JP2702127B2 - Copy grinding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a NC head in which a grinding wheel is rotatably held at a tip thereof so that the grinding wheel follows a processing surface of a workpiece to perform NC grinding. It relates to a grinding device. (Prior art) For example, in the processing of plastic molds, manual grinding by a skilled worker is indispensable for finish grinding and polishing of a machined surface of a mold pre-processed by milling or electric discharge machining. However, in recent years, methods for automating this operation have been considered. Conventionally, as an automatic grinding apparatus of this type, as shown in FIG. 8, for example, a spindle head 3 rotatably supporting a rotating spindle 2 of a grindstone 1 is supported by a saddle 4 which is fed and moved in the Y-axis and Z-axis directions. The rotation axis of the rotating main shaft is fixed in the Z-axis direction. Then, while the rotary spindle 2 is rotationally driven by an air turbine or the like, the saddle 4 is set via the NC device 5 so that the pressing force F in the axial direction of the rotary spindle 2 against the work surface Wa is fixed by the pressure sensor S, for example. Automatically controls the Z-axis direction feed servomotor 6 and feeds the rotary spindle 2 in the axial direction, that is, in the Z-axis direction. A constant pressure scanning grinding method in which grinding is performed in accordance with the W processing surface Wa is employed. (Problems to be Solved by the Invention) In such a conventional method, however, the spindle head 3 is fixed to the saddle 4 in a constant posture in the Z-axis direction, so that a three-dimensionally complicated free-form surface is required. Machining surface of shaped workpiece
In the case of performing copy grinding on Wa, for example, a substantially radial copy grinding wheel 1 as shown in FIG.
When grinding the point A and when grinding the point B, the grinding portion on the grindstone 1 that contacts the processing surface Wa is different. That is, as shown in FIGS. 9 (a) and 9 (b), the contact angle θ between the grindstone 1 and the work surface is different between point A and point B as θa> θb. For this reason, when grinding is performed by rotating the rotating spindle 2 at a constant speed, the grinding speed at which the grindstone 1 grinds the workpiece W differs between the point A and the point B. Various grinding stones are provided with an optimum grinding speed specific to the grinding stone as an optimal processing condition according to required quality, work material, etc. However, in the conventional apparatus, the contact angle θ with the work W changes, and The optimum grinding speed cannot be maintained. For example, the grinding speed is too fast, which causes an abnormal overload on the grinding wheel 1 to shorten the life of the grinding wheel. On the contrary, the grinding speed is too slow to reduce the grinding efficiency. There has been a problem that grinding cannot be performed. Therefore, the present invention detects the inclination of the surface of the workpiece to be machined, and controls the angle of the grinding wheel axis so that the contact angle between the grinding wheel and the workpiece surface is always constant. An object of the present invention is to solve the above-mentioned problem by reliably maintaining the optimum grinding speed of the grindstone while keeping the part constant. (Means for Solving the Problems) In view of the above, the present invention provides a grinding head which rotatably holds a grinding wheel at the tip thereof, which is configured so that the inclination of the grinding wheel axis can be adjusted in two directions orthogonal to each other, Contact between the grindstone and the surface of the work to be processed by controlling the inclination based on the measured values of the two distance sensors provided at the tip of the head so that the angle between the grindstone axis and the surface of the work to be processed is always constant. The angle is always constant, and the grinding area on the grinding wheel is also fixed to maintain the optimum grinding speed unique to the grinding wheel, so that stable and efficient profile grinding can be performed under optimal processing conditions. Things. That is, the present invention relates to a profile grinding apparatus that performs a grinding process in which a grinding head having a grinding wheel rotatably held at its tip is rotatably controlled in three axial directions of X, Y, and Z to follow a workpiece surface. A grinding wheel holder rotatably supporting the grinding wheel of the grinding wheel, and a first support mechanism for supporting the grinding wheel holder in a first circular motion centering on the grinding wheel tip side. And a first arc drive motor for driving the first arc motion, and a second arc motion centering on a tip end side of the grindstone in a direction orthogonal to the first arc motion with the grinding wheel holder. A second support mechanism, and a second arc drive motor for driving the second arc movement, wherein at least one of the support mechanisms is connected to the tool holder via the idle gear by the arc drive motor on a base side. Centered around At the same time as the idle gear is engaged with the linear rack member, the center of rotation of the grindstone holder is moved together with the gear center of the idle gear in the linear direction by the amount that the tip position of the grindstone holder moves with the rotation. And a first distance sensor for measuring the distance to the workpiece and a second distance sensor at an angular position different from the first distance sensor are respectively fixed at predetermined positions on the grinding wheel holder. The measured value from the first distance sensor is a first preset value.
The first arc drive motor is driven and controlled so as to match the set value of the second arc, and at the same time, the second arc is set so that the measured value from the second distance sensor matches the second set value set in advance. The drive motor is driven and controlled, so that profile grinding is performed while always holding the grinding wheel at a predetermined angle on the workpiece surface to be machined. (Example) Hereinafter, a specific configuration of the present invention will be described. FIG. 1 is a front view showing a profile grinding apparatus of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a view showing a first circular motion in a first support mechanism, and FIG. 4 is a second support. FIG. 5 is a diagram showing a second circular motion in the mechanism, FIG. 5 is a perspective view showing a relationship between two distance sensors and a work surface, and FIG. 6 is a relationship between the distance sensor and a work surface on a first plane. , FIG. 7 is a control circuit diagram of the first and second arc movements, FIG. 8 is a front view showing a conventional apparatus, and FIGS. 9 (a) and (b) explain a conventional grinding state. FIG. First, in FIGS. 1 and 2, the apparatus as a whole is a main body 7, a table guide table 8 fixed to the main body 7, and a sliding movement along the table guide table 8 in the X-axis direction perpendicular to the paper surface. Slide table 9, and Y formed integrally with the main body 7 above the table 9.
An axial guide surface 10, a first saddle 11 guided and slid along the guide surface 10 in the Y-axis direction, a Z-axis guide surface 12 integrally formed with the first saddle 11, and the guide surface 12. A second saddle 13 guided and slid in the Z-axis direction, which is a direction of contact and separation with the workpiece W, along with a grinding head 14 described later mounted on the second saddle 13, and the slide table 9 and the first
Consisting of servo motors 15, 16, and 17 for feeding and driving the saddle 11 and the second saddle 13, respectively, and by simultaneously controlling these servo motors 15, 16, and 17 by an NC device, a constant shape following the shape of the work surface Wa. Is controlled at the combined feed speed of. The second saddle 13 has the servo motor 17 at the upper end,
A feed screw 18 connected to the motor shaft of the servo motor 17 is screwed with a nut portion 19 fixed to the first saddle 11, and the feed screw 18 is rotated via the servo motor 17 to move in the Z-axis direction. It is driven to feed vertically. The grinding head 14 is provided with a rotating spindle (not shown) which is rotationally driven by, for example, an air turbine or the like, and is always elastically held at a constant pressure in the axial direction with Z-axis control by a pressure sensor or the like. A grinding wheel holder 20 rotatably supporting the grinding wheel axis C of the grinding wheel 1 at the tip through a shaft.
And a first support mechanism 21 and a second support mechanism 21 for supporting the grindstone holder 20 so as to enable a first circular motion and a second circular motion.
Of the support mechanism 22, and provided on those support mechanisms 21, 22;
First arc drive motor 23 for driving each arc motion
And a second arc drive motor 24. The grinding wheel 1 is formed in a rotating body having a substantially spherical grinding wheel surface at the tip, and has a shape capable of performing profile grinding on a free-form surface Wa. The first support mechanism 21 supports the grindstone holder 20 so as to be able to perform a first circular motion about a grindstone tip side substantially on a first plane including, for example, a Z axis and a Y axis. On the other hand, the second support mechanism 22 supports the grindstone holder 20 so as to be capable of performing a second circular motion about the grindstone tip side substantially on a second plane including, for example, the grindstone axis C and the X axis. It is. Next, the first support mechanism 21 will be described in detail with reference to FIG. At the lower end of the second saddle 13, the above-mentioned circular motion guide support portion is provided.
25 are provided integrally. Guide surface of this guide support 25
25a forms an arc with a certain point E on the grinding wheel 1 as the center, and an arc-shaped rack member 26 is formed on the guide surface 25a.
Are slidably guided in an arc direction. As shown in FIG. 2, a rack 27 is formed on the circular arc surface of the upper surface of the rack member 26, and is attached to a motor shaft of a servo motor 23 as a first circular drive motor provided on the circular guide support portion 25 side. A pinion 28 meshes with the rack 27, and transmits the rotation of the servomotor 23 to the second support mechanism 22 via the pinion 28 and the rack 27 as a first circular motion. The rack member 26 supports the second support mechanism 22 and the grindstone holder 20. The rack member 26 and the second support mechanism 22 and the grindstone holder 20 are connected to the first support mechanism 22 as shown in FIG. Are moved circularly right and left around the point E on the distal end side substantially on the plane of FIG. The point E, which is the center of the circular motion, may be set at any point on the surface of the grindstone or inside or outside the grindstone 1, but the circular motion can be performed along the spherical shape of the surface of the grindstone 1 as much as possible. It is optimal to determine one point where the displacement of the processing point on the workpiece processing surface Wa due to the movement is small. Next, the second support mechanism 22 will be described in detail with reference to FIG. A return direction guide support portion 29 is integrally provided to protrude rearward from an intermediate portion of the rack member 26. On this guide support portion 29, a portal bracket 30 is slidably guided and supported in the front-rear direction, that is, in the X-axis direction. At the lower end of the bracket 30, the grindstone holder 20 is pivotally supported along the second plane via a support pin 31, and in the middle of the bracket 30, An idle gear integrally having gears 32 and 33 is rotatably supported via a shaft 34 along the second plane. Below the one gear 33, the grinding wheel holder
A fan-shaped gear 35 centered on the support pin 31 having only a circumferential portion formed with teeth on the upper portion of 20 is integrally mounted, and the teeth are meshed with the gear 33. Above the gear 33, a rack 36 long in the X-axis direction is formed integrally with the lower surface of the return-direction guide support 29, and meshes with the gear 33. Further, a servomotor 24 as the second arc drive motor is mounted on one upper side of the bracket 30.
A pinion 37 attached to the motor shaft of the servo motor 24 meshes with the gear 32 to rotate the servo motor 24.
The rotation in the same direction is transmitted to the grindstone holder 20 via the gear 37, the gear 32, the gear 33, and the gear 35. At the same time, as shown in FIG.
And the bracket 30 is shifted in the front-rear direction while holding the grindstone holder 20. That is, as shown in FIG. 4, the tilt angle of the grinding wheel axis C is adjusted by swinging the grinding wheel holder 20 around the support pin 31. At the same time, the tip of the grindstone 1 is displaced from the original position by the swing, so that the movement is returned by the movement of the bracket 30 in the X-axis direction. On the other hand, the shift in the Z-axis direction can be corrected by the Z-axis direction control by the pressure sensor. Accordingly, while maintaining the position of the tip of the grinding wheel, a change is made to the angle of the grinding wheel axis C, and a second circular motion is performed in which the grinding wheel holder 20 circularly moves about the point E on the second plane substantially at the center. . Further, two distance sensors 38 and 39 are provided at different angular positions on the outer peripheral wall of the grinding wheel holder 20. As shown in FIGS. 5 and 6, the first distance sensor 38 is mounted at a predetermined position P which is separated from the grinding wheel axis C by a predetermined distance mp in the Y-axis direction, for example, and is provided between the point P and the workpiece processing surface Wa. The second distance sensor 39 is mounted at a predetermined position Q separated from the grinding wheel axis C by, for example, a predetermined distance mq in the X-axis direction, and measures a distance lq between the point Q and the workpiece processing surface Wa. Is what you do. As the distance sensors 38 and 39, for example, a contact type sensor such as a linear potentiometer or an electric transformer may be used, or a non-contact type sensor such as an optical distance sensor or a capacitance type distance sensor may be used. When the distances lp and lq between the respective workpiece processing surfaces Wa are measured by the two distance sensors 38 and 39, the coordinate data of the contact point E between the grindstone 1 and the processing surface Wa and the coordinates 3 on the workpiece processing surface Wa are measured. The coordinates of the point can be determined, whereby the inclination of the workpiece processing surface Wa can be easily known. For example, as shown in FIG. 6, the contact angle theta comprising the normal at the contact point of the C-axis and the workpiece work surface Wa of the grinding wheel 1 is set to theta ₁ based on the optimum processing conditions. Distance lp ₁ between the workpiece processed surface Wa from fixed sensor position P at this time is Sadamari the geometric distance lq ₁ between the workpiece processed surface Wa from fixed sensor position Q as well is determined. Then, as shown in the control circuit diagram of Figure 7, the lp ₁
Is set in the setting device 40 as a first setting value, and lq ₁ is previously set in the setting device 41 as a second setting value. During the processing, the distances lp and lq between the workpiece processing surface Wa and the sensors are measured by the sensors 38 and 39. At this time, the difference between the measured value and the set value via the respective comparators 42 and 43, that is, lp−, is set so that lp = lp ₁ and lq = lq ₁ respectively.
The values of lp ₁ and lq−lq _{1 correspond} to the first and second servo motors 2.
3 and 24 are sent to the servo amplifiers 44 and 45, respectively. 46, 4
7 is a tacho generator for each of the servomotors 23 and 24. In this way, when the first servo motor 23 with a signal lp-lp ₁ is rotated, the rack member 26 which holds the second support mechanism 22 and the grindstone holder 20, the point a first upper plane E is carried out for the first circular motion that substantially centered, is controlled such that the contact angle between the workpiece processed surface Wa of the grinding wheel 1 on the first plane theta is always theta ₁ and constant. At the same time, when the second servo motor 24 is driven to rotate by the signal of lq−lq ₁ , the grindstone holder 20 is centered on the second plane at the point E on the second plane via the second support mechanism 22. performs second arcuate motion is controlled such that the contact angle between the workpiece processed surface Wa of the grinding wheel 1 on the second plane theta is always theta ₁ and constant. As described above, since the contact angle control in two directions orthogonal to each other is performed by the two distance sensors 38 and 39, no matter which direction the grinding feed direction of the grindstone 1 along the work W surface is directed, Can be reliably detected by the two distance sensors 38 and 39, even if the workpiece processing surface Wa has a curved surface that is twisted in an indeterminate direction, and based on the measured values, the grinding wheel axis C By performing angle control in two directions simultaneously, a constant contact angle θ with respect to the work surface Wa is always constant.
₁ is kept. Note that the two directions of the sensor mounting position are not limited to those that match the X and Y directions as in the present embodiment, and may be set to any direction or angle that does not match the X and Y directions. In addition, the first support mechanism 21 can also be configured to rotate the grindstone holder 20 via the idle gear and return the base side to the straight line in the Y direction, like the second support mechanism 22. Also, the second support mechanism 22, like the first support mechanism 21, causes the arc-shaped rack member along the trajectory of the second arc motion to mesh with the drive-side pinion with respect to the arc guide support portion. It is also possible to use a mechanism having a different structure. Further, instead of each gear, another transmission structure such as a worm gear, a belt transmission, or a link mechanism can be used. (Effects of the Invention) According to the present invention, in addition to the X-, Y-, and Z-axis feed control during the profile grinding, the grinding wheel holder of the grinding head is substantially centered on a point defined on the tip side with respect to the saddle. Two mutually orthogonal
Direction of circular motion is possible, two distance sensors attached to the grindstone holder constantly measure the distance to the work surface, and drive each circular motion so that the measured value matches the preset value. Since the control is performed, the grindstone axis is tilted in the above two directions, so that the contact angle between the surface of the workpiece to be machined and the grindstone is always kept constant. That is, regardless of the direction in which the grinding feed direction of the grindstone along the workpiece surface is oriented, or the workpiece processing surface has a curved surface that is twisted in an indeterminate direction, the inclination of the workpiece processing surface with respect to the grinding wheel is equal to the two distances. Can be reliably detected by the sensor,
By simultaneously controlling the angles of the grindstone shafts in two directions based on the measured values, a constant contact angle is always maintained with the work surface. In this way, it is possible to easily grind the work surface at a fixed part of the grindstone easily even on a work surface with a complicated free-form surface shape, so that the optimum grinding speed unique to the grindstone can be maintained. it can. For this reason, it is possible to perform the profile grinding in which the finished surface is very uniform and stable. Further, in the present invention, since at least one of the circular motions is performed by a combination of linear movement and rotation, the radius of curvature of the rotation guide portion can be reduced, and a large circular arc can be formed for each of the two circular motions. There is no need to provide a guide member, and the whole can be configured to be narrow with small members. Interference with the work can be prevented, and the operating angle width of the circular motion can be increased. Therefore, it is possible to easily follow a workpiece surface having a complicated free-form surface shape, and to grind the workpiece surface at a fixed portion of the grindstone.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing a profile grinding apparatus of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a view showing a first circular motion in a first support mechanism, FIG. FIG. 4 shows the second support mechanism.
FIG. 5 is a perspective view showing the relationship between two distance sensors and the work surface, FIG. 6 is a diagram showing the relationship between the distance sensor and the work surface on the first plane, FIG. 7 shows the first
FIG. 8 is a front view showing a conventional apparatus, and FIGS. 9 (a) and 9 (b) are views for explaining a conventional grinding state. 1 ... grinding wheel, 13 ... 2nd saddle as saddle,
14 grinding head, 20 grinding wheel holder, 21 first support mechanism, 22 second support mechanism, 23 servo motor as first circular drive motor, 24 second Servo motor as an arc drive motor, 31 ... Support pin as a rotation center, 33 ... Idle gear, 34 ... Axle as a gear center, 36 ... Rack as a linear rack member, 38 ...
A first distance sensor, 39... A second distance sensor, 40... A setter for setting a first set value, 41... A setter for setting a second setter, C... , Q... Predetermined position, W
……work.

Claims (1)

(57) [Claims] In a scanning grinding apparatus that feeds a grinding head having a grinding wheel rotatably at its tip in a three-axis direction of X, Y, and Z to perform grinding according to a processing surface of a work, the grinding head is used as the grinding head. A grindstone holder rotatably supporting a grindstone shaft of the grinding grindstone, a first support mechanism for supporting the grindstone holder so as to enable a first arc movement centered on the grindstone tip side, A first arc drive motor for driving an arc motion, a second support mechanism for allowing the grindstone holder to perform a second arc motion centering on a tip end side of the grindstone in a direction orthogonal to the first arc motion; A second arc drive motor for driving the second arc motion, and the at least one support mechanism is configured to rotate the tool holder around the base side through the idle gear via the idle gear by the arc drive motor. Same as give The idle gear is engaged with the linear rack member so that the center of rotation of the grindstone holder together with the gear center of the idle gear performs a return operation in the linear direction by an amount corresponding to the movement of the tip end position of the grindstone holder with the rotation, and A first distance sensor for measuring a distance to a workpiece, and a second distance sensor fixed at a predetermined position at an angular position different from the first distance sensor, on the whetstone holder; The drive control of the first arc drive motor is performed so that the measured value from the sensor coincides with the first set value set in advance, and at the same time, the measured value from the measured value from the second distance sensor is set in advance. The second arc drive motor is driven and controlled so as to coincide with the second set value, and the grinding wheel is always held at a predetermined angle with respect to the work surface to be machined. Reluctant to copying grinding copying grinding apparatus and said.