JPH04335133A - Apparatus for setting evaluating range of machined surface - Google Patents

Abstract

PURPOSE:To set the evaluating range automatically without an error when a machined surface is evaluated. CONSTITUTION:The machined surface of an aluminum disk 2 is scanned with laser light in the direction of an arrow A. The diffracted light of the laser light is used for evaluating the machined surface. The regular reflected light is used for setting the evaluating range. The signal I00 of the regular reflected light is suddenly changed at an edge part 2a where the signal reaches the machined surface from a through hole 2H of the aluminum disk 2 during the scanning. The sudden change is captured with a high-pass filter 22, and this time point is made to be a reference time point. An evaluation-starting/finishing-signal forming part 23 forms an evaluation starting signal S and an evaluation finishing signal E with the reference time point as a reference.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a machined surface evaluation means for determining the life of a processing tool and processing defects by evaluating the machined surface when processing such as mirror cutting is performed, and the evaluation range of the machined surface. The present invention relates to a device for setting a machined surface evaluation range.

0002

2. Description of the Related Art When performing precise mirror finishing on a workpiece such as an aluminum disk substrate, a processing tool such as a diamond cutting tool is used. In this case, if the cutting tool is worn out, the cut surface will become rough, making it impossible to achieve the desired mirror finish, resulting in defective products. Furthermore, even if the cutting tool is not worn, the cutting tool may drag foreign matter and cause minute scratches on the mirror surface, resulting in defective products. For this reason, a machined surface evaluation is performed in which the machined surface of a finished workpiece is inspected to check for wear of the tool bit, presence of scratches, and the like. Although there are various methods for evaluating the processed surface, a method that scans the processed surface with a light beam such as a laser beam is generally adopted. In other words, when performing mirror finishing with a cutting tool, the cutting edge of the cutting tool creates extremely small grooves (
Cutter marks) are formed, so the machined surface is evaluated by irradiating the machined surface with a light beam, converting the diffracted light into an electrical signal, and processing this as appropriate.

0003

[Problems to be Solved by the Invention] By the way, since there are various types and sizes of workpieces, the range in which the machined surface is scanned with a light beam, that is, the range for evaluating the machined surface, varies depending on the type and size of the workpiece. different. Therefore, it is necessary to manually change the set value of the machined surface evaluation range every time the type or size of the workpiece changes, which is troublesome. Furthermore, even if set values are given in this way, if there is a relative positional shift in the scanning direction between the sensor head that sends and receives light beams in the machined surface evaluation means and the machined surface, there is a problem that errors will occur in the evaluation range. there were. SUMMARY OF THE INVENTION An object of the present invention is to provide a machined surface evaluation range setting device that solves the problems in the prior art described above and can automatically set a machined surface evaluation range without causing errors.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention scans a predetermined range of a machined surface of a workpiece in a predetermined direction with a light beam, and evaluates the machined surface using the reflected light beam. A first detection means for detecting the amount of specularly reflected light among the reflected light rays, and a second detection means for detecting a sudden change in the detection value of the first detection means during scanning of the processed surface. The present invention is characterized in that it is provided with a detection means, and an evaluation time setting means for setting an evaluation time of the machined surface using the time point at which the sudden change is first detected by the second detection means as a reference time point.

[0005]

[Operation] When a light beam is irradiated onto the machined surface of a workpiece, the reflected light includes specularly reflected rays and the aforementioned diffraction rays. is used to detect the amount of light, and when the detected amount of light changes rapidly during scanning of the processed surface, that time is taken as a reference time, and the scanning time is arbitrarily set based on this time. Since the scanning speed is constant, the setting of the scanning time is the setting of the machined surface evaluation range.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments. FIG. 1 is a block diagram of a machined surface evaluation device including a machined surface evaluation range setting device according to an embodiment of the present invention. In the figure, 1 indicates a spindle chuck of an ultra-precision lathe, and 2 indicates a machined aluminum disk attached to this spindle chuck 1. A through hole 2H is formed in the center of the aluminum disk 2 for attaching it to a mating device when it is actually used. 2a indicates the edge of the through hole 2H, and 2b indicates the outer edge of the aluminum disk 2. 3 is a machined surface evaluation device, which has the following configuration. 4 is a laser diode that outputs laser light;
5 is a driving device thereof, 6 is a collimator lens that converts the laser beam into parallel light, 7 is a pinhole that converts the laser beam into a beam with a diameter of about 1 mm, and 8 is a device that receives reflected light and outputs an electric signal proportional to the received light. It is a photodiode that A sensor head 9 is configured by the laser diode 4, the collimator lens 6, the pinhole 7, and each photodiode 8. 10 is an amplifier connected to each photodiode 8, respectively. 11 is an adder that adds the outputs of the two amplifiers 10; 12 is an averaging circuit that averages the summed values within a predetermined time; 13 is a comparator; and 14 is a setting section in which a predetermined setting value is set. 15 is a high pass filter that passes only high frequency components in the input signal; 16 is an averaging circuit; 17 is a comparator; and 18 is a set value setting section. 19 is a peak detector for detecting the peak value of the output of the high pass filter 15; 20 is a comparator; and 21 is a set value setting section. 22 is a high pass filter, and 23 is an evaluation start/end signal generating section that generates an evaluation start signal S for starting the evaluation of the machined surface and an evaluation end signal E for terminating the evaluation of the machined surface.

Next, the operation of this embodiment will be explained. The positional relationship between the sensor head 9 and the aluminum disk 2 at the start of scanning is such that the laser beam emitted from the pinhole 7 is located in the through hole 2H. The position of this laser beam may be any position in the through hole 2H. Next, the laser beam starts scanning the processed surface of the aluminum disk 2 in the radial direction as shown by arrow A. This scanning is performed by relative movement of the aluminum disk 2 and sensor head 9, but the scanning speed is constant. As described above, the laser beam is irradiated onto the cutter mark on the processed surface, resulting in reflected beams R00, R10, and R20. Reflected light R00
is specularly reflected light, and reflected lights R10 and R20 are diffracted lights, and these reflected lights respectively enter the photodiode 8 and generate electrical signals I00, I10, I2 proportional to the amount of incident light.
0 and amplified by the amplifier 10.

[0008] Here, the outline of machined surface evaluation will be explained. After the diffraction light signals I10 and I20 are amplified, they are added by an adder 11 and inputted to an averaging circuit 12 and a high pass filter 15 as a summed signal I12. Averaging circuit 1
2 is the average value I1 of the signal I12 input after the evaluation start signal S is input until the evaluation end signal E is input.
Find 3. The comparator 13 sets this average value I13 to the setting unit 1.
4 and outputs the result as a determination signal X. Since the average value I13 increases as the cutting tool wears down, if the determination signal X becomes a signal indicating that it exceeds the set value, it is determined that the cutting tool wear is progressing. On the other hand, only the high frequency component of the addition signal I12 inputted to the high pass filter 15 is extracted, and this high frequency signal (pulsating signal) is averaged as an average value I14 in the averaging circuit 16 in the same way as the averaging circuit 12. This average value I14 is compared with a set value in a comparator 17. The comparison result is output as a determination signal Y. Since the average value I14 also increases as the cutting tool wears, if the judgment signal Y becomes a signal indicating that it exceeds the set value, it is determined that the cutting tool wear is progressing, and this judgment signal Y and the judgment signal X A comprehensive judgment regarding tool wear is made. The high frequency signal of the high pass filter 15 is also input to the peak detector 19, where it detects the maximum peak value (maximum amplitude of the pulsating signal) of the signal input between the evaluation start signal S and the evaluation end signal E. ) I15 is determined and compared with the set value by the comparator 20. The comparison result of the comparator 20 is output as a determination signal Z. The maximum peak value I15 is a signal for determining defects on the machined surface, and if the determination signal Z becomes a signal indicating that it exceeds a set value, it is determined that a scratch or the like exists on the machined surface.

Next, FIGS. 2 and 3 show how to create the evaluation start signal S and the evaluation end signal E used for evaluating the machined surface.
This will be explained with reference to the waveform diagram shown in FIG. The specularly reflected light signal I00 output from the amplifier 10 has a waveform I00 in FIG.
As shown in , the level is low at the start of scanning because it is the reflected light from the through hole 2H, but as the scanning progresses and the laser light reaches the edge 2a, it is reflected by the machined surface of the aluminum disk 2 and rapidly increases. It increases and then becomes an almost constant value. At this point of increase, the high pass filter 22 outputs a signal I01 corresponding to the change, as shown in waveform I01 of FIG. As the scanning progresses further, the laser beam hits the outer edge 2b of the aluminum disk 2.
Once the signal I00 is out of the range, the signal I00 rapidly drops back to its original low level as shown in FIG. Even at this point of decrease, the high pass filter 22 outputs the signal I01 corresponding to the change (having the opposite polarity to the initial signal), as shown in FIG. When the evaluation start/end signal generation unit 23 receives the first output signal I01 of the high pass filter 22, this signal generates an evaluation start signal S (pulse signal) as shown in FIG.
is created and output, and the following output signal I01 is used as shown in Figure 2.
An evaluation end signal E (pulse signal) is created and output as shown in FIG. Both signals S and E are input to averaging circuits 12 and 16 and a peak detector 19. That is, the time from the output of the evaluation start signal S to the output of the evaluation end signal E becomes the evaluation time, and since the scanning speed is constant, the evaluation time becomes the machined surface evaluation range. In the above case, the evaluation time coincides with the machined surface scanning time, and the machined surface evaluation range is from the edge 2a of the aluminum disk 2 to the outer edge 2b. However, the processed surface evaluation range is not necessarily limited to the above range, and can be arbitrarily selected. That is, the evaluation start/end signal generation unit 23 is equipped with a timer circuit, and the input time of the first signal I01 from the high pass filter 22 is set as a reference time, and from this reference time, after the time t shown in FIG. The evaluation start signal S may be generated and output, and the evaluation end signal E may be generated and output after a time T from the reference time. This means is applied to the edge 2a of the aluminum disk 2.
This method can be applied when it is possible to evaluate the machined surface without scanning the entire area from the outer edge 2b to the outer edge 2b.

In the above embodiment, the high pass filter 2
2 is provided and the reference time point is determined by extracting the change in the signal I00. However, high
It is also possible to use a comparator instead of the pass filter 22 to set the machined surface evaluation range. FIG. 3 is a waveform diagram illustrating this means. In FIG. 3, I00 is the specularly reflected light signal as described above, and ITH is the threshold value set in the comparator. When the scan reaches the edge 2a and the signal I00 increases above the threshold ITH, the output signal of the comparator becomes, for example, a high level signal, and when the signal I00 decreases below the threshold ITH it becomes a low level signal. The evaluation start/end signal generating section 23 generates and outputs an evaluation start signal S when the output signal of the comparator rises, and generates and outputs an evaluation end signal E when the output signal of the comparator falls. As a result, the entire area from the edge 2a to the outer edge 2b of the aluminum disk 2 is set as the processed surface evaluation range. Of course, also in this example, the evaluation start/end signal generation unit 2
3 is provided with a timer circuit, and the evaluation time can be arbitrarily set using the rise time of the output signal of the comparator as a reference time. In this example, the first rapid change in the amount of specularly reflected light is captured and used as the reference point for the processed surface evaluation range.
Based on this, the evaluation time is the time until the next sudden change in light intensity, or the time determined by the timer circuit, so that the processing surface evaluation range can be automatically and easily applied to aluminum disks of any size. , can be set without error. In the above embodiments, an aluminum disk was used as an example of the workpiece, but it is obvious that the invention can be applied to any workpiece.

[0011]

[Effects of the Invention] As described above, in the present invention, the evaluation time is determined using the first sudden change in the amount of specularly reflected light as the reference point, regardless of the type or size of the workpiece. , the machined surface evaluation range can be set automatically and without error.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a machined surface evaluation range setting device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating an operation for setting a machined surface evaluation range.

FIG. 3 is a waveform diagram illustrating an operation for setting a machined surface evaluation range.

[Explanation of symbols]

2 Aluminum disk 3 Machined surface evaluation device 9 Sensor head 22 High pass filter 23 Evaluation start/end signal creation unit S Evaluation start signal E Evaluation end signal I00 Specular reflection light signal

Claims (5)

[Claims] Claim 1: A method in which a predetermined range of a machined surface of a workpiece is scanned in a predetermined direction with a light beam, and the reflected light beam is used to evaluate the machined surface, the amount of light of a specularly reflected light beam among the reflected light beams. a first detection means for detecting a sudden change in the detection value of the first detection means during scanning of the machined surface; and evaluation time setting means for setting the evaluation time of the machined surface using a point in time when a change is detected as a reference time. 2. The machined surface evaluation range setting device according to claim 1, wherein the second detection means is a high frequency filter. 3. The machined surface evaluation range according to claim 1, wherein the second detection means is a comparison means for comparing the detection value detected by the first detection means with a predetermined level. Setting device. 4. In claim 1, the evaluation time setting means sets the time from the reference time to a second time point at which the second rapid change is detected by the second detection means as the evaluation time. A device for setting a machined surface evaluation range. 5. The processing according to claim 1, wherein the evaluation time setting means sets a predetermined time from the reference time or from a time after a predetermined time has elapsed from the reference time as the evaluation time. A device for setting the surface evaluation range.