CN107297892B - A kind of 3D curved surface EFI being patterned device and method - Google Patents

Abstract

The invention belongs to the related technical field of surface patterning of curved objects, and discloses a 3D curved surface electrojet printing patterning equipment, including a workbench, a loading and unloading module, an electrojet printing module, a vision module and a curing module, wherein the workbench presents multiple In the form of a station turntable, the switching of each station is performed by its own rotation; the electrojet printing module includes multiple sets of inkjet printing heads corresponding to multiple electrojet printing and pre-curing stations, and can perform curved surface printing. Free pose adjustment and electrojet printing operation; the vision module includes a positioning camera, a measuring camera, a detection camera, a substrate observation camera and a jet observation camera, and performs high-precision online inspection of the process links in each station. The invention also discloses a corresponding process method. The invention is based on electrofluid jet printing technology, has the characteristics of high flexibility and high resolution jet printing, can realize curved surface jet printing with high quality, and is suitable for patterning curved surfaces with various patterns, such as patterning of 3D mobile phone cover plates process.

Description

A 3D curved surface electrojet printing patterning device and method

technical field

The invention belongs to the related technical field of surface patterning of curved objects, and more specifically relates to a 3D curved surface electrojet printing patterning device and method.

Background technique

Typical 3D surfaces include components such as 3D mobile phone covers. Since the development of smartphones, appearance design has become the focus of competition, and curved screens are popular for their unique visual effects and operating experience. The 3D curved surface cover is thin, transparent and clean, anti-fingerprint, anti-glare, hard, scratch-resistant, and weather-resistant. The curved edge touch function brings excellent touch feel, which can solve the problem of insufficient antenna layout space and enhance Features such as the receiving function, thus producing obvious advantages. For curved surface printing such as 3D mobile phone cover, it refers to the production of opaque colored areas, logos, button icons and other patterns on the curved cover. However, the patterning of such objects is very difficult and belongs to the industry. One of the consensus.

The curved surface printing process in the prior art usually includes the following categories: screen printing technology, which uses a scraper to apply pressure on the graphic part of the printing plate to squeeze the ink from the mesh to the substrate. The ink layer is thick, but the curved surface It is difficult to ensure that the shape of the substrate, screen frame and squeegee are consistent during printing, and ink accumulation is serious at places where the curvature changes sharply; OCA composite printing technology is to composite printed graphics and texts on the target surface through OCA optical glue, and the process is relatively complicated; Coloring technology is to replace other ions in the superficial layer of glass with non-ferrous metal ions to present a color. The color is lighter and the process cost is high. In addition, there are other technologies such as photolithographic ink printing technology and laser engraving ink technology.

However, further research shows that: firstly, none of the above-mentioned patterning technologies can well solve the problem of seamless connection in the whole manufacturing process of 3D curved objects, the efficiency is low when used, the operation is cumbersome, and there are various limitations; secondly , in the actual manufacturing process, it is necessary to obtain high-response, high-precision real-time control of the height information of the curved surface, and then achieve high-resolution curved surface patterning. However, the existing measurement schemes are often only suitable for the measurement of planar objects. The distance information from the measured object to the camera can be measured, but the accurate deformation information of the measured object in the direction away from the plane cannot be obtained. Correspondingly, there is an urgent need in the art to seek a more complete solution to the above technical problems so as to meet the current increasing technological requirements.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a 3D curved surface electrojet printing patterning device and method, wherein the overall structure and layout of the patterning device are redesigned, and multiple key Components such as the electrojet printing module, vision module, and the specific composition and setting of the workbench have been improved in many aspects. At the same time, the measurement module and measurement principle of the surface height have been specially researched, corresponding to the existing 3D surface pattern. Compared with modernization technology, it can not only efficiently perform multiple complex processes such as clamping positioning-height measurement-multiple electrospray printing and pre-curing-quality inspection and final curing in a non-contact manner, but also can realize The seamless connection of high precision and convenient station conversion has significantly improved the overall production efficiency; in addition, it can also obtain higher-precision surface height information measurement based on monocular vision during the printing process, thereby further ensuring that Obtain high-resolution, high-flexibility 3D surface electrospray printing patterning effect.

In order to achieve the above object, according to one aspect of the present invention, a 3D curved surface electrojet printing patterning equipment is provided, the equipment includes a workbench, a loading and unloading module, an electrojet printing module, a vision module and a curing module, and is characterized in that:

The workbench is in the form of a multi-station turntable, which performs the switching of various stations through its own rotation, and these stations successively include the positioning and clamping station of the curved surface, the height measurement station of the curved surface, and multiple electrojet printing stations. and pre-curing stations, as well as quality inspection stations; in addition, each station is equipped with fixtures for clamping curved surfaces, and each station can perform related operations independently of each other;

The loading and unloading module is arranged on one side of the multi-station turntable, which includes a mechanical arm equipped with a vacuum suction cup at the end, and is used to periodically absorb the curved surface to be worked, and transfer it to each station or from it move out;

The electrojet printing module includes multiple sets of jet printing heads, which are set up one by one corresponding to each of the electrojet printing and pre-curing stations, and each jet printing head has the freedom of movement in the XYZ three-axis direction degree, and the radial degree of freedom along the multi-station turntable, thereby adjusting the relative position with the curved surface;

The vision module includes a positioning camera, a measuring camera, a detection camera, a substrate observation camera, and a jet flow observation camera, wherein the positioning camera is installed above the positioning and clamping station, and is used to observe and determine the position of the curved surface on the clamp The correct installation position; the measurement camera is installed above the height measurement station to measure the height characteristic information of the curved surface in real time, and then guide the movement of the printing head so as to ensure a constant relationship between the nozzle and the curved surface height, and accordingly select nozzles to form the required line array; the inspection camera is installed above the quality inspection station, and is used to inspect the printing quality on the curved surface; in addition, the substrate observation camera is connected with each The nozzles of the above-mentioned jet printing head are installed in parallel and move together with them, and are used to perform visual positioning to determine the initial position of jet printing before performing electrojet printing, and at the same time photograph the formed pattern during the entire jet printing process; the jet The observation camera is used to perform online image capture and measurement of the ink droplet volume ejected by the printing head;

The curing module includes a pre-curing device and a final curing device, wherein each pre-curing device is set corresponding to each of the printing heads and moves together with it, and is used to perform each printing after the printing head completes each printing. A pre-curing operation is performed on the curved surface; the final curing device is arranged on one side of the multi-station turntable, and is used to perform final complete curing on the overall pattern on the curved surface.

As further preferably, each of the printing heads includes a nozzle, a ring electrode disposed below the nozzle and grounded, a high-voltage generator for generating an electric field between the nozzle and the ring electrode, and an ink stored therein and The inkjet printing container kept in communication with the nozzle; during operation, under the induction of the electric field force, the ink forms a Taylor cone at the top of the nozzle, and the droplets continue to be ejected from the top of the Taylor cone and are discharged under the action of the electric field force. Break into a large number of small droplets, and then realize the patterning operation on the curved surface.

As a further preference, the nozzle of the printing head is preferably a single nozzle or an arrayed nozzle composed of a plurality of small nozzles; when the arrayed nozzle is used, each small nozzle is arranged with a certain height difference, and Preferably, the spraying is carried out in the following state: the curve where the bottom end of the selected small nozzle is projected on the vertical plane is set to maintain a substantially conformal shape with the section line of the surface to be sprayed.

As a further preference, each of the printing heads is equipped with inks of the same or different materials, and is used to perform printing on different regions of the curved surface, thereby realizing electrojet printing of multi-layer complex patterns.

As a further preference, for the measurement camera, it preferably uses monocular vision to perform the measurement of the characteristic information of the surface height, and includes a measurement rack, a parallel light source assembly, a height detection camera and a distance sensor, wherein:

The measuring frame is in the form of a horizontally arranged symmetrical cross frame and serves as the mounting base for the other components;

The number of the parallel light source components is four, and they are respectively installed under the ends of the four identical arm structures of the measuring rack, and can be driven to rotate by matching motors to change the projection angle; each parallel The light source components are respectively composed of an installation box, and a collimator and a transmission grating respectively arranged inside the installation box, wherein the collimator is used to emit parallel light beams to the transmission grating, and the transmission grating is engraved with alternate width and narrow width. Two kinds of parallel notches, so that the parallel light beam emitted by the collimator can be projected on the surface to be measured to form parallel stripes with alternating light and dark;

The number of the height detection camera is only one, which is fixedly installed under the center of the measurement frame, and cooperates with each of the parallel light source components, and is used to collect images of the parallel stripes formed on the surface to be measured to obtain the desired 2D image;

The distance sensors are respectively arranged corresponding to each of the parallel light source components, and are used to adjust the height of the measurement rack so that the height detection camera can obtain a clear two-dimensional image. Measure the vertical distance H between the optical center of the lens of the height detection camera and the X"Y" plane, and simultaneously use it to detect the parallelism between the imaging plane of the height detection camera and the X"Y" plane , wherein the X"Y" plane is a reference plane pre-built before measurement, and it is parallel to the horizontal XY plane established with the optical center of the lens of the height detection camera as the origin.

As further preferably, for the light-transmitting wide slits and light-transmitting narrow slits in the light-transmitting slits respectively provided by the transmission gratings, their positions are coded and sorted in n-bit binary mode, and preferably the n×2 ⁿ The number of light-transmitting slits is encoded; the value of n is determined according to the field of view of the detection camera, and it is ensured that the number of stripes in the image obtained by the detection camera should satisfy m>3n-1; in addition, the The width ratio between the light-transmitting narrow slit d ₂ and the light-transmitting wide slit d ₁ preferably satisfies the formula d ₁ /d ₂ ≥2.

According to another aspect of the present invention, there is also provided a corresponding 3D curved surface electrospray printing method, characterized in that the method comprises the following steps:

(a) Vacuum absorb the curved surface to be printed by the mechanical arm, and transfer to the first station of the workbench, that is, the positioning and clamping station;

(b) Firstly, the correct installation position of the curved surface is determined by the positioning camera, and then the mechanical arm releases the curved surface according to this position, and the curved surface is sucked by the clamp to complete the clamping;

(c) the workbench is transferred to the next station, that is, the height measurement station, and the measurement operation of the height characteristic information of the curved surface is completed by the measurement camera;

(d) The workbench is switched to the next station, that is, the first of a plurality of electrospray printing and pre-curing stations, and the electrofluid jet printing of the first pattern is performed on the curved surface by the print head , and then perform surface pre-curing on the ink by the pre-curing device; then, continue to switch to the remaining electrojet printing and pre-curing stations, and perform subsequent pattern printing and pre-curing operations until the patterning of the entire curved surface is completed;

(e) The workbench is transferred to the next station, that is, the quality inspection station, and the inspection camera performs inspection on the printing quality on the curved surface; then, the mechanical arm removes the inspected curved surface, Send it to the final curing device to final cure the overall pattern on the curved surface;

(f) The mechanical arm puts the solidified curved surface into the finished product area, and prepares for the next loading.

As a further preference, in step (c), the measurement camera preferably uses monocular vision to perform the measurement process of the characteristic information of the surface height, wherein:

(c1) Establish a camera Cartesian coordinate system XYZ with the optical center of the lens of the height detection camera as the origin, wherein the Z axis of the camera Cartesian coordinate system coincides with the optical axis of the height detection camera and points below the detection camera , its X-axis and Y-axis satisfy the right-hand rule, and two of the four parallel light source components remain symmetrically located on this X-axis, and the remaining two remain symmetrically located on this Y-axis; similarly, with The center of the imaging plane of the height detection camera is the origin to establish an image Cartesian coordinate system X'Y'Z, wherein the Z axis of the image Cartesian coordinate system coincides with the Z axis of the camera Cartesian coordinate system, and its X' axis , Y' axis also satisfies the right-hand rule; then, establish a reference Cartesian coordinate system X"Y"Z directly below the height detection camera, wherein the Z axis of the reference Cartesian coordinate system is the same as the optical axis of the detection camera Coincident, its X "axis, Y" axis also satisfy the right-hand rule, and its X "Y" plane remains parallel to the XY plane of the Cartesian coordinate system of the camera;

(c2) First, use the four distance sensors to measure the distance information to the X"Y" plane respectively, and adjust the pose of the X"Y" plane according to the obtained distance information so that it is kept in line with the imaging plane of the detection camera Parallel; at the same time, compensate the difference in the Z-axis direction between the distance sensor and the optical center of the detection camera, and then measure and determine the distance between the optical center of the detection camera and the X"Y" plane Vertical distance H;

(c3) using a set of parallel light source components to project bright stripes with alternate widths and narrow widths on the surface to be measured, and using the motor to drive the parallel light source components to rotate, so that the stripes slowly sweep across the entire area to be measured; the detection camera Take a picture, and write down the projection angle α of each image; then, use the remaining three groups of parallel light source components in turn, repeat the above steps, and obtain four images of the region to be measured under the stripes projected by the four groups of parallel light source components. group image;

(c4) For the obtained four groups of images, calculate the deformation amount of any point P in the Z-axis direction on the stripes formed by each of the parallel light source components projected on the curved surface to be measured, and then calculate the average value by weighting method to calculate the actual deformation;

(c5) Move the measurement rack, traverse the entire surface to be measured in sequence, repeat steps (c2) to (c4), until the height information of all points on the entire surface to be measured is obtained, and thus complete the overall surface height measurement process .

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1. This application redesigns the overall structure and layout of the patterning equipment in combination with the actual needs of 3D curved surface patterning applications. Correspondingly, compared with the existing 3D curved surface patterning technology, it can not only Efficiently implement multiple complex processes such as clamping positioning-height measurement-multiple electrospray printing and pre-curing-quality inspection and final curing, and the seamless connection of high precision and convenient station conversion can be achieved during the entire operation process. Significantly improved the overall production efficiency;

2. The present invention further improves multiple key components such as the specific composition and arrangement of the electrojet printing module, vision module and workbench; wherein, the entire structure of the electrojet printing module adopted is compact and light, It is convenient to perform flexible adjustments in multiple directions, and can obtain higher-resolution fine surface patterns with non-contact patterning technology; the vision module can perform online monitoring and real-time feedback of multiple process parameters in the entire process, by This further improves the quality of the final product; in addition, the turntable-type workbench can work at multiple stations at the same time, which is convenient for station conversion and significantly improves production efficiency;

3. The present invention further studies the visual component and its working principle of curved surface height information measurement. Correspondingly, not only a single camera can be used to complete the overall measurement process of curved surface height information, but also its structure is more compact than existing equipment. It is compact and reasonable, easy to handle, and significantly improves the final measurement accuracy;

4. The yield rate of the product in the present invention is high, and vacuum suction cups are used for clamping and installing the curved surface to avoid scratching the curved surface. The positioning, measurement, printing process observation and printing quality inspection of the curved surface are realized by the camera, and the reliability is good; in addition, The fixture with two degrees of freedom of rotation and the printing head with three degrees of freedom of movement can effectively cooperate to realize the printing at various positions on the curved surface, avoiding the difficulty in ensuring the shape of the substrate, screen frame and squeegee in screen printing in curved surface printing For the matching problem, compared with other surface object patterning technologies, the process is simple, and there is no need to make printing plates, ink storage tanks, etc., so it is especially suitable for 3D surface patterning applications with various complex patterns.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of a 3D curved surface electrospray printing patterning device constructed according to a preferred embodiment of the present invention;

Fig. 2 is a schematic diagram illustrating a plurality of stations of the equipment shown in Fig. 1 and a conversion process thereof;

Fig. 3 is the overall process flow chart of the 3D curved surface electrospray printing patterning of the equipment shown in Fig. 1;

Fig. 4 is a schematic diagram designed according to a preferred embodiment of the present invention and used to demonstrate the electric field application method of electrojet printing technology in the present invention;

Fig. 5a is a schematic diagram of a monocular vision-based surface height information measurement scheme designed according to another preferred embodiment of the present invention;

Fig. 5b is a schematic diagram for exemplarily illustrating multiple coordinate systems constructed to facilitate the calculation and processing of surface height information in the later stage;

Fig. 5c is a schematic diagram of the composition and structure of a parallel light source assembly designed according to a preferred embodiment of the present invention;

Fig. 5d is a schematic diagram for exemplarily illustrating the projection of parallel light source components to form multiple stripes;

Fig. 5e is a schematic diagram obtained by encoding multiple stripes formed by parallel light source components according to the preferred embodiment of the present invention;

Fig. 6 is a schematic diagram for exemplarily showing the adjustment method of the curved surface pose in the present invention;

Fig. 7 is a schematic structural view of arrayed nozzles designed according to another preferred embodiment of the present invention;

Fig. 8 is a schematic diagram for more specifically showing the preferred mode of operation of the nozzle shown in Fig. 7;

FIG. 9 is a flow chart of a more specific 3D curved surface electrospray printing patterning process constructed by the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Fig. 1 is a schematic diagram of the overall structure of a 3D curved surface electrospray printing patterning device constructed according to a preferred embodiment of the present invention, Fig. 2 is a schematic diagram explaining multiple stations of the device shown in Fig. 1 and its conversion process, and Fig. 3 is a diagram The overall process flow chart of the 3D surface electrospray printing patterning of the equipment shown in 1. As shown in Figures 1 to 3, the equipment mainly includes functional components such as a workbench 500, a loading and unloading module 100, an electrojet printing module 400, a vision module 300, and a curing module 200, which will be described in detail below.

As one of the key components of the present invention, the workbench 500 is in the form of a multi-station turntable, which performs the switching of each station through its own rotation, and these stations include the positioning and clamping station of the curved surface, and the height measurement of the curved surface in turn. station, a plurality of electrospray printing and pre-curing stations, and a quality inspection station; in addition, each station is equipped with a fixture 502 for clamping a curved surface, and each station can perform related operations independently of each other. In other words, nozzles (which can be single nozzles or arrayed nozzles) 401, printing heads 402, pre-curing devices 202, positioning cameras 301, measuring cameras, detection cameras 302, fixtures 502 and other components are integrated in the On the multi-station turntable, and use the mechanical arm 101 with two rotational degrees of freedom for loading and unloading.

As shown in Figure 3, each process from ② to ⑤ is completed on the multi-station turntable, patterning and pre-curing of multiple curved surfaces, positioning and installation of curved surfaces, height measurement, and printing quality inspection. These processes can be carried out at the same time , or choose the implementation according to the needs, reflecting greater flexibility. Each station is preferably equipped with a double-rotation-degree-of-freedom fixture 502. The fixture is equipped with a vacuum suction cup 503 to clamp the curved surface and avoid damage. The suction cup 503 can be selected from the SMC vacuum suction cup series. Each of the above-mentioned modules does not rotate with the turntable, and the station is switched by turning the turntable at a certain angle. The time for switching stations is determined according to the longest process.

The loading and unloading module 100 preferably uses a robotic arm 101 to realize periodic automatic loading and unloading, and the end of the robotic arm 101 absorbs curved surfaces through a vacuum chuck 102 . The mechanical arm 101 is preferably an articulated mechanical arm with a large working space, and the suction cup 102 can be an SMC vacuum suction cup series.

As another key component of the present invention, the electrojet printing module 400 includes multiple sets of jet printing heads 402, which are set up one by one corresponding to each of the electrojet printing and pre-curing stations, and each jet printing The head has the degree of freedom of movement in the XYZ three-axis direction, and the degree of freedom along the radial direction of the multi-position turntable, thereby adjusting the relative position with the curved surface.

More specifically, the electrojet printing module 400 is designed in this application to adopt an electrofluid jet printing process. As shown in Figure 4, unlike the conventional method of applying an electric field between the nozzle 401 and the substrate, a grounded ring electrode 406 is provided below the nozzle 401, and a high voltage electric field is formed between the nozzle 401 and the ring electrode 406 through a high voltage generator 405, To create conditions for electrojet printing, the inkjet printing head 402 is supplied with ink from a container 404 that stores ink of a specific material. Under the action of the induced electric field force, the ink flows out from the inkjet printing head 402, forming a Taylor cone at the top of the nozzle 401, and the droplets flow from the Taylor The tip of the cone shoots out and is broken into small liquid droplets under the action of the electric field force to realize high-resolution printing with the diameter of the ink droplet smaller than the diameter of the nozzle 401 .

In addition, the electrojet printing module 400 includes multiple sets of printing heads 402 , and three sets of printing heads 402 are taken as an example for illustration below. Each printing head 402 prints inks of different materials, or performs printing on different regions of the curved surface, so that multiple layers of complex patterns can be printed. Each set of printing heads 402 independently has three degrees of freedom of movement, and one is along the radial direction of the multi-position turntable, which is convenient for adjusting the relative position with the curved surface. Each set of printing heads 402 is equipped with two observation cameras that will be described in detail below, wherein the substrate observation camera 308 is installed in parallel with the nozzle 401 and moves accordingly, preferably using a coaxial light source, and performs pre-printing after switching stations. The visual positioning of the jet can find the starting position of the jet printing, and can observe the completed pattern during the jet printing process. The jet observation camera 309 is used to measure the volume of the flying ink droplet.

By using the jet observation camera 309, the online measurement of the volume of the flying ink droplet can be realized, and the measurement is carried out during the process of the ink droplet landing on the curved surface. The jet observation camera 309 is perpendicular to the direction of the nozzle 401 or at a certain angle. Preferably, a high-speed camera is used, and a strobe LED is selected, and its flash frequency is an integral multiple of the injection frequency. It is installed on the opposite side of the camera 309. Add a magnifying glass or microscope to observe tiny ink droplets. According to the measurement results, the inkjet control is carried out in real time, the inkjet volume is adjusted, and the nozzles with small inkjet volume or missing spray are compensated to form a closed-loop feedback.

As another key component of the present invention, the vision module 300 includes a positioning camera 301, a measurement camera, a detection camera 302, a substrate observation camera 308, and a jet flow observation camera 309, wherein the positioning camera 301 is installed in the positioning and clamping station above, and used to observe and determine the correct installation position of the curved surface on the fixture; the measurement camera is installed above the height measurement station, used to measure the height characteristic information of the curved surface in real time, and then guide the sprayer The movement of the printing head, in order to ensure a constant height between its nozzle and the curved surface, and accordingly select the nozzle to form the required line array; the inspection camera 302 is installed above the quality inspection station, and is used to inspect the The printing quality is inspected; in addition, the substrate observation camera 308 is installed in parallel with the nozzles of each of the printing heads and moves together therewith, and is used to perform visual positioning to determine the initial position of the printing before performing electrojet printing , while photographing the formed pattern during the entire printing process; the jet observation camera 309 is used to perform on-line photographing and measurement of the ink droplet volume ejected by the printing head to form a closed-loop feedback.

Finally, the curing module 200 includes a pre-curing device 202 and a final curing device 201, wherein each pre-curing device 202 is set corresponding to each of the printing heads and moves together with it, and is used to complete each After the first jet printing, a pre-curing operation is performed on the curved surface; the final curing device 201 is arranged on one side of the multi-station turntable, and is used for final complete curing of the overall pattern on the curved surface.

More specifically, pre-curing is used to cure the surface layer of the ink pattern, preferably using UV curing such as UVLED, which is small in size and can be installed at the printing head 402 to move together, using a line light source or a surface light source, and it can be cured in about 2s. After the pre-curing is completed, after each printing, the UVLED is moved to the working area above the curved surface by the three-degree-of-freedom moving mechanism 403 to perform a pre-curing. The final curing is to fully cure the entire curved surface pattern, preferably heat curing, and preferably baked, and the final curing can be performed on multiple curved surfaces at the same time to save time and cost.

The overall working process of the above-mentioned equipment of the present invention will be explained more specifically below in conjunction with FIG. 9 .

1) The mechanical arm 101 absorbs the curved surface to be printed from the material rack, and transfers it to the positioning station of the workbench 500;

2) The positioning camera 301 determines the correct installation position of the curved surface, the suction cup 102 of the mechanical arm releases the curved surface, and the suction cup 503 of the fixture absorbs the curved surface, and the clamping is completed;

3) Turn the turntable to a certain angle to station 2, measure the height information of the curved surface measured by the camera, and obtain the shape characteristics of the curved surface;

4) The turntable rotates to a certain angle to station three, and the printing head 402 performs the electrofluid printing of the first pattern;

5) The pre-curing device 202 cures the surface layer of the ink pattern;

6) Turn the turntable to a certain angle to the next station for subsequent pattern printing and pre-curing until the patterning of the entire curved surface is completed;

7) The turntable rotates at a certain angle to the inspection station, and the inspection camera 302 inspects the printing quality of the curved surface;

8) The robotic arm 101 removes the inspected curved surface and sends it to the final curing device 201, where multiple curved surfaces are simultaneously final cured;

9) The robotic arm 101 puts the cured curved surface into the finished product area, and prepares for the next loading.

As another key improvement of the present invention, considering that the height information of the curved surface itself directly affects the quality and accuracy of subsequent operations including clamping and printing, according to another preferred embodiment of the present invention, the measurement camera is further The specific structure and working principle have been researched and designed.

As shown in Figure 5a, the measuring camera includes a measuring frame 307, a height measuring camera 303', a parallel light source assembly 304, a distance sensor 306, a motor 305, etc., wherein the height detecting camera 303' is only one, and the remaining devices are four sets. They are divided into four groups and installed on the measuring frame 307, evenly arranged around the height detection cameras 303'.

More specifically, the measuring frame 307 is in the form of a horizontally arranged symmetrical cross frame, and serves as the installation basis for other components; the number of the parallel light source assemblies 304 is four, and they are installed on four sides of the measuring frame 307 respectively. Below the ends of two identical arm structures, they can be driven and rotated by matching motors 305 to change their projection angles; each parallel light source assembly is composed of an installation box 31 and a parallel light set inside the installation box in turn. A tube 32 and a transmission grating 33 are jointly composed, wherein the parallel light tube 32 is used to emit parallel light beams to the transmission grating 33, and the transmission grating 33 is engraved with two kinds of parallel grooves alternately wide and narrow, thus making the parallel beams The parallel light beams emitted by the light pipe 32 can be projected on the surface to be measured to form parallel stripes of light and dark. More specifically, as shown in Figure 5c-Figure 5e, each parallel light source assembly is separately provided by the installation box 31 and sequentially. The collimator 32 inside the installation box and the transmission grating 33 are composed together, wherein the collimator 32 is used to emit a monochromatic parallel light beam to the transmission grating 33, and the transmission grating 33 is engraved with two kinds of parallel beams with alternate width and narrow width. The notch also has light-transmitting slits with alternate widths and narrow ones, so that the parallel light beams emitted by the collimator 32 can be projected on the curved surface to be measured to form parallel stripes with alternate light and dark. As shown more specifically in Figures 5d and 5e, the distance between the centerline of the light-transmitting slit and the centerline of adjacent notches is the grating constant d, the width of the light _- transmitting wide slit is d1, and the width of the light-transmitting narrow slit is _d2 . The parallel light emitted by the collimator 32 passes through the transmission grating 33 to form stripes with different widths on the curved surface to be measured. In order to avoid light diffraction, the monochromatic light wavelength λ of the collimator 32 should be selected according to the width of the light transmission slit, but must be smaller than the width of the light transmission slit, that is, λ<min{d ₁ ,d ₂ }. Then choose according to the accuracy requirements, the smaller the wavelength λ, the less obvious the diffraction phenomenon.

The number of the height detection camera 303' is only one, which is fixedly installed under the center of the measuring frame 307, and cooperates with each of the parallel light source assemblies 304, and is used to execute the parallel stripes formed on the curved surface to be measured. Take a picture to obtain the required two-dimensional image; In addition, the distance sensor 306 is arranged corresponding to each of the parallel light source assemblies 304, and when the height of the measuring frame 307 is adjusted so that the height detection camera can When a clear two-dimensional image is obtained, it is used to measure the vertical distance H between the optical center of the lens of the height detection camera and the X"Y" plane at this position, and is used for this height detection The parallelism between the imaging plane of the camera and the X"Y" plane is detected, wherein the X"Y" plane is a reference plane pre-built before the height characteristic information measurement, and it is detected with the height The horizontal XY plane established by the optical center of the camera lens as the origin remains parallel to each other.

As exemplarily shown in Figure 5b, in order to facilitate the later calculation process of the surface height, the optical center of the lens of the height detection camera can be used as the origin to establish a camera Cartesian coordinate system XYZ, wherein the Z axis of the camera teaching coordinate system is related to the height The optical axes of the detection cameras are coincident and point to the bottom of the detection camera, their X-axis and Y-axis satisfy the right-hand rule, and two of the four parallel light source components remain symmetrically on this X-axis, and the remaining two are also Keep symmetrically on this Y axis; similarly, set up an image Cartesian coordinate system X'Y'Z with the center of the imaging plane of the height detection camera as the origin, wherein the Z axis of the image Cartesian coordinate system is in line with the camera The Z axis of the teaching coordinate system coincides, and its X' axis and Y' axis also satisfy the right-hand rule; then, a reference rectangular coordinate system X"Y"Z is established directly below the detection camera, wherein the reference rectangular coordinate system The Z axis of the system coincides with the optical axis of the detection camera, its X "axis and Y" axis also satisfy the right-hand rule, and its X "Y" plane remains parallel to the XY plane of the camera Cartesian coordinate system.

In addition, as shown in Figure 5e, the stripe light beam generated by the parallel light source component can form multiple stripes on the X"Y" plane, where "1" represents thin stripes and "0" represents thick stripes. Through this encoding method, the corresponding relationship between the stripes on the surface to be measured and the stripes on the X"Y" plane in the image captured by the detection camera can be identified. When the detection camera captures the stripes on the surface to be tested as "001010011", there are three possible results: "0""010""100""11""00""101""001""1" and "001"010" and "011", corresponding to serial numbers "x ₁ 23x ₂ ", "x ₃ 51x ₄ ", and "123" respectively. Among them, x ₁ is not 1 and x ₂ is greater than 4, so the first group is wrong; the second group of sequences is also wrong; therefore, only the third group of sequences remains, and it conforms to the coding rules. Every fringe in the field of view is correctly identified.

The above surface height information measurement process method can be summarized as follows main steps:

Step 1: first use the four distance sensors to measure the distance information to the X"Y" plane respectively, and adjust the X"Y" plane pose according to the obtained distance information so that it is on the imaging plane of the height detection camera Keep parallel; at the same time, compensate the difference in the Z-axis direction between the distance sensor and the optical center of the height detection camera, and then measure and determine the optical center of the height detection camera to the X"Y" plane The vertical distance H between;

Step 2: Use the group of parallel light source components to project bright stripes with alternate widths and narrow widths on the surface to be measured, and use the motor to drive the parallel light source components to rotate, so that the stripes slowly sweep across the entire area to be measured; the height detection Take a picture with the camera, and write down the projection angle α of each image; then, use the remaining three groups of parallel light source components in turn, repeat the above steps, and respectively obtain the area to be measured under the stripes projected by the four groups of parallel light source components. Four sets of images;

Step 3: For the obtained four sets of images, calculate the deformation of any point P in the Z-axis direction on the stripes formed by each of the parallel light source components projected on the surface to be measured, and then calculate the average value by weighting method to calculate the actual deformation;

Step 4: Move the measurement rack, traverse the entire surface to be measured in sequence, and repeat steps 1 to 3 until the height information of all points on the entire surface to be measured is obtained, thereby completing the overall surface height measurement process.

Similarly, considering that the positioning accuracy and operation of the printing head also directly affect the quality and accuracy of subsequent operations, according to another preferred embodiment of the present invention, further studies have been made on the specific structure and working principle of the printing head and design.

As shown in Figure 6, the printing head 402 preferably can independently have three degrees of freedom of movement in the directions of x, y, and z, adjust the relative position of the nozzle 401 and the curved surface, and the degree of freedom of movement in the vertical direction ensures that the nozzle 401 and the curved surface maintain a constant Appropriate height, the fixture 502 has two degrees of freedom of rotation to adjust the spatial posture of the curved surface. During the printing process, by judging the current printing position and combining the height data of the curved surface, the posture of the curved surface is continuously adjusted to ensure that the surface of the printing area is consistent with the surface. The nozzle is vertical, and the curved surface printing is realized through the five-degree-of-freedom system, which can ensure the uniform amount of ink on the curved surface.

More specifically, according to a preferred embodiment of the present invention, as shown in Figure 7 and Figure 8, the nozzle 401 of the printing head is a single nozzle or an arrayed nozzle composed of a plurality of small nozzles; when using an arrayed nozzle In the form of the above-mentioned method, each small nozzle is arranged with a certain height difference, and the spraying is preferably carried out in the following state: the curve where the selected small nozzle bottom is projected on the vertical plane is set to be in line with the curved surface to be printed Keep the basic conformality between them.

When a single nozzle is used for printing, it can ensure that the nozzle is perpendicular to the curved surface to be printed when spraying, thereby improving the printing quality. In addition, for larger and complex 3D curved surfaces, in order to improve printing efficiency, arrayed nozzles 407 can be used. The arrayed nozzles are arranged in a 3×6 array as shown in the figure, and the printing head 402 equipped with a single nozzle 401 and an arrayed nozzle 407 is used at the same time. The arrayed nozzle 407 is used for a large printing area and a curvature Smaller curved surface area to improve efficiency, single nozzle 401 is used to print small patterns and curved surface areas with large curvature to ensure uniform ink droplets and improve printing quality. The arrayed nozzle 407 is composed of a large number of nozzles, and there is a certain height difference between each row of nozzles. When printing, first adjust the height between the printing head 402 and the curved surface to an appropriate range, and select the surface information through the control algorithm according to the curved surface information obtained by the measuring camera. Part of the nozzles are sprayed, and the surface where the bottom of the selected nozzle is located conforms to the surface to be printed to ensure that the height of each nozzle and the surface is at an optimal value. The black nozzle in the figure represents a selected combination. Different combinations can be used. Adapts to surfaces of varying curvature.

Figure 8 exemplarily shows this method of forming a conformal nozzle array through height difference. The section below the nozzle 407 is a section of the curved surface to be printed. Viewed from the front of the nozzle 407, the nozzles in different rows are projected on a vertical plane. Straight plane, the selected nozzles marked in black are on the curve conformal to the section line of the surface to be printed, that is, these nozzles form a nozzle line array on a space curve, and the curved surface is printed by a line scanning strategy. Nozzles 407 and The direction of relative motion of the surfaces is perpendicular to the surface section in the figure. The control algorithm is used to realize the deformation of the arrayed nozzle 407. Compared with the deformation through the mechanical structure, it can be adjusted in real time during spraying, maintains a conformal state, adapts to surfaces with different curvatures, and has good flexibility.

To sum up, the present invention provides a 3D curved surface electrojet printing patterning process, using electrofluid jet printing technology, which can simultaneously print multiple pieces of 3D curved surface with different patterns in different regions on one workbench, including the following process flow: Positioning → measuring surface features → multiple electrofluid printing → multiple pre-curing → printing quality inspection → final curing. The process has a high degree of automation, and the clamping method has little damage to the curved surface. The electrofluid jet printing technology can print fine patterns with high resolution, and the camera can be used for positioning, measurement, inkjet observation and printing quality inspection, which can realize pattern printing on curved surfaces. Therefore, it is suitable for the patterning of 3D curved surfaces, and is suitable for the patterning of curved surfaces with complex patterns such as 3D mobile phone covers.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (8)

1. a kind of 3D curved surface EFI being patterned equipment, which includes workbench, loading and unloading module, EFI impression block, vision Module and curing module, it is characterised in that:

The form of station dial is presented in the workbench, and the switching of each station, these works are executed by the rotation of itself Position successively includes the positioning and clamping station of curved surface, the elevation carrection station of curved surface, multiple EFI print and precuring station, Yi Jizhi Measure detection station；In addition, being equipped with the fixture for clamping curved surface on each station, and each station can be mutually indepedent Ground executes relevant operation；

The side of the station dial is arranged in the loading and unloading module comprising machinery of the end equipped with vacuum chuck Arm, and for will periodically be adsorbed to the curved surface of operation, and be transferred to each station or removed from it；

The EFI impression block includes more set jet-printing heads, these jet-printing heads correspond to each EFI print and precuring station and It sets up one by one, and each jet-printing head has the one-movement-freedom-degree in tri- axis direction of XYZ respectively, and along station dial Thus radial freedom degree adjusts the relative position between curved surface；

The vision module includes that positioning camera, measurement camera, detection camera, substrate observation camera and jet stream observe camera, In the positioning camera be installed on the top of the positioning and clamping station, and for observing and determining curved surface on the fixture just True installation site；The measurement camera is installed on the top of the elevation carrection station, the altitude feature for real-time measurement curved surface Then information instructs the movement of the jet-printing head with this, to ensure to realize constant height between its nozzle and curved surface, and according to This selects nozzle to be combined into required linear array；The detection camera is installed on the top of the quality testing station, and for song Spray printing quality on face executes detection；In addition, the nozzle of the substrate observation camera and each jet-printing head is pacified in parallel It fills and moves together therewith, and for executing vision positioning to determine the initial position of spray printing, simultaneously before executing EFI print Established pattern is shot in entire jet printing process；The ink droplet body that jet stream observation camera is used to spray the jet-printing head Product executes image and shoots and measure online；

The curing module includes precuring device and final curing device, wherein each precuring device corresponds to each spray It prints head and is arranged and moves together therewith, and for being carried out to curved surface primary pre- after the jet-printing head completes each spray printing Curing operation；The side of the station dial is then arranged in the final curing device, and for holding to the global pattern on curved surface Row is last to be fully cured.

2. 3D curved surface EFI being patterned equipment as described in claim 1, which is characterized in that the jet-printing head respectively includes spray The annular electrode below the nozzle and being grounded is arranged in, for generating electric field between the nozzle and the annular electrode in mouth High pressure generator, and be stored with ink and keep the spray printing container that is connected to the nozzle；At work, in electric field force Under inducing action, ink forms taylor cone on the top of the nozzle, and drop continues to project from the top of the taylor cone and in electricity It is broken into a large amount of droplet under the action of field force, and then realizes the patterning operations to curved surface.

3. 3D curved surface EFI being patterned equipment as claimed in claim 2, which is characterized in that the nozzle of the jet-printing head is single Nozzle or the array nozzle collectively formed by multiple small nozzles；When using the form of array nozzle, each small nozzle It is arranged with certain difference in height, and executes injection in following state: being thrown in perpendicular the small nozzle bottom end being selected Curve where shadow is set to and to keep substantially conformal between the curved surface transversal of spray printing.

4. 3D curved surface EFI being patterned equipment as claimed in any one of claims 1-3, which is characterized in that each spray Head is printed equipped with the ink of identical or different material, and the spray printing for executing curved surface different zones, be achieved in multilayer complexity The EFI of pattern prints.

5. 3D curved surface EFI being patterned equipment as claimed in any one of claims 1-3, which is characterized in that for the survey For measuring camera, the measurement of curved surface altitude feature information is executed by the way of monocular vision, and including measuring rack, putting down Line light source component, height detection camera and range sensor, in which:

The measurement rack is in the form of horizontally disposed symmetrical cross frame, and the installation foundation as other assemblies；

The quantity of the source of parallel light component is four, and each is mounted on the end of four identical arm configurations of the measurement rack End lower section, and can drive rotated so that its projected angle changes via matched motor respectively；Each source of parallel light Component sets up parallel light tube inside this mounting box separately by mounting box and successively respectively and transmission grating collectively constitutes, In the parallel light tube be used for the transmission grating emitting parallel light beam, be then carved on the transmission grating width alternate two kinds it is flat Row indentation so that the collimated light beam that the parallel light tube issues can be projected on curved surface to be measured to be formed it is light and dark parallel Striped；

The quantity of the height detection camera is only one, it be fixedly mounted on it is described measurement rack center lower section, and with it is each The source of parallel light component matches, for be formed by curved surface to be measured parallel stripes execution adopt figure to obtain required two Tie up image；

The range sensor corresponds respectively to each source of parallel light component and is arranged, and when by adjusting the measurement When the height of rack makes the height detection camera can get the clearly two dimensional image, it is used under this position to described The optical center of lens of height detection camera is measured to the vertical range H between X " Y " plane, while for this height detection The depth of parallelism between the imaging plane of camera and X " Y " plane is detected, wherein the X " Y " plane is believed in altitude response A reference planes of institute's built in advance before breath measurement, and it is built with using the optical center of lens of the height detection camera by origin Vertical horizontal X Y plane holding is parallel to each other.

6. 3D curved surface EFI being patterned equipment as claimed in claim 5, which is characterized in that respectively for the transmission grating For the wide seam of the light transmission in light transmission gap having with for light transmission narrow slit, their position carries out coding row by n binary modes Sequence, and to this n × 2ⁿLight penetrating slit is encoded；Wherein the value of n is determined according to the visual field size of the detection camera, and Ensure so that fringe number m should meet m > 3n-1 in detection camera image obtained；In addition, the light transmission narrow slit d₂With institute State the wide seam d of light transmission₁Between wide-to-narrow ratio meet formula d₁/d₂≥2。

7. a kind of method for executing 3D curved surface EFI print using device as claimed in claim 5, which is characterized in that this method Include the following steps:

(a) curved surface to spray printing is given by vacuum suction by the mechanical arm, and is transferred to the first station of the workbench Namely at the positioning and clamping station；

(b) the correct installation site of curved surface is determined by the positioning camera first, then the mechanical arm is according to this position It discharges curved surface, and curved surface is sucked by fixture and completes clamping；

(c) workbench is converted to next station namely the elevation carrection station, and is completed by the measurement camera to song The measurement of face altitude feature information operates；

(d) workbench is converted to first on next station namely multiple EFI print and precuring station, and by described Jet-printing head executes the electrofluid spray printing of the first pattern to curved surface, and it is pre- solid then to execute surface layer to ink by the precuring device Change；Then, continue conversion to remaining EFI print and precuring station, carry out subsequent pattern spray printing and precuring operation, directly To the patterning for completing entire curved surface；

(e) workbench is converted to next station namely quality testing station, and by the detection camera to the spray on curved surface Print quality executes detection；Then, the mechanical arm removes the curved surface examined, and is sent into final curing equipment to the entirety on curved surface Pattern carries out final curing；

(f) mechanical arm will complete cured curved surface and be put into finished product area, and be ready for feeding next time.

8. the method for claim 7, which is characterized in that in step (c), the measurement camera is using monocular vision Mode executes the measurement process of curved surface altitude feature information, in which:

(c1) a camera rectangular coordinate system XYZ is established as origin using the optical center of lens of the height detection camera, wherein should The optical axis coincidence of the Z axis of camera rectangular coordinate system and the height detection camera and the lower section for being directed toward the detection camera, X-axis, Y Axis meets the right-hand rule, and two holdings in four source of parallel light components are symmetrically in this X-axis, two remaining It is same to keep being symmetrically in this Y-axis；Similarly, it is established by origin of the center of the imaging plane of the height detection camera One image rectangular coordinate system X ' Y ' Z, wherein the Z axis phase of the Z axis of the image rectangular coordinate system and the camera rectangular coordinate system It is overlapped, X ' axis, Y ' axis equally meet the right-hand rule；Then, a reference is established immediately below the height detection camera Rectangular coordinate system X " Y " Z, wherein this refers to the Z axis of rectangular coordinate system and the optical axis coincidence of the detection camera, X " axis, Y " axis Equally meet the right-hand rule, and its X " Y " plane keeps being parallel to each other with the X/Y plane of the camera rectangular coordinate system；

(c2) its range information for arriving the X " Y " plane is measured respectively first with four range sensors, according to gained Range information adjusts X " Y " plane pose, makes itself and the detection camera imaging plane keeping parallelism；Meanwhile to the distance Difference between sensor and the detection camera photocentre in Z-direction compensates, and then measures and determines the detection phase The optical center of machine is to the vertical range H between the X " Y " plane；

(c3) the alternate bright fringes of width are projected on curved surface to be measured using source of parallel light component described in one group, and use institute Stating motor drives the source of parallel light component to rotate, so that the slow inswept entire region to be measured of striped；The detection camera adopts figure, and Write down the projected angle α of each image；Then, it is successively repeated the above steps using source of parallel light component described in three groups of residue, respectively Four groups of images in region to be measured under the striped projected to the source of parallel light component described in four groups；

(c4) obtained four groups of images are directed to, calculates separately to obtain each source of parallel light component and be thrown on curved surface to be measured Any point P to be formed on striped is penetrated in the deflection of Z-direction, and then find out reality in such a way that weighting is averaged to calculate Border deflection；

(c5) traverse measurement rack, successively complete curved surface to be measured of traversal, repeats step (c2) to step (c4), until obtaining Until obtaining the entirely elevation information of curved surface all the points to be measured, whole curved surface height measurement process is thus completed.