CN109501476B - Printing precision control method of digital can printing machine and digital can printing machine - Google Patents
Printing precision control method of digital can printing machine and digital can printing machine Download PDFInfo
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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
- B41J3/4073—Printing on three-dimensional objects not being in sheet or web form, e.g. spherical or cubic objects
- B41J3/40733—Printing on cylindrical or rotationally symmetrical objects, e. g. on bottles
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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
- B41J3/4073—Printing on three-dimensional objects not being in sheet or web form, e.g. spherical or cubic objects
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M5/00—Duplicating or marking methods; Sheet materials for use therein
- B41M5/0082—Digital printing on bodies of particular shapes
- B41M5/0088—Digital printing on bodies of particular shapes by ink-jet printing
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Abstract
A printing precision control method of a digital can printing machine and the digital can printing machine are characterized in that: when the characters or patterns of the tank body are digitally printed, the pixels needing to be printed in each decomposed digitized image layer are associated with the absolute angular displacement (or angular position) of each core rod on each printing station by utilizing an angular encoder arranged on the core rod, so that the accurate alignment between the printed digitized image layers is ensured; the method comprises the following steps: firstly, decomposing characters or patterns and defining an initial printing station; secondly, printing the layer of the initial printing station and establishing an accurate alignment relation; thirdly, mapping a specific alignment relation; and fourthly, finishing the rest printing. The core rod of the invention drives the tank body to print the corresponding pixel at the position where the tank body rotates in the circumferential direction, thereby ensuring the accuracy of the pixel position in each digital image layer on the tank body, further accurately aligning the printed digital image layers and realizing high-precision printing.
Description
Technical Field
The invention relates to a digital tin printing machine, in particular to a printing precision control method of the digital tin printing machine and the digital tin printing machine using the method.
Background
Digital printing jar equipment, or called jar body digital printer, is the digital printer that carries out the pattern decoration to the outer wall of the jar body.
In the prior art, the structure of a representative digital can printing device can be found in utility model patent with publication number CN 207257125U. The patent discloses a metal can digital printer, which comprises a rotary platform, a plurality of sets of mandrel components arranged on the rotary platform, a feeding driving mechanism for driving the rotary platform to rotate, and a self-rotation driving mechanism for driving a mandrel main shaft of the mandrel components to rotate; be equipped with a plurality of stations in rotary platform's periphery: the metal can feeding and discharging device comprises a can feeding station, a bottom color printing station, a bottom color pre-drying station, a plurality of color printing stations, a drying station, a can discharging station and the like, wherein a feeding driving mechanism is acted on a rotary platform and mainly comprises a feeding motor, namely the feeding motor drives the rotary platform to transfer the metal can among the stations in a 'moving-stopping-moving' intermittent motion mode; the rotation driving mechanism comprises a rotation motor, a rotation main shaft, a large bevel gear and a plurality of small bevel gears, each small bevel gear is installed in one-to-one correspondence with the mandrel main shaft of each mandrel component, and the rotation motor drives the mandrel main shaft of each mandrel component to rotate through the rotation main shaft, the large bevel gear and the small bevel gear. When the rotary platform works, the core rods and the tank body sleeved on the core rods are brought to different stations along with the intermittent rotation of the rotary platform in the moving-stopping-moving mode, and printing is carried out when the rotary platform stops under a spray head of a printing station. When the core rod is printed on each printing station, the rotating platform is in a static state, the core rod is driven by the rotation motor through the rotation main shaft, the large conical gear and the small conical gear to do uniform-speed circular motion, and the printing work of the outer wall of the tank is completed within one rotation.
The digital can printing machine adopts the specific printing mode that: the method comprises the steps of firstly decomposing information of characters or patterns to be printed into digital image layers which correspond to printing nozzles on all printing stations and need to be printed according to colors, when a core rod revolves to reach an initial printing station, the printing nozzles of the initial printing station print the corresponding digital image layers, then the core rod revolves, the core rod reaches a next printing station, the printing nozzles of the printing stations also print one digital image layer, then the core rod revolves again to sequentially complete the printing of the digital image layers of all the printing stations, and the final printing patterns are formed by covering and overprinting one layer of image layer and one layer of image layer.
If the rotation of the core rod is stable at a constant speed, the control mode of the printing spray heads of each printing station in the prior art is controlled according to time. However, in practice, due to various errors (such as gear machining errors, mechanical installation errors and motor control errors), the rotation of the core rod is not constant and stable, and pixel points in layers printed on a printing station are shifted, so that the pixel points between the layers are deviated, the problems of ghosting, blurring and the like of patterns occur, the printing precision is influenced, and the influence is more obvious particularly when the core rod runs at a high speed. For digital printing, the requirement on printing position precision is high, and when the printing is carried out with the resolution of 600dpi, the size of each pixel is about 40 μm; when printed at a resolution of 1200dpi, each pixel has a size of only 20 μm.
Therefore, how to make the printing precision not affected by the fluctuation of the movement speed of the core rod as much as possible is a difficult problem to be solved by the technical personnel in the field.
Disclosure of Invention
The invention aims to provide a printing precision control method of a digital can printing machine and the digital can printing machine, so that the printing precision is not influenced by the fluctuation of the movement speed of a core rod as much as possible.
In order to achieve the purpose, the first method adopted by the invention has the technical scheme that:
a digital printing machine printing precision control method, for the digital printing machine designed with the following structure and motion relation, when printing the characters or patterns of the tank body digitally, the angle encoder installed on the core rod is used to associate the pixels to be printed in each decomposed digital image layer with the absolute angular displacement or angular position of each core rod on each printing station, thereby ensuring the accurate alignment between each digital image layer to be printed;
the digital can printing machine is provided with a rotary platform capable of generating intermittent revolution, the rotary platform is provided with core rods for sleeving the can bodies at intervals along the circumferential direction, and each core rod intermittently revolves along with the rotary platform and simultaneously rotates around the axis of the core rod; a plurality of printing stations are arranged outside the rotary platform corresponding to the revolution stop position of the mandrel, and each printing station is provided with a printing nozzle;
the printing precision control method comprises the following steps:
first, decomposing characters or patterns and defining initial printing station
(1) Decomposing characters or patterns
Decomposing the information of the characters or patterns to be printed into digital image layers which are corresponding to the printing nozzles on each printing station and need to be printed according to colors;
(2) defining an initial print station
Selecting one printing station from the printing stations as a starting printing station, and defining the printing sequence of the rest printing stations;
secondly, printing the layer of the initial printing station and establishing an accurate contraposition relation
Printing a corresponding digital image layer at an initial printing station, simultaneously establishing a corresponding relation between pixels of the digital image layer of the station and absolute angular displacement or angular position of a current core rod by utilizing angular position information output by a current core rod angular encoder, and taking the corresponding relation as a specific alignment relation between the digital image layers of the current core rod in the printing process of the round;
thirdly, mapping specific alignment relation
Mapping the specific alignment relation of the current core rod obtained in the second step to the next rest printing stations along with the core rod, and establishing the corresponding relation between the pixels of the digital layers of the rest printing stations and the absolute angular displacement or angular position of the core rod;
the fourth step, finish other prints
And finishing the printing of the digitalized image layers of the rest printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
In the above scheme, the second step specifically is: firstly, according to the specified printing speed and resolution information, calculating the frequency of the firing pulse of the printing nozzle based on time of the printing nozzle of the initial printing station or the interval of the firing pulse of the printing nozzle based on the absolute angular displacement or angular position of the mandril; then, according to the digitalized image layer which is decomposed in the first step and corresponds to the printing nozzle on the initial printing station, the calculated frequency or angle interval of the ignition pulse of the printing nozzle on the initial printing station, and the data which represents the absolute angular displacement or angular position of the mandrel and is recorded by the mandrel angle encoder on the current initial printing station, the ignition pulse of the printing nozzle is determined, and the printing of the initial printing station is completed; and recording the corresponding relation between the position of each ignition pulse on the digital layer and the absolute angular displacement or angular position of the current mandril at the same time of finishing printing at the initial printing station, and taking the corresponding relation as the specific alignment relation.
In the above scheme, the adopted hardware system comprises the angle encoder, the main computer, the spray head main control system, the data processing unit and a sensor; the angle encoders are correspondingly arranged on the core rods; the spray head master control system is connected with the printing spray heads of all stations; the data processing unit receives the angle position information output by each angle encoder and is connected with the input and output of the spray head main control system; the sensor is arranged on the digital can printing machine and used for sensing the revolution stop of the mandril, generating information representing the revolution stop and transmitting the information to the data processing unit;
in the first step, the software in the main computer decomposes the information of the characters or patterns to be printed into the digital image layers which are required to be printed by the printing nozzles on the corresponding printing stations according to the colors; the second step is to establish and record specific alignment relation by the data processing unit; the third step is to map specific bit relationships with the data processing unit.
In order to achieve the purpose, the second method adopted by the invention has the technical scheme that:
a digital printing machine printing precision control method, for the digital printing machine designed with the following structure and motion relation, when printing the characters or patterns of the tank body digitally, the angle encoder installed on the core rod is used to associate the pixels to be printed in each decomposed digital image layer with the absolute angular displacement (or angular position) of each core rod on each printing station, thereby ensuring the accurate alignment between each digital image layer;
the digital can printing machine is provided with a rotary platform capable of generating intermittent revolution, the rotary platform is provided with core rods for sleeving the can bodies at intervals along the circumferential direction, and each core rod intermittently revolves along with the rotary platform and simultaneously rotates around the axis of the core rod; a plurality of printing stations are arranged outside the rotary platform corresponding to the revolution stop position of the mandrel, and each printing station is provided with a printing nozzle;
the printing precision control method comprises the following steps:
first, decomposing characters or patterns
Decomposing the information of the characters or patterns to be printed into digital image layers which are corresponding to the printing nozzles on each printing station and need to be printed according to colors;
second, defining the alignment relation of a digital image layer
Before printing, an angle encoder is used for defining the contraposition relation of a corresponding core rod on any printing station, the corresponding relation between the pixel of a digital image layer of the station and the absolute angular displacement or angular position of the corresponding core rod is established, and the corresponding relation is used as the specific contraposition relation between the digital image layers of the corresponding core rod in the printing process of the round;
thirdly, mapping specific alignment relation
Mapping the specific alignment relation obtained in the second step to all printing stations along with the mandril, and establishing a corresponding relation between the pixels of the digital layer of each printing station and the absolute angular displacement or angular position of the mandril;
fourthly, finishing printing of each printing station
And finishing the printing of the digitalized image layers of all the printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
In the above scheme, the adopted hardware system comprises the angle encoder, the spray head main control system, the data processing unit and a sensor; the angle encoders are correspondingly arranged on the core rods; the spray head master control system is connected with the printing spray heads of all stations; the data processing unit receives the angle position information output by each angle encoder and is connected with the input and output of the spray head main control system; the sensor is arranged on the digital can printing machine and used for sensing the revolution stop of the mandril, generating information representing the revolution stop and transmitting the information to the data processing unit;
in the first step, the software in the main computer decomposes the information of the characters or patterns to be printed into the digital image layers which are required to be printed by the printing nozzles on the corresponding printing stations according to the colors; the second step is performed by the data processing unit; said third step is also performed by means of said data processing unit.
In order to achieve the purpose, the technical scheme of the digital tin printing machine adopted by the invention is as follows:
a digital can printing machine adopts the first or second control method.
The principle of the invention is as follows: the invention is based on the problem existing in the prior art, and breakthroughs the use of angle encoders installed on the core rods to directly relate the position of each pixel of the digital image layer to the current absolute angular displacement or angular position of the core rod, in other words, the core rod drives the tank body to rotate to a certain position in the circumferential direction of the core rod, and then the point corresponding to the position in the character or pattern is printed, thereby ensuring the accuracy of the pixel position in each digital image layer on the tank body, further accurately aligning the digital image layers printed on the walls of each tank, greatly reducing the influence of the fluctuation of the motion speed on the printing accuracy, and realizing high-accuracy printing.
The invention has the following effects:
1. the running speed of the equipment is improved; (1) the printing can be started from any position of the tank body, namely the original constant speed mode can be only used for printing from the position where the pattern starts; (2) the printing can be carried out when the equipment has larger speed fluctuation just reaching the stop angle, namely the printing precision is influenced when the original fluctuation is larger;
2. the equipment cost is reduced: the maintenance time of the gear is reduced, the maintenance frequency is reduced, the manufacturing precision requirement of transmission parts such as the gear is reduced, and the mounting precision requirement of the transmission parts such as the gear is reduced;
3. the equipment is more flexible to use; the equipment can print at different speeds or at variable speeds, software parameters do not need to be adjusted again (the printed data is only relevant to the angle of a mandril and is not relevant to the speed of the equipment) -the software parameters need to be adjusted according to the speed in the original constant speed mode, and the printing can not be realized in the speed change process.
Drawings
Fig. 1 is a schematic layout of each mandrel of a digital can printing machine according to a first embodiment and a second embodiment of the present invention;
FIG. 2 is a schematic step diagram of a printing accuracy control method according to a first embodiment of the present invention;
fig. 3 is a schematic block diagram of a printing accuracy control system according to the first and second embodiments of the present invention;
FIG. 4 is a schematic diagram illustrating a principle of mapping specific alignment relationships according to a first embodiment and a second embodiment of the present invention;
fig. 5 is a schematic step diagram of a printing accuracy control method according to a second embodiment of the present invention.
In fig. 4 above: 1. a tank body; 2. the outer wall of the tank is expanded along the circumferential direction; 21. the output pulses of the angle encoder are distributed at the corresponding positions of the expanded surface of the tank wall; 3. printing a digital image layer corresponding to the spray head by the initial printing station; 31. pixel points; 4. the other digital image layers corresponding to the printing nozzles are printed; 41. and (6) pixel points.
Detailed Description
The invention is further described with reference to the following figures and examples:
the first embodiment is as follows: referring to FIGS. 1-4:
the embodiment relates to a printing precision control method of a digital can printing machine.
The printing precision control method of the digital tank printing machine aims at the digital tank printing machine with the following structure and motion relation, when tank characters or patterns are digitally printed, an angle encoder arranged on a core rod is utilized to correlate pixels needing to be printed in each decomposed digital image layer with absolute angular displacement (or angular position) of each core rod on each printing station, and therefore accurate alignment between each digital image layer to be printed is guaranteed.
Referring to fig. 1, the digital can printing machine has a rotary platform capable of generating intermittent revolution, the rotary platform is provided with core rods for sleeving the can bodies at intervals along the circumferential direction, and each core rod intermittently revolves along with the rotary platform and simultaneously rotates around the axis of the core rod; and a plurality of printing stations are arranged outside the rotary platform corresponding to the revolution stop position of the mandrel, and each printing station is provided with a printing nozzle.
Referring to fig. 2, the printing accuracy control method includes the steps of:
first step S1, decomposing text or pattern and defining initial printing position
(1) Decomposing characters or patterns
Decomposing the information of the characters or patterns to be printed into digital image layers which are corresponding to the printing nozzles on each printing station and need to be printed according to colors;
(2) defining an initial print station
Selecting one printing station from the printing stations as a starting printing station, and defining the printing sequence of the rest printing stations;
second step S2, print the initial print station and establish the precise alignment
Printing a corresponding digital image layer at an initial printing station, establishing a corresponding relation between pixels of the digital image layer of the station and the absolute angular displacement of a current core rod by using data recorded by a current core rod angle encoder, and taking the corresponding relation as a specific alignment relation between the digital image layers of the current core rod in the printing process of the round;
third step S3, mapping specific alignment relation
Mapping the specific alignment relation of the current mandril obtained in the second step to the next rest printing stations along with the mandril, and establishing the corresponding relation between the pixels of the digital layers of the rest printing stations and the absolute angular displacement (or angular position) of the mandril;
the fourth step S4 is to finish the rest of printing
And finishing the printing of the digitalized image layers of the rest printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
The printing precision control method of the embodiment specifically comprises the following steps:
the adopted hardware system comprises the angle encoder, a main computer, a spray head main control system, a data processing unit and a sensor.
As shown in fig. 3, the specific hardware system is exemplified by:
the sensor is a position sensor. The data processing unit can be a Digital Signal Processor (DSP), a singlechip, other microprocessors and the like, can also be a programmable logic chip such as an FPGA, a CPLD and the like, and can also be a computer. The following data processing unit takes a digital signal processor (DSP chip) as an example.
The angle encoder is correspondingly arranged on each core rod, the output information of each angle encoder is transmitted to a digital signal processor (DSP chip) through an electric slip ring, the angle encoder can also be called as a rotary encoder, and the rotary encoder can generally output two information: angular displacement pulse information and index information (one pulse output per revolution).
The output of the spray head control unit is correspondingly connected with the printing spray heads on the printing stations one by one, and the input of the spray head control unit is connected with a spray head main control system and a digital signal processor (DSP chip); the spray head main control system is in communication connection with the main computer and is also in communication connection with a digital signal processor (DSP chip).
The position sensor is correspondingly arranged on a certain station, the detection end of the position sensor faces the core rod and is used for sensing whether the revolution of the core rod stops or not, generating information representing the stop of the revolution and transmitting the information to the digital signal processor (DSP chip); this is an example, and in practice, information indicating that the revolution is stopped may be directly obtained from a servo motor system that drives the mandrel bar.
For the above specific hardware example, the steps of the method of this embodiment are described in detail as follows:
first step S1, decomposing text or pattern and defining initial printing position
(1) Decomposing characters or patterns
The user inputs or produces the picture to be printed by the host computer, namely the computer obtains the character or pattern information of the picture to be printed, and the computer decomposes the character or pattern information to be printed into the digital picture layer which is required to be printed by the printing nozzle on each printing station according to the color.
(2) Defining an initial print station
Presetting or selecting one printing station from printing stations by an operator before printing as a starting printing station, and defining the printing sequence of the rest printing stations; that is, which is the print station No. 1 and which is the print station No. 2 … … are set. This order is not necessarily provided in order in the circumferential direction of the rotary table of the can printing machine, and may be set arbitrarily.
Second step S2, print the initial print station and establish the precise alignment
Printing a corresponding digital image layer at an initial printing station, wherein the specific operation is as follows: firstly, calculating the frequency of the firing pulses of the printing nozzle based on time of the printing nozzle of the initial printing station or the interval of the firing pulses of the printing nozzle based on the absolute angular displacement (or angular position) of the mandrel by a nozzle main control system or a host computer according to the specified printing speed and resolution information; then, a digital signal processor (DSP chip) determines each ignition pulse of the printing nozzle according to the calculated frequency of the ignition pulse of the printing nozzle of the initial printing station or the calculated interval of the ignition pulse and the data representing the absolute angular displacement of the core rod output by the core rod angle encoder on the current initial printing station, and transmits the data to a nozzle control unit, so as to instruct the printing nozzle of the initial printing station to print and complete the printing of the digitized image layer of the initial printing station.
When the initial printing station prints the corresponding digital image layer, a digital signal processor (DSP chip) utilizes the data recorded by the current core rod angle encoder to establish and record the corresponding relation between the pixels of the digital image layer of the station and the absolute angular displacement (or angular position) of the current core rod, and the corresponding relation is used for printing and positioning each digital image layer of the current core rod in the round of printing process.
The above-described manner of establishing correspondence is shown in fig. 4, and the digitized image layer 3 of the initial print station can be regarded as an expanded view of the circumferential surface of the can body. On the one hand, the development can be measured in the circumferential direction by the output pulses generated when the mandrel coaxial angle encoder rotates, and each pulse represents different angular positions of the mandrel and the tank body on the mandrel; on the other hand, since the digitized picture can be considered to be composed of a uniformly distributed pixel lattice (each pixel has a different gray level, the lowest gray level is 0, i.e. no color), the above-mentioned expansion map can also be measured by the basic pixels of the picture in the circumferential direction. Two coordinate systems are established in the circumferential direction, which are referred to as an "angle pulse coordinate system" and a "picture pixel coordinate system", respectively, and it is obvious that the two coordinate systems are measured or described in different units in the same picture, so that they have a fixed linear correspondence. Each pixel on the layer corresponds to an angular position defined by the angular pulse in the angular pulse coordinate system. If a pixel is located between two angle pulses, the data processing unit estimates the distance of the pixel from the previous angle pulse, i.e. the fractional part of the angular position of the pixel in the "angle pulse coordinate system", and the position of the "previous pulse" is the integer part of the angular position of the pixel, the integer part and the fractional part together constituting the coordinate value of the pixel in the "angle pulse coordinate system". When the core rod (driving the tank) rotates and reaches the angle pulse coordinate corresponding to a certain pixel, the data processing unit generates an ignition pulse to control the corresponding nozzle to spray ink drops, and the corresponding pixel is generated on the tank. The angle pulse coordinate value corresponding to the first pixel of the picture (or the image layer) is defined as the initial position of the picture (each image layer). Thus, each pixel position in each image layer of the picture along the circumferential direction has a corresponding coordinate value in the "angle pulse coordinate system". A correspondence between the pixels and the absolute angular position of the mandrel is thus established.
Third step S3, mapping specific alignment relation
And mapping the specific alignment relation of the current mandril obtained in the second step to the next rest printing stations by a digital signal processor (DSP chip) along with the mandril, and establishing the corresponding relation between the pixels of the digitalized layer of the rest printing stations and the absolute angular displacement (or angular position) of the mandril.
The third step is explained specifically as follows: as shown in fig. 4, the digitized image layer of each print station is an expanded view around the circumferential surface of the can body, the digitized image layer of each print station is decomposed from the same picture, and there is an inherent corresponding relationship between the image layers, so that the corresponding relationship between the pixels of the digitized image layers 4 of the remaining print stations and the absolute angular displacement (or angular position) of the core rod is established by projecting (or moving) the coordinates of the digitized image layer 3 of the initial print station established in the second step onto the digitized image layers 4 of the remaining print stations.
The specific operation can be as follows: and mapping according to the angle position in the 'angle pulse coordinate system' of the mandril corresponding to each pixel printed by the printing nozzle of the initial printing station recorded in the second step, so as to obtain the angle position in the 'angle pulse coordinate system' of the mandril corresponding to the pixel to be printed by the printing nozzles of the rest printing stations.
The fourth step S4 is to finish the rest of printing
And finishing the printing of the digitalized image layers of the rest printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
The specific operation is as follows: and determining the ignition pulse of the printing nozzle according to the angle positions in the angle pulse coordinate system of the mandrils corresponding to the pixels to be printed by the printing nozzles of the rest printing stations obtained in the third step and by combining the data of the absolute angular displacement of the current mandrils, and transmitting the ignition pulse to the nozzle control unit, so that the printing nozzles are instructed to print, and the printing of the digital image layers of all the subsequent printing stations is completed one by one in the same way.
The embodiment relates to a digital tin printing machine, which adopts the printing precision control method of the digital tin printing machine.
In the embodiment, starting from the root of the problems in the prior art, the angular encoders installed on the core rods are utilized in a breakthrough manner to directly associate the position of each pixel of the digitized image layer with the absolute angular displacement (or angular position) of the core rod, in other words, the core rod is rotated to a certain angular position in the circumferential direction with the tank body, so that a point corresponding to the angular position in a pattern or text is printed, the accuracy of the pixel position in each digitized image layer on the tank body is ensured, further, accurate alignment can be performed between the digitized image layers, the influence of the movement speed fluctuation on the printing accuracy is greatly reduced, and high-accuracy printing is realized.
Example two: referring to fig. 1, 3, 4 and 5:
the embodiment relates to a printing precision control method of a digital can printing machine.
The printing precision control method of the digital tank printing machine aims at the digital tank printing machine with the following structure and motion relation, when characters or patterns of a tank body are digitally printed, an angle encoder arranged on a core rod is utilized to associate pixels needing to be printed in each decomposed digital image layer with absolute angular displacement (or angular position) of each core rod on each printing station, so that accurate alignment between each digital image layer to be printed is ensured;
the digital can printing machine is provided with a rotary platform capable of generating intermittent revolution, the rotary platform is provided with core rods for sleeving the can bodies at intervals along the circumferential direction, and each core rod intermittently revolves along with the rotary platform and simultaneously rotates around the axis of the core rod; a plurality of printing stations are arranged outside the rotary platform corresponding to the revolution stop position of the mandrel, and each printing station is provided with a printing nozzle;
as shown in fig. 5, the printing accuracy control method includes the steps of:
first step S5, decomposing characters or patterns
Decomposing the information of the characters or patterns to be printed into digital image layers which are corresponding to the printing nozzles on each printing station and need to be printed according to colors;
the second step S6 is to define the alignment relationship of a digitized layer
Before printing, an angle encoder is used for defining the contraposition relation of a corresponding core rod on any printing station, the corresponding relation between the pixel of a digital image layer of the station and the absolute angular displacement (or angular position) of the corresponding core rod is established, and the corresponding relation is used as the specific contraposition relation between the digital image layers of the corresponding core rod in the printing process of the round;
third step S7, mapping specific alignment relation
Mapping the specific alignment relation obtained in the second step to the next printing stations along with the mandril, and establishing the corresponding relation between the pixels of the digital layer of each printing station and the absolute angular displacement (or angular position) of the mandril;
the fourth step S8 is to complete the printing of each print station
And finishing the printing of the digitalized image layers of all the printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
The second embodiment relates to a digital can printing machine, which adopts the printing precision control method of the digital can printing machine.
The difference between the second embodiment and the first embodiment is mainly as follows: instead of establishing a specific alignment relationship while printing at the initial print station, the specific alignment relationship is established in advance before printing (only the initial position of the picture is determined at the initial print station), and then the specific alignment relationship is mapped to all print stations.
The second embodiment can obtain effects similar to those of the first embodiment.
In the above embodiment, the hardware part of the control system (i.e. fig. 3) is an example of the preferred embodiment, and it is also possible to actually implement the hardware in other prior art, for example, the DSP chip of the digital signal processor can be replaced by other microprocessor, or the functions performed by the processor can be integrated into the host computer.
In the above embodiments, how to control printing by the nozzle control unit and the nozzle main control system is specifically described in the foregoing embodiments, which is the prior art and disclosed in the prior document, and need not be described herein again.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (7)
1. A printing precision control method of a digital can printing machine is characterized in that: aiming at a digital tank printing machine designed with the following structure and motion relation, when characters or patterns of a tank body are digitally printed, an angle encoder arranged on a core rod is utilized to associate pixels needing to be printed in each decomposed digital image layer with absolute angular displacement or angular position of each core rod on each printing station, so that accurate alignment between each printed digital image layer is ensured;
the digital can printing machine is provided with a rotary platform capable of generating intermittent revolution, the rotary platform is provided with core rods for sleeving the can bodies at intervals along the circumferential direction, and each core rod intermittently revolves along with the rotary platform and simultaneously rotates around the axis of the core rod; a plurality of printing stations are arranged outside the rotary platform corresponding to the revolution stop position of the mandrel, and each printing station is provided with a printing nozzle;
the printing precision control method comprises the following steps:
first, decomposing characters or patterns and defining initial printing station
(1) Decomposing characters or patterns
Decomposing the information of the characters or patterns to be printed into digital image layers which are corresponding to the printing nozzles on each printing station and need to be printed according to colors;
(2) defining an initial print station
Selecting one printing station from the printing stations as a starting printing station, and defining the printing sequence of the rest printing stations;
secondly, printing the layer of the initial printing station and establishing an accurate contraposition relation
Printing a corresponding digital image layer at an initial printing station, simultaneously establishing a corresponding relation between pixels of the digital image layer of the station and absolute angular displacement or angular position of a current core rod by utilizing angular position information output by a current core rod angular encoder, and taking the corresponding relation as a specific alignment relation between the digital image layers of the current core rod in the printing process of the round;
thirdly, mapping specific alignment relation
Mapping the specific alignment relation of the current core rod obtained in the second step to the next rest printing stations along with the core rod, and establishing the corresponding relation between the pixels of the digital layers of the rest printing stations and the absolute angular displacement or angular position of the core rod;
the fourth step, finish other prints
And finishing the printing of the digitalized image layers of the rest printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
2. The printing precision control method of the digital can printing machine according to claim 1, characterized in that: the second step is specifically: firstly, according to the specified printing speed and resolution information, calculating the frequency of the printing nozzle ignition pulse based on time of the printing nozzle at the initial printing station, or the interval of the printing nozzle ignition pulse based on the absolute angular displacement or angular position of the mandril; then, according to the digitalized image layer which is decomposed in the first step and corresponds to the printing nozzle on the initial printing station, the calculated frequency or angle interval of the ignition pulse of the printing nozzle on the initial printing station, and the data which represents the absolute angular displacement or angular position of the mandrel and is recorded by the mandrel angle encoder on the current initial printing station, the ignition pulse of the printing nozzle is determined, and the printing of the initial printing station is completed; and recording the corresponding relation between the position of each ignition pulse on the digital layer and the absolute angular displacement or angular position of the current mandril at the same time of finishing printing at the initial printing station, and taking the corresponding relation as the specific alignment relation.
3. The printing precision control method of the digital can printing machine according to claim 1, characterized in that: the adopted hardware system comprises the angle encoder, a main computer, a spray head main control system, a data processing unit and a sensor; the angle encoders are correspondingly arranged on the core rods; the main computer is connected with a spray head main control system, and the spray head main control system is connected with the printing spray heads of all stations; the data processing unit receives the angle position information output by each angle encoder and is connected with the input and output of the spray head main control system; the sensor is arranged on the digital can printing machine and used for sensing the revolution stop of the mandril, generating information representing the revolution stop and transmitting the information to the data processing unit;
in the first step, the software in the main computer decomposes the information of the characters or patterns to be printed into the digital image layers which are required to be printed by the printing nozzles on the corresponding printing stations according to the colors; the second step is to establish and record specific alignment relation by the data processing unit; the third step is to map specific bit relationships with the data processing unit.
4. A digital can printing machine is characterized in that: the digital can printing machine adopts the control method of claim 1.
5. A printing precision control method of a digital can printing machine is characterized in that: aiming at a digital tank printing machine designed with the following structure and motion relation, when characters or patterns of a tank body are digitally printed, an angle encoder arranged on a core rod is utilized to associate pixels needing to be printed in each decomposed digital image layer with absolute angular displacement or angular position of each core rod on each printing station, so that accurate alignment between each printed digital image layer is ensured;
the digital can printing machine is provided with a rotary platform capable of generating intermittent revolution, the rotary platform is provided with core rods for sleeving the can bodies at intervals along the circumferential direction, and each core rod intermittently revolves along with the rotary platform and simultaneously rotates around the axis of the core rod; a plurality of printing stations are arranged outside the rotary platform corresponding to the revolution stop position of the mandrel, and each printing station is provided with a printing nozzle;
the printing precision control method comprises the following steps:
first, decomposing characters or patterns
Decomposing the information of the characters or patterns to be printed into digital image layers which are corresponding to the printing nozzles on each printing station and need to be printed according to colors;
second, defining the alignment relation of a digital image layer
Before printing, an angle encoder is used for defining the contraposition relation of a corresponding core rod on any printing station, the corresponding relation between the pixel of a digital image layer of the station and the absolute angular displacement or angular position of the corresponding core rod is established, and the corresponding relation is used as the specific contraposition relation between the digital image layers of the corresponding core rod in the printing process of the round;
thirdly, mapping specific alignment relation
Mapping the specific alignment relation obtained in the second step to all printing stations along with the mandril, and establishing a corresponding relation between the pixels of the digital layer of each printing station and the absolute angular displacement or angular position of the mandril;
fourthly, finishing printing of each printing station
And finishing the printing of the digitalized image layers of all the printing stations according to the corresponding relation established in the third step, and circularly and repeatedly realizing the accurate printing of characters or patterns of each tank body.
6. The printing precision control method of the digital can printing machine according to claim 5, characterized in that: the adopted hardware system comprises the angle encoder, a main computer, a spray head main control system, a data processing unit and a sensor; the angle encoders are correspondingly arranged on the core rods; the spray head master control system is connected with the printing spray heads of all stations; the data processing unit receives the angle position information output by each angle encoder and is connected with the input and output of the spray head main control system; the sensor is arranged on the digital can printing machine and used for sensing the revolution stop of the mandril, generating information representing the revolution stop and transmitting the information to the data processing unit;
in the first step, the software in the main computer decomposes the information of the characters or patterns to be printed into the digital image layers which are required to be printed by the printing nozzles on the corresponding printing stations according to the colors; the second step is performed by the data processing unit; said third step is also performed by means of said data processing unit.
7. A digital can printing machine is characterized in that: the digital can printing machine adopts the control method of claim 5.
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| DE102014110520A1 (en) * | 2014-07-25 | 2016-01-28 | Krones Ag | Direct printing machine with ink supply system |
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