distance between the center of the first nozzle row L1 and the center of the base end EB. Similarly, distances DN2, DN3, and DN4 are respectively set as the shortest horizontal distances between the center of the corresponding nozzle row and the center of the base end EB. However, distances DN1, DN2, DN3, and DN4 can also be set simply as the straight-line distance between the center of each nozzle row and the center of the base end EB, regardless of direction.

[0091] Preferably, the arrangement of such nozzle arrays is maintained during the execution of the printing action targeting the predetermined area RP.

[0092] In this embodiment, as the head 3a moves away from the base 210, the angle θ1 between the extension direction of arm 224 and the extension direction of arm 222 increases with the movement of the head 3a during the printing operation. Conversely, the angle θ2 between the extension direction of arm 222 and the rotation axis O1 decreases with the movement of the head 3a during the printing operation.

[0093] Figure 7 Let be a diagram representing the state of robot 2 under the second timing. Figure 8 This is a diagram illustrating the distance between the tip ET and the base EB of the arm 220 of robot 2 during the second timing. Figure 7 as well as Figure 8 The example illustrates a state where the timing for ejecting the second ink from the second nozzle array L2 to position PR2 is set to the second timing. Additionally, in... Figure 7 as well as Figure 8For ease of explanation, the robot 2 and the head unit 3 are schematically illustrated.

[0094] like Figure 7 as well as Figure 8 As shown, under the second timing, similarly to the first timing, the nozzle rows are arranged relative to the base 210 from near to far in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2. Therefore, the distances between these nozzle rows and the base EB, from smallest to largest, are: DN1 between the first nozzle row L1 and the base EB, DN3 between the third nozzle row L3 and the base EB, DN4 between the fourth nozzle row L4 and the base EB, and DN2 between the second nozzle row L2 and the base EB.

[0095] However, the distance DN1 under the second timing is less than the distance DN1 under the first timing. The difference between these distances DN1 is the same as the distance between the first nozzle array L1 and the second nozzle array L2. Similarly, the distance DN2 under the second timing is less than the distance DN2 under the first timing. The distance DN3 under the second timing is less than the distance DN3 under the first timing. The distance DN4 under the second timing is less than the distance DN4 under the first timing.

[0096] Based on the relationship between the distances DN1, DN2, DN3, and DN4 under the second timing and the distances DN1, DN2, DN3, and DN4 under the first timing, the distance DA between the top end ET and the base end EB of the arm 220 under the second timing is less than the distance DA under the first timing.

[0097] Here, the arm 220 under the second timing is in a contracted state compared to the arm 220 under the first timing. Therefore, the angle θ1 under the second timing is smaller than the angle θ1 under the first timing. Furthermore, the angle θ2 under the second timing is larger than the angle θ2 under the first timing.

[0098] Figure 9 Let be a graph showing the relationship between the distance DA between the tip ET and the base EB of the arm 220 and the rotation angle θ of the joint 230 of the robot 2. Figure 9 The rotation angle θ is either angle θ1 or angle θ2 mentioned above. Figure 9 The diagram illustrates the relationship between distance DA and rotation angle θ when the rotation axes O2, O3, and O5 are kept parallel to each other, and the rotation axes O1 and O6 are kept parallel to the Z-axis, and when these joints 230 are actuated. Here, an example is shown where the distance between rotation axis O3 and the tip ET is equal to the distance between rotation axis O3 and the base EB. Figure 9Regarding the distance DA, the distance DA in the most contracted state of arm 220 is set to 0, and the distance DA in the most extended state of arm 220 is set to 1. Additionally, in Figure 9 For simplicity, the limits of the range of motion of joint 230 have not been considered.

[0099] Joint 230 may become a source of vibration for arm 220. Generally, joint 230 is more prone to vibration when its rotational speed changes (increases or decreases) compared to when it is at a standstill or at a fixed speed. Furthermore, once vibration occurs at joint 230, suppressing it is difficult. The vibration generated at joint 230 is transmitted to head 3a via arm 220. As a result, head 3a vibrates. If head 3a vibrates, its actual movement path deviates from the ideal path, leading to a decrease in print quality.

[0100] like Figure 9 As shown, the greater the distance DA, the greater the angle θ1. Conversely, the greater the distance DA, the smaller the angle θ2. Here, although the individual changes in angle θ1 and angle θ2 per unit length of distance DA are roughly constant in the range of 0 to 0.8, they increase as distance DA increases when it exceeds 0.8.

[0101] Therefore, when performing a continuous movement from a state where the distance DA is relatively small and the arm 220 is contracted to a state where the distance DA is relatively large and the arm 220 is extended, and when the distance DA changes at a constant speed, although the rotational speed of the joint 230 is initially roughly constant, the change in the rotational speed of the joint 230 increases as it approaches the state where the arm 220 is extended. Therefore, the state where the distance DA is relatively large and the arm 220 is extended is more prone to joint 230 vibration compared to the state where the distance DA is relatively small and the arm 220 is contracted. Therefore, at the second timing when the distance DA is relatively small, the vibration of the head 3a is more easily suppressed compared to the first timing.

[0102] Here, during the period when head 3a scans along the movement path RU on the predetermined area RP, the period during which head 3a ejects the first ink from the first nozzle array L1 to the predetermined area RP is defined as the first period. Furthermore, during the period when head 3a scans along the movement path RU on the predetermined area RP, the period during which head 3a ejects the second ink from the second nozzle array L2 to the predetermined area RP is defined as the second period. The first period includes a first timing, and the second period includes a second timing. Here, as described above, the distance DA under the second timing is less than the distance DA under the first timing, and like from... Figure 9 As understood from the graph, when ink is ejected onto the same predetermined area RP during the first and second periods, the total rotation of the multiple joints 230 during the second period is less than the total rotation of the multiple joints 230 during the first period. Furthermore, the first and second periods may overlap or not overlap. That is, the ejection of the first ink from the first nozzle array and the ejection of the second ink from the second nozzle array can be performed simultaneously in a single scan of the first 3a, or they can be performed separately, with the first ink ejected from the first nozzle array in the first scan of the first 3a and the second ink ejected from the second nozzle array in the second scan of the first 3a.

[0103] As described above, the printing apparatus 1 includes a head 3a and a robot 2 that changes the position and orientation of the head 3a relative to the workpiece W. Here, the head 3a includes a first nozzle array L1 with multiple nozzles N for ejecting a first ink and a second nozzle array L2 with multiple nozzles N for ejecting a second ink. The robot 2 has an arm 220 with a tip ET, a base EB, and multiple joints 230; and a base 210 connected to the base EB, on which the head 3a is supported. The brightness of the second ink is lower than that of the first ink.

[0104] Based on this, when the timing for ejecting the first ink from the first nozzle array L1 to a predetermined position PR2 on the workpiece W is set as the first timing, and the timing for ejecting the second ink from the second nozzle array L2 to the predetermined position PR2 is set as the second timing, the distance DA between the tip ET and the base EB under the second timing is less than the distance DA between the tip ET and the base EB under the first timing.

[0105] In the printing apparatus 1 described above, since the brightness of the second ink is lower than that of the first ink, the spraying error of the second ink relative to the workpiece W is more noticeable compared to the spraying error of the first ink relative to the workpiece W. That is, compared to the first ink, the second ink is more likely to cause a decrease in print quality due to the spraying error relative to the workpiece W. Therefore, in order to improve print quality, the distance DA at the second timing is made smaller than the distance DA at the first timing.

[0106] To be more specific, by making the distance DA under the second timing shorter than the distance DA under the first timing, the torque centered on the base end EB of the arm 220 under the second timing is less than the torque centered on the base end EB of the arm 220 under the first timing. Therefore, under the second timing, vibration is less likely to occur at the tip ET of the arm 220 and even in the head 3a compared to the first timing. As a result, under the second timing, the spraying error of the second ink relative to the workpiece W can be reduced compared to the first timing.

[0107] Furthermore, it is shown that as the distance DA increases, the rotation of joint 230 per unit movement distance of head 3a increases. Therefore, the larger the distance DA, the easier it is to generate vibration of head 3a accompanied by the drive of joint 230. Therefore, making the distance DA in the second timing period shorter than the distance DA in the first timing period will also have the effect of reducing the vibration of head 3a accompanied by the drive of joint 230.

[0108] On the other hand, although vibration is more likely to occur in the first 3 years under the first timing compared to the second timing, the first ink is used because the spraying error is less noticeable compared to the second ink.

[0109] As described above, by improving the spraying accuracy of the second ink (whose spraying error is more noticeable) compared to the first ink (whose spraying error is insignificant), the overall print quality degradation caused by the spraying error of the ink relative to the workpiece W can be reduced. Therefore, compared to a structure where the distance DA at the second timing is greater than or equal to the distance DA at the first timing, print quality can be improved.

[0110] Furthermore, as mentioned above, in each of the first and second timing periods, the distance DN2 between the second nozzle array L2 and the base end EB is greater than the distance DN1 between the first nozzle array L1 and the base end EB. Therefore, the distance DA in the second timing period can be shorter than the distance DA in the first timing period. In addition, regardless of the first and second timing periods, by making the distance DN2 longer than the distance DN1, the distance DA during printing performed by the second nozzle array L2 can be shorter than the distance DA during printing performed by the first nozzle array L1.

[0111] Furthermore, as described above, during the periods when the robot 2 scans the predetermined area RP on the workpiece W, including the predetermined position PR2, while simultaneously ejecting the first ink from the first nozzle array L1, and during the periods when the robot 2 scans the predetermined area RP while simultaneously ejecting the second ink from the second nozzle array L2, the distance DN2 between the second nozzle array L2 and the base end EB is maintained to be greater than the distance DN1 between the first nozzle array L1 and the base end EB. Therefore, throughout the entire printing period, the distance DA at the second timing can be made shorter than the distance DA at the first timing.

[0112] Furthermore, as described above, the head 3a also includes a third nozzle array L3, which consists of multiple nozzles N arranged to eject a third ink. The brightness of the third ink is lower than that of the first ink but higher than that of the second ink. Based on this, at each of the first and second timing intervals, the distance DN3 between the third nozzle array L3 and the base end EB is greater than the distance DN1 between the first nozzle array L1 and the base end EB, but less than the distance DN2 between the second nozzle array L2 and the base end EB. Therefore, even when a third ink is used in addition to the first and second inks, the reduction in print quality caused by ink ejection error relative to the workpiece W can be reduced.

[0113] In this embodiment, as described above, the first 3a includes a first nozzle array L1, a second nozzle array L2, a third nozzle array L3, and a fourth nozzle array L4 as multiple nozzle arrays for ejecting ink. Here, the ink ejected from the nozzle array that is farther from the base end EB among any two selected nozzle arrays has a lower brightness than the ink ejected from the nozzle array that is closer to the base end EB. That is, the multiple nozzle arrays are configured such that the greater the distance between them and the base end EB, the lower the brightness of the ink ejected from the nozzle array. Therefore, when using multiple inks, the reduction in print quality caused by ink drop error relative to the workpiece W can be appropriately reduced.

[0114] Furthermore, as described above, the printing apparatus 1 also has an energy emission section 3c. The energy emission section 3c is supported by a top end ET and includes an emission surface FL that emits energy to cure the first ink and the second ink respectively.

[0115] Based on this, the distance DL2 between the second nozzle array L2 and the emission surface FL is greater than the distance DL1 between the first nozzle array L1 and the emission surface FL. Therefore, the amount of second ink adhering to the emission surface FL can be reduced compared to the amount of first ink. Here, since the brightness of the second ink is lower than that of the first ink, the second ink absorbs energy from the emission surface FL more readily than the first ink. Therefore, reducing the amount of second ink adhering to the emission surface FL has the effect of suppressing the decrease in the irradiation efficiency of energy irradiating various inks from the emission surface FL, or reducing the frequency of maintenance such as cleaning the emission surface FL. Furthermore, since the first ink absorbs energy from the emission surface FL less readily than the second ink, even if the amount of first ink adhering to the emission surface FL increases, compared to the case where the second ink is adhering to the emission surface FL, it is less likely to cause problems such as a decrease in the irradiation efficiency of energy irradiating various inks from the emission surface FL, or an increase in the frequency of maintenance such as cleaning the emission surface FL.

[0116] Furthermore, as described above, a first period and a second period are defined regarding the period during which the head 3a scans along the predetermined region RP on the workpiece W, including the predetermined position PR2. The first period is the period during which the first ink is ejected from the first nozzle array L1 into the predetermined region RP. The second period is the period during which the second ink is ejected from the second nozzle array L2 into the predetermined region RP. Based on this, the total amount of rotation of the plurality of joints 230 during the second period is less than the total amount of rotation of the plurality of joints 230 during the first period. Therefore, the vibration of the head 3a during the second period can be made less than the vibration of the head 3a during the first period.

[0117] Furthermore, as mentioned above, the first ink is the brightest ink among those sprayed from the beginning 3a. Therefore, it is possible to appropriately improve the print quality.

[0118] As described above, in this embodiment, the first ink is yellow ink. Generally, among the various colors of ink used in full-color printing, yellow ink is the brightest. Therefore, by setting yellow ink as the first ink, the print quality during full-color printing can be appropriately improved. Furthermore, in structures using five or more inks, white ink is sometimes used as the brightest ink. In this case, the first ink can also be white ink.

[0119] Furthermore, as mentioned above, the second ink is the ink with the lowest brightness among the inks sprayed from the first 3a. In this case, the print quality can be appropriately improved.

[0120] As described above, in this embodiment, the second ink is black ink. Generally speaking, black ink is the ink with the lowest brightness among the various colors of ink used in full-color printing and the like. Therefore, by setting black ink as the second ink, the printing quality of full-color printing and the like can be appropriately improved.

[0121] Furthermore, as described above, in the first 3a, a plurality of nozzle rows for ejecting ink are included, comprising a first nozzle row L1, a second nozzle row L2, a third nozzle row L3, and a fourth nozzle row L4. Preferably, the first nozzle row L1 and the second nozzle row L2 are the two nozzle rows arranged furthest apart from each other among the plurality of nozzle rows. In this case, compared to a structure where the other nozzle rows are the first nozzle row L1 and the second nozzle row L2, print quality can be improved.

[0122] 2. Second Implementation Method

[0123] The second embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0124] Figure 10 This diagram illustrates the printing operation in the second embodiment. In this embodiment, everything is the same as in the first embodiment except for the predetermined region RP. Although the first embodiment illustrates a method where the distances DN1 to DN4 between each nozzle row and the base EB remain unchanged during the printing operation, this relationship can also vary.

[0125] In this embodiment, the printing area PR is extended in the X1 direction compared to the first embodiment. Here, when the predetermined area RP is observed along the Z-axis, it is divided into area RP1 and area RP2 by an imaginary straight line YB that passes through the base end EB and is orthogonal to the scanning direction of the head 3a along the movement path RU.

[0126] exist Figure 10 In the example shown, when viewed along the Z-axis, since the movement path RU is parallel to the X-axis, the straight line YB is parallel to the Y-axis. Region RP1, when viewed along the Z-axis, is located in the X1 direction relative to the straight line YB. Conversely, region RP2, when viewed along the Z-axis, is located in the X2 direction relative to the straight line YB.

[0127] When printing is performed while the head 3a moves along the movement path RU in the X2 direction relative to such a predetermined area RP from position PS to position PE, ink ejection from the first nozzle array L1 begins at position PR1 within area RP1 and stops at position PR2 within area RP2. Here, the arrangement order of the nozzle arrays along the X-axis is maintained throughout the entire printing period. Therefore, the size relationship of distances DN1 to DN4 changes midway through the printing period.

[0128] More specifically, when the tip ET is located in region RP2, similarly to the first embodiment, the distances between each nozzle row and the base EB satisfy the relationship DN2 > DN1. Conversely, when the tip ET is located in region RP1, the distances between each nozzle row and the base EB satisfy the relationship DN2 < DN1. In this way, at the point when the tip ET crosses the straight line YB, the relationship between distances DN1 to DN4 changes midway through the printing process.

[0129] From the perspective of improving print quality, it is not preferable to perform printing when the relationship is DN2 < DN1. Therefore, it is preferable that the predetermined area RP does not contain area RP1 where the relationship is DN2 < DN1. Alternatively, it is preferable that even if the predetermined area RP includes area RP1, the movement of the robot 2 is controlled in such a way that the relationship is DN2 > DN1.

[0130] However, printing can also be performed in a state where the DN2 < DN1 relationship. That is, there are also printing processes that allow for a DN2 < DN1 relationship. Here, when the predetermined area RP includes area RP1, from the viewpoint of balancing print quality and productivity, it is preferable that the length of area RP1 along the movement path RU is shorter than the length of area RP2 along the movement path RU. More preferably, the length of area RP1 along the movement path RU is less than half the length of area RP2 along the movement path RU. In this way, as long as the length of area RP1 along the movement path RU is short enough, even if there are periods when printing is performed in a DN2 < DN1 relationship, printing can still be performed in a DN2 > DN1 relationship, thus achieving a better balance between print quality and productivity.

[0131] 3. Third Implementation Method

[0132] The third embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0133] Figure 11 This is a block diagram illustrating the electrical structure of the printing apparatus 1A according to the third embodiment. In the printing apparatus 1A, except that a head unit 3A is provided instead of a head unit 3, everything else is configured in the same manner as the printing apparatus 1 of the first embodiment. The head unit 3A is configured in the same manner as the head unit 3, except that the arrangement of the energy emission section 3c is different and an optical sensor 3g is added.

[0134] Figure 12 This is a perspective view showing the outline structure of the head unit 3A used in the third embodiment. Figure 12 As shown, in the head unit 3A, an energy emission section 3c is arranged in the a1 direction relative to the head 3a, and an optical sensor 3g is arranged in the a2 direction. Here, the energy emission section 3c is mounted on the support body 3f via a component not shown. The optical sensor 3g is mounted on the surface of the support body f facing the a2 direction by means of threaded fixing or the like.

[0135] The optical sensor 3g is an optical displacement meter or imaging device, which includes a light-receiving part FS. The light-receiving part FS is an optical component that has a surface facing the c2 direction and is used, for example, to guide light into a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor.

[0136] For example, the controller 5 corrects the actual movement path of the head 3a based on the output from the optical sensor 3g. Additionally, the optical sensor 3g can also be connected to the computer 7. Furthermore, if the optical sensor 3g is an imaging device, the output from it can be used in other applications such as demonstrating the robot 2.

[0137] Figure 13 This is a diagram used to explain the printing operation of the printing apparatus 1A according to the third embodiment. Figure 13 In the middle, and the aforementioned Figure 4 Similarly, the case of printing a predetermined area RP of the surface WF of a workpiece W placed in the X2 direction relative to the base 210 of robot 2 when viewed along the Y-axis is illustrated.

[0138] In this embodiment, the robot 2 moves its head 3a toward the base 210. Here, the direction a2 is in front of the direction in which the head 3a moves. Therefore, similar to the first embodiment, the nozzle rows are arranged relative to the base 210 in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2, from near to far.

[0139] Furthermore, the energy emission section 3c is located rearward relative to the head 3a in the direction of movement of the head 3a. Therefore, energy from the energy emission section 3c can be irradiated relative to the ink that has just been sprayed from the head 3a onto the surface WF. Furthermore, the optical sensor 3g is located in front of the head 3a in the direction of movement of the head 3a.

[0140] Even according to the third embodiment described above, print quality can be improved. Although in this embodiment, the printing apparatus 1A has an energy emission section 3c, unlike the first embodiment, the distance DL2 between the second nozzle array L2 and the emission surface FL is smaller than the distance DL1 between the first nozzle array L1 and the emission surface FL. Therefore, the period from the timing of the second ink being ejected from the workpiece W to the timing of energy irradiation on the second ink can be shorter than the period from the timing of the first ink being ejected from the workpiece W to the timing of energy irradiation on the first ink. Here, since the brightness of the second ink is lower than that of the first ink, the bleeding of the second ink on the workpiece W is more noticeable compared to the first ink. Therefore, shortening the period from the timing of the second ink being ejected from the workpiece W to the timing of energy irradiation on the second ink has the effect of improving print quality. In addition, since the bleeding of the first ink on the workpiece W is less noticeable compared to the second ink, even if the period from the timing of the first ink being ejected from the workpiece W to the timing of energy irradiation on the first ink is longer, it is less likely to cause a decrease in print quality.

[0141] Furthermore, whether to set the relationship between distances DL1 and DL2 to either the first or third embodiment can be determined by considering factors such as the ease of bleeding of the second ink. For example, if the second ink is prone to bleeding, a structure where distance DL2 is smaller than distance DL1 can be used, as in this embodiment. Conversely, if the second ink is not prone to bleeding, a structure where distance DL2 is larger than distance DL1 can be used, as in the first embodiment.

[0142] Furthermore, in this embodiment, as described above, the printing apparatus 1A also includes an optical sensor 3g. The optical sensor 3g is supported on the top end ET and includes a light-receiving part FS.

[0143] Based on this, the distance DS2 between the second nozzle array L2 and the light-receiving section FS is greater than the distance DS1 between the first nozzle array L1 and the light-receiving section FS. Therefore, the amount of second ink adhering to the light-receiving section FS can be less than the amount of first ink. Here, since the brightness of the second ink is lower than that of the first ink, the second ink absorbs light directed towards the light-receiving section FS more readily than the first ink. Therefore, reducing the amount of second ink adhering to the light-receiving section FS has the effect of improving the light-receiving efficiency in the light-receiving section FS. Furthermore, since the first ink absorbs light directed towards the light-receiving section FS less readily than the second ink, even if the amount of first ink adhering to the light-receiving section FS increases, the problem of decreased light-receiving efficiency in the light-receiving section FS is less likely to occur.

[0144] 4. Fourth Implementation Method

[0145] The fourth embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0146] Figure 14 This is a perspective view showing the outline structure of the head unit 3B used in the fourth embodiment. In the printing apparatus 1B, except for the head unit B which replaces the head unit 3, everything else is configured in the same manner as the printing apparatus 1 of the first embodiment. Figure 14 As shown, the head unit 3B has two energy emission sections 3c. One of the energy emission sections 3c is positioned relative to the head 3a in the a1 direction, and the other energy emission section 3c is positioned relative to the head 3a in the a2 direction.

[0147] Figure 15 This diagram illustrates the movement paths RU1 and RU2 of head 3a in the fourth embodiment. Movement path RU1 is the path from position PS1 to position PE1. Robot 2 moves head 3a along movement path RU1 in a direction away from base 210. At this time, the direction a1 is forward in the direction of movement of head 3a. Movement path RU2 is the path from position PS2 to position PE2. Robot 2 moves head a along movement path RU2 in a direction closer to base 210. At this time, the direction a2 is forward in the direction of movement of head 3a.

[0148] Although not illustrated here, positions PS1 and PE2 represent the X1-direction positions relative to the predetermined area RP when viewed in the Z2 direction. (The last two sentences are repetitive and can be omitted.)

[0149] Even according to the fourth embodiment described above, printing quality can be improved. In this embodiment, as described above, two energy emission sections 3c are arranged via the head 3a. Therefore, regardless of whether printing is performed in the direction away from or close to the base 210, energy can be irradiated onto the ink immediately after it has been sprayed onto the workpiece W while maintaining the relationship between the distances DN1 and DN2 as in the first and third embodiments.

[0150] 5. Change the example

[0151] The various methods illustrated above can be modified in a wide variety of ways. The following sections illustrate specific modifications that can be applied to the aforementioned methods. Furthermore, two or more methods chosen from the following examples can be appropriately combined without contradiction.

[0152] 5-1. Modify Example 1

[0153] Although in the aforementioned configuration, the nozzle rows are arranged from near to far relative to the base 210 in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2, this configuration is not limited to the aforementioned configuration, as long as the second nozzle row L2 is positioned further from the base 210 than the first nozzle row L1. For example, the nozzle rows may also be arranged from near to far relative to the base 210 in the order of first nozzle row L1, fourth nozzle row L4, third nozzle row L3, and second nozzle row L2.

[0154] 5-2. Modify Example 2

[0155] Although the foregoing description illustrates a structure for printing using four types of inks, this disclosure is not limited to any structure using only the first and second inks. It can also be applied to structures using two, three, or five or more types of inks. Furthermore, the first ink is not limited to yellow ink, as long as it has a higher brightness compared to the second ink. Similarly, the second ink is not limited to black ink, as long as it has a lower brightness compared to the first ink.

[0156] 5-3. Modify Example 3

[0157] Although the structure using the energy emission section 3c is illustrated in the foregoing, the system is not limited to this structure, and the energy emission section 3c may be omitted. In this case, for example, another device that emits light to harden or cure ink on the workpiece may be configured outside the robot 2.

[0158] 5-4. Modify Example 4

[0159] While the foregoing description illustrates a structure using a six-axis vertical multi-axis robot as a movement mechanism, it is not limited to this structure. The movement mechanism can be, for example, a vertical multi-axis robot with axes other than six, or a horizontal multi-axis robot. Furthermore, the robot's arm can have a telescopic mechanism or a linear mechanism, in addition to a rotating part composed of a rotating mechanism. However, from the viewpoint of balancing print quality during printing operations and the degrees of freedom of the robot's movements during non-printing operations, a multi-axis robot with six or more axes is preferred.

[0160] 5-5. Modify Example 5

[0161] While the foregoing examples illustrate structures such as threaded fixing for securing the head relative to the robot, the method is not limited to these structures. For instance, the head can also be secured relative to the robot by using a gripping mechanism such as a handle installed as an end effector of the robot to hold it in place.

[0162] Symbol Explanation

[0163] 1…Printing apparatus; 1A…Printing apparatus; 1B…Printing apparatus; 2…Robot; 2a…Arm drive mechanism; 3…Head unit; 3A…Head unit; 3B…Head unit; 3a…Head; 3b…Pressure regulating valve; 3c…Energy emission unit; 3e…Switching circuit; 3f…Support body; 3g…Optical sensor; 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…Pipeline section ; 10a…supply pipe; 11…wiring section; 210…base; 220…arm; 221…arm; 222…arm; 223…arm; 224…arm; 225…arm; 226…arm; 230…joint; 230_1…joint; 230_2…joint; 230_3…joint; 230_4…joint; 230_5…joint; 230_6…joint; CLK…clock signal; CNG…conversion signal; Com…drive signal; D1…output; D3…signal; DA…distance; DL1…distance; DL2…distance; DN1…distance; DN2…distance; DN3…distance; DN4…distance; DS1…distance; DS2…distance; Da…path information; EB…base end; ET…top end; FL…ejection surface; FN…ejection surface; FS…light receiving part; Img…printing data; L1…first nozzle row; L2…second nozzle row; L3…third nozzle row; L4…fourth nozzle row; LAT…latch signal; N…nozzle; O1…rotation axis; O2…rotation axis; O3…rotation axis; O4…rotation axis; O5…rotation axis; O6…rotation axis; PD …drive pulse; PE…position; PE1…position; PE2…position; PR1…position; PR2…position; PS…position; PS1…position; PS2…position; PTS…timing signal; RP…predetermined area; RU…movement path; RU1…movement path; RU2…movement path; SI…printing data signal; Sk1…control signal; VBS…bias potential; VHV…power supply potential; W…workpiece; WF…surface; dCom…waveform specification signal; f…support; θ…rotation angle; θ1…angle; θ2…angle.

Claims

1. A printing apparatus comprising: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink and a second nozzle array arranged with a plurality of nozzles ejecting a second ink. A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. The brightness of the second ink is lower than that of the first ink. When the timing for ejecting the first ink from the first nozzle array to a predetermined position on the workpiece is set as the first timing, and the timing for ejecting the second ink from the second nozzle array to the predetermined position is set as the second timing, The distance between the top end and the base end under the second timing is less than the distance between the top end and the base end under the first timing.

2. The printing apparatus as claimed in claim 1, wherein, In each of the first and second timings, the distance between the second nozzle array and the base end is greater than the distance between the first nozzle array and the base end.

3. The printing apparatus as claimed in claim 1 or 2, wherein, During the period when the robot causes the head to scan along a predetermined area on the workpiece, including the predetermined position, and when the robot causes the head to scan along the predetermined area, and when the robot causes the head to scan along the predetermined area, and when the robot causes the head to scan along the predetermined area, and when the robot causes the head to scan along the predetermined area, and when the robot causes the head to scan along the predetermined area, and when the robot causes the head to scan along the predetermined area, and when the robot causes the head to scan along the predetermined area, the distance between the second nozzle column and the base is maintained to be greater than the distance between the first nozzle column and the base.

4. The printing apparatus as claimed in claim 1, wherein, The head also includes a third nozzle array comprising a plurality of nozzles arranged to eject a third ink. The brightness of the third ink is lower than that of the first ink but higher than that of the second ink. In each of the first and second timing periods, the distance between the third nozzle array and the base end is greater than the distance between the first nozzle array and the base end, and less than the distance between the second nozzle array and the base end.

5. The printing apparatus as claimed in claim 1, wherein, The head includes multiple rows of nozzles that eject ink. The plurality of nozzle columns include the first nozzle column and the second nozzle column. The brightness of ink ejected from the nozzle column that is farther from the base end, selected from any two nozzle columns, is lower than the brightness of ink ejected from the nozzle column that is closer to the base end.

6. The printing apparatus as claimed in claim 1, wherein, It also has an energy emission section supported by the top end and includes an emission surface that emits energy to cure each of the first ink and the second ink. The distance between the second nozzle array and the exit surface is greater than the distance between the first nozzle array and the exit surface.

7. The printing apparatus as claimed in claim 1, wherein, It also has an energy emission section supported by the top end and includes an emission surface that emits energy to cure each of the first ink and the second ink. The distance between the second nozzle array and the exit surface is less than the distance between the first nozzle array and the exit surface.

8. The printing apparatus as claimed in claim 1, wherein, It also includes an optical sensor, which is supported by the top end and includes a light-receiving portion. The distance between the second nozzle array and the light-receiving part is greater than the distance between the first nozzle array and the light-receiving part.

9. The printing apparatus as claimed in claim 1, wherein, During the period during which the head scans along a predetermined area on the workpiece, including the predetermined position. When the period during which the first ink is ejected from the first nozzle array relative to the predetermined area is defined as the first period, and the period during which the second ink is ejected from the second nozzle array relative to the predetermined area is defined as the second period, The total amount of rotation of the plurality of joints during the second period is less than the total amount of rotation of the plurality of joints during the first period.

10. The printing apparatus of claim 1, wherein, The first ink is the ink with the highest brightness among the inks ejected from the head.

11. The printing apparatus as claimed in claim 1, wherein, The first ink is either yellow or white.

12. The printing apparatus of claim 1, wherein, The second ink is the ink with the lowest brightness among the inks ejected from the head.

13. The printing apparatus of claim 1, wherein, The second ink is black ink.

14. The printing apparatus as claimed in claim 1, wherein, The head includes multiple rows of nozzles that eject ink. The first nozzle array and the second nozzle array are the two nozzle arrays that are configured to be furthest apart from each other among the plurality of nozzle arrays.

15. A printing apparatus comprising: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink and a second nozzle array arranged with a plurality of nozzles ejecting a second ink. A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. The brightness of the second ink is lower than that of the first ink. When the head reaches a predetermined area on the workpiece, including a predetermined position from which the first ink is ejected from the first nozzle array, and when the first ink is ejected from the first nozzle array toward the predetermined position, the distance between the second nozzle array and the base end is longer than the distance between the first nozzle array and the base end.

16. A printing method comprising a printing apparatus having: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink, and a second nozzle array arranged with a plurality of nozzles ejecting a second ink with a lower brightness compared to the first ink; A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. In the printing method, This includes the printing action of the head ejecting the first ink and the second ink while the robot moves the head away from the base. When the timing for ejecting the first ink from the first nozzle array to a predetermined position on the workpiece in the printing operation is set as the first timing, and the timing for ejecting the second ink from the second nozzle array to the predetermined position is set as the second timing, The distance between the top end and the base end under the second timing is less than the distance between the top end and the base end under the first timing.

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