Drill bit processing equipment

Abstract

This invention provides a drill bit processing apparatus with high drilling accuracy. The drill bit processing apparatus includes a workpiece-carrying table, a spindle, a pressure foot, and a cylinder supporting the pressure foot for relative movement relative to the spindle. The cylinder includes: a cylinder (61) supplied with compressed air, a piston (71) connected to the pressure foot and sliding within the cylinder, and a pressure-reducing mechanism (64, 78, 77) for reducing the pressure within the cylinder. The pressure-reducing mechanism is configured to reduce the pressure within the cylinder based on a predetermined amount of cylinder contraction, the predetermined amount being greater than or equal to the amount of spindle descent before the drill bit penetrates the workpiece after the pressure foot contacts it.

Description

Drill processing device The present invention relates to a drill processing device that uses a drill to process a workpiece. Conventionally, there has been proposed a drill processing device that rotates a drill at high speed by means of a spindle provided with an air bearing, presses a printed circuit board with a pressure foot, and at the same time performs drilling processing with this high-speed rotating drill (see Patent Document 1). [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2016-040055. If the printed circuit board is pressed with a pressure foot and drilling is performed simultaneously in this way, problems such as warping and misalignment of the printed circuit board during drilling can be suppressed, and the quality of the drilling process can be improved. However, conventionally, the pressure foot continuously presses the printed circuit board with the same pressure as when the drill penetrates into the printed circuit board until the drilling is completed. Therefore, sometimes the substrate extends, resulting in a difference in hole position accuracy between the initial stage and the final stage of processing. In view of this, an object of the present invention is to provide a drill processing device with higher drilling accuracy. One aspect of the present invention is a drill processing device, comprising: a processing table on which a workpiece is placed; a spindle that holds a drill so that it can rotate at high speed; a pressure foot located below the spindle that presses the workpiece onto the processing table; a cylinder that supports the pressure foot so that it can move relative to the spindle, the cylinder having: a cylinder to which compressed air is supplied; a piston that is connected to the pressure foot and slides in the cylinder; a pressure reducing mechanism that reduces the pressure in the cylinder, the pressure reducing mechanism being configured to reduce the pressure in the cylinder based on a specified amount of contraction of the cylinder, the specified amount being greater than or equal to the amount of descent of the spindle from when the pressure foot abuts against the workpiece until the drill penetrates into the workpiece. According to the present invention, a drill processing device with higher drilling accuracy can be provided. Hereinafter, the drill processing device according to the embodiment of the present invention will be described with reference to the drawings. In the following description, the X-axis direction and the Y-axis direction refer to directions that are orthogonal to each other with the state of observing the workpiece in a top view as a reference, and the Z-axis direction refers to a direction orthogonal to these X-axis direction and Y-axis direction. For example, in FIG. 1, the X-axis direction is the left-right direction of the drawing, the Y-axis direction is the depth direction of the drawing, and the Z-axis direction is the up-down direction of the drawing. [General structure of the drill processing device] First, the general structure of the drill processing device 1 will be described with reference to FIG. 1. As shown in FIG. 1, the drill processing device 1 according to the present embodiment includes: a processing table 2 that is provided so as to be movable along the X-axis on a device base (not shown); a spindle unit 3; a pressure foot 5, and a workpiece (a printed circuit board in this embodiment) W to be drilled is placed on the processing table 2. The spindle unit 3 includes: a spindle 3a that rotatably holds a drill bit 4; and a bracket 3b that holds the spindle 3a. The spindle unit 3 is supported via a cross slide and a saddle (not shown) so as to be movable in the Y-axis direction and the Z-axis direction. More specifically, the spindle 3a includes: a rotating shaft that has a collet chuck for mounting the drill bit 4 at its end; an air bearing that rotatably supports the rotating shaft; and a motor that rotates the rotating shaft. The air bearing radially supports the rotating shaft through a radial air bearing and axially supports the rotating shaft through a thrust air bearing. The motor is composed of a rotor and a stator. The rotor is formed on the rotating shaft, and the stator is disposed at a position opposite to the rotor. Thus, through these rotating shaft, air bearing, and motor, the spindle 3 holds the drill bit 4 so as to be capable of high-speed rotation. In addition, a presser foot 5 for pressing the workpiece W during hole machining is engaged with the lower side of the spindle 3a. The presser foot 5 is supported by a pair of left and right cylinders 6, 6 so as to be relatively movable with respect to the spindle 3a, and these cylinders 6, 6 are supported by a bracket portion 31b of the bracket 3b. Therefore, when the spindle unit 3 descends in the Z-axis direction, the presser foot 5 also descends in the Z-axis direction together with the spindle unit 3. When the spindle unit 3 descends to a specified height position, as shown in Fig. 1, before the drill bit 4 supported by the spindle 3a, the presser foot 5 comes into contact with the surface of the workpiece W first. Compressed air at a constant pressure is always supplied from a compressor 7, which is an air supply mechanism, to the cylinders 6, 6 to press the presser foot 5 downward. Thus, in a state where the lower surface of the presser foot 5 contacts and presses the surface of the workpiece W, if the spindle unit 3 is further lowered, the cylinders 6, 6 contract, the position of the presser foot 5 remains unchanged, and only the spindle unit 3 descends. Then, as shown in Fig. 2, the drill bit 4 supported by the spindle 3a penetrates into the workpiece W to drill the workpiece W. When the drilling is completed and the spindle unit 3 ascends, from a certain position, the presser foot 5 also ascends together with the spindle unit 3. [Structure of the cylinder] Next, the structure of the cylinders 6, 6 will be described in detail. Fig. 3 is a view showing the state of the cylinder 6 of the drill machining apparatus 1 in Fig. 1. As shown in Fig. 3, the cylinder 6 is configured to include a cylinder 61 and a piston 71 that slides in the cylinder. In the cylinder 6, the inner peripheral surface 62 of the cylinder 61 and the outer peripheral surface 72 of the piston 71 are sealed, and a cylinder chamber 63 is formed on the side of the piston 71 opposite to the rod portion 73. An air port for supplying compressed air and for exhausting is formed in the cylinder chamber 63. By supplying compressed air from the compressor 7 to the cylinder chamber 63, the internal pressure of the cylinder chamber 63 becomes high, and a downward pressing force is generated on the piston 71. In addition, in the present embodiment, the piston 71 includes a rod portion 73 connected to the above-mentioned presser foot 5 and a piston portion 74 that slides within the cylinder 61. The piston portion 74 is a hollow cylindrical shape and includes: a bottom portion 75 to which the rod portion 73 is attached; a peripheral wall portion 76 that forms an outer peripheral surface that slides against the inner peripheral surface 62 of the cylinder 61. The piston portion 74 is formed to open into the cylinder chamber 63 on the side opposite to the axial direction (sliding direction) of the bottom portion 75. Further, an opening portion 78 that allows the inside and outside of the internal space 77 of the piston portion 74 to communicate is provided in the above-mentioned peripheral wall portion 76. Further, at a specified height position on the peripheral wall portion of the cylinder block 65 that forms the inner peripheral surface 62 of the above-mentioned cylinder 61, an opening portion 64 that communicates the inside and outside of the cylinder 61 is formed. The opening portion 64 of the cylinder 61 and the opening portion 78 of the piston 71 constitute a decompression mechanism that decompresses the inside of the air cylinder 6 to reduce the pressing force of the presser foot 5. More specifically, it is configured such that the opening portion 64 of the above-mentioned cylinder 61 and the opening portion 78 of the piston 71 are provided at corresponding positions in the circumferential direction. At the maximum extrusion position of the piston 71 in Figure 3, the opening portion 64 is closed by the outer peripheral surface of the piston 71, and the opening portion 78 is closed by the inner peripheral surface of the cylinder 61, so that these opening portions 64 and 78 are not in communication. In this state, the compressed air supplied from the compressor 7 does not escape to the outside through the opening portions 78 and 64, so the internal pressure of the cylinder chamber 63 is not decompressed through the opening portions 78 and 64, and the pressing force of the air cylinder 6 reaches the maximum at the maximum extrusion position of the piston 71. Then, the air cylinder 6 descends together with the spindle unit 3 in the state of this maximum extrusion position until the presser foot 5 contacts the workpiece W. In addition, at this maximum extrusion position, a specified distance t is provided between the upper end position of the opening portion 78 of the piston 71 and the lower end position of the opening portion 64 of the cylinder 61. Within the contraction range of this distance t, the opening portion 64 of the above-mentioned cylinder 61 and the opening portion 78 of the piston 71 are not in communication, and the pressing force of the air cylinder 6 is maintained at the maximum value. In the present embodiment, this distance t is at least set to be greater than or equal to the descending distance of the spindle 3a from when the presser foot 5 contacts the workpiece W until the tip of the drill 4 penetrates into the workpiece W. Therefore, at least when the drill 4 penetrates into the workpiece W, the workpiece W is pressed by the presser foot 5 with the maximum pressing force. In addition, when the drill 4 penetrates into the workpiece W to perform drilling and becomes the state shown in Figure 2 above, the contraction amount of the piston 71 reaches more than the above-mentioned distance t. As shown in Figure 4, the opening portion 64 of the cylinder 61 and the opening portion 78 of the piston 71 are in communication. If these opening portions 64 of the cylinder 61 and the opening portion 78 of the piston 71 are in communication, the compressed air CA in the cylinder chamber escapes to the outside of the cylinder through the opening portions 78 and 64, thereby being decompressed, and the pressing force of the presser foot 5 on the workpiece W becomes smaller. Thus, in the present embodiment, the opening 64 of the cylinder 61, the opening 78 of the piston 71, and the internal space 77 each become exhaust holes, and a decompression mechanism is constituted by these exhaust holes. The decompression mechanism reduces the pressure in the cylinder when the contraction of the cylinder 6 reaches a specified amount t. The above-mentioned specified amount t is greater than or equal to the descending amount of the main shaft 3a until the drill bit 4 penetrates into the workpiece W after the pressure foot 5 abuts against the workpiece W. Therefore, at least until the drill bit 4 penetrates into the workpiece W, the pressing force for pressing the workpiece by the cylinder 6 via the pressure foot 5 is maintained at the maximum pressing force. Thus, even when the drill bit 4 penetrates, at which time the workpiece is most likely to become unstable, the workpiece W can be stably pressed by the pressure foot 5. In addition, starting from the time when the drill bit 4 penetrates, as the drilling progresses, the descending amount of the main shaft 3a becomes larger, the above-mentioned exhaust holes communicate, the cylinder 6 is decompressed, and the force for pressing the workpiece W by the pressure foot 5 becomes smaller. Thus, during drilling, it is possible to prevent pressing the workpiece W with the maximum pressing force all the time, thereby preventing problems such as differences in the hole opening position accuracy at the initial and final stages of processing due to the extension of a workpiece such as a printed circuit board. In the drill processing apparatus 1 according to the present embodiment, as described above, when the drill bit 4 penetrates into the workpiece W, the workpiece W is pressed with the maximum pressing force by the pressure foot 5, and thereafter, the pressing force of the workpiece W is reduced, thereby preventing problems such as the extension of a workpiece such as a printed circuit board, and enabling the workpiece to be drilled with high precision. The present invention has been described with reference to exemplary embodiments, but it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the following patent application should be given the broadest interpretation, including all similar modifications and equivalent structures and functions. 1: Drill processing apparatus 2: Processing table 3: Spindle unit 3a: Spindle 3b: Bracket 31b: Bracket portion 4: Drill bit 5: Pressure foot 6: Cylinder 61: Cylinder 62: Inner peripheral surface 63: Cylinder chamber 64, 78: Opening (decompression mechanism) 65: Cylinder block 7: Compressor 71: Piston 72: Outer peripheral surface 73: Rod portion 74: Piston portion 75: Bottom 76: Peripheral wall portion 77: Internal space (decompression mechanism) CA: Compressed air t: Distance / Specified amount W: Workpiece Fig. 1 is a schematic diagram showing the drill processing apparatus before penetrating into the circuit board. Fig. 2 is a schematic diagram showing the drill processing apparatus after penetrating into the circuit board. Fig. 3 is a schematic diagram showing the state of the cylinder at the time of Fig. 1. Fig. 4 is a schematic diagram showing the state of the cylinder at the time of Fig. 2. None 61: Cylinder 62: Inner peripheral surface 63: Cylinder chamber 64, 78: Opening (decompression mechanism) 65: Cylinder block 71: Piston 72: Outer peripheral surface 73: Shaft portion 74: Piston portion 75: Bottom portion 76: Peripheral wall portion 77: Internal space (pressure reducing mechanism) CA: Compressed air

Claims

1. A drill bit processing apparatus, comprising: A machining table on which a workpiece is placed; a spindle that holds a drill bit so that it can rotate at high speed; A pressure foot, located below the spindle, presses the workpiece onto the machining table; a cylinder, supporting the pressure foot so as to be movable relative to the spindle, the cylinder having: a cylinder supplied with compressed air; a piston connected to the pressure foot and sliding within the cylinder; and a pressure reducing mechanism that reduces the pressure within the cylinder, the pressure reducing mechanism being configured to reduce the pressure within the cylinder based on a predetermined amount of cylinder contraction, the predetermined amount being greater than or equal to the amount of descent of the spindle from the point where the drill bit penetrates the workpiece after the pressure foot abuts against it.

2. The drill bit processing apparatus as described in claim 1, wherein, The pressure-reducing mechanism is formed in the exhaust port of the cylinder and the piston. When the piston is in the maximum discharge position, the exhaust port of the cylinder is closed by the piston. When the piston is pressed into the specified amount from the maximum discharge position, the exhaust port of the cylinder communicates with the inside of the cylinder through the exhaust port of the piston, thereby reducing the pressure inside the cylinder.

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