CN112571990A - High-precision color spraying machine and printing method thereof - Google Patents
High-precision color spraying machine and printing method thereof Download PDFInfo
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- CN112571990A CN112571990A CN202011447297.8A CN202011447297A CN112571990A CN 112571990 A CN112571990 A CN 112571990A CN 202011447297 A CN202011447297 A CN 202011447297A CN 112571990 A CN112571990 A CN 112571990A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J3/00—Typewriters or selective printing or marking mechanisms characterised by the purpose for which they are constructed
- B41J3/407—Typewriters or selective printing or marking mechanisms characterised by the purpose for which they are constructed for marking on special material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J29/00—Details of, or accessories for, typewriters or selective printing mechanisms not otherwise provided for
- B41J29/38—Drives, motors, controls or automatic cut-off devices for the entire printing mechanism
- B41J29/393—Devices for controlling or analysing the entire machine ; Controlling or analysing mechanical parameters involving printing of test patterns
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/70—Determining position or orientation of objects or cameras
- G06T7/73—Determining position or orientation of objects or cameras using feature-based methods
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Abstract
The invention relates to a high-precision color spraying machine which comprises a conveying device, a spraying and printing device and a PC (personal computer), wherein the conveying device is used for conveying coins to move along a preset movement track; the precision control system is used for acquiring the motion error of the coin and adjusting the printing parameters of the coin according to the motion error; and the printer head is used for carrying out spray printing operation on the coins according to the adjusted printing parameters. The invention has the advantages that the printing precision of the coin in the moving direction can be effectively improved, and the printing precision of the coin in the X direction can be controlled within +/-0.1 mm.
Description
Technical Field
The invention relates to a high-precision color spraying machine and a printing method thereof.
Background
When the coin surface is sprayed with colorful patterns, the colorful patterns are generally printed by a color spray printing machine. The color jet printing machine has high requirements on the positioning precision of the coin in the printing process, however, the positioning is usually realized by adjusting the posture of the coin in the prior art, an effective printing positioning means is not provided, the precision of the coin in the moving process is difficult to ensure, and the printing precision control deviation is large.
According to the knowledge, the existing color spray machine mainly depends on a main encoder to record the position information of the X direction, the main encoder is limited by installation conditions and can only be installed on a synchronous belt driven wheel, the motion track of each sliding table of 78 sliding tables on an annular guide rail cannot be directly fed back, the sliding table and the synchronous belt are in flexible connection, gaps exist between the sliding table and the synchronous belt, the synchronous belt can also have slipping phenomenon and plastic deformation phenomenon on the driven wheel, therefore, the motion position information of coins on the sliding table recorded by the main encoder has large errors, although the synchronous belt is controlled to drive to move at a constant speed after being set by a servo motor, the displacement deviation of about +/-1 mm in the X motion direction of a single sliding table still exists, the errors are directly fed back to the printing precision, and the printing precision can only be controlled to be about +/-1 mm.
Disclosure of Invention
The invention aims to: aiming at the defects in the prior art, the high-precision color spray machine and the printing method thereof are provided, and the motion error of the color spray machine can be corrected by adopting the equipment and the method, so that the printing precision is controlled within 0.1 mm.
In order to achieve the above purpose, the invention provides a high-precision color spraying machine, which comprises a conveying device, a spraying and printing device and a PC (personal computer), wherein the conveying device is used for conveying coins to move along a preset movement track; the precision control system is used for acquiring the motion error of the coin and adjusting the printing parameters of the coin according to the motion error; and the printer head is used for carrying out spray printing operation on the coins according to the adjusted printing parameters.
Preferably, the precision control system comprises a main encoder, a positioning camera, a main photoelectric sensor and a plurality of auxiliary photoelectric sensors, wherein the main encoder is mounted on a synchronous belt driven wheel of the annular track and used for detecting the movement distance of a sliding table on the annular track in the X direction; the positioning camera is arranged at the inlet of the printer head and used for collecting image information of the coin to be jet-printed; the main photoelectricity is arranged below the positioning camera, the auxiliary photoelectricity is installed at a sprayer module of the printer head, and the main photoelectricity and the auxiliary photoelectricity are sequentially triggered when a coin to be subjected to spray printing moves to the printer head along the annular track.
The invention can reposition the coin on the sliding table by the main encoder for secondary positioning and the auxiliary photoelectricity arranged at the nozzle of the printer head. Therefore, after the main encoder counts, the main encoder needs to count again every time the coin passes through the auxiliary photoelectric device once so as to correct the calculation error and control the movement precision deviation of the coin within 0.1 mm.
Preferably, the auxiliary photoelectric device is arranged below a spray head of the spray head module, the positioning camera and the printer head are both arranged above the annular track, and the main encoder, the positioning camera, the main photoelectric device and the auxiliary photoelectric device are all connected with a PC.
Preferably, the printer head comprises a group of sprayer modules, one or two sprayers are arranged on each sprayer module, and an auxiliary photoelectric device is correspondingly arranged below each sprayer.
Preferably, the conveying device comprises an annular track and a driving mechanism for driving the annular track to move, a group of sliding tables for bearing coins are arranged on the annular track, and the sliding tables can move along the annular track.
Preferably, a rotary gap feeding station, a visual positioning station, an ink-jet printing station, a color quality inspection station, a qualified product eliminating station and a defective product output station are sequentially arranged on the annular track along the conveying direction of the annular track, a gloss oil quality inspection station is arranged at the qualified product eliminating station, a coin feeding device is arranged at the rotary gap feeding station, the visual positioning station is provided with a positioning camera and a matched light source of a precision control system, the ink-jet printing station is provided with a printer head, the color quality inspection station is provided with a first inspection camera and a matched light source, the qualified product eliminating station and the defective product output station are respectively provided with a coin shifting mechanism, and the gloss oil quality inspection station is provided with a second inspection camera and a matched light source.
The invention also provides a printing method of the high-precision color spray machine, which comprises the following steps:
placing the coins on a conveying device, wherein the conveying device drives the coins to move according to a preset movement track;
and a precision control system in the spray printing device acquires a motion error generated in the conveying process of the coin, adjusts the printing parameters of the coin according to the motion error, and the printer head performs spray printing operation on the coin according to the adjusted printing parameters.
The precision control method of the color spray machine comprises the following steps:
the method comprises the steps that firstly, coins are arranged on a sliding table and move along an annular track, the coins trigger a positioning camera through main photoelectricity to acquire coin images so as to obtain a relative position difference value between the coin images and a coin template, and meanwhile, the numerical value of a main encoder is recorded as position information of the coins in the X direction when the coins pass through the main photoelectricity; turning to the second step;
secondly, the coins continuously follow the annular track to move along with the sliding table, and when the coins enter the lower part of the nozzle module, the coins pass through an auxiliary photoelectric trigger main encoder of the nozzle module to record the numerical value of the coins as position information of the coins in the X direction when the coins pass through the auxiliary photoelectric trigger main encoder; turning to the third step;
and thirdly, determining printing parameters according to the relative position difference between the coin image and the coin template and the position information of the coin in the X direction when the coin passes through the main photoelectricity and the auxiliary photoelectricity, and spraying and printing patterns on the coin by a nozzle corresponding to the auxiliary photoelectricity on the nozzle module according to the printing parameters.
In the first step, triggering a main photoelectric sensor when the coin passes through the main photoelectric sensor, sending a trigger signal to a PC (personal computer), controlling a positioning camera by the PC to photograph and collect images of the coin in motion, comparing the collected images of the coin in motion with a coin template stored in the PC by the PC to obtain a relative position difference value between the coin in motion and the coin template prestored in the PC, wherein the relative position difference value comprises a relative difference value of the coin in the X, Y direction and a rotation angle difference value of the coin, and the relative position difference values are respectively marked as delta X, delta Y and delta theta; when the coin passes through the main photoelectric sensor, the PC controls the main encoder to record the value of the coin as position information in the X direction when the coin passes through the main photoelectric sensor, and the position information is recorded as X1.
In the first step, a specific method for acquiring the relative position difference between the coin in motion and a coin template prestored in the PC is as follows:
the center positions x, y of the coin in the inspection image are compared with the center positions x1, y1 of the coin in the template image to calculate X, Y shifts, i.e. deltax, deltay,
Δx＝x-x1
Δy＝y-y1
meanwhile, the image characteristic region converts two-dimensional data into one-dimensional data through image polar coordinate conversion, and then carries out NCC template matching with the similarly processed one-dimensional template data to calculate the horizontal deviation of the image characteristic region, wherein the deviation represents the angular deviation delta theta (namely delta theta is NCC),
wherein Nrows and Ncoles respectively represent the row and column numbers of the detection image and the template image, and v1(k，l)、v2(k, l) respectively represent pixel values of the detection image and the template image at a point (k, l),
respectively representing the mean gray values, σ, of the inspection image and the template image2(v1)、σ2(v2) Respectively representing the variance of the pixel values of the detection image and the template image.
The image polar coordinate conversionThe method is characterized in that a circular ring area with representative features of the coin is converted into a long strip image, so that the angle information of the coin is converted into the horizontal direction deviation of the image, and the relationship between the converted image and the image before conversion can be calculated by calculating the Cartesian coordinates
The polar coordinate transformation (θ, r) as the center is expressed by the following calculation formula:
where r represents a radius and θ represents an angle.
The invention converts the image information from a plane coordinate to a polar coordinate system, successfully reduces two-dimensional operation to one-dimensional operation, greatly reduces the operation time of the positioning algorithm, has higher algorithm efficiency, can realize the positioning requirement with higher precision, reaches the positioning precision of 0.02mm, and meets the requirement of continuous online operation of equipment.
In the second step, the auxiliary photoelectric sensor is triggered when the coin passes through the auxiliary photoelectric sensor, the auxiliary photoelectric sensor sends a trigger signal to the PC, and then the PC controls the main encoder to record the value of the coin at the moment as the position information of the coin in the X direction when the coin passes through the auxiliary photoelectric sensor, and the position information is recorded as X2.
In the third step, the movement distance of the coin from the main photoelectric sensor to the auxiliary photoelectric sensor in the X direction is recorded as S, the expected position information of the coin when passing through the auxiliary photoelectric sensor is S1, the actual position information is S2, the expected position and the actual position of the coin when passing through the auxiliary photoelectric sensor are calculated according to the following formula,
S1＝X1+S (1)
S2＝X2 (2)
then, the actual position of the coin passing through the auxiliary photoelectric sensor is compared with the expected position to obtain the difference Delta S between the actual position and the expected position, the difference between the actual position and the expected position is calculated according to the following formula,
ΔS＝S2-S1 (3)
finally, it is determined whether the value of Δ S is within the design range, and if Δ S is within the design range, the value X2 recorded by the main encoder is used as the printing start point in the X direction, and if Δ S is not within the design range, the expected position S1 is used as the printing start point in the X direction.
In the present invention, since the distance S in the X movement direction from the main photo to the auxiliary photo under each nozzle is fixed and the movement speed V1 of the entire circular track is also constant, the position information S1 of the coin passing the auxiliary photo can be predicted to be X1+ S based on the position information X1 recorded after the coin triggers the main photo. In addition, because the coins are flatly placed on the sliding table of the annular track, the precision of the annular track in the Y motion direction is kept within plus or minus 0.02mm, the coins can be ignored, and meanwhile, the coins move on the sliding table at a constant speed along with the sliding table, and the rotation angle theta of the coins is also kept unchanged, so that the motion precision error of the coins is mainly generated in the X motion direction, and therefore, an auxiliary photoelectric device is required to be arranged at each spray head for secondary positioning, so that the error is reduced.
The invention has the advantages that the secondary positioning is carried out on the coin by adopting the auxiliary photoelectricity, the printing precision of the coin in the moving direction can be effectively improved, and the printing precision of the coin in the X direction can be controlled within +/-0.1 mm.
Drawings
The invention will be further described with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a high-precision color spraying machine according to the present invention.
Fig. 2 is a flow chart of a printing method of the high-precision color spray machine according to the invention.
Fig. 3 is a schematic diagram of the precision control process of the color spray machine of the invention.
Fig. 4 is a schematic block diagram of a color spray machine precision control system according to the present invention.
Fig. 5 is a logic block diagram of the precision control process of the color spray machine in the invention.
FIG. 6 is a logic diagram of a coin positioning algorithm of the present invention.
FIG. 7 is a schematic structural view of an ion wind processing apparatus according to the present invention.
Fig. 8 is a schematic structural view of a coin feeding device according to the present invention.
Fig. 9 is a schematic structural view of the printer head of the present invention.
FIG. 10 is a schematic view of a showerhead module according to the present invention.
Detailed Description
Example one
As shown in fig. 1, a high-precision color inkjet printer includes a frame 13, a conveying device 14, an inkjet printing device and a PC. The conveying device 14 is arranged on the rack 13 and used for conveying the coins to move in a preset movement track; the PC is connected with the conveying device 14 and the jet printing device and used for receiving signals collected by the conveying device 14 or/and the jet printing device and sending control signals to the conveying device 14 and the jet printing device; the spray printing device comprises a printer head and a precision control system, wherein the precision control system is used for acquiring the movement error of the coin and adjusting the printing parameter of the coin according to the movement error, and the printer head performs spray printing operation on the coin according to the adjusted printing parameter.
The conveying device 14 includes an endless track on which a plurality of slide tables for carrying coins are provided, and a drive mechanism that drives the endless track to move, and the slide tables are movable along the endless track. The circular track is composed of a synchronous belt, a driven wheel and a driving wheel, the driving wheel is connected with a driving mechanism (namely a motor), and the synchronous belt moves by driving the driving wheel to rotate.
In addition, a rotary gap feeding station 3, a visual positioning station 4, an ink-jet printing station 5, a color quality inspection station 6, a qualified product eliminating station 7 and an unqualified product output station 11 are sequentially arranged on the annular track along the conveying direction of the annular track, and a gloss oil quality inspection station 8 is arranged at the qualified product eliminating station 7. Still be equipped with vision inspection turn-over station 1 and ion wind processing station 2 on the frame 13, vision inspection turn-over station 1 is equipped with vision inspection turn-over device, and ion wind processing station 2 is equipped with ion wind processing apparatus, is equipped with coin feed arrangement at rotation clearance feed station 3, and coin feed arrangement links up with ion wind processing apparatus mutually, and ion wind processing apparatus is connected with vision inspection turn-over device. Visual positioning station 4 is equipped with the location camera and the supporting light source of accuracy control system, inkjet printing station 5 is equipped with the printer head, color quality inspection station 6 is equipped with first inspection camera and supporting light source, certified products rejection station 7 is equipped with first group coin mechanism for transport the coin that is located on the circular orbit slip table to band conveyer, carry to gloss oil quality inspection station 8 via band conveyer again, defective products output station 11 is equipped with the second respectively and dials coin mechanism, be used for playing the endless orbit with unqualified waste product. The gloss oil quality inspection station 8 is provided with a second inspection camera and a matched light source. The positioning camera, the first inspection camera, the second inspection camera and the matched light source thereof are respectively in communication connection with the camera controller, and the camera controller is connected with the PC. And a good product deep curing LED lamp 9 is arranged between the qualified product eliminating station 7 and the gloss oil quality inspection station 8 on the frame 13, and deep curing is carried out on the eliminated qualified product so as to facilitate subsequent gloss oil visual inspection. A waste deep curing LED lamp 10 is arranged between the qualified product eliminating station 7 and the unqualified product output station 11, and deep curing is carried out on the unqualified products conveyed by the annular rail, so that the waste eliminated by the unqualified product eliminating station 11 is prevented from polluting a production line due to the fact that printing ink is not dry.
The vision inspection turn-over device includes image acquisition module and coin turn-over mechanism, and image acquisition module gathers coin surface image and conveys to the PC, and the PC confirms whether need carry out the turn-over to the coin according to image information, if needs then coin turn-over mechanism carries out the turn-over to the coin, otherwise the coin is not the turn-over direct current. As shown in fig. 7, the ion wind processing device includes a plasma wind generator 19, a gas pipe 18, an ion wind cover 17 and a column 15, the plasma wind generator 19 and the ion wind cover 17 are both installed on the column 15, the plasma wind generator 19 is communicated with the ion wind cover 17 through the gas pipe 18, an air outlet of the ion wind cover 17 faces downwards vertically, and blows ion wind to the surface of the coin towards the coin transported on the belt conveyor. The ion wind cover 17 is connected with the vacuum joint 16, and ozone generated at the ion wind treatment station 2 is discharged through the vacuum joint 16.
As shown in fig. 8, the coin feeding device includes a feeding frame, a feeding belt conveyor 20, an indexing disc 21 and a DD motor 22, the indexing disc 21 is arranged on the feeding frame, the indexing disc 21 is arranged at the discharging end of the feeding belt conveyor 20, the DD motor 22 drives the indexing disc 21 to intermittently rotate, a plurality of arc-shaped grooves are uniformly distributed in the circumferential direction of the indexing disc 21, and a position detection hole is arranged above the arc-shaped groove at one side of the indexing disc 21. When the coins are conveyed to the arc-shaped groove at the coin inlet of the dividing plate 21 by the feeding belt conveyor 20, the in-place coin detection photoelectricity above the in-place detection hole at the arc-shaped groove is triggered to detect the coins so as to ensure that the coins are in place, and the DD motor 22 drives the dividing plate 21 to rotate for 30 degrees to drive the coins at the coin inlet to move to the next station.
As shown in fig. 9, the printer head includes a head assembly vertical plate 23 and a head assembly sliding plate 24 capable of sliding along the head assembly vertical plate 23, a lifter 25 for driving the head assembly sliding plate 24 to slide up and down is arranged on the head assembly vertical plate 23, the head assembly sliding plate 24 is provided with seven nozzle modules 26, the head assembly modules are respectively a primer printing nozzle module, a white-bottom printing nozzle module, a yellow printing nozzle module, a rose printing nozzle module, a cyan printing nozzle module, a black printing nozzle module, the nozzle modules 26 pass through a telescopic arm 27 and the head assembly vertical plate 23, seven pre-curing LED lamps 12 are arranged on the head assembly sliding plate 24, and the pre-curing LED lamps 12 are arranged on the rear side of the nozzle modules 26 to facilitate pre-curing of sprayed and printed coins immediately. As shown in fig. 10, the nozzle module 26 includes a head cover 28, a head riser 29 and a head floor 30, the head cover 28, the head riser 29 and the head floor 30 are connected to form a cavity, two nozzles 31 and a board 32 for controlling the two nozzles 31 are disposed in the cavity, and the nozzles 31 are connected to the ink cartridge. The nozzle module 26 adopts a dual-nozzle design, and adds a nozzle for compensation, so as to reduce the ink blocking probability and the line leakage phenomenon during jet printing.
As shown in fig. 2, a printing method of a high-precision color inkjet printer includes the following steps:
after the coins are inspected and turned over by the visual inspection turning-over device, the surface of the coins is subjected to surface treatment by the ion wind treatment device so as to enhance the surface tension of the coins;
the coins processed by the ion wind enter the annular track of the conveying device 14 through the coin feeding device, are placed on the sliding table of the annular track, and move in a preset annular track under the driving of the annular track;
visually positioning the coins passing through the printer head through a precision control system to obtain movement errors generated in the conveying process of the coins, adjusting printing parameters of the coins according to the movement errors, and performing spray printing and solidifying operation on the coins by the printer head according to the adjusted printing parameters;
and carrying out color quality inspection and gloss oil visual quality inspection on the coin subjected to jet printing.
The color quality inspection is to collect images of the sprayed and printed coins through a first inspection camera and send the collected image information to a PC (personal computer), the PC judges whether the surface color quality of the coins is qualified or not according to the image information, if the surface color quality of the coins is qualified, a first coin shifting mechanism rejects the coins, and the rejected qualified coins are conveyed to a gloss oil inspection station 8 through a belt conveyor for gloss oil inspection; if the color quality of the surface of the coin is unqualified, the coin is continuously conveyed by the annular track and is rejected by the second coin shifting mechanism at the unqualified product output station 11.
And in the gloss oil visual inspection, the second inspection camera is used for acquiring images of the coins with qualified surface color quality and sending acquired image information to the PC, the PC is used for judging whether the gloss oil quality of the coins is qualified or not according to the image information, and if the gloss oil quality of the coins is qualified, a final finished product is output, and if the gloss oil quality of the coins is not qualified, the finished product is treated as a waste product.
As shown in fig. 4, the precision control system includes a main encoder, a positioning camera (i.e., an industrial area-array camera), a main photo and 12 auxiliary photo, and the main encoder, the positioning camera, the main photo and the auxiliary photo are all connected to a PC. The main encoder is arranged on a synchronous belt driven wheel of the annular track and used for detecting the movement distance of the sliding table on the annular track in the X direction; the positioning camera is arranged at the inlet of the printer head and used for collecting image information of the coins to be jet-printed; the main photoelectricity is arranged below the positioning camera, the auxiliary photoelectricity is arranged at the sprayer module of the printer head and below the sprayer of the sprayer module, and the main photoelectricity and the auxiliary photoelectricity are sequentially triggered when a coin to be sprayed and printed moves to the printer head along with the annular track. The main photoelectricity and the auxiliary photoelectricity adopt opposite laser photoelectricity. The positioning camera and the printer head are both arranged above the annular track. A group of sliding tables for bearing coins are arranged on the annular track, and the sliding tables can move along the annular track. The printer head comprises seven sprayer modules, one or two sprayers are arranged on each sprayer module, 12 sprayers are arranged, an auxiliary photoelectric part is correspondingly arranged below each sprayer, a pre-curing LED lamp 12 is arranged on the rear side of each sprayer module, and the surface of a coin which is sprayed and printed by the sprayer modules at each time is pre-cured.
A method for controlling the accuracy of a color spray machine, as shown in fig. 3 and 5, comprising the following steps:
the method comprises the steps that firstly, coins are arranged on a sliding table and move along an annular track, the coins trigger a positioning camera through main photoelectricity to acquire coin images so as to obtain a relative position difference value between the coin images and a coin template, and meanwhile, the numerical value of a main encoder is recorded as position information of the coins in the X direction when the coins pass through the main photoelectricity;
secondly, the coins continuously follow the annular track to move along with the sliding table, and when the coins enter the lower part of the spray head module, the coins pass through a first auxiliary photoelectric trigger main encoder of the spray head module to record the numerical value of the coins as position information of the coins in the X direction when the coins pass through the first auxiliary photoelectric trigger main encoder;
thirdly, determining printing parameters according to the relative position difference between the coin image and the coin template and the position information of the coin in the X direction when the coin passes through the main photoelectricity and the first auxiliary photoelectricity, and spraying and printing patterns on the coin by a first nozzle on the nozzle module, which corresponds to the first auxiliary photoelectricity, according to the printing parameters;
and fourthly, the coin follows the sliding table to continue to follow the annular track to move, the operation of the second step and the operation of the third step are repeated when the coin passes through the second auxiliary photoelectric part of the nozzle module, and the operation is circulated until the coin passes through the printer head.
In the first step, the main photoelectricity is triggered when the coin passes through the main photoelectricity, the main photoelectricity sends a trigger signal to a PC (personal computer), then the PC controls a positioning camera to photograph and collect images of the coin in motion, the positioning camera transmits the collected images to the PC, the PC compares the collected images of the coin in motion with a coin template stored in the PC, and further compares the position information of the coin collected by the positioning camera with the position information of the template prestored in the PC to obtain a relative position difference value between the coin in motion and the coin template prestored in the PC, wherein the relative position difference value comprises a relative difference value of the coin in the horizontal X, Y direction and a rotation angle difference value of the coin, and the relative position difference values are respectively marked as delta X, delta Y and delta theta; when the coin passes through the main photoelectric sensor, the PC controls the main encoder to record the value of the coin as position information in the X direction when the coin passes through the main photoelectric sensor, and the position information is recorded as X1.
The embodiment selects the coaxial light source with good imaging consistency on the metal surface by matching the industrial area-array camera with a proper industrial lens, and performs imaging reduction on the coin appearance and the pattern outline. After imaging is finished, the industrial area-array camera transmits acquired image data information to an image processing unit of a PC through high-speed data transmission, and the image processing unit processes and analyzes the received image data information through an image processing algorithm to calculate X offset, Y offset and angle offset theta of the coin. The image processing algorithm (i.e. the positioning algorithm) matches each image to be positioned with a standard template pre-stored in the image processing unit by a template matching technique, calculates a deviation value thereof, and realizes high-precision positioning, and a logic block diagram of the algorithm is shown in fig. 6 ("the detection template" refers to the aforementioned "standard template").
In the first step, the specific method for acquiring the relative position difference between the coin in motion and the coin template prestored in the PC is as follows:
the center positions x, y of the coin in the inspection image are compared with the center positions x1, y1 of the coin in the template image to calculate X, Y shifts, i.e. deltax, deltay,
Δx＝x-x1
Δy＝y-y1
meanwhile, the image characteristic region converts two-dimensional data into one-dimensional data through image polar coordinate conversion, and then carries out NCC template matching with the similarly processed one-dimensional template data to calculate the horizontal deviation of the image characteristic region, wherein the deviation represents the angular deviation delta theta (namely delta theta is NCC),
wherein Nrows and Ncoles respectively represent the row and column numbers of the detection image and the template image, and v1(k，l)、v2(k, l) respectively represent pixel values of the detection image and the template image at a point (k, l),
respectively representing the mean gray values, σ, of the inspection image and the template image2(v1)、σ2(v2) Respectively representing the variance of the pixel values of the detection image and the template image.
The image polar coordinate conversion is to convert the circular ring area with representative features of the coin into a long strip image, so that the angle information of the coin is converted into the horizontal deviation of the image, and the relationship between the converted image and the image before conversion can be calculated by Cartesian coordinate
The polar coordinate transformation (θ, r) as the center is expressed by the following calculation formula:
where r represents a radius and θ represents an angle.
And the template matching part adopts a matching algorithm based on similarity measurement, uses the gray scale of the image to be positioned (namely the acquired coin image in motion) and the template to calculate the matching degree between the two through a normalized correlation measurement formula.
The traditional template matching algorithm solves the rotation problem, expects to obtain a high-precision positioning result and needs more matching times. If the angular positioning precision is 0.1 degree, 3600 times of rotation and matching of the image are needed, and the algorithm efficiency is poor. The positioning system of the embodiment converts the image information from a plane coordinate to a polar coordinate system, successfully reduces two-dimensional operation to one-dimensional operation, greatly reduces the operation time of the positioning algorithm, has higher algorithm efficiency, can realize the positioning requirement with higher precision, reaches the positioning precision of 0.02mm, and meets the requirement of continuous online operation of equipment.
In the second step, the first auxiliary photoelectric device is triggered when the coin passes through the first auxiliary photoelectric device, the first auxiliary photoelectric device sends a trigger signal to the PC, and then the PC controls the main encoder to record the value of the coin at the moment as the position information of the coin in the X direction when the coin passes through the first auxiliary photoelectric device, and the position information is recorded as X2.
In the third step, the first nozzle starts to print the pattern according to the values of Δ X, Δ Y and Δ θ obtained in the first step and in combination with the value X2 of the main encoder when the first auxiliary photo-electricity is triggered in the second step.
The expected position information of the coin passing through the auxiliary photoelectric sensor is S1 and the actual position information is S2, the expected position and the actual position of the coin passing through the auxiliary photoelectric sensor are calculated according to the following formula,
S1＝X1+S (1)
S2＝X2 (2)
when the first auxiliary photoelectric sensor is triggered, the actual position S2 (X2) when the coin passes through the auxiliary photoelectric sensor is compared with the expected position S1 (X1 + S) to obtain the difference Delta S between the actual position and the expected position, the difference between the actual position and the expected position is calculated according to the following formula,
ΔS＝S2-S1 (3)
the difference Δ S is due to motion accuracy errors and cannot be eliminated. Judging whether the value of the delta S is in a design range, if the delta S is in the design range (the design range generally takes the value of +/-2.6 mm), adopting a numerical value X2 recorded by a main encoder as a printing initial position point in the X direction, issuing printing position data to a nozzle printing board card by combining the delta X, the delta Y and the delta theta, controlling the nozzle to start printing, and starting printing by adopting X2 as a starting point at the moment so as to effectively improve the printing precision in the movement direction; if the Δ S is not within the design range, that is, the difference Δ S is too large, the predicted position S1 is used as the starting point of the print starting position in the X direction, and print position data is issued to the head print board card in combination with Δ X, Δ Y, and Δ θ, so that the head is controlled to start printing.
The coin is in keeping flat on annular guide's little slip table after advancing coin graduated disk, and little slip table moves along the guide rail X direction along with the synchronous belt this moment, and its Y direction relies on guide rail self precision to keep can reaching 0.02mm, and the coin is in the synchronization state on little slip table, does not have relative displacement, and its motion state is equal to the motion state of little slip table. When the coins pass through the main photoelectric sensor, the positioning camera is triggered to take a picture, at the moment, the relative position data delta X, delta Y and delta theta of the coins are obtained through comparison between a template prestored in the upper computer and an actual picture taking position, the three data are used as basic data of a later nozzle printing draft position and are issued to a nozzle printing board card of a printer head, and then the initial position is printed by combining the nozzle, so that the overall printing precision can be controlled. Except that direction of motion X, its Y to and rotatory Z to acquiescence do not change, and X is to owing to receive the hold-in range to pull, and the hold-in range has flexible tensioning deformation, and because the velocity of motion is not absolute at the uniform velocity, has certain error, need carry out secondary trigger with supplementary photoelectricity to the printing position that is closest to the shower nozzle is as printing the initial point, can effectively reduce the accumulative error that long distance X direction motion caused.
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (10)
1. The utility model provides a high accuracy colour inkjet machine, includes conveyor, spouts seal device and PC, conveyor is used for carrying the coin with the motion trail motion of predetermineeing, PC links to each other its characterized in that with conveyor, spout the seal device: the spray printing device comprises a printing head and a precision control system; the precision control system is used for acquiring the motion error of the coin and adjusting the printing parameters of the coin according to the motion error; and the printer head is used for carrying out spray printing operation on the coins according to the adjusted printing parameters.
2. The high-precision color spraying machine according to claim 1, characterized in that: the precision control system comprises a main encoder, a positioning camera, a main photoelectric sensor and a plurality of auxiliary photoelectric sensors, wherein the main encoder is arranged on a synchronous belt driven wheel of the annular track and used for detecting the movement distance of a sliding table on the annular track in the X direction; the positioning camera is arranged at the inlet of the printer head and used for collecting image information of the coin to be jet-printed; the main photoelectricity is arranged below the positioning camera, the auxiliary photoelectricity is installed at a sprayer module of the printer head, and the main photoelectricity and the auxiliary photoelectricity are sequentially triggered when a coin to be subjected to spray printing moves to the printer head along the annular track.
3. The high-precision color spraying machine according to claim 2, characterized in that: the auxiliary photoelectricity is arranged below a spray head of the spray head module, the positioning camera and the printer head are both arranged above the annular track, and the main encoder, the positioning camera, the main photoelectricity and the auxiliary photoelectricity are all connected with a PC.
4. The high-precision color spraying machine according to claim 3, characterized in that: the printer head comprises a group of sprayer modules, one or two sprayers are arranged on each sprayer module, and an auxiliary photoelectric device is correspondingly arranged below each sprayer.
5. The high-precision color spraying machine according to claim 4, characterized in that: the conveying device comprises an annular track and a driving mechanism for driving the annular track to move, a group of sliding tables for bearing coins are arranged on the annular track, and the sliding tables can move along the annular track.
6. The high-precision color spraying machine according to claim 5, wherein: the automatic coin-feeding device is characterized in that a rotary gap feeding station, a visual positioning station, an ink-jet printing station, a color quality inspection station, a qualified product eliminating station and a defective product output station are sequentially arranged on the annular track along the conveying direction of the annular track, a gloss oil quality inspection station is arranged at the qualified product eliminating station, a coin feeding device is arranged at the rotary gap feeding station, the visual positioning station is provided with a positioning camera and a matched light source of a precision control system, the ink-jet printing station is provided with a printer head, the color quality inspection station is provided with a first inspection camera and a matched light source, the qualified product eliminating station and the defective product output station are respectively provided with a coin shifting mechanism, and the gloss oil quality inspection station is provided with a second inspection camera and a matched light source.
7. The printing method of the high-precision color spray machine based on any one of claims 1 to 6 is characterized by comprising the following steps:
placing the coins on a conveying device, wherein the conveying device drives the coins to move according to a preset movement track;
and a precision control system in the spray printing device acquires a motion error generated in the conveying process of the coin, adjusts the printing parameters of the coin according to the motion error, and the printer head performs spray printing operation on the coin according to the adjusted printing parameters.
8. The printing method of the high-precision color spray machine according to claim 7, wherein the precision control system obtains a motion error generated during the conveying process of the coins, and adjusts the printing parameters of the coins according to the motion error, and the specific method is as follows:
the method comprises the steps that firstly, coins are arranged on a sliding table and move along an annular track, the coins trigger a positioning camera through main photoelectricity to acquire coin images so as to obtain a relative position difference value between the coin images and a coin template, and meanwhile, the numerical value of a main encoder is recorded as position information of the coins in the X direction when the coins pass through the main photoelectricity; turning to the second step;
secondly, the coins continuously follow the annular track to move along with the sliding table, and when the coins enter the lower part of the nozzle module, the coins pass through an auxiliary photoelectric trigger main encoder of the nozzle module to record the numerical value of the coins as position information of the coins in the X direction when the coins pass through the auxiliary photoelectric trigger main encoder; turning to the third step;
and thirdly, determining printing parameters according to the relative position difference between the coin image and the coin template and the position information of the coin in the X direction when the coin passes through the main photoelectricity and the auxiliary photoelectricity, and spraying and printing patterns on the coin by a nozzle corresponding to the auxiliary photoelectricity on the nozzle module according to the printing parameters.
9. The printing method of the high-precision color spray machine according to claim 8, wherein in the first step, the main photo is triggered when the coin passes through the main photo, the main photo sends a trigger signal to the PC, then the PC controls the positioning camera to photograph and collect the image of the coin in motion, the PC compares the collected image of the coin in motion with the coin template stored in the PC to obtain the relative position difference between the coin in motion and the coin template prestored in the PC, and the relative position difference comprises the relative difference of the coin in the X, Y direction and the rotation angle difference of the coin, which are respectively marked as Δ X, Δ Y and Δ θ; when the coin passes through the main photoelectric sensor, the PC controls the main encoder to record the value of the coin as the position information of the coin in the X direction when the coin passes through the main photoelectric sensor, and the position information is recorded as X1; in the second step, triggering the auxiliary photoelectric device when the coin passes through the auxiliary photoelectric device, sending a trigger signal to the PC by the auxiliary photoelectric device, and then controlling the main encoder by the PC to record the value of the coin at the moment as the position information of the coin in the X direction when the coin passes through the auxiliary photoelectric device, and recording the position information as X2; in the third step, the movement distance of the coin from the main photoelectric sensor to the auxiliary photoelectric sensor in the X direction is recorded as S, the expected position information of the coin when passing through the auxiliary photoelectric sensor is S1, the actual position information is S2, the expected position and the actual position of the coin when passing through the auxiliary photoelectric sensor are calculated according to the following formula,
S1＝X1+S (1)
S2＝X2 (2)
then, the actual position of the coin passing through the auxiliary photoelectric sensor is compared with the expected position to obtain the difference Delta S between the actual position and the expected position, the difference between the actual position and the expected position is calculated according to the following formula,
ΔS＝S2-S1 (3)
finally, it is determined whether the value of Δ S is within the design range, and if Δ S is within the design range, the value X2 recorded by the main encoder is used as the printing start point in the X direction, and if Δ S is not within the design range, the expected position S1 is used as the printing start point in the X direction.
10. The printing method of the high-precision color spray machine according to claim 9, wherein in the first step, the specific method for obtaining the relative position difference between the coin in motion and the coin template prestored in the PC is as follows:
the center positions x, y of the coin in the inspection image are compared with the center positions x1, y1 of the coin in the template image to calculate X, Y shifts, i.e. deltax, deltay,
Δx＝x-x1
Δy＝y-y1
meanwhile, the image characteristic region converts two-dimensional data into one-dimensional data through polar coordinate conversion, and then carries out NCC template matching with the similarly processed one-dimensional template data to calculate the horizontal deviation of the image characteristic region, wherein the deviation value represents the angle deviation delta theta,
wherein Nrows and Ncoles respectively represent the row and column numbers of the detection image and the template image, and v1(k，l)、v2(k, l) respectively represent pixel values of the detection image and the template image at a point (k, l),
respectively representing the mean gray values, σ, of the inspection image and the template image2(v1)、σ2(v2) Respectively representing the variance of the pixel values of the detection image and the template image.
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