JP3507871B2 - Numerical control equipment for machine tools - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool for machining a rotating workpiece by cutting a plurality of times, and relates to a numerical control device for a machine tool capable of preventing the life of the tool from being shortened.

[0002]

2. Description of the Related Art Conventionally, when a workpiece is ground by a grinder, for example, first, a machining allowance to be ground is determined, and the machining is performed by making a plurality of cuts with respect to the machining allowance. It was being appreciated. In this case, the cutting start position and the cutting amount in each cutting are set from the stock removal amount, and these are set as the setting values of the NC data. Then, the workpieces having the same shape are always processed by the set values.

[0003]

However, if the cutting start position and the cutting amount are determined only from the machining allowance, the load acting on the cutting tool may not be uniform depending on the shape of the workpiece. That is, for example, when grinding a cam-shaped workpiece W as shown in FIG. 12A, the cam lobe section b and section d are section a and section c.
Larger loads act on the stone. FIG. 12 [B] shows a load acting on the grindstone G when the workpiece W having the machining allowance t is ground by one cut. In the graph of FIG. 12B, the vertical axis represents the load acting on the grindstone G, and the horizontal axis represents the rotation angle of the workpiece W, which corresponds to the sections a to d.

Further, in general, a cast work piece is apt to cause an error in size and shape, and depending on the position of the error portion, a very large load acts on the grindstone G, which shortens the life of the grindstone G. . That is, for example, the stock removal amount t
In the case where the workpiece W of No. 4 is ground by cutting four times, as shown in FIG. 13A, when the error in the section d of the workpiece W (the hatched portion in the drawing) is large, the machining of the workpiece W is performed. When this is done, a load acts on the grindstone G as shown in the graph of FIG. 13B, and a very large load acts on the grindstone G in the section d in the first cut. For this reason, if processing is performed with a small amount of each cut in order to reduce the load acting on the cutting tool, the number of cuts increases and the cycle time of the processing becomes long.

Further, in the casting, lot production is carried out in which a fixed number of pieces are put together to produce the same product, and the cast work piece produced by this casting has an error portion generated when the lot changes. However, the change in the error portion is one of the causes that the load acting on the grindstone cannot be made constant. Therefore, the purpose of the present invention is to secure the conventional cycle time,
Moreover, it is an object of the present invention to provide a numerical control device for a machine tool that processes so as to reduce the maximum load that acts on the cutting tool of the machine tool.

[0006]

The present invention has been made to solve the above-mentioned problems, and a load measuring means 1 for measuring a load acting on a cutting tool of a machine tool for machining a workpiece.
When the load measurement means 1 of the load measured by a maximum load detecting means 2 for detecting a maximum value of the load for each notch process respectively, the maximum load detecting means each incision step adjacent detected by 2 From the relationship between the maximum load and the cutting amount in the cutting process at this time, a cutting data calculation unit 3 for calculating the cutting amount for each cutting that equalizes the value of the maximum load in each adjacent cutting process. Consists of.

Further, in the cutting data calculating means 3, the correction value calculating means 3a for calculating the correction value of the cutting amount for equalizing the value of the maximum load in each of the adjacent cutting steps , and the correction value calculating means. Based on the calculated correction value, each of the preset cuts
And a data correction means 3b for correcting the data of the cutting start position and the cutting amount for each process .

[0008]

First, in order to measure the maximum load in each cutting process , the first workpiece is machined by the cutting start position and the cutting amount which are set values determined from the machining allowance. When the processing is started, the load measuring means 1
The load acting on the cutting tool is measured, and the maximum load detecting means 2 detects the maximum load for each cutting process . Then, the cutting data calculating means 3 calculates the cutting amount and the cutting start position of each cutting process that equalizes the maximum load of each adjacent cutting process from the relationship between the maximum load and the cutting amount of each adjacent cutting process. To do. Then, this cut data calculation means 3
The second and subsequent workpieces are machined based on the cutting amount calculated by.

The above-mentioned correction may be carried out for each work piece, or when a certain condition (number of work pieces, machining time, change of work piece lot, change of cutting tool, etc.) is satisfied. You can go.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cam grinder which is an embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram of the cam grinder of this embodiment. This cam grinder consists of two main parts, one is the grinder body 10 and the other is
It is a numerical controller 30 for controlling this grinder.

A grindstone base 12 and a table 14 are placed on a bed 11 of the grinder main body 10. Whetstone stand 12
Is movably supported on the bed 11 in the X-axis direction,
The grindstone 12 is moved in the X-axis direction by driving an X-axis servomotor 17 provided in the bed 11 via a screw mechanism (not shown). This grindstone 12 has a grindstone G
Is rotatably supported, and the whetstone G is rotated by the whetstone base 1
It is designed to be performed by a grindstone driving motor 13 fixed to 2.

The table 14 is supported by the bed 11 so as to be movable in the Z-axis direction orthogonal to the X-axis.
The table 14 is moved in the Z-axis direction by driving a Z-axis servomotor 18 provided in No. 1 via a screw mechanism (not shown). A headstock 15 and a tailstock 16 are provided on the table 14, and a workpiece W is detachably held between them. Then, the spindle 23 is rotated by the servomotor 21 for spindle rotation provided on the spindle stock 15.
To rotate the workpiece W. In addition,
The workpiece W is a camshaft used in an automobile engine.

The numerical controller 30 comprises a CPU 31, an interface 32 and a memory 33. The interface 32 is connected to an X-axis drive device 19 for controlling the drive of the grindstone 12, a Z-axis drive device 20 for controlling the drive of the table, and a C-axis drive device 22 for driving the spindle 23. Further, the interface 32 is connected to a current measuring device 21 that measures the current of the grindstone driving motor 13 and outputs it as a digital signal. Then, by measuring the current of the grindstone driving motor 13, the power of the grindstone driving motor 13 is calculated, and this is used as the workpiece W of the grindstone G.
It is the load received from.

In the memory 33, a machining operation program 33a for driving the grinder and NC data 33e,
Although details will be described later, a maximum load detection program 33b, a correction value calculation program 33c, and a data correction program 33d, which are features of this embodiment, are stored. Next, the operation of the grinding machine of this embodiment will be described based on the flowchart of FIG.

First, in step 101, the workpiece W is removed.
Cut start position and cut for each cut from the algebra
Determine the amount. FIG. 3A shows the cam part of the workpiece W to be processed.
FIG. 3B shows a cross-sectional shape of a portion of FIG.
FIG. Now, four incisions (hereinafter, first to fourth)
The process of grinding the workpiece W by
To do. S for the stock removal amount t of the workpiece W,₁~ S_FourIs each worker
Is the cutting start position in₁~ D_Four
Is the cut amount in each cut. This notch
Amount D₁~ D_FourCan be set according to the workpiece W, but the book
In the embodiment, D₁= D₂= D₃= D_FourI am trying.
Then, the cutting start position S₁~ S _FourAnd notch
Amount D₁~ D_FourIn the memory 33 as NC data 33e
Set. At step 102, the first workpiece W is
It is attached to the grinder 10 and the above NC data is obtained in step 103.
Grinding is started according to 33e. In Figure 3 [B]
As shown, the rotation of the workpiece W and the combined movement of the grindstone 12
More arrow F₁Grind so that the grindstone G moves in the direction of
It That is, the workpiece W is rotated and the grindstone 12 is advanced.
Retreat and cut the grindstone G into the workpiece W,
The depth of cut of G for the workpiece W is D₁When you reach (rank
Table E₁), After that the depth of cut is D₁To be constant at
The cutting start position S of the second step₂Cut to the first
Complete the process cuts. Hereinafter, similarly, the second, third,
Make a cut in the 4th step and complete the cut in the 4th step
After that, with the depth of cut set to D4, position E_FourGrinding
Move the stone and finish the grinding process. This first mentioned above
Machining of the workpiece W is done by measuring the maximum load at each cut.
This is a process for setting.

During the grinding process, each step is performed by step 104.
The maximum load at is detected. Detection of this maximum load
Is applied to the grindstone driving motor 13 by the current measuring device 21.
Maximum current detection program 33b
From the current value input by
The power is calculated, and the value of this power is the value of the load applied to the grindstone G.
The maximum value in each process is stored as
It FIG. 5 shows the action on the grindstone G during cutting in the first to fourth steps.
6 is a graph showing a load to be applied. This graph has a horizontal axis
Rotation angle of crop W, negative acting on grindstone G in the upward direction of the vertical axis
The amount of cut is shown in the downward direction of the load and the vertical axis. Na
The maximum load value in each process is P₁~ P _FourIs.

In step 105, the machining of the first work W is completed, and in step 106, the correction value of the cutting amount in each process is calculated by the correction value calculation program 33c. The concept of calculating the correction amount of the cutting amount is to reduce the cutting amount in the process with a large maximum load and to increase the cutting amount in the process with a small maximum load to offset the cutting amount. The maximum load in each working step is made uniform, and the maximum load in the entire processing is reduced. here,
A method of calculating the correction values Δd _{1 to} Δd ₃ will be described in detail with reference to FIGS. 6 and 7. Now, to simplify the explanation,
It is assumed that the change in the load of each process changes as shown in FIG.

FIG. 7 shows a setting value cutting start position S.₁~ S
_FourAnd depth of cut D₁~ D_FourAnd cut after correction
Only start position S₁’～ S_Four'And the depth of cut D₁’～ D
_FourIt is the figure which contrasted and showed. As shown in FIG.
Correction value Δd you want to obtain₁~ Δd ₃Is the maximum of each adjacent process
This is the correction amount that makes the large load the same (average),
Correction value Δd₁Is           Δd₁= (P₂-P₁) × D₂/ 2P₂          ... (1) Is calculated by Generalizing this,           Δd_i= (P_{i + 1}-P_i) × D_{i + 1}/ 2P_{i + 1}    ... (2) Becomes However, P_iIs the maximum load of i process
Yes, i = 1, 2, 3 ,. ． ． , N-1 where n is a notch
The number of steps. From the above equation, the correction value of the second step
Δd₂And the correction value Δd in the third step₃Is calculated.

Then, in step 107, the cut start positions S ₁ 'to S ₄ ' and the cut amounts D ₁ 'to D ₄ ' after correction in each process are calculated from the calculated correction values Δd _{1 to} Δd _3. It The calculation of each value is calculated by the formula described later, and the cut start position S _i 'of the i-th step is calculated.
Is S _i '= S _i + Δd _i-1 (3) where i = 1, 2, 3 ,. ． ． , N, where n is the number of cutting steps and Δd ₀ = 0.

Further, the cut amount D' _i in the i-th step is when i = 1, D ₁ '= D ₁ + Δd ₁ (4) i = 2, 3 ,. ． ． , N−1 D _i ′ = D _i + Δd _i −Δd _i −1 (5) When i = n D _n ′ = D _n −Δd _n−1 (6) where n Is the number of cutting steps.

[0021] Notch opening in each process from the above formula
Start position and cut amount are data correction program 33d
Calculated in step 108, the NC data 33e
To change. Fig. 8 shows the load acting on the grindstone G at this time.
The format is the same as in FIG. Then, in step 109
The corrected cutting start position S ′.₁~ S ' _FourOh
And cut amount D '₁~ D ’_FourBy the second
The workpiece W is processed. The load detection described above is the first
Perform only on the second work piece, and add to the second and subsequent work pieces.
According to the corrected cutting start position S'and the cutting amount D '
It may be processed in a form that
May be detected and corrected each time. Furthermore, lot unit
Since the error at the time of casting of the workpiece changes with
You may go in. Do not change the stock removal t like this.
The cutting position S'and the cutting amount D'of each process are changed.
It is possible to reduce the maximum load on the grinding wheel G
it can.

Next, a modified example of the present invention will be described based on the flowchart of FIG. Steps 201 to 205 in FIG. 9
Up to are the same as steps 101 to 105 in FIG. The difference is that in step 206, the correction values Δd _{1 to} Δd ₃ of the cutting amount are calculated by the above-described formula (2), and in step 207, the cutting start positions S ′ _{1 to} S ′ ₄ and the cutting amount in each cutting are calculated. D' ₁ ~ D '
₄ is calculated by the equations (3) to (6). Next, at step 208, it is judged whether or not the number of correction calculations has reached a preset number. Then, when the number of times of the correction calculation reaches the set number, step 2
The process proceeds to step 09, and if not reached, the process proceeds to step 212.

When the process proceeds to step 212, the predicted maximum load which is the maximum load of each process predicted from the corrected cutting start positions S ₁ 'to S ₄ ' and the cut amount D' _{1 to} D' _{4 of} each process. to calculate the P ₁ '~P _4'. The predicted maximum loads P ₁ ′ to P ₄ ′ are calculated by the following equation. P _i ′ = P _i × D _i / D _i ′ (7) where i = 1, 2, 3 ,. ． ． In n, n is the number of steps.

Then, in step 214, the maximum load P
_The values of the predicted maximum loads P ₁ ′ to P ₄ ′ are respectively substituted into _{1 to} P ₄ , the process proceeds to step 106, and the same steps are repeated thereafter. FIG. 10 shows the load acting on the grindstone G in the same format as in FIG. The broken line in the figure indicates the first workpiece W.
Is the load that acts on the grindstone G when it is machined, and the practice is the load that acts on the grindstone G when the second and subsequent workpieces W are machined after performing the above-described correction calculation n times. However, a ^{_{S 1 n ~S 4 n, D}} 1 n ~D 4 n and maximum load.

On the other hand, the transition to step 209, the corrected cut start position S _'1 ~S' ₄ and cutting amount D _'1 ~D' ₄ changes the NC data 33e.
At step 109, the next workpiece W is held and the process proceeds to step 103. As described above, in the present modification, since the cut start positions S ′ _{1 to} S ′ ₄ and the cut amounts D ′ _{1 to} D ′ ₄ of each process are corrected a plurality of times, the maximum load of each process is more accurately uniform. Can be made into a grindstone by this
There is an advantage that the maximum load acting on can be reduced.

In the above two embodiments,
The correction amount is calculated so that the maximum loads of the adjacent processes are the same, but the correction value Δd is set in advance to a predetermined constant, and the correction is made to the cutting amount simply by the maximum load of the adjacent processes. The correction may be performed only by increasing or decreasing the value Δd. Instead of calculating the correction value Δd, the cut amount directly corrected may be calculated from the ratio between the maximum load of each process and the cut amount at this time.

Further, as described above, the workpiece W of this embodiment is
As shown in FIG. 3B, the means for grinding the workpiece
Make a cut while rotating W to a predetermined cut amount
When it reaches, the following cutting amount will be kept constant.
However, especially the grinding method is selected.
No way. For example, as shown in FIG. 11, rotation of the workpiece W
With the grindstone G stopped, the cutting start position of the first process is started with the grindstone G.
Setting S₁To the first cut amount D₁(Cutting and opening of the second process
Start position S₂Notch) and then the rotation of the workpiece W
Due to the combined movement of the whetstone base 12 with the forward / backward movement,
Grinding amount D on the outer circumference ₁Grind with. The workpiece rotates once, and the grindstone
The tip is the cutting start position S in the second step₂When you reach
The rotation of the workpiece is stopped and the workpiece W is
Depth of cut D₂Cut in. As with the first step,
Due to the combined movement of rotation and forward / backward movement of the grindstone 12,
Grind the outer circumference. Similarly, perform the third and fourth steps of grinding.
You can use any means.

[0028]

Machine tool numerical controller of the present invention as described above, according to the present invention, among the maximum load in each incision step, correcting the relationship between the maximum load and cut amount at this time of the cut step adjacent The following effects can be obtained by calculating the cutting amount for each cutting process . That is, the conventional machining cycle time can be secured because the number of cuts with respect to the machining allowance does not increase. The maximum load that acts on the tool in each cutting step is made uniform, and the maximum value of the load that acts on the cutting tool can be minimized throughout the machining. Further, even if the above-mentioned correction is not always performed on the workpiece, it is sufficiently effective only when the lot of the workpiece is changed or when the tool is replaced, and the life of the tool can be prevented from being shortened.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a complaint.

FIG. 2 is an overall configuration diagram of a grinder showing an embodiment of the present invention.

FIG. 3 is a diagram showing a shape of a workpiece in the present embodiment.

FIG. 4 is a flow chart showing the operation of this embodiment.

FIG. 5 is a graph showing a load applied to a grindstone.

FIG. 6 is a graph showing a simplified load applied to a grindstone.

FIG. 7 is a diagram showing a cutting position and a cutting amount before and after correction.

FIG. 8 is a graph showing a load applied to a grindstone after correction.

FIG. 9 is a flowchart showing the operation of the modified example.

FIG. 10 is a graph showing a load applied to a grindstone of a modified example.

FIG. 11 is a view showing a grinding means.

FIG. 12 is a diagram showing the relationship between the shape and load of the workpiece and the incision.

FIG. 13 is a diagram showing the relationship between the shape and load of the workpiece and the incision.

[Explanation of symbols]

10 cam grinder 13 Wheel drive motor 21 Current measuring device 30 Numerical control device W work P, P'maximum load S, S'cut start position D, D 'depth of cut Δd Cut amount correction value

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Claims (2)

(57) [Claims] 1. A plurality of incisions are made by rotating a workpiece.
In the machine tool for machining the workpiece according to the process, each of the cuts among the load measuring means for measuring the load acting on the cutting tool of the machine tool for machining the workpiece and the load measured by the load measuring means. maximum a load detecting means, the maximum load that the cuts step adjacent detected by the detecting means for detecting the maximum value of the load for each step respectively
From the relationship between the maximum load and the cutting amount in the cutting process at this time, a cutting data calculation means for calculating the cutting amount for each cutting process for equalizing the value of the maximum load of the adjacent cutting processes. A numerical control device for machine tools characterized in that it is equipped. 2. The cutting data calculation means according to claim 1, wherein a correction value for calculating a correction value of a cutting amount that equalizes the maximum load value of each of the adjacent cutting processes. And a data correction unit for correcting preset cutting start position and cutting amount data for each cutting process based on the correction value calculated by the correction value calculating unit. A characteristic numerical control device for machine tools.