Method for automatically holding a machining tool in a machining device

Abstract

To provide a drill holding method capable of reducing inclination and deviation which may occur between an axis of a drill with a ring mounted on a tool post and an axis of a spindle (collet chuck).SOLUTION: After a spindle is lowered until a machining tool 7 with a ring mounted on a tool post 9 having a spring 93 for energizing a mounted object upward is pushed in by a predetermined amount by a collet chuck, while the spindle is raised, the machining tool is held by the collet chuck until a lower end surface of the collet chuck is raised by an amount equal to the predetermined amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for automatically holding a processing tool such as a drill in a drilling device, and more particularly to a method for holding a processing tool with a ring via a tool post. [Background technology]

[0002] In some drilling machines, as disclosed in Patent Documents 1 and 2, for example, a drill with a ring held by a spindle is replaced via a tool post. In such machines, when a drill is held by the spindle, the lower end surface of a collet chuck provided on the spindle for holding the drill needs to be in contact with the upper end surface of the ring. Therefore, the drill is placed on a tool post with a spring inside, the collet chuck presses the drill a predetermined amount, and the restoring force of the spring holds the drill in a state where both end surfaces are in contact with each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4840897 [Patent Document 2] Patent No. 5238579 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the collet chuck is closed in the pressed-in state, the spring force is applied as a load via the ring to the tips of the holding pieces separated by the slits in the collet chuck, so if there are minute irregularities on the top end surface of the ring, the holding pieces cannot be closed evenly, and the drill axis may be held in a state where it is shifted or tilted in the direction parallel to the spindle axis. In such cases, the tip of the drill may wobble during machining, causing the problem of unstable machining accuracy.

[0005] In addition, in order to solve this problem, Patent Document 2 discloses a technology in which the tool post is provided with two springs with different spring constants, and only the spring with the small spring constant is bent when the collet chuck is closed, thereby reducing the load applied to the tip of each holding piece and holding both axes coaxially. However, when a tool post with two springs with different spring constants is used, the spring with the small spring constant may be erroneously restored due to cuttings or the like that have entered the tool post, and the drill may be tilted when placed on the tool post. In such a case, the axial deviation after holding becomes larger, and the position of the opening of the collet chuck into which the drill is inserted is misaligned with the position of the end of the shank side of the drill, which is not necessarily appropriate, and therefore the drill and the spindle may collide during the replacement operation.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a method for holding a machining tool with a ring, which solves the above-mentioned problems and makes it easier to make the axis of the drill coaxial with the axis of the spindle. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention provides a method for holding a machining tool placed on a tool post in a machining apparatus having a spindle with a holding part for holding a machining tool having a ring attached thereto, and a tool post for mounting the machining tool held on the holding part of the spindle, the tool post having an elastic body for biasing the mounted machining tool upward when the machining tool is pushed downward, the method comprising: a pushing step for lowering the spindle until the holding part pushes the machining tool placed on the tool post a predetermined amount; and a holding step for the holding part to hold the machining tool while raising the spindle after the pushing step, wherein in the holding step, the holding part holds the machining tool until the lower end surface of the holding part rises an amount equal to the predetermined amount. Effect of the Invention

[0008] According to the present invention, the inclination of the axis of the drill relative to the axis of the spindle can be reduced and maintained, so that wobble of the tip of the drill can be reduced and machining precision can be stabilized. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a drilling device according to an embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view of a spindle tip of a drilling device according to an embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view of a feed tool post of a drilling apparatus according to one embodiment of the present invention; [Figure 4] FIG. 13 is a diagram showing a variation in the position of the lower end surface of a collet chuck during a drill holding operation according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a drilling machine according to an embodiment of the present invention. In FIG. 1, a printed circuit board 3, which is a workpiece, is placed on a machine base 1, which is a base, and a machining table 2, which is driven in the X direction, is provided. A cross slide 5, which is driven in the Y direction, is provided on a gate-type column 4 attached to the machine base 1. A spindle 6, which is driven in the Z direction, is provided on the cross slide 5. The spindle 6 is provided with a collet chuck (not shown) which will be described later, and the collet chuck holds a drill 7. Reference numeral 12 denotes a sub-chuck unit attached to the spindle 6 and moves in the Z direction together with the spindle 6. The machining table 2, the cross slide 5, and the spindle 6 are provided with drive units (not shown) and are driven in their respective directions.

[0011] Reference numerals 9, 10, and 11 denote a supply tool post, a discharge tool post, and a drill cassette in which new drills and old drills are stored separately, respectively, and are installed on the processing table 2 near the printed circuit board 3 to be processed. The sub-chuck unit 12 can hold a drill at its lower end, and moves the drill 7 between the drill cassette 11 and the supply tool post 9 or the discharge tool post 10. Reference numeral 20 denotes an overall control unit that controls each part of the drill processing device. The overall control unit 20 is configured, for example, mainly with a program-controlled processing device, and controls the drive parts of the processing table 2 and the cross slide 5 based on feed position information from the drive parts of the processing table 2 and the cross slide 5. In addition, the overall control unit 20 controls the drive parts while recognizing the current height position of the lower end surface in the open state of the collet chuck based on feed position information from the drive part of the spindle 6 during the processing tool holding operation. Furthermore, the overall control unit 20 has a memory unit that stores position information of each height, which will be described later, and also has control functions other than those described here.

[0012] FIG. 2 is a cross-sectional view of the tip of the spindle, FIG. 2(A) shows a state in which the spindle 6 holds the drill 7, and FIG. 2(B) shows a state in which the spindle 6 releases the drill 7. As shown in FIG. 2(A), the spindle 6 has a rotor shaft 61 that rotates the drill 7, and at its tip are disposed a collet chuck 81 that serves as a drill holder and a spring 82 that elastically biases the collet chuck 81 upward in the figure. The spindle 6, the rotor shaft 61, and the collet chuck 81 are disposed in a coaxial position. On the drill 7 side of the collet chuck 81, a plurality of slits (not shown) are formed in the direction of the axis of rotation O, and the diameter can be reduced in the radial direction. The drill 7 is held by a radial force generated when a tapered surface 81a formed on the outer periphery of the collet chuck 81 is biased by the spring 82 against a tapered surface 61a formed on the inner surface of the rotor shaft 61.

[0013] 2(B), when a cylinder (not shown) is operated to lower piston rod 83 connected to the cylinder and move collet chuck 81 downward in the figure against spring 82, tapered surface 81a of collet chuck 81 separates from tapered surface 61a of rotor shaft 61, and collet chuck 81 enters an open state. Note that when collet chuck 81 is in the open state, the position of bottom end surface 81d of collet chuck 81 is located at a position protruding downward a predetermined amount J (hereinafter referred to as protrusion amount J) from the position in the state of FIG. 2(A) in which collet chuck 81 is closed while holding drill 7.

[0014] When the drill 7 placed on the supply tool post 9 is held, the collet chuck 81 is pulled into the rotor shaft 61 from the open state shown in FIG. 2B to the closed state shown in FIG. 2A. Specifically, the cylinder is operated to raise the piston rod 83. Then, the collet chuck 81 is pulled into the spindle 6 and rises in accordance with the rise of the piston rod 83 due to the restoring force of the spring 82. Then, the drill 7 placed on the supply tool post 9 is urged upward in a state where it is pushed in by a predetermined amount as described later, so that the lower end surface 81d of the collet chuck 81 and the upper end surface 71u of the ring 71 are in contact with each other, and the drill 7 is pulled into the spindle 6 together with the collet chuck 81 and rises, and is held as shown in FIG. 2A.

[0015] Returning to FIG. 2(A), a ring 71 is attached to the drill 7. The ring 71 is made of, for example, a hard synthetic resin. A through hole having a diameter slightly smaller than the outer diameter of the shank of the drill 7 is formed in the center of the ring 71, and the ring 71, with the shank inserted into the through hole, is integrated with the drill 7 due to its elasticity. The ring 71 is fixed to the drill 7 such that the distance from its upper surface to the tip 7p of the drill 7 is a distance K. The lower end surface 81d of the collet chuck 81 is brought into contact with the ring upper end surface 71u, so that the drill tip 7p is accurately positioned at the distance K from the lower end surface 81d of the collet chuck 81.

[0016] 3A is a cross-sectional view of the supply tool post 9 of a drilling device according to one embodiment of the present invention, and FIG. 3B is a cross-sectional view of the supply tool post 9 with a drill 7 placed thereon. The supply tool post 9 according to the present invention is composed of a sleeve 91, a holder 92, and a spring 93.

[0017] A hole is formed inside the sleeve 91, which is made up of a small diameter portion 91a that opens to the upper end side in the axial direction and a large diameter portion 91b that is coaxially connected to the end of the small diameter portion 91a and has a larger diameter than the small diameter portion. The holder 92 is formed with a large diameter portion slightly smaller in diameter than the large diameter portion 91b of the sleeve, a small diameter portion slightly smaller in diameter than the small diameter portion 91a of the sleeve, and a tapered portion connecting both portions. The tapered portion of the holder 92 abuts against a step provided between the small diameter portion 91a and the large diameter portion 91b of the sleeve, thereby restricting the holder 92 from moving upward. The holder 92 is formed with a first hole 92a having an inner diameter that opens upward and fits the ring 71, a second hole 92b that is coaxially connected to the first hole 92a and has a smaller diameter than the first hole 92a and a larger diameter than the outer diameter of the shank of the drill 7, and a third hole 92c that is coaxially connected to the second hole 92b and opens to the other end. In the small diameter portion of the holder 92, a plurality of radial slits 92d are formed that penetrate parts of the first hole 92a and the second hole 92b.

[0018] A spring 93 arranged in a compressed state between the processing table 2 and the holder 92 urges the holder 92 upward. That is, when the tapered portion of the holder 92 abuts against the step between the large diameter portion and the small diameter portion of the sleeve 91, the spring 93 is simply held in a compressed state at a predetermined height position of the sleeve 91, but when the holder 92 is pressed in, the spring 93 is further compressed, and in this state the spring 93 urges the holder 92 upward.

[0019] As shown in FIG. 3B, when the drill 7 is placed on the supply tool post 9, the lower end surface of the ring 71 of the drill 7 is placed so as to contact the bottom surface of the first hole 92a. Since the vertical height of the ring 71 and the height of the bottom surface of the first hole 92a are fixed, the height position of the upper end surface 71u of the ring 71 when the drill 7 is placed on the tool post 9 is determined as I. The height position information of the ring upper end surface 71u in this state is stored in the storage unit of the overall control unit 20. Note that since the ring 71 is made of resin, there is some variation in the height accuracy. In addition, since the tool post 9 is composed of multiple parts such as the spring 93 and the holder 92, there is some variation in the height position of the bottom surface of the first hole 92a. Therefore, taking these variations into consideration, the lowest possible height position I is stored as the height position information.

[0020] Fig. 4 is a diagram showing a change in position of the lower end surface 81d of the collet chuck 81 during a drill holding operation. The machining tool holding operation according to the present invention will be described with reference to Fig. 4. In the following description, it is assumed that the collet chuck 81 is not holding the drill 7, and that the drill 7 held by the collet chuck 81 has been moved in advance from the drill box 11 by the sub-chuck unit 12 and is placed on the supply tool post 9.

[0021] The drilling device operates as follows under the control of the overall control unit 20. During operation, the overall control unit 20 recognizes and controls the current position of the collet chuck lower end surface 81d when the collet chuck 81 is open. First, the axis of the spindle 6 (and the collet chuck 81) is moved to a position coaxial with the axis of the drill 7 placed on the supply tool post 9, and the spindle 6 starts to descend with the collet chuck 81 open (T1). When the lower end surface 81d of the collet chuck 81 descends to a position a predetermined distance above the ring upper end surface 71u of the drill 7 placed on the supply tool post 9, the descending speed is decelerated (T2). This predetermined upward position is a position where a necessary amount can be secured to prevent impact when the collet chuck lower end surface 81d comes into contact with the ring upper end surface 71u, and the height position information is stored in advance in the storage unit of the overall control unit 20. Thereafter, when the collet chuck lower end surface 81d descends to a position equal to the height I of the ring upper end surface 71u (T3), it descends further from that position by a predetermined amount P (hereinafter referred to as the push-in amount P) and stops descending (T4). As a result, the drill 7 is pressed into the supply tool post 9. Note that the push-in amount P is set to be equal to or greater than the retraction movement amount Q described below. The position of the collet chuck lower end surface 81d at T4 will be referred to as the push-in position hereinafter.

[0022] At T4, the spindle 6 immediately after stopping its descent rises while keeping the collet chuck 81 open. Then, when the collet chuck lower end surface 81d reaches a position where the collet chuck 81 completes retracting (holding) the drill 7 before rising by the pushing amount P (hereinafter referred to as the retraction start position), the collet chuck 81 starts retracting (T5).

[0023] The retraction start position is obtained in advance by an experiment or the like as follows, and stored in the memory of the overall control unit 20. First, the time Th from when the collet chuck 81 starts retracting to when it completes retracting (hereinafter referred to as retraction time Th) is obtained from the protruding amount J of the collet chuck and the retraction speed of the collet chuck 81. Next, the amount by which the collet chuck lower end surface 81d rises during the retraction time Th (hereinafter referred to as retraction movement amount Q). The collet chuck lower end surface 81d rises during the retraction time Th by the total amount of the rise caused by the spindle and the rise amount of the collet chuck itself due to retraction. Therefore, the total amount of the rise caused by the spindle during the retraction time Th, which is obtained from the spindle's rising speed and the retraction time Th, and the rise amount due to retraction, i.e., the protruding amount J of the collet chuck 81, becomes the retraction movement amount Q. Then, the retraction start position is determined to be the height position obtained by subtracting the retraction movement amount Q from the height position I of the ring upper end surface. By setting the retraction start position in this way, the biasing force of the spring 93 can be obtained until the retraction (holding) of the drill 7 by the collet chuck 81 is completed.

[0024] When the retraction by the collet chuck 81 is completed (T6), the spindle 6 accelerates and rises to a predetermined processing standby position (T7).

[0025] In the present invention, the spindle 6 holds the drill 7 while rising, instead of stopping at the position where the spindle 6 pushed in the drill 7 as in the conventional case. When the spindle 6 rises after the drill 7 placed on the tool post 9 is pushed in, the movable members constituting the tool post 9 come into contact with each other as the spring 93 returns to its original position, and extremely small vibrations are generated due to friction at that time. Furthermore, extremely small vibrations are also generated due to the driving operation when the spindle 6 moves upward. If the collet chuck 81 performs a retraction operation while the spindle 6 is rising, these extremely small vibrations make it difficult for the ring 71 to engage with the chuck claws even if the ring surface is uneven. In addition, as the spindle 6 rises, the contact pressure between the ring 71 and the collet chuck 81 may decrease, making it easier for all the holding pieces to move uniformly toward the axis of the spindle 6. This reduces the deviation between the axis of the drill 7 and the axis of the spindle 6.

[0026] In this embodiment, the timing of the start of retraction is set to the timing when the position of the lower end surface 81d in the open state of the collet chuck 81 rises from the pushed-in position and reaches the retraction start position. However, the present invention is not limited to this, and may be set to, for example, the timing when a predetermined time has elapsed from the time point (T4) when the rise starts. In this case, the predetermined time can be calculated based on the amount obtained by subtracting the retraction movement amount Q from the push-in amount P and the rising speed of the spindle.

[0027] As described above, according to the present invention, all of the holding pieces of the collet chuck can easily move uniformly toward the axis of the spindle while the lower end surface of the collet chuck and the upper end surface of the ring are in contact with each other, thereby reducing the inclination between the axis of the spindle and the axis of the machining tool. [Explanation of symbols]

[0028] 1: device base, 2: processing table, 3: printed circuit board (workpiece), 4: gate-type column, 5: cross slide, 6: spindle, 61: rotor shaft, 61a: tapered surface, 7: drill (processing tool), 71: ring, 71u: upper end surface, 7p: tip, 81: collet chuck (holding part), 81a: tapered surface, 81d: lower end surface, 82: spring, 83: piston rod, 9: supply tool post, 91: sleeve, 91a: small diameter part, 91b: large diameter part, 92: holder, 92a: first hole, 92b: second hole, 92c: third hole, 92d: slit, 93: spring, 10: discharge tool post, 11: drill cassette, 12: sub-chuck unit, 20: overall control unit

Claims

[Claim 1] A method for holding a machining tool mounted on a tool post in a processing device having a spindle including a holding portion for holding a machining tool having a ring attached thereto, and a tool post for mounting the machining tool held by the holding portion of the spindle, the tool post including an elastic body for urging the machining tool upward when the mounted machining tool is pushed downward, the method comprising: a pushing step of lowering the spindle until the machining tool placed on the tool post is pushed in by the holding portion by a predetermined amount; A holding step in which the holding part holds the processing tool while raising the spindle after the pushing step, In the holding step, the holding portion holds the processing tool until the lower end surface of the holding portion rises by an amount equal to the predetermined amount. A method for holding a processing tool, comprising:

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