JPH022662B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a machining method for a machine tool, and in particular, the first machining is performed by moving a tool relative to the workpiece, and then the tool is moved to the workpiece. A rotary shaft that pick-feeds the workpiece relatively to the workpiece, and after pick-feeding, moves the tool relatively to the workpiece in the opposite direction to the processing direction to perform second processing, and repeats these processing operations and pick-feeding operations to perform the desired processing. The present invention relates to a machining method for a machine tool that can prevent a tool from coming into contact with a workpiece during pick-feeding.

<Prior art> In numerically controlled machining of curved surfaces, as shown in Fig. 1, the tool TL is moved in the direction of the arrow at cutting speed along a predetermined path PT1 on the workpiece WK.
After machining the passage, pick feed the tool from the end point Pe to the start point Ps of the next machining passage PT2, and then move the tool along the machining passage PT2 in the direction of the arrow with cutting feed. 2 processing, and then the above pick feed and the 1st and 2nd
The curved surface is machined by repeating the process (reciprocating cutting process).

By the way, in the numerical control machining of such curved surfaces, the central axis of the tool TL (the one-dot chain line in Fig. 1) is controlled so that it always has an inclination angle from the normal direction to the normal direction of the workpiece WK or the cutting direction. It is necessary to perform processing. For this reason, the machine tool is designed to move the tool in, for example, three-dimensional orthogonal axes and simultaneously rotate the tool, thereby making it possible to perform machining while always aligning the tool center axis direction with the normal direction of the workpiece. The NC data that specifies the path includes position data (position vector) that specifies the tool tip position and tool center axis direction data (B-axis, C-axis direction position or tool center axis vector) that specifies the tool center axis direction. I'm here.

Now, even if the movement path of the tool TL of a machine tool including the rotating axis is a straight line LN in the three dimensions of X, Y, and Z as shown in Fig. 2, the tool moves along the B-axis and C-axis at the same time as the linear movement. When the tool is rotated in this direction, the path at the tip of the tool will not be a straight line but will appear as a dotted line. Therefore, if the pick feed path from the first machining end point Pe to the second machining start point Ps is not properly arranged, the tool tip will contact the workpiece at high speed during the pick feed, resulting in incorrect cutting or the tool Breakage will occur.

For this reason, in the past, a pick feed path was defined so that the tip of the tool would not hit the workpiece during pick feed, and the pick feed path was programmed one by one as NC data.

<Disadvantages of the Prior Art> However, this conventional method has the disadvantage that it is troublesome to create NC data for the pick feed passage.

<Object of the Invention> An object of the present invention is to provide a machining method for a machine tool that can easily determine a pick feed path in which a tool does not hit a workpiece without processing the curved surface itself during pick feed.

Another object of the present invention is to generate NC data for machining a curved surface by repeating the first machining along the first machining path, the pick feed, and the second machining in the opposite direction to the first machining direction. It is an object of the present invention to provide a machining method for a machine tool that can be easily created from data specifying the NC data and that can machine a curved surface using the NC data.

Another object of the invention is to comply with the Pickfeed Directive.
A machine that can be inserted into an NC program and automatically find a pick feed path where the tool does not hit the workpiece and has a short stroke length, and move the tool along the found pick feed path. The purpose is to provide a mechanical processing method.

<Summary of the invention> FIG. 3 is a schematic explanatory diagram of the present invention. The present invention allows the tool TL to be used for workpieces with a concave pick-feed portion.
Move the tool relative to WK to perform the first machining along the path PT1, then pick feed the tool relatively to the workpiece from the end point Pe of the first machining path to the start point Ps of the second machining path, After the pick feed, the second machining path PT2 is in the opposite direction to the aforementioned machining direction.
This is a machining method for a machine tool having a rotating shaft, in which a second machining is performed by moving the tool relative to the workpiece along the axis, and these machining operations and pick feed operations are repeated to perform the desired machining. In the present invention, by using the three-dimensional position data of the machining start point Ps of the second machining and the tool center axis direction data at the machining start point,
Find the approach plane AP that is in contact with the machining end point Pe of the first machining, and use the three-dimensional position data of the machining end point Pe of the first machining and the tool center axis direction data at the machining end point to find the straight line passing through the machining end point and the center of the tool. Find the intersection point Pc of the axial straight line SL and the approach plane AP, release the tool toward the intersection point, then move the tool from the intersection point to the second machining start point to pick feed, and then start the second machining. Execute.

<Embodiment> FIG. 4 is a block diagram of an embodiment of the present invention.
NC tape or memory (hereinafter referred to as NC tape) 1
01 stores NC data. Furthermore, NC
The data shows the tool TL in the first machining path PT1 in Figure 3.
Cutting is performed in the direction of the arrow to the end point Pe, and then from the end point Pe to the machining start point Ps of the second machining path PT2
The pick feed is performed until then, and then cutting is performed in the direction of the arrow along the second machining path, and thereafter the above-mentioned reciprocating cutting operation is repeated. In addition, each passage PT1, PT2 is approximated by a polygonal line using a minute straight line,
Furthermore, the pick feed is instructed by the M function command (M□□). The NC data reading device 102 reads NC data from the NC tape 101 block by block and stores it in the input memory 103. The numerical control unit 104 is stored in the input memory 103.
The NC data is decoded, and if the NC data is path data, it is input to the pulse distributor 105, and if the NC data is an M function command, S function command, or T function command to be output to the machine side, these are used. is input to the machine tool 107 via the high-voltage circuit 106,
Furthermore, if the NC data is a pick feed command M□□, the NC data reading device 102 reads the next NC.
Read the data (starting point data of the next machining path).

If the NC data is path data, the numerical control unit 104 calculates incremental values Xi, Yi, Zi, Bi, and Ci in each axis (orthogonal coordinate axes X, Y, Z, vertical and horizontal rotation axes B, C). . Next, the numerical control unit 104 sets the command linear velocity F in the three-dimensional direction and the incremental values Xi, Yi, Zi,
Using Bi, Ci, the velocity components Fx, Fy in each axis direction,
Fz, Fb, and Fc are expressed as follows: Fx=Xi・F/√ ² + ² + ² ... (1a) Fy=Yi・F/√ ² + ² + ² ... (1b) Fz=Zi・F/√ ² + ² + ² ... (1c) Fb = Bi・F/√ ² + ² + ² ... (1d) Fc=Ci・F/√ ² + ² + ² ... (1e) Obtain from and then predetermine time ΔT
The amount of movement ΔX, ΔY, ΔZ, ΔB, ΔC that should be moved in each axis direction during (16 msec) is calculated using the following formula: ΔX=Fx・ΔT ……(2a) ΔY=Fy・ΔT ……(2b) ΔZ=Fz・ΔT...(2c) ΔB=Fb・ΔT...(2d) ΔC=Fc・ΔT...(2e) Calculate these ΔX, ΔY, ΔZ, ΔB, and ΔC to the pulse distributor 105 at every time ΔT. Output. The pulse distributor 105 performs simultaneous 5-axis pulse distribution calculation based on the input data and distributes the distribution pulses Xp, Yp,
Zp, Bp, and Cp are generated and output to a servo circuit (not shown) for each axis, and the tool is moved along the cutting path.

The numerical control unit 104 also changes the current positions Xa, Ya, Za, Ba, and Ca of the current position memory 108 every ΔT seconds using the following formula: Xa±ΔX→Xa...(3a) Ya±ΔY→Ya...(3b) Za±ΔZ→Za...(3c) Ba±ΔB→Ba...(3d) Ca±ΔC→Ca...(3e) Updated (sign depends on moving direction), and similarly every ΔT seconds. The remaining movement amounts Xr, Yr, Zr, Br, Cr (initial values are Xi, Yi, Zi, Bi, Ci, respectively) stored in the movement amount memory 109 are calculated by the following formula: Xr−ΔX→Xr (4a) Yr−ΔY→Yr……(4b) Zr−ΔZ→Zr……(4c) Br−ΔB→Br……(4d) Cr−ΔC→Cr……(4e) Update. Then, the numerical control unit 104 performs pulse distribution processing or Perform other processing.

On the other hand, when the pick feed command M□□ is read from the NC tape 101, the numerical control section 104 immediately causes the next block of NC data to be read and stored in the input memory 103. The NC data commanded after the pick feed command is the position data Xn of the machining start point Ps of the second machining path PT2,
Yn, Zn, Bn, and Cn, which are stored in the input memory 103.

Thereafter, the tool center axis vector calculation section 110 calculates the tool center axis vector Va→(ia, ja, ka) at the current position (the machining end point Pe of the first machining path PT1) according to the calculation start signal from the numerical control section 104. The tool center axis vector Vn→(in, jn, kn) at the processing start point Ps of the second processing path PT2 is determined and stored in the tool center axis vector memory 111. If the vertical rotational position of the tool is b and the horizontal rotational position is c, the tool center axis vector can be calculated as follows: i=sinb・cosc (6a) j=sinb・sinc (6b) k=cosb (6c) . Therefore, the tool center axis vector calculation unit 110 calculates the vertical rotational direction positions (Ba, Bn) of the machining end point Pe and machining start point Ps stored in the current position memory 108 and input memory 103,
Using the horizontal rotation direction position (Ca, Cn), (6a) ~
The tool center axis vectors Va→, Vn→ can be determined from equation (6c).

Next, the approach plane calculation unit 112 calculates the machining start point Ps 3 stored in the input memory 103.
Using the dimensional position data (Xn, Yn, Zn) and the tool center axis vector Vn→(in, jn, kn) at the position stored in the tool center axis vector memory 111, the workpiece WK is moved at the machining start point Ps. Find the plane equation of the approach plane AP (Fig. 3) that is tangent to . Now, the general formula for the plane is ax + by + cz = d, and the normal vector Vn → of the plane is (in, jn, kn)
Therefore, in・x+jn・y+kn・z=d...(7a) holds true. Therefore, by determining d in the above equation, a plane equation can be obtained. Now, since the approach plane AP includes the machining start point Ps (Xn, Yn, Zn), in・Xn+jn・Yn+kn・Zn...(7b) holds, so the approach plane AP is (7a),
(7b) is specified by equation.

After that, the intersection calculation unit 113 calculates the approach plane.
Calculate the three-dimensional position coordinates of the intersection point Pc of AP and straight line SL. Now, if the distance from the machining end point Pe to the intersection Pc is l, then Pc→=Pe→+l·Va→ (8a) holds true. However, Pc→, Pe→ are position vectors at the intersection point Pc and the machining end point Pe. Since the intersection point Pc exists on the approach plane AP, Vn→・Pc→=d (8b) holds true. However, d is a value obtained from equation (7b). From equations (8a) and (8b), Vn→・(Pe→+l・Va→)=d...(8c) is established, and l is obtained from equation (8c), and this l is expressed as (8a).
By substituting into the equation, the position vector Pc of the intersection Pc→(Xc,
Yc, Zc) is calculated. In addition, l is l = (d-Vn→・Pe→)/Vn→・Va→ = d−(in・Xa+jn・Ya+kn・Za/in・ia+jn・ja+
kn・ka, and Xc=Xa+l・ia Yc=Ya+l・ja}...(8d) Zc=Za+l・ka.

When the three-dimensional coordinate values (Xc, Yc, Zc) of the intersection point Pc are input, the numerical control unit 104 sets the tool center axis vector Va in the direction from the machining start point Pe to the intersection point Pc.
It is determined whether the direction matches the direction of , and if it matches, the workpiece shape of the pick feed section is convex, so the following processing is performed. If they do not match, it means that the shape of the workpiece in the pick feed section is concave, and therefore processing will be performed in the case of a concave shape, but such processing will not be explained. Now, if the workpiece shape of the pick feed section is convex, the numerical control section 104 calculates the following equations: Calculate the axis incremental values Xi, Yi, Zi, then perform the calculations (1a) to (1c) and (2a) to (2c) in the same way as above to find ΔX, ΔY, and ΔZ, and calculate ΔT. It is input to the pulse distributor 105 every second. or,
The numerical control unit 104 controls (3a) to (3c) every ΔT seconds,
Perform operations (4a) to (4c). Then, if Xr=Yr=Zr=0, that is, if the tool reaches the intersection Pc, then the numerical control unit 104 calculates Bn−Ba→Bi Cn−Ca→Ci to determine the vertical rotation direction. Calculate incremental values Bi and Ci in the horizontal rotation direction. After that,
The calculations (1d) to (1e) and (2d) to (2e) are performed to obtain ΔB and ΔC, which are input to the pulse distributor 105 every ΔT seconds. In addition, the numerical control unit 104
Calculations (3d) to (3e) and (4d) to (4e) are performed every second. Then, when Br=Cr=0, the numerical control unit 104 next calculates The incremental values Xi, Yi, and Zi of each axis are calculated, and ΔX, ΔY, and ΔZ are similarly determined, and these are input to the pulse distributor 105 every ΔT seconds. Then, when Xr=Yr=Zr=0, the NC data reading device 102 is made to read the NC data of the next block, and thereafter the tool is moved along the second machining path based on the NC data. Process the second passage.

Then, by repeating the above operations, a curved surface will finally be processed.

The above example assumes that vertical rotational direction position B and horizontal rotational direction position C are input from the NC tape as data for specifying the tool center axis direction, but B,
Instead of C, tool center axis vector V → (i, j, k)
may be given. However, in such cases (1a)
~ Prior to calculating equation (1e), vertical and horizontal rotational directions positions B and C are calculated from the tool center axis vector using the following equation.
It is necessary to ask for

B=tan ^-1 (√ ² + ² /k) C=tan ^-1 (j/k) Note that the tool center axis vector calculation section 110 is no longer necessary (the calculations of equations (6a) to (6c) are no longer necessary). Become).

Also, in the above, a pick feed command is inserted into the NC program, and when the pick feed command is read from the NC tape after machining along the first machining path is completed, the pick feed path is automatically determined and the pick feed command is This is a case where the tool is moved along the path and then machining is performed along the second machining path. However, the present invention is not limited to such a case. For example, input data that specifies a curved surface and data that specifies a pick feed, use the curved surface data to create NC data that specifies a cutting path, and use the data that specifies a pick feed to create NC data for the pick feed path using the method described above. Create data to obtain NC tape, and then print the NC tape.
It can also be configured to process curved surfaces by inputting it to an NC device. Furthermore, NC data for a cutting path for moving the tool along the first machining path in advance,
A series of NCs consisting of NC data for the cutting path that moves the tool along the second machining path, and pick feed commands inserted between these two NC data.
Prepare data, input it to the NC tape creation device, use the pick feed command to find the pick feed path using the method described above, create NC data that specifies the pick feed path, replace the pick feed command with the NC data, and then It is also possible to re-create an NC tape containing pick feed path data instead of the pick feed command, and input the NC tape to the NC device to process the curved surface. FIG. 5 is a block diagram of an embodiment of the present invention, in which the same parts as in FIG. 4 are given the same reference numerals. NC tape or memory 10
1. Identifying tool movement along the first machining path
A large amount of NC data is stored, which includes NC data, NC data specifying tool movement along the second machining path, and pick feed commands inserted between these data. Note that the data for specifying the passage does not necessarily have to be NC data, but may be position data for specifying the end point of each minute straight line when a curve is approximated by a polygonal line using minute straight lines, and data for specifying the direction of the tool center axis. .

The NC data reading device 102 reads one block at a time.
NC data is read from the NC tape 101 and stored in the input memory 103. In addition, input memory 10
3 is designed to be able to store two blocks worth of path data. The NC tape creation processing unit 201 determines whether the NC data of the current block stored in the input memory 103 is a pick feed command, and if it is not a pick feed command, the NC data is directly transferred to an NC data output device (paper tape puncher, magnetic (tape device, etc.) 202, and then causes the NC data reading device 102 to read the next NC data.

On the other hand, if the NC data stored in the input memory 103 is a pick feed command, the NC tape creation processing section 201 uses the NC data reading device 102 to read the NC data of the next block, in other words, the machining start point Ps of the second machining path. 3D position data Xn, Yn,
Zn and vertical rotational direction and horizontal rotational direction position data Bn, Cn are read and stored in the input memory 103. The input memory 103 contains three-dimensional position data Xa, Ya, and the machining end point Pe of the first machining path.
Za, vertical and horizontal rotational direction positions Ba and Ca are also stored.

After that, the tool center axis vector calculation unit 110
The current position (first processing path PT
Find the tool center axis vector Va → (ia, ja, ka) at the machining end point Pe) of No. 1, and also calculate the vertical rotational position Bn and horizontal rotational position of the machining start point Ps stored in the input memory 103. Using Cn, the tool center axis vector Vn→(in, jn, kn) at the machining start point is determined from equations (6a) to (6c), and these are stored in the tool center axis vector memory 111.

Next, the approach plane calculation unit 112 and the intersection calculation unit 113 perform the above-mentioned calculations to obtain the three-dimensional coordinate values (Xc, Yc, Zc) of the intersection point Pc, and input these to the NC tape creation processing unit 201.

When the three-dimensional coordinate values of the intersection point Pc are input, the NC tape creation processing unit 201 moves from the machining end point Pe to the intersection point Pc.
It is determined whether the direction toward the direction matches the direction of the tool center axis vector Va→, and if it matches, the direction from Pe
Positioning data up to Pe G01XXc, YYc, ZZc; is created and output to the NC data output device 202. If they do not match, the shape of the workpiece in the pick feed section is concave, and NC data for the concave case is created, but this will not be explained. Next, the NC tape creation processing unit 201 creates rotational direction positioning data G01BBn, CCn; for rotating the tool in the vertical and horizontal directions at the intersection point Pc and aligning the tool center axis vector with that at the machining start point Ps. Output to the NC data output device 202.

After that, the NC tape creation processing unit 201 creates positioning data G01XXn, YYn, ZZn; for linearly moving the tool from the intersection point Pc to the machining start point Ps, and outputs it to the NC data output device 202.
At the same time, the next NC data is read by the NC data reader 10.
2, read the data, and repeat the above process based on the read NC data. Through the above steps, the NC tape 203 for processing a curved surface has been created. It is assumed that the NC data is created as an absolute.

NC tape 203 created by the above processing
The NC data stored in is read by the NC device 204, and the NC device 204 executes NC processing based on the read NC data. That is, the first
After performing cutting along the second machining path, pick feed is performed, and after pick feeding, cutting is performed along the second machining path, and thereafter the above operations are repeated to process the curved surface.

Incidentally, the circuits shown in FIGS. 4 and 5 can also be configured using a microcomputer. In that case, the flowchart of the processing of the processor is
The result will be as shown in Fig. 7. Further, the present invention can be applied when the inner product of the tool center axis vector at the end point of the first machining path and the start point of the second machining path is positive and the workpiece shape of the pick feed portion is convex.

<Effects of the Invention> As explained above, according to the present invention, in a machining method for a machine tool including a rotary axis that processes a curved surface by repeating reciprocating cutting operations between a pick feed and a tool, the machining start point Ps after the pick feed is Find the approach plane AP that is in contact with the workpiece at
The intersection point Pc between the approach plane and the straight line SL in the direction of the tool center axis at the machining end point Pe is found, and then the pick feed operation is performed along the path of Pe → Pc → Ps, so the pick feed path can be easily found. Moreover, it is possible to reliably prevent the tool from hitting the workpiece during pick-feeding, and there is no need to process the curved surface shape itself. In addition, it is possible to easily create NC data for picking feed the tool along the Pe → Pc → Ps path by performing the process for determining the pick feed path described above, and in this case, the NC data for the pick feed path where the tool does not hit the workpiece can be easily created. Can create data.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the tool path when machining a curved surface by repeating pick feed and reciprocating cutting operations, Fig. 2 is an explanatory diagram of the trajectory of the tool tip when a rotating axis is included, and Fig. 3 is the curved surface shape of the pick feed section. 4 is a block diagram of an embodiment of the present invention, FIG. 5 is a block diagram of another embodiment of the present invention, and FIGS. 6 and 7 are diagrams of FIGS. It is a flowchart of processing when the circuit shown in the figure is configured by a microcomputer. 101... NC tape, 102... NC data reading device, 103... Input memory, 104... Numerical controller, 105... Pulse distributor, 106...
Strong electric circuit, 107...Machine tool, 108...Current position memory, 109...Remaining travel amount memory, 110
... Tool center axis vector calculation section, 111 ... Tool center axis vector memory, 112 ... Approach plane calculation section, 113 ... Intersection point calculation section, 201 ...
NC tape creation processing unit, 202...NC data output device, 203...NC tape, 204...NC
Device.

Claims (1)

[Claims] 1. A method for moving a tool relative to a workpiece to
After that, the tool is pick-fed relative to the workpiece, and after the pick-feeding, the tool is moved relative to the workpiece in the opposite direction to the machining direction to perform a second machining, and these machining operations and pick-feeding operations are repeated. In a machining method for a machine tool including a rotating shaft that performs a desired machining on a convex portion of a workpiece, three-dimensional position data at a machining start point of the second machining and tool center axis direction data at the machining start point are provided. Using the method, an approach plane that contacts the convex part of the workpiece at the second machining start point is obtained, and the three-dimensional position data of the machining end point of the first machining and the tool center axis direction data at the machining end point are used. find the intersection of a straight line passing through the machining end point in the direction of the tool center axis and the approach plane, and moving the tool toward the intersection;
A machining method for a machine tool, characterized in that the tool is then moved from the intersection to a second machining start point to pick feed, and then the second machining is executed. 2 NC data is created from the passage data for the first and second machining and the obtained pick feed passage data, and the convex portion of the workpiece is machined in accordance with the NC data. A method for machining a machine tool according to claim 1.