JPH0760338B2 - Numerical controller for machining non-round workpieces - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a numerical control device for controlling the machining of a non-round work piece such as a cam (hereinafter, simply referred to as "workpiece").

[Prior art]

Conventionally, a method is known in which a numerical control device controls the feed of a grinding wheel in the direction perpendicular to the spindle axis in synchronization with the spindle rotation, and grinds a workpiece such as a cam. The required machining shape can be obtained by adding profile data to a numerical control device that controls the feed of the grinding wheel synchronously with the rotation of the spindle. On the other hand, the rotation speed of the spindle is controlled so that the grinding speed is constant at an arbitrary point on the workpiece. Then, in order to realize the speed control, the rotation speed of the spindle is given stepwise by the rotation angle of the spindle at which a constant grinding speed condition is not satisfied in a predetermined range.

[Problems to be Solved by the Invention]

In this way, the main rotation speed changes stepwise,
The acceleration / deceleration becomes too large at the angle at which the speed changes,
Vibration of the mechanical system was generated, which adversely affected the surface properties of the machined surface. In order to eliminate such a drawback, it is considered that the rotation speed of the spindle is specified in detail and the change in the rotation speed of the spindle is made smooth. However, the above method has a problem that the input data increases, and much labor and time are required for preparation for processing. The present invention has been made to solve the above problems, and an object of the present invention is to provide a machined surface even if there is little input data for the override value of the rotational speed of the spindle for the required shape. The object is not to adversely affect the properties, and as a result, the non-round work piece is machined into a predetermined shape in a short time.

[Means for Solving the Problems]

According to the configuration of the invention for solving the above problems, profile data indicating the relationship between the rotation angle of the spindle and the position of the tool feed shaft is created according to the lift data that specifies the shape of the non-round work and the diameter of the grindstone. However, in a numerical control device that controls machining of non-round workpieces according to profile data, profile data storage means for storing profile data and rotation of the spindle depending on the machining shape, which is less than the number of profile data data points. Value storage means that stores the number of override values stepwise for each angular range of the spindle that does not satisfy the constant machining speed condition, and the change in the required angle and override value of the connecting section that smoothly changes the spindle speed. A ratio storage means for storing the relationship between the quantities as a ratio and each rotation angle at which the rotation speed of the spindle in the override value storage means changes. Determine the required angle of the connecting section from the amount of change in the spindle rotational speed and the ratio, and obtain the sequence of override values that smoothly changes the rotational speed of the spindle in the connecting section. Override value calculation means for obtaining the overriding value for each pitch from the overriding value stored in the overriding value storage means and the overriding value obtained by the overriding value smoothing means, and the overriding value obtained by the profile data and the overriding value computing means And position control means for numerically controlling the spindle and the tool feed shaft based on the above.

[Action]

The shape of the non-round work piece is given by lift data indicating the relationship between the rotation angle and the lift amount. The lift data specifies the shape of the non-round work by a sequence of points. A smooth curve considering the allowable error close to the lift data consisting of this point sequence is obtained, and by the numerical value and the grindstone diameter for each predetermined rotation angle obtained from the smooth curve,
Profile data is created. On the other hand, it is necessary to grind within a range of a constant speed change amount so as not to adversely affect the property of the machined surface, but for this reason, the rotation speed of the spindle is overridden and the rotation speed of the spindle is changed. Then, the point sequence of the overriding value obtained by smoothing the rotational speed of the spindle is obtained for each rotational angle at which the rotational speed of the spindle changes, based on the ratio between the angular difference in the connecting section and the change amount of the override value. Then, for each pitch of the profile data, the override value of the rotation speed of the spindle is calculated, including the connecting section. Next, based on the profile data and the override value, the rotation speed of the spindle and the position of the tool feed shaft are synchronously controlled, and the non-round workpiece is machined.

【Example】

Hereinafter, the present invention will be described based on specific examples. FIG. 1 is a block diagram showing a numerical control grinding machine. Reference numeral 10 is a bed of a numerical control grinder, on which a table 11 driven by a servo motor and a screw feed mechanism (not shown) is slidably arranged in the Z-axis direction parallel to the spindle axis. There is. A headstock 12 having a main shaft 13 mounted thereon is arranged on the table 11, and the main shaft 13 is rotationally driven by a servomotor 14. A tailstock 15 is placed on the right end of the table 11, and a workpiece W composed of a camshaft is held by a center 16 of the tailstock 15 and a center 17 of the spindle 13. The workpiece W is fitted to the positioning pin 18 protruding from the spindle 13,
The rotation phase of the workpiece W matches the rotation phase of the spindle 13. A tool base 20 that can move back and forth toward the workpiece W is guided behind the bed 10, and a grinding wheel G that is rotationally driven by a motor 21 is supported on the tool base 20. This tool base 20
Is connected to the servo motor 23 via a feed screw (not shown), and is moved forward and backward by the forward and reverse rotation of the servo motor 23. The drive units 51 and 52 are circuits that input command pulses from the numerical control device 30 and drive the servomotors 14 and 23, respectively. Pulse generators 53, 55 and speed generators 54, 56 are coupled to the servomotors 14, 23, respectively, and their outputs are fed back to the drive units 51, 52 for feedback control of speed and position. The numerical controller 30 is a device that mainly controls the rotation of the control shaft to control the grinding of the workpiece W and the correction of the grinding wheel G. As shown in FIG. 2, the numerical controller 30 mainly comprises a main CPU 31 for controlling the grinding machine, a ROM 33 storing a control program, and a RAM 32 storing input data and the like. An NC profile data area 321 for storing machining profile data and an NC override value data area 322 for storing smooth override value data are formed on the RAM 32. The numerical control device 30 further includes a drive CPU 36, a RAM 35, and a pulse distribution circuit 37 as a drive system for the servo motors 14 and 23. RAM35 is from main CPU31 to grinding wheel G, spindle 13
Is a storage device for storing the positioning data of No. 1 and the override value of the rotation speed of the spindle 13. The drive CPU36 is a device that takes into account the override value of the rotational speed of the spindle 13 and performs operations such as slow-up, slow-down, interpolation of the target point, etc. regarding the feed of the control axis for machining, and outputs the positioning data of the interpolation point in a fixed cycle. The pulse distribution circuit 37 is a circuit that outputs a movement command pulse to each drive unit 51, 52 after pulse distribution. Automatic programming device 70 connected to the numerical control device 30
Is an apparatus for automatically creating profile data from lift data and grindstone diameter, and further automatically creating machining override value data from override value data and ratio data. The device is composed of a front CPU 71, a RAM 72 and an input / output interface 73. The RAM 72 has a lift data area 721 that stores lift data for a plurality of workpieces.
And a tolerance data area 722 for storing the tolerance of the finished shape of the workpiece, a wheel diameter data area 723 for storing the current wheel diameter when the profile data is generated, and lift data smoothed within the tolerance. A profile data area 724 that is converted into profile data and stored according to the obtained numerical value for each predetermined rotation angle and the current grindstone diameter, and a spindle that is stepwise given for each large angle range with respect to the shape of the workpiece. Override value data area 725 that stores the override value data of the rotation speed and ratio data area 72 that stores the ratio of the connecting section that smoothly changes the spindle rotation speed
6 and a smoothed override value data area 727 for converting and storing the override value data of the spindle speed in the connecting section, which is converted into smoothed override value data at the ratio of the connecting section. Further, a tape reader 41 for inputting lift data and the like, a keyboard 42 for inputting data, and a CRT display 43 for displaying data are connected to the front CPU 71 via an input / output interface 73. Next, the operation will be described. When the device is set to data entry mode, the front CP
The U71 is a tape reader 4 via the input / output interface 73.
All lift data necessary for machining are read from 1 and stored in the lift data area 721. Similarly, the override value data required for processing is read and stored in the override value data area 725. Now, when the device is set to the profile data creation mode, the front CPU 71 smoothes the lift data in the lift data area 721 within the permissible error in the permissible error data area 722, and the numerical value for each predetermined rotation angle and the grindstone diameter. Data area 72
The profile data is calculated by using the current grinding wheel diameter of 3. The profile data is stored in the profile data area 724 and transferred to the NC profile data area 321 via the front CPU 71 and the main CPU 31 when the cam is actually processed. Next, the operation of the front CPU 71 will be described with reference to the flowchart of FIG. 3 when the device is set to the smoothed override value data creation mode. First, in step 100, the override value data area 7
Read the 25 override value data. Next step
Moving to 102, the ratio data in the ratio data area 726 is read. Next, in step 104, the required smoothing angle n is calculated from the override change amount m based on the ratio data in each connecting section of the override value data. Next, the process proceeds to step 106, where smoothing points (10
Point) is calculated as a point on a curve connecting two mathematical points. Next, in step 108, the straight line equations connecting the smoothing points are calculated.
Next, the routine proceeds to step 110, where interpolation processing is performed in each connecting section of the override value data for each pitch of the profile data described above. Then, the process proceeds to step 112, and the override value data including the interpolated override value data is output for each pitch in the entire section of the profile data, and the process is ended. The override value data is stored in the smoothed override value data area 727 and transferred to the NC override value data area 322 via the front CPU 71 and the main CPU 31 when the workpiece W is actually machined. The override value data required for processing is, for example, the fourth
For a non-round work piece as shown in Figure (a),
It is given for each angle range shown in (A), (B), ..., (F), which is a stepwise graph of the override value of the spindle rotational speed with respect to the angle as shown in FIG. 4 (b). expressed. In this figure, the override value, which is the input data of the spindle speed in the angular ranges (A), (B), ..., (F) in FIG. 4 (a), is shown as a specific value.
The front CPU 71 converts the stepwise input override value data into smooth smoothed override value data connected by a curve according to the flowchart of FIG. 3 described above. Then, when the machining command signal is given from the operation panel 45, the main CPU 31 follows the NC profile data stored in the NC profile data area 321 and the NC override value data stored in the NC override value data area 322. Cam grinding is executed by outputting a machining command.

【The invention's effect】

The present invention stores the override value of the number of revolutions of the spindle corresponding to the machining shape, which is smaller than the number of data points of the profile data, stepwise for each angular range of the spindle where the constant machining speed condition is not satisfied, and the rotation of the spindle. The relationship between the required angle of the connecting section for smoothly changing the number and the change amount of the override value is stored as a ratio. Then, the required angle of the connecting section is obtained from the change amount and the ratio of the rotating speed of the spindle at each rotation angle at which the rotating speed of the spindle changes, and a sequence of override values that smoothly changes the rotating speed of the spindle in the connecting section. Then, the override value for each pitch of the profile data is obtained from the override value stored in the override value storage means and the override value obtained by the override value smoothing means. Therefore, as described above, a smoothly changing override value can be obtained by inputting an override value smaller than the number of data points of the profile data.
Further, since the angle of the connecting section is obtained according to the change amount of the override value, it is possible to smoothly connect at the minimum necessary connecting section angle, and it is possible to quickly and smoothly change the processing speed. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a numerical control grinding machine according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of the numerical controller. FIG. 3 is a flowchart showing the processing procedure of the front CPU 71. FIG. 4A is an explanatory view showing one shape of the non-round work and the override value of the spindle rotation speed with respect to the angle. FIG. 4B is a graph showing the smoothed override value data with respect to the input override value data. 10 …… bed, 11 …… table, 13 …… spindle 14,23 …… servo motor, 15 …… tailstock 20 …… tool stand, 30 …… numerical control device 53,55 …… pulse generator 54,56 ...... Speed generator 70 …… Automatic programming device G …… Grinding wheel, W …… Workpiece

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-93510 (JP, A) JP-A-62-100813 (JP, A) JP-A-61-86163 (JP, A)

Claims (1)

[Claims] 1. Profile data showing the relationship between the rotation angle of the spindle and the position of the tool feed axis is created in accordance with the lift data that specifies the shape of the non-round work and the diameter of the grindstone, and the profile data is created in accordance with the profile data. In the numerical controller for controlling the machining of the non-round workpiece, a profile data storage means for storing the profile data, and an override of the number of revolutions of the spindle according to the machining shape, which is less than the number of data points of the profile data. Override value storage means for storing a value stepwise for each angular range of the spindle in which a constant machining speed condition is no longer satisfied; a required angle of a connecting section for smoothly changing the rotational speed of the spindle; and a change in the override value The ratio storage means for storing the relationship between the quantities as a ratio, and the rotation speed of the spindle in the override value storage means change Override value smoothing means for obtaining a required angle of the connecting section from the amount of change in the number of rotations of the spindle at each rotation angle and the ratio, and obtaining a sequence of override values for smoothly changing the number of rotations of the spindle for the connecting section. An override value calculation means for obtaining an override value for each pitch of the profile data from the override value stored in the override value storage means and the override value obtained by the override value smoothing means, the profile data and the A numerical control device for machining a non-round workpiece, comprising: position control means for numerically controlling the spindle and the tool feed axis based on the override value obtained by the override value calculation means.