JPH0822501B2 - Automatic grinding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to finishing of welding excess or deburring of a workpiece,
The present invention relates to an automatic grinding device used for chamfering and the like.

[Prior Art] An apparatus for automating a grinding operation for removing a welding surplus to finish it flat and deburring or chamfering a workpiece is known, for example, from Japanese Patent Laid-Open No. 121169/1989. ing.

As shown in FIGS. 8 and 9, the device disclosed in the above-mentioned Japanese Patent Laid-Open Publication holds a constant speed rotary electric grinder 24 in which the motor load current increases and decreases according to the magnitude of the grinding amount per unit time, and the grinder. It comprises a slider 8, a slide mechanism 6 for moving the slider up and down, a traveling carriage 4, and a guide rail 1. The trolley 4 travels at a constant speed in parallel with the line to be ground (welding surplus) 51 by the guide rail 1. The pinion 2 is projected to the lower part of the trolley 4, and this is engaged with the rack 3 provided on the guide rail 1. A traveling motor (not shown) is built in the traveling mechanism 5, and the carriage 4 is caused to travel at a constant speed in the longitudinal direction of the rail by rotating the pinion 2 via the speed reduction mechanism.

The slide mechanism 6 controls the heightwise distance between the electric grinder 24 and the welding surplus 51, and a support block inside the slider is screwed onto the output shaft of the slide lifting motor at the upper end for lifting. The slider 8 is moved up and down by the rotation of the motor 7. A holder 9 is provided on the front part of the slider 8 and the electric grinder 24 is attached.

When the carriage 4 is run at a constant speed along the line to be ground (welded surplus) 51, the slide mechanism 6 is controlled so that the load current of the grinder motor 24 becomes constant, and as a result, the grindstone disk 26 is consumed. The grinding amount per unit time mm ₃ / min is always kept constant. Therefore, as shown in Fig. 10, the base metal
On the surface of 50, there is a hemisphere 51 with a height of b and a semi-circular cross section.
As shown in Fig. 11, if the base metal surface is almost uniformly present along the weld line, even if the base metal surface is gently uneven, the grinding removal amount e (remaining amount s) of the extra height b can be tracked accordingly. Can be finished evenly. Moreover, unlike the method of controlling the pressing force, it is not affected by gravity, so the control performance does not change even if grinding is performed in any posture such as sideways or upward.

[Problems to be Solved by the Invention] On the other hand, when the apparatus is started at the grinding start point, it is necessary to start the rotation of the grinder motor in a state where the grindstone is not in contact with the object to be ground. As the operation method after that,
(A) The slide control circuit (not shown) and the carriage traveling are started at the same time. (B) First, only the slide control circuit is started, and since the grinder motor load current is small, the slide switch is automatically lowered and the traveling switch is turned on when the grinding lowering is started. (C) There are three ways of lowering the slide mechanism by the switch operation and starting the slide control circuit and the carriage traveling at the time when the grinding lowering is started.

Of these, (a) can be automatically started by an external command, but an unground portion remains near the grinding start point. (B) and (c) are practical methods that do not produce unground portions, but the operator must operate the switch while monitoring.

In the trolley traveling system as shown in FIGS. 8 to 9, since the start at the grinding start point is originally dependent on human beings, the need for monitoring is not so problematic. However, when a robot is used as the traveling mechanism to grind multiple locations by program control, naturally each grinding start point is automatically activated by a start signal, so the conventional method inevitably leaves unground areas. . Further, when grinding all the way to the ridge A of the object to be ground (Fig. 12), the slide control mechanism lowers the slide mechanism at the ridge A, so that when the robot reaches the next descending start point, the grindstone There is a risk of colliding with the object to be ground.

Similarly, since the slide mechanism is automatically lowered as the grindstone is consumed, the grindstone may collide with the object to be ground when the robot reaches the next processing start point after the grindstone is replaced with a new grindstone. Further, when the grinder motor is stopped in the grinding state at the end of the grinding process, the phenomenon that the grindstone bites into the object to be ground due to the inertial rotation and scratches the surface of the base material cannot be avoided.

Generally, when machining with contour control in which a rotary tool is moved along a programmed contour of a workpiece, US Pat.
As in 96360, the feed rate is controlled so that the rotation torque reaches the target value, but if the wear of the tool can be ignored, it is possible to perform efficient machining with programmed contour control. . However, grinding with a grinding wheel disk inevitably involves wear of the grinding stone, and therefore it is impossible to perform grinding simply by moving the grinding stone along a grinding line (contour).

Therefore, in the present invention, an industrial robot is used as a traveling mechanism that moves along a three-dimensional programmed contour, a slide mechanism is attached to the wrist of the robot, and this slide mechanism moves the grinder toward or away from the workpiece. By keeping the grinder motor current constant, the grindstone wear is compensated and the grinding amount is kept constant so that it does not collide with the object to be ground, does not bite, and does not damage the base metal surface. The purpose is to provide an automatic grinding machine.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a multi-joint type or rectangular coordinate type industrial robot as a traveling mechanism, and a sliding mechanism for supporting an electric grinder on a wrist portion of the traveling mechanism. It is installed.

That is, the automatic grinding apparatus of the present invention includes an electric grinder including a constant-speed rotary motor whose load current increases and decreases according to the magnitude of the grinding amount per unit time and a grindstone disk driven by the motor; An industrial robot which is a multi-joint type robot or a rectangular coordinate type robot; and a slide mechanism attached to the wrist part of the industrial robot so as to move the electric grinder three-dimensionally along the grinding surface of the workpiece.
A programmable controller for controlling the electric grinder and the slide mechanism in response to signals for starting, returning to the origin, and stopping from the controller of the robot; and a control circuit connected to the programmable controller; the slide mechanism for the grinding surface. The motor includes a lifting motor for adjusting the height of the grindstone disk, and a slider that moves up and down by driving the motor and supports the electric grinder on the front surface. The control circuit has a grinder motor at a grinding start point. And a timer means for driving the slide mechanism to bring the grindstone disk closer to the grinding surface after the idling current of the motor stabilizes; and the grindstone disk grinds by the change of the load current of the grinder motor. When contact with the surface is detected, there is a time lag or a time lag. Detecting means for outputting a drive signal to the traveling mechanism; means for controlling forward / backward drive of the lifting motor so that the load current of the grinder motor during grinding is equal to a set value; and of the grinder motor during grinding. A means for controlling the forward / backward drive of the lifting motor so that the load current matches the set value; temporarily stopping the control mechanism of the slide mechanism at any time during the grinding process, and connecting the grinder and the slide mechanism. A means for holding the relative position as it is, and a method of lowering the slider to a constant position of the elevating stroke by lowering the slider from the upper end of the elevating stroke at a constant speed for a fixed time before starting the grinding process. And a return-to-origin means.

The origin returning means in the control circuit may be composed of a potentiometer that directly detects the displacement of the slider from the reference position, and a lifting motor drive unit that restores the slider to a fixed position of the lifting stroke by the output signal of the potentiometer. Good.

[Operation] The load current of the electric grinder is detected, and when it is smaller than the set current value, the grinder is lowered to approach the work. Conversely, when the actual load current is larger than the set current value, the electric grinder is set to the work. The raising / lowering motor is driven so as to rise so as to separate from. Since the load current of the grinder is kept constant in this way, a certain amount of excess can be removed by grinding as long as the traveling speed of the grinder is constant. Therefore, if the height and width of the surplus are uniform over the entire length of the weld line, such as with automatically welded beads, even if the base metal surface is deformed along the weld line, it will automatically follow the base metal surface. Weld surplus can be removed by grinding.

It is possible to control the grinder load to be constant with the industrial robot itself, but since the mass of the robot body is large and the rigidity of the joints is insufficient, delay in tracking the wrist is inevitable. is there. On the other hand, in the present invention, while the robot is used as a traveling mechanism, a slide mechanism is attached to the wrist and a lightweight grinder is controlled by one axis in the sliding direction to improve the followability.

Moreover, since the uniaxial slide mechanism attached to the wrist of the robot follows wear of the grindstone disk and displacement of the surface to be ground, the robot body has no special control load other than traveling the wrist according to a predetermined teaching locus.

[Embodiment] FIG. 1 is a front view of the device of the present invention, and FIG. 2 is a block diagram of circuit control.

The following example shows a case in which an articulated industrial robot is used as a traveling mechanism and applied to an apparatus for grinding and removing weld surplus.

From the top of the column 11 several joints 12, 1
An articulated robot 10 is used which causes a distal arm 17 to make a three-dimensional movement via 3, 14 and arms 15, 16. A slide mechanism 20 is fixed to the tip arm 17 as shown in the figure, a swivel plate is provided on the slider 22, and a constant-speed rotary electric grinder 24 that increases or decreases the load current according to the amount of grinding per unit time is attached. . The electric grinder 24 includes a motor 25 and a grindstone disk 26. As disclosed in the above-mentioned Japanese Patent Laid-Open Publication, the slide mechanism 20 includes an upper lifting motor 21.
And a screw erected via a reduction gear provided on the motor output shaft, and a support block. The support block meshes with the screw and has a slider 22 at the front. The grindstone disk 26 is arranged immediately above the welding surplus 51 of the workpiece 50 set on the underframe 28, and grinds the surplus 51 by bringing the grindstone disk 26 close to each other according to a predetermined program.

FIG. 2 shows a block diagram of a control circuit when an AC reversible motor is used as the lifting motor 21. In an actual device, a programmable controller (not shown) is connected to each element to control a single operation sequence.

This control circuit, when starting the grinder motor 25 at the grinding start point, a timer means for driving the slide mechanism 20 to bring the grindstone disk 26 closer to the grinding surface after the idling current of the motor is stabilized, At the same time as detecting that the grindstone disk 26 has come into contact with the grinding surface due to a change in the load current of the grinder motor 25, or a detection means for outputting a drive signal to the traveling mechanism with a time lag, the load of the grinder motor during grinding. A means for controlling the forward / backward drive of the lifting motor so that the current matches the set value, and by regulating the operating time of the lifting motor 21 before and after the grinding process, the grindstone disk 26 and the slide mechanism 20. And an origin returning means for restoring the relative position of the above to a constant state.

The motor 25, the traveling motor 27, and the lifting motor 21 of the electric grinder 24 are all driven by a power source 30 (for example, AC 100V) via an overload prevention circuit 33 (FIG. 2).

The traveling motor 27 [generally refers to each motor for turning or rotating each rotary joint (joint) on the waist, shoulder, and elbow of the robot, twisting the wrist, and tilting] is a signal from a robot controller (not shown). Thus, the grindstone disk 26 of the electric grinder attached via the slide mechanism 20 of the wrist is driven to run so as to come to the surface to be ground. The motor 25 of the grinder is kept at a constant rotation speed by an electronic control circuit regardless of the amount of grinding.

At that time, the fluctuating load current of the motor 25 is detected by the current detector 34.
Detected by the rectifier circuit 31 and the smoothing circuit 32, and displayed on the load current display scale and sent to the comparator 36.
The comparator 36 compares the current value set in advance in the current value setter 35 and the load current, and when the absolute value of the difference exceeds the value set in advance in the sensitivity adjustment circuit 39,
Depending on whether the error is positive or negative, the forward / reverse switching circuit 37 composed of a flip-flop is operated to rotate the lifting / lowering motor 21 forward or backward. If a current value is programmed and input from the robot controller instead of the current value setter 35, a set current value different for each grinding point can be input and the grinding amount can be arbitrarily selected.

A forward / reverse switching circuit 37 that switches the rotation direction of the lifting motor 21 according to a home return signal from a programmable controller (not shown), a limit switch 44 that detects the upper limit position of the slider 22, and a lowering of the slider 22 for a certain time from the upper limit position. A means for returning the slide mechanism to the original point is configured by a timer that drives the lifting motor 21 to perform the above.

Further, the returning means detects the position of the slider 22 in the slide mechanism directly with a potentiometer (not shown) instead of lowering the slider from the upper end of the elevating stroke at a constant speed for a fixed time within the set time of the timer, The raising / lowering motor 21 may be driven such that

Note that the weld surplus may have local protrusions at the seams of the weld beads, etc., unlike the oxide scale of the steel plate, and during grinding, the grinding stone rotating at high speed collides with the protrusions. If it is damaged, fragments will be scattered and it is very dangerous.
Therefore, an overload prevention circuit 33 is provided which operates when such an abnormal situation occurs and the load current of the electric grinder reaches a limit value.

When the load current of the liner motor 25 exceeds the allowable limit value, the overload prevention circuit 33 operates and the power supply 30 is shut off, and the rotation of the grinder motor 25, the traveling motor 27, and the lifting motor 21 is stopped. Stop to prevent burnout of grinder and damage of grindstone. In addition to the above, FIG. 2 shows terminals for inputting start, control stop, origin return, and stop signals from the robot controller, load detection circuit 38, and timers T1 to T.
4, there are relays 41-43 and limit switch 44.

 Next, the operation of the above device will be described.

First, the relay 41 is turned on by the start signal, the grinder motor 25 starts to rotate, the relay 43 is turned on after a delay of the titer T1, and the slider 22 is lowered by the slide lift motor 21. At this time, the load detection circuit 38 monitors the smoothed load current of the grinder motor 25, and delays the timer 42 from the moment when it exceeds a certain level to close the relay 42 and close the running motor.
Start 27.

FIG. 6 shows the start-up operation in relation to the grinder motor load current. The load current of the grinder motor 25 rises immediately after starting and reaches P, but at the rated speed, it drops to Q and stabilizes. After the timer T1, the slider is lowered, and at the same time, the load detection circuit 38 also starts monitoring.
Then, when the grindstone comes into contact with the object to be ground, the load current again starts to rise, so that the load detection circuit 38 starts the traveling motor 27 with a delay of the timer T2 from the moment when the threshold value R is exceeded. So, T1 is almost constant (usually about 2 seconds),
T2 is T2 to prevent excessive cutting when the load setting value S is small.
Is brought closer to O.

Next, when a control stop signal is input, the relay 43 is disconnected, so that the relative position between the slide mechanism 20 and the grinder is fixed as it is. For example, when trying to grind all the way up to the ridge C of the object to be ground as shown in FIG. 3, if the slide control is temporarily interrupted at the point B before that, the slide mechanism descends too much at point C and the next machining starts. There is no possibility that the grindstone will collide with the object to be ground at point D. The consumption of the whetstone between BC can be ignored. Further, when the robot moves from C to D, the slide control function is already stopped at the point B, so that the grinder motor 25 can be moved while rotating. If the slide control function is not stopped, the sliding mechanism 20 will move to the lower limit during movement. Further, if the control stop signal is released when the point D is reached, the relay 43 is turned on and the slide control function is restored, so that the electric grinder immediately descends and the grinding process can be started.

Furthermore, by stopping or restoring the slide control function, it is possible to deal with irregularities on the surface to be ground. For example, as shown in FIG. 4, when the uneven swell 51 is ground while slidingly controlled, the unevenness remains on the finished surface, and the swell 51 remains and the base material 50 is cut. In that case, as shown in FIG. 5, the load setting value is reduced to start the pre-grinding from the point A, and the slide control is stopped at the point B where the slide control starts to function, and only the convex portion is removed first. Since the load setting value is small, the consumption of the grindstone during preliminary grinding is small.
Therefore, if final grinding is performed while sliding control is performed again, the final finished surface will be flat.

Next, the operation of the slide mechanism in response to the origin return signal will be described. When an origin return signal is input from the controller, the forward / reverse switching circuit 37 is actuated to cause the slider up / down motor 21 to normally rotate to raise the slide mechanism 20. Although it reaches the upper limit switch 44 and stops, the forward / reverse switching circuit 37 immediately operates to reverse the slider lifting motor 21 to lower the slider 22 and stop by the timer T3 (FIG. 7). If the rotation speed of the lifting motor 21 and the setting of the timer T3 are constant, this operation always restores the relative position of the slide mechanism and the grinder to a constant state. If this function is used, the robot will always be taught with the grindstone disk returned to the origin position, and the robot will return to the same origin position when starting work after the grindstone height position is unknown or when starting up after exchanging the grindstone. be able to. The timer T3 is set such that the origin is located at a position slightly higher than the center of the stroke of the slide mechanism 20.

As a means for returning to the origin, in addition to the above embodiment,
The position of the slider 22 in the slide mechanism 20 may be directly detected by a potentiometer, and the lift motor may be driven so that the distance from the upper or lower reference position is constant.

When the stop signal is input, the relay 41 and the relay 42 are turned off to stop the traveling motor 27 and the grinder motor 25, and at the same time, the slider elevating motor 21 is normally rotated to raise the slider 22, and the timer T4 is activated. Stop. With this operation, the grindstone stops rotating while being separated from the object to be ground, so there is no risk of scratching the ground surface. Also, the slider
The rise of 22 also prevents the grindstone from colliding with the object to be ground at the next processing start point.

FIG. 7 shows the origin return, activation, control, and control stop of the slide mechanism 20 (movement of the grindstone disk in the air or in the case of machining a work piece having two separate grinding surfaces as shown in FIG. 3). It is a time chart of operation including air cut) and stop.

EFFECTS OF THE INVENTION According to the present invention, since the industrial robot is used as the traveling mechanism and the slide mechanism is attached to the wrist of the robot, the object to be ground is approached when the load current of the grinder motor is smaller than the set value. If the load current is larger than the set value, the load current is increased so as to separate from the object to be ground. Since this lifting operation is one-axis control by the slide motor, it has excellent followability and reduces the load of robot operation control. Further, it is possible to automatically grind a plurality of places by a program operation. That is, since the vehicle is run after detecting that the grinding has started, predetermined grinding can be performed even when the position of the object to be ground is different from that at the time of teaching. In addition, the ground surface with deformation and irregularities can be finished smoothly, and it is safe to move to the next processing start point with the grinder still rotating after grinding all the edges of the object to be ground. Further, no matter where in the grinding surface the grinding process is stopped, there is an effect that the part is not bitten and scratched.

[Brief description of drawings]

FIG. 1 is a front view of the automatic grinding apparatus of the present invention, FIG. 2 is a block diagram of a control circuit, FIG. 3 is a vertical cross-sectional view of grinding portions at a plurality of places, and FIGS. Fig. 6 is an enlarged vertical cross-sectional view of the welding surplus with unevenness, Fig. 6 is an operation time chart at start-up, Fig. 7 is a time chart including return to origin, start-up, control, control stop, stop, and Fig. 8 is conventional. Fig. 9 is a side view of Fig. 8, Fig. 9 is a side view of the weld surplus, Fig. 11 is a longitudinal cross-section of Fig. 10, and Fig. 12 is an object to be ground. FIG. 6 is a cross-sectional view showing a lowered state of the grinder when processing up to the ridge line of FIG. 10 …… Articulated industrial robot, 15, 16, 17 …… Arm, 20 …… Slide mechanism, 21 …… Lifting motor, 22 ……
Slider, 23 ... Holder, 24 ... Electric grinder, 25 ...
… Grinder motor, 26 …… Grindstone disk, 27 …… Traveling motor, 28 …… Underframe, 30 …… Power supply, 31 …… Rectifier circuit,
32 …… Smoothing circuit, 33 …… Overload prevention circuit, 34 …… Current detection unit, 35 …… Current value setting device, 36 …… Comparator, 37 …… Forward / reverse switching device, 38 …… Load detection circuit, 39 …… Sensitivity adjustment circuit,
T1 to T4 …… Timer, 41 to 43 …… Relay, 44 …… Limit switch, 50 …… Base metal surface, 51 …… Welding surplus.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Hatta 5-3-20 Kitashinagawa, Shinagawa-ku, Tokyo Aiko Engineering Co., Ltd. (56) Reference JP-A-1-121169 (JP, A) JP Sho 61-216003 (JP, A) Actually opened Sho 61-117663 (JP, U)

Claims (2)

[Claims] 1. An electric grinder comprising a constant speed rotary motor whose load current increases and decreases according to the amount of grinding per unit time and a grindstone disk driven by the motor; and an articulated type equipped with a wrist. Or an industrial robot which is a Cartesian coordinate type robot; a slide mechanism attached to the wrist of the industrial robot to move the electric grinder three-dimensionally along the grinding surface of the workpiece; A programmable controller that controls the electric grinder and the slide mechanism in response to a signal for returning to the origin and a stop; and a control circuit connected to the programmable controller; the slide mechanism adjusts the height of the grindstone disc with respect to the grinding surface. And a motor for raising and lowering the electric motor to drive the motor to raise and lower and to the front side of the electric grinder. A slider that supports the grinding wheel; and the control circuit drives the slide mechanism after the idling current of the motor is stabilized when the grinder motor is started at the grinding start point to drive the grindstone disk to the grinding surface. And a detecting means for outputting a drive signal to the traveling mechanism at the same time as or when a time lag is detected when it is detected that the grindstone disk has come into contact with the grinding surface due to a change in the load current of the grinder motor; Means for controlling forward / backward drive of the lifting motor so that the load current of the grinder motor matches with a set value during machining; temporarily stopping the control function of the slide mechanism at any time during grinding Means for holding the relative position between the slide mechanism and the slide mechanism as it is at that time, and raising the slider before starting the grinding process. An automatic grinding device, comprising: an origin returning unit that restores the slider to a constant position of an elevating stroke by lowering the slider from the upper end of the descending stroke at a constant speed for a certain period of time. 2. An electric grinder comprising a constant speed rotary motor whose load current increases and decreases according to the amount of grinding per unit time and a grindstone disk driven by the motor; and an articulated type equipped with a wrist. Or an industrial robot which is a Cartesian coordinate type robot; a slide mechanism attached to the wrist of the industrial robot to move the electric grinder three-dimensionally along the grinding surface of the workpiece; A programmable controller that controls the electric grinder and the slide mechanism in response to a signal for returning to the origin and a stop; and a control circuit connected to the programmable controller; the slide mechanism adjusts the height of the grindstone disc with respect to the grinding surface. And a motor for raising and lowering the electric motor to drive the motor to raise and lower and to the front side of the electric grinder. A slider that supports the grinding wheel; and the control circuit drives the slide mechanism after the idling current of the motor is stabilized when the grinder motor is started at the grinding start point to drive the grindstone disk to the grinding surface. And a detecting means for outputting a drive signal to the traveling mechanism at the same time as or when a time lag is detected when it is detected that the grindstone disk has come into contact with the grinding surface due to a change in the load current of the grinder motor; Means for controlling forward / backward drive of the lifting motor so that the load current of the grinder motor matches with a set value during machining; temporarily stopping the control function of the slide mechanism at any time during grinding Means for holding the relative position between the slider and the slide mechanism as it is at that time; and a direct detection of the displacement of the slider from the reference position. An automatic grinding machine comprising: a potentiometer, and an origin-returning means, which is composed of a lifting motor drive unit that restores the slider to a fixed position of the lifting stroke according to the output signal of the potentiometer.