JP6999263B2 - Manufacturing method and machine tool for multiple ball screws - Google Patents

Description

The present invention relates to a method for manufacturing a plurality of ball screws and a machine tool using such a plurality of ball screws.

Conventionally, a plurality of ball screws may be used in a moving mechanism for moving a moving object such as a spindle of a machine tool. For example, Patent Document 1 describes an example of a machine tool adopted as a moving mechanism in which a twin ball screw using two ball screws moves a spindle. If a plurality of ball screws are used, the rigidity of the moving mechanism is increased, which is advantageous when the spindle is moved in the vertical direction.

While the ball screw is preferably used as the moving mechanism of the spindle, if a plurality of ball screws are used for the moving mechanism, the positioning accuracy may decrease due to the staggering error of each ball screw. The stagger error means the fluctuation v _2π specified in JIS B1192, that is, the periodic fluctuation that occurs when the ball screw makes one rotation.

Here, the influence of the stagger error on the movement of the spindle will be described in detail with reference to FIGS. 5 to 7. FIG. 5 is a schematic front view schematically showing the movement mechanism of the ram in the portal machining center using the twin ball screw, and FIG. 6 is a diagram showing an error when each ball screw of the twin ball screw of FIG. 5 makes one rotation. FIG. 7 is a diagram for explaining an error occurring in the tip position of the spindle supported by the ram of FIG.

As shown in FIG. 5, in a portal machining center using a twin ball screw, a ram R including a rotation spindle is supported by two ball screws 10 and 20 extending in the Z-axis direction. The ball screws 10 and 20 are arranged parallel to each other with a predetermined interval in the Y-axis direction. The ram R is supported via nuts 31 and 32 so as to be able to advance and retreat in the direction perpendicular to the two ball screws 10 and 20 (Z-axis direction), and the ball screws 10 and 20 are simultaneously driven to rotate in the same direction at a constant speed. By doing so, it is moved in the Z-axis direction (vertical direction in FIG. 5). On the other hand, although not shown, the ram R of the present embodiment is supported by a linear motion guide, and its movement in the XY direction is restricted. However, due to the above-mentioned stagger error, an error in the Y-axis direction occurs at the position of the tip of the ram R (lower end in FIG. 5), that is, the tip of the rotation spindle when moving in the Z-axis direction. This error will be described in more detail with reference to FIGS. 6 and 7.

Two curves are shown in FIG. 6, of which the curve shown by the solid line on the left side shows the actual movement amount error curve when one of the ball screws 10 makes one rotation, and is shown by the broken line on the right side. The curve shows the actual movement amount error curve when the other ball screw 20 makes one rotation. On each curve, an error of the ideal movement amount, that is, straight lines I1 and I2 of the alternate long and short dash line showing an error of 0 with respect to the movement amount are superimposed and shown. Here, as shown in FIG. 6, the case where the actual movement amount error curves of the ball screws 10 and 20 are both sinusoidal curves having an amplitude of a and their phase difference is 180 ° is illustrated. According to FIG. 6, one of the ball screws 10 has a negative error state in which the actual movement amount is smaller than the ideal movement amount in the range where the rotation angle is larger than 0 ° and smaller than 180 °. On the other hand, in the range where the rotation angle is larger than 180 ° and smaller than 360 °, the actual movement amount is larger than the ideal movement amount and is in a positive error state. On the other hand, the other ball screw 20 has a positive error in the actual movement amount larger than the ideal movement amount in the range where the rotation angle is larger than 0 ° and smaller than 180 °. In the range where the rotation angle is larger than 180 ° and smaller than 360 °, the actual movement amount is smaller than the ideal movement amount and is in a negative error state. However, in any of the ball screws 10 and 20, the error of the actual movement amount becomes 0 at the positions of 180 ° and 360 °.

When the ram R is moved by such two ball screws 10 and 20, the other ball screw 20 is larger than the amount of movement of the ram R by one ball screw 10 in the range where the rotation angle is larger than 0 ° and smaller than 180 °. The amount of movement of the ram R by is larger. Therefore, in this angle range, as shown in I of FIG. 7, the tip position of the ram R with respect to the spindle head (not shown) supporting the ram R is in the positive direction of the Y axis (FIG. 7). A posture change (tilt) that moves to the left) occurs. In particular, when the rotation angle is 90 °, the nut 31 screwed to one ball screw 10 has a negative error of a, and the nut 32 screwed to the other ball screw 20 has a positive error of a. , The inclination of the ram with respect to the spindle head is maximized. When the rotation angle is 180 °, there is no error in the actual movement amount of each of the ball screws 10 and 20, so that the ram R does not tilt with respect to the spindle head as shown in II of FIG. The error of the tip position becomes 0. When the rotation angle exceeds 180 °, the amount of movement of the ram R by the other ball screw 20 becomes smaller than the amount of movement of the ram R by one ball screw 10. Therefore, in this angle range, as shown in III of FIG. 7, the ram R has a posture in which the tip position thereof moves in the negative direction of the Y axis (to the right in FIG. 7) with respect to the spindle head. A change (tilt) occurs. In particular, when the rotation angle is 270 °, a positive error of a occurs in the nut 31 screwed to one ball screw 10, and a negative error of a occurs in the nut 32 screwed to the other ball screw 20. , The inclination of the ram with respect to the spindle head is maximized. The states indicated by the reference numerals I, II, and III in FIG. 7 correspond to the phases indicated by the reference numerals I, II, and III in FIG. 6, respectively.

In this way, due to the staggering error of the two ball screws 10 and 20, every time the two ball screws 10 and 20 make one rotation, one swinging motion is generated in the ram R, and the swinging motion is generated in the Z-axis direction. When it is moved, it repeats one cycle of swinging with one lead. The swinging motion of the spindle due to the staggering error of the ball screw is not limited to the portal machining center, but also in the lateral boring machine and other general moving mechanisms in which a moving mechanism having two ball screws is adopted. Can occur. In FIG. 7, the error in the tip position of the spindle due to the staggering error of the two ball screws 10 and 20 is exaggerated. The actual error is, for example, about several μm.

To solve such a problem, for example, Patent Document 2 proposes a method of canceling a stagger error with a spring. However, the method using a spring cannot exert its effect on the spindle of a machine tool that receives an external force during cutting.

It is also conceivable to attach one scale to one ball screw and perform feedback control using a total of two scales. However, it is not realistic to attach two scales to one drive system because the cost is high.

Generally, the movement amount error of the ball screw (error between the representative movement amount and the reference movement amount) can be measured and confirmed. However, since the stagger error is a minute error within one lead, it is not regarded as a problem and has not been confirmed. Further, when one ball screw is used for one drive system, if the feedback from the scale is used, the stagger error is also corrected when the representative movement amount error is corrected, so that it is not regarded as a problem.

The stagger error that occurs when each ball screw makes one rotation has a large effect when driven by two ball screws. To eliminate the effect of this stagger error, use a ball screw that does not have a stagger error, or make the size of the stagger error of the two ball screws uniform, and use the ball screw when assembling the ball screw to the machine tool. It is necessary to align the rotation phases. However, it is considered that the stagger error is influenced by the error caused by one rotation of the work material (ball screw) of the grinding machine, so it is not realistic to eliminate the stagger error itself.

In order to make the magnitude of the stagger error uniform, it is sufficient to make the error caused by one rotation of the work material uniform, so it is considered possible to deal with it by using the same grinding machine.

In order to align the phase of the stagger error, the phase of the stagger error is estimated and adjusted from the error generated in the moving object such as the ram. Specifically, in order to align the phases of the stagger error, attach the nuts of the two ball screws to the moving object, fix the phases of these nuts, and then shift the phase of one nut by the required amount. The method of inserting a kanza or the like is adopted.

However, such adjustment of the phase of the stagger error is performed after the ball screw is attached to the machine tool or the like, and it is difficult to confirm the error amount. Therefore, it has been desired to make the magnitude, position, and phase of the stagger error uniform at the level of a single component of a plurality of ball screws.

Japanese Unexamined Patent Publication No. 11-99422 Japanese Unexamined Patent Publication No. 03-263658

As a result of diligent studies, the inventor of the present invention has found that the above-mentioned error in the tip position of the spindle can be eliminated by aligning the magnitude and phase of the stagger error between a plurality of (for example, two) ball screws. did.

The present invention is based on the above findings. That is, an object of the present invention is to provide a method for manufacturing a plurality of (for example, two) ball screws in which the stagger error is rotationally synchronized (position and phase are synchronized).

Further, an object of the present invention is to provide a machine tool that eliminates an error in the tip position of the spindle due to a staggering error and does not cause tool wobbling with respect to a moving shaft using such a plurality of ball screws, and is stable. It is to realize the machined surface.

The method for manufacturing a plurality of ball screws according to the present invention includes a first preparation step of preparing a first ball screw having a roughened screw groove and a first preparation step.
The first mounting process of mounting the first ball screw on the grinding machine and
The first grinding step of grinding the thread groove of the first ball screw and
A second preparation step of removing the first ball screw from the grinding machine and preparing a second ball screw having a roughened screw groove.
The second mounting process of mounting the second ball screw on the grinding machine, and
The position of one end face of the second ball screw in the longitudinal direction with respect to the grinding machine is set to the same position as the position of one end face in the longitudinal direction of the first ball screw when the first ball screw is ground. At the same time, the phase of one end of the thread groove of the second ball screw is set to be the same phase as the phase of one end of the thread groove of the first ball screw when the first ball screw is ground. Setting process and
A second grinding step of grinding the thread groove of the second ball screw is provided.

According to the present invention, in each of the two ball screws, the screw groove is ground by the same processing machine with the position of one end face in the longitudinal direction and the phase of one end of the screw groove aligned. .. This makes it possible to provide a method for manufacturing a plurality of ball screws in which the stagger error is rotationally synchronized.

In the above manufacturing method, one end having an engaging portion that can be engaged with the grinding machine and the other end having an abutting surface that abuts on one end face in the longitudinal direction of the ball screw to be machined. Further equipped with a process of preparing a jig having,
The first mounting step includes a step of attaching the jig to the first ball screw.
The second mounting step may include a step of attaching the jig to the second ball screw.

In this case, the distance between the one end face of the first ball screw with respect to the grinding machine and the one end face of the second ball screw with respect to the grinding machine by the jig, that is, the longitudinal direction in each of the two ball screws. The position of one end face can be reliably aligned.

The above jig has a bottomed tubular first nut and a tubular second nut.
The engaging portion is provided on the outer surface of the bottom of the first nut.
The contact surface is provided on the end surface of the second nut.
The first nut and the second nut may be screwed to a male screw portion provided at one end of the ball screw to be machined so as to form a double nut.

In this case, since the jig can be fixed to the plurality of ball screws so as not to be loosened extremely easily, the plurality of ball screws can be rotationally synchronized with high accuracy.

Further, the manufacturing method includes a step of preparing an auxiliary jig having a marker portion indicating the phase of one end of each screw groove of the first ball screw and the second ball screw for the grinding machine.
Further provided with a step of setting the auxiliary jig in the grinding machine,
For the first ball screw and the second ball screw, the phase of one end of each screw groove may be set to a predetermined phase by referring to the marker portion of the auxiliary jig.

In this case, the stagger error of each ball screw can be reliably rotated and synchronized.

Alternatively, it is also possible to realize the setting process without using a jig. That is, in the manufacturing method, the position of one end face in the longitudinal direction of the second ball screw when the second ball screw is mounted on the grinding machine is the position when the first ball screw is mounted on the grinding machine. A step of processing the second ball screw may be further included so that the position of one end face of the first ball screw is the same.

Also in this case, in each of the two ball screws, the screw groove is ground by the same processing machine with the position of one end face in the longitudinal direction and the phase of one end of the screw groove aligned. This makes it possible to provide a method for manufacturing a plurality of ball screws in which the stagger error is rotationally synchronized.

Alternatively, a machine tool having a plurality of ball screws manufactured by the above manufacturing method is also within the scope of the present invention.

That is, the present invention is a moving object and
A plurality of ball screws, which are arranged parallel to each other and for driving and positioning the moving object in a predetermined direction, are provided.
It is a machine tool characterized in that the phases of the stagger error of the plurality of ball screws coincide with each other along the longitudinal direction of each ball screw.

According to the present invention, with respect to a moving shaft using a plurality of ball screws whose stagger error is rotationally synchronized, the tilt of the tip of the spindle via a moving object such as a ram due to the stagger error is eliminated and the tool does not wobble. It is possible to provide a machine tool and realize a stable machined surface.

Specifically, the plurality of ball screws are two ball screws.

According to the present invention, it is possible to provide a method for manufacturing a plurality of ball screws in which the stagger error is rotationally synchronized.

Alternatively, according to the present invention, with respect to a moving shaft in which a plurality of ball screws whose staggering error is rotationally synchronized are adopted, a moving object due to the staggering error, for example, an error in the position of the tip of the spindle is eliminated to cause the tool to wobble. It is possible to provide a machine tool that does not occur and realize a stable machined surface.

It is a figure for demonstrating the manufacturing method by one Embodiment of this invention, and the grinding machine is shown in the side view. It is a figure which shows the actual movement amount curve in the state where the magnitude and the phase of the stagger error of two ball screws are aligned. FIG. 2 is a diagram showing a state in which the two ball screws of FIG. 2 are moved in the negative direction of the Z axis without causing an error in the tip position of the spindle supported by the ram. It is a schematic vertical sectional view which shows the auxiliary jig attached to the ball screw. It is a schematic front view which shows typically the moving mechanism of a ram in a gantry machining center which adopted a twin ball screw. It is a figure which shows the error when each ball screw of the twin ball screw of FIG. 5 makes one rotation. It is a figure for demonstrating the error which occurs in the tip position of the spindle supported by the ram of FIG.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram for explaining a manufacturing method according to an embodiment of the present invention, and the grinding machine 100 is shown in a side view.

As shown in FIG. 1, the ball screw 210 to be ground by the present manufacturing method has a columnar outer shape having a longitudinal direction (left-right direction in FIG. 1), and a screw groove is ground by a grinding machine 100. It has a portion 211 and small diameter portions 212 and 213 provided at both ends of the screw portion 211. The ball screw 210 is attached to the machine tool via these small diameter portions 212 and 213. Further, a datum surface 216 is provided on an annular end surface surrounding one small diameter portion 212, which is located at one end (left side in FIG. 1) of the screw portion 211. The datum surface 216 is a reference surface used for positioning the machine tool when the ground first ball screw is attached to the machine tool. Further, a recess 215 is provided on the end surface of the other small diameter portion 213. Since the second ball screw 220, which will be described later, is also ground by the grinding machine 100, reference numerals corresponding to each component of the second ball screw 220 are also shown in FIG.

Further, as shown in FIG. 1, the grinding machine 100 has a base 110 and a face plate base 120 provided on the base 110, and a face plate 130 as a spindle driven to be rotated is attached to the face plate base 120. There is. Further, on the base 110, a tailstock 140 for supporting a work arranged on the other side of the face plate 130 at a predetermined distance from the face plate 130 is provided. As an example, the base 110 is a rectangular bed (base) having a length exceeding the length of the ball screw 210 to be machined, and is installed horizontally. The face plate 130 is arranged near one end of the base 110 (left side in FIG. 1) so as not to move in the longitudinal direction of the ball screw 210, and the face plate 130 transmits the rotational motion to the ball screw 210. A button 160 is provided to connect the drive unit and the ball screw 210.

A tailstocking portion 150 is attached to the face plate 130. As will be described later, the tailstock portion 150 engages with an engaging portion 412 provided on a jig 400 attached to one small diameter portion 212 of the ball screw 210 to support one end of the ball screw 210. It has a conical first convex portion 151 at its tip.

The tailstock 140 is movable on the base 110 in the length direction of the base 110. Further, on one side of the tailstock 140, a conical second convex portion for engaging with the concave portion 215 provided in the other small diameter portion 213 of the ball screw 210 to support the other end of the ball screw 210. 141 is provided. The first convex portion 151 and the second convex portion 141 are arranged along the length direction of the base 110. Since the first ball screw 210 is pressed and supported by the first and second convex portions 151 and 141 in the concave portion 215 and the engaging portion 412, its longitudinal position depends on the processing depth of the concave portions 215 and the engaging portion 412 at both ends. It will be decided.

Next, a jig 400 for processing the screw grooves 217 and 227 of the first and second ball screws 210 and 220 so as to be rotationally synchronized with high accuracy will be described with reference to FIG.

FIG. 4 is a schematic vertical sectional view showing the jig 400. This jig 400 is arranged between the datum surfaces 216 and 226 of the first and second ball screws 210 and 220 and the tailstock portion 150 of the grinding machine 100, and is arranged between the datum surfaces of the first ball screw 210 with respect to the grinding machine 100. The purpose is to align the position of 216 with the position of the datum surface 226 of the second ball screw 220 with respect to the grinding machine 100.

As shown in FIG. 4, the jig 400 abuts on one end 411 having an engaging portion 412 engageable with the grinding machine 100 and the datum surfaces 216 and 226 of the ball screws 210 and 220 to be machined. The other end 421 having the contact surface 422 is provided. Specifically, the jig 400 has a bottomed tubular first nut 410 and a tubular second nut 420, and the engaging portion 412 is provided on the outer surface of the bottom of the first nut 410. The contact surface 422 is provided on the end surface of the second nut. The first nut 410 and the second nut 420 form a double nut on the male screw portions 212a and 222a of the one small diameter portion 212 and 222 provided at one end of the ball screws 210 and 220 to be machined. It is designed to be screwed into.

As shown in FIG. 4, the first nut 410 is a bottomed tubular nut with one side (left side in FIG. 4) closed. On the outer surface of the bottom of the first nut 410, a mortar-shaped recess having the rotation axis of the first nut 410 as a central axis is formed as an engaging portion 412. The bottom portion is provided at a position where the first nut 410 and the second nut 420 are screwed to the male screw portions 212a and 222a and do not interfere with the tips of the male screw portions 212a and 222a. Further, on the other side of the first nut 410 (on the right side in FIG. 4), a first sleeve portion 413 having a thickness relatively thinner than that of the other regions is provided. The inner peripheral surface of the first sleeve portion 413 is a cylindrical surface, and as will be described later, when screwed to the male screw portions 212a and 222a, a part of the second nut 420 is accommodated without a gap. It is supposed to be done. As a result, the centering (centering) of the first nut 410 with respect to the second nut 420 is performed.

Further, as shown in FIG. 4, the second nut 420 is a tubular nut, and has a screwed portion 423 formed with a female threaded portion screwed to the male screw portions 212a and 222a, and the screwed portion. It has a second sleeve portion 424 integrally provided on the other side of the 423 (right side in FIG. 4). In the present embodiment, the screwed portion 423 has a cylindrical shape, and its outer diameter is equal to the inner diameter of the first sleeve portion 413 of the first nut 410. On the other hand, the inner surface of the second sleeve portion 424 is a circumferential surface, so that the second sleeve portion 424 fits tightly with one of the small diameter portions 212 and 222 of the ball screws 210 and 220 without a gap. As a result, the second nut 420 is centered (centered) with respect to one of the small diameter portions 212 and 222.

Next, a process of grinding a thread groove in the threaded portion 211 by the grinding machine 100 will be described. Here, as an example, a case where the screw grooves 217 and 227 of the two ball screws 210 and 220 constituting the twin ball screw type moving mechanism are ground will be described.

In the present manufacturing method, first, a first ball screw 210 in which the screw groove 217 is ground is prepared. The first ball screw 210 is formed with a screw groove 217'roughened in advance by an appropriate grinding device. The pitch of the rough-processed screw groove 217'is appropriately determined according to the specifications of the machine tool to which the ball screws 210 and 220 are attached.

First, prior to the grinding process, the jig 400 is attached to one small diameter portion 212 of the first ball screw 210. Specifically, the second nut 420 is screwed into the male screw portion 212a of the first ball screw 210 until the contact surface 422 of the second nut 420 abuts on the datum surface 216 of the first ball screw 210. At the time of this screwing, the inner peripheral surface of the second sleeve portion 424 fits tightly with the outer peripheral surface of one small diameter portion 212 of the first ball screw 210. As a result, the second nut 420 is screwed to one of the small diameter portions 212 while being centered (centered).

Next, the first nut 410 is screwed into the male screw portion 212a. At this time, in the first nut 410, the inner peripheral surface of the first sleeve portion 413 fits tightly with the outer peripheral surface of the screwed portion 423 of the second nut 420. As a result, the first nut 410 is screwed to the second nut 420 while being centered (centered). That is, the first nut 410 is screwed to one of the small diameter portions 212 while being centered (centered) via the second nut. Then, when the bottom surface of the recess formed in the first sleeve portion 413 of the first nut 410 comes into contact with the tip end surface of the screwed portion 423 of the second nut 420, the screwing to the male screw portion 212a is completed.

Then, when the first nut 410 is fixed and the second nut 420 is rotated in the reverse direction in the direction of loosening with a predetermined torque in this state, a so-called double nut is formed by the first nut 410 and the second nut 420, and each nut 410, The 420 is firmly fixed to the male screw portion 212a.

In the grinding machine 100, the face plate 130 is rotationally driven and set to a predetermined phase with respect to the grinding machine 100 before the first ball screw 210 to be ground is fixed in the rotational direction with respect to the face plate 130. Then, the auxiliary jig 300 is attached to a predetermined position on the face plate 130. In the illustrated embodiment, the predetermined phase is a phase in which the predetermined position to which the auxiliary jig 300 is attached is located at the lowest position.

As shown in FIG. 1, the auxiliary jig 300 used in the present embodiment has a positioning portion 310 having a length of L1 in the longitudinal direction and orthogonal to the longitudinal direction from the other end of the positioning portion 310. It has an L-shaped outline having a phase defining portion 320 extending in the direction of the surface. One end of the positioning portion 310 can be attached to the auxiliary jig mounting portion 131 provided on the face plate 130. The other end surface 311 of the positioning portion 310 has a plane orthogonal to the longitudinal direction, and this plane serves as a first marker portion indicating the longitudinal position of the first ball screw 210 with respect to the grinding machine 100. It is designed to work. Further, the phase defining portion 320 has a length L2, and the edge portion 321 on the other side on the distal side (upper side in FIG. 1) from the positioning portion 310 is the first ball screw 210 with respect to the grinding machine 100. As a second marker portion indicating the phase of one end 217e of the rough-processed screw groove 217', it functions at the same time as the first marker portion.

When the first ball screw 210 is fixed to the grinding machine 100, the tailstock 140, which has been previously arranged with respect to the tailing portion 150 at a distance exceeding the length of the first ball screw 210, is shown in FIG. It is moved in the direction indicated by A. Due to this movement, at one end of the first ball screw 210, the first convex portion 151 engages with the engaging portion 412 (see FIG. 4) of the jig 400, and at the other end, the other small diameter. The second convex portion 141 engages with the concave portion 215 provided in the portion 213. As a result, the first ball screw 210 is pressed and supported by the first and second convex portions 151 and 141 in the concave portion 215 and the engaging portion 412, and moves in the longitudinal direction (left-right direction in FIG. 1) with respect to the grinding machine 100. Is regulated.

As described above, one end surface of the first ball screw is provided with a datum surface 216 which is a reference surface used for positioning with respect to the machine tool. In order to rotate and synchronize the stagger errors of the plurality of ball screws with each other, it is necessary to accurately position the datum surface 216 with respect to the grinding machine 100, so that the positioning is performed by mounting the jig 400 described above.

Of course, instead of adopting the jig 400, a second recess may be provided in one of the small diameter portions 212 so as to be exactly a predetermined distance from the datum surface 216. In this case, the second concave portion engages with the first convex portion 151 of the tailstock portion 150. Further, as long as the tailstock portion 150 moves in the longitudinal direction of the first ball screw 210 and the first ball screw 210 can be firmly fixed in line with the first marker, such a method may be used.

Then, the first ball screw 210 is appropriately rotated around the axis, and the phase of the first ball screw 210 is set so that one end 217e of the rough-processed screw groove 217'consists with the edge portion 321 of the positioning portion 310. To.

In this state, the face plate 130 and the first ball screw 210 are connected and fixed by a button 160, which is a transmission member for transmitting the rotational drive of the face plate 130 to the first ball screw 210. After that, a grinding tool (not shown) is brought into contact with one end 217e of the rough-processed screw groove 217'. In the example shown in FIG. 1, the button 160 is attached to the opposite side of the auxiliary jig 300 with respect to the center of rotation of the face plate 130. Then, in this state, the face plate 130 is rotationally driven. As the face plate 130 rotates, the grinding tool grinds the roughened screw groove 217'. After a predetermined grinding, the completed screw groove 217 is formed on the surface of the screw portion 211.

When the grinding is completed, the rotation of the face plate 130 is stopped, the button 160 is removed from the first ball screw 210, and the first ball screw 210 is removed from the grinding machine 100.

Next, a second ball screw 220 having a roughly machined screw groove 227'and equipped with a jig 400 used for grinding the first ball screw 210 is mounted on the same grinding machine 100. Since the procedure for mounting the second ball screw 220 on the grinding machine 100 is the same as the procedure for mounting the first ball screw 210 on the grinding machine 100, detailed description thereof will be omitted here. At this time, considering the case where the pitches of the screw grooves 217 and 227 of the first and second ball screws 210 and 220 are both 10 mm as an example, the error in the longitudinal direction of the screw grooves 217 and 227 due to the phase difference is, for example. In order to make it 0.5 mm or less, the ball screws 210 and 220 are attached to the grinding machine 100 so that the phase difference between the screw grooves 217 and 227 of the first ball screw 210 and the second ball screw 220 is within 18 °. Just attach it. The allowable range of this phase difference can be appropriately determined according to the desired processing accuracy.

Then, the rough-processed screw groove 227'is ground by a grinding tool (not shown). As a result, the completed screw groove 227 is formed on the surface of the screw portion 221. When the grinding is completed, the second ball screw 220 is removed from the grinding machine 100 in the same manner as in the case of the first ball screw 210.

According to the manufacturing method as described above, the position of the grinding tool with respect to the grinding machine 100 when grinding a specific position of the screw groove 217'with respect to the datum surface 216 with respect to the first ball screw 210. With respect to the second ball screw 220, the position of the grinding tool with respect to the grinding machine 100 when grinding a specific position of the screw groove 227'with respect to the datum surface 226 is the same. That is, even if the first and second ball screws 210 and 220 include a stagger error, their sizes and phases are aligned with respect to the datum surface 216.

Next, with reference to FIGS. 2 and 3, the operation of the moving mechanism using the twin ball screw by the first and second ball screws 210 and 220 thus manufactured will be described. FIG. 2 is a diagram showing an actual movement amount curve in a state where the magnitude and phase of the stagger error of the two ball screws 210 and 220 are aligned, and FIG. 3 is a diagram showing the actual movement amount curves of the two ball screws 210 and 220 by the two ball screws 210 and 220 of FIG. , Is a diagram showing a state in which the tip position of the spindle supported by the ram is moved in the negative direction of the Z axis without causing an error.

Two curves are shown in FIG. 2, of which the curve shown by the solid line on the left side shows the actual movement amount curve when one of the ball screws 10 makes one rotation, and is shown by the broken line on the right side. The curve shows the actual movement amount curve when the other ball screw 20 makes one rotation. Similar to FIG. 6, the straight lines I1 and I2 of the alternate long and short dash line indicating the ideal amount of movement are superimposed on each curve. As can be understood from FIG. 2, the first and second ball screws 210 and 220 of the present embodiment both include a sinusoidal stagger error having an amplitude of a, but their sizes and phases are aligned. Has been done.

When the ram R is moved by such two ball screws 210 and 220, each ball screw 210 and 220 causes a plus error of the same magnitude in a range where the rotation angle is larger than 0 ° and smaller than 180 °. For example, as shown in FIG. 3, when the rotation angle is 90 °, an error (excess) of + a occurs in both of the two nuts 31 and 32. Therefore, the posture of the ram R does not change within the range of the rotation angle.

Similarly, each ball screw 210, 220 causes a negative error of the same magnitude in a range where the rotation angle is larger than 180 ° and smaller than 360 °. For example, as shown in FIG. 3, when the rotation angle is 270 °, both the nuts 31 and 32 have an error of −a (not enough). Therefore, the posture of the ram R does not change within the range of the rotation angle.

As described above, when the ram R supporting the rotating spindle is moved in the negative direction of the Z axis by the two ball screws 210 and 220, the parallel state between the axis of the spindle and the Z axis is always maintained. In addition, in FIG. 3, in order to avoid complication, only the nut 32 is shown instead of the ram R at the rotation angles of 90 ° and 270 °.

According to the manufacturing method of the present embodiment as described above, according to the present invention, in each of the two ball screws 210 and 220, the position of one end face in the longitudinal direction and one end of the screw grooves 217 and 227. The screw groove is ground by the same processing machine with the phases aligned. This makes it possible to provide a method for manufacturing a plurality of ball screws 210 and 220 in which the stagger error is rotationally synchronized.

In the above manufacturing method, the other end having an engaging portion 412 that can be engaged with the grinding machine 100 and the other end having an abutting surface 422 that abuts on one end surface in the longitudinal direction of the ball screw to be machined. A jig 400 with an end is used. As a result, the distance between the one end face of the first ball screw 210 with respect to the grinding machine 100 and the one end face of the second ball screw 220 with respect to the grinding machine 100, that is, the distance between the two ball screws 210 and 220. The position of one end face in the longitudinal direction in each can be reliably aligned.

Further, the jig 400 has a bottomed tubular first nut and a tubular second nut, and these nuts are male screw portions provided at one end of the ball screws 210 and 220 to be machined. Is screwed into the double nut to form a double nut. As a result, the jig 400 can be fixed to the two ball screws 210 and 220 so as not to be loosened extremely, so that the two ball screws 210 and 220 can be rotationally synchronized with high accuracy.

Further, in this manufacturing method, an auxiliary jig having a second marker portion indicating the phase of one end 217e and 227e of each screw groove 217', 227'of the first ball screw 210 and the second ball screw 220 with respect to the grinding machine 100. Using 300, the phase of one end of each screw groove is set to a predetermined phase. Therefore, in this case, the stagger error of each of the ball screws 210 and 220 can be reliably rotated and synchronized. Further, since it can be confirmed by using the first marker portion whether or not the distance between the face plate 130 of the grinding machine 100 and the datum surface 216 and 226 is appropriate, the position of the datum surface 216 and 226 with respect to the face plate 130 can be confirmed. Can be determined accurately.

According to the twin ball screw type machine tool using the first and second ball screws 210 and 220 as described above, as can be understood from FIGS. 2 and 3, the stagger error of the first and second ball screws 210 and 220 It is possible to provide a machine tool that does not cause tool wobbling by eliminating the error in the tip position of the spindle caused by the above, and to realize a stable machined surface.

Of course, the manufacturing method of a plurality of ball screws by the manufacturing method as described above can be applied not only to a portal machining center but also to various machine tools such as a horizontal boring machine, and further, the manufacturing method is not limited to the machine tool and has high accuracy. It can also be applied to general moving mechanisms that require flexible position control. Further, the number of ball screws used in such a machine tool or a moving mechanism is not limited to two, and may be three or more. When processing the third and subsequent ball screws, exactly the same method as the manufacturing method of the first and second ball screws 210 and 220 described above can be adopted.

10 One ball screw 20 The other ball screw 100 Grinding machine 110 Base 120 Face plate Base 130 Face plate 131 Auxiliary jig mounting part 140 Pushing base 141 Second convex part 150 Pushing part 151 First convex part 160 Kere 210 First ball screw 211 Threaded part 212, 213 Small diameter part 212a Male threaded part 217 Completed threaded groove 217'Roughly machined threaded groove 217e One end of threaded groove 215 Recessed 216 Datum surface 220 Second ball screw 221 Threaded part 222, 223 Small diameter part 222a Male screw part 227, 227'Screw groove 226 Datum surface 300 Auxiliary jig 310 Positioning part 311 Other end face 320 Phase defining part 321 Edge of positioning part 400 Jig 410 First nut 411 One end 412 Engagement Part 413 1st sleeve part 420 2nd nut 421 Other end part 422 Contact surface 423 Screwing part 424 2nd sleeve part I1, I2 Ideal movement amount R Ram

Claims (7)

The first preparation process for preparing the first ball screw with the thread groove roughly processed, and
The first mounting process of mounting the first ball screw on the grinding machine and
The first grinding step of grinding the thread groove of the first ball screw and
A second preparation step of removing the first ball screw from the grinding machine and preparing a second ball screw having a roughened screw groove.
The second mounting process of mounting the second ball screw on the grinding machine, and
The position of the datum surface located at one end of the second ball screw in the longitudinal direction with respect to the grinding machine is located at one end of the first ball screw in the longitudinal direction when the first ball screw is ground. The position is set to be the same as the position of the datum surface, and at the same time, the phase of one end of the thread groove of the second ball screw is set to one of the thread grooves of the first ball screw when the first ball screw is ground. A setting step of setting the phase to be the same as the phase of the end of the ball, and a second grinding step of grinding the thread groove of the second ball screw.
A method of manufacturing a plurality of ball screws, which is characterized by being equipped with. One end having an engaging portion engageable with the grinding machine and the other end having an abutting surface abutting on a datum surface located at one end in the longitudinal direction of the ball screw to be machined. Further equipped with a process of preparing a jig having a
The first mounting step includes a step of attaching the jig to the first ball screw.
The manufacturing method according to claim 1, wherein the second mounting step includes a step of attaching the jig to the second ball screw. The jig has a bottomed tubular first nut and a tubular second nut.
The engaging portion is provided on the outer surface of the bottom of the first nut.
The contact surface is provided on the end surface of the second nut.
2. The second aspect of the present invention, wherein the first nut and the second nut are screwed to a male screw portion provided at one end of a ball screw to be machined so as to form a double nut. Manufacturing method. A step of preparing an auxiliary jig having a marker portion indicating the phase of one end of each screw groove of the first ball screw and the second ball screw for the grinding machine.
The process of setting the auxiliary jig in the grinding machine and
Further prepare
The first ball screw and the second ball screw are characterized in that the phase of one end of each screw groove is set to a predetermined phase by referring to the marker portion of the auxiliary jig. The manufacturing method according to any one of 3. The position of the datum surface located at one end of the second ball screw in the longitudinal direction when the second ball screw is mounted on the grinding machine is the position when the first ball screw is mounted on the grinding machine. 1. The manufacturing method according to claim 1, further comprising a step of processing the second ball screw so that the position of the datum surface located at one end of the ball screw is the same. Objects to move and
A plurality of ball screws arranged parallel to each other and for driving and positioning the moving object in a predetermined direction,
Equipped with
The phases of the stagger error of the plurality of ball screws coincide with each other along the longitudinal direction of each ball screw.
At the component level of the plurality of ball screws, the magnitude, position, and phase of the stagger error of the plurality of ball screws are aligned with respect to the datum surface located at one end of each ball screw in the longitudinal direction. A featured machine tool. The machine tool according to claim 6, wherein the plurality of ball screws are two ball screws.

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