JP2005153077A - Method for making deep hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and inexpensively work a deep hole with high positional accuracy without using a preliminary drilling drill and a guide bush. <P>SOLUTION: A guide hole can be made with high positional accuracy without the occurrence of breakage of a tool or the like by preventing the vibration, which is caused by the imbalance of a mass, in order to work the guide hole by rotationally driving a drill with a first rotational speed r1 at low speed in guide hole making processes of S1 and S2. After that, high dimensional accuracy and excellent surface roughness can be obtained with cutting by high-speed rotation without the occurrence of positional deviation and breakage or the like by suppressing the vibration, which is caused by the imbalance of a mass, even with high-speed rotation since the tip part of the drill is positioned by the guide hole even though hole drilling is performed to the target hole depth PZ2 by rotationally driving the drill with a second rotational speed r2, which is higher than the first rotational speed r1, in actual hole drilling processes of S4 and S5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a deep hole machining method, and more particularly to a technique for machining a high-precision deep hole easily and at low cost.

  When machining a deep hole using a long drill whose protrusion length L from the chuck is, for example, 10D or more with respect to the drill diameter D, if the rotational speed becomes high, the positional accuracy may decrease due to vibration caused by mass imbalance. While machining is not possible due to broken tools, drilling with low speed rotation may impair dimensional accuracy and surface roughness. In general, lowering the rotation speed also lowers the feed rate, resulting in poor machining efficiency. Become. On the other hand, as described in Patent Document 1, for example, a pilot hole is first processed using a drill for preliminary processing that is shorter than the depth of the hole to be processed, and then longer than the depth of the hole to be processed. A drill is used to perform the drilling process. As another method, as shown in FIG. 6, it is conceivable to perform drilling by positioning the long drill 104 with a guide bush 102 disposed in the vicinity of the workpiece 100.

JP-A-4-348803

  However, when the prepared hole is machined using the pre-machining drill, the number of tools increases and the tool needs to be changed, so that the machining cost increases and the machining time becomes long. Even when the guide bush is used, it is necessary to prepare the guide bush according to the diameter of the drill. Therefore, the number of parts is increased, the processing cost is increased, and the guide bush cannot be applied to a recess where the guide bush interferes with the workpiece.

  The present invention has been made in the background of the above circumstances, and its purpose is to enable deep holes to be machined easily and at low cost with high positional accuracy without using a preliminary drill or guide bush. There is to do.

  In order to achieve this object, the first invention is a deep hole machining method for machining a deep hole using a long drill having a long protruding length L from the chuck, and (a) a first rotation of the long drill A guide hole machining step in which a guide hole is machined by rotating at a speed r1 to form a guide hole shallower than a target deep hole; and (b) the long drill is driven at a higher speed than the first rotation speed r1 And a main drilling process for performing drilling to a depth of.

  2nd invention is the deep hole processing method of 1st invention, (a) The said protrusion length L is 10D or more with respect to the drill diameter D, (b) The depth of the said guide hole is drill diameter D. On the other hand, it is in the range of 1D to 3D.

  According to a third invention, in the deep hole machining method of the first or second invention, the feed speed of the long drill is changed in conjunction with the rotational speed, and the main drilling process is compared with the guide hole machining process. It is characterized by being fed at high speed.

  A fourth invention is the deep hole machining method according to any one of the first invention to the third invention, wherein the first rotation speed r1 is a hole drilling process by rotating the long drill at a constant rotation speed. Based on the relationship between the rotation speed of the tool and the tool life, the tool life is set to a rotation speed near or lower than the longest tool life.

A fifth invention is the deep hole machining method according to any one of the first to fourth inventions, wherein the first rotational speed r1 is set such that the protruding length L is 10D ≦ L ≦ 15D with respect to the drill diameter D. defined in the range of 300~2400min ^-1, 15D <defined within the 300～2100Min ^-1 when the L ≦ 20D, when 20D <the L ≦ 30D is defined within the 300～900Min ^-1 It is characterized by being able to.

  In such a deep hole machining method, the long drill is first rotationally driven at the first rotation speed r1 at a low speed to machine the guide hole, so that vibration caused by mass imbalance is prevented, and tool breakage or the like occurs. The guide hole can be machined with high positional accuracy without any problems. Thereafter, the long drill is rotationally driven at a speed higher than the first rotational speed r1, and drilling is performed to the target depth. However, since the drill tip is positioned by the guide hole, the mass of the drill is increased even at a high speed. Vibrations resulting from imbalance are suppressed, and no positional shift or breakage occurs, and high dimensional accuracy and excellent surface roughness can be obtained by cutting with high-speed rotation. This makes it possible to easily and cost-effectively process a deep hole with high positional accuracy and excellent surface roughness and dimensional accuracy without using a prefabricated drill or a guide bush.

  In the third invention, the feed speed of the long drill is changed in conjunction with the rotational speed, and the main drilling process is fed at a higher speed than the guide drilling process, so that drilling can be performed with high efficiency. it can.

  In the fourth aspect of the invention, an appropriate first rotation speed r1 is set according to the protruding length L, the material of the workpiece (work material), etc., so that the guide hole can be accurately avoided while reliably avoiding tool breakage or the like. Can be processed, and an excellent tool life can be obtained.

  In the fifth aspect of the invention, since an appropriate first rotation speed r1 is set according to the protruding length L, it may differ depending on the material of the workpiece, etc., but generally guides with high accuracy while avoiding tool breakage and the like. Holes can be machined and an excellent tool life is obtained.

  The deep hole machining method of the present invention is preferably applied to a long drill having a protruding length L of 10D or more as in the second invention, but can also be applied to a long drill shorter than 10D. It is desirable that a long drill is provided with a spiral chip discharge groove so as to have an axial dimension substantially the same as the protruding length L so that drilling can be performed at once. A spiral chip discharge groove may be provided only in the portion, and it may be premised on a step process in which a drill is extracted in the middle of drilling to discharge chips.

  The depth of the guide hole is suitably in the range of 1D to 3D with respect to the drill diameter D, and preferably in the range of 1D to 2D. If the depth of the guide hole is shallower than 1D, the positioning of the drill tip may not be sufficiently obtained, and vibration may occur and position accuracy may be impaired or the tool may be broken. When the high-precision drilling region by high-speed rotation is reduced and the feed speed is linked with the rotation speed, the processing efficiency is deteriorated.

  In the actual drilling process, for example, the drilling process is performed at a constant second rotational speed r2 that is faster than the first rotational speed r1, but the second rotational speed r2 is continuously changed. It is also possible to change it. The first rotation speed r1 may also be a constant rotation speed, but can be changed continuously or stepwise.

  At the time of transition from the guide hole machining step to the main drilling step, the rotation speed may be increased as it is, but the rotation may be temporarily stopped for ease of control. In addition, if a return step is provided to stop rotation and return only the predetermined dimension to the extraction direction, the chips can be reliably divided and the chips are good when rotated at a high speed in the subsequent drilling step. To be discharged. In the returning step, the long drill may be completely extracted from the guide hole, but the tip of the drill may remain in the guide hole. Also in this drilling process, step processing which extracts a long drill from a hole on the way can also be adopted as needed.

  The feed rate of the long drill is determined, for example, by the feed amount per one rotation of the drill. In that case, the feed rate is changed in conjunction with the rotation rate as in the third invention. However, it may be sent at a constant feed rate regardless of the rotation speed, or it may be sent at a higher speed than the guide hole machining process in the main drilling process regardless of the rotation speed. Various aspects are possible.

  The range of the first rotational speed r1 of the fifth invention is a result of drilling a S50C that is widely used as a work material, and depending on the material of the work material for which a deep hole is to be machined. It is changed appropriately.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram for explaining a drilling device 10 that can suitably carry out the deep hole machining method of the present invention, and a drill 12 is detachably attached to a chuck 16 of a rotary drive device 14 such as an electric motor. It is attached and is driven to rotate around the axis. The drill 12 is a two-blade long drill having a protruding length L from the chuck 16 of 10D or more with respect to the drill diameter D (see FIG. 4), and has an axial dimension substantially the same as the protruding length L. A pair of spiral chip discharge grooves 18 are provided, and chips that are cut by the cutting edge at the tip are discharged to the shank side, so that a deep hole having substantially the same depth as the protruding length L is formed at a time. Can be processed after dawn. In this embodiment, the drill diameter D = 6 mm, the protruding length L = 20D = 120 mm, and the total drill length is 180 mm.

  The rotary drive device 14 is moved up and down by a Z-axis moving device 22 having a Z-axis motor 20 and a feed screw (not shown), and the drill 12 is rotated around its axis by the rotary drive device 14. The workpiece 24 is drilled by being moved downward by the Z-axis moving device 22 while being rotationally driven. The Z-axis motor 20 is provided with a Z-axis position detector 26 such as an encoder so that the Z-axis position of the rotary drive device 14, that is, the axial position of the drill 12 is detected. The workpiece 24 is disposed on the XY table 28, moved in the XY plane perpendicular to the Z axis, and positioned and fixed at a predetermined drilling position. The rotational driving device 14, the Z-axis moving device 22, and the XY table 28 are controlled by a controller 30 including a computer. The controller 30 detects the Z-axis position. Various detection signals necessary for the control are supplied from the device 26 or the like. Instead of providing the XY table 28, the workpiece 24 may be fixed at a fixed position by moving the Z-axis moving device 22 in the XY direction.

  The controller 30 performs drilling according to the flowchart shown in FIG. 2 by performing signal processing according to a program stored in advance in the ROM while utilizing the temporary storage function of the RAM. Of the series of steps in FIG. 2, steps S1 and S2 are guide hole machining steps, step S3 is a return step, and steps S4 and S5 are main drilling steps. This drilling process is performed while supplying a predetermined cutting fluid.

In step S1 of FIG. 2, the rotary drive device 14 rotates the drill 12 around the axis center at a predetermined relatively low first rotational speed r1, while the Z-axis moving device 22 performs a predetermined feed speed. Is lowered to approach the workpiece 24. In the present embodiment, the workpiece 24 is S50C, and the first rotation speed r1 is appropriately determined within the range of 300 to 2100 min ⁻¹ because the protruding length L = 20D. Further, the feed rate is a feed amount per one rotation of the drill, and is set to about 0.20 mm / rev, for example. The feed rate is changed in conjunction with the rotation rate, so that the low-speed feed corresponding to the first rotation rate r1 is used here. Is lowered.

  In step S2, it is determined whether or not the Z-axis direction position PZ detected by the Z-axis position detector 26 has reached a predetermined guide hole depth PZ1, and step S1 is performed until the guide hole depth PZ1 is reached. repeat. That is, as shown in FIG. 3, until the guide hole depth PZ1 is reached, drilling is performed while the drill 12 is rotationally driven at a relatively low first rotational speed r1, and thus the workpiece 24 is subjected to drilling. As shown in FIG. 4A, a guide hole 32 having a depth PZ1 is formed. The guide hole depth PZ1 is sufficiently shallow within a range of 1D to 2D with respect to the drill diameter D as compared with a target hole depth PZ2, for example, a depth dimension close to the protruding length L = 20D.

  Here, the protruding length L of the drill 12 has a length dimension of 20D with respect to the drill diameter D. However, since the rotation speed is low in the guide hole processing step of the above steps S1 and S2, it results from imbalance of mass. Generation of vibration is suppressed, and the guide hole 32 can be processed with high positional accuracy without causing tool breakage or the like.

The first rotation speed r1 is appropriately determined within a range of 300 to 2100 min ⁻¹ based on the test result shown in FIG. 5B so that the guide hole 32 can be machined with high positional accuracy. Referring to FIG. 5 in detail, as shown in (a), three types of long drills with different protruding lengths L are prepared and rotated at five rotational speeds 880, 1400, 2100, 2400, and 2700 min ^−1. Then, drilling was performed under the following processing conditions, and the number of drilled holes until the tool life was reached was examined. The result is (b). Both drill diameters D are 6 mm. Further, tool life is wear width of basically flank wear V _B is determined by whether or not reached 0.2 mm, according to the tool breakage those machined hole number 0. 1 is a vertical type, a test was conducted using a horizontal machining center as shown in the following processing conditions.
(Processing conditions)
Work material: S50C
Feeding speed: 0.20mm / rev (non-step)
Cutting fluid: Water-soluble cutting fluid Machine: Horizontal machining center

Then, from the test result of FIG. 5 (b), for tool No. 2 having a protrusion length L of 20D which is the same as that of the present embodiment, an excellent tool life is obtained up to about 2100 min ⁻¹ , so that the protrusion length L is 15D < In the case of L ≦ 20D, if the first rotational speed r1 is set within a range of 300 to 2100 min ⁻¹ , drilling can be performed with high positional accuracy without causing tool breakage. The first rotation speed r1 is set within a range of 300 to 2100 min ⁻¹ .

Further, for a 15D tool No1 with a relatively short protruding length L, an excellent tool life is obtained up to about 2400 min ⁻¹ , and therefore when the protruding length L is 10D ≦ L ≦ 15D, 300 to 2400 min ^−1. If the first rotation speed r1 is set within the range, the drilling can be performed with high positional accuracy without causing tool breakage. On the other hand, projecting the tool No3 length L is longer 30D than this example, it is possible to perform the drilling without causing tool breakage be about 880Min ^-1, protruding length L of 20D <L In the case of ≦ 30D, if the first rotation speed r1 is set within a range of 300 to 900 min ⁻¹ , drilling can be performed with high positional accuracy without causing tool breakage.

  Returning to FIG. 2, in step S <b> 3, the rotation of the drill 12 by the rotation driving device 14 and the lowering by the Z-axis moving device 22 are temporarily stopped, and the drill 12 is moved backward (ascended) by the Z-axis moving device 22. ) As a result, the chips are reliably divided, and the chips are reliably discharged from the chip discharge groove 18 when the drill 12 is rotationally driven again in the main drilling process after step S4. The return dimension of the drill 12 is very small and is sufficiently smaller than the guide hole depth PZ 1, and the drill tip is held in the guide hole 32.

In step S4, the drill 12 is lowered at a predetermined feed speed by the Z-axis moving device 22 while the drill 12 is driven to rotate around the shaft center at a predetermined second rotation speed r2 by the rotation drive device 14, and drilled again. Processing. Here, since the tip of the drill is positioned by the guide hole 32, vibration caused by imbalance of mass is suppressed even at high speed rotation, and there is no possibility of causing position shift or breakage. Therefore, the second rotation speed r2 Is set at a higher speed than the first rotational speed r1, for example, a rotational speed of 3000 min ⁻¹ or higher so that high dimensional accuracy and excellent surface roughness can be obtained by cutting by high-speed rotation. The feed rate is the feed amount per one rotation of the drill, and is the same as that in step S1. However, since the feed rate is changed in conjunction with the rotation speed, it is lowered at a high speed feed corresponding to the second rotation speed r2. .

  In step S5, it is determined whether or not the Z-axis direction position PZ detected by the Z-axis position detector 26 has reached a predetermined target hole depth PZ2, and step is performed until the hole depth PZ2 is reached. Repeat S4. That is, as shown in FIG. 3, drilling is performed from the guide hole depth PZ1 to the target hole depth PZ2 while the drill 12 is rotationally driven at the high-speed second rotational speed r2. A deep hole 34 having a target hole depth PZ2 is formed in the workpiece 24 as shown in FIG. The hole depth PZ2 can be a dimension close to the protruding length L = 20D, and is appropriately set within a range of, for example, (L-10) mm or less in consideration of chip discharge.

  When the Z-axis direction position PZ reaches the target hole depth PZ2, an end process is performed in step S6, the drill 12 is retracted upward at a predetermined return speed and pulled out from the deep hole 34. Stop rotation around the mind.

  As described above, in this embodiment, in the guide hole machining process of steps S1 and S2, first, the drill 12 is driven to rotate at the first rotation speed r1 at a low speed to process the guide hole 32. The generated vibration is prevented, and the guide hole 32 can be processed with high positional accuracy without causing tool breakage or the like. Thereafter, in the main drilling step of steps S4 and S5, the drill 12 is rotationally driven at a second rotational speed r2 higher than the first rotational speed r1, and drilling is performed to the target hole depth PZ2. Since the tip of the drill is positioned by the guide hole 32, vibration caused by mass imbalance is suppressed even at high speed rotation, and no positional deviation or breakage occurs, and high dimensional accuracy is achieved by cutting by high speed rotation. And excellent surface roughness. As a result, the deep hole 34 with high positional accuracy and excellent surface roughness and dimensional accuracy can be processed easily and at low cost without using a preliminary drill or guide bush.

In this embodiment, the feed speed of the drill 12 is changed in conjunction with the rotational speed, and in the main drilling process in which most holes are drilled, the guide 12 is fed at a higher speed than the guide hole machining process. In the drilling process, the machining efficiency is improved as a whole although the machining efficiency is poor. That is, as shown in FIG. 5B, in the case of the tool No. 2 having the same protruding length L = 20D as in the present embodiment, when drilling is performed at a constant rotational speed from the beginning, about 2100 min ⁻¹ is the limit. However, in this embodiment, the drilling process can be performed at 3000 min ⁻¹ or more, and the processing time can be shortened.

Further, in this embodiment, as shown in FIG. 5, the rotational speed and tool when drilling is performed by rotating the long drill at a constant rotational speed using the same work material as the workpiece 24. The relationship with the service life is investigated, and the first rotation speed r1 is set within the range of 300 to 2100 min ^-1 , which is the rotation speed where the tool life is the longest or lower than that. The guide hole 32 can be machined with high accuracy while avoiding the above, and an excellent tool life can be obtained.

Incidentally, performs drilling at the following processing conditions in accordance with the present embodiment, when the wear width of the flank wear V _B is examined machined hole number to reach the 0.2 mm, a 1100 hole, the tool of FIG. 5 Durability improved compared to the maximum number of drilled holes in No2. 1 is a vertical type, a test was conducted using a horizontal machining center as shown in the following processing conditions.
(Processing conditions)
Drill diameter D: 6mm
Total drill length: 180mm
Protruding length L: 120mm (20D)
Guide hole depth PZ1: 10 mm (1.7 D)
Total machining depth PZ2: 110mm
Work material: S50C
First rotation speed r1: 1400 min ⁻¹ (26.4 m / min)
Second rotation speed r2: 4775 min ⁻¹ (90.0 m / min)
Feeding speed: 0.20mm / rev (non-step)
Cutting fluid: Water-soluble cutting fluid Machine: Horizontal machining center

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention implements in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

It is a schematic block diagram of the drilling apparatus which can implement suitably the deep hole processing method of this invention. It is a flowchart explaining the action | operation at the time of drilling a deep hole according to the deep hole processing method of this invention using the drilling apparatus of FIG. It is a figure explaining the relationship between the hole depth and the rotational speed in the drilling process of FIG. FIGS. 2A and 2B are cross-sectional views at the time of drilling in FIG. 2, where FIG. 2A is a stage where a guide hole having a depth PZ1 is formed, and FIG. 2B is a stage where a deep hole having a depth PZ2 is formed. This figure explains the results of investigating the relationship between the rotational speed and tool life when drilling by rotating a long drill at a constant rotational speed. (A) is the specifications of the drill used. b) is the test result. It is sectional drawing explaining an example of the conventional deep hole processing method which drills using a guide bush.

Explanation of symbols

12: Drill (long drill) 16: Chuck 32: Guide hole 34: Deep hole D: Drill diameter L: Projection length PZ1: Guide hole depth PZ2: Target hole depth r1: First rotation speed Step S1, S2: Guide hole machining step Steps S4 and S5: Main drilling step

Claims (5)

A deep hole machining method for machining a deep hole using a long drill having a long protruding length L from the chuck,
A guide hole machining step in which the long drill is rotationally driven at a first rotational speed r1 to machine a guide hole shallower than a target deep hole;
A main drilling step in which the long drill is rotationally driven at a speed higher than the first rotational speed r1 to perform drilling to a target depth;
A deep hole processing method characterized by comprising: The protruding length L is 10D or more with respect to the drill diameter D,
The depth of the said guide hole is in the range of 1D-3D with respect to the drill diameter D. The deep hole processing method of Claim 1 characterized by the above-mentioned. 3. The depth according to claim 1, wherein a feed speed of the long drill is changed in conjunction with a rotational speed, and the main drilling process is performed at a higher speed than the guide hole machining process. Drilling method. Whether the first rotational speed r1 is around the rotational speed with the longest tool life based on the relationship between the rotational speed and the tool life when the long drill is rotationally driven at a constant rotational speed for drilling. The deep hole machining method according to any one of claims 1 to 3, wherein the rotational speed is set to be lower than that. The first rotational speed r1 is determined within a range of 300 to 2400 min ⁻¹ when the protruding length L is 10D ≦ L ≦ 15D with respect to the drill diameter D, and is 300 to when 15D <L ≦ 20D. defined in the range of 2100min ^-1, 20D <deep hole drilling according to any one of claims 1 to 4 when L ≦ 30D is characterized in that defined by the range of 300～900Min ^-1 Method.

Images