JP4201970B2 - Non-circular workpiece processing data creation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a data creation device for controlling machining of a non-round workpiece such as a cam.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a method of grinding a non-round workpiece such as a cam by controlling a feed of a grinding wheel in a direction perpendicular to a spindle axis in synchronization with rotation of a spindle by a numerical controller is known. The machining shape of the non-circular workpiece is obtained by assigning profile data to the numerical controller in order to synchronously control the feed of the grinding wheel with respect to the rotation of the spindle. This profile data gives the amount of movement of the grinding wheel per unit rotation angle of the spindle so that the grinding wheel is reciprocated along the finished shape of the workpiece. It is demanded from. The override value that determines the spindle speed is empirically corrected by the operator while observing the machining result, and machining is performed using the override value, and the work of reflecting the result is repeated. Was done.
[0003]
However, in this technique, since the spindle speed is set based on the experience and intuition of the operator, there is a problem that the cycle time increases when the above correction is repeated in rough machining. Moreover, in the finishing process, when the set value of the spindle rotation speed is larger than the optimum value, there is a problem that the grindstone cannot follow and the machining accuracy is lowered.
[0004]
For this reason, a technique has been developed in which the spindle rotational speed is determined from the limit feed speed and limit acceleration that can be followed by the grinding wheel head, and the machining accuracy is improved. (Japanese Patent Laid-Open No. 10-283012)
[0005]
[Problems to be solved by the invention]
However, in the technique described in Japanese Patent Application Laid-Open No. 10-283012, the spindle rotational speed itself is automatically determined from the limit feed speed and limit acceleration, but the override value is still set by the operator based on experience and intuition. .
[0006]
For this reason, the spindle rotation speed is controlled to within the limit limit for the grinding wheel head feed speed and acceleration, but the override value is not appropriate, and in rough machining aimed at shortening the cycle time, the machining speed may decrease more than necessary. In some cases, the contact speed may partially exceed the limit value in the finishing process and the surface properties may be deteriorated, so that a desired processing accuracy may not be obtained.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention relates to the lift data for specifying the shape of a non-round workpiece and the grinding wheel diameter, and the rotation angle of the spindle holding the non-round workpiece and the position of the grinding wheel platform. In the non-circular workpiece machining data creation device for creating profile data indicating the relationship between the non-circular workpiece and the non-circular workpiece based on the profile data stored in the profile data storage means Rough machining override calculating means for calculating an override value for the rotational speed of the spindle according to the machining shape of the spindle so that the grinding amount per unit time is constant, and the profile data stored on the profile data storage means based on the profile data And finishing machining override calculating means for calculating the override value so that the contact speed is constant.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on specific examples. FIG. 1 is a schematic diagram showing the configuration of a numerically controlled grinding machine 1. A table 11 is disposed on the bed 10 so as to be slidable in the Z-axis direction parallel to the main axis. The table 11 is driven via a servo motor 8 and a feed screw 9. On the table 11, a headstock 12 having a spindle 13 mounted thereon is disposed, and the spindle 13 is rotationally driven by a servo motor 14. A tailstock 15 is placed on the right end of the table 11, and a workpiece W composed of a camshaft is held between the center 16 of the tailstock 15 and the center 17 of the main shaft 13. The workpiece W is fitted to a positioning pin 18 projecting from the main shaft 13, and the rotational phase of the workpiece W is matched with the rotational phase of the main shaft 13. Behind the bed 10, a grinding wheel platform 20 that can be advanced and retracted toward the workpiece W is guided, and a grinding wheel G that is rotationally driven by a motor 21 is supported on the grinding wheel platform 20. The grinding wheel base 20 is moved forward and backward in the X-axis direction orthogonal to the Z-axis by a linear motor 23 attached to the lower part.
[0009]
A linear encoder 22 for detecting the position of the grinding wheel base 20 is provided on the side surface of the grinding wheel base 20.
The servo motors 8 and 14 and the linear motor 23 are connected to the control device 30 via servo amplifiers 51, 52 and 53, respectively. Further, rotary encoders 54 and 55 are connected to the servo amplifiers 51 and 53, and linear servos are connected to the servo amplifier 52. It is connected to the encoder 22.
[0010]
The servo amplifiers 51, 52, and 53 are circuits that input position command signals from the numerical controller 30 and drive the servo motors 8, 14 and the linear motor 23. Outputs of the rotary encoder 54 and the linear encoder 22 are fed back to the servo amplifiers 51 and 52, and feedback control of speed and position is performed.
[0011]
The numerical control device 30 is mainly composed of a numerical control device (CNC device) 31, a programmable controller (PLC) 32, a servo control device 33, and an Ethernet communication interface 34, which are connected via a bus line 25 and a bus interface 26, respectively. Is done.
The CNC device 31 is a device that mainly calculates rotation of the spindle 13 and feed control of the grinding wheel G and profile data necessary for machining the workpiece W and override of the spindle 13 according to commands from an operation panel 45 described later.
[0012]
As shown in FIG. 2, the CNC device 31 includes a CPU 35, a ROM 36 that stores a control program, and a RAM 37 that stores input data and the like. On the RAM 37, as shown in FIG. 3, the lift data area 321 for storing the lift data of the workpiece W, and the machine data for storing the diameter of the grinding wheel G when generating the profile data, machine-specific constants, and the like. An area 322, a profile data area 323 for storing profile data calculated from lift data and the diameter of the grinding wheel G, and a rough machining override value data area 324 for storing override value data at the time of rough machining with respect to the spindle rotational speed A finish machining override value data area 325 for storing the override value data at the time of finishing machining, and an NC program area 326 for storing an NC for machining the workpiece W and an NC program for machining the workpiece W are formed. ing.
[0013]
The PLC 32 performs on / off control such as rotation / stop of the motor 21 that rotates the grinding wheel G and driving / stopping of a pump that supplies the grinding fluid. Further, the servo control device 33 inputs the grinding wheel G, the positioning data of the main shaft 13 and the override value for the rotational speed (rpm) of the main shaft 13 from the CNC device 31, and the rotational angle position of the main shaft 13 and the rotational speed of the main shaft 13 are input. In consideration of the override value, calculations such as slow-up, slow-down, target point interpolation, etc. are performed on the feed of the grinding wheel platform 20 related to machining, and interpolation point positioning data is output to the servo amplifiers 51, 52, 53 at a constant cycle. Device.
[0014]
The operation panel 45 includes a display device 46 for displaying various data and the like, and a switch group 47 for inputting data. The display device 46 is a touch panel, and an operator can operate on the data displayed on the display device 46. Data can be input by touching with a finger or the like.
The operation of the CNC device 31 for determining the override value with the above configuration will be described below. When the data calculation mode is set by operating the operation panel 45, the CNC device 31 causes the grindstone for each rotation angle θ of the spindle 13 based on the lift data in the lift data area 323 and the current grindstone diameter in the machine data area 322. The position data X (θ) of the table 20 is calculated to create profile data, which is stored in the profile data area 323.
[0015]
Next, the operation of the CPU 35 will be described below with reference to the flowchart of FIG. 4 regarding the creation of override value data used by the numerically controlled grinding machine 1 for rough machining.
First, in step 100, profile data is read from the profile data area 323.
Next, in step 102, a grinding removal rate limit value Pmax indicating the grinding efficiency within a predetermined time is set. The limit value Pmax of the grinding removal rate is arbitrarily determined by the operator from the performance of the grinding wheel G, the material of the workpiece W, and the like, and is input from the control panel 45.
[0016]
Next, at step 104, the grinding amount Qi in the section i at every predetermined angle (0.5 degree in the embodiment) when the workpiece W is caused to generate a cam by using the profile data X (θ) and the cutting amount t is given. Ask for. Here, as shown in FIG. 6, the grinding amount Qi accumulates (integrates) the tangential arc H (θ) of the workpiece W and the grinding wheel G for each rotation angle θ when the cutting amount t is given for the section i. Is required. The cutting amount t can be obtained from the NC program stored in the NC program area 326. A symbol i attached to each symbol is a variable for representing a section of one round of the workpiece. For example, if the predetermined angle is every 0.5 degrees, the symbol i is a variable between 0 and 720.
[0017]
Next, at step 106, the grinding removal rate Pi is obtained. The grinding removal rate Pi indicates a grinding amount that can be ground within the time Ti, and is expressed by the following equation.
[Expression 1]
Pi = Qi / Ti− (1)
Here, when the base circle of the workpiece W is ground as the initial value Tb, the time Ti is arbitrarily set as the time required for grinding the section i by rotating the spindle 13 at the rotation speed Nb [rpm]. Even if the operator empirically determines from the mechanical performance and the material of the grindstone, etc., or from the performance of the grindstone table 20 of the numerical control grinding machine 1, etc., as in the technique described in JP-A-10-283012, The rotational speed Nb may be determined from the limit feed speed and limit acceleration that can be followed by the grinding wheel platform.
[0018]
The initial value Tb is obtained from the following equation from the spindle speed Nb.
[Expression 2]
Tb = predetermined angle i / angular velocity = i / ((2π / 60) Nb) − (2)
However, i [degree] × π / 180 [rad].
Next, in step 108, it is determined whether or not the grinding removal rate Pi is equal to the limit value Pmax input in step 102. If it is not equal to the limit value Pmax, the process proceeds to step 110. Proceed to
[0019]
In step 110, it is determined whether or not the grinding removal rate Pi is greater than the limit value Pmax. If greater than the limit value Pmax, the process proceeds to step 114. If smaller than the limit value Pmax, the process proceeds to step 116.
In step 114, a predetermined minute time α is added to the time Ti, and the process returns to step 106 to calculate the grinding removal rate Pi again. When the routine proceeds to step 116, the minute time α is subtracted from the time Ti, and the routine returns to step 106 to calculate the grinding removal rate Pi again.
[0020]
Thereafter, Step 106 to Step 116 are repeated until the grinding removal rate Pi becomes equal to the limit value Pmax, and the time Ti is expanded or contracted.
On the other hand, when proceeding to step 118, the override value OVi [%] of the section i is obtained by the following equation.
[Equation 3]
OVi = 100 × Tb / Ti − (3)
Here, Tb is an initial value of time Ti.
[0021]
Thereafter, the override value OVi of the section i is stored in the rough machining override value data area 324, and it is determined whether or not the override value OVi of all sections corresponding to one round of the workpiece W is obtained in step 120. If the override value OVi for all the sections has not been obtained, the process proceeds to the next section i + 1, and steps 104 to 118 are repeated to obtain the override value OVi for all the sections (one work rotation).
[0022]
Thus, an override value with a constant grinding removal rate Pi as shown in FIG. 5A is obtained. In FIG. 5A, the vicinity of 0 to 90 degrees, the vicinity of 270 to 360 degrees corresponds to the base circle portion of the workpiece W, and the vicinity of 180 degrees corresponds to the cam top portion of the workpiece W.
Next, creation of override value data used by the numerically controlled grinding machine 10 for finishing will be described below with reference to the flowchart of FIG.
First, in step 250, profile data X (θ) is read from the profile data area 724.
[0023]
Next, in step 252, a grinding speed limit value Kmax is set. The grinding speed limit value Kmax is input from the control panel 45 by arbitrarily determining a speed at which the base circle portion of the workpiece W can be ground with a desired finish accuracy based on the experience of the operator or past experimental data. Input into the RAM in advance.
Next, at step 254, the contact travel distance Li on the surface of the workpiece W for a predetermined angle (0.5 degrees in the embodiment) section i, that is, the circumferential length of the predetermined angle of the workpiece W as shown in FIG. Although equivalent to this, if the section i is set to a very small angle (about 0.5 degrees), it can be replaced with a linear distance between the section i and the section i-1.
[0024]
Next, in step 256, the contact moving speed Ki is obtained. This contact moving speed Ki indicates a grinding speed that can be ground within the time Ti, and is expressed by the following equation.
[Expression 4]
Ki = Li / Ti− (4)
Here, when the base circle of the workpiece W is ground as the initial value Tb, the time Ti is arbitrarily set as the time required for grinding the section i by rotating the spindle 13 at the rotation speed Nb [rpm]. The operator is determined empirically from the mechanical performance and the material of the grinding wheel.
The initial value Tb is obtained from the formula (2) from the spindle speed Nb.
[0025]
Next, in step 258, it is determined whether or not the contact moving speed Ki is equal to the limit value Kmax input in step 252, and if it is not equal to the limit value Kmax, the process proceeds to step 260, and if it is equal to the limit value Kmax, step 268 is performed. Proceed to In step 260, it is determined whether or not the contact moving speed Ki is greater than the limit value Kmax. If greater than the limit value Kmax, the process proceeds to step 264. If smaller than the limit value Kmax, the process proceeds to step 266.
[0026]
In step 264, a predetermined minute time α is added to the time Ti, and the process returns to step 256 to calculate the contact moving speed Ki again. Further, when the process proceeds to step 266, the minute time α is subtracted from the time Ti, and the process returns to step 256 to calculate the contact moving speed Ki again.
Thereafter, step 256 to step 266 are repeated until the contact moving speed Ki becomes equal to the limit value Pmax, and the time Ti is expanded or contracted.
[0027]
On the other hand, when the routine proceeds to step 268, the override value OVi [%] of the section i is obtained by the equation (3), stored in the finishing machining override value data area 325, and in step 270, the entire section corresponding to one round of the workpiece w is obtained. It is determined whether or not the override value OVi is obtained. If the override value OVi for all the sections has not been obtained, the process proceeds to the next section i + 1, and steps 254 to 270 are repeated to obtain the override value OVi for all the sections (one work rotation).
[0028]
As a result, an override value with a constant contact speed Ki as shown in FIG. 5B is obtained.
[0029]
Thereafter, when a machining command signal is given from the operation panel 45, the CPU 35 stores the profile data stored in the profile data area 321, the rough machining override value data area 322, and the finishing machining override value data area 323. The grinding of the cam is executed by outputting a machining command according to the rough machining override value and the finishing machining override value.
[0030]
As described above, the override value OVi of the main shaft 13 is determined to obtain an override value that keeps the grinding removal rate constant in order to shorten the cycle time (grinding time) in rough machining, and the machining accuracy (especially surface properties) is improved in finishing machining. For this reason, the override value that keeps the contact speed (grinding speed) constant is obtained, so that it is possible to reduce the machining time and improve the machining accuracy.
[0031]
In the above embodiment, the CNC device 31 is used as a non-circular workpiece machining data creation device. However, the present invention is not limited to this, and a general-purpose computer is used instead of the CNC device 31 to override roughing and finishing. A value may be obtained.
[0032]
The rough machining override calculating means of the present invention corresponds to the flowchart shown in FIG. 4 of the above embodiment and the CNC device 31 for executing the flowchart of FIG. Further, the finishing machining override calculation means corresponds to the flowchart of FIG. 7 and the CNC device 31 that executes the flowchart. Further, the profile data storage means corresponds to the RAM 37.
[0033]
【The invention's effect】
As described above, in the present invention, the override value of the spindle is determined to obtain an override value that maintains a constant grinding amount (grinding removal rate) per unit time in order to shorten the cycle time (grinding time) in rough machining, and is processed in finish machining. In order to improve the accuracy (particularly the surface property), the override value that makes the contact speed (grinding speed) constant is obtained, so that there is an effect that both the processing time can be reduced and the processing accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is a view showing an overview of a numerically controlled grinding machine according to a specific embodiment of the present invention.
FIG. 2 is a diagram showing an electrical configuration of a control device according to a specific embodiment of the present invention.
FIG. 3 is a schematic diagram showing a data configuration of a RAM of a numerical controller according to a specific embodiment of the present invention.
FIG. 4 is a flowchart showing a calculation procedure of rough machining override by a numerical controller according to a specific embodiment of the present invention.
FIG. 5 is a graph showing rough machining override values and finishing machining override values according to a specific example of the present invention.
FIG. 6 is a diagram for explaining a grinding amount of a workpiece W by a grindstone per unit time.
FIG. 7 is a flowchart showing a calculation procedure of finishing machining override by the numerical controller according to the specific embodiment of the present invention.
FIG. 8 is a diagram for explaining a contact movement amount when machining a workpiece and a grindstone.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Numerical control grinding machine 11 Table 13 Spindle 20 Grinding wheel stand 30 Control apparatus 31 Numerical control apparatus (CNC apparatus)
37 RAM
G Whetstone W Workpiece

Claims (1)

Non-circular circle that creates lift data that identifies the shape of the non-circular workpiece and profile data that indicates the relationship between the rotation angle of the spindle that holds the non-circular workpiece and the position of the grinding wheel base, depending on the wheel diameter In a workpiece machining data creation device, a storage means for storing profile data, and an override for the rotational speed of the spindle according to the machining shape of the non-circular workpiece based on the profile data stored in the profile data storage means Rough machining override calculating means for calculating the value so that the grinding amount per unit time becomes constant, and the override value is calculated based on the profile data stored in the profile data storage means so that the contact speed is constant. A non-circular workpiece machining data creation device comprising finishing machining override calculation means.

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