JPS63272418A - Thread-cutting method - Google Patents

Abstract

PURPOSE:To prevent a cutter from wear, by providing such a thread cutting method that cutting along the center line of a crest of the a thread, cutting along walls of the crest and cutting down to the bottom of the crest along the center line are successively made. CONSTITUTION:When a workpiece is cut so as to form a thread having a thread-height K, first to third cutting steps are made by a constant cutting depth (d). The first cutting step is made so that the cutting edge of a cutter 1 is moved along the center line of a crest of a thread to be cut. Then, a second cutting step is made so that the cutting edge is moved along one wall surface of a crest to be cut, and this step is carried out along both wall surface of the crest, repeatedly, until the total cutting depth along each wall surface becomes more than a set value. Thus, after completion of cutting steps IV to XI, the third step is again carried out so that the cutting edge of the cutter 1 is moved again along the center line of the crest to complete the thread cutting.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a thread cutting method.

In the conventional thread cutting method controlled by a numerical control device, there are four types of cutting methods, as shown in FIGS. 5 to 8. That is, as shown in FIG.
For constant cutting/single-edge cutting, the cutting edge of the cutting tool 1 is moved along one cutting surface of the workpiece 2 so that the cutting amount is constant each time.As shown in Fig. 6, the cutting edge of the cutting tool 1 is Constant cutting amount/zigzag cutting, in which the cutting surface is alternately moved along the cutting surface so that the cutting amount is constant each time;
As shown in FIG. 7, the cutting edge of the blade 1 is moved along one cutting surface of the workpiece, and the depth of cut is constant each time. There are four types of methods: constant depth of cut and staggered cutting, in which the cutting edge is alternately moved along two cutting surfaces and the depth of cut is constant each time.

Problems to be Solved by the Invention During cutting, it is better to keep the cutting load as constant as possible. This point is the same in thread cutting, and from this point of view, constant cutting amount/single edge cutting or constant cutting amount/staggered cutting as shown in Figures 5 and 6, in which the cutting amount is constant and the cutting load is uniform, is used. However, if this method of cutting has a constant cutting amount, as the machining progresses and the depth of cut decreases, the amount of cutting will decrease as shown in Figures 5 and 6. If the blade of the knife 1 is not sharp, it will not be possible to cut the small allowance;
A phenomenon occurs in which the blade of the cutter 1 slides on the cutting surface, causing the blade of the cutter 1 to wear out. Particularly when machining a screw with a large 6-pitch (lead), as the machining progresses, the threads become smaller and this phenomenon often occurs. In addition, with the constant cutting amount and single-edged cutting method shown in Fig. 5, there are many cutting edges on one side of the cutting tool 1, which causes only one blade to wear out and shortens the life of the cutting tool 1. have.

On the other hand, with the cutting method shown in Figures 7 and 8 where the depth of cut ff1 is constant, the amount of cut is constant, so the cutting load increases as the machining progresses, resulting in the machining of threads with a small pitch (lead). However, when machining screws with a large pitch (lead),
The fluctuation in cutting load is large, which is undesirable. Furthermore, single-edge cutting with a constant depth of cut as shown in FIG. 7 has the disadvantage that only the blade 1 is used a lot, which causes wear and shortens the life of the blade 1, as described above.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thread cutting method that uses the blades on both sides of a cutter almost equally, reduces wear on the blade of the cutter, and extends the life of the cutter.

Furthermore, it is an object of the present invention to provide a thread cutting method with less variation in cutting load.

Another object of the present invention is to provide a thread cutting method suitable for thread cutting with large pips (leads).

Means for Solving the Problems The present invention performs a first step of cutting by moving the cutting edge of the blade along the center line of the thread bottom of the thread to be machined, and then cutting the bottom of the thread to be machined. The second stroke of moving the cutting edge along each wall to cut the depth of cut is performed for one or more strokes each until the total depth of cut for each wall in the second stroke reaches the set value or more, and then The above-mentioned problem was solved by performing the third stroke of moving the cutting edge along the center line and cutting the cutting depth one or more times until the cutting edge reached the set screw bottom.

Operation: In the first stroke of cutting, the cutting edge of the blade is moved along the center line of the thread bottom of the thread to be machined to make a cut, and this first stroke is performed for one or more strokes, and then the second stroke is performed. , the cutting edge is moved along the wall of the valley of the thread to be machined, and the cutting is performed on each wall of the valley until the total depth of cut in this second stroke exceeds the set value. Even if both sides of the blade are used and the depth of cut is constant, the variation in cutting load will not be large. In addition, after the second stroke is completed, the third stroke moves the cutting edge along the center line of the thread bottom to cut and cut, and the third stroke cuts to the thread bottom. The blades on both sides of the knife are used in the step 3 as well, and the blades on both sides of the knife are used in the step 1. Second
Since the outer periphery of the thread trough has already been scraped off by the stroke, the amount of cutting becomes large and the cutting load does not become large. Therefore, the method of the present invention is suitable for cutting threads with a large pitch (lead).

Embodiment FIG. 1 is an explanatory diagram of an embodiment of the present invention, showing an example of machining a thread with a thread height k on a workpiece 2,
This embodiment shows an example in which thread cutting is performed with the depth of cut in each of the first to '3rd strokes described above being set to a constant depth of cut d. First, a first step is performed in which the cutting edge of the blade 1 is moved along the center line of the thread bottom of the thread to be machined to make a cut.

In this embodiment, the first stroke consists of three cutting depths, and the cutting edge is moved along the center line of the screw bottom by the set depth of cut ld, as shown in Fig. 1.
, then move the cutting edge along the center line of the thread bottom by the depth of cut fid and perform the cutting shown in Figure 1 ■, then similarly perform the cutting shown in Figure 1 ■, and then make the depth of cut. , a case in which the total depth of cut 14d exceeds the set value is shown, and in this case, the cutting depth in the first stroke is finished and the next second stroke is started. That is, if the total depth of cut exceeds the set value by the next depth of cut, the next depth of cut is not performed and the process proceeds to the second stroke. Note that the first stroke may be performed until the depth of cut exceeds a set value, and then the second stroke may be performed. Also,
The number of cutting depths (number of strokes) to be performed in this first stroke may be set, and when this set value is reached, the process may proceed to the second stroke.

Next, in the second process, the cutting edge is moved along the wall of the valley of the thread to be machined to cut the depth of cut, and this process is performed along both walls of the valley, so that the total depth of cut for each wall is the set value. Repeat this process until the above is achieved.

That is, in FIG. 1, ■, ■, ■, ■, and ■.

■、＠J、Do the cutting of ■. The set value for the total depth of cut in the second stroke is the total depth of cut in the first stroke or the first. When the depth of cut is constant in the second stroke as in the example shown in FIG. In the example shown in FIG. 1, the first stroke is 3 strokes, and the second stroke is 4 strokes for 8 walls, an increase of one.

In this way, when the second stroke is completed, that is, when the cutting and cutting in the second stroke from ■ to ■ in FIG. , performs a third step of cutting. In this third step, if the cutting edge does not reach the bottom of the thread even after cutting by a certain amount d, cutting is performed by cutting by this certain amount d,
If the depth of cut exceeds the thread bottom after making a certain amount of cut d, the cutting is continued until the cutting edge reaches the position of the thread bottom, and the thread cutting process is completed.

- In the embodiment shown in FIG. 1, the cutting depth ld is 0. Perform the cutting of ■, make the cutting depth d′ to the bottom of the thread in [phase], and
Thread cutting has been completed.

As a result of cutting in this way, both sides of the blade of the cutter 1 are used approximately equally, and as a result, the blades on both sides wear approximately equally, compared to the conventional thread cutting method that uses a single edge. The life of the knife 1 will be approximately twice as long. In addition, the workpiece 2 on the center line of the thread bottom is removed by a predetermined amount, then the workpiece 2 is removed from both sides of the thread valley, and finally the workpiece 2 is removed along the centerline of the thread bottom, so the machining progresses. However, the amount of cutting does not change significantly, and the variation in cutting load is reduced.

Further, in this embodiment, since cutting is performed with a constant depth of cut, there is less cutting, and the blade of the cutter and the cutting surface do not slide and wear the blade. Further, if the pitch (lead) of the thread is particularly large and the variation in the cutting load during cutting during the first stroke is large, the cutting may be performed with a constant cutting amount only during the first stroke.

Although the above-mentioned thread cutting process may be performed manually or by other methods, an example will be described below in which the thread cutting process is performed using a fixed cycle using a numerical control device.

Fig. 2 is an explanatory diagram of a canned cycle for thread cutting controlled by a numerical controller, in which the blade 1 is applied to the workpiece 2 from the canned cycle start point B1 by a predetermined depth of cut, until it reaches the cutting position B2. While rotating the workpiece 2, move the cutter 1 relative to the workpiece 2 in the Z-axis direction, move it to the cut-up point B3 between the predetermined depths of cut, then move it in the X-axis direction and then in the Z-axis direction. Then, it is returned to the fixed cycle starting point B1, and then moved to the cutting position B2 according to the next cutting depth, and the same operation is performed sequentially to perform thread cutting. In this thread cutting process, a fixed recycle G code has conventionally been used, and the format of this G code is as follows.

G76X Z I K D F A P
:G76 is a G code indicating a fixed cycle for thread cutting.

X is the diameter value of the thread bottom of the thread to be machined. .

K is the height k of the thread (distance in the X-axis direction).

D is the first cut suspension d0 F is screw glue f0 Δ is the angle a of the cutting edge (the angle of the thread).

P is the designation of the cutting method, for example, Pl for constant cutting amount and single-edge cutting shown in Fig. 5, B2 for constant cutting amount and staggered cutting shown in Fig. 6, and B3 for constant cutting amount and single-edged cutting shown in Fig. 7. ,
The constant depth of cut/zigzag cutting shown in Fig. 8 is designated as B4.

When 076 of the canned cycle for thread cutting as described above is read from the cannibal program, the numerical control device moves the blade 1 from the canned cycle start position B1 to the canned cycle start position B2, as described above. B3. B4. The machine moves sequentially to B1, makes a predetermined depth of cut, and processes the thread until the height of the thread reaches the commanded value k. It should be noted that the parameter for the screw cut-up r is set according to the screw thread f.

The above is a conventional fixed cycle thread cutting method, but by adding the cutting method shown in Fig. 1 as, for example, B5 to the parameter P that specifies the cutting method of this fixed cycle, cutting method P5 is set. If specified, the first
Machining should be performed using the cutting method shown in the figure. In this embodiment, the set value for the total depth of cut in the 19th stroke for transitioning from the first stroke to the second stroke is set as a parameter from the manual data input device of the numerical control device. If this setting value is also set using the G code of the canned cycle for thread cutting, create a new G code that commands the canned cycle for thread cutting using the cutting method shown in Fig. 1, and add this G code to the parameter of G76 above. A parameter for setting the set value U is provided.

Also, the second step when transitioning from the second step to the third step
The set value for the total depth of cut in the stroke may be similarly set as a parameter, but in this embodiment, it is set on the program as described below.

Therefore, first, the position of the cutting edge of the blade 1 during each cutting in the cutting method P5 in the thread cutting method shown in FIG. 1 will be analyzed. The cutting edge angle of the cutter 1 is the lead of the al thread as f, the height of the thread as k, the first depth of cut as d, the intersection of the center line of the thread bottom of the thread to be machined and the outer diameter of the workpiece, That is, if we take point BS in Figure 1 as the origin and calculate the distance between this point and the cutting edge of the blade 1 for each cutting, the distance in the Z-axis direction (left and right in Figure 1) for each cutting in the first stroke is "0", and the X-axis direction (up and down in Figure 1) is d
, 2d, 3d, and the n-th incision becomes nd.

Moreover, the distance in the X-axis and Z-axis directions between the cutting edge and point 88 with respect to the cutting depth when the cutting edge moves along one wall of the thread valley in the second stroke is as follows for each stroke for each die in FIG.
In (1) and (2) to (3), if the first cut for each mold is m = 1, the distance in the X-axis direction from the point 88 at each cut is md, and the distance in the Z-axis direction is (f/ 2)
−mdtan(a/2>).

In addition, in the third stroke, the z-axis direction is rOJ, and the
Assuming that n cuts are made in the first stroke, the distance in the axial direction is (n+1)d for the first cut (0 in Figure 1) of the third stroke, and (n+2) for the second cut. d..., and finally kd.

In this way, the position of the cutting edge of the blade 1 at each cutting time is determined, and based on this, the numerical control device sets the cutting method P to the fixed cycle for thread cutting with G code G76.
The process when the method shown in FIG. 1 of No. 5 is specified will be explained with reference to the flowchart of FIG. 3. Note that the hardware configuration of the numerical control device is the same as the configuration for conventional thread cutting, so a description thereof will be omitted.

G code G of the thread cutting canned cycle from the program
76 is read, and if the designation by the parameter P for specifying the depth of cut is P5, first set the index n to "1" (step S1), and set the program parameter D, the depth of cut d read in 8, and the cutting edge angle a. Therefore, the first cut of the first cut is
The coordinate position (point B2 in FIG. 2) at which the blade 1 starts moving relative to the workpiece 2 in the z-axis direction for cutting is determined from the distance of the cutting edge from the drawing point BS in the x@ and z-axis directions.

Now, if the Z-axis coordinate of the canned cycle start point is ZO, then the first
In the first step (■ in Fig. 1), the cutting depth ff1d is made from the outer peripheral surface of the workpiece 2, so the cutting edge
The axis coordinate position x 1 is the outer circumferential surface calculated by adding the screw thread height k to 1/2 of the diameter value X of the screw bottom specified in the program (as shown in Figure 2, the origin of the coordinate position is The coordinate position X1 = (X/2) + md is obtained by subtracting the cut id from the X-axis coordinate position of the center of the mounting part. and,
As the Z-axis coordinate position Z1, the coordinate position of the cutting edge at the first cutting of the first stroke is determined as the Z-axis coordinate position ZO of the starting point during the fixed cycle (step 82). The cutting edge is moved to the thus determined coordinate position (Xl, Zl) and cutting is performed (step 82).

That is, as shown in the subroutine of FIG. 4, the coordinate position @(Xl
. Perform thread cutting while rotating (Step 5B)
2). Then, when the position determined by the value 2 specified by the program parameter Z and the thread cut-up r set by the parameter from the manual data input device is reached, the cut-up process is performed (step 5B3), and then 1, the start point for the fixed cycle. Processing to return to B1 is performed (step 5B4). Note that step SB2. Since the processing of SB3 and SB4 is the same as the conventional process, the details will be omitted. In this way, when the first thread cutting is completed, the process returns to the main routine shown in Fig. 3, and the index n is incremented by "1" in step 8.
4) It is determined whether the distance from the point 88 of the cutting edge by the next cutting exceeds the value U set by the parameter. In other words, it is determined whether nd=26>U (step S5).
, if it is not exceeded, repeat the process from step 82 onwards,
Perform the second cutting and cutting (cutting depth indicated by ■ in Fig. 1). At this time, when the rotational position of the workpiece 2 reaches the position where the blade 1 starts moving in the Z-axis direction relative to the workpiece 2 in one cutting, that is, when the Z-axis direction movement start position is reached. , the blade 1 is moved in the direction of the workpiece 2 (step 5B2), and the second cutting is started. As a result, the workpiece 2 is rotating at a predetermined constant speed, and the cutter 1
moves in the z-axis direction at a predetermined constant speed, so if the cutting edge coordinate positions for the first and second cuts are the same,
In the second cut, the cutter 1 starts cutting from the same position on the workpiece 2. However, the Z-axis coordinate position at the time of the second cut is the same, but the X-axis coordinate position is
Because the second cut has made it smaller by d,
As shown in FIG. 1, the cutting edge advances by d in the X-axis direction to perform cutting.

Note that if the judgment in step S5 is that the cutting method is such that the depth of cut is constant as shown in FIG. The nth time is nd), so instead of the set value U, the number of cutting depths in this first stroke, for example, as in the example shown in Fig. 1, after three cutting depths, the line line of cylinder 2 is changed. In this case, the process may proceed to the second step, that is, to step S6 when n=4.

In addition, the process of step $5 is changed to step S3 and step S.
4, the total depth of cut 1nd (the X-axis coordinate distance of the cutting edge from point BS) has exceeded the set value U, or the set number of depths of cut has been completed. Alternatively, it may be determined whether or not it has been completed.

Thus, when the first step of cutting is completed, the process moves to step S6, where the index m is set to "1" and the cutting edge is moved along one wall of the valley of the thread to be machined. Perform step 2 cutting. In this example, the first
As shown in the figure, cutting is performed from the right side wall in Figure 1, and the position of the cutting edge at this time is determined. Since the first cut in the second stroke is the set depth of cut d, the X-axis coordinate position
=X1 is, Xm=X1= (x/2)+ to -md= (x/2
) + becomes -d. In addition, the Z-axis coordinate position is Zm=21 = ZO+((f/2 )-djan (a/2)). Then, the cutting edge is moved to this coordinate position (Xl, Zl), and the depth of cut cutting process (step 89) shown in the subroutine in Figure 4 is performed.
The Z-axis coordinate Zm = 21 is calculated from the Z-axis coordinate ZO at each depth of cut in the first stroke ((f/2>-dtan(a/2)
) is positioned farther than the workpiece 2 (in the Z-axis positive direction), so when cutting by moving the cutter 1 relative to the workpiece 2 in the Z-axis direction, compare it with the first cutting of the first stroke. The cutter 1 comes into contact with the workpiece 2 at a later stage, and the workpiece 2 is cut as shown in FIG.

In this way, when the first cutting (■ in Figure 1) is completed on one wall of the thread valley to be machined, the index m is set to "1".
'' step 510), and it is determined whether the value of this index m is equal to the value of the index n in the first step plus "1" (step 511). That is, in the first step, cutting is performed three times in the example shown in FIG.
Since the process moves to step S6 because τ exceeds the set value in the third cutting, n=4, and the value of the index m is n.
It is determined whether or not +1=5, and the processing from step 87 onward is performed until the value of the index m becomes 15''. That is, in step S10, the index m=2, and in steps S7 and 88, >-mdtan(a/2))-ZO
+((f/2>-26jan(a/2)) The above formula is calculated to determine the position of the cutting edge, and the same cutting process as described above (■ in Fig. 1) is performed. m=n+1=
Repeat until 4+1=5, and when the index m reaches (m+1), for example, in the example in Figure 1, repeat the process 4 times (■, ■, ■, in Figure 1).
When the cutting of (ii) is completed and the index m = 5, the depth cutting for one wall of the thread valley (on the right side in Figure 1) is completed,
Move on to cutting the other wall. That is, step S1
In step 2, the index m is set to "1", and steps 813 to 817, which are equivalent to steps 7 to 811, are performed, but steps 87 to 811 and step 8 are performed.
The only difference between the processes in steps 13 to 817 is that in step S8 and step 814. That is, steps 87 to 811
Compared to the case of cutting the right wall of the thread valley in Figure 1, the X-axis coordinate position of the cutting edge at each depth of cut is
(x/2)+ -mdT- same Tearcar, Z-axis coordinate position is different. In other words, in Figure 1, cutting the left wall involves cutting the left side of the center line of the thread bottom of the screw.
In the process, the cutting edge must contact the workpiece 2 at an earlier timing, so the distance between the point BS and the cutting edge position is ((f/2) - mdtan(a/2)
) in the direction of workpiece 2. As a result, the cutting position each time when cutting this left wall is
m-(x/2>+, -md Zm=ZO-((f/2)-mdtan(a/2)).Thus, the index m becomes "1" in the index n during the processing of the first process. ” Perform cutting until the added value is reached (
■, ■, ■, ■ in Figure 1). And index m=n+1
After (in the example of FIG. 1, m=4+1=5 and four cuttings have been performed), the process moves to the third step starting at the next step 818.

In this embodiment, the number of strokes for each type in the second stroke is one more than the number of first strokes, but this number may be the same (i.e. m=n in step S11.817).
), as shown in Figure 1, when the second stroke is completed, there will be more scraping holes along both walls of the valley, which will reduce the fluctuation in cutting load caused by the next third stroke. It turns out.

In the third stroke, the value of the index n in the first stroke is multiplied by the depth of cut ad in step 818 to calculate the total depth of cut (of the cutting edge) by the first stroke at the stage where the cutting of the first stroke is completed. The value obtained by adding the depth of cut d to the distance in the X-axis direction of the cutting edge during cutting at the end of the first stroke from point BS (■ in Figure 1)
In the example shown in the figure, the depth of cut has been performed only three times, but the index n (n = 4 in step S4) is judged to be greater than the thread height k, and if it is not , similar to the first stroke, the coordinate position of the cutting edge Xn= (x/2)
-nd Zn=ZO is determined (step 519), cutting is performed (step 520), the index n is incremented by "1" (step 521), and the processes from step 818 are repeated. That is, in the example of FIG. 1, since n=4 at the end of the first process,
In Fig. 1, the cutting coordinate position for cutting 0 is X4 - (x/2) + -46 Z4 = ZO, and the cutting coordinate position for cutting ◯ is X5 = (x/2) + -56 Z5 = ZO. Become. Thus, when attempting to cut the next depth of cut, the distance nd from the point BS in the X-axis direction of the cutting edge (the total depth of cut in the first stroke plus the total depth of cut up to the next depth of cut in the third stroke) value) exceeds the thread height k set in the program (step 818), the X-axis coordinate position of the cutting edge at the next depth of cut is set as the thread bottom (x/2), and the Z-axis direction is set as ZO. (Step 822), performs cutting (
Step 523). In this way, the thread cutting process of this embodiment is completed.

Effects of the Invention As described above, in the present invention, both sides of the blade are used equally for cutting, so the blades on both sides wear out evenly, and unlike conventional methods, only one side wears out more. This can extend the life of the cutlery. In addition, the center of the thread trough is first removed, then both sides of the trough are removed, and finally the cutting edge is moved along the center line of the thread bottom to remove the depth of cut, so the depth of cut remains constant. However, the present invention is most suitable for machining threads with a large pitch (lead), since there is little change in cutting amount and less variation in cutting load.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram illustrating a thread cutting method according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a fixed cycle for thread cutting, and FIGS. 3 (A) and (B) are illustrations of the embodiment of the present invention. Fig. 4 is a flowchart of the subroutine for cutting depth and cutting processing in the same operation flowchart, and Fig. 5 is a conventional cutting method for constant cutting amount and single-edge cutting. Figure 6 is a diagram showing the conventional cutting depth method for constant cutting amount and staggered cutting, Figure 7 is a diagram showing the conventional cutting depth method for single edge cutting with constant cutting depth m, and Figure 8 is a diagram showing the conventional cutting depth method for single-edge cutting. Constant
It is a figure which shows the cutting method of staggered cutting. 1...Knife, 2...Work.

Claims (8)

[Claims] (1) Perform one or more first strokes of cutting by moving the cutting edge of the knife along the center line of the thread bottom of the thread to be machined, and then move the cutting edge along each wall of the valley of the thread to be machined. The second stroke of moving the blade and cutting the depth of cut is carried out for one or more strokes each until the total depth of cut for each wall in the second stroke reaches the set value or more, and then the cutting edge is moved along the center line of the thread bottom. A thread cutting method characterized in that the third step of moving and cutting is performed one or more steps until the cutting edge reaches a set thread bottom. (2) The thread cutting method according to claim 1, wherein the depth of cut in the first to third strokes is constant. (3) The thread cutting method according to claim 1, wherein the cutting depth in the first stroke is a constant cutting amount. (4) The thread cutting method according to claim 3, wherein the depth of cut in the second stroke and the third stroke are constant. (5) The first stroke is performed for one or more strokes until the total depth of cut in the first stroke exceeds the value set by the next depth of cut. Claims 1, 2, and 3 The thread cutting method described in item 1 or 4. (6) The first stroke is performed for one or more strokes until the total depth of cut by the first stroke becomes equal to or greater than a set value. Thread cutting method described in section. (7) The set value of the total depth of cut in the second stroke is as follows:
The thread cutting method according to claim 1, wherein the total depth of cut in the first step is taken as the total depth of cut. (8) The thread cutting method according to claim 2, wherein the total cutting depth of each of the first and second strokes is set by the number of times each stroke is performed.