JPH05241660A - Thermal deformation correcting method for electronic part loader - Google Patents

Abstract

PURPOSE:To keep the loading accuracy of electronic parts onto a substrate satisfactory for a long time by repeatedly executing position correction in a fixed cycle so as to correct position deviation while measuring the position of an adsorbing device to an image pickup device for recognizing parts. CONSTITUTION:An adsorbing nozzle 3 is loaded to an adsorbing device 12, and nothing is adsorbed to the nozzle 3. The adsorbing device 12 is positioned in the field of view above an image pickup device by operating a robot 1. The adsorbing device 12 is autonously positioned at every angle equally dividing a circumference, the image of the adsorbing nozzle 3 is picked up by an image pickup device 8 plural times such as fourtimes at every 90 deg., for example, and the central position coordinate of the silhouette of each image is measured. The average value of all the measured values is calculated, and this value is defined as the rotational center position coordinate of the adsorbing nozzle 3. At this time, when the thermal deformation of a ball screw 10 is in a transient state and it is estimated that the necessity of correction is high, the correction is repeatedly executed in the fixed cycle only during that period. On a stage where the ball screw reaches normal temperature and the extension is converged at a fixed value, the machine is continuously operated without being corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of correcting thermal deformation of a robot, and more particularly to a method of calibrating deformation of a robot carrying a mounting head of an electronic component mounting machine due to thermal expansion of components.

[0002]

2. Description of the Related Art Conventionally, an electronic component mounting machine having a structure for mounting an electronic component on a printed circuit board by moving a mounting head equipped with a suction device by the operation of a robot such as an orthogonal type or an articulated type is as follows. Electronic parts were attached according to the procedure.

An electronic component is imaged by an image pickup device for recognizing the electronic component fixed to the main body of the electronic component mounting machine in the middle of a path in which the suction device vacuum-sucks the electronic component from the component supply device and moves to the mounting target position. The displacement of the electronic component (first displacement) with respect to the suction device is measured, the mounting head is moved, and then the mounting target pattern printed on the printed circuit board is photographed by the pattern imaging device mounted on the mounting head. The displacement (second displacement) of the mounting target pattern with respect to the pattern imaging device, and the controller calculates the displacement (third displacement) of the suction device with respect to the mounting target pattern from the second displacement. Based on the displacement and the third displacement, the mounting head position at the time of mounting is corrected.

In the conventional method, when the electronic component sucked by the suction device is photographed, the image of the tip (that is, the nozzle) of the suction device cannot be captured by the image pickup device for recognizing the electronic component. Therefore, it is impossible to accurately measure the position of the suction device, which is directly affected by the position repeat error of the robot.

Even if the tip of the suction device is displaced from the origin position at the coordinates on the electronic component recognition screen, if the displacement is a constant two-dimensional vector amount, the origin position of the screen is calibrated to be substantially corrected. The mounting operation can be executed without any inconvenience. Generally, in the conventional method, prior to the automatic operation, an image of the tip of the suction device in the state where no component is sucked is photographed at a predetermined position at the time of detection, and the center of the image of the tip or the suction device is rotated. The axis of rotation of the tip at this time serves as the origin position of the output image of the electronic component recognition imaging device.

[0006]

However, for example, a ball screw, which is often used as a transmission / deceleration device for a robot, thermally expands with time due to heat generation or sliding friction of a drive device, so that heat is relatively transferred. The position that should be the origin of the electronic component recognition image when the position of the suction device during electronic component imaging shifts, as seen from the coordinate system attached to other components of the electronic component mounting machine. Also moved, and the initial calibration alone is useless.

It is possible to calibrate the origin position of the image once as a function of the elapsed time after the start of operation and refer to the calibrated value during the subsequent automatic operation.
That is, the operating conditions are different for each type of printed circuit board, and the amount of heat generated during the operation is also different, which is not very practical.

On the other hand, in general, as a method for correcting the deformation according to the change of the environmental temperature of the apparatus, a method of periodically measuring the environmental temperature, that is, the room temperature value and returning it to update the calibration position is also possible. In the electronic component mounting machine, the factor of linear expansion of the ball screw, which is mainly caused by sliding friction or heat generation of the driving device, is dominant, so the correlation between changes in environmental temperature and linear expansion is low, so use the environmental temperature. I can't. Even in an articulated robot that does not use a ball screw, the same problem occurs because the components are deformed due to the sliding friction of the transmission portion and the heat generation of the driving device.

Applied Mechanical Engineering, Volume 28, No. 4, (198
7 years), p98 to p103, "Ball screw heat generation and countermeasures", measures such as suppression of friction heat generation of the ball screw and cooling method are described. However, once thermal deformation has occurred, a method of performing calibration at an appropriate time with an appropriate method is considered to be the most reliable correction means. In an electronic component mounting machine, it is practical and efficient to visually calibrate using an electronic component imaging device at an electronic component imaging position.

In addition to the linear expansion of the ball screw, the ambient temperature, the influence of other elements of the electronic component mounting machine such as the mounting head, or the electrical characteristics due to heat generation after the start of energization of the electronic circuit of the image processing apparatus. Calibration is indispensable to collectively deal with the origin drift of the screen due to changes.

An object of the present invention is to provide a method of correcting an electronic component suction position recognition error caused by thermal expansion of a ball screw or the like to maintain good mounting accuracy of an electronic component on a printed circuit board for a long time. Especially.

[0012]

In order to achieve the above object, according to the present invention, a controller for an electronic component mounting machine is provided with a position calibration for measuring a position of a suction device with respect to a component recognition image pickup device and correcting a position deviation. The position calibration means is repeatedly executed at a preset timing at the start of the automatic operation and during the automatic operation.

[0013]

When the electronic component mounting machine starts and executes the automatic operation operation, the robot recognizes what is in the visual field of the component recognition imaging device fixed to the main body at a preset timing according to the position calibration means. Position the suction device that is not sucked or the suction device that is loaded with the position calibration jig, measure the stop position of the suction device with the imaging device, and the controller updates the origin position data in the field of view for component recognition. To do. The mounting position is corrected based on the updated origin position data.

The preset timing for updating the origin position data is, for example, immediately before the start of the automatic operation and after the start of the automatic operation in a constant cycle until a fixed number of electronic components are completely mounted. To do.

[0015]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a perspective view showing the configuration of an electronic component mounting machine to which each embodiment of the present invention is applied. The mounting operation of the electronic component mounting machine will be described with reference to FIG. The mounting head 2 is moved by the XY robot (biaxial orthogonal robot) 1 to the horizontal plane (X
Move in the (Y plane). One of a plurality of replaceable suction nozzles 3 is loaded at the tip of the suction device 12 provided on the mounting head 2. The mounting head 2 is moved above the electronic component supply device 4, and the suction device 12 is lowered to vacuum-suck the electronic component 5. The robot 1 is moved to position the suction device 12 above the imaging device 8 fixed to the main body of the electronic component mounting machine, and an image of the electronic component 5 is captured. Next, the robot 1 is moved again so that the imaging device 9 attached to the mounting head 2 is located above the initial commanded mounting position on the printed circuit board 6, and an image of the mounting target pattern 7 is captured, and image processing is performed. The device 14 and the control device 15 calculate a position correction amount from the data of the two images, and move the robot 1 so that the suction device 12 is located right above the corrected command mounting position. The suction device 12 is lowered again to mount the electronic component 5 on the mounting target pattern 7.

FIG. 3 illustrates how the origin position of the image moves due to thermal deformation of the ball screw. In the orthogonal robot 1 that uses the ball screw 10 as a transmission / reduction device, the ball screw 10 gradually increases in temperature and expands after the start of operation due to heat generated by the drive device 11 and sliding friction heat. The drive device 1 is operated according to the temperature rise and the coefficient of linear expansion of the ball screw 10.
The load movement distance of the robot 1 for a constant rotation angle of 1 increases.

In the electronic component mounting machine, the positional accuracy of the XY robot 1 is high when the electronic component 5 sucked by the suction nozzle 3 mounted on the tip of the suction device 12 is photographed and when it is mounted on the printed circuit board 6. Especially required. Normally, at the mounting position, an image of the printed circuit board 6 is taken by the image pickup device 9 attached to the mounting head 2 every time the mounting operation is performed, and the image between the mounting head 2 and the mounting target pattern 7 (including the influence of thermal deformation is included). Since the relative position is calculated, it is not necessary to calibrate repeatedly only for the correction of thermal deformation. However, at the electronic component photographing position, it must be repeatedly positioned at a fixed position on the coordinate system of the image pickup device 8 fixed to the main body of the electronic component mounting machine. Since the imaging device 8 is hardly affected by thermal deformation and the stop position of the mounting head 2 gradually moves due to thermal expansion, the center position of the suction nozzle 3 is appropriately calibrated to update the origin position.

FIG. 1 shows the operation schedule of the first embodiment of the present invention. In FIG. 1, the horizontal axis represents time. The arrow indicates the time of calibration. After the automatic operation is started, the calibration is executed every constant period T (<T ₀ ) until the constant time T ₀ elapses. For example, assuming that T ₀ = 60 minutes and T = 15 minutes, a total of 5 at time t = 0, 15, 30, 45, 60 minutes.
Perform calibration once.

The automatic calibration work is performed in the following procedure. The adsorption device 12 is loaded with the adsorption nozzle 3, and nothing is adsorbed on the adsorption nozzle 3. Alternatively, as another method, the adsorption device 12
In place of the suction nozzle 3, one position calibration jig 13 is loaded. The bottom surface of the position calibration jig 13 is placed at the same height as the tip height of the suction nozzle 3. The robot 1 is operated to position the suction device 12 within the field of view above the imaging device 8. An image of the suction nozzle 3 (or the position calibration jig 13) is picked up by the imaging device 8 a plurality of times (circumferential division number) four times, for example, four times by rotating the suction device 12 by an angle that divides the circumference equally. Is photographed and the center position coordinates of the silhouette of each image are measured. The average value of all the measured values is calculated and used as the rotation center position coordinate of the suction nozzle 3.

According to the present embodiment, the repetitive calibration is executed only during the period when the thermal deformation of the ball screw 10 is in the transient state and the necessity of the calibration is expected to be great, and the ball screw 10 reaches the steady temperature, At the stage where the elongation is expected to converge to a constant value, continuous automatic operation can be performed without interruption due to calibration, so that there is an effect that accurate and efficient calibration becomes possible. Further, even when origin drift due to a change in electrical characteristics due to heat generation after the start of energization simultaneously occurs in the electronic circuit of the image processing apparatus 14, accurate and efficient calibration becomes possible.

Further, according to the method of loading with a single position calibration jig, calibration can be performed with high reproducibility and high accuracy without being affected by the dimensional error of each suction nozzle.

It should be noted that, instead of executing calibration every fixed period T until a fixed time T ₀ has elapsed after the start of automatic operation,
Almost the same effect can be obtained by a method in which calibration is executed at regular intervals T until the mounting of a predetermined number of electronic components is completed. Further, as a more practical method, it is conceivable that after the time T has passed from the time of the previous calibration, a new calibration is executed immediately before the mounting on the next substrate is started.

FIG. 4 shows the operation schedule of the second embodiment of the present invention. The calibration is executed when the electronic component mounting machine starts the automatic operation, every time when the mounting on a fixed number of printed circuit boards is started after the operation is started, or when the mounting on the fixed number of printed circuit boards is completed. Immediately before the start of the automatic operation operation, and after the mounting on each of the N printed boards is completed, the calibration work is automatically performed immediately before the mounting on the next N printed boards is started. The calibration work is repeated every time the printed circuit board is mounted.

According to this embodiment, it is possible to perform accurate calibration in response to the deformation of the ball screw due to the thermal expansion after the start of operation, and the mounting accuracy of electronic parts is improved.

By executing the calibration at the start of operation once, the temperature conditions at the start of operation can be considered to be almost the same every time after the rest period of a certain time or more. It is also possible to omit the calibration every time the automatic operation starts and perform the calibration only during the automatic operation.

FIG. 5 shows the operation schedule of the third embodiment of the present invention. The calibration is executed every time the mounting of a certain number of electronic components is completed after the start of the automatic operation. The present embodiment also has the effect that accurate calibration can be performed almost as in the second embodiment.

Further, even when the target printed circuit board is large and the time required to mount it on one printed circuit board is long, the position can be finely corrected.

FIG. 6 shows the operation schedule of the fourth embodiment of the present invention. After starting the automatic operation, the calibration is executed every time a predetermined constant time T elapses. According to this embodiment, accurate calibration can be performed almost as in the third embodiment.

[0030]

According to the present invention, since the origin position data in the visual field for recognizing a component can be updated at any time, the robot of the robot at the time of recognizing the electronic component while continuing the automatic driving operation due to the thermal deformation of the components of the electronic component mounting machine can be updated. Even if the stop position moves, the relative position of the electronic component with respect to the suction device can be correctly measured. Therefore, the mounting accuracy of the electronic component on the printed circuit board can be kept good for a long time immediately after starting.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an operation schedule according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of an electronic component mounting machine to which each embodiment of the present invention is applied.

FIG. 3 is an explanatory diagram showing a state in which an image origin position moves due to thermal deformation.

FIG. 4 is an operation schedule diagram of the second embodiment of the present invention.

FIG. 5 is an operation schedule diagram of the third embodiment of the present invention.

FIG. 6 is a diagram showing an operation schedule according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... XY robot, 2 ... mounting head, 3 ... suction nozzle,
4 ... Electronic component supply device, 5 ... Electronic component, 6 ... Printed circuit board, 7 ... Mounting target pattern, 8 ... Imaging device, 9 ... Imaging device, 10 ... Ball screw, 11 ... Driving device, 12 ... Adsorption device, 13 ... Position calibration jig, 14 ... Image processing device, 15 ...
Control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Naoji Aji, 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo, Hitachi, Ltd. Inside the mechanical laboratory

Claims (1)

[Claims] 1. An electronic component mounting machine having a structure in which a mounting head equipped with a suction device is moved by a robot operation to mount an electronic component on a printed circuit board, wherein the robot has a main body at a predetermined point during automatic operation. In the field of view of the imaging device for component recognition fixed to the part, the suction device is positioned, and the stop position of the suction device is measured by the imaging device,
A method for correcting thermal deformation of an electronic component mounting machine, characterized in that the control device updates the origin position data in the component recognition visual field based on the measurement result.