JP2005219135A - Truing method in centerless grinding machine for bar-like workpiece, and centerless grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a truing technology improving surface roughness of a machined surface of a workpiece to grind even a workpiece with an extremely small diameter and obtaining high production efficiency, in centerless grinding for grinding a bar-like workpiece into stepped shape. <P>SOLUTION: A centerless grinding machine performs centerless grinding of a tip shaft part Wb of the bar-like workpiece W into stepped shape by a conductive grinding wheel 1 with a profile corresponding to the final shape of the tip shaft part Wb of the bar-like workpiece W. After carrying out electric discharge truing of a grinding wheel surface 10 of the grinding wheel 1, a part for grinding the tip shaft part Wb of the workpiece W in the grinding wheel surface 10 is subjected to mechanical truing using a truing tool with a shaft similar to workpiece shape and having a cylindrical truing surface 31a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a truing method and a centerless grinding method for a centerless grinding machine for a bar-shaped workpiece, and more particularly to a truing technique for a centerless grinding machine for grinding a tip shaft portion of a bar-shaped workpiece.

  Conventionally, centerless grinding by an in-feed grinding method has been generally performed as a method of machining a tip shaft portion of a rod-like workpiece (hereinafter referred to as a workpiece) into a stepped shape.

  In-feed grinding is supported by rotating the large-diameter base shaft of the workpiece with an adjustment wheel and blade, and pressing the workpiece against the adjustment wheel with a presser roller, while creating a profile corresponding to the final shape of the small-diameter tip shaft. The grinding wheel is used to grind the tip shaft portion of the workpiece (see, for example, Patent Document 1). In such in-feed grinding, the grinding wheel is cut and fed without supporting the tip shaft portion of the workpiece. Since grinding is difficult, it is difficult to obtain the same degree of concentricity because the tip shaft portion is bent, and in order to avoid this bending, it is necessary to slow down the cutting feed amount of the grinding wheel, which results in longer cycle time and higher production efficiency. It was bad.

  In consideration of this point, the applicant applies the work shaft to the grinding wheel by the work pusher while forcibly rotating the work by pressing and supporting the base part of the work against the adjusting wheel by the pressure roller. We have developed and proposed a so-called push-through feed grinding method in which the tip shaft portion of the workpiece is ground by a grinding wheel by feeding it relatively to (see Patent Document 2). It has become possible to obtain high production efficiency while ensuring high coaxiality and cylindricity of the tip shaft portion.

  By the way, also in this push-through feed grinding, a grinding wheel having a profile corresponding to the final shape of the small-diameter tip shaft portion of the workpiece is used. In order to effectively exhibit the above-described effects, the grinding wheel of the grinding wheel is used. It is necessary to apply truing to the surface regularly or at an appropriate interval.

  This type of truing method includes discharge truing and mechanical or contact truing. The former discharge truing is a non-contact truing method using the discharge action on the grindstone surface of a conductive grindstone using a conductive bonding material such as a conductive resin bond or a metal bond. The grindstone surface is very sharp, but the surface roughness of the work surface of the workpiece is relatively rough. On the other hand, the latter contact type truing mechanically trues the grindstone surface by directly applying a truer or dresser to the grindstone surface, but the surface roughness of the workpiece surface with the truing grindstone is relatively fine. The sharpness of the grinding wheel surface is not so good.

  Thus, in any truing method, there are advantages and disadvantages. When grinding the tip shaft part of a rod-shaped workpiece into a stepped shape, the grinding wheel surface of the grinding wheel is a cylindrical grinding surface for grinding the tip shaft part ( Since the cross-sectional contour is straight) and the tapered cylindrical surface (cross-sectional contour is tapered) that grinds the boundary portion between the tip shaft portion and the base shaft portion, a good sharpness can be obtained and the sharpness can be reduced. Emphasizing the point that it can last for a long time, in push-through feed grinding, a grinding wheel equipped with a conductive grinding wheel capable of discharge truing is suitably used.

  However, some rod-like workpieces, such as micro drills, have a very small tip shaft diameter (0.05 mm or less), and such grinding wheels with discharge truing are extremely fine. There has been a situation in which it is difficult or impossible to machine the tip shaft portion of the diameter.

In other words, in the case of an ultra-fine workpiece, the surface roughness of the processed surface is an element that acts as a crack as it is, and in the grinding wheel that has been subjected to electric discharge truing, the surface roughness of the workpiece is too fine. For this reason, there is a limit to the diameter of the workpiece to be machined, making it difficult or impossible to machine an extremely thin workpiece.
JP-A-60-177849 JP 2002-25194 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a grindstone while taking advantage of electric discharge truing in centerless grinding in which a rod-shaped workpiece is ground into a stepped shape. Providing truing technology that improves the surface roughness of the work surface of the workpiece by aligning the abrasive tip of the wheel surface of the car, enables grinding even for ultra-fine workpieces, and achieves high production efficiency. There is.

  Another object of the present invention is to provide a centerless grinding technique of a push-through feed grinding method that employs the above truing technique.

  In order to achieve the above object, the truing method of the present invention performs centerless grinding of the tip shaft portion of the rod-shaped workpiece into a stepped shape with a conductive grinding wheel having a profile corresponding to the final shape of the tip shaft portion of the rod-shaped workpiece. A centerless grinder for truing the grinding wheel surface of the grinding wheel, and after discharging the truing wheel surface of the grinding wheel, a portion of the grinding wheel surface for grinding the tip shaft portion of the workpiece. It is characterized by mechanical truing using a truing tool with a shaft similar in shape and having a cylindrical truing surface.

  As a preferred embodiment, the mechanical truing by the truing tool with a shaft is rotationally driven by placing the truing tool with a shaft on a blade of a centerless grinding machine and rotating the truing tool with a shaft by an adjusting wheel. A portion of the grinding wheel surface of the grinding wheel to be ground is trued by causing the grinding wheel to be cut relatively to the truing tool with the shaft.

  As a more specific example, by placing the base shaft portion of the truing tool with shaft on the blade of a centerless grinding machine and pressing and supporting the base shaft portion against the adjusting wheel by pressing means, the truing tool with shaft is supported. The truing tool with the shaft is fed relative to the grinding wheel by the feeding means in the axial direction while forcibly rotating the truing tool, so that the cylindrical truing surface of the truing tool with the shaft causes the grinding wheel surface of the grinding wheel to Truing the part to grind the tip shaft part of the workpiece.

In this case, the truing tool with a shaft preferably has at least the reference shaft portion having the same outer diameter as the base shaft portion serving as a machining reference of the workpiece, and the truing tool with a shaft is provided on the cylindrical truing tool. A diamond shaft truing tool in which diamond abrasive grains are used as the abrasive grains is preferably used.

  On the other hand, the discharge truing is performed by truing the entire grinding wheel surface of the grinding wheel by using a truer as a discharge truing electrode, and this discharge truing is performed while the grinding wheel is stopped or ground depending on the purpose. .

  The truer preferably comprises a discharge truing electrode in the form of a disc-like truer.

  Further, the centerless grinding method of the present invention adopts truing by the above truing method, and presses and supports the base shaft portion of the workpiece against the adjustment wheel by the pressing means, thereby forcibly rotating the workpiece. Is fed relative to the grinding wheel by the feeding means in the axial direction, the tip shaft portion of the workpiece is ground by the grinding wheel, and the grinding wheel surface of the grinding wheel is periodically or at an appropriate interval, It is characterized by applying truing by the above truing method.

  The truing technique of the present invention was born as a result of various test studies by the present inventors. In other words, the present inventor, in push-through feed grinding, takes advantage of electric discharge truing and solves the problem, thereby limiting the object of processing without limiting the object to be machined. In order to develop a truing technology that can effectively machine the extremely thin tip shaft even for a rod-shaped workpiece having a part, we initially considered various improvements as follows. It did not lead to a drastic solution.

  First of all, we considered reducing the surface roughness by reducing the grain size of the grindstone. However, if this is done, the sharpness will worsen and the grinding speed must be slowed down. The effect of through-feed grinding will be halved.

  In addition, the cylindrical grinding surface that grinds the tip shaft part of the workpiece has a fine-grained grinding wheel surface with fine-grained abrasive grains, and the tapered cylindrical surface that grinds the boundary part between the tip shaft part and the base shaft part has a coarse grain size. However, in this case, as shown in FIG. 6, a connecting portion c between the fine-grained grindstone surface “a” and the coarse-grained grindstone surface “b” is obtained by discharge truing. As a result, a level difference occurs over time, and the fine-grained grindstone surface a does not work.

  Furthermore, in order to make up for the shortcomings of discharge truing, in addition to the discharge truing device, it was considered that a mechanical or contact type truing device could be installed on the centerless grinding machine at the same time. Or the apparatus cost will be increased significantly.

  After such trial and error by the inventor, the present invention has been completed.

  That is, according to the present invention, after discharging the truing wheel surface of the grinding wheel, the portion of the grinding wheel surface that grinds the tip shaft portion of the workpiece is similar to the workpiece shape and has a cylindrical truing surface. Since truing tools are used to perform mechanical truing, that is, contact truing, the following effects can be obtained, and the ultra-thin diameter that has been difficult or impossible in the past has been obtained without detracting from the advantages of discharge truing. It is possible to provide truing technology that can grind workpieces.

(1) In the contact type truing according to the present invention, a truing tool having the same rotation axis as the work to be processed, that is, a truing tool with a shaft similar to the work shape and having a cylindrical truing surface, is used. A straight portion of the surface, that is, a cylindrical grinding surface portion, which is a finishing section for grinding the tip shaft portion of the workpiece, is finished straight with respect to the workpiece, and the tips of the abrasive grains at this portion are aligned. As a result, the surface roughness of the tip shaft portion of the workpiece to be processed becomes good (surface roughness is improved), and the tip shaft portion having an extremely small diameter can be ground.

(2) As described above, the straight part of the grinding wheel surface of the grinding wheel has a uniform abrasive grain tip, so that the processed surface of the tip shaft part of the workpiece is finished cleanly.

(3) The tapered cylindrical surface portion that grinds the tapered portion on the grinding wheel surface of the grinding wheel, that is, the tapered surface portion that is the boundary portion between the tip shaft portion and the base shaft portion of the workpiece is subjected to discharge truing and has good sharpness. Therefore, the grinding speed can be increased.

(4) Further, as the truing tool with a shaft, a tool in which at least the reference shaft portion has the same outer diameter as that of the base shaft portion serving as a machining reference of the workpiece, and further, a tool having the same overall shape as the workpiece is adopted. Thus, in the case of contact truing, this truing tool is set in place of the workpiece, so that the same automatic loader as that during workpiece grinding can be used, and finishing truing can be automated.

  In addition, according to the centerless grinding method of the present invention, the effect of the truing method is exhibited, and the effect of push-through feed grinding is also exhibited. Even if the workpiece is extremely small, it is possible to accurately control the longitudinal direction of the workpiece, that is, the axial dimension, and the tip shaft portion of the workpiece is ground based on the outer diameter of the workpiece base shaft portion. It is possible to grind the stepped workpiece W in a short time while ensuring a high degree of coaxiality and cylindricity with little blurring of the center.

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

  1 to 4 show a centerless grinder according to the present invention. Specifically, this grinder has a large-diameter base shaft portion as shown in FIG. This is a so-called push-through feed type that performs centerless grinding into a stepped shape having Wa and a small-diameter tip shaft portion Wb. This centerless grinding machine is configured to grind only the tip shaft portion Wb (a two-stage structure comprising a minimum diameter shaft portion Wb1 and a small diameter shaft portion Wb2) of the workpiece W. The grinding wheel 1, the adjustment wheel 2, and the blade 3 The pressure roller 4, the work pusher 5 and the truing device 6 are configured as main parts.

  The grinding wheel 1 grinds the outer peripheral surface of the tip shaft portion Wb of the workpiece W, and the grinding wheel surface 10 is the final shape of the tip shaft portion Wb of the workpiece W, that is, the tip shaft portion Wb (Wb1, Wb2). A profile corresponding to the final finished shape of the outer peripheral surface is provided. Specifically, the grinding wheel surface 10 of the grinding wheel 1 is a cylindrical grinding surface (a cross-sectional contour is straight) 10a for grinding the tip shaft portion Wb of the workpiece W, and a boundary portion between the tip shaft portion Wb and the base shaft portion Wa. A tapered cylindrical surface 10b (having a tapered cross-sectional profile) for grinding the tapered surface portion Wc.

  The grinding wheel surface 10 of the grinding wheel 1 is composed of a conductive grinding wheel to which discharge truing is applied. This conductive grindstone is formed by bonding so-called superabrasive grains such as fine diamond grains and CBN (cubic boron nitride) grains by a conductive bonding material such as a conductive resin bond or a metal bond. The grindstone surface 10 made of such a conductive grindstone has a strong holding power of abrasive grains and is unlikely to be deformed. Further, the shape is corrected by discharge truing, so that the protruding amount of the abrasive grains is sufficient. Takes off and has a good sharpness.

  The grinding wheel 1 has a conventionally known general basic structure. That is, the grinding wheel 1 is detachably mounted and fixed to the grinding wheel shaft 11, and is rotatably supported on a grinding wheel base (not shown) on which the grinding wheel shaft 11 is fixedly mounted. It is drivingly connected to a driving source such as a driving motor through a power transmission means such as a gear mechanism.

  The adjustment wheel 2 rotates and supports only a shaft portion that is not a grinding target of the workpiece W, that is, a large-diameter base shaft portion Wa that serves as a processing reference. The workpiece W is disposed at a position shifted in the axial direction. The adjusting wheel 2 has a conventionally known general basic structure. That is, the adjustment wheel 2 is detachably attached and fixed to the adjustment axle 12, and the adjustment axle 12 is rotatably supported on the adjustment carriage (not shown), and power transmission means such as a power transmission belt and a gear mechanism. Via a drive source such as a drive motor.

  In the illustrated embodiment, the axis of the adjusting wheel 2, that is, the axis of the adjusting wheel 12 is arranged in the direction opposite to the workpiece W by the cooperative action with the pressing means 15 described later (in FIG. It is set so as to give a thrust in the direction opposite to the feed direction X of W). With such an arrangement configuration of the adjusting wheel 2, in cooperation with the work pusher 5 described later, the work pusher 5 forcibly feeds the work W in the feed direction X and realizes speed control thereof, and The reciprocating operation of the truing tool 30 with a shaft, which will be described later, and the speed control thereof are realized by the reciprocating movement of the work pusher 5 in the axial direction.

  As shown in FIG. 2, the blade 3 supports the base shaft portion Wa of the work W together with the adjustment wheel 2, and is installed on the adjustment carriage like the adjustment wheel 2. An inclined support surface 3a for supporting from below is provided.

  The pressure roller 4 is a main part of the pressing means 15 that presses and supports the large-diameter shaft portion Wa of the workpiece W against the rotation support surface 2a of the adjustment wheel 2 together with the elastic urging means 14, and the roller shaft 16 Is supported so as to be freely rotatable. The pressure roller 4 is disposed so as to face the adjusting wheel 2 and can be brought into rolling contact with the outer peripheral surface of the base shaft portion Wa of the work W, and the base portion of the work W by the elastic biasing means 14. The outer circumferential surface of Wa is configured to be constantly and resiliently pressed with a predetermined pressing force.

  The pressure roller 4 of the pressing means 15 elastically presses and supports the base shaft portion Wa of the work W against the adjustment wheel 2 and cooperates with the rotation wheel 2 to adjust the work W. The thrust in the reverse feed direction is given to the workpiece W while forcibly rotating.

  The work pusher 5 is a main part of the feeding means 20 for forcibly feeding the workpiece W in the axial direction, that is, the feeding direction X on the grinding wheel 1 side. Although not specifically illustrated, the work pusher 5 is disposed substantially coaxially with the work W supported by the adjusting wheel 2 and the blade 3 and is supported so as to be movable in the axial direction of the work W. Yes. The work pusher 5 is drivingly connected to a moving means (not shown). As the moving means for reciprocating the work pusher 5 in the axial direction, a linear motor or a conventionally known feed driving device provided with a feed screw mechanism is appropriately employed.

  Then, the leading end 5a of the work pusher 5 is brought into contact with the rear end surface of the base shaft portion Wa of the work W by the feeding means, and the work W is moved at a predetermined speed in the axial direction (feeding direction) X by a predetermined distance. Just send in. In this case, in the present embodiment in which the adjusting wheel 2 is inclined so as to give a thrust in the counterfeed direction to the workpiece W, the workpiece pusher 5 moves the workpiece W in the feeding direction X against the thrust action. The feed is forcibly sent at a predetermined feed speed.

  The truing device 6 applies truing to the grinding wheel surface 10 of the grinding wheel 1 periodically or at an appropriate interval. Specifically, the discharging truing part 21 shown in FIG. 3 and the contact type truing shown in FIG. It is in the form of a composite truing device comprising the section 22.

  The discharge truing portion 21 discharges the entire grinding wheel surface 10 (10a, 10b) of the grinding wheel 1 and the discharge truer 25 is disposed on the opposite side of the adjustment wheel 2 with respect to the grinding wheel 1.

  As the discharge truer 25, a discharge trueing electrode in the form of a disk-like truer is preferably employed, and the discharge truer 25 of the illustrated embodiment has an extremely thin disk shape with a thickness of 1 mm or less. The narrow outer peripheral surface 25a is a truing surface.

  Although not specifically shown, the discharge truer 25 is rotatably supported by the truer base via the truer shaft 26 arranged in parallel with the grinding wheel axle 11, and is rotationally driven via a power transmission mechanism. Linked to the source. Thereby, the discharge truer 25 is rotationally driven in a state in which the truing surface 25 a is disposed to face the grinding wheel surface 10 of the grinding wheel 1. The above-mentioned truer base is moved along the outer peripheral contour of the grinding wheel surface 10 of the grinding wheel 1 by moving means (not shown), and the discharge truer 25 is traversed so as to have a profile corresponding to the shape of the grinding wheel 1.

  In addition, the discharge truer 25 is electrically connected to the (−) pole of the power supply 28 via the power supply body 27 and serves as a (−) pole discharge truing electrode. Correspondingly, the grinding wheel 1 is electrically connected to the (+) pole of the power supply 28 via the power supply body 29.

  Then, according to the properties of the grinding wheel surface 10 of the grinding wheel 1, the discharge truer 25 is rotationally driven by the truer shaft 26 and traverses in the axial direction of the grinding wheel 1 along the outer peripheral contour of the grinding wheel surface 10 of the grinding wheel 1. On the other hand, a direct current is passed through the grinding wheel 1 and the discharge truer 25, whereby the conductive bonding material portion of the grinding wheel surface 10 is melted and removed by a discharge action to form a chip pocket. The discharge truing by the discharge truing unit 21 can be executed either when the grinding wheel 1 is stopped or during grinding.

  The contact truing portion 22 mechanically trues a portion of the grinding wheel surface 10 of the grinding wheel 1 for grinding the tip shaft portion Wb of the workpiece W, that is, the cylindrical grinding surface 10a, and is similar to the shape of the workpiece W. The attached truing tool 30 is configured as a main part.

  Specifically, the contact type truing unit 22 places the truing tool 30 with the shaft in the same state as when the workpiece W is ground, that is, the centerless grinder grinds the truing tool 30 with the shaft by push-through feed. By operating, the cylindrical grinding surface 10a of the grinding wheel 1 is mechanically trued.

  The truing tool 30 with a shaft is similar in shape to the shape of the workpiece W, and includes a truing portion 31 for truing the cylindrical grinding surface 10a of the grinding wheel 1, and the outer peripheral surface of the truing portion 31 has the above grinding wheel. A cylindrical truing surface (cross-sectional contour is straight) 31 a corresponding to the grinding wheel surface 10 of the vehicle 1 is used.

  As shown in FIG. 4, the specific shape of the truing tool 30 with a shaft includes a reference shaft portion 30 a having a shape corresponding to the large-diameter base shaft portion Wa of the workpiece W, and a tip shaft portion Wb to be ground on the workpiece W. And a truing portion 31 integrally provided at the tip of the support shaft portion 30b. These portions 30a, 30b and 31 are formed coaxially. Has been.

  In the truing tool 30 with a shaft of the illustrated embodiment, at least the outer diameter size of the reference shaft portion 30a is set to be the same as the outer diameter size of the base shaft portion Wa serving as a processing reference of the workpiece W. The truing portion 31 has a length L set larger than a width l of the grinding wheel surface 10 of the grinding wheel 1 and an outer diameter of the tip W W of the workpiece W. (It is not limited to the same dimension as the outer diameter dimension of the distal end shaft portion Wb, and in the illustrated case, it is set larger than the outer diameter dimension of the distal end shaft portion Wb). The cylindrical truing surface 31a of the truing portion 31 is formed by a diamond abrasive grain bonded by a bonding material, and is in the form of a rotary diamond dresser.

  Then, when the truing tool 30 with a shaft is set on a centerless grinding machine instead of the workpiece W in accordance with the properties of the cylindrical grinding surface 10a of the grinding wheel 1, the truing tool 30 with a shaft moves on the blade 3 like the workpiece W. Then, the cylindrical grinding surface 10a of the grinding wheel 1 is mechanically trued. The contact type truing by the truing tool 30 with the shaft can be executed while the grinding wheel 1 is stopped or during the grinding process as in the case of the above-described electric discharge truing. Truing is performed by appropriately interposing between the workpieces W, W,.

  Thus, in the centerless grinding machine configured as described above, the workpiece W is forcibly rotated and the forcibly rotated by the base shaft portion Wa of the workpiece W being pressed against and supported by the adjusting wheel 2 by the pressing means 15. The workpiece W is fed in the axial direction (feed direction) X by the feeding means 20, whereby the tip shaft portion Wb of the workpiece W is ground by the grinding wheel 1. Specifically, this grinding step includes the following steps.

(1) In the state where the grinding wheel 1 is set and arranged corresponding to the finished dimension of the minimum diameter shaft portion Wb1 of the tip shaft Wb of the workpiece W, the grinding wheel 1 and the adjustment wheel 2 are each rotationally driven at a predetermined rotational speed. At the same time, as the work pusher 5 advances in the feed direction X, the bar-like work W is supplied to the position of the adjusting wheel 2 along the inclined support surface 3a (see FIG. 2) of the blade 3. . Then, as a result of the pressure roller 4 of the pressing means 15 pressing the workpiece W against the adjusting wheel 2 with a predetermined elastic biasing force, the workpiece W is forcibly rotated by the rotating force of the adjusting wheel 2 ((( 1)).

(2) Further, the work pusher 5 advances, so that the work W is sent in the axial direction X, and the tip shaft portion is sent into the grinding wheel 1. In this case, only the base shaft portion Wa of the workpiece W is rotationally supported by the adjusting wheel 2 and the blade 3 by the pressing force of the pressure roller 4, and the tip side outer peripheral surface of the tip portion Wb of the workpiece W is the grinding wheel 1. To form a cylindrical portion and a tapered portion of the minimum diameter shaft portion Wb1 as shown in FIG.

  The mechanism of the grinding process in this case is as follows. First, the tip of the workpiece W comes into contact with the tapered cylindrical surface 10b of the grinding wheel 1 to start grinding, and the tip shaft portion Wb of the workpiece W is fed in accordance with the feeding of the workpiece W by the workpiece pusher 5. The minimum diameter shaft portion Wb1 is ground to a preset shape dimension. In other words, in the workpiece W, the outer peripheral surface of the minimum diameter shaft portion Wb1 is ground by the grinding wheel 1 with reference to the outer diameter of the base shaft portion Wa supported by the pressure roller 4 and the adjustment wheel 2. At this time, the minimum diameter shaft portion Wb1 of the workpiece W fed while being ground is not supported by the rotation support surface 2a of the adjustment wheel 2 as shown in (2) of FIG. is there.

(3) When the workpiece W is fed to a predetermined position in the axial direction and the minimum diameter shaft portion Wb1 of the workpiece W is ground into a predetermined final finish shape, the grinding wheel 1 is moved to the workpiece by the workpiece pusher 5. The workpiece W is fed to a predetermined position in the axial direction thereof (see (3) in FIG. 5) while moving backward (negative cutting operation) in synchronization with the feeding operation of W.

(4) The minimum diameter of the workpiece W by the advancement of the workpiece pusher 5 in the feed direction X in a state where the grinding wheel 1 is retracted corresponding to the finished dimension of the small-diameter shaft portion Wb2 on the tip shaft Wb of the workpiece W. The outer peripheral surface of the portion following the shaft portion Wb1 is ground by the grinding wheel 1 to form a cylindrical portion and a tapered portion of the small diameter shaft portion Wb2 as shown in FIG. The mechanism of the grinding process in this case is the same as that described in the process (2).

(5) When the workpiece W is fed to a predetermined position in the axial direction and the small-diameter shaft portion Wb2 of the workpiece W is ground into a predetermined final finished shape, the grinding wheel 1 is moved to the workpiece W by the workpiece pusher 5. The workpiece W is fed to a predetermined position in the axial center direction (see (5) in FIG. 5) while moving backward (negative cutting operation) in synchronization with the feeding operation.

(6) Further, the work wheel W is fed to a predetermined position in the axial direction while the grinding wheel 1 is moved backward in synchronization with the work W feeding operation by the work pusher 5 (see (5) in FIG. 5). Then, the grinding wheel 1 is completely separated from the workpiece W to complete the grinding process (see (6) in FIG. 5).

(7) The workpiece W having the tip shaft portion Wb (two-stage structure comprising the minimum diameter shaft portion Wb1 and the small diameter shaft portion Wb2) thus ground is removed from the grinding wheel 1 and the adjustment wheel by a discharge means (not shown). It is discharged from the processing position between the two.

(8) Returning to the step (1) again, the same operation is repeated thereafter.

  Further, the truing device 6 is executed at any time during the grinding process or while the grinding process is stopped at regular intervals or at appropriate intervals according to the properties of the grinding wheel surface 10 of the grinding wheel 1. In this truing, the composite truing by the discharge truing part 21 and the contact truing part 22 of the truing apparatus 6 is performed at any time on the grinding wheel surface 10 of the grinding wheel 1. This truing process is specifically performed in the following processes, and in the illustrated embodiment, it is performed in-process during grinding of the grinding wheel 1.

A. Discharge truing:
The discharge truing portion 21 discharges the entire grinding wheel surface 10 of the grinding wheel 1 as described above (see FIG. 3).

B. Contact truing:
Subsequently, the cylindrical grinding surface 10a for grinding the tip shaft portion Wb (Wb1, Wb2) of the workpiece W in the grinding wheel surface 10 is mechanically trued by the contact truing portion 22 as follows (see FIG. 4). ).

(1) Instead of the workpiece W, the truing tool 30 with a shaft is placed and set on the blade 3 of the centerless grinding machine.
(2) The adjustment wheel 2 is rotated and the truing tool 30 with the shaft is rotated.
(3) Only the cylindrical grinding surface 10a of the grinding wheel surface 10 of the grinding wheel 1 is mechanically operated by cutting the grinding wheel 1 to be rotated relative to the cylindrical truing portion 31 of the truing tool 30 with a shaft. Truing (contact truing).
(4) In this state, the truing tool 30 with a shaft is reciprocated in the axial direction by the work pusher 5 to finish the cylindrical grinding surface 10a of the grinding wheel 1 straight.

  Further, the contact type truing is appropriately interposed between the workpieces W, W,... That are continuously processed, so that the truing tool 30 with the shaft moves on the blade in the same manner as the workpiece W, so that the cylindrical grinding of the grinding wheel 1 is performed. It is also possible to mechanically true the surface 10a (see FIG. 4).

  That is, the base truing tool 30 of the shafted truing tool 30 is placed on the blade 3 of the centerless grinding machine by supplying the truing tool 30 with the shaft appropriately interposed between the workpieces W, W,. At the same time, the base shaft portion 30a is pressed against and supported by the adjusting wheel 2 by the pressure roller 4 of the pressing means 15, and the grinding wheel 1 is driven by the work pusher 5 of the feeding means 20 while the truing tool 30 with the shaft is forcibly rotated. The cylindrical grinding surface 10a of the grinding wheel 1 is mechanically trued by the cylindrical truing surface 30a of the cylindrical truing portion 31 of the truing tool 30 with a shaft.

  With the above configuration, that is, after the grinding wheel surface 10 of the grinding wheel 1 is discharge-truded, the cylindrical grinding surface 10a for grinding the tip shaft portion Wb of the workpiece W of the grinding wheel surface 10 is replaced with the workpiece. By using a truing tool 30 with a shaft similar to the shape of W and having a cylindrical truing surface 31a, that is, mechanically performing contact truing, it is difficult or impossible in the past without impairing the advantages of discharge truing. It was possible to grind even the tip shaft portion Wb of the workpiece W having an extremely small diameter (0.05 mm or less, for example, 0.02 mm diameter) such as a micro drill.

  In particular, in contact truing by the contact truing part 22, a grinding wheel is used for truing with a truing tool 30 with a shaft having the same rotational axis as the workpiece W, that is, a reference shaft part 30a, and a cylindrical truing surface 31a. The cylindrical grinding surface 10a, which is a straight section on the grinding wheel surface 10 of the vehicle 1, that is, the finishing section for grinding the tip shaft portion Wb of the workpiece W, is finished straight with respect to the workpiece, and the abrasive grain tips of the cylindrical grinding surface 10a are aligned. become. As a result, the surface roughness of the tip shaft portion Wb of the workpiece W to be processed becomes good (the surface roughness is improved), and the tip shaft portion Wb having an extremely small diameter can be ground.

  In other words, in the case of an extremely thin workpiece W, the surface roughness of the processed surface becomes an element that acts as a crack as it is, and the roughness element that acts as a crack is improved by improving the surface roughness. Therefore, processing with an extremely small diameter becomes possible.

  In addition, as described above, when the straight portion (cylindrical grinding surface) 10a of the grinding wheel surface 10 of the grinding wheel 1 has the abrasive grain tips aligned, the processed surface of the tip shaft portion Wb of the workpiece W is finished cleanly.

  The tapered cylindrical surface 10b for grinding the tapered portion of the grinding wheel surface 10a of the grinding wheel 1, that is, the tapered surface portion Wc that is the boundary portion between the tip shaft portion Wb and the base shaft portion Wa of the workpiece W is subjected to discharge truing. Since the sharpness is good, the grinding speed can be increased.

  Furthermore, according to the centerless grinding method described above, the effect of the truing method is exhibited, and the effect of push-through feed grinding is also exhibited. By these synergistic effects, the diameter of the tip shaft portion Wb of the workpiece W is achieved. Even if the dimension is extremely small, the grinding longitudinal direction of the workpiece W, that is, the dimension in the axial direction can be accurately controlled, and the tip shaft portion Wb of the workpiece W is ground based on the outer diameter of the base shaft portion Wa. It is possible to grind the stepped workpiece W in a short time while ensuring a high degree of coaxiality and cylindricity while there is little blurring of the axis of the workpiece W.

  The above-described embodiment is merely a preferred embodiment of the present invention, and the present invention is not limited thereto, and various design changes can be made within the scope.

  For example, as the truing tool 30 with a shaft, it is possible to adopt the same overall shape as that of the workpiece W. With such a configuration, a shaft instead of the workpiece W can be used in contact truing. The attached truing tool 30 can be transported by an automatic loader, and finishing truing can be automated.

It is a schematic plan view which shows the centerless grinding machine which is Embodiment 1 of this invention, and has shown the state which grinds a rod-shaped workpiece | work. FIG. 2 is a sectional view of the same centerless grinding machine taken along line AA in FIG. 1. It is a schematic block diagram which shows the discharge truing part of the truing apparatus of the centerless grinding machine. It is a schematic plan view corresponding to FIG. 1 which shows the contact-type truing part of the truing apparatus of the centerless grinding machine. It is process explanatory drawing for demonstrating the process which grinds the rod-shaped workpiece | work by the centerless grinding machine to a stepped shape. In a conductive grinding wheel that is discharge-truded, the cylindrical grinding surface that grinds the tip shaft part of the workpiece is a fine-grained grinding wheel surface with fine grain size, and the taper that grinds the boundary part between the tip shaft part and the base shaft part It is a top view for demonstrating time-dependent deformation | transformation by discharge truing in the case of making a cylindrical surface into the coarse-grained grindstone surface provided with the coarse grain size abrasive grain.

Explanation of symbols

W Work Wa Base shaft portion Wb Tip shaft portion Wc Tapered surface portion X Workpiece feed direction 1 Grinding wheel 2 Adjustment wheel 2a Rotating support surface 3 Blade 3a Inclined support surface 4 Pressure roller 5 Work pusher 6 Truing device 10 Grinding wheel surface 10a Cylindrical grinding surface 10b Tapered cylindrical surface 15 Press means 20 Feed means 21 Discharge truing portion 22 Contact truing portion 25 Discharge truer 25a Truing surface 30 Truing tool with shaft 30a Reference shaft portion 30b Support shaft portion 31 Cylindrical truing portion 31a Cylindrical truing surface

Claims (6)

In a centerless grinding machine for centerless grinding the tip shaft portion of the rod-shaped workpiece into a stepped shape by a conductive grinding wheel having a profile corresponding to the final shape of the tip shaft portion of the rod-shaped workpiece, the grinding wheel surface of the grinding wheel is A truing method,
After the discharge truing of the grinding wheel surface of the grinding wheel, a portion of the grinding wheel surface for grinding the tip shaft portion of the workpiece is obtained using a truing tool with a shaft similar to the workpiece shape and having a cylindrical truing surface. A truing method in a centerless grinder for a bar-shaped workpiece characterized by mechanically truing. The mechanical truing by the truing tool with a shaft is carried out by placing the truing tool with a shaft on a blade of a centerless grinder and rotating the grinding wheel that is driven to rotate while the truing tool with a shaft is rotated by an adjusting wheel. 2. The bar-shaped tool according to claim 1, wherein a portion of the grinding wheel surface of the grinding wheel to be ground is trued by performing a cutting operation relative to the attached truing tool. Truing method for centerless grinding machines. Mechanical truing by the truing tool with a shaft is performed by placing a reference shaft portion of the truing tool with a shaft on a blade of a centerless grinding machine and pressing and supporting the reference shaft portion against the adjusting wheel by a pressing means. The grinding wheel is moved by the cylindrical truing surface of the truing tool with the shaft by feeding the truing tool with the shaft relative to the grinding wheel in the axial direction by the feeding means while forcibly rotating the truing tool with the shaft. 3. A truing method in a centerless grinding machine for a bar-shaped workpiece according to claim 1 or 2, wherein a portion of the grindstone surface for grinding the tip shaft portion of the workpiece is ground. 4. The truing in the centerless grinding machine for a bar-shaped workpiece according to claim 3, wherein the truing tool with a shaft has at least the reference shaft portion having the same outer diameter as a base shaft portion serving as a machining reference of the workpiece. Method. 5. The bar-shaped workpiece according to claim 1, wherein the discharge truing uses a truer as a discharge truing electrode to discharge the entire grinding wheel surface of the grinding wheel. Truing method for centerless grinding machines. A centerless grinding method for centerless grinding the tip shaft portion of the rod-like workpiece into a stepped shape by a conductive grinding wheel having a profile corresponding to the final shape of the tip shaft portion of the rod-like workpiece,
By pressing and supporting the base shaft portion of the workpiece against the adjusting wheel by the pressing means, the workpiece is forcibly rotated, and the workpiece is fed relative to the grinding wheel by the feeding means in the axial direction. While grinding the tip shaft part of the wheel with a grinding wheel,
A centerless grinding method for a bar-shaped workpiece, wherein truing is performed on the grinding wheel surface of the grinding wheel periodically or at an appropriate interval by the truing method according to any one of claims 1 to 5.

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