JP7849042B2 - machine tools - Google Patents

Description

This invention relates to a machine tool.

In machine tools, when grooving a workpiece, the cutting chips generated by the cutting process are often long and connected. These long, connected chips can become entangled with the cutting tool, leading to machining defects and equipment malfunctions.

Conventionally, to solve the problem of chip entanglement, machine tools with a vibratory cutting function, such as the one shown in Patent Document 1, which processes while vibrating the cutting tool in the feed direction, and machine tools with an oscillating cutting function, such as the one shown in Patent Document 2, which moves the cutting tool back once it has cut a predetermined amount into the workpiece, thereby breaking up the chips and preventing continuous chip generation during processing.

Japanese Patent Application Publication No. 6-285701 Japanese Patent Publication No. 2017-182336

However, machine tools with an oscillating cutting function, such as those shown in Patent Document 2 (hereinafter referred to as "conventional examples"), have problems such as long processing times and malfunctions like chips getting stuck between the cutting tool and the workpiece, leading to chip damage. Furthermore, their chip breaking performance is not particularly high.

This invention has been made in view of the problems of the conventional methods described above, and aims to provide a machine tool that shortens processing time compared to oscillating cutting, exhibits high chip breaking performance, and minimizes the occurrence of problems such as damage to the cutting edge (tip) caused by the broken chips getting stuck between the cutting tool and the workpiece.

The gist of this invention will be explained with reference to the attached drawings.

A machine tool comprising a rotary table 1 on which a workpiece W is placed and fixed, a cutting tool 2 for cutting the workpiece W placed and fixed on the rotary table 1, and a coolant ejection unit 3 for ejecting high-pressure coolant toward the vicinity of the cutting edge of the cutting tool 2, wherein the movement of the cutting tool 2 is controlled based on a numerical control program, the cutting edge 2a of the cutting tool 2 does not detach from the workpiece W and is always in contact with the workpiece W, and furthermore, the cutting tool 2 is configured to move while alternately repeating feed movement and stopping according to the numerical control program , and the numerical control program controls the cutting The machine tool is programmed to feed the tool 2 at a constant feed rate for a predetermined time, immediately stop the cutting tool 2 by immediately reducing the feed rate to zero after the predetermined time has elapsed, stop the feeding movement of the cutting tool 2 for a stop time set to be longer than the predetermined time, and immediately resume feeding the cutting tool 2 at the constant feed rate after the stop time has elapsed. Furthermore, the coolant ejection unit 3 is configured such that the high-pressure coolant, set to an ejection pressure of 1 MPa to 10 MPa, is injected into the cutting chips near the cutting edge 2a of the cutting tool 2 during cutting, causing the cutting chips to break up .

As described above, this invention provides a machine tool that shortens processing time compared to oscillating cutting, exhibits high chip-breaking performance, and minimizes the risk of chips getting stuck between the cutting tool and workpiece, leading to problems such as chip damage.

This is an explanatory diagram showing the cutting process in this embodiment. This is an enlarged explanatory diagram of the main parts during the cutting process in this embodiment. This is an enlarged explanatory plan view of the area enclosed by the dotted line in Figure 2. This is an explanatory diagram showing the thickness of the cutting chips generated in this embodiment. This figure shows an example of the operation pattern of the cutting feed stop function in this embodiment. This figure shows an example of the operation pattern of the cutting feed stop function in this embodiment. This figure shows an example of the operation pattern of the cutting feed stop function in this embodiment. This is an illustrative diagram showing the cutting process (operation of the cutting tool) in this embodiment.

A preferred embodiment of the present invention will be briefly described with reference to the drawings, illustrating the operation of the invention.

This invention, based on the feed time and stop time related to the cutting feed movement of the cutting tool 2 set in the numerical control program, performs machining by alternately feeding and stopping the cutting tool 2 during machining. As a result, the thickness of the cutting chips generated by the stopping action of the feed movement becomes thinner, and this thinner chip thickness makes the chips easier to break apart.

Furthermore, as described above, in this invention, the cutting tool 2 performs machining by alternately feeding and stopping based on the feed time and stop time set in the numerical control program during cutting. However, since the cutting edge 2a of the cutting tool 2 does not escape from the workpiece W, there is no loss of return movement as in the conventional example, thereby shortening the machining time and improving productivity.

Furthermore, in this invention, since the high-pressure coolant ejected from the coolant ejection section 3 is sprayed onto the thinned cutting chip, the cutting action of the high-pressure coolant acts on the cutting chip, improving the chip-breaking performance and ensuring reliable breaking of the cutting chip generated by the machining process.

Furthermore, since the high-pressure coolant blows away and removes the fragmented cutting chips in this invention, the likelihood of chips getting stuck between the cutting tool 2 and the workpiece W, causing problems such as damage to the cutting edge 2a, is minimized.

Specific embodiments of the present invention will be described based on the drawings.

This embodiment, as shown in Figure 1, is a machine tool comprising a rotary table 1 for mounting and fixing a workpiece W, a cutting tool 2 for cutting the workpiece W mounted and fixed on the rotary table 1, and a coolant ejection unit 3 for ejecting high-pressure coolant toward the vicinity of the cutting edge 2a (tip 2a) of the cutting tool 2. Specifically, it is an NC machine tool configured so that the movement of the cutting tool 2 is controlled based on a numerical control program. In the figure, reference numeral 4 indicates the jaws for chucking (fixing) the workpiece W, and reference numeral 5 indicates the workbench on which the workpiece W is mounted.

Specifically, the high-pressure coolant ejected from the coolant ejection unit 3 is set to an ejection pressure of 1 MPa to 10 MPa. As shown in Figures 2 and 3, the coolant ejection unit 3 is configured to spray the high-pressure coolant, set to the aforementioned ejection pressure, onto the cutting chips near the cutting edge 2a of the cutting tool 2 during machining.

In other words, this embodiment is configured such that a high-pressure coolant, set to 1 MPa to 10 MPa, is injected (sprayed) onto the cutting chip, thereby generating a cutting (fragmentation) effect on the cutting chip.

Furthermore, this embodiment includes a cutting feed stop function in the numerical control program that controls the feed movement of the cutting tool 2 during machining. This cutting feed stop function causes the cutting tool 2 to move while alternately repeating feed movement and stopping.

Specifically, the cutting feed stop function can be enabled or disabled using an M-code (address used in NC programming) command. By enabling this cutting feed stop function, the cutting tool 2 moves while repeatedly feeding and stopping (speed 0) during the cutting process. When the cutting tool 2 stops, as shown in Figure 4, the thickness of the cutting chips generated by the cutting process is reduced as much as possible, making them easier to break apart.

In other words, if the cutting tool 2 does not stop (i.e., if the feed movement is performed continuously), the chips are generated with the same thickness (t1), as shown by the dashed line in Figure 4. However, if the cutting feed stop function is activated and the feed movement and stopping of the cutting tool 2 are repeated alternately during cutting, the movement speed of the cutting tool 2 gradually decreases as the cutting tool 2 stops. As this movement speed decreases, the thickness of the generated chips gradually decreases, as shown by the solid line in Figure 4. The thickness of the generated chips becomes thinnest (t2) when the cutting tool 2 stops, and the formation of this thin section makes the chips more easily broken apart.

Furthermore, in this embodiment, the feed rate of the cutting tool 2 is determined by the feed override setting, and the feed rate can be changed by changing this feed rate setting.

Specifically, the feed rate is determined by the programmed feed rate and feed time, which are specified as arguments in the program. Similarly, the stop time during which the feed movement is paused is also specified as an argument in the program.

Furthermore, the operation of the cutting tool 2 during the stop time can be selected from two options. The first option, as shown in Figures 5 and 6, is that during the set stop time, the feed rate of the cutting tool 2 gradually (stepwise) decreases from a predetermined speed (specified speed), stops briefly, and then gradually (stepwise) increases the feed rate to reach the predetermined speed (original feed rate).

Specifically, as shown in Figure 5, for example, the specified feed rate is set to 100%, and the feed rate during the stop time is set to a stepwise deceleration/acceleration ratio in the following order: 100% → 95% → 80% → 50% → 25% → 5% → 0% → 5% → 25% → 50% → 80% → 95% → 100%. This is how the aforementioned operation is performed.

Furthermore, in this operation, as shown in Figure 6 , if the stopping time is set to a long time, not only is the time at speed 0 increased, but the time at each stage also increases, resulting in an overall increase in the time it takes to reach speed 0 and the time it takes to return to the specified speed. In other words, the deceleration time and acceleration time are both increased (programmed).

The second method, as shown in Figure 7, involves the cutting tool 2 stopping immediately without any reduction in feed rate when the stop time is reached. The feed movement of the cutting tool 2 is then stopped for the set stop time, and immediately resumes feed movement at the specified speed once the stop time has elapsed.

Specifically, if the specified feed rate is set to 100%, the aforementioned operation is executed by setting it in the order of 100% → 0% → 100%.

Furthermore, as shown in Figures 5-7, the feed time and stop time in the cutting feed stop function are set so that the stop time is longer than the feed time.

In other words, this embodiment shortens the length of the cutting chips generated by shortening the feed time (because the length of the cutting chips generated by cutting is proportional to the feed time), and improves the fragmentation ability by extending the period in which the thickness of the cutting chips is thinned by extending the stop time. As a result, the cutting chips generated during cutting can be reliably fragmented at short intervals.

The following is a comparative evaluation supporting the effects of this embodiment.

This evaluation compared the machining time when cutting a workpiece under equivalent cutting conditions in this embodiment and the conventional example. In this embodiment, an additional process is added during cutting: high-pressure coolant, set to a discharge pressure of 8 MPa, is injected (water-sprayed) onto the cutting chips from the coolant ejection unit 3.

Table 1 shows the cutting conditions and machining time for this embodiment and the conventional example, and Figure 8 is an illustrative diagram showing the working state (operation of the cutting tool 2) in this embodiment.

In this embodiment, under the cutting conditions, the operation of the cutting tool 2 during the stop time was set to a pattern where the feed rate gradually decreased and then gradually increased, as shown in Figure 5. Therefore, the stop time includes the time spent decelerating and increasing the feed rate.

As shown in Table 1, when machining was performed under equivalent cutting conditions, the machining time for this embodiment was 32 minutes, while the machining time for the conventional example was 76 minutes.

Thus, this embodiment demonstrated that the processing time was 44 minutes shorter than that of the conventional example, confirming that the processing time could be reduced to less than half.

Furthermore, in this embodiment, as shown in Figure 8, the cutting chips were broken up at each stopping time when the feed movement of the cutting tool 2 was stopped, generating short pieces of chips. These generated chips were removed (blown away) by the high-pressure coolant, preventing them from becoming entangled with the cutting tool 2 or trapped between the cutting tool 2 and the workpiece W, thus confirming a good machining condition.

Thus, this embodiment dramatically reduces processing time compared to conventional oscillating cutting processes. Furthermore, it exhibits high chip-breaking performance, and since the broken chips are blown away and removed by high-pressure coolant, the risk of chips getting stuck between the cutting tool and workpiece, leading to chip damage and other problems, is significantly reduced. This results in a groundbreaking machine tool with superior productivity.

Furthermore, as described above, this embodiment breaks up cutting chips through the interaction between the cutting feed stop function and high-pressure coolant. Therefore, it is not necessary to use ultra-high-pressure coolant (approximately 14 MPa to 20 MPa), and sufficient effect can be obtained with high-pressure coolant of approximately 1 MPa to 10 MPa, thereby reducing equipment costs.

Furthermore, the present invention is not limited to this embodiment, and the specific configuration of each constituent element can be designed as appropriate.

1 Rotary table 2 Cutting tool 2a Cutting edge 3 Coolant outlet W Workpiece

Claims (1)

A machine tool comprising a rotary table for mounting and fixing a workpiece, a cutting tool for cutting the workpiece mounted and fixed on the rotary table, and a coolant ejection unit for ejecting high-pressure coolant toward the vicinity of the cutting edge of the cutting tool, wherein the movement of the cutting tool is controlled based on a numerical control program, the cutting edge of the cutting tool does not detach from the workpiece during cutting and is always in contact with the workpiece, and furthermore, the cutting tool is configured to move while alternately repeating feed movement and stopping according to the numerical control program, and the numerical control program controls the cutting The machine tool is programmed to feed the tool at a constant feed rate for a predetermined time, immediately stop the cutting tool by immediately reducing the feed rate to zero after the predetermined time has elapsed, and to stop the feeding movement of the cutting tool for a stop time set to be longer than the predetermined time, and immediately resume feeding the cutting tool at the constant feed rate after the stop time has elapsed, and furthermore, the coolant ejection unit is configured such that the high-pressure coolant, set to an ejection pressure of 1 MPa to 10 MPa, is injected into the cutting chips near the cutting edge of the cutting tool during cutting, thereby breaking up the cutting chips .