CN114101779A

CN114101779A - Strip-shaped metal material, slitting method, and meandering measurement method for strip-shaped material

Info

Publication number: CN114101779A
Application number: CN202111419681.1A
Authority: CN
Inventors: 木村直幸; 鲛岛大辅; 野村知康
Original assignee: JX Nippon Mining and Metals Corp
Current assignee: JX Nippon Mining and Metals Corp
Priority date: 2017-03-31
Filing date: 2018-03-09
Publication date: 2022-03-01
Also published as: CN110475639A; JP2018171677A; KR102425952B1; TW201836742A; JP6787832B2; TWI663009B; KR20210084684A; WO2018180378A1; KR20190133735A

Abstract

The present invention relates to a strip-shaped metal material, a slitting method, and a meandering measurement method for the strip-shaped metal material. The invention provides a strip-shaped metal material with high parallelism after slitting and a slitting method for obtaining the strip-shaped metal material, and provides a method for reasonably measuring meandering of the strip-shaped metal material. Wherein, when the strip-shaped metal material is used for measuring the clearance between the straight edge and the strip-shaped metal material in the direction perpendicular to the length direction by taking the length of 50mm as a unit, the maximum value of the clearance in every 1m in the length direction of the strip-shaped metal material is less than or equal to 0.12 mm.

Description

Strip-shaped metal material, slitting method, and meandering measurement method for strip-shaped material

The application is a divisional application of PCT patent application with the international application date of 3, 9 and 2018, and the international application date of the PCT patent application is 3, 9 and the application number of the PCT patent application is 201880022325.6.

Technical Field

The present invention relates to a strip-shaped metal material, a slitting method for continuously cutting a metal material into a predetermined width along a longitudinal direction to obtain the strip-shaped metal material, and a meandering measurement method for the strip-shaped metal material.

Background

In a production line for metal materials such as mild steel, copper alloy, and stainless steel, the metal materials are rolled to a final thickness while being conveyed in a longitudinal direction, slit into specific widths according to a user's desire, and wound into coil shapes to be shipped. As a method of longitudinally cutting a metal material into a specific width, a method of passing the metal material between longitudinal cutters having circular knife cutters arranged vertically is generally performed.

If the shape of the metal material before being slit is wavy rather than flat, both side edges of the slit strip-shaped metal material are not parallel straight lines, but show a curved shape as shown in fig. 2. Such a curved shape is not suitable for applications requiring strict dimensional accuracy. For example, when a lead frame is formed by etching a strip-shaped metal material, if the lead frame is bent largely, it is difficult to form holes at regular intervals by a pressing step, and the yield of products is significantly reduced.

As a method for preventing the bending, the following methods are known: before the metal material passes through the slitter, guide rollers linearly arranged in the conveying direction are pressed from both sides of the metal material (for example, patent document 1).

Patent document 2 describes a copper strip slitting device for slitting a copper strip in a longitudinal direction, the device including: an unwinding rotating device which feeds out the copper strip plate; a plurality of upper and lower base cutters which shear the copper strip plate to an extent that the copper strip plate is not completely separated in the thickness direction; a press roller for pressing the copper strip plate subjected to the shearing processing in the thickness direction to completely separate and cut the copper strip plate; and a winding rotary device for winding the separated and cut thin copper strip plate; the cutter head parts of the upper disc cutter and the lower disc cutter are composed of local conical cutter head parts, wherein the local conical cutter head parts comprise flat parts with contact angles of 0 degrees with the copper strip plate and inclined parts with angles of 5-30 degrees with the copper strip plate, and the inclined parts are formed on extension lines of the flat parts; as an additional effect of the invention, the amount of bending of the slit copper strip plate is also reduced.

Here, the measurement of the amount of bending is generally performed in accordance with JIS H3100 (2012), and specifically, as shown in fig. 2, is referred to as the depth of an arc of an arbitrary portion with respect to a standard length of 1000 mm.

Background of the invention

Patent document

[ patent document 1] Japanese patent application laid-open No. 10-109217

[ patent document 2] Japanese patent laid-open publication No. 2013-237116.

Disclosure of Invention

Problems to be solved by the invention

However, the above-mentioned means still fail to completely solve the problem of the reduction in the product yield in the pressing step. Further, the present inventors found that: even if the amount of bending measured according to the JIS standard is reduced, there is a case where the problem of abnormality in the pressing step cannot be solved.

Further, the present inventors have made further intensive studies and as a result have found that: when a metal material is continuously cut into a predetermined width along a longitudinal direction to obtain a strip-shaped metal material, micro-vibrations are generated in a width direction and a vertical direction, and the strip-shaped metal material is caused to meander at a minute period. The minute periodic meandering (hereinafter referred to as "minute meandering") may not be detected according to the JIS standard, and as a result, even if the amount of bending measured according to the JIS standard is reduced, a strip-shaped metal material suitable for the pressing step may not be obtained.

Therefore, there is a need for a strip-shaped metal material with high parallelism in which the micro-meandering is suppressed, and a slitting method for obtaining such a strip-shaped metal material. In addition to the JIS standards, a reasonable measurement method reflecting the minute meandering caused by the micro-vibration at the time of slitting is required.

That is, the strip-shaped metal material has both the amount of bending and the minute meandering measured in accordance with JIS standard. Therefore, even if the bending amount measured according to JIS standard is zero, the minute meandering can be made non-zero.

This is because the amount of bending measured according to JIS standard is different from the causative system of the occurrence of minute meandering. That is, the occurrence of bending measured according to JIS standard is due to the shape of the raw material before slitting. The shape of the material before slitting is affected by the finish cold rolling step or the shape straightening step or the relaxation annealing step after the finish rolling step. On the other hand, the generation of the micro-meandering is caused by the slitter apparatus and the slitting method as described above.

Accordingly, an object of the present invention is to provide a strip-shaped metal material having a high degree of parallelism after slitting, a slitting method for obtaining the strip-shaped metal material, and a method for reasonably measuring minute meandering of the strip-shaped metal material.

Means for solving the problems

The present invention includes the following aspects.

(1) A strip-shaped metal material, wherein a straight edge is brought into contact with a side surface of the strip-shaped metal material in the longitudinal direction, and when a gap between the straight edge and the strip-shaped metal material in a direction perpendicular to the longitudinal direction is measured in units of 50mm in length, the maximum value of the gap per 1m in the longitudinal direction of the strip-shaped metal material is 0.12mm or less.

(2) The strip-shaped metal material according to (1), wherein a bending amount per 1m in a longitudinal direction is 0.03mm or less.

(3) The strip-shaped metal material according to (1) or (2), wherein the strip-shaped metal material is a strip-shaped metal material of copper or a copper alloy.

(4) A method for longitudinally cutting a metal material into a predetermined band width while conveying the metal material in a longitudinal direction, comprising the steps of performing the longitudinal cutting step and the following steps (i) to (iii);

a slitting step of slitting a metal material into a specific band width by using a slitter having two pairs of circular knife cutters for cutting off edge regions on both sides of the metal material conveyed in a longitudinal direction, and at least one pair of circular knife cutters disposed inside each of the two pairs of circular knife cutters for cutting the metal material into a specific width; (i) the steps of (i) to (iii) are as follows:

(i) before the longitudinal cutting step, limiting the movement of the metal raw material conveyed in the length direction in a region from the position of the circular knife cutter to a position at least 1 time of the width of the metal raw material, and limiting the passing direction of the metal raw material from two sides;

(ii) before the longitudinal cutting step, limiting the movement of the metal raw material conveyed in the length direction from the front direction and the back direction in a region from the position of the circular knife cutter to a position at least 1 time of the width of the metal raw material;

(iii) after the slitting step, the movement of the slit metal material is limited to a region from the position of the circular knife cutter to a position 3 times the width of the metal material from the front and back directions by at least one position.

(5) The method of (4), further comprising the steps of: before the step of limiting the movement of the metal material conveyed in the longitudinal direction from both sides and the front and back directions, the metal material is leveled.

(6) A meandering measurement method of a strip material, characterized in that: the straight edge is brought into contact with the side surface of the strip material cut to have a fixed length in the longitudinal direction, and the gap between the straight edge and the strip material in the direction perpendicular to the longitudinal direction is measured in units of the pitch of the fixed length.

(7) The meandering measuring method according to (6), wherein the pitch is less than one tenth of the length of the strip.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a strip-shaped metal material with high parallelism in which meandering is suppressed can be obtained, and abnormalities in the pressing step can be effectively suppressed.

Drawings

Fig. 1 is a schematic view showing a state in which a strip-shaped metal material meanders.

Fig. 2 is a diagram showing a method of measuring a bending amount in JIS H3100 (2012).

FIG. 3 shows a schematic diagram of the construction of a slitter apparatus according to an embodiment of the present invention.

Fig. 4 is a diagram showing a meandering measurement method of a strip material according to an embodiment of the present invention.

Detailed Description

(Metal strip)

The kind of the strip-shaped metal material is not particularly limited, and examples thereof include steel, copper alloy, and stainless steel.

Here, it is important that when the straight edge is brought into contact with the side surface of the strip-shaped metal material in the longitudinal direction and the gap between the straight edge and the strip-shaped metal material in the direction perpendicular to the longitudinal direction is measured in units of 50mm in length, the maximum value of the gap per 1m in the longitudinal direction of the strip-shaped metal material is 0.12mm or less.

As described above, when a metal material is continuously cut into a predetermined width along the longitudinal direction to obtain a strip-shaped metal material, micro-vibrations are generated in the width direction and the vertical direction, and the strip-shaped metal material meanders. Such meandering due to the micro-vibration does not necessarily appear as bending of the strip-shaped metal material, and thus the method for measuring the amount of bending in JIS H3100 (2012) may not be able to accurately measure the meandering. In order to accurately evaluate such hunting, the number of measurement points must be increased compared to the method in JIS H3100 (2012). Therefore, in the present invention, when the straight edge is brought into contact with the side surface of the strip-shaped metal material in the longitudinal direction and the gap between the straight edge and the strip-shaped metal material in the direction perpendicular to the longitudinal direction is measured in units of 50mm in length, the maximum value of the gap per 1m in the longitudinal direction of the strip-shaped metal material is 0.12mm or less. Thus, the gap values can be obtained from a plurality of measurement points, and the meandering caused by the micro-vibration can be accurately reflected. As a result, a strip-shaped metal material suitable for a subsequent pressing step or the like can be reliably provided.

The details of the method for measuring the maximum value of the gap will be described later.

Further, the following strip-shaped metal material is preferable: the above condition is satisfied, and the amount of bending per 1m in the longitudinal direction is 0.03mm or less. The amount of bending is a value obtained by a measurement method of the amount of bending in JIS H3100 (2012). This ensures the quality of the strip-shaped metal material more reliably.

When the tensile strength of the strip-shaped metal material is 600MPa or more, the strip-shaped metal material can have a strength required as a material for electric and electronic components. If the tensile strength exceeds 950MPa, the processing may become difficult, and therefore 950MPa or less is preferable. From the viewpoint of achieving both strength and workability, the Vickers hardness of the strip-shaped metal material is preferably 180 to 300.

Next, the slitter apparatus and the slitting method according to the present invention will be described with reference to the drawings. A schematic diagram showing the constitution of the slitter apparatus (100) of the present embodiment is shown in fig. 3. The long metal material 200 taken out from the uncoiler ペイオフリール (not shown) is slit into a desired band width in the slitter 130 while being conveyed in the longitudinal direction. After the division, the metal material (200) can be wound into a coil shape by a tension roller (not shown). Although not shown, the metal material (200) can be loosened in a ring shape at the front and rear stages of the slitter apparatus (100). This makes it easy to adjust the conveyance speed of the metal material (200).

The kind of the metal material (200) to be slit is not particularly limited, and examples thereof include mild steel, copper alloy, and stainless steel. In order to obtain a raw metal material (200) having a high degree of parallelism after slitting, it is preferable to improve the flatness by performing leveling correction in advance by leveling rolls or the like before the raw metal material (200) enters the slitting machine (130). The thickness of the metal material is preferably 0.10 to 0.16 mm. If the thickness is less than 0.10mm, the strength is low, and it is difficult to use the metal alone and it is necessary to bond the metal to a resin or the like. If the thickness exceeds 0.16mm, the bending radius must be set large in bending, and this is not suitable for downsizing of electric and electronic parts. The width of the strip-shaped metal material after slitting is preferably set to 100 to 200 mm. If the thickness is less than 100mm, the productivity is poor, and if the thickness exceeds 200mm, it is difficult to perform press working with stable quality over the entire width.

(guide roll)

At the front stage of the slitter (130), guide rollers (120) are provided on both sides of the metal raw material (200) being conveyed. The guide rollers (120) are devices for preventing meandering by restricting the passing direction of the metal raw material (200) from both sides. When the metal material (200) being conveyed starts to meander, the side surface of the metal material (200) is abutted against the side surface of the guide roller (120) to prevent the meandering and correct the meandering in a specific passing direction. The rotation axis of the guide roller (120) is parallel to the front and back directions of the metal material (200), and thus the rotation direction of the guide roller when the metal material (200) abuts against the guide roller (120) coincides with the passing direction of the metal material (200). This can reduce friction between the metal material (200) and the guide roller (120). In order to ensure the meandering preventing effect, the guide roller (120) must be disposed in a region from the position of a circular knife cutter of a slitter to a position of at least 1 time the width of the metal material. In order to improve the meandering preventing effect, the guide rollers (120) are preferably arranged in a straight line on each side. The guide rollers (120) are preferably provided in pairs on opposite sides of the metal material (200).

(Snake prevention board of slitter front section)

However, the provision of only the guide roller (120) has a limited effect of preventing meandering, and thus cannot prevent meandering at a high level. Further, the movement of the metal material (200) in the vertical direction cannot be restricted only by the guide roller (120), and thus, there may be a case where the metal material (200) is undulated or passes over the guide roller (120). Therefore, it is effective to further provide a pair of meandering preventing plates (110a, 110b) for pressing the metal material (200) from above and below as meandering preventing means at the front stage of the slitter (130). From the viewpoint of preventing meandering, undulation, and passing over the guide roller (120), it is preferable that the guide roller (120) and the meandering preventing plates (110a, 110b) are provided so that the length ranges thereof in the passing direction at least partially overlap. The lower meandering preventing plate (110b) can be laid on a suitable base or floor, and the upper meandering preventing plate (110a) can be placed on the lower meandering preventing plate so as to sandwich the metal material (200) being conveyed. By providing the meandering preventing plates (110a, 110b) in addition to the guide rollers (120), meandering, undulation, and passing over the guide rollers of the metal material (200) are suppressed, and the base material can be advanced to the slitting step in a more flat state. In order to ensure the meandering preventing effect, the meandering preventing plates (110a, 110b) must be disposed in a region from the position of a circular knife cutter of a slitter described below to a position of at least 1 time the width of the metal material.

Preferably, a sheet of a material having a low frictional resistance, such as a commercially available nonwoven fabric, is attached to the surfaces of the meandering preventing plates (110a, 110b) that come into contact with the metal material (200) so as not to damage the metal material (200) and not to increase the conveyance resistance. The pressing force of the meandering preventing plates (110a, 110b) against the metal material (200) can be set appropriately in consideration of the meandering preventing effect, and a sufficient effect can be obtained even when the meandering preventing plates (110a, 110b) are formed as plywood. When the self weight of the snake-preventing board can not obtain the snake-preventing effect, a weight can be placed on the snake-preventing board.

From the viewpoint of enhancing the meandering prevention effect, the meandering prevention plates (110a, 110b) are preferably provided so as to have a width equal to or greater than the width of the metal material (200) and so as to press the metal material (200) across the entire width of the metal material (200). The length of the meandering prevention plates (110a, 110b) in the direction of passage can be set as appropriate while maintaining the meandering prevention effect. The upper and lower meandering preventing plates (110a, 110b) may be formed of one sheet, or may be formed by arranging a plurality of sheets in the conveying direction. Specifically, the length of the meandering preventing plates (110a, 110b) in the direction of passage is preferably 500 to 800 mm.

(slitting machine)

Referring to fig. 3, in one embodiment, the slitting machine (130) may have: upper and lower pairs of circular knife cutters for cutting off edge regions on both sides of the metal raw material being conveyed in the length direction; and at least one pair of upper and lower circular knife cutters disposed inside the two pairs of circular knife cutters, respectively, for cutting the metal material into a predetermined width.

(Snake prevention board of slitting machine rear section)

In order to significantly improve the parallelism of the slit metal material (200), it is effective to provide meandering preventing plates (140a, 140b, 160a, 160b, 170a, 170b) also at the rear stage of the slitting machine (130). The prevention of meandering of the metal material (200) after slitting prevents the metal material (200) after slitting from overlapping, and the prevention of meandering of the metal material (200) after slitting also contributes to the prevention of meandering of the metal material (200) before and during slitting. In order to ensure the meandering preventing effect, the meandering preventing plates (140a, 140b, 160a, 160b, 170a, 170b) must be disposed in a region from the position of the circular knife cutter of the slitter to a position 3 times or more the width of the metal material. When the self-weight of the meandering prevention plates (140a, 140b, 160a, 160b, 170a, 170b) cannot sufficiently obtain the meandering prevention effect, a weight (150) may be further placed on the meandering prevention plates. The preferred aspects of the meandering preventing plates (140a, 140b, 160a, 160b, 170a, 170b) are the same as those of the meandering preventing plates (110a, 110b) at the front stage of the slitter (130), and therefore, the description thereof is omitted.

Next, a method of measuring meandering of a strip material according to the present invention will be described. When measuring meandering of a strip, a straight edge is brought into contact with a side surface of the strip cut to have a fixed length in the longitudinal direction, and a gap between the straight edge and the strip in a direction perpendicular to the longitudinal direction is measured in units of pitches of the fixed length. This makes it possible to effectively reflect meandering caused by micro-vibration in the slitting process on the measurement result. For example, the pitch may be set to a length of one tenth or less of the length of the strip, 10 points or more may be measured, the maximum value of the obtained values may be used as an index value of meandering, and the maximum value may be set to a fixed index or less.

For example, as shown in fig. 4, on a measuring table 203 having a plane on which a strip material 250 is placed and a plurality of measuring holes 210 provided at a specific pitch in the measuring direction on the plane, a reference straight edge 204 is placed on the measuring table 203 along the measuring direction so as to partially cover each measuring hole, and the gap between the reference straight edge 204 and the strip material 250 in each measuring hole 210 can be measured. Here, in order to easily measure the gap between the reference straight edge (204) and the strip (250), the spacer (208) may be disposed along the measuring direction so that the strip (250) and the reference straight edge (204) are spaced apart by a distance capable of partially covering each measuring hole. When the spacer (208) is disposed, the actual value of the gap between the reference straight edge (204) and the strip (250) is obtained by subtracting the offset distance of the spacer (208) from the measured value.

The meandering measurement method of a strip material of the present invention can be applied to the strip metal material of the present invention. The meandering measurement method of a strip material according to the present invention can be applied to a long strip material, and may not necessarily be applied to a strip metal material.

Examples

The following examples of the present invention are provided for better understanding of the present invention and advantages thereof, and are not intended to limit the present invention.

A metal material, namely a Carson copper alloy (2-4 mass% Ni-0.4-1.0 mass% Si-Cu) having a tensile strength, Vickers hardness, plate thickness and plate width shown in Table 1, was slit using a slitter device having a structure shown in FIG. 3. In each of the examples and invention examples, the lengths (110a, 110b) of the meandering preventing plates at the front stage of the slitter, the presence or absence of the meandering preventing plates (140a, 140b, 160a, 160b, 170a, 170b) at the rear stage of the slitter, and the widths of the strip-shaped metal materials after slitting were also adjusted as described in table 1.

The operating conditions of the slitter apparatus are as follows.

Guide rollers (120): are linearly arranged on both sides in the passing direction. The area where the guide roller is provided is the same as the area where the meandering preventing plates (110a, 110b) at the preceding stage are provided.

Meandering prevention plates (110a, 110b) of the preceding stage: a commercially available plywood made of nonwoven fabric was attached to the surface of the plywood which was in contact with the metal material. The weight was adjusted in such a manner that no scratching was caused.

Meandering preventing plates (140a, 140b, 160a, 160b, 170a, 170b) of the rear stage: a commercially available plywood made of nonwoven fabric was attached to the surface of the plywood which was in contact with the metal material. The weight was adjusted in such a manner that no scratching was caused.

Weight (150): the weight was adjusted in such a manner that no scratching was caused.

The evaluation of each example and comparative example was performed as follows.

< tensile Strength >

The tensile strength in the direction parallel to the rolling direction was measured by a tensile tester in accordance with JIS-Z2241.

Vickers hardness

According to JIS-Z-2244 (2009) in order to load: 0.098N was subjected to a micro Vickers hardness test to measure the micro Vickers hardness.

< bend >)

Measurement was carried out in accordance with JIS H3100 (2012).

< micro hunting >

The slit was cut 1m in the longitudinal direction of the longitudinally cut strip-shaped metal material, the straight edge was brought into contact with the side surface in the longitudinal direction, the gap between the straight edge and the strip-shaped metal material in the direction perpendicular to the longitudinal direction was measured in units of 50mm in length, and the maximum value was set to the value of the minute meandering.

< presence of pressureless Exception >

As shown in fig. 2, a step of forming a guide hole at a travel pitch (travel length), a step of conveying a material at a travel pitch (travel length), and a step of inserting a pilot punch into the guide hole at a travel pitch (travel length) are sequentially performed, and a press test of continuously conveying a strip-shaped metal strip is performed by repeating the series of operations. In the press test, the presence or absence of an abnormality was determined as follows.

Pressure anomaly: the conveyance of the strip-shaped metal belt is stopped.

Pressure anomaly: the edges of the pressed strip metal band are deformed by contact with the press structure.

Pressure anomaly: damage occurs to the edges of the pressed strip metal strip due to contact with the press structure.

No pressure exception: no such stops, deformations and damages were found.

In examples 1 to 11, since the meandering value was 0.12mm or less, there was no abnormality in the subsequent pressing step. The bending value can be suppressed to 0.03mm or less.

On the other hand, in comparative examples 1 to 6, since the meandering value exceeded 0.13mm, an abnormality occurred in the subsequent pressing step. In particular, in comparative examples 1 to 3, it is understood that the value of the meandering is at a low level, but the value of the meandering is high, and thus the abnormality in the pressing step cannot be suppressed.

Description of the reference numerals

110a, 110 b: snake prevention plate of front section

120: guide roller for preventing meandering

130: slitting machine

140a, 140b, 160a, 160b, 170a, 170 b: meandering preventing plate of rear section

150: weight object

200: metal raw material

203: measuring table

204: reference ruler

208: spacer member

210: measuring hole

250: a strip-shaped material.

Claims

1. A strip-shaped metal material, wherein a straight edge is brought into contact with a side surface of the strip-shaped metal material in the longitudinal direction, and when a gap between the straight edge and the strip-shaped metal material in a direction perpendicular to the longitudinal direction is measured in units of 50mm in length, the maximum value of the gap per 1m in the longitudinal direction of the strip-shaped metal material is 0.12mm or less.

2. The strip-shaped metal material according to claim 1, wherein a bending amount per 1m in a longitudinal direction is 0.03mm or less.

3. The strip metal material according to claim 1 or 2, wherein the strip metal material is a strip metal material of copper or a copper alloy.

4. A method for longitudinally cutting a metal material into a predetermined band width while conveying the metal material in a longitudinal direction,

comprising the steps of carrying out a slitting step and the following steps 1) to 3):

a slitting step of slitting a metal material into a specific band width by using a slitter having two pairs of circular knife cutters for cutting off edge regions on both sides of the metal material conveyed in a longitudinal direction, and at least one pair of circular knife cutters disposed inside each of the two pairs of circular knife cutters for cutting the metal material into a specific width; 1) -3) the steps are as follows:

1) before the longitudinal cutting step, limiting the movement of the metal raw material conveyed in the length direction in a region from the position of the circular knife cutter to a position at least 1 time of the width of the metal raw material, and limiting the passing direction of the metal raw material from two sides;

2) before the longitudinal cutting step, limiting the movement of the metal raw material conveyed in the length direction from the front direction and the back direction in a region from the position of the circular knife cutter to a position at least 1 time of the width of the metal raw material;

3) after the slitting step, the movement of the slit metal material is limited to a region from the position of the circular knife cutter to a position 3 times the width of the metal material from the front and back directions by at least one position.

5. The method of claim 4, further comprising the steps of: before the step of restricting the movement of the metal material conveyed in the longitudinal direction from both sides and the front and back directions, the metal material is leveled.

6. A meandering measurement method of a strip material, characterized in that: the straight edge is brought into contact with the side surface of the strip material cut to have a fixed length in the longitudinal direction, and the gap between the straight edge and the strip material in the direction perpendicular to the longitudinal direction is measured in units of the pitch of the fixed length.

7. The meandering measurement method according to claim 6, wherein the pitch is less than one tenth of the length of the strip.