JP2012006130A - Milling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a milling method by which a workpiece of precise flatness can be obtained at low cost.SOLUTION: With a workpiece W held by a clamp part 10 and a natural clamp part 20, a machining surface F of the workpiece W is subjected to a first milling process. Then, the natural clamp part 20 is temporarily receded from the workpiece W, and is arranged at an optimum position relative to the workpiece W anew. Under this condition, the machining surface F of the workpiece W is subjected to a second milling process.

Description

  The present invention relates to a milling method, and in particular, a method for milling a thin workpiece with high flatness.

  In performing milling, as a means for fixing a workpiece, a fixing method using a clamp that clamps and fixes the workpiece and a natural clamp that supports the workpiece from one side is known.

  For example, the clamping device disclosed in Patent Document 1 clamps and fixes at least a position from the center in the longitudinal direction of a thin workpiece with a clamp arm and supports the back surface of the workpiece with a natural clamp. By milling the surface of the workpiece in this state, it aims to process a thin workpiece with high flatness.

Japanese Patent Laid-Open No. 10-202456

  However, even if milling is performed using the clamping device as described above, it cannot be said that the flatness of the workpiece can be sufficiently increased, and further contrivance is required.

  By the way, when trying to finish a workpiece to the desired flatness by only one milling, the amount of workpiece cutting per machining increases, so it is difficult to obtain the accuracy of the workpiece surface and the burden on the milling tool. Becomes larger. For this reason, milling is generally performed in a plurality of times.

  However, even when milling is performed in multiple steps, it is difficult to increase the flatness of the workpiece for the following reasons. That is, prior to milling, the workpiece is supported by the clamping device. Specifically, the workpiece is clamped and fixed by the clamp portion, and the natural clamp portion is brought close to the workpiece and arranged at an optimum position for supporting the workpiece. The optimum position of the natural clamp part varies depending on the shape and material of the work, the place where milling is performed, the position of the clamp part, etc., for example, it is placed at a position where it abuts on the work or a little away from the work. The When the workpiece is first milled in a state in which the workpiece is supported by the clamping device in this manner, the workpiece is distorted, so that the natural clamp portion may be displaced from the optimum position. If the workpiece is subjected to the second milling in this state, the support by the natural clamp portion is not sufficient, and there is a possibility that desired flatness cannot be obtained.

  For example, it is conceivable that the position information of the workpiece is feedback-controlled and the natural clamp portion is always arranged at the optimum position. However, such feedback control causes a significant increase in cost.

  The problem to be solved by the present invention is to provide a milling method capable of obtaining a workpiece with high flatness at low cost.

  In order to solve the above-mentioned problems, the present invention is a method of milling the surface of a workpiece, wherein a clamping step of clamping and fixing the workpiece by a clamp portion and a natural clamp portion are brought close to the workpiece, and an optimum position with respect to the workpiece The natural clamping process that supports the workpiece from one side, the first milling process that mills the surface of the workpiece, and the natural clamping part are once separated from the workpiece and placed in the optimum position for the workpiece again. The re-natural clamping process to be performed and the second milling process for further milling the surface of the workpiece are sequentially performed.

  Thus, in the milling method of the present invention, after finishing the first milling process, the natural clamp part is once separated from the work, and again placed at the optimum position with respect to the work. Thereby, since the 2nd milling process can be performed in the state which supported the work favorably in the natural clamp part, the flatness of the work surface of the work can be increased. Such a milling method is suitably applied to a thin-walled workpiece (for example, an engine timing chain cover) that is liable to cause machining distortion.

  As described above, according to the milling method of the present invention, even a thin workpiece is subjected to a simple process of arranging the natural clamp portion at the optimum position again without providing high-cost feedback control. Just finish the workpiece with high flatness.

(A) is a top view of a workpiece | work (timing chain cover), (b) is the side view which looked at (a) figure from the A direction. (A) is a top view of a milling machine, (b) is the side view which looked at (a) figure from the B direction. It is a side view of the clamp part of the said milling machine. It is a side view of the natural clamp part of the said milling machine. It is a block diagram which shows the procedure of the milling method which concerns on one Embodiment of this invention.

  Hereinafter, a milling method according to an embodiment of the present invention will be described with reference to the drawings.

  In the present embodiment, a method of milling a thin timing chain cover as shown in FIG. The workpiece W is die-cast and milled on a planar processing surface F (shown as dots in FIG. 1 (a)) along the outer edge of the surface (the surface visible in FIG. 1 (a)). Apply. In the present embodiment, a case will be described in which milling is performed with the front surface of the workpiece W facing upward and the back surface facing downward.

  The milling process of this embodiment is performed using the milling machine 1 shown in FIG. The milling machine 1 includes a processing unit 2 that performs milling on the processing surface F of the workpiece W, and a clamp device 3 that holds the workpiece W. In addition, illustration of the process part 2 is abbreviate | omitted in Fig.2 (a).

  As shown in FIG. 2B, the processing unit 2 includes a disk-shaped milling blade 2 a and a motor 2 b that rotationally drives the milling blade 2 a around a rotation axis in the vertical direction. The processing unit 2 is movable in the vertical direction and the horizontal direction.

  The clamp device 3 includes a base 4, a clamp portion 10 fixed on the base 4, and a natural clamp portion 20. In this embodiment, the clamp part 10 is provided in three places, and the natural clamp part 20 is provided in one place (refer Fig.2 (a)).

  As shown in FIG. 3, the clamp unit 10 includes a clamp arm 11 and a sheet 12. The clamp arm 11 has a plunger 13 attached to a base end portion and a link 14 attached to an intermediate portion. The plunger 13 is provided so as to be movable up and down by a drive unit (not shown) such as an air cylinder. With the workpiece W placed on the upper surface of the sheet 12, the plunger 13 is raised and the tip of the clamp arm 11 is lowered, whereby the workpiece W is clamped and fixed between the clamp arm 11 and the sheet 12 from above and below.

  The natural clamp part 20 is provided with the main-body part 21, the plunger 22, and the pad 23 as shown in FIG. The plunger 22 is provided so as to be movable up and down by a drive unit (not shown) such as an air cylinder. By raising and lowering the plunger 22, the pad 23 can be moved closer to and away from one side surface (lower surface in the present embodiment) of the workpiece W. The natural clamp unit 20 is provided with detection means for detecting the optimum position with respect to the workpiece W. In the present embodiment, the position where the pad 23 is brought into contact with the workpiece W is set as the optimum position, and a pressure sensor is provided as a detection means.

  As shown in FIG. 5, the milling method according to the embodiment of the present invention is performed through a clamping process, a natural clamping process, a first milling process, a re-natural clamping process, and a second milling process.

(1) Clamping process First, the workpiece | work W is mounted in the sheet | seat 12 of the three clamp parts 10 (refer Fig.2 (a)). At this time, the plunger 13 of the clamp portion 10 is retracted to the lowest position as shown by a solid line in FIG. 3, whereby the tip end portion of the clamp arm 11 is outside the sheet 12 (side away from the workpiece W). evacuate. At this time, the plunger 22 of the natural clamp part 20 is retracted to the lowest position, and the upper surface of the pad 23 is positioned below the upper surface of the sheet 12. Accordingly, in this state, the pad 23 of the natural clamp portion 20 is not in contact with the lower surface of the workpiece W. The clamping device 3 may be provided with positioning pins for positioning the workpiece W in the horizontal direction.

  In this state, the plunger 13 of each clamp part 10 is raised and the tip part of the clamp arm 11 is lowered. Thereby, as shown by a chain line in FIG. 3, the workpiece W is sandwiched and fixed between the clamp arm 11 and the sheet 12 from above and below. In this state, the upper surface of the clamp arm 11 is disposed below the processing surface F of the workpiece W. Thereby, the situation where the milling blade 2a and the clamp arm 11 interfere in a subsequent milling process is avoided. For this reason, the clamp location by the clamp part 10 is limited to the location where it fell below the process surface F of the workpiece | work W one step. In the present embodiment, the portions indicated by C1, C2, and C3 in FIG. 1 are clamped.

(2) Natural clamping process In the state which clamped the workpiece | work W with the three clamp parts 10, the plunger 22 of the natural clamp part 20 is raised, and the upper surface of the pad 23 is arrange | positioned in the optimal position with respect to the workpiece | work W. In the present embodiment, the state where the pad 23 is in contact with the lower surface of the workpiece W is set as the optimum position. When the pressure sensor detects contact between the pad 23 and the lower surface of the workpiece W when the plunger 22 is raised (ie, when a minute pressure is detected), the plunger 22 is stopped. The work W is supported from below by the pad 23 arranged at the optimum position. As described above, the position at which the plunger 22 is stopped at the moment when the pad 23 comes into contact with the workpiece W is set to the optimum position, and the plunger 22 is stopped in a state where the pad 23 is pressed against the workpiece W with a predetermined pressure. The position may be the optimum position.

  As described above, since the clamp location by the clamp portion 10 is limited, there is a possibility that the workpiece W cannot be supported in a stable state only by the clamping and fixing by the clamp portion 10. For example, the unsupported portion of the workpiece W may bend or vibrate due to the processing pressure from above by the milling blade 2a during milling. In particular, when the workpiece W is thin as in the present embodiment, the clamp location is severely limited, and bending or vibration due to processing pressure is likely to occur. Then, the workpiece | work W can be supported in the stable state by supporting the location with high possibility that a bending | flexion and a vibration generate among the locations which cannot be clamped with the clamp part 10 with the natural clamp part 20. FIG. In this embodiment, the portion indicated by N in FIG. 1 is supported by the natural clamp portion 20.

(3) 1st milling process Next, in the process part 2, the 1st milling (rough process) is given to the process surface F of the upper surface of the workpiece | work W. FIG. Specifically, while the motor 2b is driven and the milling blade 2a is rotated, the processing unit 2 is lowered, the milling blade 2a is brought into contact with the processing surface F, and this surface is plane-cut. In this state, the processing unit 2 is moved in the horizontal direction, and the entire processing surface F is cut and finished to a predetermined flatness.

(4) Re-natural clamping process When the first milling process is completed, the support of the workpiece W by the natural clamping unit 20 is once released. Specifically, the plunger 22 of the natural clamp part 20 is lowered, and the pad 23 is separated from the lower surface of the workpiece W. And the plunger 22 is raised again and the pad 23 is arrange | positioned in the optimal position. That is, the plunger 22 is stopped at the moment when the pad 23 comes into contact with the workpiece W, and the pad 23 is held at this position.

(5) Second Milling Process Then, the machining unit 2 performs the second milling (finishing) on the machining surface F of the workpiece W, and finishes the machining surface F to a desired flatness. Since the specific content of the second milling process is the same as that of the first milling process, duplicate description is omitted.

  According to the above milling method, the processed surface F can be finished with high flatness. That is, since the work distortion occurs in the workpiece W by the first milling process, the position of the natural clamp portion 20 may deviate from the optimum position. Thus, as described above, in the re-natural clamping process, the work W can be supported in a stable state by re-arranging the pads 23 of the natural clamping part 20 at the optimum position. By performing the second milling process in this state, the processed surface F can be finished with high flatness.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the optimum position of the pad 23 of the natural clamp portion 20 is a position where the optimum position is in contact with the lower surface of the workpiece W. However, the present invention is not limited to this. For example, a position away from the lower surface of the workpiece W by a predetermined distance may be set as the optimum position of the pad 23. In this case, the natural clamp unit 20 is provided with a distance sensor (not shown) that measures the distance between the pad 23 and the workpiece W.

  Moreover, in said embodiment, the clamp location of the workpiece | work W by the clamp part 10 is 3 places (C1-C3 of FIG. 1), and the support location of the workpiece | work W by the natural clamp part 20 is 1 location (N of FIG. 1). However, these numbers and positions may be changed.

  In the above-described embodiment, the case where the workpiece W is a timing chain cover has been described. However, the present invention is not limited to this. For example, the processing method of the present invention can be applied to a camshaft housing of an engine. Thus, the milling method of the present invention is suitably applied to thin-walled workpieces that are likely to be distorted by the first milling.

  In the above-described embodiment, the milling process is divided into two stages (the first milling process and the second milling process), but may be performed in three stages or more. In this case, it is preferable to provide a re-natural clamping step after milling that is particularly prone to processing distortion, that is, a large amount of cutting.

  Moreover, although the case where it arrange | positions so that the process surface F of the workpiece | work W may become an upper surface is shown in said embodiment, it is not restricted to this, For example, the workpiece | work W is arrange | positioned so that the process surface F may face down or sideways. May be.

DESCRIPTION OF SYMBOLS 1 Milling machine 2 Processing part 2a Milling blade 2b Motor 3 Clamping device 4 Base 10 Clamp part 11 Clamp arm 12 Sheet 13 Plunger 14 Link 20 Natural clamp part 21 Body part 22 Plunger 23 Pad F Work surface W Workpiece

Claims (1)

A method of milling the surface of a workpiece,
A clamping step of clamping and fixing the workpiece at the clamping portion;
A natural clamping process that supports the workpiece from one side by placing the natural clamping part close to the workpiece and placing it at the optimum position for the workpiece,
A first milling process for milling the surface of the workpiece;
A natural re-clamping process in which the natural clamp part is once separated from the work and placed again in the optimum position for the work,
A second milling process for further milling the surface of the workpiece;
Milling method to be performed in order.

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