JPH0549411B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a gear shaping method.

As shown in Fig. 1, a gear shaper generally cuts the gear 2 to be cut while the cutter 1 moves from the top dead center A to the bottom dead center B of its stroke, and then when it returns to the top dead center A. To prevent interference (contact) between the cutter 1 and the part already machined with the cutter, at the bottom dead center B of the stroke, move the cutter 1 a little away from the workpiece gear 2 (relieving) and then return it to the top dead center A. It's starting to look like this. C is a relieving part.

However, in reality, under certain conditions, so-called relieving interference may occur in which the cutter 1 and the gear to be cut 2 interfere with each other during relieving. This has a great effect on the cutter life and machining accuracy. Factors that cause relieving interference include circumferential feed speed,
These include the radial feed rate, the amount of relieving, the shape of the cutter, and the shape of the gear to be cut, but it is generally difficult to change the amount of relieving, the shape of the cutter, and the shape of the gear to be cut in order to prevent interference. Therefore, cutting conditions such as circumferential feed rate and radial feed rate were selected as appropriate. In general, the area of relieving interference with cutting conditions is shown in Figure 2, and as the circumferential feed F _ROT is increased, the safe area of the radial feed F _RAD tends to become narrower.

Here, relieving interference will be further explained. As mentioned above, in gear shaping, the cutter 1 is usually relieved in the radial direction in order to release the cutting edge of the cutter 1 from the gear to be cut 2 during the return process of the cutter. In this case, the problem is not when relieving the cutter 1 in the radial direction, but in the process of returning the cutter 1 from the bottom to the top after relieving. That's it. Therefore, relieving is performed after the cutter 1 has completely passed the lower end of the gear to be cut 2.
Rather than the radial retraction velocity during relieving,
If the relieving amount, which is the distance itself, is small, there will be interference in the return process from the bottom to the top.

In other words, in recent gear shaping, there is a tendency to increase the circumferential feed rate (mm/stroke) to improve machining efficiency, so in the return process, the cutter 1 and the workpiece gear 2
The positional relationship in the circumferential direction will be considerably shifted,
Naturally, a large amount of relieving is required, and in machines with a small amount of relieving, relieving interference occurs.

This will be explained in detail with reference to FIG.
First of all, it should be noted that the cutter 1 of the gear shaper has the shape of a gear, but the workpiece gear 2 becomes a gear only after machining is completed; 1 and the gear to be cut 2 are not meshed with each other. During machining, the cutter 1 moves up and down as shown in Figure 1 to machine the gear to be cut 2. During this up and down movement, the cutter 1 and the gear to be cut 2 simultaneously rotate at a constant speed. . Therefore, naturally, there is a deviation in the circumferential direction between the position where the cutter 1 processes the upper surface of the gear 2 to be cut and the position when the cutter 1 returns after making one reciprocation in the vertical direction. Therefore,
If the position when the cutter 1 makes one reciprocation and returns is located in an unmachined portion of the gear to be cut 2, interference between the cutter 1 and the gear to be cut 2 will occur there. From this, when the circumferential feed speed is very small, the amount of deviation is small, so relieving interference is unlikely to occur.
As the circumferential feed rate increases, the amount of deviation increases, and relieving interference is more likely to occur.

Furthermore, since the radial feed rate (mm/stroke) of the cutter 1 tends to be increased to improve machining efficiency, the depth of cut per stroke of the cutter 1 and the workpiece gear 2 increases accordingly. It is necessary to increase the relieving amount, and in machines with a small relieving amount, relieving interference will occur.

Figure 2 above shows the relieving interference area obtained in the experiment, and the conditions were: relieving amount 0.56 mm, relieving angle 90°, and number of strokes 600/stroke.
The depth of cut is 5.66mm. It can also be seen from FIG. 2 that the larger the circumferential feed rate and the radial feed rate are, the more relieving interference occurs.

For these reasons, the circumferential feed rate and the radial feed rate are factors that cause relieving interference.

However, if the amount of binging is simply set too large in order to avoid relieving interference, there is a disadvantage that the moving distance of the cutter 1 becomes longer and the cycle time of gear shaping becomes unnecessarily long.

Therefore, according to the relieving amount and offset angle (the angle in the relieving direction with respect to the line connecting the cutter center and the workpiece gear center) of the machine used, the circumferential feed rate and radial feed rate should be adjusted as described above. Appropriate selection was made to avoid interference with relieving.

However, in the past, there was no gear shaping machine in which the circumferential feed and radial feed were constant except for switching between rough machining and finishing machining, and the speeds of these were variable. In other words, the radial feed rate was kept constant at a low speed in view of safety to prevent interference and maximum cutting load. Therefore, relieving interference has become a major problem when reducing cycle time in gear shaping.

In view of the problems of the prior art described above, the present invention provides a highly efficient gear shaping method that prevents relieving interference, extends cutter life, improves machining accuracy, and shortens cycle time. The purpose is to

The gear shaping method of the present invention that achieves this objective is as follows:
The circumferential feed rate F _ROT and the radial feed rate F _RAD in gear shaping are calculated using the following formula F _RAD × (F _ROT ) ⁿ = Q...Equation (1) However, Q is a constant value and the relationship 0<n≦1 is used. It is characterized by being maintained and variably controlled. For example, the radial feed rate F _RAD is controlled to be high at first and decelerate stepwise or continuously as the depth of cut becomes deeper so that the cutting load remains approximately constant throughout the entire machining process. In contrast, the circumferential feed rate
F _ROT performs acceleration control from low speed to high speed while maintaining the relationship in equation (1) above. If we illustrate the relationship of the above equation (1), the second
It will look like curve D in the figure. The constant Q in equation (1) is a constant unique to each gear shaping machine, and is a value that sets the curve D in FIG. 2 in a safe area against relieving interference.

Here, how to determine Q and n will be explained. First, the relieving interference region is set as shown in FIG. 2 from graphical analysis and experimental data. Q and n
may be determined so that the above equation (1) does not touch or enter this relieving interference region. However, theoretically, even if it touches or enters the relieving interference area, there is no problem as long as it is outside the relieving interference area in the practical range of the radial feed rate F _RAD and the circumferential feed rate F _ROT . Furthermore, it is not necessary that the above equation (1) strictly follows the relieving interference region as shown in FIG.

According to the method of the invention, the radial feed rate F _RAD
When F ROT is large, the circumferential feed rate F _ROT is automatically reduced, allowing machining to be performed in a safe area away from the cutter's relieving interference area. Therefore, the life of the cutter is extended and the machining accuracy is improved. Furthermore, as the radial feed increases, the machining time is shortened. Note that during simultaneous cutting with radial and circumferential feed, the machining time depends only on the radial feed speed, so even if the circumferential feed decreases to a certain extent, the machining time is not affected.

That is, the gear cutting of the gear shaper can be roughly divided into two modes: () and () below. () E in Fig. 4 where radial and circumferential feeding are performed at the same time→
Tool path mode F: In this case, the cutting time depends on the size of the radial feed rate,
Not affected by circumferential feed rate. () Mode of tool trajectory F→F in FIG. 4 in which only circumferential feed is performed and machining for one rotation of the workpiece is normally performed: The cutting time in this case is influenced by the size of the circumferential feed rate. The present invention targets the above-mentioned () mode in which radial feeding and circumferential feeding are performed simultaneously.
Generally, the circumferential feed rate is the same in the above () mode and () mode, but in the present invention, the circumferential feed rate is controlled by the previous formula (1), so machining is performed using the circumferential feed rate. Time becomes unaffected.

The gear shaping method of the present invention is useful for use in digitally controlled gear shaping machines, NC controlled gear shaping machines, and the like.

An embodiment of the present invention will be described below with reference to FIG. In the example shown in Fig. 3, the depth of cut is divided into three equal parts,
The feed speed is controlled in stages. In Fig. 3, 3 is a control device with a calculation function for a gear shaping machine;
4 is a digital operation panel, 5 is a radial feed servo motor, and 6 is a circumferential feed servo motor. Further, H is the total depth of cut, F _RAD0 is the radial feed rate at the final cut position, and F _ROT0 is the circumferential feed rate at the final cut position, and these are digitally set by the operator on the operation panel 4. F _RAD0 and F _ROT0 are speeds selected to avoid relieving interference at the final cutting position, allowing conventional cutting conditions to be used.
On the other hand, regarding the numerical value n, the value of n is determined so that when F _RAD・F _ROT ⁿ = Q, a circumferential feed F _ROT that does not cause relieving interference even if the radial feed F _RAD is large is obtained. put. This n value is
given to.

In the embodiment shown in FIG. 3, the control device 3 controls the feed rate in stages with respect to the depth of cut, and will be explained in three stages as an example. The control device 3 includes a Q value calculation section 3a in the above equation (1) and a feed rate calculation section 3b.

The Q value calculation unit 3a receives F _RAD0 and F _ROT0 from the operation panel 4.
When the set values are input, the above equation (1) is calculated using these set values to calculate Q, and this is given to the feed rate calculation section 3b.

On the other hand, the feed rate calculation section 3b divides the total cutting depth H input from the operation panel 4 into a predetermined number of divisions, 3 in this example. The first section is the cutting area from 0 to H/3, the middle section is the cutting area from H/3 to 2H/3,
The final section is the cutting area from 2H/3 to H. The feed rate calculation unit 3b multiplies the set value F _RAD0 by a proportionality constant K ₁ of K ₁ > 1 so that the radial feed rate is large in the first cutting section, and calculates K ₁・F _RAD0 as the actual radial feed rate. and command the servo motor 5. In the middle cutting section, set value F _RAD0 is 1<K ₂
<K ₁ is multiplied by a proportional constant K ₂ , and K ₂ ·F _RAD0 is set as the actual radial feed rate and commanded to the servo motor 5 . Set value in the last cutting section
F _RAD0 itself is commanded to the servo motor 5.
In this way, the radial feed is fast at the beginning of the cutting head and slows down as the cutting progresses, so that the cutting load is approximately uniform over the entire cutting stroke near the maximum allowable load, and the radial feed is faster than the conventional constant low-speed radial feed. The cycle time of gear shaping process is shortened and efficiency is increased.

The feed rate calculation unit 3b further calculates the speed according to the cutting section,
A circumferential feed rate is calculated using equation (1) from the constant Q and the radial feed rate in each cutting section, and this is commanded to the servo motor 6 as an actual set value. That is,
In the first cutting section 0 to H/3 (Q/K ₁・F _RAD0 ) ^1/
n , in the middle cutting section H/3 to 2H/3 (Q/K ₂・
F _RAD0 ) ^1/n , in the last cutting section 2H/3~H (Q/
F _RAD0 ) ^1/n = F _ROT is the actual circumferential feed rate. Therefore, in the first cutting section where the radial feed rate is high, the circumferential feed rate is automatically reduced to such an extent that it does not enter the relieving interference region.
This eliminates relieving interference, extends cutter life, and improves machining accuracy.

As mentioned above, in the example shown in Figure 3, the total depth of cut H and the setting values of radial feed and circumferential feed at the final cutting position
If one set of F _RAD0 and F _ROT0 data is given, it will be automatically converted into three types of data as the depth of cut progresses. Note that the number of divisions in the cutting section is not limited to three stages.
Any number of stages of 2 or more may be used.

As explained above, cycle time can be shortened without causing relieving interference by variable control of radial feed rate F _RAD and circumferential feed rate F _ROT while maintaining the relationship F _RAD × (F _ROT ) ⁿ = constant. can do.

[Brief explanation of the drawing]

FIG. 1 is a simplified explanatory diagram of gear shaping processing, FIG. 2 is a graph showing the relationship between relieving interference area and cutting conditions, and FIG. 3 is a configuration diagram of an embodiment of the present invention. FIG. 4 is a diagram for explaining two modes () and () in gear cutting of the gear shaper. In the drawing, 1 is a cutter, 2 is a gear to be cut, 3 is a control device with an arithmetic function for a gear shaping machine, 3a is a Q calculation unit,
3b is a feed rate calculation unit, 4 is a digital operation panel, 5
6 is a radial feed servo motor, and 6 is a circumferential feed servo motor.

Claims (1)

[Claims] 1 Circumferential feed rate F _ROT and radial feed rate F _RAD in gear shaping are calculated using the following formula F _RAD × (F _ROT ) ⁿ = Q where Q is a constant value of 0<n≦1. A gear shaping method characterized by variable control while maintaining relationships.