KR940008088B1 - Numerically controlled machine tool and method of controlling grinding operation thereof - Google Patents

Abstract

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Description

Numerical control machine tool and its grinding motion control method

1 is a schematic diagram in the form of a partial block of a numerically controlled machine tool according to the present invention.

2 is a flowchart of a process for producing a roll of a desired shape using the numerically controlled machine tool of the present invention.

3A to 3E are partial views illustrating the shape and parameters of the roll.

4 is a diagram showing a storage area for storing roll shapes, parameters and other data.

5 is a graph showing the relationship between the drive current supplied to the grinding wheel rotary motor and the amount of grinding by the grinding wheel.

6 and 7 are partial views showing a path for grinding a roll by a grinding wheel.

8 is a flowchart of a skipping control sequence of the grinding control method according to the present invention.

9 is a graph showing the relationship between the amount of elastic deformation of the roll and the drive current supplied to rotate the grinding wheel.

10 is a graph showing the relationship between the wear rate of the grinding wheel and the drive current supplied to the grinding wheel rotary motor.

11 is a diagram showing a roll grinding process.

12 is a block diagram of a system for correcting the amount of grinding of a roll to be ground, depending on the elastic deformation of the roll and wear of the grinding wheel.

13 is a flowchart for a sequence for grinding a roll having a preset current in the grinding control method of the present invention.

14 to 16 are partial views showing the path of the grinding wheel according to the grinding control method of the present invention.

* Explanation of symbols for main parts of the drawings

2: roll or workpiece 4: headstock

6: tailstock 10: spindle motor

12: grinding wheel 16: slide table

22: servo motor 24: grinding wheel motor

30: numerical control device 32, 34, 36: drive device

38: processor 40: storage device

46: input device 48: display device

50: roller grinding step 52: elastic deformation correction means

54: wear correction means 56: grinding control means

The present invention relates to a numerically controlled machine tool, such as a roll grinding machine for grinding a workpiece into a roll shape, and a grinding operation control method of the numerically controlled machine tool, in particular to correct wear and damage of a workpiece, The present invention relates to a numerically controlled machine tool capable of processing a workpiece into a desired shape while considering tool wear and the like.

Numerically controlled machine tools, typically a roll grinder for grinding the workpiece in a roll shape, rotate the workpiece at a predetermined speed, radially move the tool towards and away from the workpiece, and move it in the axial direction of the workpiece. In general, it is arranged to grind the workpiece into a roll shape. Since the tool must be moved, the machine tool has a storage device for storing numerical control data, whereby the radial movement amount of the tool depending on the axis position of the tool is continuously programmed and driven to move the tool. The control device for supplying a command pulse to the device is based on the numerical control data. The numerical control machine tool is widely used for roll processing and the like.

Rolls processed by numerically controlled machine tools include rolls of different shapes, from simply cylindrical rolls to rolls with pointed, sinusoidal and sharp outer peripheral shapes for various applications. To date, rolls with a sharp outer periphery have been usually ground using cams. However, with the use of cams, when the rolls to be ground have different outer peripheral shapes, different lengths, different radii or other different parameters, an appropriate cam must be selected and the drawback of the grinding process is low.

It is possible to machine the workpiece with a desired roller having an outer peripheral shape that can be displayed relatively simply, such as a sinusoidal curve. In such a machining process, the workpiece to be processed is divided into small portions, each of the small portions is approximated by a straight line or an arc to generate numerical control data (processing program), and the generated numerical control data is subjected to the machining. Used to control the machine. However, because the generated machining programs are very long and complex, they are not suitable for producing rolls with complex outer peripheral shapes.

In order to precisely roll the workpiece into the roll, the cutting depth of the workpiece that is radially ground by the tool (ie, the rotary grinding wheel) is very important during the grinding process. If there are no other factors or factors to consider, then the target (command) depth of the cut should be equal to the net depth of the cut so that the workpiece can be ground accurately.

However, when continuing the grinding process on the roll grinding machine, the rotary grinding wheel is worn, so that the actual cutting depth is smaller than the desired cutting target length. In addition, during the grinding process, since the grinding wheel is subjected to a predetermined pressure on the workpiece, the workpiece roll is somewhat elastically deformed. The amount of elastically deforming the roll also reduces the actual cutting depth to be smaller than the desired target cutting depth.

Therefore, for high precision grinding of workpieces into rolls, it is necessary to prepare a machining program considering the wear on the grinding wheel and the elastic deformation of the rolls. Since the amount of correction performed by the machining program for wear and elastic deformation varies from grinding wheel to grinding wheel and from roller to roll, an estimate of the compensation amount for each grinding wheel and each roll must be determined. The amount of wear of the grinding wheel changes with the time of the grinding process, and it is very difficult to prepare a numerical control program considering the time dependent change of the amount of wear. Measure the size of the roll in one exercise to grind the workpiece using the machining program prepared as a predictive value, check the dimensional accuracy when the grinding wheel reaches the target grinding position, correct the grinding depth, and then again To start. However, this grinding operation is very poor in efficiency.

The rolls used for a given time wear differently depending on what they were used for and how they were used. Even one roll has parts that wear to a greater extent and parts that wear to a lesser extent. Therefore, in order to efficiently grind these rolls, the less worn parts should be intensively grounded by a process known as a truing process, in the desired roll shape.

In the truing process, the individual roll shape must measure how it is worn and prepare a machining program for grinding the roll based on this measurement. Optionally, a machining program for grinding rolls to a constant diameter, regardless of how they are worn, should be used to grind the rolls. According to the former process, a machining program must be prepared for each of the rolls to be ground according to the wear state of the rolls. The latter constant grinding method does not require a machining program to prepare for each roll, but it takes a long time because the rollers must be constantly ground regardless of their wear condition.

The main object of the present invention is to take into account the wear of a tool such as a rotary grinding wheel and the elastic deformation and local wear of the workpiece, for example a numerically controlled machine tool such as a roller grinder which can efficiently and accurately mill the workpiece to the desired shape. And a method for controlling a numerically controlled machine tool.

It is another object of the present invention to provide a numerically controlled machine tool for grinding a workpiece into a roll shape by rotating the workpiece around its axis at a predetermined speed and moving the grinding machine in the radial and axial directions of the workpiece. The machine tool includes first driving means for rotating the grinding machine, detection means for detecting the drive current supplied to the first driving means, second driving means for moving the grinding machine in the radial direction of the workpiece, and the detection. And a control means for comparing the drive current value detected by the means with the preset current value and controlling the second driving means based on the comparison result.

It is still another object of the present invention to provide a numerically controlled machine tool for grinding a workpiece into a roll shape by rotating the workpiece around its axis at a predetermined speed and moving the grinding machine in the radial and axial directions of the workpiece. The machine tool includes first driving means for moving the grinding machine in the radial direction of the workpiece, second driving means for moving the grinding tool in the axial direction of the workpiece, and setting means for setting the grinding shape of the workpiece as a formula; And control means for preparing point group data for controlling the first and second driving means based on the formula set by the setting means.

It is still another object of the present invention to provide a numerically controlled machine tool for rotating a workpiece around its axis at a predetermined speed and grinding the workpiece in a roll shape by moving the grinding machine in the radial and axial directions of the workpiece. The machine tool includes a detection means for detecting a drive current supplied to a drive motor for rotating the grinder, and a wear correction for calculating the amount of wear on the grinder as a movement correction amount of the grinder in the radial direction of the workpiece based on the detected drive current value. Means and means for adding a movement aid amount of the grinding machine to the movement target amount in order to compensate for the reduction of the grinding amount due to the wear of the grinding machine.

It is still another object of the present invention to provide a numerically controlled machine tool which rotates a workpiece around its axis at a predetermined speed and moves the grinding machine in the radial and axial directions of the workpiece to grind the workpiece. Detecting means for detecting the drive current supplied to the drive motor to rotate the grinder, and the amount of elastic deformation of the grinder produced by grinding the workpiece with the grinder in the radial direction of the workpiece, based on the detected drive current value. Elastic deformation correction means for calculating the movement correction amount, and means for compensating for the reduction in the amount of grinding due to the elastic deformation of the grinding machine by adding the movement correction amount of the grinding machine to the movement target amount.

Another object of the present invention is a method for controlling the grinding operation of a numerically controlled machine tool which rotates a workpiece around its axis at a predetermined speed and moves the grinding machine in the radial and axial directions of the workpiece to grind the workpiece into a roll shape. The grinding operation control method includes selecting a grinding shape of a workpiece and a workpiece to be calculated, selecting a parameter by the selected grinding shape, and applying a predetermined formula based on the parameter and the grinding shape. Calculating point group data for grinding the workpiece, storing the point group data in a storage area of the storage device corresponding to the workpiece, reading the stored point group data from the storage device, and grinding the workpiece. Controlling the grinder based on this point group data for grinding into the shape. Doing.

Another object of the present invention is to control the grinding operation of a numerically controlled machine tool which rotates a pore at a predetermined speed around its axis and moves the grinder in the radius and axial direction of the workpiece to grind the workpiece into a roll shape. The method of controlling grinding operation comprises the steps of: detecting a drive current supplied to a drive motor to rotate the grinder, and causing the grinder to operate until the detected drive current value reaches a preset current value; Grinding the workpiece in the direction of the workpiece; then grinding the workpiece by moving the grinding wheel in the axial direction of the workpiece; and when the detected driving current value falls below the preset current value, the detected driving current value is the preset current value. Causing the grinding machine to grind the workpiece in its radial direction until And the step of continuously grinding the workpiece by switching the movement of the grinding machine in the axial direction of the workpiece.

Another object of the present invention is a method for controlling the grinding operation of a numerically controlled machine tool which rotates a workpiece around its axis at a predetermined speed and moves the grinding machine in the radial and axial directions of the workpiece to grind the workpiece into a roll shape. This grinding operation control method comprises the steps of: detecting a drive current supplied to a drive motor to rotate a grinding machine; and after the detected drive current value coincides with a preset comparison state, another machining from a machining program to be executed. And switching to the program.

It is yet another object of the present invention to provide a method for controlling the grinding operation of a numerically controlled machine tool, wherein another machining program from a machining program to be executed is executed when the detected current value reaches a preset current value in a preset comparison state. Switching is executed.

It is another object of the present invention to provide a method for controlling the grinding operation of a numerically controlled machine tool, wherein the difference between the detected drive current value and the preset current value in the preset comparison state is determined and the workpiece is ground. To this end, the grinding machine is moved toward the workpiece at a predetermined speed based on this difference.

Another object of the present invention is a method for controlling the grinding operation of a numerically controlled machine tool which rotates a workpiece around its axis at a predetermined speed and moves the grinder in the radial and axial directions of the workpiece to roll the workpiece into a roll shape. The method provides a first drive means for rotating a grinding machine to perform different machining functions, a second drive means for moving the grinder in the radial direction of the workpiece and moving the grinder in the axial direction of the workpiece. Supplying a plurality of instructions for instructing a predetermined movement with respect to the third driving means for providing a special instruction for enabling at least one of the plurality of instructions, and a special instruction for grinding the workpiece; Selecting and enabling at least one of the plurality of instructions based on the It includes.

Another object of the present invention is a method for controlling the grinding operation of a numerically controlled machine tool which rotates a workpiece around its axis at a predetermined speed and moves the grinding machine in the radial and axial directions of the workpiece to roll the workpiece into a roll shape. The grinding operation control method includes the steps of detecting a driving current supplied to a driving motor to rotate a grinding machine, and based on the detected driving current value in the radial direction of a workpiece, the grinding machine corresponding to the wear amount of the grinding machine. Calculating a movement compensation amount of the motor; correcting the wear correction coefficient and the predetermined period at a predetermined period based on the difference between the target current value supplied to the drive motor and the detected driving current value; Continuously correct the movement correction amount of the grinding machine, and add this corrected amount to the movement target amount It includes the step of compensating for the reduction in the amount of grinding of the work piece due to the wear of the group.

The above and other objects, features and advantages of the present invention will become more apparent from the following description when the preferred embodiments of the present invention are illustrated by way of illustrative embodiments with reference to the accompanying drawings.

1 shows a numerically controlled machine tool according to a preferred embodiment of the present invention. The rolls or workpieces 2 to be processed or ground by the numerically controlled machine tool are held between the main shaft 4 and the tail stock 6 in a line with the axis 8 extending in the Z direction. The spindle 4 includes a spindle which can be rotated by a spindle motor 10 for rotating the roll 2 around the shaft 8 at a predetermined speed.

A grinding machine or rotatable grinding wheel 12 is mounted on a slide table 16 guided by a guide 14 which can rotate about an axis 18. When the slide table 16 is driven by the servo motor 20, the slide table 16 may slide in the Z direction along the guide 14. In addition, the slide table 16, when driven by the servo motor 22, can slide in the X-axis direction (in the radial direction of the roll 2) along another guide mechanism (not shown). The grinding wheel 12 can be rotated about its own axis at a predetermined speed by the grinding wheel motor 24. The drive current (load current) supplied to the motor 24 is detected by a detector used for grinding control to correct the grinding depth and the like, as described later. Numerical control device 30 is a servo device 20, 22, the drive device (32, 34, 36) for rotating the spindle motor 10, the rotation of the roll (2) and the rotation of the grinding wheel 12 and In order to grind the roll 2 in the shape indicated by the numerical control data, a command pulse is supplied to the grinding wheel motor 24 that controls the movement in the Z and X axis directions.

The numerical control device 30 stores a processor 38 composed of a microcomputer or the like, and a storage device 40 for storing the control program for causing the processor 38 to execute numerical control operations, and for storing numerical control data. And a pulse divider 42 for supplying a command pulse to the drive devices 32, 34, 36 by the instruction issued from the processor 38. The control program and the numerical control data may be input to the numerical controller 30 via the input device 46. A display device such as a CRT or the like is indicated by reference numeral 48. The target length of the cutting is denoted by reference numeral R, the net depth of the cut is denoted by reference numeral C, and the radius of the roll before grinding is denoted by reference numeral S.

The numerically controlled machine tool of the present invention will basically operate as described above.

By entering the shape parameters of the numerically controlled machine tool, the rolls 2 of various external peripheral shapes can be created to match the desired action. The grinding process will be described with reference to the flowchart of FIG.

The power supply for the numerically controlled machine tool is turned on in step 1, and then the slide table 16, on which the grinding wheel 12 is rotatably mounted, has a radial direction (X-axis) and a roll ( By moving similarly in the axial direction (Z axis) of 2), it returns to an origin. This operation is performed by monitoring the return process on the display device 48 connected to the numerical control device 30 using the input device 46.

Next, the coordinates of the roll 2 are set in step 3 to determine the moving range of the slide table 16. Step 3 is followed by step 4 in which the shape of the roll 2, the number of the rolls 2 and its parameters are selected and entered. Preferably at this time the numerical control device 30 is in the editing mode and the required data can be easily entered by means of a menu displayed continuously on the display device 48.

The storage device 40 has a storage area for storing the shape and parameters of a plurality of rolls (10 in the illustrated embodiment). First, select the number of the roll, and then select the shape of the roll. There are five available roll shapes including sine shape, sine, taper and arc shape combination, arc, taper and sinusoidal combination, right taper shape and left taper shape and the like. One of these roll shapes may be indicated by a corresponding code number. The user may also stand up another roll shape to display a selected one of these other roll shapes.

After displaying the roll shape, certain parameters can be entered for the roll shape. 3a to 3e show the roll shape and parameters of the different rolls 2. 3a shows a roll 2 having an outer periphery to be ground in a sinusoidal shape. The parameter L represents the display length of cambering, the parameter D represents the depth of the cambering, and the parameter RL represents the roll length. 3b shows a roll 2 having an outer periphery to be ground in a combination of sine, taper and arc curves. The parameters L, D, and RL are the same as those shown in FIG. 3A. The parameter L1 represents the length of the sinusoid, the parameter L2 represents the length of the taper curve, the parameter A represents the amount of taper, and the parameter r represents the radius of the arc. 3c shows a roll 2 having an outer periphery to be ground in a combination of arc, taper and sinusoidal curves. The illustrated parameter is the same as that of FIG. 3B. 3d shows the roll 2 to be ground to the right tapered shape. The parameter RL indicates the roll length, the parameter L indicates the display length of the cambering, and the parameter A indicates the amount of taper. 3e shows a roll 2 having an outer periphery to be ground in a left tapered shape. These parameters are the same as shown in FIG. 3d.

These parameters, as well as the roll number and roll shape, can be entered via the keyboard of the input device 46. The entered roll number, roll shape and parameters are stored in the storage device 40 in a corresponding relationship.

4 shows a storage area of the memory device 40 for storing roll shapes and parameters. P1 represents the coordinates of the left end of the roll, P2 represents the center coordinates of the roll, and P3 represents the coordinates of the right end of the roll. The storage area number 1 stores the roll shape and the parameters for the roll number 1. The stored roll shape is one of the code numbers showing the roll shape shown in Figs. 3A to 3E, and the stored parameters correspond to the stored roll shape. The storage area numbers 2 to 10 store the roll shape and the parameters for the roll numbers 2 to 10.

After entering the roll number, the roll shape and the parameters in step 4, the point group data constituting the numerical control data (processing program) is calculated by a predetermined formula corresponding to the roll shape displayed in step 5. If the roll shape is, for example, the sinusoidal shape shown in FIG. 3A, the cutting depth X at which the roll 2 is radially ground by the grinding wheel is given by the following equation.

Here, 0 ≦ Z ≦ L and Z indicate the axial position of the roll 2, θ is an inherent parameter of the machine tool, and is determined by, for example, the curvature of a sinusoidal curve. The point group data calculated by the above formula is stored in the storage device 40 in a correspondence relationship between the next roll number and the roll shape.

The point group data forming the numerical control data is calculated in the storage device 40 in a predetermined area, and after being stored, the stored point group data is continuously read in step 6, and the axis direction (Z axis) of the grinding wheel 12 is obtained. ) And the movement in the radial direction (X axis) is controlled based on the point group data to grind the roll 2 into the indicated cabring curve. After the roll 2 has been ground over the entire length in step 7, the next step 8 checks whether there is a command for grinding the next roll. If there is an instruction, Steps 3 to 7 are repeatedly executed. Without such a command, the power to the numerical control machine tool is turned off and the grinding process is terminated.

In order to efficiently and very accurately grind the roll 2 using a numerically controlled machine tool such as a roll grinder, local wear on the roll 2 during the extended use or elastic deformation of the roll 2, grinding wheel ( Considering the wear of 12), grinding of the rolls is required.

Various processing functions possessed by the numerical control machine tool will be described below.

5 shows the driving current value I supplied to the grinding wheel motor 24 to rotate the grinding wheel 12 and the amount of movement in the radial direction of the roll 2 of the grinding wheel 12, that is, the cutting depth c. ) Relationship between The drive current I and the cutting depth C are correlated by the function I = h (c), as described below.

While the grinding wheel motor 24 rotates at a constant speed, the torque τ produced by the grinding wheel motor 24 is proportional to the friction force θ generated between the grinding wheel 12 and the roll 2. In a range in which the cutting depth C is not excessively large, the frictional force θ is proportional to the cutting depth C or is increased in forging. therefore,

Where h (C) is a monotonically increasing function. The grinding wheel motor 24 is a DC motor, and the generated torque τ is proportional to the drive current I.

therefore,

As a result, between the cutting depth C and the drive current I, from the relationship represented by equations (1) and (2),

There is a simple proportional relationship or monotonically increasing relationship indicated by. Therefore, the cutting depth C can be determined from the drive current value I by the grinding wheel 12. Even if the grinding wheel motor 24 is an AC motor such as an induction motor, it is possible to determine the torque τ generated from the drive current I, so basically the cutting depth C is determined by the DC motor as the grinding wheel motor 24. It can be determined from the drive current I in the same way as it is used.

The drive current I supplied to the grinding wheel motor 24 is detected by the detector 26 and the movement of the grinding wheel 12 in the radial direction (X axis) of the roll 2 to the processor 38. Controlled by it, the grinding wheel 12 can be ground to the cutting depth by the preset current while moving the grinding wheel 12 in the axial direction of the roll 2 in order to grind the roll 2. When the drive current I falls below the preset current, the grinding wheel 12 grinds the radial direction (X-axis) of the roll 2 for grinding the roll 2 until the preset current is reached. Move the wheel 12. After reaching the preset current, the movement of the grinding wheel 12 in the axial direction is reversed, and the roll 2 is ground from its end to its collar. By grinding the rolls 2 in this way, the rolls 2, which are prone to local wear during use for a certain period of time, do not program numerical control data due to uneven or worn conditions of the surfaces of the individual rolls 2, Grinding is automatically performed on the less worn parts. Therefore, the roll 2 can be efficiently ground uniformly to the most worn area.

6 and 7 show the movement path of the grinding wheel 12 for grinding the roll 2 in the machining process. In each of Figs. 6 and 7, the roll 2 to be ground is fixedly supported between the headstock 4 and the tailstock 6, and is shown by the main motor 10, as shown in Fig. 1. Rotate at a predetermined speed.

6 shows the roll 2 being more worn at the center and less worn at the opposite end. The grinding wheel 12 starts to grind the roll ₂ from the points P ₁ , P ₂ at the opposite end or collar of the roll 2. The cutting depth C by the grinding wheel 12 in the radial direction of the roll 2 is compared with the driving current I supplied to the grinding wheel motor 24, that is, the current detected by the detector 26. It is set to the memory | storage device 40 of the numerical control apparatus 30 as an in preset current value. 7 shows a truing process for grinding an arched outer periphery convex crown roll that is susceptible to local wear with concave crown rolls. The grinding wheel 12 starts to grind the roll from the center point P ₂ having less wear.

In the truing process, the grinding wheel 12 grinds the roll 2 in the radial direction, from the starting point P ₁ or P ₃ (FIG. 6) or at the starting point P in the axial direction of the roll 2. ₂ ) (figure 7).

Prior to the grinding operation, the grinding wheel 12 moves in the radial direction (X axis) of the roll 2, and when the grinding wheel 12 is connected to the roll 2, the current supplied to the grinding wheel motor 24 To change. By detecting the current supplied to the grinding wheel motor 24 and comparing the detected current with a preset threshold, it is possible to determine whether or not the grinding wheel 12 is in contact with the roll 2. When the grinding wheel 12 contacts the roll 2, the execution of the machining program for moving the grinding wheel 12 toward the roller 2 is stopped, and the next machining program is executed. The amount of radial movement of the grinding wheel 12 displayed at the stage of the interrupted program is canceled.

Then, based on the subsequent program, the grinding wheel 12 is moved in the axial direction (Z axis) of the roll 2 to grind the roll 2. When the grinding wheel 12 reaches the less worn area of the roll 2, the current supplied to the grinding wheel motor 24 is reduced. The direction of movement of the grinding wheel 12 along the axis of the next roll 2 is reversed to continue the grinding operation in the opposite direction. The roll 2 can thus be ground efficiently, without measuring the shape of each roll to be or is being True or preparing a machining program for such a roll.

8 shows a skipping control sequence for switching from the radial movement of the grinding wheel 12 to the axial movement of the grinding wheel 12 during the grinding process.

In step 11, the target current (preset current) value applied to the grinding wheel motor 24 is input as a preset value for executing the truing process, or as a machining command (processing program) such as a grinding wheel contact command. The detector 26 adjusts the drive current supplied to the grinding wheel motor 24 in step 12, and the drive current value from the detector 26 is large with the target current value of the processor 38 in step 13. If the detected current reaches the target current in step 13, the machining program to be executed next is stopped, and the completion state is set in step 14, at which time the remaining movement amount of the grinding wheel 12 is canceled. Then, for example, the next program is executed to move the grinding wheel 12 in the axial direction of the roll 2.

If the detected current has not yet reached the target current in step 13, step 15 checks whether the axis command distribution is completed. Upon completion, the next error state is displayed and the error state is set in step 16. If not complete, the next speed command value is output in step 17, and the machining process from step 12 is continued.

The correction function that the numerically controlled machine tool of the present invention has in order to correct the amount of grinding will be described below.

9 shows the relationship between the elastic deformation amount E of the roll 2 to be ground and the drive current value I supplied to the grinding wheel motor 24. The roll 2 to be ground is primarily elastically deformed in accordance with the pressing force of the grinding wheel 12. The larger the drive current I supplied to the grinding wheel motor 24, the greater the torque generated by the motor 24, and the greater the force that the grinding wheel 12 presses on the roll 2. Therefore, since the roll 2 elastically deforms in proportion to the drive current I supplied to the grinding wheel motor 24, the elastic deformation amount E of the roll 2 is expressed as the following monotonically increasing function. .

E = f (I)... … … … … … … … … … … … … … … … … … … … … … … … … … (4)

10 shows the relationship between the wear rate ΔW of the grinding wheel 12 and the drive current value I supplied to the grinding wheel motor 24. Wear on the grinding wheel 12 is caused by friction between the grinding wheel 12 and the roll 2. As described above, the frictional force θ generated between the grinding wheel 12 and the roll 2 is proportional to the torque τ generated by the grinding wheel motor 24, and this torque τ is in turn a grinding wheel motor. It is proportional to the drive current I supplied to 24. Accordingly, the wear amount W of the grinding wheel 12 is also a function of the drive current I of the grinding wheel motor 24. The wear amount W of the grinding wheel 12 is related to the time that the grinding wheel 12 and the roll 2 press against each other. The wear rate ΔW of the grinding wheel 12 (that is, the rate at which the grinding wheel 12 wears from time t to t + Δτ) is represented by the following function.

W = g (I)... … … … … … … … … … … … … … … … … … … … … … … … … … … … (5)

Therefore, the wear amount W of the grinding wheel 12 is given by integrating the wear rate ΔW over time as follows.

W = Wdt = g (I) dt... … … … … … … … … … … … … … … … … … … … (6)

11 shows a roll grinding process taking the above into consideration. Assuming that the roll 2 has a radius S before grinding, and that the target cutting depth is R shown in FIG. 1, the net cutting depth C has no elastic deformation in the roll 2, If there is no wear on the grinding wheel 12, it will be equal to the target cutting depth (R), so

S-R = S-C.

However, since the net cutting depth C is actually reduced by the elastic deformation amount E of the roll 2 and the wear amount W of the grinding wheel 12,

S-R = S-C + (E + W)

Can be obtained, and the roll 2 cannot be ground to a desired shape.

The elastic deformation amount E of the roll 2 is proportional to the driving current I supplied to the grinding wheel motor 24 (see FIG. 9), and the wear rate ΔW of the grinding wheel 12 is the grinding wheel motor ( It is a function of the drive current I supplied to 24 (see FIG. 10). The wear amount W is determined by the equation as a time integral of the wear rate ΔW. Therefore, assuming that the sum of the elastic deformation amount D of the roll 2 and the wear amount W of the grinding wheel 12 is an error D, the roll 2 has an error D = E generated in the roll grinding process of FIG. By calculating + W, grinding is carried out to a desired shape, whereby the net cutting depth C is smaller than the target cutting depth R, thereby correcting the target cutting depth R with an error D.

As described above with reference to FIGS. 5, 9 and 10, the depth of cut (C), the amount of elastic deformation (E) and the amount of wear (W) are the driving current (I) supplied to the grinding wheel motor (24). Has a predetermined relationship with In this respect, the load current value (driving current value) Im supplied to the grinding wheel motor 24 is detected by the detector 26 shown in FIG. 1, and the elastic deformation amount E and the wear amount W are numerical values. Calculated by the processor 38 of the control device 30, the target cutting depth R is corrected by the elastic deformation amount E and the wear amount W in order to automatically correct the grinding amount of the roll 2. .

12 is a block diagram of a system for correcting the grinding amount of the roll 2. In the roll grinding process, the cutting depth C is reduced due to the wear on the grinding wheel 12 and the elastic deformation of the roll 2. The system includes elastic deformation correction means 52, wear correction means 54 and soft-fish control means 56 of the processor 38 of the numerical control device 30.

Numerical control data for the grinding wheel 12 (indicating the axis and the amount of movement in the radial direction of the roll 2) is given as a command, and the target current value Is for the grinding wheel motor 24 is given this command. It is set based on this. The actual current supplied to the grinding wheel motor 24 is detected by the detector 26 in FIG. 1 as the load current Im.

The elastic deformation correction means 52 calculates the elastic deformation amount E from the target current Is and the actual load current Im as follows.

E = f (Im) = k. I… … … … … … … … … … … … … … … … … … … … (7)

Where k is the elastic deformation correction coefficient of the machine tool and ΔI is the difference between the target current Is and the load current Im. In terms of dead zone, which is a system parameter of the numerically controlled machine tool of the present embodiment, ΔI is determined as follows.

ΔI = IS-Im-δ... … … … … … … … … … … … … … … … … … (8)

Where Im-Is <δ,

I = 0 ... … … … … … … … … … … … … … … … … … … … … … (9)

Where -δ≤Im-Is≤δ

ΔI = Is-Im + δ... … … … … … … … … … … … … … … … … … 10

Where δ <Im-Is

The elastic deformation amount E thus calculated is added to the target cutting depth R. FIG. Similarly, the wear correction means 54 calculates the wear amount W from the target current Is and the load current Im as follows.

W = g (Im) = q.Is.Im... … … … … … … … … … … … … … … … (11)

Where q is the wear compensation factor of the machine tool. The wear rate ΔW is the depth of cut per unit time and corresponds to the speed v at which the grinding wheel 12 grinds the roll 2 in its radial direction. When the roll 2 is ground by the grinding wheel 12 at the speed v, the amount of wear W is the target cutting depth R because the amount of movement of the grinding wheel 12 in the radial direction is an integral of the speed. Is added to. As a result, the cutting depth corrected by the elastic deformation amount E of the roll 2 and the wear amount W of the grinding wheel 12 is applied to the roll grinding step 50 as a command, so that the roll 2 is of a desired shape. Grinding can be done.

The target current value Is, the elastic deformation correction coefficient k and the wear correction coefficient q are set together in the command code in the numerical control program, and the parameters of the input device 46 coupled to the numerical control device 30 are set. It is written by a function and stored in the storage device 40.

The wear correction coefficient q is not necessarily constant because the wear amount W of the grinding wheel 12 changes with the time of the grinding process. More specifically, the wear amount W is determined according to the rotational speed of the grinding wheel 12, the cutting depth thereby, the speed supplied in the axial direction, the shape and material of the roll 2, and other factors. Empirically established for However, when the grinding capability of the grinding wheel 12 is lowered due to its load or peeling of the surface layer of the grinding wheel 12, the above-mentioned wear correction process is not sufficient to correct the cutting depth.

In order to solve this problem, the wear compensation coefficient q is the difference between the target current Is and the load current Im supplied to the grinding wheel motor 24 and the time interval T at which the wear compensation occurs. It is recognized and corrected on the basis of.

More specifically, the wear coefficient recognition command is inserted into the machining program, and the wear correction coefficient q is calculated and corrected at a predetermined time interval of the wear correction means 54 shown in FIG. 12 based on the following equation. do.

q (new) = q (old) = × … … … … … … … … … … … … … … … … (12)

Where α is the recognition coefficient, a parameter unique to the machine tool, and q (new) and q (old) are the current and past wear correction coefficients. The difference ΔI between the currents is calculated through equations (8) to (10), taking into account the dead space δ. When the target current Is and the load current Im are in the dead band, the wear correction factor q (new) remains unchanged. When the target current Is and the load current Im exceed the dead space δ, the wear correction factor q (new) is the amount by which the target current Is and the load current Im exceed the dead zone δ. Change proportionally. At this time, the cutting depth C corresponding to the load current Im greatly changes, and therefore, the wear correction coefficient q is automatically corrected because the amount of wear or the grinding ability of the grinding wheel 12 changes. As a result, the roll 2 can be changed very accurately regardless of how the state of the grinding wheel 12 changes.

The numerically controlled machine tool according to the present embodiment has a function of causing the grinding wheel 12 to grind the roll at a predetermined cutting depth based on the preset current. More specifically, the load current Im supplied to the grinding wheel motor 24 is detected by the detector 26, and the detected load current Im is the preset target current Is by the processor 38. Compared with the grinding wheel 12, the grinding wheel 12 radially grinds the roll 2 at a predetermined speed until the load current Im supplied to the grinding wheel motor 24 reaches the target current Is, As a result, the roll 2 is ground to a predetermined cutting depth. The soft erase means 56 shown in FIG. 12 compares the load current Im detected by the detector 26 with the target current Is, and controls the servo motor 22 to control the grinding wheel 12. In accordance with the difference between these currents, the roll 2 is ground radially at a predetermined speed, thereby obtaining a desired cutting depth C. The soft erase means 56 operates when a command for grinding the roll 2 is included in the machining program based on the target current. If the elastic deformation and wear correction commands are in the same program block as the command for grinding the roll 2 based on the target current, then the elastic deformation and wear correction commands are ignored.

The function of causing the grinding wheel 12 to grind the roll 2 based on the preset current will be described with reference to the flowchart of FIG. First, the numerical control data (the amount of movement of the grinding wheel 12, the target current Is for the grinding wheel motor 24, etc.) in the axial direction and the radial direction of the roll 2) is used to control the grinding wheel 12. Given as a command, the roll 2 is ground in accordance with this command in step 21. The target current Is is given to the processing program or written through the parameter setting function of the input device 46 such as a key board or the display device 48 such as a CRT display and stored in the storage device 40. .

When the target current Is is set and a command for grinding the roll 2 is given based on this target current Is, the soft control means 56 load current supplied to the grinding wheel motor 24. It is operated to compare Im with the target current Is in step 22. If the load current Im is smaller than the target current Is, then the grinding wheel 12 is driven to cut the roll 2 at the speed v indicated by the following equation.

v =-[b / a.Is + c]... … … … … … … … … … … … … … … … (13)

Here, a, b and c are system parameters inherent to the machine tool at steps 23a, 24a, 25a and 26a. If the load current Im is greater than the target current Is, the grinding wheel 12 moves away from the roll 2 at the speed v given in steps 23b, 24b, 25b and 26b by Go to.

v = b / a = Is + c... … … … … … … … … … … … … … … … … … (14)

When the load current Im reaches the target current Is, the instruction for grinding the roll 2 on the basis of the target current is canceled in step 27, and the grinding wheel 12 stops only the roll (in step 28). 2) is moved in the axial direction (Z axis). Next, the grinding wheel 12 reaches a predetermined position in the Z axis direction, and at that time, the movement of the grinding wheel 12 along the Z axis ends in step 29. Thus, the roll 2 is ground using the grinding wheel 12 to a predetermined cutting depth.

The grinding mode according to the illustrated embodiment on the basis of the various combined functions mentioned above will be described below. For example, the grinding mode includes a lateral grinding mode for grinding rollers to realize adaptive control by correcting wear on the grinding wheel and correcting elastic deformation of the roll, and a lateral grinding mode in which an intermediate cutting speed is specified. And a transverse grinding mode that specifies cutting the roll at its opposite end. A specific command code (specific command) is determined for these three transverse grinding modes. On the basis of several predetermined parameters with the selected one of the special instructions, the instructions for performing the various grinding functions mentioned above are enabled to perform the corresponding lateral grinding mode.

14 shows a path for moving the grinding wheel 12 into the lateral grinding mode in which adaptive control is used. In this lateral grinding mode, a target current Is supplied to a grinding wheel motor 24 for grinding the end points P ₁ to P ₃ , given a code indicating a specific command corresponding to the mode (sixth) The same also applies to a parameter indicating the number N of the lateral movement, the staying time t at which the grinding wheel stays at the end of the roll 2 and the speed F supplied to the grinding wheel 12. In response to the specific command code, the wear correction function and the elastic deformation correction function are enabled to grind the rollers in the same way, as indicated by the command code for the individual correction function.

As shown in FIG. 14, the grinding wheel 12 grinds the roll 2 while moving in the axial direction of the roll 2. In the region 1, the grinding wheel 12 moves along the shape defined by the initial setting of the roll 2. In the zone 2, moving in the axial direction (Z axis) of the roll 2, the grinding wheel 12 is operated when the load current Im supplied to the grinding wheel motor 24 reaches the target current Is. The roll 2 is ground in the radial direction (X axis) of the roll 2 until now. Next, in the zone 3, the grinding wheel 12 grinds the roll 2 in the axial direction transversely, while performing wear correction and elastic deformation correction. In area 4, the wear correction factor q is based on the time interval that the wear correction has been made so far and the difference between the target current Is and the load current Im supplied to the grinding wheel motor 24. The grinding process changes to accommodate the amount of wear of the grinding wheel 12 that changes over time. In the zone 5, using the changed abrasion correction factor q, the grinding wheel 12 is moved to the transverse end point, performing wear and elastic deformation correction in the same manner as in the zone 3. In zone 6, the grinding wheel 12 moves along the roll shape defined by the initial setting. The grinding wheel 12 then stays for the stay time t indicated in the area 7. Then, as indicated by regions 1 'through 6 and region 7', movement in regions 1 through 6 and region 7 is transverse to effect lateral grinding. It is repeated by the number N of the direction movement.

FIG. 15 shows the movement path of the grinding wheel 12 to the lateral grinding mode in which the intermediate cutting speed is indicated. Also in this lateral grinding mode, the code indicating the corresponding specific command, the target current Is, the starting point P ₁ to P ₃ , the number N of the lateral movement, the stay time t, The parameters give the feed rate (F) and the intermediate cutting speed (v). In this transverse grinding mode, the grinding wheel 12 rolls at a grinding speed v indicated in the radial direction (X axis) until it reaches the target current Is, before reaching the transverse end point. Grinding). The grinding wheel 12 follows the path indicated by the arrow of FIG. The grinding roll 12 may be shaped by grinding the roll along a defined shape up to its most worn area prior to the grinding process. In the lateral grinding mode, only the function of grinding the roll 2 based on the preset current is executed, while the adaptive control functions such as wear compensation and elastic deformation correction are not performed.

16 shows the movement path of the grinding wheel 12 in the lateral grinding mode in which the grinding wheel 12 grinds the roll 2 at its opposite end. In this transverse grinding mode, the code indicating the Daewoong specific command, the starting point (P ₁ to P ₃ ), the transverse movement number (N), the stay time (t), the feed speed (F) and , Parameters indicating the elastic deformation amount E at the end and the cutting speed v at the end point are given. In this transverse grinding mode, as indicated by the arrow in FIG. 16, the grinding wheel 12 starts traversing in the opposite direction from the current position and moves transversely at the cutting speed V with an elastic deformation amount E. Grind the roll (2) at the opposite end by the marked number (N). When the current position of the grinding wheel is at P ₁ or P ₃ , the marking of the transverse end point may be exempted.

In this lateral grinding mode, no grinding word is performed based on the load current supplied to the grinding wheel motor 24.

In the present invention, as mentioned above, on the basis of the fact that the driving current supplied to the grinding wheel motor and the cutting depth by the grinding wheel have a predetermined relationship, the driving current is detected by the detector, and the cutting made in the roller By controlling the depth and the workpiece by the grinding wheel, the drive current reaches the preset current. The workpiece is ground to the desired shape by repeatedly inverting the movement of the grinding wheel in the axial direction of the workpiece. Therefore, it is not necessary to measure the wear state of the adjusted workpiece and program numerical control data for truing the workpiece. Therefore, the workpiece can be ground very efficiently. By simply setting the cutting depth by the grinding wheel as the driving current supplied to the grinding wheel motor, setting the starting point, and giving a truing command, the area of the less worn workpiece is automatically ground to the desired cutting depth. Can be. The process of the invention is thus more efficient than the process for uniformly grinding the workpiece.

Furthermore, when the drive current satisfies the predetermined comparison state, the control is switched from the current machining program to the next machining program. Thus, how the grinding wheel comes into contact with the workpiece measures the shape of the workpiece or prepares the machining program. Can be detected easily and accurately. Therefore, the direction in which the grinding wheel moves relative to the workpiece can be automatically reversed for more efficient grinding operation.

The present invention is also based on the fact that the load current supplied to the motor to rotate the grinding wheel has a predetermined relationship to the net cutting depth by the grinding wheel and the amount of wear on the grinding wheel. More specifically, the drive current supplied to the grinding wheel motor is detected, and the movement compensation amount of the grinding wheel in the radial direction of the workpiece is calculated from this drive current in correspondence with the amount of wear. This calculated amount is added to the moving target amount so as to compensate for the reduction in the amount of grinding caused by wear on the grinding wheel. Therefore, the reduction in the amount of grinding (cutting depth) caused by the wear on the grinding wheel in the grinding process can be easily compensated automatically. Therefore, it is possible to grind the workpiece very accurately without requiring complicated procedures such as predicting the amount of wear on the grinding wheel or preparing numerical control data for the reduction of the cutting depth due to such amount of wear. Moreover, measurement of roll dimensions, confirmation of dimensional accuracy and repeated grinding operations are minimized in the finishing process, thus increasing the efficiency of the entire process.

According to the present invention, moreover, the difference between the drive current supplied to the grinding wheel motor and the target current is determined at each time interval, and the cutting depth is then corrected based on the wear on the grinding wheel, and the wear correction coefficient is sequentially And the amount of movement of the grinding wheel is corrected based on the corrected wear correction coefficient. Depth of cut is precisely made by automatically correcting the sequential wear correction coefficient according to the amount of wear on the grinding wheel that changes over time in the grinding process.

The present invention is also based on the fact that the load current supplied to the motor for rotating the grinding wheel has a predetermined relationship with the net cutting depth by the grinding wheel and the elastic deformation of the grinding wheel. More specifically, the drive current supplied to the grinding wheel motor is detected, and the movement compensation amount of the grinding wheel in the radial direction of the workpiece corresponding to the elastic deformation amount is calculated from this drive current. This calculated amount is added to the moving target amount to compensate for the reduction in the amount of grinding caused by the elastic deformation of the grinding wheel in the grinding process. Therefore, the reduction in the amount of grinding (cutting depth) caused by the elastic deformation of the grinding wheel in the grinding process can be easily compensated automatically. Therefore, it is possible to grind the workpiece very accurately without requiring complicated processes such as predicting the elastic deformation amount of the grinding wheel or preparing numerical control data for the reduction of the cutting depth due to such elastic deformation amount.

Furthermore, the grinding wheel moves in the axial direction and the radial direction of the workpiece based on a specific instruction, and selectively displays a plurality of operating instructions by parameters in order to grind the workpiece into a desired shape under the instruction made possible by this specific instruction. can do. When grinding the workpiece, one or more commands from the individual grinding functions allow the grinding process to be carried out automatically. Therefore, it is not necessary to prepare complex programs for individual workpieces, and it is possible to set necessary parameters without operator intervention with the result of increasing the efficiency of the grinding process.

Furthermore, by selecting a desired roll shape and simply setting a parameter corresponding to the selected roll shape, the point group data forming the numerical control data can be automatically calculated by a predetermined formula, and according to the calculated point group data The roller can be ground in the roller shape of. Therefore, the grinding process can be performed very efficiently without requiring a complicated process such as selecting a cam according to the shape of the roll and the length of the roll or programming point group data for each roll. Rolls with various curved surfaces can be ground very easily using the numerically controlled machine tools of the present invention.

Although certain preferred embodiments have been shown and described, many changes and modifications can be made to the invention without departing from the scope of the appended claims.

Claims (3)

In a numerically controlled machine tool for grinding a workpiece in a roll shape by rotating the workpiece at a predetermined speed around the axis and moving the grinding machine in the radius and axial direction of the workpiece, the numerically controlled machine tool rotates the grinding machine. Detection means for detecting the drive current supplied to the drive motor, wear correction means for calculating the amount of wear on the grinding machine as the movement compensation amount of the grinding machine in the radial direction of the workpiece based on the detected drive current value, and the wear of the grinding machine. And means for adding the movement correction amount of the grinding machine to the movement target amount so as to compensate for the reduction of the grinding amount. In a numerically controlled machine tool for grinding a workpiece in a roll shape by rotating a workpiece at a predetermined speed around its axis and moving the grinding machine in the radius and axial direction of the workpiece, the numerically controlled machine tool rotates the grinding machine. Detecting means for detecting the drive current supplied to the drive motor, and the elasticity of the grinder produced by grinding the workpiece with the grinding machine in the radial direction of the workpiece as a movement compensation amount of the grinding machine based on the detected drive current value. Elastic deformation correction means for calculating the deformation amount, and means for adding the movement compensation amount of the grinding machine to the movement target amount to compensate for the reduction of the grinding amount due to the elastic deformation of the grinding machine. Control machine tool. A method of controlling the grinding operation of a numerically controlled machine tool for grinding a workpiece in a roll shape by rotating the workpiece at a predetermined speed about its axis and moving the grinding machine in the radial and axial directions of the workpiece, the method comprising Detecting a driving current supplied to the driving motor to rotate the grinding machine, calculating a movement compensation amount of the grinding machine in a radial direction, corresponding to the wear amount of the grinding machine, in the radial direction, based on the detected driving current value; Next, correcting a predetermined time interval and a wear correction coefficient at the predetermined time interval based on the difference between the target current value supplied to the drive motor and the detected drive current value, and sequentially wear correction coefficient To compensate for the movement compensation of the grinding machine and to compensate for the reduction in the amount of grinding of the workpiece due to wear on the grinding machine. And a step of adding this correction amount to the movement target amount.