JPS61213154A - Method and apparatus for printing inner surface of pipe - Google Patents

Abstract

PURPOSE:To automatically print the inner surface of a pipe by a method in which the position and dimensions of a pipe are calculated on the basis of pipe detection signals obtained by a sensor to be moved by a multi-joint robot, and a printing head is moved along the inner surface of the pipe and printing is carried out. CONSTITUTION:Action indicating signals to select given programs on inside diameters calculated by an arithmetic unit for the position and dimensions of a pipe are put in a controller 11 for a robot 10, in which action contents according to the inside diameter of the pipe are input as programs. The action indicating signals include, besides selection signals, information on the end face 52 and central position of the pipe 50 in relation to the spatial coordinate axis of tips of joins 12 of the robot 10. The controller 11, therefore, moves a printing head inside the pipe for printing on the basis of the action indicating signals. Upon printing actions of the printing head 30, jet timing is controlled by the controller 31 for printing.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a tube inner surface printing method and apparatus, and more particularly to a tube inner surface printing method and apparatus suitable for printing characters, symbols, etc. on the inner surface of each stacked tube such as a steel pipe or a plastic pipe.

[Conventional technology]

Characters, symbols, etc. are printed on various types of pipes to clearly indicate product classification, type, dimensions, usage, etc. For example, for printing on the outer surface of the tube, JP-A-58-
163465 etc., characters engraved on a stencil by spraying paint on the stencil,
There is a stencil method for marking figures etc. on a pipe as a member to be marked, and a stamp method.
Various printing devices, such as those using a dot matrix method, have been proposed and put into practical use.

[Problems to be solved by the invention]

However, if letters or the like are printed on the outer surface of the tube, if a large number of tubes are stacked, the letters printed on the outer surface of the tube will be hidden and cannot be read. In addition, there are problems in that the characters printed on the outside surface of the tube may rub off during transportation or storage, making them difficult to read (or in extreme cases, disappearing). In response to these requests, the current practice is to print manually using stencils, stamps, etc. only on relatively large diameter pipes. There was no suitable method for automatically inserting the print head into the tube and moving it along the tube wall while maintaining a predetermined distance from the tube wall, and the print head was not inserted into the tube with a relatively small diameter. This is due to the fact that it was not as compact as possible.Furthermore, in order to automatically print on the inner surface of a tube, it is necessary to accurately grasp the position of the end surface of the tube and the dimensions of the tube. Moreover, since the printing area is extremely limited on the inner surface of the tube, the insertion and movement of the print head must be performed with high precision.Therefore, it is necessary to automate the printing on the inner surface of the tube. had the problem of being difficult.

[Purpose of the invention] The present invention has been made in order to solve the above-mentioned problems of the conventional art, and is applicable when there are variations in the position of the end of the tube that is the printing material, fluctuations in the central axis position of the tube, changes in the dimensions of the tube, etc. Another object of the present invention is to provide a tube inner surface printing method and apparatus that can automatically print on the inner surface of a tube. [Means to solve the problem]

As summarized in FIG. 1, the present invention is a method for printing on the inner surface of a tube. The articulated robot moves, the tube detection sensor obtains a tube detection signal, the position where the cough tube detection signal is obtained is obtained as a coordinate signal in three-dimensional space, and these tube detection signals and spatial coordinate signals are used to detect the tube. The position and dimensions of the tube are calculated, and based on the calculation results, a print head provided near the tube detection sensor is moved along the inner surface of the tube by a robot, and the print head is operated to print. In this way, the above objective has been achieved. Further, in a practical aspect of the present invention, the movement of the pipe detection sensor by the articulated robot on a plane perpendicular to the center line of the pipe and close to the end face of the pipe is performed by moving the movement locus of the sensor on a plane that intersects two lines. By using a folded line composed of straight lines, the above object is achieved by eliminating waste in movement for detecting the position and dimensions of the tube, and by making it possible to detect the position and dimensions of the bud in a short time. . Further, an embodiment of the present invention includes the print head. By making the movement along the inner surface of the tube during printing a constant speed motion, the printing timing control of the print head can be simplified and easily performed, thereby achieving the above object. Further, the present invention provides a tube inner surface printing device having a plurality of joints,
A multi-joint robot that can move the tip of the joint to any position in three-dimensional space; a tube detection sensor that detects the end surface of the tube to be printed, which is attached to the tip of the joint of the multi-joint robot; A tube detection sensor movement control means for moving the tube detection sensor on a plane perpendicular to the center line of the tube and close to the end surface of the tube, a detection signal of the tube detection sensor, and a joint to which the tube detection sensor is attached. pipe position/dimension calculation means for calculating the end face position of the pipe, the center line position of the pipe, and the inner diameter of the pipe based on the obtained three-dimensional spatial coordinate signal of the detection signal; and the pipe detection sensor is installed. A print head is attached to the joint that is attached to the tube and prints on the inner surface of the tube, and the distance between the print head and the inner surface of the tube is maintained constant inside the tube based on signals from the tube position/dimension calculation means. and a print control means for moving the print head along the inner surface and controlling the print head, thereby achieving the same object.

[Effect]

In the present invention, when printing on the inner surface of a tube, a tube detection sensor is moved by an articulated robot on a plane perpendicular to the center line of the tube and close to the end surface of the tube, and the tube detection signal is detected by the tube detection sensor. At the same time, the position where the tube detection signal is obtained is obtained as a coordinate signal in a three-dimensional space, and the position and dimensions of the tube are calculated based on the tube detection signal and the spatial coordinate signal,
Based on the calculation results, a robot moves a print head provided near the tube detection sensor along the inner surface of the tube, and operates the print head to print. Therefore, the position and dimensions of the tube can be accurately grasped, and based on the position and dimensions of the tube, the print head can be moved a large distance into the tube with high accuracy. As a result, even if there are variations in the position of the end face of the tube, fluctuations in the center line position of the tube, changes in the inner diameter and wall thickness of the tube, etc., it is possible to automatically print on the inner surface of the tube.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a tube inner surface printing device to which the present invention is applied will be described in detail with reference to the drawings. In this example, the 21i! ! As shown in Figure 1 and Figure 3, an articulated robot 1 widely known as an industrial robot
0, a distance sensor 20 as a tube detection sensor attached to the tip of the joint 1i12 of the articulated robot 1o, and a print head 3o, and these articulated robots 10. It is composed of a distance sensor 20 and a control device 40 that controls the print head 30. The distance sensor 20 is configured such that the projected laser beam is connected to the joint 12.
The printing head 30 is attached to the tip of the joint 12 of the multi-joint robot 10 so as to be parallel to the axis of the tube 50, and the printing head 30 is attached so that the tip of the marking nozzle faces the inner surface 58 of the tube 50 when inserted into the tube 50. It is located at the rear of the distance sensor 2o and attached to the gap Wi12 so that the axis of the marking nozzle is perpendicular to the axis of the joint 12. The articulated robot 10 has a plurality of joints, and is configured such that the tip of the joint 12 can be moved to any position in three-dimensional space. The articulated robot 10 is not particularly limited, but for example, an industrial robot manufactured by FANUC, 1? '/trFANUc ROBOT 5-MoDEL 1
J etc. can be used. The distance sensor 20 serving as the tube detection sensor is constituted by a laser rangefinder that measures the distance to the object based on the principle of triangulation using laser light. This distance sensor 2o, as shown in FIG.
a lens 24 for projecting the light generated by the light onto the end face 52 of the tube 50; a photodetecting element 26 for detecting the reflected light scattered on the surface of the end face 52; and an imaging lens 28 that forms an image. The photodetecting element 26 obtains as an electrical output the position on the light receiving surface at which the reflected light is incident, and outputs an electrical output from the end surface 5.
The electrical output of the photodetecting element 26 changes depending on the position of the photodetecting element 26. Therefore, the distance between the distance sensor 20 and the end surface 52 of the tube 50 can be measured by analyzing the electrical output signal of the photodetecting element 26 with the signal converting means 21. As the distance sensor 20, a laser distance meter manufactured by Anki Denki Co., Ltd. or 5ELCO-1 Co., Ltd. can be used. The print head 30 uses a known dot matrix print head. That is, for example, Utility Model Application No. 58-12865
As proposed in 8 etc., electricity selectively sprays dots of paint or ink using a solenoid! ) A dot matrix print head combining a plurality of marking nozzles (11) is used. The print head 30 has a print head system shown in FIG.
It is controlled by device 31. Therefore, by appropriately controlling the jetting state of each marking nozzle, a desired character or symbol can be printed during the relative movement with the object to be printed. The control Il device 40 connects the distance sensor 20 to the tube 5.
The robot control lI moves on a plane perpendicular to the center line 54 of the tube 50 and close to the end surface 52 of the tube 50.
Based on the function as a distance sensor movement control means that instructs the v&M 11, the detection signal of the distance sensor 20, and the coordinate signal of the three-dimensional spatial position obtained from the detection signal of the sensor 1lff 12 to which the distance sensor 20 is attached. , the position of the end surface 52 of the tube 50, the center II of the tube 50! 54 position and the inner diameter of the pipe 5o, and based on the output of the pipe position/dimension calculation means, the pipe 50
It moves the print head 30 along the inner surface of the tube 50 while maintaining a constant distance from the inner surface of the tube, and also functions as a print control means for issuing commands to the print head control device 31. The operation of this embodiment will be explained below with reference to FIGS. 5 and 6. Once the pipe 5o has been transported to a predetermined position by the transport device a (not shown), the distance sensor 20 attached to the joint 12 of the articulated robot 10 is moved parallel to the end surface 52 as shown in FIG. In addition, it is moved on two prespecified intersecting straight lines L1 and LZ on adjacent surfaces while maintaining the vertical direction to the end surface 52. That is, the distance sensor 20 is placed on a surface perpendicular to the center line 54 of the tube 50 and close to the end surface 52 of the tube 50, from the starting point P1 of the straight line 41 L+ to the straight lines L1 and L.
2 to the end point P ++ of the straight line L2. During this movement, the distance sensor 20 is activated, and from the change in the measurement signal, that is, the change in the distance measured by the distance sensor 20, the straight line L1. Find each spatial coordinate of P2 to P10 on L2. The space locus 1 vote for each point of P2 to P10 is the direct I
It can be obtained by reading the coordinate signal of the tip of the joint 12 of the articulated robot 10 when the distance sensor 20 located on IL + and the straight line L2 detects the end face 52. Note that point P2 is one intersection of the straight line L1 and the outer surface 56 of the tube 50, point P3 is one intersection of the straight line L1 and the inner surface 58 of the tube 50, and point P4 is the other intersection of the straight line 11L+ and the inner surface 58 of the tube 50. The intersection point P5 is the other intersection point of the straight line [1 and the outer surface 56 of the tube 50. Similarly, points P7 and PIo are straight I
Intersection of I L 2 and the outer surface 56 of the tube 50, point Pa, P9
is the intersection of the straight line L2 and the inner surface 58 of the tube 50. In addition,
C indicates the intersection of the center line 54 of the tube 50 and the moving plane of the distance sensor 20 when collecting data for calculating the position and dimensions of the tube 50, that is, the center point of the tube 50. In addition, since the mass Ii robot 10 generally has a built-in pulse coder etc. in commercially available industrial robots,
The spatial coordinate position of the tip of the joint 12 can be automatically detected, and therefore the points P2 to Ps and the points P7 to
P to is used as a coordinate signal for the robot system till device 11.
Automatic detection is possible from Next, the point P3, P-1pH, P9 where the coordinate signal is 1
Using the coordinate signals of , the coordinate position of the center point C of a circle passing through these points P3, Pa, Pa, and P9 and its diameter d are determined by calculation. Although the calculation method is not particularly limited, it is performed as follows, for example. First, a straight line WAJ2+ passing through the midpoint q1 of the line segment (Pa, Pa) and orthogonal to the line segment (Pa, Pa), and a line segment (Pg, Ps) passing through the midpoint q2 of the line segment (Pa, P9). )
Find the center point C of the circle corresponding to the inner surface 58 of the tube 50 as the intersection with the straight line 12 perpendicular to m58
Find the diameter d of the circle corresponding to . Also, by substituting the coordinates of the three points exclusively for the intersections P3 and P4 between the straight line L1 and the inner surface 58 of the tube 50 and the intersection P between the straight line L2 and the inner surface 58 of the tube 5o into the equation of the circle, the coordinates of each of these points are calculated as follows. By solving the substituted equations simultaneously, the center point C of the circle corresponding to the inner surface 58 and the diameter d of the circle may be determined. or,
The position of the end surface 52 of the tube 50 is 11L in FIG.
Intersection points P2 and Ps between t and the outer surface 56 and inner surface 58 of the tube 50
Measurement is possible from the signal output of the distance sensor 20 between the two points. Next, the operation of printing on the inner surface 58 of the tube 50 will be described based on the data of the position of the end surface 52 of the tube 50, the position of the center aC of the tube 50, and the inner diameter of the tube 50 obtained in this way. a print head control device 31 that controls the print head 30;
, a print start timing signal and a print data signal from the print control means are inputted via the robot control device 11 . The robot control M] device 11 of the articulated robot 10 includes:
The operation contents according to the inner diameter of the tube 50 as the object to be printed are inputted in advance as a program, and the robot 1iI
I [To the device 11, an operation instruction signal for selecting a predetermined program based on the inner diameter calculated by the tube position/dimension calculation means is inputted from the printing control means. This operation instruction signal includes, in addition to the program selection signal, the origin of the distal end of the joint 12 of the articulated robot 1o on the spatial coordinate axis (a point in space determined in advance when the articulated robot 10 is powered up). Information on the respective positions of the end face 52 of the tube 50 and the center point C of the tube 50 is also included. Therefore, the robot control device 11 moves the print head within the tube for printing based on the operation instruction signal. This printing The movement of the head 30 within the tube is carried out as follows: First, a program corresponding to the inside of the tube 50 is selected;
As shown in FIG. 6, according to the data on the center point C of the tube 50 and the distance data between the end surface 52 of the tube 50 and the point Pn,
The tip of the joint 12 is the point P u, Az, A2, As, A
s, and moves along a trajectory that passes through HP sequentially. That is, the print head 30 at point Pn moves along the trajectory K to position A1 along the central axis 54 of the tube 50. Then, it moves forward as shown in 2 along the central axis 54 of the tube 50 to the internal point A2 of the tube 5o. The position of point A2 is between the point Pn and the pipe 50 which were actually measured in advance.
The distance between the end faces 52 is determined so that the print head 30 is inserted into the tube 50 at a predetermined distance from the end faces 52 . Next, the print head 30 rotates in the circumferential direction along the inner rjn 58 of the tube 50 to a point A3 on a movement locus 3 as shown in FIG. While moving on this movement trajectory 3, the print head 3
0 is operated to print a predetermined mark on the inner surface 58 of the tube 50. During the printing operation of the print head 3o, the ejection timing of the plurality of ejection nozzles is controlled by the print head tfilm device 3.
1, necessary printing is performed. In this case, the ejection timing is determined by the print head 30.
This is performed in synchronization with the relative movement of the tube 5o which is the object to be printed. In a typical printing device, the amount of movement of the print head is detected by a movement amount detector such as a rotary encoder to control the ejection timing of the dots. However, when an industrial robot is used as a carrier for the print head 30, as shown in FIG. Focusing on speed movement, accurate dot matrix printing can be performed by controlling the timing at a predetermined time set in advance. Next, after printing is completed at point A3, the print head 30
It moves along the central axis 54 of the tube 50 to a point A4 as shown in the movement trajectory 4. Next, it moves from this point A4 to the reference point HP and returns, completing the series of printing operations. The reference point HP is a predetermined standby position, and when the tube 50 is transported by a transport device (not shown), the joint 12 of the articulated robot 10, the print head 30, and the distance sensor 20
The position is such that it does not interfere with the pipe 50 or the conveying device. Therefore, according to this embodiment, the position and dimensions of the tube 50 can be accurately grasped, and the print head 30 can be moved within the tube 50 with high precision. Therefore, required characters and symbols such as the type, size, direction, and purpose of the tube to be printed can be printed automatically and extremely efficiently at predetermined positions on the inner surface of the tube 50. Moreover, any combination of characters and symbols can be automatically printed on any small-diameter tube to extremely large-diameter tube within the insertable range of the print head 30. In the above embodiment, the tube detection sensor is configured with a distance meter that uses a laser beam, but the present invention is not limited to this, and the distance to the object can be measured by, for example, the intensity of the electromagnetic field. An eddy current distance meter may also be used. Further, the conveying device for the tube 50 always keeps the end surface 5 of the tube 50
If it is possible to position 2 in a certain position,
The distance sensor 20 does not need to have a distance meter function, and may simply be configured to be able to detect the end surface 52 of the tube 5o. Furthermore, in the embodiment described above, in order to detect the position and dimensions of the end surface 52 of the tube 5o, when the distance sensor 2o is moved on a plane perpendicular to the center line 54 of the tube 50 and close to the end surface 52 of the tube 5o, , its movement trajectory is two intersecting straight lines Ll,
Although the folding line is made up of L2, the present invention is not limited to this, and may be made of two parallel straight lines, for example. Further, in the embodiment described above, the print head 30 is configured as a dot matrix print head, but the present invention is not limited to this.
Any other type of print head may be used as long as it can be inserted into the 0. Furthermore, in the embodiment described above, when printing, the timing of the print head 30 is controlled based on time, focusing on the fact that the tip of the joint 12 of the articulated robot 10 moves at a constant speed. The present invention is not limited thereto; for example, the print head 30 can be controlled by a rotary encoder.
Detects the actual amount of movement of the print head 30 based on this.
The timing control may be performed. However, in this case, since the print head 30 makes a turning motion that moves along the circumferential direction of the inner surface 58 of the tube 50, the radius of this turning movement varies depending on the inner diameter of the tube 50, so it is not a normal linear movement. Or compared to the case of simple rotational motion? ! ! Requires a crude structure. Further, in the embodiment described above, the print data input to the print head control device 31 can be input manually, but for example, when printing is performed within a tube manufacturing line, the print data may be input manually by a host computer that controls the line. (not shown), further automation can be achieved. Further, the scope of application of the present invention is not limited to printing on the inner surface of a tube, and it is also possible to print on any arbitrary position on the end face of a cylindrical body, for example. In this case, the diameter of the cylindrical body and the position of the central axis can be easily determined as a modification of the tube position/dimension detection method of the present invention. Furthermore, even without printing, it is easily possible to determine the outer diameter, inner diameter, wall thickness, etc. of a tube with a modification of the present invention, and it is also possible to automatically inspect the dimensions of a tube. For example, to determine the wall thickness of a tube, the inner diameter d of the tube 50 determined as described above and its center point C, and the intersection point P2 of the outer surface 56 of the tube 50 and the straight line 111LI, L2.
, P5, P7, PIO, etc., and calculate from the equation of the circle corresponding to the outer surface 56 of the tube 50 and the equation of the circle corresponding to the inner surface of the tube 5o described above. I can do it.

【Effect of the invention】

As explained above, according to the present invention, when printing on the inner surface of a tube, complicated positioning can be easily performed and the print head can be accurately moved within the tube, so automation can be achieved, thereby saving labor. It has excellent effects such as improving the efficiency of product process control.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the gist of the tube inner surface printing method according to the present invention, FIG. 2 is a side view showing the configuration of embodiments of the tube inner surface printing apparatus according to the present invention, and FIG. Block diagram showing the configuration of the control WAi device used in the example, Part 4
The figure is a side view showing the detection principle of the pipe detection sensor, and Fig. 5 is a front view showing the principle for detecting the position and dimensions of the pipe.
FIG. 6 is a side view showing the printing operation by the print head, M
FIG. 7 is a diagram showing joint movement of an articulated robot in terms of the relationship between time and speed. DESCRIPTION OF SYMBOLS 10... Articulated robot, 20... Distance sensor, 3o... Print head, 40... Control device, 50... Tube, 52... End surface.

Claims (4)

[Claims] (1) In a tube inner surface printing method for printing on the inner surface of a tube, a tube detection sensor is moved by an articulated robot on a surface perpendicular to the center line of the tube and close to the end surface of the tube, and the tube detection sensor is used to print on the tube. Obtain the detection signal and obtain the position where the tube detection signal was obtained as a coordinate signal in a three-dimensional space, calculate the position and dimensions of the tube using these tube detection signals and the spatial coordinate signal, and calculate the position and dimensions of the tube based on the calculation result. A method for printing on the inner surface of a tube, characterized in that a print head provided near a tube detection sensor is moved along the inner surface of the tube by a robot, and the print head is operated to print. (2) The movement of the tube detection sensor by the articulated robot on a surface perpendicular to the center line of the tube and close to the end surface of the tube is performed on a bending line whose movement trajectory is formed by two intersecting straight lines. A tube inner surface printing method according to claim 1. (3) The tube inner surface printing method according to claim 1 or 2, wherein the print head moves along the inner surface of the tube during printing at a constant velocity. (4) An articulated robot that has a plurality of joints and can move the tips of the joints to arbitrary positions in three-dimensional space, and a tube to be printed attached to the tips of the joints of the articulated robot. a tube detection sensor for detecting an end surface; a tube detection sensor movement control means for moving the tube detection sensor on a surface perpendicular to the center line of the tube and close to the end surface of the tube; a detection signal of the tube detection sensor; and pipe position/dimension calculation for calculating the end face position of the pipe, the center line position of the pipe, and the inner diameter of the pipe based on the three-dimensional spatial coordinate signal obtained from the detection signal of the joint to which the pipe detection sensor is attached. means attached to the joint to which the tube detection sensor is attached;
A printing head that prints on the inner surface of the tube, and moving the printing head inside the tube along the inner surface while maintaining a constant distance from the inner surface of the tube based on signals from the tube position/dimension calculation means. A tube inner surface printing device comprising: a printing control means for controlling a printing head;