JP2009136956A - Turning method, turning condition and cutting path generation method - Google Patents

Abstract

The present invention provides a turning method capable of suitably suppressing chatter vibration even in a machining path parallel to a spindle while maintaining finishing accuracy of a machined surface.
An axial direction per one rotation of the spindle of the cutting tool 5 so that a current cutting position by the cutting tool 5 does not overlap with a cutting trace left on a workpiece turning surface by turning up to one rotation of the spindle. The first step for setting the feed amount to the workpiece, the second step for turning while feeding the cutting tool 5 in the axial direction with the feed amount A set in the first step, and the machining for which the turning processing was performed in the second step The cutting tool 5 is advanced in the radial direction from the spindle rotation phase rotated about 180 ° from the spindle rotation phase at the start of cutting in the second step with respect to the surface at a spindle rotation speed different from the spindle rotation speed in the second step. And a third step of performing turning again.
[Selection] Figure 1

Description

  The present invention relates to a turning method capable of suppressing chatter vibration generated during turning, particularly regenerative chatter vibration in a machine tool such as an NC lathe, and turning conditions and cutting for carrying out the turning method. The present invention relates to a route generation method.

  For example, in an NC lathe, a workpiece is gripped by a rotatable main shaft, and the workpiece is rotated together with the main shaft, and at the same time, the outer diameter machining (turning) of the workpiece is performed by sending a cutting tool in the axial direction. In this turning process, there is a case in which “chat vibration” in which the work and / or the cutting tool vibrates is generated by being affected by the rigidity of the work and the cutting tool, cutting conditions (for example, cutting depth, feed speed, spindle rotation, etc.). is there. Among these “chatter vibrations”, “regenerative chatter vibration”, which is self-excited vibration, not only deteriorates the finishing accuracy of the workpiece machining surface, but also causes cutting tool defects, and has been a problem in the past.

Therefore, in order to suppress the “chatter vibration” as described above, for example, a turning method as described in Patent Documents 1 to 3 has been proposed.
The turning method described in Patent Document 1 is intended to suppress “chatter vibration” by periodically changing the rotation speed of the workpiece when turning the workpiece. Further, the turning method described in Patent Document 2 is intended to suppress “chatter vibration” by applying an axial tensile force to the workpiece and reducing the escape of the workpiece during turning.
Furthermore, the turning method described in Patent Document 3 automatically generates a cutting path that does not generate chatter vibration in the cutting path of the downward part of the workpiece.

JP-A-49-105277 JP-A-9-290301 JP-A-5-324035

However, in the turning method described in Patent Document 1, since the rotational speed of the spindle is changed during processing, there is a problem in that streaks due to the change in the rotational speed are likely to remain on the work surface of the workpiece and the finishing accuracy is deteriorated. is there.
In addition, since the turning method described in Patent Document 2 requires a separate device for pulling the workpiece, there are problems such as high cost, an increase in the number of processes, and an increase in the size of the entire device. For this reason, there is a problem that it can be applied only to a workpiece having a relatively long axial length, and there is a problem in versatility.
The turning method described in Patent Document 3 has a problem that chatter vibrations in a machining path parallel to a general main axis cannot be suppressed, although chatter vibrations in the descending part of the workpiece can be avoided.

  Therefore, in view of the above problems, the present invention provides a turning method and a turning method capable of suitably suppressing chatter vibration even in a machining path parallel to the spindle while maintaining the finishing accuracy of the machining surface. An object of the present invention is to provide a turning condition and a cutting path generation method for carrying out.

In order to achieve the above object, the first invention described in claim 1 is directed to a workpiece by feeding a cutting tool in the axial direction or the radial direction of the spindle while rotating the workpiece attached to the rotatable spindle. A turning method in which turning is performed so that the current cutting position of the cutting tool does not overlap the cutting trace left on the workpiece turning surface by turning up to one rotation of the main spindle. A first step for setting the feed amount in the axial direction per rotation, a second step for turning while feeding the cutting tool in the axial direction at the feed amount set in the first step, and turning in the second step With the feed set in the first step, the cutting tool is advanced in the radial direction from the spindle rotation phase rotated about 180 ° from the spindle rotation phase at the start of cutting in the second step with respect to the machining surface performed. A third step of performing again the turning in a two-step spindle rotation speed different spindle speed, and having a.
In order to achieve the above-mentioned object, the second invention according to claim 2 is a predetermined number of times with respect to the workpiece by feeding the cutting tool in the axial direction of the spindle while rotating the workpiece attached to the rotatable spindle. This is a turning method that performs turning, and the workpiece turning surface is turned by turning the current cutting position of the cutting tool up to one revolution before the main spindle, based on the finished surface roughness, cutting tool shape, and workpiece cutting allowance. The first step of setting the feed amount per rotation of the spindle of the cutting tool and the spindle rotation phase are equally divided by a predetermined number of times so as not to overlap the cutting traces left above, and each phase after the division Is set to the cutting start position of each turning process, and the cutting tool is fed in the axial direction with the feed amount set in the first step from each cutting start position set in the second step, and the previous turning A third step of performing each turning the spindle speed during working at different spindle speed, and having a.

In order to achieve the above object, a third invention described in claim 3 is a method for generating a turning condition and a cutting path for carrying out the turning method described in claim 1, wherein at least the workpiece shape and A first step for storing initial parameters including a desired workpiece finish surface roughness, a cutting tool shape, and a spindle rotation speed in the storage means; and a current cutting by the cutting tool from the initial parameters stored in the first step. Set the cutting line by calculating the feed amount in the axial direction per spindle revolution of the cutting tool so that the position does not overlap the cutting trace left on the workpiece turning surface by turning up to one revolution of the spindle A second step, a third step for setting a plurality of cutting positions at a spindle rotation phase different from each other by about 180 °, and a spindle rotation speed different from the spindle rotation speed at the previous turning. A fourth step of, characterized by having a.
In order to achieve the above object, a fourth invention according to claim 4 is a method for generating a turning condition and a cutting path for carrying out the turning method according to claim 2, wherein at least a workpiece finish surface is provided. A first step of storing in the storage means initial parameters including the roughness, the shape of the cutting tool, the machining allowance of the workpiece, and the spindle rotation speed, and the initial parameters stored in the first step, The cutting position is calculated by calculating the feed amount in the axial direction per spindle revolution of the cutting tool so that the cutting position does not overlap with the cutting trace left on the workpiece turning surface by turning until one revolution of the spindle A second step for setting the spindle, a third step for equally dividing the spindle rotation phase by a predetermined number of times and setting each phase as a cutting position of the cutting line, and a spindle rotating speed during the previous turning process And having a fourth step of setting a different spindle speed.

According to the turning method of the present invention, when a cutting tool is advanced in the radial direction and the turning process is performed again on the machined surface after cutting, it is approximately 180 from the spindle rotation phase at the start of the previous turning operation. Since the turning process is started from the rotated spindle rotation phase, the current turning range by the cutting tool does not overlap with the turning trace of the previous rotation, which is caused by the undulations left uncut by the previous turning. Regenerative chatter vibration does not occur. In addition, since the spindle rotation speed in the current turning process is set to avoid the spindle rotation speed in the previous turning process, the regenerative chatter vibration caused by the undulations generated during the previous turning process is not stopped. Therefore, the occurrence of regenerative chatter vibration can be suppressed, and effects such as prevention of tool breakage can be achieved.
Particularly, according to the turning method described in claim 2, since the cutting conditions are set in consideration of the desired workpiece finish surface roughness, chatter vibration is avoided and the desired finish surface roughness is obtained. In addition, regardless of the machining path, a good finished surface can be machined by a machining path that is parallel to the spindle or down or up.
According to the turning condition and cutting path generation method of the present invention, it is possible to automatically generate turning conditions and a cutting path that avoid chatter vibration so that a desired workpiece finish surface roughness can be obtained. There is no need to make settings and the workload is reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing a machining situation in the turning method according to the first invention, and is applied to a machine tool such as an NC lathe.
In FIG. 1, reference numeral 1 denotes a main shaft that is rotatably provided. A chuck 2 having a claw 3 is attached thereto, and the work 4 can be gripped by the claw 3. Turning (outer diameter machining) on the workpiece 4 rotates the workpiece 4 attached to the chuck 2 together with the main shaft 1, while cutting the cutting tool 5 cut into the outer peripheral surface of the workpiece 4 along the axial direction of the main shaft 1. Done by sending. The operation of the rotation 1 of the spindle and the feeding operation of the cutting tool 5 are controlled by an NC device (not shown).

  Here, "regenerative chatter vibration" means that the undulation caused by the previous uncut material that occurs within the cutting range of the cutting tool affects the cutting force during the current cutting, and the vibration is fed back and expanded. It is a phenomenon. Once regenerative chatter vibration occurs, large undulations remain on the workpiece finish surface, which not only deteriorates the finishing accuracy, but also causes serious problems such as breakage of the cutting tool.

  FIG. 2 is an explanatory diagram showing the path of the cutting tool. The previous machining is indicated by 6 and leaves a spiral trajectory on the workpiece. The feed amount of the cutting tool per spindle revolution at this time is set so that the current turning range does not overlap with the turning trace before one revolution. That is, in FIG. 1, the cutting tool feed amount per one rotation of the spindle based on the following formula (1), with the corner radius r, corner angle α, side cutting edge angle β, and workpiece cutting allowance d as initial parameters in FIG. A is calculated.

  Next, when turning the tool again in the radial direction and turning again, as shown by 7 in FIG. 2, turning is performed from the spindle rotation phase rotated 180 ° from the spindle rotation phase at the start of the previous turning operation. To implement. 3A shows the cutting trace left on the workpiece 4 in this turning process, and FIG. 3B shows the cutting trace left on the workpiece 4 in the turning process when the spindle rotation phase at the start of cutting is not shifted by 180 °. The cutting traces made by the previous machining are indicated by dotted lines, and the cutting traces obtained by the current cutting are indicated by solid lines. In (A), the spindle rotation phase at the start of cutting is shifted by 180 ° between the previous time and this time, so the cutting marks are shifted by half of the tool shape between the previous time and this time, and the adjacent cutting marks are overlapped. Absent. Accordingly, there is no regenerative chatter vibration due to the undulations left uncut during turning one revolution. However, when the main spindle rotation phase is not shifted by 180 ° (B), as shown by the hatched portion, there is a possibility that the adjacent cutting traces are overlapped and regenerative chatter vibration is generated.

  Further, here, when the tool is advanced and cut in the radial direction, a spindle rotation speed different from the previous spindle rotation speed is set. Thereby, since the feedback loop of chatter vibration is not established, it is possible to suppress regenerative chatter vibration caused by undulations in the previous turning process.

As described above, according to the turning method of the above aspect, the current cutting position by the cutting tool 5 is not overlapped with the cutting trace left on the turning surface of the work 4 by turning before one rotation of the spindle. , Set the feed amount in the axial direction per rotation of the spindle of the cutting tool 5, perform turning while feeding the cutting tool 5 in the axial direction with the set feed amount, From the spindle rotation phase rotated approximately 180 ° from the spindle rotation phase at the start of the previous turning, the cutting tool 5 is advanced in the radial direction and again at a spindle rotation speed different from the spindle rotation speed at the previous turning. By performing the turning process, the current turning range by the cutting tool 5 does not overlap with the turning trace before one rotation, so that the regenerative chatter vibration due to the undulations left uncut during the one-turn turning does not occur . In addition, since the spindle rotation speed in the current turning process is set to avoid the spindle rotation speed in the previous turning process, regenerative chatter vibration due to the undulation that occurred during the previous turning process does not occur. Therefore, the occurrence of regenerative chatter vibration can be suppressed, and effects such as prevention of tool breakage can be achieved.
The above-mentioned turning method is suitable for rough machining because it has a merit that the amount of chips discharged per unit time is large and high-efficiency machining, but the finished surface roughness is not taken into consideration.

On the other hand, when accuracy is required for the finished surface, the turning method of the second invention is used.
Here, the feed amount per rotation of the main spindle that does not overlap with the cutting trace before one rotation is calculated from the desired workpiece finish surface roughness, cutting tool shape, and workpiece cutting allowance, and the feed direction is used in the radial direction. Performs multiple turning without changing the cutting position. At this time, different rotational speeds are set for each of the plurality of turnings, and the turning process is started from a phase obtained by equally dividing the phase of the spindle at the start of the cutting.
FIG. 4 shows an explanatory diagram of the cutting tool path at this time, and a specific numerical value is substituted for explanation. For example, desired workpiece finish surface roughness Rz = 0.01 [mm], tool corner radius r = 1 [mm], corner angle α = 90 °, side cutting edge angle β = 45 °, workpiece cutting allowance d = 0 .4 [mm], the feed amount per rotation of the main spindle that does not overlap with the cutting trace before one rotation is calculated as 1.63 [mm] from the previous equation (1). On the other hand, the pitch p for obtaining a desired finished surface roughness is approximated by the following equation (2) and is 0.28 [mm].

Therefore, since A / p = 5.82, the machining is performed six times rounded up after the decimal point without changing the radial cutting position. Again, the six spindle revolutions are different from the previous values to avoid chatter vibration. The spindle rotation phase at the start of workpiece cutting is set to every 60 ° obtained by dividing 360 ° by 6 times of cutting. That is, as shown in FIG. 4, when the first turning trajectory is a, it is shifted by 60 ° to b, and further shifted by 60 ° to c,.
FIG. 5 is a diagram showing the cutting traces left on the workpiece. Here, when the first cutting trace a is viewed, the first rotation cutting trace a1 and the second rotation cutting trace a2 do not overlap. Regenerative chatter vibration does not occur. Moreover, although a1 overlaps with the cutting trace b1 of the first rotation of the second cutting, the occurrence of chatter vibration can be avoided because the machining is performed at a different rotational speed. As described above, it is possible to set processing conditions for obtaining a desired finished surface roughness without generating chatter vibration.

As described above, also in the turning method of the second invention, the current cutting position by the cutting tool 5 is until one rotation before the main shaft, based on the workpiece finish surface roughness, the shape of the cutting tool 5, and the workpiece cutting allowance. Set the feed amount per rotation of the spindle of the cutting tool 5 so that it does not overlap with the cutting trace left on the workpiece turning surface by turning, and divide the spindle rotation phase equally by a predetermined number of times. Are set as the cutting start position of each turning process, and the cutting tool 5 is fed in the axial direction with the previously set feed amount from each set cutting start position, and the spindle rotational speed during the previous turning process By turning each with a different spindle rotation speed, the current turning range by the cutting tool 5 does not overlap with the turning trace of the previous rotation, resulting from the undulations left uncut by the previous turning. Regenerative chatter vibration does not occur . In addition, since the spindle rotation speed in the current turning process is set to avoid the spindle rotation speed in the previous turning process, the regenerative chatter vibration caused by the undulations generated during the previous turning process is not stopped. Therefore, the occurrence of regenerative chatter vibration can be suppressed, and effects such as prevention of tool breakage can be achieved.
In particular, since the cutting conditions are set in consideration of the desired workpiece finish surface roughness, chatter vibration is avoided and the desired finish surface roughness is obtained. In addition, regardless of the machining path, a good finished surface can be machined by a machining path that is parallel to the spindle or down or up.

Next, a turning condition and a cutting path generation method for automatically generating a turning condition and a cutting path for performing the above-described turning method based on at least the work shape, a desired workpiece finish surface roughness, and the cutting tool shape Will be described by specifically substituting numerical values with reference to the flowchart of FIG.
First, the operator has a workpiece shape D1 = 30 [mm], a desired workpiece finish surface roughness Rz = 0.01 [mm], a corner radius r = 1 [mm] as a cutting tool shape, and a corner angle α = 90. °, horizontal cutting edge angle β = 45 °, material shape D2 = 34 [mm], finishing allowance d1 = 0.2 [mm], rough cutting depth d2 = 0.5 [mm], spindle speed S = 1000 [min ⁻¹ ] is input to the NC device as an initial parameter (step 1, expressed as “S 1” in FIG. 6, and so on).

Next, the presence or absence of cutting residue is confirmed in the roughing setting (step 2). If there is a cutting residue, a cutting line L1 shifted by the roughing cutting amount d2 is set (step 3), and roughing cutting condition setting is performed. Thus, the spindle rotation speed and the spindle rotation phase at the start of cutting on the workpiece are set (step 4). The first spindle rotation speed is set to an initial value S = 1000 [min ⁻¹ ], and the spindle rotation phase at the start of cutting on the workpiece is set to 0 °, and is recorded in the memory unit of the NC device serving as a storage unit. The values recorded in the NC device are shown in FIG.
Next, returning to step 2, if there is any remaining cutting, step 3 further shifts by the roughing cutting amount d2 to set the cutting line L2. In the next roughing cutting condition setting (step 4), avoiding the previous spindle rotation speed, for example, it is reduced by 5% to 950 [min ⁻¹ ], and the spindle rotation phase at the start of cutting is 180 °. In this example, roughing is repeated four times, and the spindle rotation speed at this time is alternately set to 1000 [min ⁻¹ ] and 950 [min ⁻¹ ]. The process so far corresponds to the third invention.
After the rough machining is performed four times in this way, when there is no cutting residue with a finishing allowance, the process proceeds to finishing machining cutting condition setting (step 5).

  The cutting line and cutting conditions are set according to the fourth invention. Here, the machining allowance of the workpiece is 0.7 [mm] by adding the value of the rough cutting depth d2 = 0.5 [mm] to the finishing allowance d1 = 0.2 [mm]. First, the feed amount per one revolution of the spindle that does not overlap with the cutting trace before one revolution is calculated as 2.23 [mm] from the equation (1). On the other hand, the pitch p for obtaining the desired finished surface roughness is 0.28 [mm] from the equation (2). Since A / p = 7.96, eight machining rounded up after the decimal point is set. The spindle rotation phase at the start of cutting is set to 45 ° obtained by dividing 360 ° by 8 times of cutting, and the spindle rotation speed is set to a value different from the previous value in order to avoid chatter vibration.

  As described above, according to the above-described turning condition and cutting path generation method, the turning condition and the cutting path that avoid chatter vibration can be automatically generated so that a desired workpiece finish surface roughness can be obtained, and the operator can perform complicated calculation. It is no longer necessary to set the cutting conditions and the work load is reduced.

In the above-described embodiment, an example applied to outer diameter turning is described, but the turning method according to the present invention is also effective for inner diameter turning, end face turning, and tapered surface and curved surface machining. Can be applied.
In the first aspect of the invention, in the above embodiment, the turning is started from the spindle rotation phase rotated by 180 ° from the spindle rotation phase at the start of the previous turning incision. The position where the peak of the peak of the machining surface generated by the tool path coincides with the position of the valley of the machining surface generated by the previous machining is good. This value varies depending on the tool shape, but in most cases, it may be 180 °. Further, this spindle rotation phase may be a value slightly deviated from 180 °. That is, if it is 180 °, regenerative chatter vibration can be avoided reliably, but if the main shaft rotational phase shift is slight, there may be a slight overlap of cutting traces and regenerative chatter vibration may not occur. Therefore, in such a case, a value slightly deviated from 180 ° is acceptable.

Furthermore, the turning conditions and the cutting path generation method of the above embodiment have been described in the examples in which the third and fourth inventions are implemented. However, in the case where only either roughing or finishing is performed, each is independent. In the invention, the turning conditions and the cutting path may be automatically generated.

It is explanatory drawing of the processing condition in the turning method which concerns on this invention. It is explanatory drawing which shows the cutting tool path | route with respect to a workpiece | work. (A) is explanatory drawing which shows the cutting trace without the duplication left on the workpiece | work, (B) is explanatory drawing which shows the cutting trace with the duplication remaining on the workpiece | work. It is explanatory drawing which shows the cutting tool path | route with respect to the workpiece | work at the time of dividing | segmenting the spindle rotational phase at the time of a cutting start into 6 equal parts. It is explanatory drawing which shows the cutting trace left on the workpiece | work by the process of FIG. It is a flowchart explaining the method of producing | generating a turning condition and a cutting path automatically. It is a table | surface explaining the value set by the method shown in FIG.

Explanation of symbols

  1 .... Spindle, 2 .... Chuck, 4 .... Work, 5 .... Cutting tool, 6 .... Previous tool path, 7 .... Set tool path, A ... Axial feed amount, .alpha. , Β ·· Horizontal cutting edge angle, r · Corner radius, d ·· Work cutting allowance.

Claims (4)

A turning method for performing a turning process on the workpiece by sending a cutting tool in an axial direction or a radial direction of the spindle while rotating a workpiece attached to a rotatable spindle,
In the axial direction per one rotation of the main shaft of the cutting tool, the current cutting position by the cutting tool does not overlap the cutting trace left on the workpiece turning surface by the turning up to one rotation of the main shaft. A first step of setting the feed amount of
A second step of performing turning while feeding the cutting tool in the axial direction at the feed amount set in the first step;
The cutting tool is advanced in the radial direction from the spindle rotation phase rotated about 180 ° from the spindle rotation phase at the start of cutting in the second step with respect to the machining surface that has been turned in the second step, and the first step A third step of turning again at a spindle rotational speed different from the spindle rotational speed of the second step with the feed set in
A turning method characterized by comprising: A turning method that performs a predetermined number of turnings on the workpiece by rotating a workpiece attached to the rotatable spindle while sending a cutting tool in the axial direction of the spindle,
From the workpiece finish surface roughness, the shape of the cutting tool, and the machining allowance of the workpiece, the current cutting position by the cutting tool is left on the workpiece turning surface by turning up to one rotation before the main spindle. A first step of setting a feed amount per rotation of the spindle of the cutting tool so as not to overlap with a cutting trace that is present;
A second step of equally dividing the spindle rotation phase by the predetermined number of times, and setting each phase after the division to a cutting start position of each turning process;
From each incision start position set in the second step, while turning the cutting tool in the axial direction with the feed amount set in the first step, each turning operation is performed at a spindle rotation speed different from the spindle rotation speed at the previous turning. A third step to perform;
A turning method characterized by comprising: A method for generating a turning condition and a cutting path for performing the turning method according to claim 1,
A first step of storing in the storage means initial parameters including at least a workpiece shape, a desired workpiece finish surface roughness, a cutting tool shape, and a spindle rotation speed;
Based on the initial parameters stored in the first step, the cutting position of the cutting tool is set so that the current cutting position by the cutting tool does not overlap with the cutting trace left on the workpiece turning surface by turning up to one rotation of the spindle. A second step of calculating a feed amount in the axial direction per one rotation of the spindle and setting a cutting line;
A third step of setting a plurality of cutting positions at spindle rotation phases different from each other by approximately 180 °;
A fourth step of setting a spindle rotational speed different from the spindle rotational speed at the time of the previous turning,
A turning condition and a cutting path generation method characterized by comprising: A method for generating a turning condition and a cutting path for performing the turning method according to claim 2,
A first step of storing in the storage means initial parameters including at least the workpiece finish surface roughness, the shape of the cutting tool, the machining allowance of the workpiece, and the spindle rotation speed;
Based on the initial parameters stored in the first step, the cutting position of the cutting tool is set so that the current cutting position by the cutting tool does not overlap with the cutting trace left on the workpiece turning surface by turning up to one rotation of the spindle. A second step of calculating a feed amount in the axial direction per one rotation of the spindle and setting a cutting line;
A third step of dividing the spindle rotation phase into equal parts by a predetermined number of times and setting each phase as a cutting position of a cutting line;
A fourth step of setting a spindle rotational speed different from the spindle rotational speed at the time of the previous turning,
A turning condition and a cutting path generation method characterized by comprising:

Images