WO2006011353A1 - Thread groove processing method - Google Patents

Abstract

A thread groove (20) is processed by a ball end mill (15), a rotating tool. For example, a thread groove is rough-processed on the periphery of work (10) by a cutting tool, then the groove is hardened, and finally the groove is finished by the ball end mill (15). The ball end mill (15) has a cutting edge diameter smaller than the width of the thread groove, and the groove is finished by varying in a stepped manner the cutting position of the ball end mill (15). By this, a thread groove of a lead screw device with a large diameter and a thread groove with a complex shape can be processed at high accuracy, not to mention general thread grooves. Further, grinding by a grinding stone can be eliminated.

Description

 Thread groove processing method

 Technical field

 [0001] The present invention relates to a thread groove machining method for a screw shaft or a nut of a feed screw device.

 Background art

 [0002] The feed screw device has two members (screw shaft and nut) provided with screw grooves, and a plurality of rolling elements inserted into a rolling path constituted by the screw grooves of both members, Smooth rolling movement between the screw shaft and nut is achieved by rolling or sliding of the rolling elements.

 [0003] The thread groove of the screw shaft and nut is usually processed by roughing the thread groove using a total tool, quenching the surface, and finally grinding with a total turret. It will be calocheed. In the case of a small-diameter feed screw device, the thread groove may be directly machined with a full-sized turret for a hardened workpiece.

 [0004] Also, Patent Document 1 proposes a machining method using a small general-purpose tool instead of a total tool. In this method, the accuracy of the thread groove force is improved by repeating cutting by sequentially shifting the general-purpose tool in the arc direction of the cross-sectional shape of the thread groove.

 Patent Document 1: JP-A-6-249317

 Disclosure of the invention

 Problems to be solved by the invention

[0005] However, the conventional processing method has the following problems.

(1) The larger the diameter of the feed screw device, the more difficult it is to grind the thread groove.

In grinding with a total type mortar, the shape of the mortar is directly transferred to the thread groove. Therefore, the shape distortion and wear of the grindstone greatly affects the thread groove processing accuracy. Problems such as the distortion of the shape of the grinding wheel become more prominent as the feed screw device becomes larger in diameter, that is, as the size of the turret becomes larger, which causes a reduction in the accuracy of thread groove machining. Recently, a large-diameter feed screw device with a screw shaft diameter of φ250-350mm and a thread groove width (ball diameter) of about 25mm has been introduced. It is hard to say that it is realistic. Also, the increase in the size of the grindstone causes the so-called “chatter” and increases the size of the grinding equipment. There is also a harmful effect of inviting.

 [0007] In addition, Patent Document 1 describes that grinding with a mortar can be omitted. However, with a general-purpose byte, the cutting speed cannot be increased so much, and wear due to cutting resistance is severe. Actually, it is difficult to achieve the surface roughness required for a lead screw device with only a general-purpose tool.

 (2) It is difficult to process a thread groove having a complicated shape.

 In other words, since the cutting tool has only one cutting edge, the cutting tool can only be fed in one direction during cutting. This is the same for both general-purpose bytes and general-purpose bytes. Therefore, the cutting with Neut cannot make a simple spiral shape and force check. For example, a complicated shape in which a bent portion is provided in the middle of a screw groove is difficult to process. In addition, grinding with a general-purpose turret cannot cope with such complex shapes.

 [0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to process a screw groove of a large-diameter feed screw device or a screw groove of a complicated shape with high accuracy. An object of the present invention is to provide a thread groove processing method capable of

 [0010] Another object of the present invention is to provide a thread groove machining method capable of machining a thread groove without grinding with a mortar with high accuracy.

 Means for solving the problem

 In order to achieve the above object, in the present invention, the thread groove of the feed screw device is covered by a rotary tool that rotates about an axis that is substantially perpendicular to the axis of the workpiece on which the thread groove is processed. Here, the “feed screw device” includes both a ball screw and a roller screw, and the “thread groove” includes both the thread groove of the screw shaft and the thread groove of the nut.

 [0012] This type of rotary tool has a cutting speed much higher than that of a cutting tool, and wear is small, so that a highly accurate force can be obtained. In addition, it is possible to achieve a sufficient surface roughness even before finishing with a turret. This type of rotary tool, unlike conventional tools and full-size turrets, can control the cutting position flexibly regardless of how the cutting edge is applied. Can be processed freely, and complex shapes can be easily processed.

[0013] The rotary tool is preferably a milling tool such as an end mill or a face mill. Of these, a ball end mill is particularly preferable. Alternatively, it is also preferable to use a grinding tool as the rotating tool. The rotary tool in the present invention processes a thread groove by relatively sending the rotary tool and the workpiece, and does not include a drilling tool that cannot perform force cutting in the direction of the rotation axis. Further, the rotary tool in the present invention does not include a conventional general-purpose grindstone that rotates around an axis substantially parallel to the axis of the workpiece.

 [0014] It is preferable that the rotary tool is a tool made of a super-hard material. In particular, CBN (Cubic Boron

 Nitride) Tool is preferred!

 [0015] This makes it possible to perform cutting by ultra-high speed rotation such as tens of thousands of rpm, shortening the machining time and improving the machining accuracy, and enabling dry force. In addition, CBN tools have the advantage that they can be cut after quenching.

 [0016] As one aspect of the thread groove cabling method, a first cutting process of roughing the thread groove on the peripheral surface of the workpiece with a cutting tool, a quenching process of quenching the roughly processed thread groove, A second cutting step of finishing the hardened thread groove with a rotary tool (such as a ball end mill) can be considered. That is, instead of the conventional grinding process using a grindstone, a second cutting process using a rotary tool is provided.

 [0017] In the second cutting step, it is preferable to use a rotary tool having a cutting edge diameter smaller than the thread groove width, and to finish the thread groove by gradually changing the cutting position by the rotary tool.

 [0018] According to this method, the thread groove of the feed screw device having a large diameter can be machined with a small rotary tool, and problems such as an increase in the size of the machining device and an increase in cost do not occur. Further, according to the above method, the same rotary tool can be used to machine a thread groove of a small diameter to medium diameter feed screw device as well as a large diameter feed screw device, and the versatility of the machining device is improved.

 [0019] In the second cutting step, at one end of the thread groove, an offset amount in the groove width direction with respect to the center of the thread groove and a cut amount corresponding to the offset amount are set in the rotary tool, and the workpiece is rotated while rotating the workpiece. And the rotary tool are moved relative to each other by the feed amount corresponding to the lead of the thread groove, and the cutting is performed in a spiral manner to the other end of the thread groove with a constant offset amount and a cutting amount. It is preferable to perform the finishing force of the thread groove by changing the set value of the cut amount stepwise and repeating the helical cutting.

[0020] By using a powerful method, control of the processing apparatus can be simplified and cutting can be performed efficiently. You can. In addition, there is an advantage that the machining accuracy is stabilized because the cutting is performed from one end of the thread groove to the other end with a constant cutting amount in one spiral cutting.

 [0021] The first end force of the thread groove After performing the spiral cutting in the forward path to the second end, the rotation direction of the workpiece and the feed direction of the workpiece and the rotary tool are reversed, and the second end force It is more preferable to perform the helical cutting even in the return path to the first end of the end force.

 [0022] If spiral cutting is performed in each of the forward path and the return path, the machining efficiency can be improved and the machining time can be shortened.

 [0023] It is preferable to cut a symmetrical position with respect to the center of the thread groove in the forward path and the backward path by inverting the offset amount while maintaining the cutting amount of the rotary tool at the second end.

 [0024] Thereby, the cut amount at the symmetrical position of both walls of the thread groove becomes the same, and the shape accuracy of the thread groove is improved. In addition, since the air cut can be minimized, the man-hour reduction effect can be obtained.

 [0025] A workpiece is mounted on a processing apparatus including a head for supporting the cutting tool, a head for quenching, and a head for supporting the ball end mill, and the first cutting step, the quenching step, And it is preferable to perform the said 2nd cutting process continuously.

 [0026] Thereby, the setup time between processes can be shortened or zero, and the machining time can be shortened.

 [0027] Other aspects of the thread groove processing include a quenching process in which the peripheral surface of the workpiece is quenched, and the peripheral surface of the workpiece that has been quenched using a rotating tool is shallower than the quenching depth. A method including a cutting step of adding grooves is conceivable. In other words, only one cutting with a rotating tool is performed until the final Karoe.

 [0028] By the powerful method, the thread groove cover can be accurately performed with few steps. This method is effective for the thread groove force of a small-diameter feed screw device.

 [0029] When the thread groove itself is small, it is preferable to use an overall rotary tool corresponding to the thread groove shape in the cutting step. As a result, the machining time can be shortened, and the machining accuracy and the surface roughness can be improved.

[0030] The screw groove is formed on an inner peripheral surface of a nut assembled to a screw shaft provided with a spiral screw groove, and the cutting step is performed together with the screw groove of the screw shaft. Forming the rolling groove constituting the rolling path into a length of less than one round of the inner circumference of the nut; And a step of forming a circulation groove for circulating the rolling elements in the rolling path from one end to the other end of the rolling groove.

 The invention's effect

 [0031] According to the present invention, not only general thread grooves but also thread grooves of large-diameter feed screw devices and complex-shaped thread grooves can be processed with high accuracy. In addition, grinding with a turret can be omitted.

 BEST MODE FOR CARRYING OUT THE INVENTION

[0032] Preferred embodiments of the present invention are illustratively described in detail below with reference to the drawings.

[0033] <First embodiment>

 The first embodiment is an example in which the thread groove machining method according to the present invention is applied to a thread groove calorie of a large-diameter ball screw.

 [0034] (Configuration of Ball Screw)

 FIG. 1 is a perspective view showing a schematic configuration of a ball screw. As shown in the figure, the ball screw has a screw shaft 1 and a nut 2 assembled so as to be relatively movable. The outer circumferential surface of the screw shaft 1 and the inner circumferential surface of the nut 2 are formed with spiral thread grooves 3 and 4 with the same lead, and both thread grooves 3 and 4 are combined inside the nut 2 to form a tunnel-like shape. Construct a rolling path. A plurality of rolling elements 5 are inserted in this rolling path. In this example, balls are used as the rolling elements 5 and the spacers 6 are interposed between the respective balls. In addition, a return pipe method is adopted as a circulation method of the rolling elements 5.

 In the ball screw configured as described above, when the screw shaft 1 (or nut 2) is rotated around the axis, the nut 2 (or screw shaft 1) moves linearly in the axial direction. At this time, since the rolling element 5 performs a rolling motion in the rolling path, a smooth feeding motion is realized. Conversely, it is also possible to give a linear motion to the nut 2 or the screw shaft 1 and convert it into a rotational motion.

[0036] With a general ball screw that has been commercialized, the screw shaft diameter is a few mn! The ball diameter (thread groove width) is about φ10mm at most. On the other hand, in this embodiment, assuming a very large ball screw having a screw shaft diameter of φ100 mm or more (for example, about φ250 to 350 mm) and a ball diameter of about φ10 to 25 mm! /, The [0037] With such a large diameter, problems such as distorted turret shape, chatter chatter, and increased processing equipment cannot be ignored, and the thread groove should be machined in the same way as a general ball screw. Is difficult. Therefore, in this embodiment, the thread groove is processed by the method described below. Here, the thread groove of the force nut, which will be described by taking the thread groove force of the screw shaft as an example, can be covered by the same method.

 [0038] (Thread groove processing method)

 Fig. 2 and Fig. 3 show the configuration of the processing equipment for thread groove cover. Fig. 2 is a diagram of the machining device as viewed in the axial direction of the screw shaft, and Fig. 3 is a diagram schematically showing the head configuration of the machining device.

[0039] The processing apparatus generally includes a work support unit 11 that supports a work (object to be processed) 10, and a processing unit 13 that is provided with a head 12 that supports a tool or the like. The machining apparatus includes three machining units 13 that can be controlled independently. Each of the carriage units 13 includes a first cutting head 12a that supports a roughing nose 14 and induction hardening. A quenching head 12b is used, and a second cutting head 12c is mounted to support a ball end mill 15 for finishing. Each head 12a-12c is controlled by CNC.

 [0040] At the time of processing, the workpiece 10 made of raw material is mounted on the chuck 16 of the workpiece support unit 11, and the workpiece 10 is rotated around the axis while keeping the workpiece 10 horizontal. Then, a paste process (first cutting process) in which the screw groove is ft¾sed to the peripheral surface of the workpiece 10 by the knot 14, a quenching process in which the screw groove is quenched by the quenching head 12b, and a screw A finishing process (second cutting process) in which the grooves are finished by the ball end mill 15 as a rotating tool is sequentially performed. As a result, since one-chuck can be performed continuously from quenching to finishing, the setup time between processes can be shortened to zero or the machining time can be shortened.

 [0041] Next, details of each step will be described.

 [0042] (Simplified process)

Fig. 4 shows how roughing is performed with the tool 14. In this embodiment, a cutting tool 14 smaller than the thread groove width W is used. Then, by repeating the turning while appropriately switching the offset amount and the cutting amount of the cutting tool 14, the cross-section arc-shaped (Gothic-arch shape) screw groove 20 is formed on the outer peripheral surface of the workpiece 10. [0043] Here, it is also preferable to use a force-type tool or a ball end mill that uses a small tool 14 as a cutting tool to check the thread groove.

 [0044] (Quenching process)

 When the thread groove 20 is finished, high-frequency quenching is performed on the surface of the workpiece 10 using the quenching head 12b. In the present embodiment, as indicated by the alternate long and short dash line in FIG. 5, only the surface of the thread groove 20 is shallowly quenched (approximately several mm). The surface of the thread groove 20 may be hardened using means other than high frequency (for example, laser).

 [0045] (Finishing process)

 Subsequently, the thread groove 20 is finished by the ball end mill 15. Here, using a ball end mill 15 containing super hard material CBN for the cutting edge, dry machining is performed by high-speed rotary cutting. Also, as shown in Fig. 6, select a cutting edge diameter smaller than the thread groove width W (for example, φ4-5mm), and set the cutting position (offset amount and cutting amount) by the ball end mill 15. Finish the thread groove 20 by changing it step by step. The offset amount refers to the displacement in the groove width direction with respect to the center of the screw groove 20 (indicated by Ol, 02,... In FIG. 6), and the cutting depth refers to the radial displacement (in FIG. 6). CI, C2, ···).

 [0046] Specifically, the following cutting control is performed. First, the ball end mill 15 is set to the initial position and rotated at a high speed of tens of thousands of rpm. The initial position is a position that is further on the axially outer side by an offset amount “01” from the groove center at one end (first end) of the spiral thread groove 20. Then, the cutting amount “C1” corresponding to the offset amount “01” is set, and the cutting edge of the ballend mill 15 is caused to enter the thread groove surface. In this embodiment, the amount of cut is controlled so that the amount of intrusion into the thread groove surface is about 50 to 60 microns. The ball end mill 15 rotates around an axis parallel to the approach direction, that is, an axis substantially orthogonal to the workpiece axis.

Next, as shown in FIG. 7, the workpiece 10 is rotated forward at a constant speed in the direction of the arrow RA, and at the same time, the ball end mill 15 is moved to the left in the drawing with a feed amount corresponding to the lead of the thread groove 20. Move to. As a result, the ball end mill 15 is fed along the edge of one side of the thread groove 20 (see arrow A), and the other of the thread grooves 20 is maintained while maintaining the constant offset amount “01” and the cut amount “C1”. Cutting is performed spirally to the end (second end) (this process is hereinafter referred to as spiral cutting).

When the ball end mill 15 reaches the second end, the offset amount is gradually decreased while the cut amount “C1” is maintained, and the rotation of the workpiece 10 is also decelerated. At this time, the locus of the ball end mill 15 draws a curve as indicated by an arrow. Then, at the timing when the offset amount of the ball end mill 15 turns to a negative value, reverse rotation of the workpiece 10 (in the direction of the arrow RB) is started, and the ball end mill 15 is controlled so as to draw a curve indicated by the arrow. With this control, the end of the thread groove 20 is processed into an arc shape. Fig. 8 shows a cross section along the line DD in Fig. 7.

 [0049] When the value of the offset amount becomes "01", the ball end mill 15 is moved to the right in the figure by the feed amount corresponding to the lead of the thread groove 20 while rotating the workpiece 10 at a constant speed. Therefore, on the return path, the ball end mill 15 is sent along the edge opposite to the outward path (see arrow B), and the first offset of the thread groove 20 is determined by the constant offset amount “1” and the cut amount “C1”. Spiral cutting is performed to the end of 1.

 [0050] When the ball end mill 15 reaches the first end, as in the case of the second end, the groove end is processed into an arc shape. By the above series of controls, cutting is performed on the portion of the screw groove 20 having the same depth.

 [0051] After that, if the offset amount of the ball end mill 15 is set to "02" and the cut amount is set to "C2" and the same control as described above is performed, the portion slightly inside the thread groove 20 can be cut. In this way, the finish machining of the thread groove is completed by sequentially repeating the cutting control up to the center portion of the thread groove 20 while gradually switching the offset amount and the cutting amount.

 [0052] The thread groove machining method of the present embodiment described above has the following advantages.

 [0053] The ball end mill 15 has a cutting speed much higher than that of Neute and has little wear, so that it can be processed with high accuracy. In addition, sufficient surface roughness can be achieved, eliminating the need for grinding with a grindstone. In machining with the ball end mill 15, the machined surface roughness is determined by the cutting edge diameter and pick feed. In other words, by appropriately selecting the cutting edge diameter of the ball end mill 15 and the offset amount described above, it is possible to easily achieve the surface roughness required for the ball screw.

[0054] In addition, unlike the bite and the turret, the ball end mill 15 is not limited to the method of applying the cutting edge. The cutting position can be controlled flexibly. Therefore, the degree of freedom of processing is increased, and reciprocal cutting and groove end processing as described above can be easily performed. As a result, a small ball-end mill 15 can be used to process any ball screw having a small diameter to a large diameter, and the versatility of the processing apparatus is increased. In the conventional method, as the screw shaft diameter and the thread groove width increase, the rigidity of the processing device is required. Therefore, the force that has led to an increase in the size and cost of the processing device. Does not occur.

 [0055] In addition, since the ball end mill 15 of CBN is used in the present embodiment, it is possible to perform cutting by high speed rotation of tens of thousands of rpm, and it is possible to shorten the processing time and improve the processing accuracy. It is dry and does not require cutting oil, which is preferable from the viewpoint of environmental issues.

 [0056] Further, by adopting the above-described spiral cutting, it is possible to simplify the control of the processing apparatus and to perform cutting efficiently. Furthermore, since the cutting is performed from one end to the other end of the thread groove 20 with a constant cut amount, the machining accuracy is stabilized. Since the cutting force is also spirally cut in each of the forward path and the return path, the machining efficiency can be improved and the machining time can be shortened.

 [0057] In addition, the offset amount is reversed while maintaining the cut amount at the end of the thread groove 20, and the positions symmetrical to the thread groove center are cut in the forward path and the backward path. The cut amount at the symmetric position is the same, and the shape accuracy of the thread groove 20 is improved (that is, the thread groove shape is symmetrical). In addition, since reciprocal cutting is performed with a constant cutting depth, air cuts can be minimized and man-hours can be reduced.

 [0058] Further, the end of the thread groove is machined into an arc shape, and the force is rounded up as shown in FIG. 8, thereby reducing the burden on the ball end mill 15.

 In the present embodiment, the thread groove of the force nut 2 shown in the case where the thread groove of the screw shaft 1 is formed can also be formed by the same processing method.

 [0060] <Second Embodiment>

 The second embodiment is an example in which the thread groove machining method according to the present invention is applied to thread groove machining with a complicated shape.

 [0061] (Nut configuration)

FIG. 9 is a perspective view showing a thread groove of the nut. The nut 30 also has a single ring force, and an endless thread groove (hereinafter referred to as “one-turn groove”) 31 is formed on the inner peripheral surface thereof. one The winding groove 31 is composed of two partial forces: a rolling groove 32 that forms a rolling path of the ball (rolling element) together with the thread groove of the screw shaft, and a circulation groove 33 that circulates the ball in the rolling path. The The rolling groove 32 is the same lead as the screw groove of the screw shaft and has a length of less than one round of the inner circumference of the nut. On the other hand, the circulation groove 33 has a lead in the opposite direction to the rolling groove 32, and connects one end of the rolling groove 32 with the other end. The portion of the circulation groove 33 has a groove depth larger than the ball diameter.

 FIG. 10 shows a state where the nut 30 is assembled to the screw shaft. The rolling groove 32 portion of the winding groove 31 is the force that forms the rolling path of the ball facing the screw groove 41 of the screw shaft 40.The circulation groove 33 portion straddles the thread 42 of the screw shaft 40. It becomes like this.

 [0063] The circulation groove 33 is a portion corresponding to the return nove in the nut of the first embodiment. That is, when the nut 30 and the screw shaft 40 rotate relatively, the ball rolls while receiving a load in the rolling path between the rolling groove 32 of the nut 30 and the screw groove 41 of the screw shaft 40. Then, the ball that has reached the end of the rolling groove 32 passes through the circulation groove 33 in an unloaded state, gets over the thread 42, and is returned to the other end of the rolling groove 32.

 [0064] According to such a one-turn groove 31, it is possible to circulate the ball with a simple configuration without adding a circulation member such as a return pipe, a deflector, or an end cap.

 [0065] However, since the single-turn groove 31 has a complicated shape having a bent portion in the middle rather than a simple spiral shape, cutting with a cutting tool or grinding with a grindstone is difficult. Therefore, in this embodiment, the thread groove is processed by the method described below.

 [0066] (Thread groove machining method)

 FIG. 11 to FIG. 15 show the configuration of a processing apparatus for thread groove cover. 11 is a perspective view of the processing apparatus, FIG. 12 is a plan view, FIG. 13 is a front view, and FIG. 14 is a side view. FIG. 15 is a cross-sectional view showing a head configuration of a ball mill.

 [0067] The machining apparatus generally includes a workpiece support unit 51 that supports a workpiece, and a cage unit 52 that is provided with a head 53 that supports a tool. The work support unit 51 includes a chuck 54 that holds a work. The machining unit 52 is movable in the two axis directions of Υ and Z and is controlled by CNC.

As shown in FIG. 15, the tip of the head 53 is connected to a ball end mill 55, a dynamic pressure bearing 56 that rotatably supports the ball end mill 55, and a base end of the ball end mill 55. A turbine 57 is provided. By spraying the high-pressure fluid onto the turbine 57, the ball end mill 55 can be rotated at a high speed (for example, tens of thousands of rpm). The ball end mill 55 may be driven by a motor or belt in addition to the dynamic pressure spindle!

 [0069] As the ball end mill 55, a CBN tool containing super hard material CBN is used for the cutting edge, and the cutting edge diameter is selected to be the same as the groove width of the one-turn groove 31. That is, in the present embodiment, the total type ball end mill 55 corresponding to the thread groove shape is used. Use of CBN tools facilitates surface cutting after quenching.

 Therefore, in the present embodiment, prior to the processing of the thread groove, a predetermined depth of quenching is performed on the inner peripheral surface of the cylindrical cake that also has raw material strength (quenching process). In this state, the inner peripheral surface of the work remains a cylindrical surface, and a thread groove is formed.

 [0071] Next, after the quenched workpiece is mounted on the chuck 54 of the workpiece support unit 51, the ball end mill 55 is set to the initial position and rotated at a high speed of several tens of thousands of rpm. Here, the initial position (in the Z-axis direction) is a position corresponding to the starting end of the rolling groove 32. Then, the cutting depth (Y-axis direction) is set in accordance with the groove depth of the rolling groove 32, and the cutting edge of the ball end mill 55 is caused to enter the inner peripheral surface of the workpiece. The amount of penetration (groove depth) at this time is shallower than the quenching depth. Also in this embodiment, dry processing is performed.

 Subsequently, while rotating the workpiece at a predetermined speed, the ball end mill 55 is fed in the Z-axis direction with a feed amount corresponding to the lead of the rolling groove 32 to process the rolling groove 32. When the workpiece rotates by a predetermined angle (less than one turn) and the ball end mill 55 reaches the end of the rolling groove 32, the feed direction is reversed and the depth of cut is increased. Then, the circulation groove 33 is processed from the end to the start of the rolling groove 32. Thus, the processing of the one-turn groove 31 is completed.

 [0073] According to the above method, by using the CBN ball end mill 55, it becomes possible to perform thread groove machining after quenching, and the Lo process as in the first embodiment can be omitted. Shikaso can also be machined with high precision and can achieve a sufficient surface roughness, eliminating the need for grinding with a turret. Therefore, the thread groove can be machined with high accuracy by only two processes, the quenching process and the cutting process.

[0074] Further, according to the ball end mill 55, a thread groove having a complicated shape such as a one-turn groove 31 in which a bent portion exists in the middle can be processed easily and with high accuracy. Reality In the embodiment, since the entire ball end mill 55 is used, the entire thread groove can be machined with a single feed, and the machining time can be shortened. In addition, the accuracy of the car and the roughness of the carved surface will be improved.

 [0075] While the present invention has been described in detail with reference to the first and second embodiments, these are merely examples of the present invention. The scope of the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the technical idea.

 [0076] For example, in the above embodiment, the force exemplified for the machining of a special screw groove such as a screw groove or a single turn groove of a large-diameter ball screw. The screw groove machining method according to the present invention is a general feed screw. The present invention can also be preferably applied to thread groove machining of devices (ball screws, roller screws, etc.).

 [0077] Further, the control method of the ball end mill is not limited to that of the above embodiment, and can be modified as appropriate. For example, in the first embodiment, the tool is applied from the edge of the screw groove and sequentially moved to the center of the screw groove. On the contrary, the tool is applied from the center of the screw groove and sequentially moved to the edge. Alternatively, the cutting may be performed from one edge of the thread groove to the other edge in order. Further, cutting may be performed only in the outward path, and the end shape of the screw shaft may not be processed into an arc shape.

 [0078] In the second embodiment, when there is a weight of a force nut that holds the workpiece horizontally, the workpiece is placed on the table and the tool is fed from above.

 Further, in the above embodiment, the same thread groove force can be obtained even if a rotating tool such as a force using a CBN ball end mill is used. For example, it is possible to use a milling tool (end mill or face mill) used for milling caroe, or to use a small rotary grinding tool. When machining a thread groove having a Gothic cross section as in the above embodiment, a ball end mill having a round tool tip is suitable as a grinding tool. When the thread groove has a straight cross-sectional shape such as a square groove or V groove, a rotary tool such as a straight end mill or face mill is suitable. The type of rotary tool to be selected should be determined according to the cross-sectional shape of the thread groove and the control method (feed method) of the rotary tool.

 Brief Description of Drawings

FIG. 1 is a perspective view showing a schematic configuration of a ball screw according to a first embodiment. FIG. 2 is a diagram showing a configuration of a processing apparatus according to the first embodiment.

 FIG. 3 is a diagram schematically showing a head configuration of the processing apparatus of FIG. 2.

 [Fig. 4] A diagram showing Loe's state of Neut.

 FIG. 5 is a diagram showing a screw groove that has been quenched.

 [Fig. 6] A diagram showing the state of finishing force by a ball end mill.

 FIG. 7 is a diagram for explaining cutting control of a ball end mill.

 FIG. 8 is a sectional view taken along the line D-D in FIG.

 FIG. 9 is a view showing a thread groove of a nut according to a second embodiment.

 FIG. 10 is a view showing a state where the nut of FIG. 9 is assembled to the screw shaft.

 FIG. 11 is a perspective view showing a configuration of a processing apparatus according to a second embodiment.

 FIG. 12 is a plan view of the processing apparatus of FIG.

 FIG. 13 is a front view of the processing apparatus of FIG.

 FIG. 14 is a side view of the processing apparatus of FIG.

 FIG. 15 is a cross-sectional view showing a head configuration of a ball end mill.

Explanation of symbols

 1 Screw shaft

 2 Nut

 3, 4 thread groove

 5 Rolling elements

 6 Spacer

 10 work

 11 Work support unit

 12 heads,

 12a 1st cutting head

 12b quenching head

 12c 2nd cutting head

13 Karoe Unit Bonore End Minore Chuck Thread Groove

Nut

Single winding groove (screw groove) Rolling groove

Circulation groove

Screw shaft

Thread groove

Thread

Work support unit Processing unit Head,

Chuck Bonore End Minore Dynamic Pressure Bearing Turbine

Claims

The scope of the claims  [1] A thread groove machining method, characterized in that a thread groove of a feed screw device is machined by a rotary tool that rotates about an axis substantially orthogonal to an axis of a workpiece on which the thread groove is machined.  2. The thread groove caloe method according to claim 1, wherein the rotary tool is a ball end mill.  [3] The thread groove machining method according to claim 1 or 2, wherein the rotary tool is a CBN tool.  [4] a first cutting process in which a thread groove is roughly machined on a peripheral surface of a workpiece by a cutting tool;  A quenching process for quenching the threaded grooves;  4. The thread groove machining method according to claim 1, further comprising a second cutting step of finishing the quenched thread groove with the rotary tool. 5. [5] The second cutting process is characterized in that a rotary tool having a cutting edge diameter smaller than the thread groove width is used, and the cutting position by the rotary tool is changed stepwise to finish the thread groove. The thread groove processing method according to claim 4. [6] In the second cutting process,  At one end of the thread groove, an offset amount in the groove width direction with respect to the center of the thread groove and a cutting amount according to the offset amount are set in the rotary tool,  While rotating the workpiece, the workpiece and the rotary tool are moved relative to each other by the feed amount corresponding to the lead of the screw groove, and a spiral is cut to the other end of the screw groove with a certain offset amount and cut amount. Including steps,  6. The thread groove force method according to claim 5, wherein the thread groove finishing force is measured by changing the set values of the offset amount and the cut amount stepwise and repeating the helical cutting.  [7] The first end force of the thread groove After performing the spiral cutting in the forward path to the second end, the rotation direction of the workpiece and the feed direction of the workpiece and the rotary tool are reversed to The thread groove machining method according to claim 6, wherein the spiral cutting is performed also in a return path to the first end. [8] The offset amount is counteracted while maintaining the cutting amount of the rotary tool at the second end. 8. The thread groove machining method according to claim 7, wherein the thread groove machining method cuts a symmetrical position with respect to the thread groove center in the forward path and the backward path by rolling. [9] A work is mounted on a processing apparatus including a head that supports the cutting tool, a head that performs quenching, and a head that supports the rotating tool,  The thread groove processing method according to any one of claims 4 to 8, wherein the first cutting step, the quenching step, and the second cutting step are continuously performed. [10] A quenching process for quenching the peripheral surface of the workpiece,  The cutting process which processes the thread groove shallower than the quenching depth on the peripheral surface of the hardened work using the rotary tool, The method according to any one of claims 1 to 3, Thread groove machining method.  11. The thread groove machining method according to claim 10, wherein in the cutting step, an overall rotary tool corresponding to the thread groove shape is used. [12] The screw groove is formed on an inner peripheral surface of a nut assembled to a screw shaft provided with a helical screw groove.  The cutting process includes  Forming a rolling groove that constitutes a rolling path of the rolling element together with the thread groove of the screw shaft to a length less than one round of the inner circumference of the nut;  The thread groove processing method according to claim 10 or 11, further comprising a step of forming a circulation groove for circulating the rolling elements in the rolling path from one end of the rolling groove to the other end.