JP2014157534A - Method for measuring moving speed of work table of numerically controlled machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more accurately measure a moving speed of a work table in grinding.SOLUTION: One dock 5 with a narrow width (L) is installed on the front of a work table 2 or a magnetic chuck 3 in the vicinity of a working point where a workpiece w and a grinding wheel 4 abut on each other, one on-off sensor 6 is attached to a fixed side machine frame, and a time (t) from sensing (on) of a left end or a right end of the dock by the on-off sensor 6 up to no sensing (off) by the on-off sensor 6 after passage of the another end of the dock 5 further continuing movement is measured by a timer to calculate a table moving speed (=[L/t]m/min).

Description

  In the present invention, when a workpiece (workpiece) placed on a work table that reciprocates in the left-right direction is ground with a grinding wheel, machining is performed according to the machining programming conditions stored in the memory unit of the numerical controller. The present invention relates to a method for measuring a moving speed of a work table used in a numerical control (NC) machine tool using a dock and an on-off sensor.

When machining multiple workpieces of the same type, if the physical properties (surface roughness, gloss, straightness, dimensions, etc.) of the previously machined workpiece are within the acceptable product threshold, machining of the new workpiece to be machined next The next workpiece is machined without changing the conditions, and the physical properties (surface roughness, gloss, straightness, dimensions, etc.) of the machined workpiece after the tool (for example, grinding wheel) is worn out are the threshold values for acceptable products. If the product is rejected and rejected, a numerically controlled machine tool is used to machine the next workpiece, replacing it with the optimum machining conditions for the previously machined workpiece recorded in the recording unit of the numerical controller. ing. For example, Okamoto Machine Tool Mfg. Co., Ltd. has an ultra-precision micro-profile grinding machine “UPZ210LiII” (trade name) (see Non-Patent Document 1) and a precision surface grinding machine “PSG-iQ” (trade name) (see Non-Patent Document 2). , CNC ultra precision forming grinding machine "UPZ series"
(Product name) (see Non-Patent Document 3) is manufactured and sold.

  Japanese Patent Laying-Open No. 2011-95879 (Patent Document 1) proposes a correction grinding method using a correction grinding program stored in a memory unit of such a numerically controlled grinding apparatus. Japanese Patent Laying-Open No. 2010-97399 (Patent Document 2) discloses a machine coordinate system in a numerical control apparatus for a machine tool having at least a linear axis and a rotary axis as drive axes capable of relatively moving a workpiece and a tool. An NC data storage unit for storing machine coordinate system NC data including a linear axis coordinate and a rotation axis angle in the system, and a command feed speed of a machining point of the tool with respect to the workpiece, and between the workpiece and the tool When the relative orientation changes, according to the distance between the rotation center of the workpiece and / or the tool and the machining point of the tool with respect to the workpiece, obtained based on the machine coordinate system NC data, A numerical control device for a machine tool including a speed correcting unit for correcting the moving speed of each drive shaft is proposed.

  As the machining conditions, the work table left / right moving speed, or the input (in-put) of the stroke (table reversal) count related to the recording part is also the work type, work size, tool lowering speed, tool rotation speed, tool It is an element of important machining conditions including machining conditions such as dressing speed, column or saddle back-and-forth feed speed. The measurement of the lateral movement speed of the work table depends on the table reversal positioning means in the conventional NC machine tool. Therefore, the table overrun reversal distance is not taken into account in the calculation of the horizontal movement speed of the work table.

  Japanese Patent Laid-Open No. 9-85594 (Patent Document 3) reciprocates a work table on which a work to be processed is placed and fixed, and intermittently cuts a grindstone provided on a rotatable spindle every time the work table is reversed. In the grinding method in which the workpiece is ground by being fed, the inversion of the work table is detected by a sensor, and the spindle is moved at a feed speed synchronized with the movement speed of the work table based on the detected signal. Then, a grinding method characterized in that intermittent cutting is given to the grindstone is proposed.

  Japanese Patent Laid-Open No. 10-138132 (Patent Document 4) discloses that a table on which a workpiece is placed is reciprocated horizontally in a predetermined section by a hydraulic device, and a grindstone and the workpiece are moved by a servo motor at the end of the section. In a control device for a surface grinder that grinds a workpiece by moving it in the front-rear direction at a movement distance M and a movement speed v specified in advance, the table reciprocation time T is measured at the start of machining. When T <2M / v, a numerical controller for a surface grinding machine is disclosed, wherein the moving distance M is replaced with a moving distance v · T / 2.

Japanese Unexamined Patent Application Publication No. 2009-90415 (Patent Document 5) discloses a reciprocal reversal of a machine tool table that inverts the table by transmitting it to a moving member that changes the rotational motion of a three-phase induction motor fixed to the bottom surface of the machine tool to a linear motion. It is a moving method that uses an electronic control unit, a three-phase induction motor, an inverter, an encoder, a limit switch, and a dock, and in advance a right limit switch that conforms to the table moving speed (V _t ) and stroke width (L _s ). When the dog under the table comes into contact, the table decelerates, the current of the three-phase induction motor becomes 0 mA, the table position becomes the left reverse position, the deceleration time (t _d ) according to the deceleration, and the table reverses to the left and accelerates It is determined acceleration time the dog under the table corresponding to the acceleration in contact with the left limit switch a (t _a) experience measurement, the table moves Speed (V _T), stroke width (L _s), the machine tool table inversion table that describes the deceleration time (t _d) and acceleration time (t _a) in the reference, adapted to the work to be machined from the electronic control unit Teach-in the table moving speed (V _t ), stroke width (L _s ), deceleration time (t _d ) and acceleration time (t _a ), and then press the table movement start switch to perform electronic control An electrical signal command is transmitted from the device to the inverter, and the received inverter transmits the electrical signal of the rotational speed of the three-phase induction motor to the three-phase induction motor at the time of table movement and reversal to the three-phase induction motor. Disclosed is a method for reversing and reversing a machine tool table, wherein the table is accelerated, moved at a constant speed, decelerated, and reversed by changing the number of rotations. That.

Japanese Patent Application Laid-Open No. 2008-22215 (Patent Document 6) discloses that a grinding wheel is moved up and down, a reciprocating movement of a work table on which a chuck for fixing a work is placed, and a relative direction of a grinding wheel. In a method of grinding a workpiece surface by lowering a grinding wheel rotating with respect to the workpiece surface to the workpiece surface by using a grinding device that grinds the workpiece surface by movement, the grinding wheel and the workpiece When the vibration sensor head installed on the chuck surface near the workpiece detects the vibration signal generated from the interference area, and the value (E _i ) of the vibration signal is higher than the preset trigger value (E ₀ ) of the vibration signal When the work table is advanced in one direction and the vibration signal value (E _i ) reaches or falls below a preset vibration signal trigger value (E ₀ ), the work table drive means Disclosed is a workpiece grinding method characterized by sending an inversion signal to invert a work table.

Japanese Patent Laid-Open No. 2006-82158 (Patent Document 7) discloses that a grinding wheel is moved up and down, a reciprocating movement of a work table on which a magnetic chuck for fixing a work is placed, and a relative direction of a grinding wheel. In a method of grinding a workpiece surface by lowering a grinding wheel rotating with respect to the workpiece surface to the workpiece surface and grinding the workpiece surface using a grinding apparatus that grinds the workpiece surface by a gentle movement, the grinding wheel and the workpiece When a vibration sensor head installed on the chuck surface near the workpiece detects a vibration signal generated from the interference area of the workpiece, and the value (E _i ) of the vibration signal is higher than a preset trigger value (E ₀ ) of the vibration signal Advances the work table in one direction, and when the vibration signal value (E _i ) reaches a preset vibration signal trigger value (E ₀ ) or less, the work table drive means A workpiece grinding method is disclosed in which an inversion signal is sent to the workpiece table to invert the workpiece table.

Okamoto Machine Tool Manufacturing's distribution catalog, “Ultra-Precision Micro Profile Grinding Machines—UPZ210LiII, UPZ210LiII DOUBLE EAGLE, UPG310Li”, 2-3 pages, September 2011, issued 3,000 copies. Okamoto Machine Tool Manufacturing's distribution catalog, “Precision Surface Grinding Machine-PSG-SA, SA-iQ Series, PSG-CA, CA-iQ Series”, created in June 2012, 3,000 copies issued. Okamoto Machine Tool Manufacturing's distribution catalog, “CNC Super Precision Surface Grinding Machine-UPZ-SERIES”, created in January 2012, issued 1,000 copies.

JP 2011-95879 A JP 2010-97399 A Japanese Patent Laid-Open No. 9-85594 JP-A-10-138132 JP 2009-90415 A JP 2008-22215 A JP 2006-82158 A

  A method for determining the table reversal time using two docks, two proximity sensors and a timer described in Patent Document 3, and a table reversal time using two docks, two limit switches and an encoder described in Patent Document 5 The table moving speed is calculated by dividing the distance (m) between the two dogs by the time (minutes) the table passes between the two proximity sensors or limit switches. However, in the actual work table reversal, the work table often overruns the limit switch position, and the actual table movement speed value of the table movement speed at the time of workpiece grinding is slightly different from the actual table movement speed value. Is the actual situation. Therefore, there is a tendency in the machining industry that the threshold value of the physical properties of the accepted workpiece that has been ground is slightly widened, and there is a slight variation in the physical properties among the many processed workpieces obtained.

  The method of determining the table reversal position disclosed in Patent Document 7 using the vibration sensor head installed on the chuck surface near the workpiece has an advantage that it is not necessary to input the table moving speed of the processing conditions to the storage unit of the numerical controller. The accuracy of vibration sound sensitivity of the vibration sensor heads currently on the market is low, picking up the vibration noise when the workpiece and grinding wheel collide and the vibration noise of the grinding fluid blown on the work point where the workpiece and grinding wheel abut. Therefore, the method for determining the table inversion position has a drawback that the accuracy is lower than the method for determining the table inversion position described in Patent Document 5 and Patent Document 6. In other words, it is necessary to add a sensing program with a filter that eliminates the vibration sound that the grinding fluid collides with.

  The present inventors measure a value that is as close as possible to the table moving speed at the time of workpiece processing in order to meet the demand for the provision of a numerically controlled machine tool that can obtain a workpiece with further ultra-precision physical properties in the machine tool industry. As a method, a single dock with a width (L) narrower than the left and right width of the work is installed on the work table or magnetic chuck surface near the work point where the work and the grinding wheel come into contact with each other. Install an on-off sensor until the on-off sensor no longer senses the reverse end of the dock that continues to move after the on-off sensor senses the left or right edge of the dock (on) It was conceived that the table moving speed (L / t) m / min closer to the actual table moving speed can be calculated if the time (t) is measured with a timer.

  According to the first aspect of the present invention, when a workpiece placed on a workpiece table that reciprocates in the left-right direction is ground with a grinding wheel, the workpiece is machined according to the machining programming machining conditions stored in the memory unit of the numerical controller. In the method for measuring the moving speed of a work table used in a numerically controlled machine tool, one dog having a narrow width (L) is installed on the work table or magnetic chuck surface near the work point where the work and the grinding wheel abut, On the other hand, one on-off sensor is attached to the fixed-side machine frame, and when this on-off sensor senses the left or right edge of the dock (on), the reverse end of the dock that continues to move further moves to the on- The work table is characterized in that the time (t) until the off sensor is no longer detected (off) is measured by a timer, and the table moving speed = (L / t) m / min is calculated. In the method of measuring the movement speed.

  Compared with the conventional method for measuring the work table speed including overrun, in the method of the present invention, the table moving distance (L) measurement is shortened to a dock width (L) equal to or smaller than the right and left width of the work. Thus, a moving speed closer to reality can be calculated, and a ground workpiece that has been subjected to precision grinding with more uniform physical properties can be obtained. Moreover, since it can measure with one dock and one proximity sensor without using a pair of limit switches or a pair of docks, the cost of the measuring apparatus can be reduced.

FIG. 1 is a partial view at a standby position of a numerically controlled machine tool machine equipped with a table moving speed detection device, FIG. 1A is a partial plan view, and FIG. 1B is a partial front view. 2 is a partial view of the numerically controlled machine tool machine tool shown in FIG. 1, FIG. 2A is a partial front view with a dock, and FIG. 2B is a partial perspective view showing a proximity sensor mounting portion.

  A numerically controlled machine tool machine tool 1 shown in FIGS. 1 to 2 includes a work table 2 that can reciprocate in a horizontal direction on a machine frame (base) F, a magnetic chuck 3 fixed to the upper surface of the work table, and the magnetic chuck. Placed workpiece (workpiece) w, grinding wheel 4 that can be rotated on the grinding wheel shaft, and can be moved up and down, and partial position near the workpiece w on the front surface of the magnetic chuck 3 (the workpiece center and the dock width center are close to each other) (On the vertical plane passing through the center of the sensor) The dock 5 with a left and right width of 50 mm provided to be movable in the left and right directions on the dock rail 5a, one on-off type made by OMRON on the fixed machine frame A magnetic field sensor “E2E-X2D1-U” (trade name) 6 is attached, and when the magnetic field sensor 6 senses the passage of the left end or the right end of the dock (on), the reverse end of the dock that continues moving further passes through. The time (t) until the magnetic field sensor 6 is no longer sensed (off) is measured by the timer of the clock circuit attached to the numerical control device, recorded in the recording unit, and the table moving speed = (L / t) m / min is calculated and transmitted to the storage unit.

  As the on-off sensor 6, a magnetic field sensor and an optical sensor are commercially available. As the on-off type magnetic field sensor, the above-mentioned “E2E-X2D1-U” (trade name) manufactured by OMRON Corporation, manufactured by Keyence Corporation "EV-108M" (product name), Panasonic's "GX-8MW" (product name), as the on-off light sensor, OMRON's "E3Z-R61" (product name), manufactured by Keyence Corporation "EV-108M" (trade name) and "PR-MB15N3" (trade name) manufactured by Panasonic can be purchased from the market. The on-off electrical signal of the on-off sensor 6 is transmitted to the recording unit of the numerical controller (not shown) via the telegraph cable 6a, and then the on-off time (t) is displayed by the timer. When the dock rail 5a is replaced with a new type of workpiece w having a changed size, the dock 6 moves on the dock rail 5a according to the machining conditions of the machining program and comes close to the workpiece w on the front surface of the magnetic chuck 3. Used to reach the partial position (on the vertical plane passing through the workpiece center and the dock width center).

  Prior to starting grinding of the workpiece w using the numerically controlled machine tool 1, the dock position is fixed. Next, select the machining program number disclosed on the display screen of the numerical control device, check whether the previously displayed machining conditions are acceptable, and if there are inconvenient machining conditions, the machining condition display field back will be displayed. Since the warning color is displayed, if an example of a workpiece that has been ground in advance is recorded, the past optimum machining condition numerical value can be replaced by pressing the machining condition display field. If there is no record, the operator inputs on the operation panel the machining conditions that would be optimal based on experience.

  When the grinding start button is pressed, workpiece grinding is started by relative movement of the workpiece and the grinding wheel based on the machining program, and at the same time, the table moving speed is measured, calculated, and recorded in the recording unit.

  After the workpiece has been ground, the physical properties such as surface roughness (Ra), straightness, thickness, gloss, and presence of chatter marks are measured and sent to the recording unit of the numerical controller. The result is compared with the acceptable physical property value of the workpiece stored in the part, and pass / fail is determined. When a workpiece having better physical properties than the previous machining conditions is obtained, it is rewritten to the current machining conditions. When a workpiece with physical properties inferior to the previous machining conditions is obtained, the machining condition display field back is displayed as a warning color (red) as described above. Replace with the optimum machining conditions.

  Since the work table moving speed measurement method of the present invention measures the table moving speed during work machining, the work table moving speed calculation method that does not include the reverse table moving distance of the conventional table overrun is more realistic. The table moving speed can be calculated. Therefore, ultra-precise grinding with a numerically controlled machine tool becomes possible. Moreover, the replacement time of the grinding wheel can be extended.

1 Numerically controlled machine tool F Machine frame (bed)
w Workpiece (Workpiece)
2 Work table 3 Magnetic chuck 4 Grinding wheel 5 Dock 5a Dock rail 6 On-off type sensor
6a Telegraph cable

Claims (1)

  Used for numerically controlled machine tools that perform machining according to the machining programming conditions stored in the memory section of the numerical controller when grinding a workpiece placed on a workpiece table that reciprocates in the left-right direction with a grinding wheel. In the method of measuring the moving speed of the work table, a single dog with a small width (L) is installed on the work table or magnetic chuck surface near the work point where the work and the grinding wheel abut, One on-off sensor is mounted, and the on-off sensor no longer senses the reverse end of the dock that continues to move after the on-off sensor senses (on) the left or right edge of the dock ( time (t) until the time (off) is measured with a timer, and the table moving speed = (L / t) m / min is calculated. .