JP2014040001A - Workpiece processing device and control method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a workpiece processing device that can prevent breakage or the like of a tool while maintaining processing accuracy even if impulsive processing reaction force occurs when a workpiece of a hard material such as cast iron is processed, and further to provide a control method therefor.SOLUTION: A workpiece processing device comprises: a force sensor 12 that is mounted to a robot hand three-dimensionally movable and detects external force applied thereto; a copying jig 14 that is mounted to the force sensor 12 and has a copying member 15 for copying an outer surface of a workpiece 1; a processing tool 16 that is mounted to the copying jig 14 and processes the workpiece 1; and a processing controller 20 for force controlling copying jig pressing force Fall of the copying jig 14 with respect to the outer surface of the workpiece 1 such that a value of the copying jig pressing force Fall is greater than an expected maximum value of processing reaction force R. The workpiece processing device moves the copying jig 14 along the outer surface of the workpiece 1 while copying the outer surface of the workpiece 1 by the copying member 15 and processes the workpiece 1 by the processing tool 16.

Description

  The present invention relates to a workpiece processing apparatus that is used by being attached to a robot hand such as an industrial robot, and a control method thereof.

For example, Patent Documents 1 and 2 have already been proposed as "work processing apparatuses" that are used by attaching to a robot hand such as an industrial robot to perform cutting processing and grinding processing such as deburring, C-chamfering, and round edge processing. ing.
The “force control device and robot using the same” disclosed in Patent Document 1 measures a machining reaction force generated by cutting and teaches in advance while controlling the force so that the force pressing the cutting tool against the workpiece becomes a set value. Machining along the trajectory.
In addition, the “work copying apparatus” in Patent Document 2 processes a work having a variation in shape while copying a reference surface.

Japanese Patent No. 3217351 JP 2002-370116 A

FIG. 1 is a schematic diagram showing a tool pressing force (A) and a tool displacement (B) in the control of Patent Document 1.
As shown in FIG. 1A, when the force control is performed so that the tool pressing force Ft becomes a target value, there is a problem that the variation of the machining reaction force R cannot be followed. That is, when a hard material such as cast iron is machined by the control means of Patent Document 1, even if an attempt is made to feed back the deviation of the tool pressing force Ft from the target value to bring it closer to the target value, high-frequency vibration and impact force In a normal control cycle, the control cannot catch up and the position of the tool is displaced, which adversely affects the machined surface. For this reason, as shown in FIG. 1B, the workpiece machining apparatus attached to the robot hand occurs in a direction other than the direction away from the workpiece or the direction away from the workpiece due to the impact force. (For example, if the machining reaction force suddenly decreases, the tool must be pressed accordingly.)
In any case, since it is difficult to control so as to cancel out the severe fluctuation of the tool reaction force in the normal control cycle, there is a problem in that the machining accuracy is deteriorated or the tool is broken.
Moreover, since the means of patent document 2 which processes while following a reference surface is intended for the product of a comparatively soft material, it cannot apply to the workpiece | work of hard materials, such as cast iron. Further, since the buffer mechanism is provided, there is a problem that the machining accuracy is deteriorated due to the fluctuation of the machining reaction force.

The present invention has been developed to solve the above-described problems. That is, the first object of the present invention is to maintain machining accuracy and prevent damage to tools even when a shocking reaction force occurs when machining a hard material such as cast iron. An object of the present invention is to provide a workpiece processing apparatus and a control method thereof.
In addition, a second object of the present invention is to provide a workpiece machining apparatus and a control method for the workpiece deburring, C-chamfering, round edge machining, plane machining, and workpiece machining apparatus capable of following the workpiece if there is a reference shape. Is to provide.
Furthermore, a third object of the present invention is to provide a workpiece machining apparatus capable of changing the dimensions of C chamfering and round edge machining, and a control method therefor.

According to the present invention, a force sensor is attached to a movable robot hand that covers six degrees of freedom of space and detects an external force acting on the robot hand.
A copying jig having a copying member attached to the force sensor and copying the outer surface of the workpiece;
A machining tool attached to the copying jig or the robot hand for machining a workpiece;
A machining control device for force-controlling the copying jig pressing force against the workpiece outer surface of the copying jig to a value larger than the maximum value of the expected machining reaction force;
There is provided a workpiece machining apparatus that moves a copying jig along the outer surface of the workpiece while copying the outer surface of the workpiece with the copying member, and processes the workpiece with the machining tool.

  According to the reference example, the copying jig has a spring that urges the copying member toward the outer surface of the workpiece, and the spring constant of the spring ignores the displacement of the copying jig due to variation in the processing reaction force. The size is set as large as possible, and is set so as to be within the required processing accuracy.

  Further, the copying member includes a first copying member and a second copying member that copy two surfaces of a workpiece sharing a C surface or an edge to be rounded.

  According to a preferred embodiment of the present invention, the first copying member and the second copying member are each composed of a spherical roller or a curved roller.

  According to another preferred embodiment of the present invention, a tool moving device attached to the copying jig and moving the machining tool on a straight line or a curve is provided.

  (1) having a spring that biases the copying member toward the outer surface of the workpiece, (2) the copying member is made of a spherical roller, (3) a tool moving device that moves the machining tool, etc. The dimensions of chamfering and round edge machining can be varied.

Further, according to the present invention, a force sensor that is attached to a movable robot hand covering six degrees of freedom of space and detects an external force acting on the robot hand,
A copying jig having a copying member attached to the force sensor and copying the outer surface of the workpiece;
A machining tool attached to the copying jig or the robot hand for machining a workpiece;
A machining control device for controlling the pressing force of the copying jig against the workpiece outer surface of the copying jig;
The copying jig pressing force is set to a value larger than the maximum value of the expected machining reaction force,
There is provided a method of controlling a workpiece machining apparatus, wherein a copying jig is moved along the outer surface of the workpiece while copying the outer surface of the workpiece with the copying member, and the workpiece is machined by the machining tool.

  According to a preferred embodiment of the present invention, the machining control device performs a hybrid control of the force control and a position control for moving the copying jig along a previously taught path.

  Moreover, it is preferable to prepare a plurality of copying jigs or processing tools, sequentially replace them, and perform the processing a plurality of times.

  Further, by preparing a plurality of copying jigs or processing tools, sequentially exchanging them, and performing the above-described processing a plurality of times, it is possible to perform deburring, C chamfering, and round edge processing of the workpiece.

According to the apparatus and method of the present invention described above, an external force (that is, machining reaction force) acting on the robot hand is detected by the force sensor, and the copying jig pressing force against the workpiece outer surface of the copying jig is predicted by the machining control apparatus. Since the force is controlled to a value larger than the maximum value of the machining reaction force, even if a fluctuation in the machining reaction force occurs instantaneously, the maximum value of the machining reaction force does not exceed the pressing force of the copying jig, and the copying jig However, the acceleration in the direction away from the workpiece surface does not occur, and as a result, the displacement of the machining tool is suppressed and a smooth machining surface is obtained.
Even when the rigidity of the robot hand 4 is low, the robot hand and the processing tool attached to the robot hand 4 do not escape (i.e., do not displace) due to the processing reaction force. It is determined by the relationship, and a highly accurate machining surface can be obtained by one machining.
Therefore, when machining a workpiece made of a hard material such as cast iron, machining accuracy can be maintained and damage to the tool can be prevented even if an impact machining reaction force is generated.

It is a schematic diagram which shows the tool pressing force (A) in the control of patent document 1, and the displacement (B) of a tool. It is a block diagram of the industrial robot provided with the workpiece processing apparatus of this invention. It is 1st Embodiment figure of the workpiece processing apparatus of this invention. It is a schematic diagram which shows the tool pressing force (A) and the displacement (B) of a tool by the apparatus of FIG. It is explanatory drawing of the round edge process by the apparatus of FIG. It is another explanatory drawing of the round edge process by the apparatus of FIG. It is 2nd Embodiment figure of the workpiece processing apparatus of this invention. It is a figure of the workpiece processing apparatus of a reference example. It is a schematic diagram which shows the tool pressing force (A) and the displacement (B) of a tool by the apparatus of FIG. It is 3rd Embodiment figure of the workpiece processing apparatus of this invention. It is explanatory drawing of C chamfering process by the apparatus of FIG. It is another explanatory drawing of C chamfering by the apparatus of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 2 is a configuration diagram of an industrial robot provided with the workpiece machining apparatus of the present invention. In this figure, 1 is a workpiece (member to be processed), 2 is a table, 3 is a robot, 4 is a robot hand, 5 is a robot control device, and 10 is a workpiece processing device.

The workpiece 1 is a workpiece to be deburred, chamfered, or rounded by the workpiece machining apparatus 10 and is made of a hard material such as cast iron.
In this example, the workpiece 1 is accurately fixed at a predetermined position on the upper surface of the table 2.

In this example, the robot 3 is an articulated robot, but the present invention is not limited to this, and may be another robot.
The robot control device 5 is a numerical control device, for example, and controls the robot hand 4 to six degrees of freedom (three-dimensional position and rotation about three axes) by a command signal.
The machining control device 20 of the present invention described later is included in the robot control device 5 in this example. Note that the machining control device 20 may be provided separately from the robot control device 5.

FIG. 3 is a first embodiment of the workpiece machining apparatus according to the present invention.
In this figure, a workpiece machining apparatus 10 according to the present invention includes a force sensor 12, a copying jig 14, a machining tool 16, and a machining control apparatus 20.

The force sensor 12 is, for example, a load cell, is attached to the robot hand 4 that can be moved three-dimensionally, and detects an external force acting on the robot hand 4.
The external force detected by the force sensor 12 is preferably an external force having six degrees of freedom (a force in three directions and a torque around three axes), but the present invention is not limited to this, and a copying jig pressing to be described later Other force sensors may be used as long as the force F _all can be detected.

The copying jig 14 is attached to the force sensor 12 and has a copying member 15 that copies the outer surface of the workpiece 1. In this example, the copying member 15 includes a first copying member 15a and a second copying member 15b.
The first copying member 15a and the second copying member 15b are configured to copy the two surfaces 1b and 1c of the workpiece 1 sharing the C surface or the edge 1a to be rounded.
In this example, 1b is the upper surface of the workpiece 1, 1c is the side surface of the workpiece 1, the end surface of the first copying member 15a is in contact with the upper surface 1b perpendicularly and downward, and the end surface of the second copying member 15b is the side surface 1c. It touches vertically and sideways (rightward in the figure). In addition, although it is preferable that the upper surface 1b is a horizontal surface and the side surface 1c is a vertical surface, this invention is not limited to this.
In this example, the first copying member 15 a and the second copying member 15 b are formed integrally with the copying jig 14. However, the present invention is not limited to this and may be separate.

  Further, the copying members 15a and 15b may be configured such that the contact surface is slid and the roller is copied while rolling. In this example, the copying is performed on the two surfaces 1b and 1c. However, the copying member may be omitted in a direction in which the fluctuation of the processing reaction force can be ignored.

The processing tool 16 is attached to the copying jig 14 and processes the workpiece 1.
In this example, the processing tool 16 includes a tool 16a (a cutter in this example) for processing the workpiece 1 and a driving device 16b (a spindle motor in this example) that rotationally drives the tool 16a. In this example, the tool 16a is a conical cutting tool or a grinding tool. However, the tool is not limited to a cutter, and may be another tool (grinding stone or brush).
The driving device 16b can be replaced by an air motor other than the spindle motor.

The machining control device 20 is a control program installed in the robot control device 5, for example, and is a value larger than the maximum value of the expected machining reaction force R for the copying jig pressing force F _all against the workpiece outer surface of the copying jig 14. To force control. That is, from the external force detected by the force sensor 12 (preferably an external force having 6 degrees of freedom), the downward force and the right force are calculated in the figure acting on the first copying member 15a and the second copying member 15b. The robot hand 4 is force-controlled so that the copying jig pressing force F _all of the above becomes a value larger than the maximum value of the expected machining reaction force R.
Note that data necessary for this calculation (for example, dimensions and weights of components of the workpiece machining apparatus 10) are stored in advance in the storage device of the robot control device 5 or the machining control device 20.

Using the apparatus described above, the method of controlling the workpiece machining apparatus of the present invention is as follows:
(A) The copying jig pressing force F _all in each direction is set to a value larger than the maximum value of the expected machining reaction force R,
(B) The copying tool 14 is moved along the outer surface of the workpiece 1 while copying the outer surfaces (the two surfaces 1b and 1c) of the workpiece 1 with the copying members (the first copying member 15a and the second copying member 15b). 16 is used to process the workpiece 1.

  Further, the machining control device 20 performs hybrid control of the above-described force control and position control. In the position control, the copying jig 14 is moved along a previously taught route. Note that part or all of this position control may be performed by the robot controller 5.

  Furthermore, a plurality of copying jigs 14 or processing tools 16 may be prepared and sequentially replaced, and the processing may be performed a plurality of times.

FIG. 4 is a schematic diagram showing a tool pressing force (A) and a tool displacement (B) by the apparatus of FIG. In FIG. 4 (A), the vertical axis represents the scanning tool pressing force F _all, which corresponds to the sum of the processing reaction force R acting on the tool pressing force Ft and the tool.

According to the above-described apparatus and method of the present invention, the external force (that is, the machining reaction force R) acting on the robot hand 4 is detected by the force sensor 12, and the copying jig pressing force F _all (that is, the copying treatment) is detected by the processing control device 20. Since the pressing force of the tool 14 against the workpiece outer surface is controlled to a value larger than the maximum value of the expected machining reaction force R, the machining reaction force R varies instantaneously as shown in FIG. Even if it occurs, the maximum value of the machining reaction force R does not exceed the pressing force of the copying jig (the copying jig pressing force F _all ), and no acceleration in the direction in which the copying jig 14 leaves the workpiece surface is generated. As shown in FIG. 4B, as a result, the displacement of the machining tool is suppressed and a smooth machining surface is obtained.

Even when the rigidity of the robot hand 4 is low, the robot hand 4 and the machining tool 16 attached to the robot hand 4 do not escape (that is, do not move) by the machining reaction force R, so that the machining amount is the copying jig 14 and the machining tool 16. A highly accurate machined surface can be obtained by one machining.
Therefore, when machining a workpiece 1 made of a hard material such as cast iron, even if an impact machining reaction force R occurs, machining accuracy can be maintained and damage to the tool can be prevented.

  As a means for replacing the copying jig 14 or the processing tool 16, it is preferable to prepare a tool changer and a plurality of tools in advance. Further, as means for changing the positional relationship between the tool and the workpiece, changing the shape of the cutter blade, changing the mounting position of the spindle, or the like may be performed.

FIG. 5 is an explanatory diagram of round edge processing for changing the shape of the cutter blade using the apparatus of FIG. 3.
In this figure, reference numeral 18 denotes a tool changer comprising a changer main body 18a and a change member 18b that are detachable from each other. The copying jig 14 described above is attached to the force sensor 12 via the tool changer 18 so that the changer main body 18a and the change member 18b can be separated as necessary, and can be replaced with a different copying jig 14 or a processing tool 16. It has become.
Moreover, in this figure, 16a-1, 16a-2, 16a-3 has shown the some tool 16a from which the shape of a blade differs. Other configurations are the same as those in FIG.

  As shown in this figure, a plurality of (in this example, three) tools 16a (16a-1, 16a-2, 16a-3) are prepared in advance, and these are sequentially exchanged to process the workpiece 1 a plurality of times. By carrying out, round edge processing can be performed.

FIG. 6 is another explanatory view of the round edge processing for changing the spindle mounting position using the apparatus of FIG. In this figure, 14-1, 14-2, and 14-3 show a plurality of copying jigs 14 having different spindle mounting positions. Other configurations are the same as those in FIG.
As shown in this figure, a plurality of (three in this example) copying jigs 14 (14-1, 14-2, 14-3) having different spindle mounting positions are prepared in advance, and these are sequentially replaced, By performing the machining of the workpiece 1 a plurality of times, the round edge machining can be performed.

FIG. 7 is a second embodiment of the workpiece machining apparatus according to the present invention.
In this example, the workpiece machining apparatus 10 of the present invention includes a tool moving device 19 attached to the copying jig 14. In this example, the tool moving device 19 is configured to move the processing tool 16 on a straight line in an oblique direction in the drawing. The moving direction is not limited to a straight line, and may be an arbitrary curve.
The tool moving device 19 is preferably non-back drivable that does not move backward due to the processing reaction force. Such a configuration can be configured by a worm screw, a screw screw, or the like. Other configurations are the same as those in FIG.

  With the above-described configuration, since the tool does not escape due to the machining reaction force, a highly accurate machining surface can be obtained by one machining. Further, by driving the tool moving device 19 in synchronization with the operation of the robot arm and changing the positional relationship between the tool and the copying jig, the machining dimension can be continuously changed along the robot trajectory.

FIG. 8 is a diagram of a workpiece machining apparatus according to a reference example.
In this example, the copying jig 14 includes a spring 17 (for example, a compression spring) that biases the copying member 15 (the first copying member 15a and the second copying member 15b) toward the outer surface (1b, 1c) of the workpiece 1. Have. The spring constant of the spring 17 is set to be large so that the displacement of the copying jig due to the variation of the machining reaction force can be ignored.
Other configurations are the same as those in FIG.

FIG. 9 is a schematic diagram showing a tool pressing force (A) and a tool displacement (B) by the apparatus of FIG.
In FIG. 9A, if the target value of the copying jig pressing force F _all is sufficiently large and the fluctuation of the processing reaction force R does not exceed the pressing force F _all of the copying jig, the copying jig 14 leaves the workpiece surface. Directional acceleration does not occur and the spring constant is large, so that the displacement of the copying jig 14 can be kept small. As a result, the displacement of the tool is suppressed, and a smooth machined surface is obtained.
In addition, by changing the target value of the copying jig pressing force F _all in synchronization with the robot arm trajectory, the tool is displaced as shown in FIG. 9B, and the dimension of the C surface is changed along the trajectory. be able to.
For example, when the spring constant is 500 N / mm and the copying jig is pressed at 100 N, the positional relationship between the copying jig and the cutter is determined so that C0.3 machining of C0.3 can be performed. When the pressing force is set to 250 N in the course of the robot trajectory, C0.6 chamfering is performed. Also, if there is a fluctuation in the machining reaction force of 10 N during machining, the 0.02 mm spring is displaced.

FIG. 10 is a diagram of a third embodiment of the workpiece machining apparatus of the present invention.
In this figure, the first copying member 15a and the second copying member 15b are each composed of a spherical roller. The tool 16a is a spherical cutter in this example.
Other configurations are the same as those in FIG.
In FIG. 10, when spherical rollers are used as the copying members 15 a and 15 b of the copying jig 14, the size and angle of the C surface machining can be adjusted by the pressing angle of the roller against the workpiece 1.

FIG. 11 is an explanatory diagram of C chamfering by the apparatus of FIG.
As shown in FIG. 10, when the jig 14 is rotated along the straight line 6 connecting the centers of the spherical rollers, the depth at which the processing tool 16 (spherical cutter) cuts into the workpiece 1 changes.
However, when a spherical cutter is used, the center of the spherical cutter must not be on the rotation axis 6. Further, as the distance between the center of the spherical cutter and the rotary shaft 6 is larger, the cutting depth is greatly changed with a slight inclination. Thereby, the dimension of C chamfering can be processed into a target dimension.

FIG. 12 is another explanatory view of C chamfering by the apparatus of FIG.
As shown in this figure, when each of the two spherical rollers is slid in contact with the workpiece 1, the angle at which the spherical cutter strikes the workpiece 1 changes. Thereby, the angle of C chamfering can be processed into a target dimension. However, since the depth of cut also changes, it is necessary to readjust the depth of cut by the method described above.
Furthermore, a round edge process can be obtained by combining these processes and performing a plurality of processes by changing the robot trajectory.
In addition to the spherical roller, the copying jig can obtain the same effect by sliding the contact surface processed into a spherical surface to the workpiece surface. Moreover, it is also possible to use curved surfaces other than a spherical surface for both the roller and the cutter.

  In addition, this invention is not limited to embodiment mentioned above, is shown by description of a claim, and also includes all the changes within the meaning and range equivalent to description of a claim.

1 workpiece (workpiece), 1a edge 1b top surface, 1c side surface, 2 table, 3 robot, 4 robot hand, 5 robot control device, 6 straight line (rotating axis), 10 workpiece processing device, 12 force sensor 14 (14- 1, 14-2, 14-3) copying jig, 15 copying member, 15a first copying member, 15b second copying member, 16 machining tool, 16a (16a-1, 16a-2, 16a-3) tool ( Cutter), 16b drive device (spindle motor), 17 spring (for example, compression spring), 18 tool changer, 18a changer body, 18b change member, 19 tool moving device, 20 machining control device

Claims (5)

A force sensor that is attached to a movable robot hand that covers six degrees of freedom in space and detects an external force acting on the robot hand;
A copying jig having a copying member attached to the force sensor and copying the outer surface of the workpiece;
A machining tool attached to the copying jig or the robot hand for machining a workpiece;
Based on the external force detected by the force sensor, a force acting on the copying member is calculated, and the copying jig pressing force against the workpiece outer surface of the copying jig is larger than the maximum value of the expected machining reaction force. And a machining control device for force control,
The copying member is adapted to copy the outer surface of the workpiece at a position away from the processing position of the workpiece by the processing tool,
The machining control device performs a hybrid control of the force control and a position control for moving the copying jig along a path taught in advance, thereby copying the copying jig while copying the outer surface of the workpiece with the copying member. A workpiece machining apparatus, wherein the workpiece machining apparatus moves along an outer surface of the workpiece, processes the workpiece with the machining tool, and prevents the robot hand and the machining tool from being displaced by a machining reaction force. The copying member is composed of a first copying member and a second copying member that copy the C surface or the two surfaces of the workpiece sharing the edge to be rounded,
The processing control device calculates a force acting on the first copying member in the first direction and a force acting on the second copying member in the second direction based on the external force detected by the force sensor, 2. The force control of the scanning jig pressing force in the direction and the scanning jig pressing force in the second direction is controlled to a value larger than the maximum value of the expected machining reaction force. Work processing equipment.   The machining control device calculates a force acting on the copying member based on an external force detected by the force sensor, and controls the copying jig pressing force to a value larger than the maximum value, thereby performing an impact. 3. The workpiece machining apparatus according to claim 1, wherein the maximum value of the machining reaction force does not exceed the copying jig pressing force even when a general machining reaction force is generated.   4. The workpiece machining apparatus according to claim 1, further comprising a tool moving device that is attached to the copying jig and moves the machining tool on a straight line or a curved line. A force sensor that is attached to a movable robot hand that covers six degrees of freedom in space and detects an external force acting on the robot hand;
A copying jig having a copying member attached to the force sensor and copying the outer surface of the workpiece;
A machining tool attached to the copying jig or the robot hand for machining a workpiece;
Based on the external force detected by the force sensor, a force acting on the copying member is calculated, and the copying jig pressing force against the workpiece outer surface of the copying jig is larger than the maximum value of the expected machining reaction force. And a processing control device for force control
The copying member is adapted to copy the outer surface of the workpiece at a position away from the processing position of the workpiece by the processing tool,
The machining control device performs hybrid control of the force control and position control for moving the copying jig along a previously taught path, so that the copying jig can be used while copying the outer surface of the workpiece with the copying member. A control method for a workpiece machining apparatus, characterized in that the workpiece moves along an outer surface of the workpiece, the workpiece is machined by the machining tool, and the robot hand and the machining tool are not displaced by a machining reaction force.

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