Automatic tool changer for ultrasonic vibration machining equipment

Abstract

An automatic tool changer for an ultrasonic vibration machining device is provided that can stably obtain an optimum fastening torque regardless of individual differences in the shape of tool holders due to manufacturing. [Solution] The device comprises a tool holder body, a plurality of tool holders each having parallel rotation constraint portions on at least two sides and a male or female thread portion on the opposite side of the tool, a horn portion 1 having a female or male thread portion inside a hollow interior, an ultrasonic vibrator 16 that applies ultrasonic vibrations to the horn portion, a piezoelectric element 17 sandwiched in the middle of the ultrasonic vibrator, and a rotary connector 18 that shares a power source with the piezoelectric element via wiring, and is equipped with a spindle 13 that can be rotated by a spindle motor 14, a Z-axis motor that moves the spindle in the Z-axis direction, a tool magazine fitting that fits into the rotation constraint portion of the tool holder to hold it, and a control unit that controls the operation of the spindle, and for each tool holder, a phase setting value is input into the display device of the control device and stored in memory, and the phase of the spindle is controlled.

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic vibration machining device. [Background technology]

[0002] In processes such as cutting and grinding using ultrasonic vibration, there is a demand for ultrasonic vibration machining equipment that allows frequent tool changes and diverse machining. Generally, the workpieces that are subjected to ultrasonic vibration machining are often brittle materials, which means that machining takes a very long time. In addition, many of the workpieces to be machined are very small, but there is also a demand for ultrasonic vibration machining equipment that can machine relatively large workpieces, including not only brittle materials but also metals. In any case, one of the challenges in cutting and grinding using ultrasonic vibration is how to shorten the machining time while maintaining the quality of precision machining.

[0003] Patent Document 1 discloses a spindle unit that can be applied to the automatic tool changers of existing machine tools to meet the demand for frequent tool changes. This spindle unit has a horn with an ultrasonic vibrator built into the tip of the spindle, and a tool holder is attached to the tip of the horn. A drawbar is inserted into a through hole that passes through the axis of the horn, and by driving the drawbar in the clamping / unclamping direction, the tool holder is automatically changed, thereby overcoming the challenge of reducing the machining cycle time.

[0004] Furthermore, this spindle device has an ultrasonic vibrator built into the tip of the spindle, so the ultrasonic vibrator does not need to be attached or detached during automatic tool changes, which stabilizes power supply and ensures stable transmission of ultrasonic vibrations to the tool holder, while also solving the problem of high tool holder costs.

[0005] However, in Patent Document 1, the ultrasonic vibrator, which was conventionally placed in a tool holder that holds a tool, is simply incorporated into the horn portion at the tip of the spindle, which increases the length of the spindle unit and does not actually solve the problem of the device becoming larger. In other words, in existing machine tools, increasing the length of the tip of the spindle unit means that the maximum tool length of the tool that can be held becomes shorter.

[0006] One of the advantages of placing the ultrasonic vibrator on the spindle side rather than inside the tool holder is that the ultrasonic vibrator can be made larger, enabling high-output ultrasonic oscillation and making it possible to machine large workpieces with large-diameter tools.However, as mentioned above, if the maximum tool length is shortened, this advantage cannot be fully utilized.

[0007] Therefore, in Patent Document 2, an ultrasonic vibrator and a support horn that transmits the ultrasonic vibrations excited by the ultrasonic vibrator to the machining tool via the tool holder are installed inside a hollow main body sleeve formed in the spindle. This not only stabilizes the power supply and enables the ultrasonic vibrations to be transmitted stably to the tool holder, but also prevents the length of the spindle device from becoming too long, solving the problem of maximum tool length.

[0008] Furthermore, the machine employs automatic tool change, in which the support horn and tool holder are attached and detached by screws as the spindle rotates. As with Patent Document 1, this meets the demand for frequent tool changes and overcomes the challenge of reducing cycle time.

[0009] However, Patent Document 2 does not take into consideration the fact that the phase at which the male thread starts to be cut differs for each individual tool holder, and that the distance between the upper end face of the tool holder on the side where the tool holder is fastened to the horn portion and the uppermost end of the rotation constraint portion of the tool holder differs.

[0010] No matter how standardized a tool holder is, or how accurately the threading position and rotation restriction part position are specified on the drawing, it is extremely difficult to completely eliminate the subtle tolerances of tens to hundreds of microns that occur for each individual tool during manufacturing.

[0011] For example, as shown in Figure 1, if tool holder T1 and tool holder T2 have different phases T1a and T2a at the start of cutting the male thread, respectively, simply controlling the rotation angle of the spindle so that the angles of the two faces of the rotation constraint portions T1b and T2b of tool holders T1 and T2 match the shape of the holder receiving hole in the tool stocker and fastening the horn portion to the tool holder will actually result in the phase at which the optimal fastening torque is obtained being different for tool holders T1 and T2, and therefore the optimal fastening torque may not be obtained.

[0012] 2 also shows a case where tool holder T1 and tool holder T2 have different Z-axis distances T1h and T2h between the top end faces T1c and T2c of the tool holder that are fastened to horn portion 1 and the top ends (Z-axis reference positions) T1d and T2d of the tool holder's rotation constraint portion that engages with holder receiver 2 of the tool stocker. Even if a shock absorbing material is used to absorb this difference in Z-axis distance when tool holders T1 and T2 are pressed against horn portion 1, the load in the Z-axis direction is different for tool holders T1 and T2, which affects the rotational torque value of the spindle motor and may prevent the optimum fastening torque from being obtained. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-166303 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-39627 Summary of the Invention [Problem to be solved by the invention]

[0014] In view of the above-mentioned problems, the present invention aims to provide an automatic tool changer for an ultrasonic vibration machining device that can stably obtain the optimal fastening torque regardless of individual differences in the tool holder (shape due to manufacturing). [Means for solving the problem]

[0015] The automatic tool changer for an ultrasonic vibration machining device according to the present invention comprises a holder body to which a tool is fixed, a plurality of tool holders in the holder body, each having a rotation restriction portion on at least two parallel faces and a male or female thread portion on the side opposite the tool, a horn portion having a female or male thread portion within a hollow interior, an ultrasonic vibrator that applies ultrasonic vibration to the horn portion, a piezoelectric element sandwiched in the middle of the ultrasonic vibrator, and a rotary connector that shares a power source with the piezoelectric element via wiring, and the spindle is rotatable by a spindle motor, a Z-axis motor that moves the spindle in the Z-axis direction, and a fitting that fits into the rotation restriction portion of the tool holder and holds the tool holder one by one. and a control device that controls the operation of the spindle so that the female or male thread of the horn and the male or female thread of the tool holder are fastened or unfastened to or from each other by rotating and advancing or retreating the spindle in accordance with a predetermined spindle angle and Z-axis movement amount, thereby allowing the tool holder to be detachably replaced on the spindle. A phase setting value for each tool holder is input to a display device of the control device and stored in memory, and when a tool is replaced, the phase setting value of the tool holder to be replaced is read out, the phase of the spindle at the start of threading is calculated, and the calculated phase is sent to the spindle motor to control the phase of the spindle.

[0016] Furthermore, a Z-axis compensation value may be input to the display device of the control device for each tool holder and stored in memory, and when changing a tool, the Z-axis compensation value of the tool holder for which the tool is to be changed may be read out, the Z-axis position at the start of screwing may be calculated, and a command may be sent to the Z-axis motor to control the Z-axis position of the spindle.

[0017] The phase setting value is the angular difference between the reference phase for tool change of the spindle, in which the fitting portion and the rotation constraint portion are parallel, and the phase at which thread cutting of the male or female thread portion of the tool holder begins.

[0018] The Z-axis correction value is the difference between the distance between the Z-axis reference position of the rotation constraint part fitted to the fitting part and the Z-axis reference position of the upper end face of the tool holder, and the Z-axis reference position of the rotation constraint part fitted to the fitting part and the actual Z-axis position of the upper end face of the tool holder. [Effects of the Invention]

[0019] The automatic tool changer for the ultrasonic vibration machining equipment of the present invention realizes automatic tool change that enables screw fastening with optimal fastening torque without being affected by individual differences in the shape of each tool holder, simply by rotating and advancing the spindle according to the specified spindle angle and Z-axis movement amount.

[0020] Furthermore, with the automatic tool changer for the ultrasonic vibration machining device according to the present invention, by measuring the thread cutting start phase of the male or female thread portion of the tool holder for each tool holder and the distance between the Z-axis reference position and the upper end face of the tool holder, the tool holder can be gripped in the fitting portion without being affected by tolerance differences of tens to hundreds of microns that arise due to individual differences in the tool holder, thereby preventing collisions and wear on the male and female thread portions and extending the life of the tool holder body. [Brief explanation of the drawings]

[0021] [Figure 1] 3A and 3B are a plan view and a front view, respectively, schematically illustrating the relationship between the rotation constraint portion of the tool holder of the automatic tool changer of the present invention and the phase at which the male thread starts to be cut. [Figure 2] 10 is a diagram for explaining the distance between the upper end surface of the tool holder on the side fastened to the support horn of the tool holder of the automatic tool changer of the present invention and the reference position in the Z-axis direction. FIG. [Figure 3] 1A is a plan view of a tool magazine, FIG. 1B is a plan view of a fitting portion, and FIG. 1C is a front view of the fitting portion of an ultrasonic vibration machining device according to the present invention. [Figure 4] 1 is a cross-sectional view of an ultrasonic spindle unit of an ultrasonic vibration machining apparatus according to the present invention; [Figure 5] 2 is a block diagram of a control device for controlling an automatic tool changer of the ultrasonic vibration machining apparatus of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 and 2 are also used to explain the problems to be solved in the prior art, and the same drawings will be used in the description of the embodiment of the present invention. In each figure, the same or corresponding parts are assigned the same reference numerals.

[0023] In Figure 1, tool holders T (T1, T2) each have a tool t1 or t2 fixed to one side (the workpiece side, not shown) of a tool holder body 3, and a male threaded portion 4 on the other side (the horn portion 1 side), and at least two opposing rotation constraint portions Tb (T1b, T2b) are provided on the side of the tool holder body 3. The two surfaces of the rotation constraint portion Tb are parallel to each other.

[0024] 3 shows a tool magazine 5 that stores and holds a plurality of tool holders T (T1, T2, ...). The tool magazine 5 has a fitting portion 2 on its circumference into which the rotation constraint portions Tb on two surfaces of the tool holder T are fitted, and the uppermost end of the rotation constraint portion Tb of the tool holder T that engages with the fitting portion 2 is the Z-axis reference position Td. A plunger 6 is provided on the fitting surface 2a of the fitting portion 2 that joins with the rotation constraint portion Tb of the tool holder T, and when the tool holder T is fitted into the fitting portion 2 at the correct fitting position, the plunger 6 engages with the recess Tb' of the rotation constraint portion Tb, thereby positioning the tool holder T.

[0025] 4 is a cross-sectional view of an ultrasonic spindle unit 10 of an ultrasonic vibration machining device according to the present invention. The ultrasonic spindle unit 10 includes a hollow cylindrical spindle head 11, a spindle 13 rotatably supported by a spindle motor 14 connected to the rear end of the spindle 13 via a bearing 12 inside the spindle head 11. The spindle 13 has a through-hole 15 passing through its axis. A horn 1 is fixed to the tip of the through-hole 15, and an ultrasonic vibrator 16 is fixed to the rear end of the horn 1 to transmit ultrasonic vibrations to the horn 1. A piezoelectric element 17 is mounted in the middle of the ultrasonic vibrator 16.

[0026] A rotary connector 18 is installed on the outer periphery of the rear end of the spindle 13, and the rotary connector 18 consists of a rotor 19 fitted onto the outer periphery of the spindle 13 and a power supply unit 20 that is non-rotatingly arranged on the spindle head 11 side. Power is supplied to the rotor 19 when a fixed brush 20a of the power supply unit 20 comes into contact with the rotor 19. Wiring 21 extending from below the rotor 19 is connected to the piezoelectric element 17 via the vibrator wiring plate 17a, and power is supplied to the entire ultrasonic vibrator 16.

[0027] Figure 5 is a schematic block diagram of a control device 30 that controls the automatic tool changer. 31 is the main CPU of the control device. 32 is ROM, 33 is RAM, and 34 is non-volatile memory. 35 is a PMC (programmable machine controller) that controls the rotation and Z-axis movement of the spindle 13. 36 is a display device, 37 is a keyboard for inputting a phase setting value Rx and a Z-axis correction value Sx (described later), 38 is a display device control circuit, and 39 is an NC program for automatic tool change.

[0028] Here, the phase setting value Rx displayed on the display device 36 will be described. When exchanging tool holder T between tool holder T and spindle 13, that is, when the male thread portion 4 of tool holder T starts to be fastened to the female thread portion 1a of the horn portion 1, the phase of the spindle 13 is determined so that the rotation constraint portion Tb of tool holder T is parallel to the fitting surface 2a of the fitting portion 2 of the tool magazine 5. The phase of the spindle 13 at this time is called the spindle orientation completion position R0. For example, the start of thread cutting T2a of tool holder T2 in Figure 1 begins at the spindle orientation completion position R0. In this case, the phase of the spindle 13 (horn portion 1) when the screw fastening starts is determined to be the spindle orientation completion position R0. The phase setting value Rx is R0 (the standard phase setting value is 0°).

[0029] However, with the tool holder T1 in Fig. 1, the thread cutting start point T1a is shifted in phase by θ° from the spindle orientation completion position R0, so the phase of the spindle 13 (horn part 1) when the screw fastening starts must be aligned with the thread cutting start point T1a. The phase setting value Rx displayed on the display screen 36 is the angle θ° from the spindle orientation completion position R0 to the thread cutting start point T1a.

[0030] Next, the Z-axis correction value Sx displayed on the display device 36 will be described. Because the pitch and lead of the screw are constant for all tool holders T, the screw tightening Z-axis movement amount H of the spindle 13 from the start of screw tightening to the completion of screw tightening remains the same for all tool holders T (see Figure 2). Therefore, the Z-axis position of the tip surface 1b of the horn 1 at the start of screw tightening (the Z-axis position of the spindle 13 at the start of screw tightening) is determined to be a position set off in the positive direction of the Z-axis by the screw tightening Z-axis movement amount H from the Z-axis position of the top end surface Tc, which varies for each tool holder T.

[0031] 2 is a reference line indicating the dimension (distance in the Z-axis direction) between the Z-axis reference position Td of the rotation constraint portion Tb that engages with the fitting portion 2 indicated on the drawing and the upper end face Tc of the tool holder. It is desirable that all tool holders T be manufactured according to the dimensions indicated on the drawing, but since differences of several tens to several hundreds of microns occur between each tool holder, the difference in distance in the Z-axis direction from this reference line Th is used as a Z-axis correction value Sx, and the Z-axis position of the upper end face Tc of each tool holder is corrected, thereby determining the Z-axis position of the spindle 13 at the start of screw tightening.

[0032] The phase setting value Rx and Z-axis offset value Sx determined for each tool in this way are entered using the keyboard 37. These entered setting values ​​are stored in non-volatile memory. The PMC 35 reads the phase setting value Rx and Z-axis offset value Sx of the tool Tx to be replaced from memory and transfers these setting values ​​to the NC program 39. The NC program 39 uses the transferred setting values ​​to send Z-axis and spindle positioning commands to the main CPU 31. The main CPU 31 reads the commands from the NC program 39, calculates the phase and Z-axis position of the spindle 13, and sends positioning commands to the Z-axis servo amplifier 40 and spindle amplifier 41. The Z-axis servo amplifier 40 and spindle amplifier 41 control the Z-axis servo motor 42 and spindle motor 14 to position the spindle 13 to the phase and Z-axis position at the start of screw tightening.

[0033] The tool magazine 5 indexes the fitting portion 2, which holds the next tool holder T to be used, to the automatic tool change position P0. The spindle 13 is positioned to the phase and Z-axis position at the start of screw tightening using the phase setting value and Z-axis offset value corresponding to the indexed tool holder T. The spindle 13 then moves forward while rotating according to a predetermined spindle angle (the angle at which the spindle 13 must rotate before the female and male threads are tightened) and Z-axis travel amount, completing the tightening of the female threads of the horn portion 1 and the male threads of the tool holder T. Note that this predetermined spindle angle and Z-axis travel amount are set so that optimal torque can be obtained when the screw tightening is complete.

[0034] In this way, by storing the phase setting value Rx and Z-axis compensation value Sx for each tool holder T in advance in the control device, the spindle 13 can obtain the optimal fastening torque simply by rotating and advancing at a predetermined spindle angle and Z-axis movement amount, without being affected by individual differences between tool holders T.

[0035] The present invention is not limited to the above-described embodiment. For example, a male thread may be provided on the horn portion 1 and a female thread may be provided on the tool holder, and the spindle angle may be adjusted using the phase at which the female thread of the tool holder starts to cut the thread as the phase setting value.

[0036] Furthermore, by periodically measuring the Z-axis correction value, it is possible to address thermal displacement of the spindle or machine caused by the ultrasonic vibrator.

[0037] Furthermore, the tool magazine is not limited to a disk-shaped one, and may be a tool exchange arm having a fitting portion that restrains the rotation restraint portion of the tool holder, and the concept includes such. [Explanation of symbols]

[0038] 1 Horn part, 1a Female thread part 2 mating portion, 2a mating surface 3 Tool holder body 4 Male thread 5 Tool Magazine 10 Ultrasonic spindle unit 11 Spindle head 13 Spindle 14 Spindle motor 16 Ultrasonic transducer 17 Piezoelectric element 18 Rotating Connector 19 Rotating body, 20 Power supply unit, 20a Fixed brush 30 Control device T(T1, T2...) Tool holder Ta (T1a, T2a...) Beginning of thread cutting Tb Rotation restriction part Tc (T1, T2...) top surface Td Z-axis reference position Th Tool holter top surface Z-axis reference position P0 automatic tool change position R0 Spindle orientation completion position Rx phase setting value Sx Z-axis correction value

Claims

1. The automatic tool changer for ultrasonic vibration machining equipment is a holder body to which a tool is fixed; and a plurality of tool holders, each of which has parallel rotation constraint portions on at least two sides and a male or female thread portion on the side opposite to the tool; a spindle that has a hollow interior, a horn portion having a female or male screw portion, an ultrasonic vibrator that applies ultrasonic vibrations to the horn portion, a piezoelectric element that is sandwiched in the middle of the ultrasonic vibrator, and a rotary connector that shares a power source with the piezoelectric element via wiring, and that can be rotated by a spindle motor; a Z-axis motor that moves the spindle in the Z-axis direction; a fitting portion of a tool magazine that fits into the rotation constraint portion of the tool holder to grip the tool holder; a control device that controls the operation of the spindle so that the female or male thread portion of the horn portion and the male or female thread portion of the tool holder are fastened or unfastened to each other by rotating and advancing or retracting the spindle in accordance with a predetermined spindle angle and Z-axis movement amount, thereby enabling the tool holder to be detachably replaced on the spindle, an automatic tool changer for an ultrasonic vibration machining device, characterized in that a phase setting value is input to a display device of the control device and stored in a memory for each tool holder, and when changing a tool, the phase setting value of the tool holder to be changed is read out, the phase of the spindle at the start of screwing is calculated, and a command is sent to the spindle motor to control the phase of the spindle.

2. 2. The automatic tool changer for an ultrasonic vibration machining apparatus according to claim 1, wherein a Z-axis compensation value is input to a display device of the control device and stored in a memory for each tool holder, and when changing a tool, the Z-axis compensation value of the tool holder for tool change is read out, a Z-axis position at the start of screwing is calculated, and a command is sent to the Z-axis motor to control the Z-axis position of the spindle.

3. The phase setting value is:

2. The automatic tool changer for an ultrasonic vibration machining apparatus according to claim 1, wherein the angular difference is between a reference phase for tool change of the spindle in which the fitting portion and the rotation constraint portion are parallel to each other, and a phase in which thread cutting of the male or female thread portion of the tool holder begins.

4. The Z-axis correction value is 4. The automatic tool changer for an ultrasonic vibration machining apparatus according to claim 2 or 3, wherein the difference is a distance between a Z-axis reference position of the rotation restraint portion fitted into the fitting portion and the Z-axis reference position of the upper end surface of the tool holder, and a difference between the Z-axis reference position of the rotation restraint portion fitted into the fitting portion and the actual Z-axis position of the upper end surface of the tool holder.

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