JP2005319553A - Centering and machining method of workpiece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centering and machining method of a workpiece, in which centering is carried out with reference to a bore of a workpiece simultaneously with machining of the bore, correction of inevitable relative displacement between a table of a machining device and a main shaft in order to ensure machining accuracy is not required, and the dimensional accuracy of each workpiece can be stabilized by carrying out a machining procedure each time under almost constant conditions without positional corrections. <P>SOLUTION: According to the centering and machining method, a centering jig 1 equipped with a centering member 3 having a taper cone 3a is mounted on the main shaft 5 of the machining device, and the centering jig 1 is fitted into the bore of the workpiece 10 to position the workpiece 10 to the center of the main shaft with reference to the main shaft 5, followed by clamping the workpiece 10 and fixing the same to a work holder 6 while the centering jig 1 is left as it is. Thereafter a tool is mounted on the main shaft 5 in place of the centering jig 1, and then the bore of the workpiece and an area with reference to the bore are machined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for centering a workpiece that makes it possible to accurately process a sintered part having a shaft hole.

  For example, sintered sprocket wheels are manufactured by machining a central shaft hole (inner diameter hole) or a peripheral small hole as a finish, and shipping the processed product as a product. FIG. 3 shows an example of a sintered sprocket wheel. In the illustrated sintered sprocket wheel, the inner diameter hole 11, the peripheral small holes 12 and 13 and the key groove 14 whose center is the center of the inner diameter hole 11 are processed.

  For machining, a machining center is used for mass-produced products, and a workpiece 10 such as a sintered sprocket wheel is held by an inner diameter chuck C provided on the table side as shown in FIG. The part is being processed.

  When the workpiece has a boss portion and can be gripped from the outside, the target portion may be processed by gripping the boss portion with an outer diameter chuck.

  When the workpiece is gripped by the outer diameter chuck, positioning is performed on the basis of the outer diameter. For this reason, a workpiece whose inner and outer diameters are not concentric is poor in positional accuracy on the basis of the inner diameter of the processing site. Therefore, when the position accuracy on the inner diameter reference of the processing part is required, a method of holding the workpiece with the inner diameter chuck is used. However, if the inner diameter chuck is used, the workpiece must be grasped when machining the inner diameter hole. In other words, there arises a problem of a decrease in productivity and an increase in processing cost.

  Further, in machining performed using a machining center or the like, machining conditions change over time. A deviation occurs between the spindle and the table due to the influence of temperature change or the positioning accuracy of the work holder, and the machining pitch fluctuates accordingly.

  In order to eliminate the problem of accuracy degradation due to this, conventionally, the processed workpiece is sampled and checked to check the fluctuation status of the machining pitch, and when it is judged that correction is necessary, the relative position between the spindle and the table is corrected. Is carried out several times a day.

  However, this method takes time and labor for sampling inspection and position correction. Further, since deviations are accumulated until correction is performed, variation in dimensional accuracy of the product (variation within an allowable value) also increases.

Here, the following Patent Document 1 discloses a positioning clamp device in which a pallet is installed on a turning table, and the position of the pallet is controlled by a linear actuator to change the position of the workpiece on the pallet. If the positioning clamp device of this patent document 1 or a work holder having a function similar to this is used, the correction work can be automated, but in the correction by sampling inspection several times a day, the correction work is performed. It is affected by the accumulation of deviations. Moreover, since the positioning clamp apparatus as shown in Patent Document 1 is expensive, the economic burden increases.
Japanese Patent Application Laid-Open No. 08-057536

  The present invention eliminates the need for conventional position correction to cope with thermal displacement, etc., stabilizes the dimensional accuracy of the workpiece by making the machining conditions almost constant, and increases the economic burden. The goal is to eliminate restrictions on internal diameter machining.

In order to solve the above problems, in the present invention, a process of mounting a centering jig having a tapered taper outer peripheral surface to the main spindle of the processing machine,
The process of positioning the workpiece centered on the spindle with reference to the spindle by fitting the centering jig attached to the spindle of the processing machine into the bore of the workpiece,
Clamping the positioned workpiece with the centering jig remaining and fixing it to the workpiece holder,
Provided is a workpiece centering method in which a tool is mounted on the spindle of a processing machine in place of the centering jig, and the inner diameter hole of the workpiece or a portion where the inner diameter hole serves as a position reference is processed with this tool.

  In this method, it is preferable that the centering jig is urged by an elastic body, and the outer peripheral surface of the taper taper is elastically pressed against the inlet portion of the inner diameter hole of the workpiece to be fitted.

  Also, after placing the workpiece on the seating surface provided in the workpiece holder, centering and positioning with the centering jig, the workpiece is sandwiched and fixed between the seating surface and the workpiece presser opposed thereto, It is more preferable to adopt a method in which the support of the work by the seating surface is a local support, the outer periphery of the work is surrounded by a peripheral wall provided on the work holder, and the work is centered by a centering jig in this state.

  According to the method of the present invention, since the inner diameter hole of the workpiece is positioned at the center of the spindle and the machining is performed on the basis of the inner diameter hole, the positional accuracy on the basis of the inner diameter of the processed part is increased. In addition, since the workpiece is positioned for each workpiece, even if there is a deviation in the relative position between the workpiece holder and the spindle provided on the table of the processing machine, it will not be affected, and the machining conditions will be constant and the dimensions and quality of the product will be fixed. The variation of the is suppressed small.

  Furthermore, according to the method of the present invention, since the workpiece is centered before clamping, the centering can be performed with an inexpensive centering jig. In addition, since the centering jig is replaced with a tool after the positioning, the inner diameter hole can be processed without gripping the workpiece.

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings. FIG. 1 shows an example of a centering jig used in the present invention. The centering jig 1 includes an attachment portion 2 to be inserted into a main shaft of a processing machine (machining center), a centering member 3 held by the attachment portion 2 so as to be slidable in the axial direction, and the centering member 3 from the attachment portion 2. The spring 4 is configured to urge the centering member 3 in the pushing direction.
Although a spring is used here, the biasing means may be a fluid damper such as rubber or air, a fluid cylinder such as air, or the like.

  The centering member 3 has a tapered taper cone 3a having a tapered surface concentric with the shaft at the outer periphery at the front.

  A method for centering and processing a workpiece using the centering jig 1 will be specifically described below.

  As shown in FIG. 2, the centering jig 1 is mounted on the spindle 5 of the processing machine. A work holder 6 is provided on a table (not shown) of the processing machine, and a work 10 to be processed is placed on the work holder 6.

  The work holder 6 holds a workpiece 10 between the seating surface 7 that receives and supports one surface of the workpiece 10 from below, a peripheral wall 8 that surrounds the outer periphery of the workpiece 10, and the seating surface 7 facing the seating surface 7. 9 and. The work presser 9 has driving means (not shown) for clamping and unclamping, and is moved by being driven by the driving means.

  When the workpiece 10 is placed on the seating surface 7 of the workpiece holder 6, the spindle 5 of the processing machine is lowered. As a result, the taper cone 3a of the centering jig 1 attached to the spindle 5 is inserted into the inner diameter hole of the workpiece 10 as shown by a chain line in FIG. Thus, the workpiece 10 is positioned at a position based on the axis of the main shaft 5 by the action of the tapered surface.

Thereafter, the spring 4 is compressed, a switch (not shown) is actuated, for example, when the relative movement amount of the centering member 3 and the mounting portion 2 reaches a specified value, and the workpiece 10 is clamped by the workpiece presser 9. Is fixed to the work holder 6.
Here, the workpiece 10 may be positioned while the taper cone 3a is rotated by the spindle 5 at an extremely low speed that does not cause sliding wear on the inner diameter hole of the workpiece 10 and the taper cone 3a.

  Therefore, the spindle 5 is once raised, the centering jig 1 mounted on the spindle 5 is replaced with a tool, and the workpiece is processed with a tool attached to the spindle. The machining is performed on an inner diameter hole or a small hole around the inner diameter hole, and a tool corresponding to the machining content is replaced and used.

  When the machining is completed, the workpiece holder 9 is unclamped, the workpiece 10 is removed, a new workpiece is set, and the above operation is repeated.

  According to this method, it is necessary to attach and detach the centering jig 1 to and from the spindle 5 every time one workpiece is machined. However, recent machining centers can perform tool change in less than 1 second. Has emerged and has little impact on productivity.

  Further, in this method, since all the workpieces are positioned on the basis of the spindle, the machining accuracy is not affected even if a relative displacement between the table and the spindle occurs. For example, with respect to the sintered sprocket wheel of FIG. 3, the inner diameter chuck method and the chuck method according to the method of the present invention can obtain the same or better accuracy for the pitch P from the center of the inner diameter hole 11 to the center of the small hole 12. Became.

  If the seat surface 7 of the work holder is a partially raised surface as shown in FIG. 2, the support area of the work is small, and the work is easily slipped when centering, so that the centering is smoothly performed. Further, when the area of the seat surface 7 is reduced, it is difficult to cause a problem that a burr generated on the end surface of the workpiece rises on the seat surface 7 and the workpiece holding posture is lost.

Sectional drawing which shows an example of the centering jig used with the method of this invention Sectional drawing which shows the centering state by the method of this invention Sectional view showing an example of a workpiece Sectional view of workpiece held by inner diameter chuck

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centering jig 2 Mounting part 3 Centering member 3a Taper cone 4 Spring 5 Spindle 6 Work holder 7 Seat surface 8 Peripheral wall 9 Work holding 10 Work 11 Inner diameter hole 12, 13 Small hole 14 Keyway

Claims (4)

A process of mounting a centering jig having a tapered taper outer peripheral surface to the spindle of the processing machine,
The process of positioning the workpiece centered on the spindle with reference to the spindle by fitting the centering jig attached to the spindle of the processing machine into the bore of the workpiece,
Clamping the positioned workpiece with the centering jig remaining and fixing it to the workpiece holder,
A work centering method in which a tool is mounted on a spindle of a processing machine in place of the centering jig, and the inner diameter hole of the work or a portion where the inner diameter hole serves as a position reference is processed with this tool.   The work centering method according to claim 1, wherein the centering jig is urged by an elastic body, and the outer peripheral surface of the tapered taper is elastically pressed and fitted to an inlet portion of an inner diameter hole of the work.   The workpiece is placed on a seating surface provided in a workpiece holder, centered by the centering jig and positioned, and then the workpiece is sandwiched and fixed by the seating surface and a workpiece presser opposed thereto. 2. The work centering method according to 2 above.   The support of the workpiece by the seating surface is a local support, and the outer periphery of the workpiece is surrounded by a peripheral wall provided on the workpiece holder, and the workpiece is centered by a centering jig in this state. The workpiece centering method described.

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