JPH06170700A - Milling tool having odd number of cutting edges and machining error measuring method/device for machining using this tool - Google Patents

Abstract

PURPOSE:To easily and surely measure an amount of deflecting of a milling tool during rotation having an odd number of cutting edges. CONSTITUTION:By detecting a normal direction position of a machining surface, in a part symmetrical to a tool rotational center 7 relating to cutting edges 24 of a tool of passing through the machining surface synchronously with the point of time the cutting edge 24 of the tool passes through the machining surface, by a noncontact detecting device, a position of the cutting edge is detected to measure a shape error of the machining surface. A shape of the part symmetrical to the tool rotational center 7 relating to the cutting edge of the tool is set vertical to a straight line of connecting the cutting edge 24 to the tool rotational center 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures in-process the shape error of a machined surface due to the deflection of the tool caused by the cutting force when the side milling or the step milling is performed using a milling tool such as an end mill. And a milling tool suitable therefor.

[0002]

2. Description of the Related Art A problem in NC cutting is that
Mainly the roughness of the surface of the work and the shape accuracy of the cutting surface. In particular, when side milling or step milling is performed using a milling tool such as the end mill 4 shown in FIG. 5, shape errors such as waviness and inclination of the machined surface due to the deflection of the tool pose a serious problem. In the past, when machining was performed with an NC machine tool using a milling tool such as an end mill, it was common to perform rough machining in advance and then finish machining with gradually reducing the depth of cut to obtain shape accuracy. . However, this method often depends on the intuition of a skilled worker, and requires several trial productions and measurement using a dedicated measuring machine. On the other hand, as described above, a method has been proposed in which the shape precision of the workpiece is the waviness or inclination of the machined surface caused by the deflection of the tool, and the tool deflection due to the cutting force is obtained by simulation calculation.

However, the method of obtaining the tool deflection by simulation calculation often does not match the reality when cutting a complicated curved surface. That is, when performing intermittent cutting like end milling, the magnitude and direction of the cutting force change momentarily even during one rotation of the tool due to the change in the contact position between the workpiece and the cutting edge of the tool. .
Since the bending of the tool is generated by this cutting force, the size and shape of the bending also change during rotation. The shape accuracy of the machined surface is determined by the deflection of the tool when the cutting edge of the tool passes through the finished surface. This is the same for up cut and down cut. Therefore, in order to obtain the machining error in-process, it is necessary to know how much the tool has deflected at the position when the cutting edge passes through the finished surface. Conventionally, as a method for measuring the amount of deflection at the tool tip of an end mill during side cutting, there is a method using a specially shaped tool and a flash camera. (For example, see Fujikoshi Technical Report vol.37 No.1.1981).
Similarly, in the case of side cutting, a steel ring is attached to a part of the end mill, and a deflection is measured by applying a leaf spring with a built-in strain gauge to this part. (For example, Machinery Promotion Association Technical Research Institute "Processing Technology Data File" 204F
00). However, while these conventional tool deflection measurement techniques were able to measure the deflection amount at the place where the rotating tool was not in contact with the workpiece, it was not possible to obtain the deflection shape over the whole area. Moreover, it was impossible to apply it to the machining error control of the workpiece in-process. For this reason, it is desired to develop a technique capable of easily and reliably measuring the amount of deflection of the milling tool during rotation and being applied to machining control of a workpiece in-process.

In order to solve this problem, only when the side milling or the step milling is performed using a milling tool having an even number of cutting edges, when the cutting edges of the milling tool pass through the working surface, A measurement that detects the position of the cutting edge by detecting the position of the cutting edge on the opposite side of the blade in the normal direction of the finished surface with a non-contact detection device, and measures the shape error of the processing surface in-process A method has been developed (Japanese Patent Application No. 4-34221). FIG. 5 shows an outline thereof, and 1 is a processing error measuring device using the processing error measuring method of the present invention. The displacement meter 2 is arranged so as to face the end mill 4. The end mill 4 is attached to a chuck 6 of a spindle head 5 of a machine tool, and a displacement gauge holder 8 is arranged around the chuck 6 concentrically with a rotation center 7 of the chuck 6. The displacement gauge holder 8 is located outside the chuck 6 and is rotatable about a rotation center 7 of the chuck 6, and as shown in FIG. It is something to detect.

[0005]

[Problems to be Solved by the Invention] Japanese Patent Application No. 4-34221
The method of measurement is that when a certain cutting edge is generating a machining surface, the cutting edge located on the opposite side to the center of rotation of the tool is on the normal line of the machining point. It is a measurement method that detects the position of the cutting edge that is being machined by detecting the position of the cutting edge on the opposite side of the cutting edge that is being processed, and measures the shape error of the machined surface. Applicable only to milling tools with an even number of cutting edges, where there is a cutting edge on the opposite side of the cutting edge.
Therefore, there is a problem that it is not possible to use a milling tool having an odd number of cutting edges, which is excellent in terms of material, rigidity, productivity, etc. of a tool or a workpiece. Therefore, the present invention can easily and reliably measure the amount of deflection of a rotating milling tool having an odd number of cutting edges, and reflect the measurement result in-process on the machining accuracy control of the workpiece. It is an object of the present invention to provide a machining error measuring method and device for machining using a milling tool having an odd number of cutting edges, and a milling tool suitable for it.

[0006]

SUMMARY OF THE INVENTION The present invention, when performing side milling or step milling with a milling tool having an odd number of cutting edges, synchronizes with the time when the cutting edges of the tool pass through the working surface. Position of the cutting edge is detected by the non-contact type detection device, which detects the position of the cutting surface that is symmetric with respect to the cutting edge passing through the machining surface of the tool, in the normal direction of the machining surface. It is characterized by detecting and measuring the shape error of the machined surface. Further, the shape of the portion symmetrical with respect to the cutting edge of the tool with respect to the tool rotation center is perpendicular to the straight line connecting the cutting edge and the tool rotation center.

[0007]

By the above means, even in the case of a tool having an odd number of cutting edges which does not exist at a position 180 degrees opposite to the cutting edge being machined, the tool diametric The shape error of the machined surface is measured by measuring the side surface position on the opposite side of.

[0008]

Embodiments of the present invention will be described below. The present invention, as shown in FIG. 1, is such that a synchronizing device 3 is added to a conventional device. The synchronizing device 3 obtains a signal from a rotation detector of a tool (not shown) and sends a measurement timing signal to the displacement meter. Specifically, the rotation detector of the tool is a pulse generator, and it receives pulse train signals so that the cutting edge surface of the tool produces a finished surface every few pulses before starting the machining or at the number of pulses from the origin position. Whether or not to process is stored in advance as synchronization data, and when the number of received pulses matches the synchronization data, a measurement timing signal is sent to the displacement meter. Displacement meter 2 measures
It is a portion (outer side surface 12) located on the opposite side in the radial direction of the machined surface generation portion 14 of the workpiece 10 of the end mill 4.

Next, the operation of detecting the shape error of the workpiece by using the processing error detecting device thus constructed will be described. When the end mill comes into contact with the work piece and cuts the work piece, when the end mill bends to cause an uncut portion on the work piece or overcutting (not shown) as shown in FIG. The uncut portion or the excessively cut portion (not shown) causes a shape error. The displacement meter 2 observes the outer side surface 12 of the end mill 4. If there is no deformation in the radial direction of the end mill, the distance between the displacement gauge 2 and the outer side surface 12 detected by the displacement gauge 2 plus the length from the outer side surface 12 to the end mill cutting edge is the machined surface generation part of the workpiece. Is the distance to. In this way, the position of the end mill 4 during processing is measured by the non-contact type displacement gauge 2 from the direction normal to the processing surface. The position of the outer side surface 12 of the end mill 4 at that time is measured in synchronism with the time when the cutting edge generates a machining surface at the height of the line of sight of the displacement meter by a signal from the synchronizing device. The rigidity of the end mill is sufficiently large in the radial direction and the deformation in the radial direction of the tool can be ignored compared to the deflection in the axial direction.Therefore, the difference between the measured value during cutting and the value during idling is due to the tool deflection on this machining surface. The resulting machining error will remain. In this way, by detecting the side surface position of the tool in synchronism with the time when the cutting edge of the tool generates the machining surface, even when machining is performed using a milling tool having an odd number of cutting edges, Process processing error measurement becomes possible.

A milling tool having an optimum shape for carrying out the present invention will be described below. In FIG. 3, 21
FIG. 4 is a sectional view of a milling tool having the shape of the present invention. A side surface of the tool including a portion 25 symmetrical about the rotation center 22 with respect to the cutting edge 24 is perpendicular to a straight line 48 connecting the cutting edge and a portion symmetrical about the tool rotation center with respect to the cutting edge, and a measurement range 46 of the position detector. Has become. In the machining using the milling tool of the present invention, as compared with the case of the conventional tool (see FIG. 6), as shown in FIG. 4, when the machining surface 41 is deflected in both vertical and horizontal directions. However, it can be seen that the measurement range 46 of the position detector is parallel to the machined surface, so that the measurement error due to the deflection 45 generated in the direction parallel to the machined surface does not occur.

[0011]

As described above, according to the present invention, it is possible to accurately measure a machining error in machining using a milling tool having an odd number of cutting edges.

[Brief description of drawings]

FIG. 1 is a diagram showing a concept of a processing error measuring device of the present invention.

FIG. 2 is a vertical cross-sectional view showing a state where the end mill is in contact with a workpiece.

FIG. 3 shows a milling tool according to the present invention.

FIG. 4 is a view for explaining the action of the milling tool of the present invention.

FIG. 5 is a perspective explanatory view of a processing error measuring device.

FIG. 6 is a diagram illustrating the operation of a conventional milling tool.

FIG. 7 is a diagram showing a concept of a conventional processing error measuring device.

[Explanation of symbols]

1 Machining error measuring device 2 Displacement meter 3 Synchronizing device 4 End mill 5 Spindle head 6 Chuck 7 Center of rotation 8 Displacement holder 9 Line of sight 10 Work piece 11 Machining surface without deflection 12 Outer side surface 13 Synchronous signal 14 Machining surface generation part 21 End mill 22 Center of rotation 24 Cutting edge 25 Symmetrical part with respect to the center of rotation with respect to the cutting edge 26 Measurement point of non-contact position detection device 27 Measured machining surface shape error 28 Measurement error 29 Actual machining surface shape error (= machining surface vertical 40 Deflection of the end mill in the direction) 40 Measuring axis of the non-contact position detector 41 Machining surface without deflection 42 End mill without deflection 43 Rotation center without deflection 44 Rotation center with respect to the cutting edge without deflection Symmetric part with respect to 45 45 Deflection of end mill in horizontal direction of machined surface 46 Line to the constant range 48 cutting edge and cutting edge connecting the symmetrical parts to the tool rotation center

Claims (3)

[Claims] 1. When side milling or step milling is performed using a milling tool having an odd number of cutting edges, the time when the cutting edges of the milling tool pass through the machining surface is detected,
In synchronization with it, the position of the cutting edge is detected by detecting the position in the normal direction of the processing surface of the portion symmetrical to the tool rotation center with respect to the cutting edge of the milling tool with a non-contact type detection device. , A method for measuring a machining error of a machining using a milling tool having an odd number of cutting edges, which is characterized by measuring a shape error of a machining surface. 2. A device for measuring a machining error when side milling or step milling is performed by using a milling tool having an odd number of cutting edges, and detecting a time point when the cutting edges of the milling tool pass through a machining surface. Means, and means for detecting, in a non-contact manner, the position in the normal direction of the machining surface of a portion symmetrical to the tool rotation center with respect to the cutting edge of the milling tool in synchronization with the passing time, A machining error measuring device for machining using a milling tool with an odd number of cutting edges. 3. A milling tool having an odd number of cutting edges, wherein a shape of a portion symmetrical with respect to the cutting edges about the tool rotation center is perpendicular to a straight line connecting the cutting edges and the tool rotation center. A milling tool with an odd number of cutting edges.