JP2001255105A - Defect inspection method for axially symmetric object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection method for an axially symmetric object, which permits handy and quick inspection of defects such as chips or burrs with a higher detection accuracy as caused at a corner part, in the inspection of products with the aim of guaranteeing the quality thereof. SOLUTION: An axially symmetric object 11 is rotated about the shaft thereof and defects such as chips or burrs caused at a corner part are inspected with a contact type displacement meter 1 provided at the corner part. This realizes handy and quick inspection by examining defects such as chips or burrs caused at the corner part using the contact type displacement meter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method for an axisymmetric object for detecting the presence of a chip, a burr, or the like generated at a corner of an axisymmetric object.

[0002]

2. Description of the Related Art For example, in the case of an axially symmetric object of a high-precision precision part such as a ceramic valve, a defect such as a chip or a burr is easily generated at a corner of the valve. If such a defect is present, the product cannot be used as a product, so the corners of the manufactured axisymmetric object are inspected to detect defects such as chips or burrs that occur in the corners in advance, and the axisymmetric Objects need to be removed. Conventionally, as a method of detecting the presence of a defect such as a chip or a burr generated at a corner of an axisymmetric object, a method of visually detecting a corner defect using a microscope, and a method of detecting a corner using an image processing technique. A method for detecting a defect is generally used.

[0003]

Among the conventional methods described above, in the method of visually inspecting, when inspecting the corners of an axisymmetric object, it is difficult to fit on the microscope screen at one time over one round. Usually, the inspection is performed while rotating the object around the axis. In this case, it is necessary to sequentially inspect a plurality of corners, and there is a problem that much time is required for the inspection. In the method using image processing technology, it is possible to shorten the inspection time by performing image processing analysis by using multiple cameras at the same time. There was a problem of interference. In addition, when the inspection is automated using image processing, it is difficult to realize the processing due to the influence of dust, oil, processing marks, and the like on the surface.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a defect inspection method for an axisymmetric object capable of easily and quickly inspecting defects such as chips or burrs generated at corners in product inspection for quality assurance with high detection accuracy. It is.

[0005]

A defect inspection method for an axisymmetric object according to the present invention is characterized in that an axisymmetric object is rotated around an axis, and a chip generated at a corner is provided by a contact displacement meter provided at the corner. And inspects for defects such as burrs. In the present invention, a simple and quick inspection is realized by inspecting a defect such as a chip or a burr generated at a corner using a contact type displacement meter.

In a preferred embodiment of the present invention, the zeroth and first order components of the Fourier transform equation are obtained from the data f (x) from the displacement meter, and the zeroth and first order components are subtracted from the data to obtain the deviation, Data g without influence of runout component
(X) is obtained, and a defect inspection is performed based on the obtained data g (x). Further, the following evaluation function F is obtained from the data f (x) from the displacement meter, A point 1 at which F (l) is minimized is obtained, a rotation cycle obtained by removing the rotation speed fluctuation from this 1 is obtained, and a defect inspection is performed based on the obtained rotation cycle. In any case, various effects that cause errors can be eliminated, and highly accurate detection can be performed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an example of a state in which a defect inspection method for an axisymmetric object according to the present invention is performed. In the example shown in FIG. 1, a contact 3 attached to the tip of a plurality of displacement meters 1 is brought into contact with a predetermined position of a corner of an axisymmetric object 11 to be measured, and the axisymmetric object 11 is rotated. As shown in FIG. 1, the gripping of the axisymmetric object 11 can be inspected for all corners by being sandwiched between the bearing 6 and the driving force transmitting wheel 7. Axisymmetric object 11 being measured
The vertical movement of the cylinder has an adverse effect on the processing of the captured signal, so that the pin 8 and the pneumatic cylinder 9
The movement is suppressed by being sandwiched between. In order to suppress the resistance when the axisymmetric object 11 rotates, the tip of the holding pin 8 may be spherical or sharpened to reduce the contact area. In addition, 5 is a motor.

The displacements of the plurality of displacement meters 1 over one round are measured and recorded using the signal converter 2 and the signal processor 4. If the corner is missing, the contact 3 of the displacement meter 1 falls into the valley, and if there is a burr at the corner, the contact 3 of the displacement meter 1 gets over it, and the displacement is detected. Then, when data exceeding a predetermined threshold value is detected from the obtained displacement data over one round, it is determined that the axisymmetric object 11 has a defect. The axisymmetric object 11 has a deviation and a shake with respect to the axis. In such a case, it is preferable to process the signal by Fourier transform and remove the signal. In addition, there are cases where the rotational speed of the axisymmetric object 11 fluctuates. In such a case, it is preferable to obtain the influence from a predetermined evaluation function and remove it. These preferred examples will be described later in detail.

FIGS. 2A to 2C are views showing an example of a contact 3 used in the defect inspection method for an axisymmetric object according to the present invention. As shown in FIGS. 2A to 2C, the contact 3
As the flakes (FIG. 2A), the corners of the material (FIG. 2A)
(B)) or a thin thread, wire (FIG. 2 (c)) or the like can be used. Considering the wear life of the contact 3, it is preferable to design the tip of the displacement meter 1 so that it can be easily replaced.

Next, as preferred examples of the present invention, (1) removal of the influence of deviation and runout and (2) removal of the influence of rotation speed fluctuation will be described.

(1) Removal of deviation and shake: When the measurement is performed while rotating the axisymmetric object 11, the taken-in signal includes a deviation and a shake component (FIG. 3 (a)). If this signal is processed as it is, it may cause erroneous detection or missed detection. In order to separate the deviation and the shake from the signal, an expression for obtaining the zero-order and first-order components of a discrete Fourier transform expression can be used.

[0012]

(Equation 1)

In this process, the deviation is removed by the zero-order component represented by a ₀ and the shake component is removed by the first-order components represented by a ₁ and b ₁ . At the same time, the information on the amount of shake is obtained from the square root of the sum of squares of a ₁ and b ₁ . The corner runout information can be used as feedback for the machining process or as information for part shipment inspection. further,
If the displacement meter 1 is attached to an arbitrary position using the configuration and the arithmetic processing of the present invention as it is, the function as a shake measuring device is also achieved.

(2) Elimination of the influence of rotational speed fluctuation: When the pores for rotating the parts are driven by using friction, the rotational speed may change due to slippage or wear. If the actual rotation speed is different from the value set in the signal processor, the deviation and shake removal processing is not performed normally. With a change in rotational speed of only 5%, 16% of the whirling to be removed remains unabsorbed. Therefore, the actual rotation period is obtained by performing arithmetic processing on the obtained signal, and the measurement accuracy can be improved by removing the influence of the rotation speed by using the actual rotation period.

The total number of the measured signal data is M. Taking into account the periodicity of the measurement result and focusing on the n data from the beginning of the data, a data group very similar to this data group should appear one cycle later (FIG. 4). If a location that substantially matches the n data is found in the vicinity of the predicted one cycle later, it can be said that that is the beginning of the second cycle. Since it is unlikely that the measured values coincide completely, a point 1 where the value of F is minimized is searched for using the following evaluation function F. In this method, since the first n data in the first cycle and the first n data in the second cycle are compared, data for one cycle + n data is always required. The number of data M must be large so that one cycle + n data is always obtained even when the rotation of the component is the slowest.

[0016]

As is apparent from the above description, according to the present invention, a defect such as a chip or a burr generated at a corner is inspected using a contact type displacement meter, so that it is simple and quick. Inspection can be realized. Further, in an example in which the influence of the data deviation, the influence of the shake component, and the influence of the rotational speed fluctuation are removed, various effects that cause errors can be eliminated, and highly accurate detection can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a state in which a defect inspection method for an axisymmetric object according to the present invention is performed.

FIGS. 2A to 2C are diagrams illustrating examples of a contact used in the defect inspection method for an axisymmetric object according to the present invention.

3A is a diagram illustrating an example of a signal before the shake process according to the present invention, and FIG. 3B is a diagram illustrating an example of a signal after the shake process according to the present invention.

FIG. 4 is a diagram for explaining removal of the influence of rotational speed fluctuation in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Displacement meter, 2 signal converters, 3 contacts, 4 signal processors, 5 motors, 6 bearings, 7 wheels for driving force transmission, 8
Holding pin, 9 Pneumatic cylinder, 11 Axisymmetric object

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2F062 AA66 BB07 BB20 BC80 EE01 EE66 FF17 GG17 HH05 HH16 JJ10 2F069 AA60 AA68 BB40 CC10 DD08 DD13 DD15 DD19 GG01 GG13 GG39 GG52 GG58 GG65 GG78 GG01 GG78 GG23 PP02 QQ05 2G024 AA15 BA27 CA05 FA02 FA04 FA06

Claims (3)

[Claims] 1. An axisymmetric object characterized by rotating an axisymmetric object around an axis and inspecting a chip, a burr, or other defect at the corner with a contact displacement meter provided at the corner. Defect inspection method. 2. The data f from a displacement meter during the defect inspection.
From the (x), the 0th-order component and the 1st-order component of the Fourier transform equation are obtained, and the 0th-order component and the 1st-order component are subtracted from the data, thereby eliminating the influence of the deviation and the shake component, respectively.
2. The defect inspection method for an axisymmetric object according to claim 1, wherein (x) is obtained, and a defect inspection is performed based on the obtained data g (x). 3. The data f from a displacement meter during the defect inspection.
The following evaluation function F is obtained from (x), 2. The defect inspection method for an axisymmetric object according to claim 1, wherein a point l at which F (l) is minimized is determined, a rotation cycle obtained by removing a rotation speed fluctuation from the l, and a defect inspection is performed based on the determined rotation cycle.