JP7161254B2 - Processing method, processing equipment and program - Google Patents

Description

The present disclosure relates to techniques for forming a finished surface using an end mill.

A rotary tool such as a ball end mill having an R shape on the tip side is often used for finishing. Patent Literature 1 discloses a technique for finishing a mold that requires a draft using a ball end mill.

FIG. 1 shows how a vertical wall of a mold with a draft angle is finished with a ball end mill. In this finishing process, a step of rotating the ball end mill and feeding it along the wall surface in a predetermined feed direction to cut the work material and a step of pick-feeding the ball end mill in the predetermined pick-feed direction are repeated.

A ball end mill has a hemispherical ball portion at its tip. Assuming that the radius of the ball portion is r and the feed amount in the pick feed direction (pick feed amount) is fp, the finished surface roughness R of the vertical wall surface is expressed by the following equation.
R ⁼ fp2/(8r)
From this formula, it can be seen that by reducing the pick feed amount fp, it is possible to create a finished surface with high precision and high quality in an ideal state in which there is no displacement of the ball end mill.

Japanese Patent No. 5963292

When machining the wall surface of the mold, it is often necessary to use a tool that protrudes long and has low dynamic rigidity. In the finishing process for wall surfaces, etc., it is not easy to stably perform high-precision machining because the deflection of the tool in the direction where the dynamic rigidity is low has a large effect on the machining accuracy.

The present disclosure has been made in view of such circumstances, and an object thereof is to provide a technique for forming a finished surface with high accuracy using an end mill.

In order to solve the above problems, a machining method according to an aspect of the present disclosure includes a first step of cutting a work material by rotating an end mill having an R shape on the tip side and feeding the work material relatively to the work material. and the second step of pick-feeding (moving in the pick-feed direction) the end mill with respect to the work material are repeated to cut the work material. In this processing method, areas other than a partial area of the finished surface formed by one cutting edge are removed by subsequent cutting. In this machining method, from the timing when one cutting edge cuts into the work material to the timing when the cutting edge exits the work material, the formation of the partial region is performed more than the timing when the cutting edge exits the work material. Complete by a timing close to the timing of cutting.

A processing apparatus according to another aspect of the present disclosure is a processing apparatus that cuts a work material, and includes a rotation mechanism that rotates a main spindle having an end mill having an R shape on the tip side, and an end mill for the work material. a feed mechanism for relatively moving the end mill, a first step of controlling the operations of the rotation mechanism and the feed mechanism to feed the end mill relatively to the work material while rotating it, and cutting the work material; and a control device for repeating a second step of pick-feeding the to the work material. In the processing by this processing device, the area other than the partial area of the finished surface formed by one cutting edge is removed by subsequent cutting. The control device cuts the formation of the partial region from the timing when one cutting edge cuts into the work material to the timing when the cutting edge comes out of the work material than the timing when the cutting edge comes out. Complete by the timing close to the timing.

Yet another aspect of the present disclosure is an end mill having a rounded shape on the tip side. This end mill repeats a first step of feeding the end mill relative to the work material while rotating to cut the work material, and a second step of pick-feeding the end mill with respect to the work material. It is used for finish machining of work materials, and has a right edge left twist shape or a left edge right twist shape.

Yet another aspect of the present disclosure is a processing method in which an end mill is rotated and fed relatively to the work material to cut the work material to form a finished surface, wherein the helix angle of the cutting edge is A 0 degree end mill is used to perform up-cutting.

It should be noted that any combination of the above-described components and expressions of the present disclosure converted between methods, devices, systems, etc. are also effective as aspects of the present disclosure.

ADVANTAGE OF THE INVENTION According to this indication, the technique for forming a finished surface with high precision using an end mill can be provided.

It is a figure which shows a mode that the vertical wall of a metal mold|die is finish-processed with a ball end mill. It is a figure which shows the processing apparatus of embodiment. It is a figure which shows the external appearance of a ball end mill. It is a figure for demonstrating the outline|summary of the processing method used as a comparative technique. It is a figure for demonstrating the process in which a finished surface is removed. FIG. 5 is a diagram showing analysis results of cutting force and tool displacement during machining in a comparative technique; It is a figure which shows the analysis result of the processing error in a comparison technique. FIG. 5 is a diagram showing analysis results of cutting force and tool displacement during machining in a comparative technique; It is a figure which shows the finishing process procedure in embodiment. 1 is a diagram showing the appearance of a ball end mill in Example 1. FIG. 4 is a diagram showing analysis results of cutting force and tool displacement during machining in Example 1. FIG. FIG. 10 is a diagram showing analysis results of machining errors in Example 1; FIG. 10 is a diagram for explaining an outline of a processing method according to Example 2; FIG. 10 is a diagram showing analysis results of cutting force and tool displacement during machining in Example 2; FIG. 10 is a diagram showing analysis results of machining errors in Example 2; FIG. 11 is a diagram for explaining an outline of a processing method according to Example 3; FIG. 10 is a diagram showing how the improved ball end mill used in Example 3 cuts. It is a figure for demonstrating the outline|summary of the processing method by a modification.

FIG. 2 shows the processing device 1 of the embodiment. The processing device 1 includes a machine tool device 10 and a control device 100 . The control device 100 may be an NC control device that controls the machine tool device 10 according to an NC (numerical control) program, and the machine tool device 10 may be an NC machine tool controlled by the NC control device. In the processing apparatus 1, the machine tool device 10 and the control device 100 may be configured as separate bodies and connected by a cable or the like, but may be configured as an integrated unit.

The machine tool device 10 includes a bed portion 12 and a column portion 14, which are main body portions. A first table 16 and a second table 18 are movably supported on the bed section 12 . The first table 16 is movably supported in the Y-axis direction by rail portions formed on the bed portion 12, and the second table 18 is movably supported in the X-axis direction by rail portions formed on the first table 16. Supported. A workpiece setting surface is provided on the upper surface of the second table 18, and a workpiece 62 to be machined is fixed to the workpiece setting surface. The work material 62 may be a metal material for a mold having standing walls before finish machining, that is, having pre-machined standing walls. The processing apparatus 1 of the embodiment finishes the vertical wall of the work material 62 to form a vertical wall having a draft angle. may be used.

The Y-axis motor 22 rotates the ball screw mechanism to move the first table 16 in the Y-axis direction, and the X-axis motor 20 rotates the ball screw mechanism to move the second table 18 in the X-axis direction. do. The Y-axis sensor 32 detects the position of the first table 16 in the Y-axis direction, and the X-axis sensor 30 detects the position of the second table 18 in the X-axis direction.

A spindle 46 to which a cutting tool 50 is attached is provided above the second table 18 . In the embodiment, an end mill tool having an R shape on the tip side is attached to a chuck provided on the spindle 46 . Such end mill tools are typically ball end mills, but may also be radius end mills or barrel end mills. A spindle motor 40 rotates a spindle 46 , and a spindle sensor 42 detects the rotational speed of the spindle motor 40 . The spindle 46 and the spindle motor 40 are fixed to the spindle support 44 .

The main shaft support portion 44 is supported movably in the Z-axis direction by a rail portion formed on the column portion 14 on the back side thereof. The Z-axis motor 24 rotates the ball screw mechanism to move the main shaft 46 in the Z-axis direction. The Z-axis sensor 34 detects the position of the spindle 46 in the Z direction.

The first tilt motor 52 rotates the gear mechanism to tilt the main shaft support 44 about an axis perpendicular to the main shaft 46 and the Y-axis. A tilt sensor 56 detects the tilt angle of the main shaft 46 . The second tilting motor 54 rotates the gear mechanism to tilt the main shaft support 44 about an axis parallel to the Y-axis. A tilt sensor (not shown) separate from the tilt sensor 56 detects the tilt angle of the main shaft 46 .

The control device 100 drives and controls the X-axis motor 20, the Y-axis motor 22, the Z-axis motor 24, the first tilt motor 52, the second tilt motor 54 and the main shaft motor 40 according to the NC program. The control device 100 acquires detection values detected by each of the X-axis sensor 30, Y-axis sensor 32, Z-axis sensor 34, tilt sensor, and spindle sensor 42, and reflects them in drive control of each motor.

In the machine tool device 10 shown in FIG. 2, the work piece 62 is moved in the X-axis direction and the Y-axis direction by the X-axis motor 20 and the Y-axis motor 22, respectively, and the cutting tool 50 is moved in the Z-axis direction by the Z-axis motor 24. However, these movements need only be relative between the cutting tool 50 and the work material 62 . That is, in the machine tool device 10, the cutting tool 50 may be moved in the X-axis direction and the Y-axis direction, and the cut material 62 may be moved in the Z-axis direction. In the machine tool device 10, the cutting tool 50 is tilted with respect to the workpiece 62 by the first tilting motor 52 and the second tilting motor 54. These tilting motors may be provided on the bed portion 12 side. good. In this way, it does not matter which of the cutting tool 50 and the work material 62 is moved. Mechanisms for realizing such movement are collectively called "feeding mechanisms".

FIG. 3 shows the appearance of the ball end mill. A ball end mill has a hemispherical ball portion and a cylindrical portion connected to the ball portion. As will be described later, the ball end mill shown in FIG. 3 has a shape of a right-hand blade and right-hand twist.

The tool parameters and machining conditions that can be designed for ball end mills are shown below.
<Tool parameters>
・ Tool diameter ・ Tool protrusion ・ Number of flutes ・ Helix angle ・ Right edge/left edge <Processing conditions>
・Rotation speed ・Feed direction ・Feed amount per tooth ・Pick feed direction ・Pick feed amount ・Radial depth of cut ・Lead angle ・Tilt angle , and the tilt angle is the inclination angle of the tool in the direction perpendicular to the tool advancing direction.

As shown in FIG. 3, the helix angle of the ball end mill changes depending on the depression angle of the ball portion. The twist angle is close to 0 degrees near the bottom of the ball portion, gradually approaches a constant twist angle as it approaches the cylindrical portion, and has a constant twist angle at the cylindrical portion. Normally, the helix angle of a ball end mill means the helix angle of the cylindrical portion.

The end mill rotates in different directions depending on the orientation of the cutting edge. The helical edge of an end mill has a right edge and a left edge. When the end mill is viewed from the shank side to the tip side, a tool that cuts in the clockwise direction is called a "right edge". A tool that cuts in a counterclockwise direction is called a "left-hand edge". Ordinary end mills are right-handed tools, and there are few left-handed end mills.

In an end mill, the chip discharge direction differs depending on the twist direction of the cutting edge. A right-handed blade, right-helical end mill discharges chips upward, and a right-handed blade, left-handed end mill discharges chips downward. Hereinafter, regarding the right blade, the twist angle of the right twist is defined as positive, and the twist angle of the left twist is defined as negative. As for the left-hand blade, the left-handed, left-twisted end mill discharges chips upward, and the left-handed, right-twisted end mill discharges chips downward.

The ball end mill shown in FIG. 3 is a right-hand edge, right-hand helix tool and has a positive helix angle. As for right-handed blades, right-handed blade right-hand twist end mills are very common, but right-handed blade left-handed end mills with a rounded shape on the tip side, although the right-handed blade left-handed twist shape is slightly present in square end mills. does not exist. Similarly, there is no left-handed edge right-handed end mill having an R shape on the tip side.

The machining accuracy of the ball end mill will be considered below. First, before describing the processing method of the embodiment, a comparative technique for comparing with the processing method of the embodiment will be described.
In the comparative technique and the embodiment, the wall surface of the standing wall is finished by contour machining. Contour machining is to keep the height of the z-axis constant in one machining pass, feed in the xy direction to cut one line, and after cutting one line, pick feed in the z-axis direction to cut one line. It is a processing method that creates a finished surface by cutting and repeating this.

The comparative technique uses a common right-hand blade, right-hand helix ball nose end mill.
4(a) and 4(b) are diagrams for explaining an outline of a processing method as a comparative technique. In FIGS. 4A and 4B, the xyz coordinate system represents the tool coordinate system fixed to the ball end mill, and the uvw coordinate system represents the work piece coordinate system fixed to the work piece 62 . The xyz coordinate system, which is the tool coordinate system, may differ from the XYZ coordinate system in the machine tool device 10 . In the uvw coordinate system, the u-axis is the direction perpendicular to the wall surface of the vertical wall to be formed, the v-axis is the direction parallel to the feed direction, and the w-axis is the direction parallel to the pick feed direction. In the comparative technique, the feed direction of the ball end mill is the negative direction of the v-axis, and the pick-feed direction is the negative direction of the w-axis.

FIG. 4(a) shows how a ball end mill is fed to cut a work material in one machining pass. In the figure, the ball end mill indicated by a dotted line indicates the position of the previous cutting edge (one blade before), and the ball end mill indicated by a solid line indicates the position of the cutting edge of this time. The position of the current cutting edge is at a position advanced by the feed amount per blade from the position of the previous cutting edge in the feed direction.

FIG. 4(b) shows how the ball end mill cuts the work material in two overlapping machining passes. The surface of the work material 62 to be machined is rotated by a tilt angle _αT about the v-axis with respect to the z-axis. In the figure, the ball end mill indicated by the dotted line indicates the position of the cutting edge in the previous machining pass (one pass before), and the ball end mill indicated by the solid line indicates the position of the cutting edge in the current machining pass. The position of the cutting edge in the current machining pass is at a position advanced by the pick feed amount from the position of the cutting edge in the previous machining pass in the pick feed direction.

Ball end mill machining error is determined by the relative displacement of the tool and work material at the moment the cutting edge forms a finished surface. The term "finished surface" used herein refers to a surface formed by cutting a wall surface with a rotating cutting edge in the finishing process. In a ball end mill with a helix angle, the timing at which a finished surface is formed during cutting with a single blade differs depending on the height position of the cutting edge.

As in the comparative technology, when the pick feed direction is set downward (negative direction of the w-axis) and wall milling is performed with a ball nose end mill with a right-hand edge and right-hand twist, among the cutting edges involved in cutting, the bottom part is first Cutting begins with the cutting edge portions cutting into the work material, then the higher cutting edge portions continue to cut into the work material, and finally the uppermost cutting edge portion cuts into the work material. After that, when the cutting edge part near the bottom that cuts first comes out of the work material, the cutting edge part at a higher position comes out of the work material in the same order as the cutting order, and finally the top part The cutting edge part comes out of the work material, and cutting by one cutting edge is completed. Thus, according to the comparative technique, the finished surfaces are formed sequentially from bottom to top.

In ball end milling, most of the finished surface formed by the current cutting edge is removed by the next cutting edge in the same machining pass or the cutting edge in the next machining pass after one pick feed.

5A to 5C are diagrams for explaining the process of removing the finished surface.
FIG. 5(a) shows the finished surface A1 formed by the cutting edge this time. The N-th pass means the N-th machining pass in finishing machining.

FIG. 5(b) shows the finished surface B1 formed by the next cutting edge in the same machining pass. In FIG. 5B, the finished surface B1 is the hatched area. The finishing surface B1 is formed at a position shifted in the feed direction from the finishing surface A1 by the feed amount per blade. As shown, the finished surface B1 is formed over most of the finished surface A1. Therefore, most of the finished surface A1 is removed, leaving only a small portion of the finished surface A2.

FIG. 5(c) shows the finished surface C1 formed in the next machining pass. In FIG. 5(c), the finished surface C1 is the hatched area. The (N+1)-th pass, which is the machining pass for the finishing surface C1, is the (N+1)-th machining pass in the finish machining and means the pass subsequent to the N-th pass.

In the (N+1)th pass, cutting is performed by shifting the ball end mill downward by the pick feed amount from the Nth pass. As illustrated, the finished surface C1 is formed overlapping the finished surface A2. Therefore, most of the finished surface A2 is removed, leaving only a small portion of the finished surface A3. (Actually, most of the finished surface A2 is already removed in the machining before the finished surface C1 is formed in the (N+1)th pass.) The remaining finished surface A3 is then machined. hereinafter referred to as the "final finished surface".

As described above, in contour line machining, most of the finished surface formed by the current cutting edge is removed by the next cutting edge in the same machining pass or the cutting edge in the next machining pass after sending 1 pick feed amount, and a slight final Only the finished surface is left. A final product is a result of connecting the final finished surfaces, and if the final finished surface can be finished with high precision, a high-quality product can be created. In the wall machining of molds, etc., a low-rigidity structure (in this case, a long protruding end mill) is vibrated by the cutting force during machining, resulting in static displacement (static deflection) and dynamic displacement (forced vibration). Occur. If the displacement generated when forming the final finished surface is large, the machining accuracy will be poor, and if the displacement is small, the machining accuracy will be good.

In the comparative technology analysis, the tool parameters and machining conditions were set as follows.
<Tool parameters>
Tool diameter: 10mm
Tool protrusion: 50mm
Number of flutes: 1 Helix angle: +30 degrees (right helix)
Right Blade <Processing Conditions>
Feed direction: -v direction Feed amount per blade: 0.22 mm
Pick feed direction: -w direction Pick feed amount: 0.1mm
Radial depth of cut: 0.6mm
Lead angle: 0 degrees Tilt angle _αT : +7 degrees

Hereinafter, the timing (time) at which the ball end mill first contacts the work material is tin, the timing (time) at which the final finished surface is formed is tc, and the time difference (tc-tin) is Tp. As shown in FIG. 5(c), the final finish surface A3 has an area, and it takes a short time to form the final finish surface A3. In the embodiment, the timing tc is the time when the formation of the final finished surface is completed. The timing tc may be the time when the central portion of the final finished surface is formed.

FIG. 6 shows analysis results of cutting force and tool displacement during machining in a comparative technique. Looking at the variation of the cutting force, the cutting force begins to increase at timing t in , then decreases and becomes 0 at timing t out . At timing tin, the cutting edge involved in cutting starts cutting into the work material from the cutting edge part near the bottom, and after gradually cutting to the cutting edge part at the top, the cutting edge near the bottom It expresses that the cutting edge part gradually comes out of the work material, and the uppermost cutting edge part comes out of the work material at the timing tout.

Focusing on the displacement of the tool, it is confirmed that the displacement grows after the timing t in , and that the forced vibration in particular grows significantly. At timing tc, the displacement grows large. Therefore, a large machining error occurs in the final finished surface formed at the timing tc. The machining error is one of indices for evaluating machining accuracy, and is defined as the difference between the target position and the actual position of the final finished surface. From this, it can be seen that according to the comparative technique, the cutting edge forms the final finished surface after the displacement grows, so that the machining error is large.

FIG. 7 shows analysis results of machining errors in the comparative technique. In this analysis, the radial depth of cut was varied and other parameters and machining conditions were held constant. A positive machining error means uncut, and a negative machining error means over-cut. From the analysis results shown in FIG. 7, it is confirmed that the machining error greatly fluctuates when the radial depth of cut changes.

FIG. 8 shows analysis results of cutting force and tool displacement during machining in a comparative technique. Here, the cutting force and tool displacement are analyzed when the radial depth of cut is set to 0.3 mm, 0.5 mm, and 0.7 mm. In the figure, circle marks indicate the timing of tin, and square marks indicate the timing of tc. As shown in this analysis result, according to the comparative technique, Tp (=tc-tin) is large, so it is confirmed that the tool displacement grows at the timing tc for forming the final finished surface. Even if the machining conditions are set to Tp where the tool displacement is 0 using such a displacement profile, there are various reasons such as the position of the pre-machined surface being not accurately known at the actual machining site. , high-precision control according to the displacement profile is not easy.

Based on the above, a method for realizing high-precision machining according to the embodiment will be described. In the comparative technique, since the time Tp is long, the tool displacement is large at the timing tc for forming the final finished surface. The present inventor focused on the problem in this comparative technique and found the possibility of realizing high-precision machining by shortening the time Tp.

FIG. 9 shows the finishing procedure in the embodiment. In the processing apparatus 1, the control device 100 controls the spindle motor 40 and the feed mechanism according to a predetermined finish machining program to cause the machine tool device 10 to perform finish machining. The control device 100 and the machine tool device 10 are equipped with a computer including circuit blocks, memories, and other LSIs, and as described above, the machine tool device 10 and the control device 100 may be integrated. The control device 100 drives the spindle motor 40 to rotate the cutting tool 50 attached to the spindle 46 , and drives the feed mechanism to feed the cutting tool 50 relative to the workpiece 62 . Have.

The machine tool device 10 performs a first step (S1) in which the cutting tool 50 is rotated and sent relative to the work material 62 to cut the work material 62, and the cutting tool 50 is moved to the work material 62. and the second step (S2) of pick feeding (moving in the pick feeding direction) are alternately repeated. The first step (S1) and the second step (S2) are repeatedly executed until cutting by all machining paths is performed (N in S3), and when cutting by all machining paths is completed (Y in S3), Finishing is finished. In this finish machining, as shown in FIG. 5, the area other than the partial area of the finished surface formed by one cutting edge is removed by subsequent cutting.

In the first step, the processing device 1 is used to cut a portion of the area remaining as the final finished surface A3 from the timing when one cutting edge cuts into the work material 62 to the timing when the cutting edge exits the work material 62. Forming is completed by a timing closer to the timing of cutting than the timing of the cutting edge coming out. This reduces the time Tp. Formation of the partial area remaining as the final finished surface A3 is preferably started from the timing when the cutting edge cuts into the work material 62 . This makes it possible to greatly shorten the time Tp. Of the cutting edges involved in cutting in the first step, the processing device 1 moves the cutting edge located on the opposite side to the pick-feed direction to the work material 62 before the cutting edge located on the pick-feed direction side. A short time Tp is realized by cutting into .

<Example 1>
Example 1 proposes a shape of a ball end mill that shortens the time Tp in finishing.

10 shows the appearance of the ball end mill in Example 1. FIG. This ball end mill has a shape with a right edge and left helix. This ball end mill is specially designed and manufactured, and is not commercially available. Although the cutting edge is not formed on the bottom of the ball portion due to the restriction of the grinder that manufactures the ball end mill, this does not affect the wall surface finish processing targeted in the embodiment. At the bottom of the ball portion, a cutting edge with a different twist direction (for example, a straight edge or a right-hand twist) may be formed to realize a multifunctional tool.

11 shows analysis results of cutting force and tool displacement during machining in Example 1. FIG. The parameters and processing conditions used in the analysis are the same as those used in the analysis of the comparative technique described above. In Example 1, cutting force and tool displacement are analyzed when the radial depth of cut is set to 0.3 mm, 0.5 mm, and 0.7 mm. In the figure, circle marks indicate the timing of tin, and square marks indicate the timing of tc. In FIG. 11, the timings tout at which the cutting edge exits the work material are expressed in the same manner.

When the ball end mill with right edge and left twist of Example 1 is used for finishing, of the cutting edges involved in cutting, the cutting edge portion near the top starts cutting at timing tin, and immediately thereafter (at timing t). A cutting edge portion near the top allows a final finished surface to be formed. That is, the final finished surface A3 shown in FIG. 5(c) can be formed immediately after starting cutting with one cutting edge. Since the cutting force for forming the final finished surface is small, the static displacement is small and the dynamic displacement is also small. Therefore, the final finished surface can be formed before the tool displacement grows.

As shown in FIG. 11, according to Example 1, from the timing tin when one cutting edge cuts into the work material to the timing tout when the cutting edge exits the work material, the area that becomes the final finished surface is completed by the timing tc closer to the cutting timing tin than the timing tout at which the cutting edge comes out. By making Tp (=tc-tin) very short, it is confirmed that the tool displacement does not grow at the timing tc when the formation of the final finished surface is completed.

FIG. 12 shows the analysis results of machining errors in Example 1. FIG. In this analysis, the radial depth of cut was varied and other parameters and machining conditions were held constant. A positive machining error means uncut, and a negative machining error means over-cut. From the analysis results shown in FIG. 12, it is confirmed that even if the radial depth of cut changes, the machining error is small and the amount of change is also small. According to the finish machining according to Example 1, since the pick feed is performed in the downward direction of the wall surface, the cutting width projected in the radial direction of the end mill (the width in which the blade is in contact) is small and chatter vibration is less likely to occur, resulting in high accuracy. Wall processing can be realized. Although the above is based on the premise of down-cutting, even in up-cutting, the final finished surface is formed immediately after the start of cutting, so a ball end mill with a right-hand blade and left-hand twist can achieve high-precision wall processing.

In the first embodiment, a right-hand edge, left-twist ball end mill has been described, but a left-hand edge, right-twist ball end mill can also achieve high-precision wall machining. The absolute value of the twist angle is, for example, preferably 10 degrees or more, more preferably 30 degrees or more. In order to shorten the time Tp in finishing machining, besides the helix angle, setting values for machining conditions such as pick feed amount, radial depth of cut, and lead angle have an effect, but the absolute value of the helix angle is set large. By doing so, there is an advantage that the setting range of processing conditions can be widened.

<Example 2>
Example 2 proposes a lead angle that shortens the time Tp in finishing. The lead angle is a tool inclination angle in the advancing direction (feeding direction), and the lead angle at which the entire tool is tilted forward with respect to the tool feeding direction is a positive lead angle. Therefore, the lead angle at which the ball portion advances in the feed direction ahead of the cylindrical portion with respect to the tool feed direction is a negative lead angle. In Example 2, the ball end mill is set to have a negative lead angle _αL .

In Example 2, a ball end mill with no helix angle (a helix angle of 0 degrees) is used so that the influence of the lead angle can be easily understood.
FIG. 13 is a diagram for explaining the outline of the processing method according to the second embodiment. In Example 2, the feed direction of the ball end mill is the negative direction of the v-axis, and the pick-feed direction is the negative direction of the w-axis. Figure 13 shows how the ball end mill feeds and cuts in one machining pass. The position of the cutting edge of each is shown. The position of the current cutting edge is at a position advanced by the feed amount per blade from the position of the previous cutting edge in the feed direction.

When a ball end mill without helix angle is used and a negative lead angle is set, the topmost cutting edge among the cutting edges involved in cutting begins cutting, and immediately after that, the topmost cutting edge cuts the final surface. can be formed. That is, the final finished surface A3 shown in FIG. 5(c) can be formed immediately after starting cutting with one cutting edge. Since the cutting force for forming the final finished surface is small, the static displacement is small and the dynamic displacement is also small. Therefore, the final finished surface can be formed before the tool displacement grows.

14 shows analysis results of cutting force and tool displacement during machining in Example 2. FIG. Except for the tool torsion angle and lead angle, the parameters and machining conditions in the analysis are the same as those used in the analysis of the comparative technique described above, and the lead angle α _L is -30 degrees. In Example 2, cutting force and tool displacement are analyzed when the radial depth of cut is set to 0.3 mm, 0.5 mm, and 0.7 mm. In the figure, circle marks indicate the timing of tin, and square marks indicate the timing of tc.

As shown in FIG. 14, according to Example 2, from the timing tin when one cutting edge cuts into the work material to the timing tout when the cutting edge exits the work material, the area that becomes the final finished surface is completed by the timing tc closer to the cutting timing tin than the timing tout at which the cutting edge comes out. By making Tp (=tc-tin) very short, it is confirmed that the tool displacement does not grow at the timing tc when the formation of the final finished surface is completed.

FIG. 15 shows the analysis results of machining errors in Example 2. FIG. In this analysis, the radial depth of cut was varied and other parameters and machining conditions were held constant. A positive machining error means uncut, and a negative machining error means over-cut. From the analysis results shown in FIG. 15, it is confirmed that even if the radial depth of cut changes, the machining error is small and the amount of change is also small. According to the finish machining according to the second embodiment, since the pick feed is performed in the downward direction of the wall surface, the cutting width is small and chattering vibration is less likely to occur, so that highly accurate wall machining can be realized. Although the above is based on the premise of down-cutting, even with up-cutting, the final finished surface can be formed immediately after the start of cutting, so high-precision wall processing can be achieved.

The absolute value of the lead angle is, for example, preferably 10 degrees or more, more preferably 30 degrees or more. In order to shorten the time Tp in finishing machining, besides the lead angle, setting values for machining conditions such as the helix angle, pick feed amount, and radial depth of cut have an effect. By setting it, there is an advantage that the range of torsion angle and the setting range of other processing conditions can be widened. Moreover, by combining the technique shown in the first embodiment and the technique shown in the second embodiment, the time Tp can be shortened in a wider range of machining conditions, and highly accurate wall machining can be achieved.

<Example 3>
The third embodiment proposes a machining method in which the pick-feed direction is directed upward (positive direction of the w-axis) and the time Tp in the finish machining is shortened, unlike the comparative techniques and the first and second embodiments.

FIG. 16 is a diagram for explaining the outline of the processing method according to the third embodiment. In Example 3, the feed direction of the ball end mill is the negative direction of the v-axis, and the pick-feed direction is the positive direction of the w-axis. The ball end mill shown in FIG. 16 has a shape of a right-hand blade and right-hand helix.

FIG. 16 shows how the ball end mill cuts the work material in two overlapping machining passes. The workpiece 62 is rotated by a tilt angle _αT about the v-axis with respect to the z-axis. In the figure, the ball end mill indicated by the dotted line indicates the position of the cutting edge in the previous machining pass (one pass before), and the ball end mill indicated by the solid line indicates the position of the cutting edge in the current machining pass. The position of the cutting edge in the current machining pass is at a position advanced by the pick feed amount from the position of the cutting edge in the previous machining pass in the pick feed direction.

When the pick feed direction is +w direction, the lower cutting edge among the cutting edges involved in cutting starts cutting, and immediately after that, the lower cutting edge forms the final finished surface. As a result, the cutting edge begins to cut into the work material 62, and the final finished surface can be formed immediately. Since the cutting force for forming the final finished surface is small, the static displacement is small and the dynamic displacement is also small. Therefore, the final finished surface can be formed before the tool displacement grows.

By making the pick feed direction upward on the wall surface in this way, among the cutting edges involved in cutting in the first step, the cutting edge located on the opposite side to the pick feed direction is replaced with the cutting edge located on the pick feed direction side. It is possible to cut into the work material before the blade. As a result, the time Tp (=tc-tin) can be significantly shortened as compared with the comparative technique, and highly accurate finishing can be achieved. On the other hand, in the ball end mill shown in FIG. 16, the pick feed direction is set upward on the wall surface, so that the cutting width is increased. For this reason, in the third embodiment, it is preferable to suppress chatter vibration that may occur due to the upward direction of the pick feed on the wall surface.

FIG. 17 shows how the improved ball end mill used in Example 3 cuts the work material. The workpiece 62 is rotated by a tilt angle _αT about the v-axis with respect to the z-axis. In the figure, the ball end mill indicated by the dotted line indicates the position of the cutting edge in the previous machining pass (one pass before), and the ball end mill indicated by the solid line indicates the position of the cutting edge in the current machining pass. The position of the cutting edge in the current machining pass is at a position advanced by the pick feed amount from the position of the cutting edge in the previous machining pass in the pick feed direction.

The cutting tool 50, which is an improved ball end mill, has a hemispherical ball portion at the tip of the tool, a small diameter portion connected to the hemispherical ball portion, and a cylindrical portion connected to the small diameter portion. The small diameter portion has a circular cross section in a direction perpendicular to the tool axis direction, and the radius of the circular cross section is smaller than the radius r of the ball portion. The small-diameter portion of the cutting tool 50 shown in FIG. 17 has a shape in which the top side of a hemisphere with a radius r is removed along a plane perpendicular to the axis, and the cylindrical portion connects to the cutout surface of the top side.

なお小径部は、半径ｒの半球頂部側を、軸線に垂直な断面で除去した形状を有してよいが、半径ｒの底面をもつ円錐を、軸線に垂直な断面で除去した形状を有してもよい。Compared to the cutting process shown in FIG. 16, the improved cutting tool 50 does not cut at the cylindrical portion and has a significantly reduced cutting width, so chatter vibration is less likely to occur. Therefore, the stability against chatter vibration is high, and highly accurate finishing can be achieved. In order for the cylindrical portion not to cut, θc shown in the figure must satisfy the following inequality.

The small diameter portion may have a shape obtained by removing the hemispherical top side with radius r in a cross section perpendicular to the axis, but it has a shape obtained by removing a cone having a bottom surface with radius r in a cross section perpendicular to the axis. may

The present disclosure has been described above based on the embodiments and examples. Those skilled in the art will understand that the embodiments and examples are illustrative, and that various modifications can be made to combinations of each component and each treatment process, and such modifications are within the scope of the present disclosure. It is about

In the above-described multiple embodiments, the end mill having an R shape on the tip side is rotated and sent relative to the work material 62, and the work material 62 is cut by the cutting edge provided in the portion having the curvature. and the second step of pick-feeding (moving in the pick-feed direction) the end mill with respect to the workpiece 62 are repeated to form a finished surface. This processing method is based on the premise that a region other than a partial region of the finished surface formed by one cutting edge is removed by subsequent cutting.

In the modified example, we propose a machining method in which the side edge of an end mill is mainly used to transfer the shape of the cutting edge to a surface perpendicular to the feed direction to form a finished surface. Also in the processing method of this modification, the area other than the partial area of the finished surface formed by one cutting edge is removed by subsequent cutting, but by forming the finished surface using the side edge, All or most of the linear finished surface A2 in FIG. 5(b) is left as the final finished surface.

In the processing method of the modification, the side edge of the end mill is mainly used to form the finished surface, so the end mill does not need to have an R shape on the tip side. you can In a modified example, the end mill may have an R shape on the tip side, and may be a ball end mill, radius end mill, barrel end mill, or the like.

FIGS. 18A and 18B are diagrams for explaining an overview of the processing method according to the modification. FIGS. 18(a) and 18(b) show how the end mill is fed to form the finished surface. The xyz coordinate system represents the tool coordinate system fixed to the end mill, and the uvw coordinate system represents the work piece coordinate system fixed to the work piece 62 . In the uvw coordinate system, the u-axis is the direction perpendicular to the wall surface of the vertical wall to be formed, the v-axis is the direction parallel to the feed direction, and the w-axis is the direction parallel to the pick feed direction. The feeding direction of the end mill is the negative direction of the v-axis. For example, to form a draft angle, the surface of the workpiece 62 to be machined may be rotated about the v-axis by a tilt angle α _T with respect to the z-axis.

In the machining method of the modification, the control device 100 rotates the end mill and feeds it relative to the work material 62 to cut the work material 62 to form a finished surface. In a modified example, the control device 100 uses an end mill whose cutting edge has a helix angle of 0 degrees to perform up-cutting. The helix angle of the cutting edge is 0 degrees, and the finished surface is formed by up-cutting. Therefore, the final finished surface can be formed before the tool displacement grows.

A summary of aspects of the disclosure follows. An aspect of the present disclosure includes a first step of cutting the work material by rotating an end mill having an R shape on the tip side and feeding it relative to the work material, and picking the end mill with respect to the work material. This is a machining method for cutting the work material by repeating the second step of feeding. In this processing method, areas other than a partial area of the finished surface formed by one cutting edge are removed by subsequent cutting. In this machining method, from the timing when one cutting edge cuts into the work material to the timing when the cutting edge comes out of the work material, the formation of a part of the area is cut more than the timing when the cutting edge comes out. Complete by the timing close to the timing. As a result, highly accurate machining can be achieved.

In this machining method, the formation of the partial region may be started from the timing when the cutting edge cuts into the work material. In this machining method, among the cutting edges involved in cutting in the first step, the cutting edge located on the opposite side to the pick feed direction is applied to the work material earlier than the cutting edge located on the pick feed direction side. It is preferable to cut it. This machining method may use a right edge left helix end mill or a left edge right helix end mill. In the first step of this machining method, the end mill may be set with a negative lead angle. This processing method may use an end mill having a hemispherical ball portion, a small diameter portion connected to the ball portion, and a cylindrical portion connected to the small diameter portion.

A processing apparatus according to another aspect of the present disclosure is a processing apparatus that cuts a work material, and includes a rotation mechanism that rotates a main spindle having an end mill having an R shape on the tip side, and an end mill for the work material. a feed mechanism for relatively moving the end mill, a first step of controlling the operations of the rotation mechanism and the feed mechanism to feed the end mill relatively to the work material while rotating it, and cutting the work material; and a control device for repeating a second step of pick-feeding the to the work material. In the processing by this processing device, the area other than the partial area of the finished surface formed by one cutting edge is removed by subsequent cutting. The control device controls the formation of a part of the region between the timing when one cutting edge cuts into the work material and the timing when the cutting edge exits the work material, and the timing of cutting rather than the timing when the cutting edge exits. be completed by a timing close to As a result, highly accurate machining can be achieved.

Yet another aspect of the present disclosure is an end mill having a rounded shape on the tip side. This end mill repeats a first step of feeding the end mill relative to the work material while rotating to cut the work material, and a second step of pick-feeding the end mill with respect to the work material. It is used for finish machining of work materials, and has a right edge left twist shape or a left edge right twist shape. High precision machining can be achieved by using this end mill.

Yet another aspect of the present disclosure is a processing method in which an end mill is rotated and sent relative to a work material to cut the work material to form a finished surface. In this processing method, an end mill having a cutting edge with a helix angle of 0 degrees is used to perform up-cut processing. As a result, highly accurate machining can be achieved.

The present disclosure relates to a technique of forming a finished surface using an end mill having an R shape on the tip side.

DESCRIPTION OF SYMBOLS 1... Processing apparatus, 10... Machine tool apparatus, 50... Cutting tool, 62... Work material, 100... Control apparatus.

Claims (7)

A first step of cutting the work material with the cutting edge of the R-shaped portion by rotating an end mill having an R shape on the tip side and feeding it relative to the work material, and the end mill with respect to the work material. A machining method for cutting a work material by repeating the second step of pick-feeding, and a region other than a part of the finished surface formed by one cutting edge of the R-shaped portion is cut by subsequent cutting to be removed,
Among the cutting edges involved in cutting in the first step, the cutting edge located on the opposite side to the pick feed direction cuts into the work material before the cutting edge located on the pick feed direction side,
Between the timing when one cutting edge of the R-shaped portion cuts into the work material and the timing when the cutting edge comes out of the work material, the formation of the partial region is cut more than the timing when the cutting edge comes out. Complete by the timing close to the timing,
A processing method characterized by: The formation of the partial region is started from the timing when the cutting edge cuts into the work material,
The processing method according to claim 1, characterized by: Use a right edge left helix end mill or a left edge right helix end mill,
3. The processing method according to claim 1 or 2 , characterized in that: In a first step, setting a negative lead angle on the end mill;
4. The processing method according to any one of claims 1 to 3 , characterized in that: Using an end mill having a hemispherical ball portion, a small diameter portion connected to the ball portion, and a cylindrical portion connected to the small diameter portion,
The processing method according to claim 1 , characterized by: A processing device for cutting a work material,
a rotating mechanism that rotates a spindle to which an end mill having an R shape is attached on the tip side;
a feed mechanism for moving the end mill relative to the work material;
a first step of controlling the operations of the rotation mechanism and the feed mechanism to feed the end mill relative to the work material while rotating it, and cutting the work material with the cutting edge of the R-shaped portion; with a control device that repeats the second step of pick-feeding the work material, and the area other than the partial area of the finished surface formed by one cutting edge of the R-shaped portion is formed by subsequent cutting to be removed,
The control device is
Among the cutting edges involved in cutting in the first step, the cutting edge located on the opposite side to the pick feed direction cuts into the work material before the cutting edge located on the pick feed direction side,
Between the timing when one cutting edge of the R-shaped portion cuts into the work material and the timing when the cutting edge comes out of the work material, the formation of the partial region is cut more than the timing when the cutting edge comes out. Complete by the timing close to the timing,
A processing device characterized by: to the computer,
A first function of cutting the work material with the cutting edge of the R-shaped portion by rotating the end mill having an R shape on the tip side and feeding it relative to the work material;
A program for repeatedly realizing a second function of pick-feeding an end mill to a work material, in which the area other than the partial area of the finished surface formed by one cutting edge of the R-shaped portion is is removed by subsequent cutting,
The first function is
Among the cutting edges involved in cutting, the cutting edge located on the opposite side to the pick feed direction cuts into the work material before the cutting edge located on the pick feed direction side,
Between the timing when one cutting edge of the R-shaped portion cuts into the work material and the timing when the cutting edge comes out of the work material, the formation of the partial region is cut more than the timing when the cutting edge comes out. Including the function to complete by the timing close to the timing,
A program characterized by

Images