JPH0521702B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an NC machining method for an NC machine tool.
In particular, it relates to an NC machining method that corrects machining errors that occur when NC machining is performed by multiplying position command data of an NC machining program by a scaling factor.

[Prior art and problems to be solved]

When performing scaling processing by multiplying the NC machining program of an NC machine tool by a scaling factor for enlargement or reduction, if the NC machining program has been programmed by digitizing the workpiece shape, the workpiece shape must be scaled and cut. It would be possible to offset and perform NC machining, but when the shape is a solid shape with a three-dimensional free-form surface, current NC equipment has problems with calculation speed, making it difficult.

On the other hand, if the NC machining program is programmed with the cutter center locus, scaling can be performed by multiplying the position command data by the scaling factor, but if the NC machining program includes the cutter radius, Because there is
As long as cutters of the same size are used, the scaling factor will not be applied to the radius of the cutter, resulting in the problem that the workpiece shape will not be processed with the desired scaling factor. In other words, this results in machining errors for a correct workpiece shape.
However, a three-dimensional NC with a three-dimensional free-form surface
Since the machining program is a cutter center locus program, as described above, even if scaling is performed, a correct three-dimensional curved surface shape of the desired scale cannot be obtained. That is, when performing NC machining of many workpieces such as molds that include three-dimensional free-form surfaces, there is a drawback that the correct workpiece shape cannot be realized even if scaling machining is performed. Therefore, the present invention aims to eliminate such drawbacks.

[Solution]

In view of the above-mentioned object of the invention, the present invention uses the same NC machining program to correct machining errors when NC machining is performed by multiplying the NC machining program programmed with the cutter center trajectory by a scaling factor. , re-machining by offsetting the amount expressed by the function of the used tool diameter D and the scaling factor k in the direction in which the position of the machining start point is scaled so that the position of the tool and workpiece moves relative to each other. It provides a machining method, and more specifically, in the NC machining method of an NC machine tool, after a workpiece is NC-machined with an NC machining program in which the tool center trajectory is programmed as numerical information, the same NC machining program is used. , so that the positions of the tool and workpiece move relatively, the amount D/2 (k-1 ) is offset and re-machined to correct the error of scaling machining.In addition, the position command data based on the NC machining program is interpolated in the information processing unit, and the movement command data of each feed axis of the NC machine tool is calculated. , multiply the travel amount of each feed axis by the desired scaling factor independently for each feed axis, create movement command data of an independent scale for each feed axis, and multiply the movement command data by the desired scaling factor for each feed axis. Transmitted to the servo mechanism of the NC device
After NC machining, using the same NC machining program, the position of the machining start point is moved in the scaled direction using the tool diameter D and the scaling factor so that the positions of the tool and workpiece move relative to each other. The present invention provides an NC machining method that corrects errors in scaling machining in which the amount D/2 (k-1) expressed as a function of k is offset and remachined. Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

〔Example〕

Figure 1 is applied to the implementation of the NC machining method for correcting errors in scaling machining according to the present invention.
A schematic mechanical diagram showing an example of an NC processing device, Figure 2 is a high-speed NC in the NC processing device shown in Figure 1.
FIG. 2 is a block diagram showing the configuration of a high-speed NC data creation device that performs arithmetic conversion processing of machining data.

Now, the high-speed NC machining equipment shown in Figure 1 is
A device 10, a buffer memory means 12 for storing NC machining data that is separate from or attached to the NC device 10, an NC machining program supply device 14 that supplies an NC machining program, and an NC machining program supplied from the NC machining program supply device 14. A high-speed NC machining data creation device 16 that calculates and converts predetermined NC machining data into machining data for high-speed NC machining according to a high-speed machining command from a program, whose operation is controlled according to NC machining command data from the NC device 10. It is configured to include a servo mechanism 18 (including X-axis, Y-axis, and Z-axis motors), etc.

The above-mentioned NC machining program supply device 14 is
For example, it may be configured using a well-known automatic programming device, a host computer, a floppy device, etc., and an NC machining program that is preprogrammed according to a design drawing for a workpiece to be machined by an NC machining mechanism (not shown). It supplies and sends out. Then, this NC machining program supply device 14 and high-speed NC machining data creation device 16
is connected by an interface means 20, and similarly a high-speed NC machining data creation device 16.
and the above-mentioned buffer memory means 12 are also connected by a similar interface means 22.

The NC machining program supplied from the NC machining program supply device 14 includes both an NC machining command to perform NC machining in normal or standard speed mode and an NC machining command to perform NC machining in high speed mode. It is now being supplied one after another in well-known block units. At this time, the third
As shown in the NC format in the figure, when transitioning from standard NC machining to high-speed NC machining, the high-speed NC
When scaling is performed during the machining process,
A scaling multiplication command (hereinafter referred to as scaling command) is included in advance. Then, for example, the start of high-speed NC is commanded in advance at the NC programming stage using the preparation function G05.

Of course, high-speed processing can be performed externally depending on the progress of machining.
An external operation means that can command NC machining may be provided.

When the NC machining program including the scaling command and the high-speed NC machining command G05 is thus supplied, the high-speed NC data creation device 16 receives the NC machining program at the data receiving section 24 shown in FIG. The data receiving unit 24 receives the high-speed NC data processing unit 26a in the next stage data processing unit 26 according to the presence or absence of the high-speed machining command G05 for each block of NC command data of the NC machining program.
or by bypassing the high-speed NC data processing section 26a to send the NC command data to the data transmission section 28.
Send to. Now, when in high speed mode, that NC
The command data is subjected to interpolation calculations and the like in the high-speed NC data processing section 26a, and is converted into a binary data movement command (number of distributed pulses) that can be directly supplied to the servo mechanism 18 of the NC device. Further, as a feature of the present invention, when a scaling command is included, the scaling calculation unit 26b multiplies the above-mentioned binary data movement command by a desired scaling factor specified for each feed axis, and calculates each Forms a scale movement command independent of the feed axis. That is, for example, in the NC format scaling command shown in Figure 3, the values indicated by △ in the X-axis direction, the values indicated by □ in the Y-axis direction,
In the Z-axis direction, the scaling calculation unit 26b multiplies the values for each axis by different magnification values, such as the values indicated by circles. When there is no scaling command, the processing does not go through the scaling calculation section 26b.

On the other hand, in the normal speed mode, the NC command data is directly sent from the data receiving section 24 to the data transmitting section 28. What should be noted here is that the NC command data for high-speed NC machining is used when attempting to obtain a smooth machined curved surface by performing NC machining at every minute interpolation distance, such as when processing a three-dimensional curved surface shape. NC machining for each minute interpolation distance is performed 3 times in a row.
If the arithmetic processing is performed in the NC device 10 as usual to obtain the dimensional curved surface, the arithmetic processing takes a lot of time, and high efficiency of automatic processing by NC machining cannot be achieved. That is, high-speed NC
The data creation device 16 creates data that can be sent directly to the servo mechanism in the NC device 10 at high speed in advance using arithmetic processing means separate from the NC device 10.
It has an external function that makes it possible to omit all offset processing and interpolation processing using 0. All NC command data transmitted from the data transmitter 28 of the high-speed NC data creation device 16, both scaled and unscaled data, is stored in the buffer memory means 12 via the interface 22, and from there is further transmitted to the NC device. 10 are sent one after another. The buffer memory means 12 has the function of temporarily storing all NC command data including NC machining command data created at high speed, and sequentially transmitting it to the subsequent NC device 10.

In addition, the operation panel 30 is connected to the high-speed NC data creation device 16, and as mentioned above, the high-speed NC processing command
In addition to G05, it is also possible for a person to apply a high-speed NC machining command, and it is also possible to change the feed rate using commands in the NC program.

In the high-speed mode, the NC device 10 reads high-speed NC machining data that has already been converted into movement command data for each axis from the buffer memory means 12 at fixed time intervals, and immediately transfers the data to the servo mechanism 18 as described above.
According to this, high-speed NC machining is executed. In addition, in the case of normal speed mode (standard NC machining mode), the NC machining data is
After undergoing necessary processing such as offset processing, linear interpolation processing, and circular interpolation processing in the arithmetic processing section in 0, the data is sent to the servo mechanism 18 as movement command data for each axis, and by the functions of a normal NC device,
NC machining is performed. In that case,
Even in the normal standard NC machining mode, a scaling calculation unit may be provided in the NC device 10 after the above-mentioned calculation processing unit, and the scaling factor may be multiplied by the amount of movement of each feed axis. Also, the first
As an example different from the example of the configuration shown in FIGS. , the data receiving section receives position command data based on the NC machining program from the NC program supply means 14, identifies whether it is high-speed NC machining mode or standard NC machining mode, and performs high-speed processing in the same way as described above depending on the mode. N.C.
Data processing to perform machining or standard NC machining
This can be executed within the NC device 10, and in each mode, the movement command for each axis can be multiplied by a scaling factor according to the scaling command, and then sent to the servo mechanism 18. In other words, the scaling command can be executed regardless of whether high-speed NC machining or standard NC machining is being performed.

On the other hand, in NC processing, the servo mechanism 18,
Due to the fact that NC machine tools have mechanically operating parts such as feed mechanisms, the higher the commanded speed by the NC command, the slower the follow-up of these mechanical parts, or droop, occurs, and the machining path that is commanded, especially at corners, is delayed. Errors occur. Therefore, even when performing high-speed NC machining using high-speed NC machining data for forming movement command data calculated and converted by the high-speed NC data creation device 16 mentioned above,
The NC device 10 allows high-speed NC machining, especially along a corner path, high-speed NC machining at an inflection point,
When performing high-speed NC machining of a path with a large curvature such as a circular arc, errors due to the droop described above occur and machining accuracy decreases, so it is necessary to prevent this as much as possible. Therefore, the present applicant has already disclosed in Japanese Patent Application Laid-Open No. 63-26707 an invention for preventing the occurrence of errors due to droop. Then, control is performed to reduce the feed speed of each axis on the NC machine tool side (usually, in the technical field of machine tools, three axes, the X-axis, Y-axis, and Z-axis, which are orthogonal to each other are used). This prevents errors caused by droop. That is,
In the high-speed NC data creation device 16, for the vectors indicating the minute interpolation straight lines commanded by each block of the movement command data on the path of the corner portion described above, the difference between the vectors of two adjacent blocks before and after Angular displacements are calculated one after another, and movement command data is created to reduce the feed rate according to the magnitude of these angular change rates.

In general, feed rate control in NC machining involves increasing or decreasing the amount of movement given at one time (pulse distribution number) in a control method that provides movement command data to the servo mechanism at fixed time intervals. It is done by certain things. for example
Assuming that movement command data is given at 10 millisecond intervals, if the amount of movement given at one time is 0.5mm, the feed rate will be 3000mm/min, and if the amount of movement is 0.1mm.
If it is set to 600mm/min.

On the other hand, referring to Figure 4, which shows vectors of minute interpolated straight lines for each block when performing high-speed NC machining using linear interpolation, the angular displacement between vectors A and B of adjacent front and rear blocks in the same figure can be seen. According to the inner product theorem, θ can be found from the relationship cos θ=A・B/|A|・|B|. Depending on the change in angle of this θ from 0 to 90°, for example, when it is around 0°, the amount of movement given at one time is the amount corresponding to the command speed, and as θ becomes larger, the amount of movement is divided. If the feed speed is applied several times, the feed rate is reduced, and as a result, errors due to droop can be minimized when performing high-speed NC machining.

Now, referring to Fig. 5, the information processing section interpolates the position command data based on the NC machining program to create movement command data for each feed axis of the NC machine tool, and the amount of movement of each feed axis. By applying the NC machining method that performs NC machining by multiplying each feed axis by the desired scaling factor independently and creating independent scale movement command data for each feed axis, the X-axis and Y-axis in feed axis
An example of the relationship between the tool trajectory (cutter path) and the shape of the workpiece is shown when NC machining is performed with scaling applied to the axes. In Figure 5,
The diameter of the cutter is D. This is a case where approximately square linear shape machining is performed on the workpiece by NC machining, and the cutter path T1 is normal NC machining where the scaling factor is 1 and no expansion or reduction is performed. At this time, the workpiece has a shape indicated by workpiece shape W1. On the other hand, the cutter path T2 is a case where NC machining is performed by commanding a scaling factor of 1.5 times for both the X-axis and the Y-axis, so that the workpiece has an enlarged workpiece shape W2. This shows how the shape has been processed. Here, the point to note is that the cutter path T1
It is true that the above 1.5 times scaling is achieved between and the cutter path T2, but the workpiece shape W
1 and the workpiece shape W2, 1.5 times scaling is not performed.

Figure 6 shows the tool path () when the same NC machining method using scaling is applied to an NC program for NC machining of a circle, with enlargement scaling applied only to the X-axis of the feed axis of the NC machine tool. This shows the relationship between the cutter path) and the shape of the workpiece. In this case, the NC format indicates a scaling command (SCALE
1024 Z 1024) is programmed. A numerical value (***) is written such that the scale factor of the X-axis is k. Note that scaling is a multiplication factor multiplied by the amount of movement of each axis per unit time (for example, 10 msec), and is given so that ***/1024 becomes k, and the remainder after dividing by 1024 is stored in the memory of the scaling calculation unit. and sends the quotient to the servo mechanism 10 of the NC device 10. Then, calculate the next amount of movement in the same way to find the quotient and remainder, add the remainder stored in the memory last time to this remainder, and if a carry corresponding to the minimum amount of movement is obtained, add 1 to the quotient. A calculation means is used to prevent a large error from occurring in the desired shape due to an accumulated error in the amount of movement due to cutting off the remainder.

Now, Figure 6 shows a program for NC machining of a circular arc shape using circular interpolation using a cutter with radius r.
It shows the relationship between the cutter path and the workpiece shape when elliptical NC machining is achieved by multiplying by a scaling factor of k times only in the axial direction.
In this case, cutter path T3 and workpiece shape W3
This is the case of normal arc-shaped NC machining where the scaling is 1.0 times on each axis.On the other hand, the cutter path T4 and the workpiece shape W4 are always multiplied by the scaling factor k only in the X-axis direction. This indicates that an ellipse is formed. In other words, the cutter with radius r is cutter path T with radius b
When performing NC machining of an arc via 3, X ² + Y ² = b ² ...(1) Here, considering the case where the X-axis movement amount X' is multiplied by the scaling factor k, the When the amount of movement is multiplied by 1/k, that is, 1/k・
When X′ is substituted for X in equation (1), equation (1) becomes (X′/k) ² +Y ² =b ² …(2) That is, (1/kb) ² X′ ² +Y ² /b ² = 1 (3) Therefore, if a = kb, then X' ² /a ² +Y ² /b ² = 1, and it can be seen that an elliptical shape is essentially obtained.

The cutter path T4 and workpiece shape W4 in FIG. 6 indicate an elliptical shape that has been NC-processed in this way. Of course, when the workpiece shape W4 is a cutter with a radius of r, it is a pseudo-elliptical shape that extends by an amount r inside the cutter path T4, so it contains an error with respect to the true elliptical shape. It is. Moreover, in this case as well, the cutter path T
3 and the cutter path T4 are in a relationship multiplied by the scaling factor k, but the workpiece shape W3
The same cutter (diameter
2r), there is no relationship multiplied by the scaling factor k. Therefore, in the present invention, when multiplied by the scaling factor,
This provides an NC machining method that can obtain a workpiece shape that is scaled by the scale factor of the original program shape. Of course, since scaling is performed by multiplying each axial feed direction by an independent desired scaling factor, there is not necessarily a similar relationship between the original program shape and the scaled shape due to enlargement or reduction.

The present invention uses an NC machining program to machine a workpiece using an NC machining program.
After machining, the position of the cutter and workpiece is moved relative to each other using the same NC machining program, so that the position of the machining start point is scaled in the direction expressed as a function of the tool diameter D and the scaling factor k. The workpiece is then NC-machined again by offsetting the amount D/2(k-1), and since the same cutter is used, the cutter diameter is not scaled. Corrections are made.

Figure 7 shows the cutter path T3 shown in Figure 6.
The workpiece shape W4 obtained when performing NC processing by multiplying the scaling factor k only in the X-axis direction and following the elliptical path of the cutter path T4.
Then, cutter diameter D (radius r=D/2)
and the quantity r expressed as a function of the scaling factor k
This shows the principle of re-machining (k-1) by offsetting it in the X-axis direction at the position of the machining start point. 7th
In the figure, when performing NC machining on a circular arc with radius b using circular interpolation, if the NC machining is performed by multiplying the scaling factor k only in the X-axis direction, points P2 and P4 at 90 degrees and 270 degrees from the machining starting point P1 Then, (b
−r). However, in the actual workpiece shape W4, the length is (kb-r) at a point P2' corresponding to the point P2, for example. Therefore, the difference between point P2 and point P2' is r(k-1). Therefore, by offsetting this r(k-1) at the machining start point in advance,
After the NC machining of the workpiece shape W4, the NC machining is performed again. Note that re-machining by offset requires offsets to the left and right sides of the machining start point P1 in the X-axis direction at points P2 and P4, respectively, and re-performs NC machining. The workpiece shape is shown as W5. In addition, in FIG. 7, from A1 to A
4 shows the position of the cutter at each point P1, P2, P3, and P4 when the cutter is offset to the right at the processing start point P1, and B1 to B4 indicate the position when the cutter is offset to the left at the processing start point P1. The position of the cutter at each point P1, P2, P3, and P4 is shown. Since the corrected workpiece shape W5 is in an elliptical shape at least in terms of the major axis and the minor axis, it can be seen that the workpiece shape W5 is closer to an elliptical shape than the workpiece shape W4.

However, if we strictly examine the trajectory of each point on the outline of the workpiece shape W5, as shown in FIG.
In the offset method, the true ellipse shape E1 is cut into a shape shown by the approximate ellipse E2 at points other than the major axis and minor axis, and furthermore,
It is impossible to avoid residual errors. This means that if the same cutter is used and the machining start point is simply offset, the cutter TL will not be the cutter TL1 that circumscribes the ellipse E1, but will be the approximate ellipse E2.
This is because the result is the same as that obtained by cutting with cutter TL2, which is circumscribed by . Therefore, the present invention further provides a method that, after the first NC machining by scaling the workpiece, when the cutter is offset at the machining start point and the NC machining is performed again, the cutter diameter is changed and the machining is performed. It is something to do.

Figure 9 shows how to change the cutter diameter and try again.
By performing NC machining, the approximate ellipse E3 becomes closer to the true ellipse E1, and the workpiece shape can now be regarded as a completely normal desired ellipse shape. There is. Here, in the example of FIG. 9, the approximate ellipse E2 of FIG.
However, considering that the cutter is biting inward from the true ellipse E1, the cutter diameter is changed to the smaller diameter side when re-NC machining. Of course, if it is more advantageous to change to a cutter with a larger diameter as necessary, the cutter can be changed to a larger diameter cutter.
The amount of cutter offset at the machining start point when the cutter diameter is changed is clear from the illustration in Figure 9, but since it does not change the tool center trajectory, the cutter offset used for the initial NC machining is Needless to say, it is D/2(k-1) determined from the diameter D.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, first, even though cutters of the same size are used, the diameter of the cutter is also multiplied by a scaling factor. In order to produce cutting effects, an offset amount is given at the start point of machining and re-NC machining is performed, so the effect of achieving NC machining of a workpiece shape that is extremely close to the desired workpiece shape and with few errors can be achieved. With,
Furthermore, by changing the cutter diameter at the stage of offset and re-NC machining, it is possible to achieve NC machining of the workpiece shape with even fewer errors in relation to the truly desired shape. The effect can be obtained. Therefore, the same NC
When performing NC machining by multiplying each axis direction by a desired and independent scaling factor based on the machining program, the desired workpiece shape is planned from the original workpiece shape, and the shape is approximately equal to the planned workpiece shape. It is possible to perform NC processing to obtain the shape.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of one embodiment of an NC processing device suitable for carrying out the NC processing method according to the present invention;
Fig. 2 is a block diagram showing the configuration of the high-speed NC data creation device shown in Fig. 1, Fig. 3 is a diagram showing an example of the format of an NC program including a scaling command, and Fig. 4 is a block diagram showing the configuration of the high-speed NC data creation device shown in Fig. 1. Diagram 5 explaining the angular displacement of a vector representing a minute interpolation straight line commanded by successive blocks.
The figure is a diagram explaining an example of performing linear NC machining on a workpiece by multiplying the same scaling factor in the two axes directions of the X and Y axes. Figure 6 shows one of the X A diagram for explaining an example of performing elliptical machining by multiplying the scaling factor k in the axial direction, and Figure 7 is the same NC according to the present invention.
Figure 8 is a diagram explaining the principle of re-NC machining after giving an offset to the tool at the machining start point using a machining program. Figure 8 is a diagram explaining the minute error remaining in the NC machining method of Figure 7. FIG. 9 is a diagram illustrating how error correction can be achieved more effectively by changing the tool diameter in re-NC machining using cutter offset according to the present invention. 10... NC device, 14... NC program supply means, 16... High speed NC data creation device, 18
...Servo mechanism, 26a...High speed NC data processing unit, 26b...Scaling calculation unit, D...Cutter diameter, r...Cutter radius, k...Scaling magnification.

Claims (1)

[Claims] 1. In the NC machining method of an NC machine tool, the same
Using an NC machining program, the tool diameter D
and the quantity D/ expressed as a function of the scaling factor k
Correcting errors in scaling processing, which is characterized by reprocessing by offsetting 2(k-1).
NC processing method. 2 At the time of re-machining, use a tool with a diameter different from the diameter D of the tool used for the initial NC machining.
According to claim 1, the amount D/2(k-1) obtained from the diameter D of the tool used for NC machining is offset, and the re-machining is performed using the NC machining program. An NC machining method that corrects errors in scaling machining. 3 In the NC machining method of the NC machine tool, the information processing section interpolates position command data based on the NC machining program, creates movement command data for each feed axis of the NC machine tool, and calculates the amount of movement of each feed axis. is independently multiplied by the desired scaling factor for each feed axis, creating independent scale movement command data for each feed axis, and transmitting the movement command data to the servo mechanism of the NC device to perform NC processing. After the same
Using an NC machining program, the position of the machining start point is moved in the scaled direction by an amount expressed as a function of the tool diameter D and the scaling factor k, so that the positions of the tool and the workpiece are moved relative to each other. An NC machining method for correcting errors in scaling machining, characterized by remachining by offsetting D/2(k-1). 4 At the time of re-machining, use a tool with a diameter different from the tool diameter D used for the initial NC machining.
The amount D/2 (k-1) obtained from the diameter D of the tool used for NC machining is offset, and the NC
The NC machining method for correcting errors in scaling machining according to claim 3, wherein the re-machining is performed using a machining program. 5 Set the tool diameter of the tool to be used to be a smaller diameter d than the initial tool diameter D, offset the amount D/2 (k-1) found from the initial tool diameter D, and use the NC machining program. An NC machining method for correcting errors in scaling machining according to claim 3, wherein said remachining is performed.