JP2013052482A - Method of machining work - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably bore through-holes even when substrates with a dispersion in thickness are machined.SOLUTION: This method of machining a work includes: a first step of confirming that the relation "H>t+t+α" is established when the blade length of a drill is H, the thickness of a work 1 stack is t, the thickness of a conductive plate is t, and an adjustment value is α; a second step (S1) of placing a lower plate on a table, the conductive plate on the lower plate, and a work on the conductive plate in this order; a third step (S2) of lowering the drill at a cutting rate pre-set as a cutting rate used to the surface of the lower plate after the drill is moved to the upper side of a machining position for the work placed in the second step; and a fourth step (S3) of lowering the drill by an additional cutting rate which is equal to the distal end length of the drill after it is detected whether a voltage induced in a rotor shaft is applied to the conductive plate or not while the drill lowers in the third step.

Description

  The present invention relates to a workpiece machining method, and more particularly to a workpiece machining method in which a workpiece composed of a conductive layer and an insulating layer is fixed on a table and is machined by a drill.

  Conventionally, when drilling a printed circuit board, since the variation in the thickness direction of the printed circuit board is large, a drill was cut from the surface of the printed circuit board based on the surface of the printed circuit board, and a through hole was made in the printed circuit board . As a technique for processing such a printed circuit board with a drill, for example, the inventions described in Patent Documents 1 and 2 are known.

  Among them, in Patent Document 1, in a workpiece machining method for machining a workpiece by holding a tool on a rotatable rotor shaft having a high resistance to ground, the workpiece is insulated from the ground, and an axis generated on the rotor shaft. The invention is characterized in that the tip position of the tool is detected by measuring the voltage through the workpiece. In this invention, a bush formed of a conductive material is disposed at the tip of the installed pressure foot, the drill and the bush come into contact with the copper foil on the workpiece surface, and the axial voltage generated on the rotor shaft is detected via the bush. Then, it is disclosed that the height at which the drill comes into contact with the printed circuit board is accurately measured to process the through hole.

  Further, in Patent Document 2, in order to measure the height of the drill with respect to the surface layer of the printed circuit board, a potential difference is given between the drill and the conductive surface layer or the nth conductive layer, The signal generated between the drill and the surface layer at the time of contact is used to determine the zero level of the hole depth, and the signal generated at the time of contact between the drill tip and the nth conductive layer is The invention is described as being used to determine the final level.

Japanese Patent Laid-Open No. 2001-341052 Japanese Patent Laid-Open No. 7-285097

  By the way, in the technique described in Patent Document 1, in order to process a printed board having a variation in thickness, the drill is usually cut from the board surface by a cutting amount obtained by multiplying the thickness of the board by a safety factor. I was processing. In such a method, the cutting depth of the drill after penetrating the printed circuit board is minimized in order to improve the processing efficiency (for example, the safety factor is set to 1.23). Therefore, when a thick printed circuit board is included due to variations in the thickness of the printed circuit board, it is not penetrated into a single printed circuit board (hereinafter referred to as 1 stack) formed by stacking one or more sheets. Holes were machined, and machining quality was sometimes reduced. In other words, if three stacks of 1 mm thickness are taken as one stack and the safety factor of the cutting depth of the drill is 1.23, the cutting depth is 3.69 mm, but if three substrates of 1.24 mm thickness are taken as one stack, The thickness of one stack is 3.72 mm, and it is not possible to make through holes in all of the printed circuit boards.

  On the other hand, the technique described in Patent Document 2 is used for processing a blind hole (bottomed hole). Therefore, Patent Document 2 does not disclose processing a substrate whose lowermost layer is a metal layer. As a result, the through hole cannot be reliably processed.

  Therefore, the problem to be solved by the present invention is to ensure that through holes can be processed in one stack of printed circuit boards even when thick printed circuit boards are included due to variations in the thickness of the printed circuit boards. It is in.

In order to solve the above-mentioned problem, the first means is to relatively move a work composed of a conductive layer and an insulating layer, a table on which the work is placed, and a drill held on the rotor shaft. In the workpiece machining method, when the cutting edge length of the drill is H ₄ , the thickness of the workpiece 1 stack is t ₁ , the thickness of the conductive plate is t ₂ , and the adjustment value is α, H ₄ > t ₁ + t ₂ + α

A first step for confirming that the relationship is established; a second step for sequentially stacking a lower plate on the table, a conductive plate on the lower plate, and a workpiece on the conductive slope; and the second step A third step of moving the drill above the processing position of the workpieces stacked in the step and then lowering by a preset cutting amount as a cutting amount to the surface of the lower plate; and the third step And detecting whether or not a voltage induced in the rotor shaft is applied to the conductive plate in the process of lowering at a fourth step, and then lowering the drill by an additional depth of cut that is the tip length of the drill. And a process.

  In this case, if the voltage induced in the rotor shaft from the conductive plate is not detected before the drill reaches the surface of the lower plate in the fourth step, an alarm is output and the processing is stopped. A fifth step may be further provided.

  According to the present invention, even when a thick printed circuit board is included due to variations in the thickness of the printed circuit board, the through holes can be reliably processed in one stack of printed circuit boards.

It is explanatory drawing which shows the structure of the workpiece processing apparatus which concerns on embodiment of this invention. It is explanatory drawing shown about the dimensional relationship of each part in this embodiment. It is a flowchart which shows the operation | movement procedure in embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a workpiece machining apparatus according to an embodiment of the present invention. The workpiece machining apparatus according to the present invention is roughly divided into a workpiece fixing portion and a workpiece machining portion.

  The workpiece fixing unit includes a table 6 on which the workpiece 1 is placed and positioned, a detector 4 and an NC (Numerical Control) device. On the table 6, the lower plate 3, the conductive plate 2, and the work 1 are stacked in this order from below, and are positioned on the table 6 by reference pins (not shown).

  The lower plate 3 is made of, for example, resin, and the conductive plate 2 made of, for example, aluminum is placed thereon. The work 1 is composed of a conductive layer and an insulating layer, and is placed so that the insulating layer is positioned on the conductive plate 2 side in the drawing and the conductive layer is positioned on the drill 19 side in the drawing. In FIG. 1, three workpieces 1 are stacked to form one stack.

  The detector 4 detects an electrical signal from the conductive plate 2 and outputs the detected electrical signal to the NC device 5. The NC device 5 is a device that numerically controls the movement of a machine tool or an industrial robot, and converts digital information of a computer into command information for a servo mechanism that directly controls the movement of the machine.

  The workpiece machining section includes a three-phase power source 7, an inverter power source 8, a coil 9, a rotor 10, a rotor shaft 11, a saddle 12, a holder 13, a piston rod 14, a pressure foot 15, a bush holder 16, a bush 17, a collet chuck 18, and a drill. 19 is provided.

  The three-phase power source 7 is a commercial AC voltage power source, and an inverter power source 8 is connected. The inverter power supply 8 converts a commercial AC voltage from the three-phase power supply 7 into an AC voltage having a high frequency, and a coil 9 as a stator is connected to the inverter power supply 8.

  The rotor shaft 11 is disposed in a space inside the coil 9 and is rotatably supported by an air radial bearing (not shown). A rotor 10, which is a rotor in which a copper material is formed in an end ring shape, is attached to the rotor shaft 11. A drill 19 is detachably held at the lower end of the rotor shaft 11 via a collet chuck 18. The rotor shaft 11 is also supported by the saddle 12 via a holder 13.

  The saddle 12 moves the drill 19 in the Z-axis direction (direction perpendicular to the workpiece 1) by moving the holder 13 up and down. The holder 13 is provided with a piston rod 14 that supports the pressure foot 15 so as to be movable in the Z-axis direction, and a bush holder 16 that holds a bush 17 is provided at the lower end of the pressure foot 15.

  The detector 4 includes a filter and a comparator (not shown). The filter inputs the inverter AC voltage to the comparator from the shaft voltage on which the commercial AC voltage of the frequency of the three-phase power source 7 (for example, 50 Hz) and the inverter AC voltage that is the control frequency of the inverter power source 8 (for example, 1 kHz) are superimposed. The comparator compares the inverter AC voltage with a predetermined voltage, and outputs a detection signal to the NC device 5 when the inverter AC voltage exceeds a predetermined voltage. The voltage detected by the comparator changes when the tip 19 a of the drill 19 contacts the conductive plate 2.

  Note that one stack of the work 1, the conductive plate 2, and the lower plate 3 are placed on the table 6 by a reference pin (not shown), but the bottom of the pressure foot 15 is lowered by the bush 17 provided in the Z-axis direction. Since the workpiece 1 is pressed in the direction, the workpiece 1 is not processed while being lifted off the table 6.

  Further, the NC device 5 controls the workpiece machining unit, for example, controls a drive motor (not shown), raises and lowers the holder 13, and performs position control of the drill 19 (position control in the Z-axis direction) and rotation control of the drill 19. .

FIG. 2 is an explanatory diagram showing the dimensional relationship of each part in the present embodiment.
In the figure, the drill 19 is usually the tip 19a of the drill 19 is held by the collet chuck 18 so that the lower end of the tip of the collet chuck 18 of the rotor shaft 11 at a distance of H _1. When the rotor shaft 11 is positioned at the standby position, the height of the tip of the drill 19 from the surface of the table 6 is H. Hereinafter, the position where the height is H with respect to the surface of the table 6 is referred to as a movement origin O of the drill 19 in the Z-axis direction. The drill 19 designates the Z coordinate of the target position from the NC device 5 with the movement origin O as a reference.

H ₂ is a distance that is set in advance prior to processing as the distance that the tip of the drill 19 held by the collet chuck 18 reaches the surface of the lower plate 3. This distance H _2, the shank portion of the drill 19 is lowered drill 19 were broken (edge portion without drill) is set to prevent crashing on the workpiece 1. At this time, although an error occurs in the distance H ₂ by the mounting accuracy of the workpiece 1 and the drill 19, since the error is a distance that fits to the thickness of the lower plate 3 and the conductive plate 2, the drill 19 reaches the table 6 In addition, it does not reach the conductive plate 2 and cannot be detected.

H ₃ is the distance from the surface of the lower plate 3 to the position to move the drill tip in the horizontal direction. That is, the distance from the surface of the lower plate 3 to the cutting feed start position to the second and subsequent machining portions (drilling positions), and the distance at which the bush 17 is 1 to 2 mm from the surface of the workpiece 1. The first drilling is done from the position shown in FIG. 2, drilling of the second and subsequent runs from the position of a distance H _2.

H ₄ is the blade length of the drill 19 and is about 4.5 mm for the drill 19 having a diameter of 0.3 mm and about 7.5 mm for the drill 19 having a diameter of 0.5 mm. The thickness of one workpiece 1 (printed circuit board) is about 1 mm, and as shown in FIG. 2, the thickness t _{1 of} one stack in which three pieces are stacked is about 3 mm. The thickness _{t 2} of the conductive plate 2 is 0.1 mm to 0.3 mm, the lower plate 3 is about 1.6 mm. Incidentally, the blade length _{H 4} is,
H ₄ > t ₁ + t ₂ + α (1)
The drill 19 that has been confirmed in advance is selected and held by the collet chuck 18. α is an adjustment value, which is obtained from Expression (2), and is intended to prevent the shank portion from colliding with the surface of the work 1 even if there is a variation in the thickness of the printed circuit board and an additional depth of cut described later.

α> t _m × m + g _s + k _i (2)
t _m is a maximum thickness deviation per printed circuit board (difference between the maximum thickness and the average thickness of the printed circuit board), and is determined in advance prior to processing using a plurality of printed circuit boards of each thickness. m is the number of stacks. g _s is a mounting error of the drill 19 and the work 1, as described above, usually but is set to 0 because the distance to fit the thickness of the lower plate 3 and the conductive plate 2 is set by the operator as needed. k _i is an additional depth of cut, and in the case of the present embodiment, the tip length d of the drill 19 is obtained from the formula (3).

d = φ / 2 tan (θ / 2) (3)
Here, φ is the diameter of the drill, and θ is the tip angle of the drill 19. θ is normally 120 ° to 140 ° in a drill for processing a printed circuit board. Usually α is set to 1 to 3 mm.

  In addition, the dimension in FIG. 2 shows a specific example in order to explain the processing method in the present embodiment, and the present invention is not limited to the illustrated dimension.

  FIG. 3 is a flowchart showing an operation procedure in the embodiment of the present invention, which is executed by the CPU of the control device of the NC device 5. The CPU includes a control unit and a calculation unit. The control unit controls the interpretation of instructions and the control flow of the program, and the calculation unit executes the calculation. The program is stored in a memory (not shown), and an instruction to be executed (a numerical value or a sequence of numerical values) is taken out from the memory in which the program is placed and executed. Here, the part which NC unit 5 performs is programmed in the flowchart of the FIG.

In the flowchart of FIG. 3, first, a stack of workpieces 1 is placed on the conductive plate 2 by a workpiece transfer device (not shown) (step S <b> 1), and the drill 19 is moved above the machining position of the workpieces 1. After completion of the movement, by a distance _{H 2} is lowered (Step S2). If the distance is detected with H ₂ by detector 4 signals conductive plate 2 until lowering, after the drill 19 is lowered only as thick additional depth of cut of the conductive plate 2 (step S3), and to be next processed if there is a hole (step S4: Y), from the raised by H ₃ above the next processing position moving the drill 19 (step S5). Then, repeating the steps of lowering only H ₃ again returns to step S2. Therefore, the fact that the detector 4 has detected a signal indicating that the tip 19a of the drill 19 has contacted the conductive plate 2 in step S3 means that a through hole has been formed.

In step S3, although an additional depth of cut _{k i} was _k i = d, an additional depth of cut _{k i k i = d + d} c: if _{(d c} the thickness of the printed circuit board of the conductive layer) and, 1 Even when the lowermost layer of the printed circuit board of the stack is a conductive layer, the through hole can be processed.

  When the signal of the conductive plate 3 is not detected in step S3 (step S3: N), since the through hole is not formed, an alarm is output and the machining is stopped (step S8). If there is no hole to be processed next in step S4 (step S4: N), the workpiece 1 is unloaded (step S6), and the presence / absence of the workpiece 1 to be processed next is determined (step S7). Then, when there is no next workpiece 1 (step S7: N), the processing is finished, and when there is a next workpiece 1, the processing after step S1 is repeated.

  As described above, in this embodiment, as long as the relationship of the expression (1) is satisfied, a through hole can be reliably opened even when a workpiece having a variation in thickness is processed. Quality degradation can be prevented.

The first step in the claims is a process for confirming the thickness t ₁ of the printed circuit board 1 by the above equation (1), the second step is in step S1, and the third step is in step S2. The fourth process corresponds to step S3, and the fifth process corresponds to step S8. The detection in step S3 is performed by the detector 4, and the NC device 5 performs drill movement control, lift control, alarm output, and machining control.

  It should be noted that the present invention is not limited to this embodiment, and various modifications are possible, and all technical matters included in the technical idea described in the scope of claims are the subject of the present invention.

1 Work 2 Conductive plate 3 Lower plate 4 Detector 5 NC device 6 Table 11 Rotor shaft 19 Drill

Claims (3)

In a workpiece machining method for machining a workpiece by relatively moving a workpiece composed of a conductive layer and an insulating layer, a table on which the workpiece is placed, and a drill held by a rotor shaft,
H ₄ > t ₁ + t ₂ + α, where H _{4 is} the length of the drill, t _{1 is} the thickness of one substrate constituting the workpiece, t _{2 is} the thickness of the conductive plate, and α is the adjustment value.
A first step of confirming that the relationship of
A second step of sequentially stacking a lower plate on the table, a conductive plate on the lower plate, and a workpiece on the conductive slope;
A third step of moving the drill above the processing position of the workpieces stacked in the second step and then lowering by a preset cutting amount as a cutting amount to the surface of the lower plate;
After detecting whether or not a voltage induced in the rotor shaft is applied to the conductive plate in the process of descending in the third step, the drill is moved by an additional depth of cut that is the tip length of the drill. A fourth step of lowering;
A method for machining a workpiece, comprising: In the processing method of the workpiece according to claim 1,
The additional cutting amount in the fourth step is a cutting amount obtained by adding the thickness of the conductive layer of the workpiece to the tip length of the drill;
A workpiece machining method characterized by In the processing method of the workpiece | work of Claim 1 or 2,
If the voltage induced in the rotor shaft from the conductive plate is not detected before the drill reaches the surface of the lower plate in the fourth step, an alarm is output and the machining is stopped. A workpiece machining method, further comprising a step.