CN114812470A - A kind of measurement and calibration method of thin film online thickness gauge - Google Patents

Abstract

The invention relates to a measurement and calibration method for a thin-film online thickness gauge, including a measurement and calibration method for detecting the thin-film online thickness gauge and traceability of its value; the invention solves the metrological calibration and traceability of the thin-film online thickness gauge. The appearance and working state of the thickness gauge, the thickness measurement indication error, the thickness measurement repeatability, the scanning speed indication error, the scanning speed repeatability and other measurement detection methods can judge whether the thin film online thickness gauge is functional and accurate. The traceability of the value adopts the direct measurement method and the indirect weighing method, which ensures the accurate and reliable transmission of the value of the equipment.

Description

A kind of measurement and calibration method of thin film online thickness gauge

technical field

The invention relates to a measurement and calibration method, in particular to a measurement and calibration method of a thin-film online thickness gauge.

Background technique

The thin film online thickness gauge is an application instrument that combines photoelectric detection, computer and industrial control technology to realize online thickness measurement. It is widely used in new film material thin film production lines, and can measure the thickness of various film materials in real time. , It has the characteristics of non-contact measurement, no damage to the surface of the object, no environmental pollution, strong anti-interference ability, high precision, complete data acquisition and processing functions, and is an important equipment for product quality control of new film material industrial production lines. At present, the online thickness gauges for thin films mainly include laser online thickness gauges, coating online thickness gauges, ray online thickness gauges, and infrared online thickness gauges.

At present, the thin film thickness gauge is generally installed on the bulky thin film production line, and its sensor position is relatively hidden and not easy to disassemble. Some thin film online thickness gauges emit radiation, so the direct detection is cumbersome and dangerous, and it is impossible to trace the source, and there is no relevant measurement calibration method.

In the high-speed vibration environment of the production line, the sensors and measurement circuit devices are easily affected by the environment over time, especially promethium-147, krypton-85, strontium-90, cesium-137 with beta rays After the radioactive source decays, the product thickness or scanning speed cannot meet the requirements, resulting in unstable product quality.

In view of the important role of the thin-film online thickness gauge in the film material production line, in order to avoid the occurrence of film defective products as much as possible, and to ensure the accuracy and reliability of the measurement data of the thin-film online thickness gauge and the unity of the traceability of the measurement value, an online thin-film thickness measurement is provided. The measurement and calibration method of the instrument is very necessary and has important practical significance.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a measurement and calibration method for a thin-film online thickness gauge, so as to solve the problem of the appearance and working state of the thin-film online thickness gauge, the indication error of thickness measurement, the repeatability of thickness measurement, and the scanning speed. The detection of measurement characteristics such as indication error and scanning speed repeatability can solve the measurement calibration and standard traceability of the thin film online thickness gauge.

For achieving the above object, the technical solution of the present invention is as follows:

A method for measuring and calibrating a thin film online thickness gauge, comprising the following steps:

(1) Select the standard film and confirm: According to the maximum measurement thickness in the online thickness measurement manual of the film, select the minimum thickness, half the maximum thickness and the maximum thickness of the PET film as the standard film, and confirm by direct measurement method and indirect measurement method The thickness of the film confirms that the traceability of the value is accurate;

(2) Judging the appearance and working status: Check whether the appearance of the online film thickness gauge is in good condition, whether the production line is running normally, and whether it has an output display device;

(3) Indication error of thickness measurement: put three standard thickness films of minimum thickness, half of the maximum thickness and maximum thickness that can be detected by the equipment on the feeding roller, set the parameters of the online thickness gauge, measure at least 6 times continuously, and calculate The displayed average value calculates the indication error according to the following formula,

where:

σ: absolute error of indication, the unit is micrometer (μm);

测量列的平均值，单位为微米(μm)；

The average value of the measurement column, in micrometers (μm);

L _o : standard film thickness, in microns (μm);

(4) Repeatability of thickness measurement: Put three standard thickness films of the minimum thickness, half the maximum thickness and the maximum thickness that can be detected by the equipment on the feeding roller, set the parameters of the online thickness gauge, and measure at least 6 times continuously at the same level. Repeatability calculated according to the following formula;

where:

s _L : repeatability, in microns (μm);

L _i : measurement column, the unit is micrometer (μm);

测量列的平均值，单位为微米(μm)；

The average value of the measurement column, in micrometers (μm);

(5) Confirm that the scanning speed digital tachometer value is accurate:

Confirm that the digital tachometer has been traced to the source of the value of the superior unit, and has passed the verification;

(6) Scanning speed indication error:

When measuring the scanning speed of the thin film online thickness gauge, the minimum scanning speed, half of the maximum scanning speed and the maximum scanning speed of the device are required for detection. The same speed is measured at least 6 times, and the indication error is calculated according to the following formula:

where:

δ _νi : Scanning speed indication error (%) at the i-th measurement point;

V _i : Indication value of scanning speed at the i-th measurement point, the unit is (m/s);

n _i : the rotational speed measured by the non-contact tachometer at the i-th measurement point, the unit is (r/min);

生产线上承载薄膜的滚筒外径测量平均值，单位为(m)；

The average measurement of the outer diameter of the roller carrying the film on the production line, the unit is (m);

(7) Scanning speed repeatability:

According to the above method, measure the same point continuously for at least 6 times. After calculating the scanning speed, calculate the obtained measurement column according to the following formula:

where:

s _V : repeatability, in m/s;

V _i : the displayed value of each scan, the unit is m/s;

扫描速度的平均值，单位为m/s。

Average scan speed in m/s.

Compared with the prior art, the present invention has the following beneficial effects:

The invention solves the problems that the film online thickness gauge cannot be traced and calibrated. The value is transmitted to the standard film by the direct measurement method and the indirect weighing method of the superior unit, and the rotational speed of the superior unit is transmitted to the standard film by the direct comparison method and the direct measurement method. Working tachometer. To test the appearance and working status of the thin film online thickness gauge, thickness measurement indication error, thickness measurement repeatability, scanning speed indication error, scanning speed repeatability and other measurement characteristics, to solve the measurement calibration and standard of the thin film online thickness gauge traceability. Provide measurement guarantee for the measurement development of the thin film industry.

Description of drawings

FIG. 1 is a flow chart of the measurement and calibration of the online thickness gauge of the present invention.

Detailed ways

In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific embodiments, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

As shown in Figure 1, a method for measuring and calibrating a thin film online thickness gauge of the present invention comprises the following steps:

Step 1: Standard film traceability

1. Using direct measurement method

(1) Environmental requirements:

Measure thin film samples under the same temperature, humidity and cleanliness conditions as the thin film online thickness gauge; there is no influence of dust, vibration, noise, corrosive gas and strong magnetic field that affect the measurement; the power supply for the electric micrometer Voltage abrupt changes should be avoided.

(2) Preparations:

Before self-calibration, select the 0.01μm gear of the inductance micrometer to ensure that the isothermal equilibrium time of the inductance micrometer and the calibration equipment is not less than 4 hours, and make the inductance micrometer energized and preheated for more than 30 minutes. When calibrating with a side probe , the axis of the measuring rod should be perpendicular to the vertical direction of the working surface of the bench.

(3) Collection requirements for standard film samples:

According to the maximum measured thickness in the online thickness measurement manual of the film, select the minimum thickness, half of the maximum thickness and the maximum thickness of the PET film with three thicknesses. At about 1m from the longitudinal end of the specimen, use a blade to cut the specimen along the entire width in the transverse direction, and the specimen width is 100mm. The specimen shall be flat without wrinkles and shall have no other defects. The sample is measured with single layer or multiple layers, and the requirements for the number of layers are shown in Table 1:

Table 1 Requirements for the number of measurement layers

Nominal thickness/μm Sample layers/layers ≤16 10 17～25 5 >25 1

Follow the method of aliquoting the length of the sample to determine the point where the thickness will be measured, as follows:

a) The length of the sample is less than or equal to 300mm, and 10 points are measured;

b) The length of the sample is between 300mm and 1500mm, and 20 points are measured;

c) The length of the sample is ≥1500mm, and at least 30 points are measured.

For uncut samples, the measurement should start at 50mm from the edge.

(4) Calculation method of standard film:

Directly measure with an electric micrometer, and after obtaining the measured value, the average thickness indication error should be calculated according to formula (1):

where:

W _a : Relative indication error of average thickness, %;

δ ₁ : average thickness, in microns (μm);

δ ₀ : Nominal thickness, in micrometer (μm).

The thickness indication error should be calculated according to formula (2):

where:

W _u : Maximum (minimum) thickness indication error, %;

δ ₂ : maximum (minimum) thickness, in microns (μm);

δ ₀ : Nominal thickness, in micrometer (μm).

2. Using indirect weighing method:

(1) Standard film sampling options:

According to the maximum measured thickness in the online thickness measurement manual of the film, select the minimum thickness, half of the maximum thickness and the maximum thickness of the PET film with three thicknesses. Unwind film or sheet rolls into stacks as cut material. Before measuring the width, ensure the material and production environment. For non-coiled samples, the state adjustment is sufficient for 30min.

Place the material on a flat surface, and place the support on the material at right angles to the longitudinal direction of the material. The zero scale on the ruler is aligned with the left longitudinal edge of the material. Measure the exact position of the right side of the material on the ruler, accurate to 1mm, from the width of the two samples. The distance between the two samples should be about 1m apart in the longitudinal direction.

The minimum number of samples cut from the film or sheet should be determined according to the width of the sample: when the width is less than or equal to 1000mm, cut 3 pieces; when the width is greater than 1000mm and less than or equal to 1500mm, cut 5 pieces; when the width is greater than 1500mm, cut Cut 10 pieces; for thin films, when the mass of 100cm2±0.5cm2 is less than 1g, use two adjacent samples in the extrusion/calendering direction as one sample for testing; measure the area of the sample and record .

(2) Calculation of net weight

Place the center of the sample roll on the pan of the balance, making sure that it is not in contact with other objects, and weigh the net weight of the sample.

Calculate the average value of the sample according to formula (3), the unit is kg.

where:

n: number of measurements (times);

m _i : measure the mass of the sample, in kilograms (kg);

测量试样质量平均值，单位为千克(kg)。

Measure the average mass of the sample in kilograms (kg).

(3) Calculation method of density

In order to ensure the accuracy of the test results, use the prepared alcohol to clean the sample to ensure that no air bubbles will be generated on the surface of the sample when placed in water. Put the sample into the center of the hanging rail inside the electronic density meter. The hanging rail should be completely submerged in the water of the electronic density meter and not in contact with the water tank. Operate the electron density meter and record the density value of the sample at this time.

(4) Calculation of thickness indication error

Calculation of average weighing thickness: The average weighing thickness h _s of a single sample is calculated according to formula (4), and the unit is micron.

In the formula: A _s : the mass of the sample per unit area, in grams per 100g/cm2;

ρ: density of the sample, in g/cm3.

If two samples are superimposed, the weighing thickness h _s of the sample is calculated according to formula (5), the unit is micrometer, and so on.

After the average measurement value is obtained, enter the formula (6) to calculate the thickness indication error:

where:

W _a : Average thickness indication error, %;

δ ₁ : Device display thickness, in microns (μm);

δ ₀ : actual average thickness, in micrometers (μm).

Depending on the quality of the sample, the thickness indication error should meet the requirements of Table 2 below:

Table 2 Thickness indication error

Step 2: Appearance and working status judgment method of thin film online thickness gauge:

After the traceability measurement of the standard film is confirmed by the above two methods, the standard film is placed on the raw material drum of the production line. Check whether the appearance of the thin film online thickness gauge is in good condition, whether the production line is running normally, and whether it has an output display device. If it conforms to normal production, prepare for the next measurement and calibration.

Step 3: Indication error of thickness measurement:

Put the minimum thickness, half of the maximum thickness and the maximum thickness that can be detected by the equipment on the feeding drum, set the parameters of the online thickness gauge, measure at least 6 times continuously, and calculate the average value displayed according to the following formula 7. value error.

where:

σ: absolute error of indication, the unit is micrometer (μm);

测量列的平均值，单位为微米(μm)；

The average value of the measurement column, in micrometers (μm);

L _o : Standard film thickness value, in micrometers (μm).

Step 4: Thickness Measurement Repeatability:

Put the minimum thickness, half of the maximum thickness and the maximum thickness three standard thicknesses that can be detected by the equipment on the feeding roller, set the parameters of the online thickness gauge, and measure at least 6 times continuously at the same level, and calculate the repeatability according to the following formula 8.

where:

s _L : repeatability, in microns (μm);

L _i : measurement column, the unit is micrometer (μm);

测量列的平均值，单位为微米(μm)。

The average value of the measurement column is measured in micrometers (μm).

Step 5: Measure the scanning speed of the thin film online thickness gauge

The minimum scanning speed, half of the maximum scanning speed and the maximum scanning speed are required for the detection of the device. The same speed is measured at least 6 times, and the indication error is calculated according to the following formula 9.

where:

δ _νi : Scanning speed indication error (%) at the i-th measurement point;

V _i : Indication value of scanning speed at the i-th measurement point, the unit is (m/s);

n _i : the rotational speed measured by the non-contact tachometer at the i-th measurement point, the unit is (r/min);

生产线上承载薄膜的滚筒外径测量平均值，单位为(m)。

The average measurement of the outer diameter of the rolls carrying the film on the production line, in (m).

Step 6: Scan Speed Repeatability:

The same point, continuous measurement at least 6 times, the obtained measurement column is calculated according to formula (10):

where:

s _V : repeatability, in m/s;

V _i : the displayed value of each scan, the unit is m/s;

扫描速度的平均值，单位为m/s。

Average scan speed in m/s.

Step 7: Evaluation of Measurement Uncertainty:

1 Overview

1.1 Measurement basis: Self-calibration regulations of the thin film online thickness gauge (taking the measurement method as an example, the weighing method is evaluated with reference to this method).

1.2 Environmental conditions: Measure the film sample under the same temperature, humidity and cleanliness conditions as the film online thickness gauge, and the measurement standard is stationary in this environment for more than 2 hours.

1.3 Main measurement standards: digital display electric micrometer with resolution (division value) of 0.01μm; steel ruler with measurement range (0～500)mm and division value of 1mm.

1.4 Measured object: thin film online measuring instrument.

1.5 Measurement method

According to the environmental requirements of the regulations, remove the film material on the line, use the method required in the specification, measure it with a steel ruler, and then cut it. The thickness of the cut sample is measured with a digital display electric micrometer, and the indication error, plane non-parallelism and repeatability are calculated.

2 Build a mathematical model

2.1 Mathematical model

where:

ΔP: Average thickness indication error, in microns (μm);

L _i : the displayed value of the online thickness gauge, in microns (μm);

电感测微仪测量平均值，单位微米(μm)。

The electrical micrometer measures the average value in micrometers (μm).

3. Standard uncertainty evaluation of input quantity

3.1 The main source of the standard uncertainty u (P _is ) of the input quantity is the measured indication value and the zero point error of the electric micrometer.

3.1.1 Evaluation of _the standard uncertainty u(P) of _the input quantity P

The source of the standard uncertainty of the input quantity P _is mainly the measurement repeatability of the electric micrometer, which can be obtained by measuring the repeatability condition and evaluated according to the A-type method. 10 repeatability measurements were performed on the samples measured by the thin film online thickness gauge, and the results are as follows:

Table 3 Measured values of 10 times measured by the thin film online thickness gauge

number of readings 1 2 3 4 5 Measured value (μm) 19.7 19.9 19.8 20.1 19.9 number of readings 6 7 8 9 10 Measured value (μm) 19.9 20.1 19.9 20.1 20.1

Its average is

Using the Bessel formula to calculate the experimental standard deviation σ of a single value, there are:

In order to be more representative and credible, we arbitrarily select samples of the same product from different collection locations to carry out 2 consecutive groups of measurements. Each group is measured 10 times under the condition of repeatability, and a total of 10 groups of measurement columns are obtained. The measurement column is calculated according to the above to obtain the experimental standard deviation of a single measurement, as shown in Table 2, and the following conclusions are obtained:

Pooled sample standard deviation

In the actual measurement situation, the input quantity P _is measured twice under repeatability conditions, and the arithmetic mean of the two measurements is taken as the result of each measurement. Then the standard uncertainty of the result is obtained:

3.1.2 Evaluation of the standard uncertainty u (p _{is 1} ) of the input quantity p _{is 1}

按照B类不确定度评定。Under the measurement conditions, the position of the zero scale line of the electric micrometer, the difference between the maximum and the minimum value is 0.4μm, and the half width is 0.2μm, assuming uniform distribution within the interval, including the factor

According to the category B uncertainty assessment.

but

3.1.3 The calculation of the standard uncertainty u (p _{is 1} ) of the input quantity, since the sub-items of the input quantity u (p _{is 1} ) are independent of each other, so

3.2 Evaluation of the standard uncertainty u (P standard) of the input quantity

按照B类不确定度评定。The maximum allowable error of the electric micrometer is determined according to its technical index, and the half-width bit a of the maximum allowable error is set to be evenly distributed in the interval, and the inclusion factor is

According to the category B uncertainty assessment.

α=0.25×40μm/100=0.1μm

4. Standard Uncertainty Summary Table

Standard Uncertainty Components sources of uncertainty Standard uncertainty u(P is checked) 0.1333μm u(P is) Measurement repeatability 0.0665μm u(P is) zero 0.1155μm u(P mark) The electrical micrometer itself 0.0577μm

5. Combined Standard Uncertainty

Since xi are independent of each other, the combined uncertainty is

6. Expanded Uncertainty

Taking k=2, then U=0.29 μm.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art , without departing from the scope of the technical solution of the present invention, when the technical content disclosed above can be used to make some changes or modifications to equivalent embodiments of equivalent changes, as long as it does not depart from the technical solution content of the present invention, according to the technical solution of the present invention Substantially any brief modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solutions of the present invention.

Claims (9)

1. The measurement calibration method of the film on-line thickness gauge is characterized by comprising the following steps: calibrating a film online thickness gauge by using a standard film, wherein the parameters of the film online thickness gauge include appearance, working state, indicating value error and repeatability; constructing a thickness tracing chain of the standard film for metering and calibrating by adopting a direct measurement method and an indirect weighing method; and (3) constructing a scanning speed tracing chain of the standard film for metering and calibrating by adopting a direct measurement method and a comparison method.

2. The on-line thickness gauge metering calibration method according to claim 1, characterized in that: the standard film is made of a PET film material, and the width of the standard film is equal to the maximum width measured by the on-line thickness gauge; at the highest set speed of the field device, the length is at least 1 cycle around the rack.

3. The on-line thickness gauge metering calibration method according to claim 1 or 2, characterized in that: when the standard film adopts a direct measuring method for tracing, a verification device of the Chinese metrological scientific research institute is transmitted to an inductance micrometer calibrator of a municipal metrological test station, and then the calibration device is transmitted to a working electricity sensing micrometer; when the method is used for tracing the source by adopting a weighing indirect weighing method, the weight calibrating device of the provincial metrological scientific research institute is transmitted to the electronic balance calibrating device of the city metrological testing institute, and then the weight calibrating device is transmitted to the electronic balance for work and the electronic densimeter.

4. The on-line thickness gauge metering calibration method according to claim 1 or 2, characterized in that: the tracing chain of the scanning speed is transmitted to a municipal metering hospital from a rotating speed standard device of a superior metering hospital through a comparison measuring method, then a calibration device of a municipal tachometer is transmitted to a digital tachometer, finally the speed of a standard film is directly measured by the digital tachometer for work, and the actual scanning speed of the on-line thickness gauge is obtained through measurement.

5. The on-line thickness gauge metering calibration method according to claim 1, characterized in that: when the appearance and the working state are calibrated, whether the appearance of the film on-line thickness gauge is intact or not and whether the production line runs normally or not are checked, and whether the production line has an output display device or not is judged.

6. The method for calibrating the metering of the on-line thickness gauge according to claim 1, wherein: when the indicating value error is calibrated, three standard thicknesses of the minimum thickness, half of the maximum thickness and the maximum thickness which can be detected by the equipment are placed on a feeding roller, the parameters of an online thickness gauge are set, the measurement is continuously carried out for at least 6 times on the same layer, and the indicating value error and the repeatability of the thickness measurement are calculated.

7. The on-line thickness gauge metering calibration method according to claim 6, characterized in that:

the method specifically comprises the following steps:

(1) thickness measurement indication error: three standard thickness films of minimum thickness, half of maximum thickness and maximum thickness which can be detected by the equipment are placed on a feeding roller, parameters of an online thickness gauge are set, continuous measurement is carried out for at least 6 times, a displayed average value is calculated, and an indicating value error is calculated according to the following formula,

in the formula:

σ: absolute error in micrometers (μm);

the mean of the columns was measured in micrometers (μm);

L _o : standard film thickness values in microns (μm);

(2) repeatability of thickness measurement: three standard thickness films of minimum thickness, half of maximum thickness and maximum thickness which can be detected by the equipment are placed on a feeding roller, parameters of an online thickness gauge are set, continuous measurement is carried out for at least 6 times on the same layer, and the repeatability is calculated according to the following formula;

in the formula:

s _L : reproducibility in micrometers (μm);

L _i : measurement columns in micrometers (μm);

the mean value of the columns was measured in micrometers (μm).

8. The on-line thickness gauge metering calibration method according to claim 1, characterized in that: when the scanning speed of the film on-line thickness gauge is measured, the minimum scanning speed, half of the maximum scanning speed and the maximum scanning speed of the device are required to be detected, the same speed is measured for at least 6 times, and the indication value error and repeatability of the scanning speed are calculated.

9. The on-line thickness gauge metering calibration method according to claim 8, characterized in that: the method specifically comprises the following steps:

(1) scanning speed indication error:

when the scanning speed of the film on-line thickness gauge is measured, the minimum scanning speed, half of the maximum scanning speed and the maximum scanning speed of the device are required to be detected, the same speed is measured for at least 6 times, the indicating value error is calculated according to the following formula,

in the formula:

δ _νi : scanning speed indication error (%) at the ith measurement point;

V _i : an indication of the scanning speed at the ith measurement point, in units of (m/s);

n _i : measuring by a non-contact tachometer at the ith measuring point to obtain the rotating speed, wherein the unit is (r/min);

measuring the average value of the outer diameter of a roller bearing a film on a production line, wherein the unit is (m);

(2) scanning speed repeatability:

continuously measuring the same point for at least 6 times according to the method, calculating the scanning speed, and calculating the obtained measurement column according to the following formula:

in the formula:

s _V : repeatability, unit is m/s;

V _i : the scanning of each time displays the value, and the unit is m/s;

the average value of the scanning speed is in m/s.

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