A method for calibrating a pass of a continuous rolling stand

Abstract

The application discloses a continuous rolling rack hole type calibration method and relates to the technical field of steel pipe rolling, and comprises the following steps: S1, hydraulic cylinder zero adjustment and calibration platform center correction; S2, installation of a calibration disc gauge; S3, filling of a gasket; S4, automatic calibration; S5, offline correction of a hole type; and S6, online hole type re-inspection. Through hydraulic cylinder zero adjustment and calibration platform center correction, the contact between a rolling roller and the calibration disc gauge is automatically calibrated, and a hole type deviation is corrected in real time, so that the calibration accuracy and efficiency are improved, and the precision and consistency of the hole type on the production line are ensured. Meanwhile, the fit degree of the clearance between the calibration disc gauge and the rolling roller and the deviation of the stroke value of the hydraulic small bin are judged, so that the center of the calibrated hole type is consistent with the center of the actual working hole type, and the risk of uneven wall thickness of the rolled rough pipe is reduced.

Description

Technical Field

[0001] This invention relates to the field of steel pipe rolling technology, specifically a method for calibrating the pass profile of a continuous rolling mill stand. Background Technology

[0002] The cross-sectional shape of the rolled tube depends on the space between the rolls and the mandrel, and the roll die restricts the flow of metal on the outside of the tube, thus affecting the uniformity of the wall thickness. Therefore, the accuracy of the actual roll die is crucial to ensuring wall thickness precision.

[0003] Currently, a traditional method involves calibrating the actual die profile using a polygonal disc gauge on a machine calibration bench. This method involves checking and adjusting the roll gap deviation, and adjusting the machine frame according to the standard value of the hydraulic chute stroke, to meet requirements before direct use. Another traditional method involves acquiring die profile images using a high-precision camera and comparing them with a reference pattern. However, both of these traditional methods have the following problems:

[0004] When using a polygonal disc gauge for die calibration, the point contact between the gauge and the rolls can lead to localized deformation of the gauge over time, causing a change in the contact position and increasing the deviation of the calibrated die. Furthermore, after assembly, it's impossible to easily and accurately assess and correct the positional deviation between the actual die and the theoretically designed die by checking the roll gap, meaning accurate calibration cannot be performed on-site. Additionally, this method relies on offline roll gap checks to determine die deviation, making it impossible to re-inspect the actual working die on the mill stand. This can cause the center of the actual working die to deviate from the center of the calibrated die, resulting in uneven metal flow during the rolling of the rough tube and increasing the unevenness of the rough tube wall thickness.

[0005] The method of using a high-precision camera to acquire aperture images and compare them with reference graphics has high equipment investment and maintenance costs, and the installation process is also relatively complicated.

[0006] Therefore, the present invention provides a method for calibrating the pass shape of a continuous rolling mill stand to solve the problems mentioned in the background art. Summary of the Invention

[0007] The purpose of this invention is to provide a continuous rolling mill stand pass calibration method to solve at least one aspect of the problems and defects mentioned in the background art.

[0008] According to one aspect of the present invention, a method for calibrating the pass pattern of a continuous rolling mill stand is provided, comprising the following steps: S1, zeroing the hydraulic cylinder and centering the calibration table; S2, installing the calibration disc gauge; S3, filling the shims; S4, automatic calibration; S5, offline correction of the pass pattern; S6, online re-inspection of the pass pattern.

[0009] Specifically, step S4 includes: starting automatic calibration, the hydraulic cylinder of the frame calibration table pushes the top slide of the roll swing arm until the roll contacts the calibration disc arranged in the center of the calibration table; and recording the stroke values ​​of the three hydraulic chambers at this time.

[0010] Step S5 specifically includes: measuring the gap between the calibration disc gauge and the roll with a feeler gauge. If the calibration disc gauge fits well with the edge of the roll and the gap is within 0.1mm, and the deviation of the stroke values ​​of the three hydraulic chambers is less than 1mm, then it is allowed to move to the production line for re-inspection; otherwise, the corresponding gap shims are filled or removed under the roll base to correct the roll surface position until it meets the requirements.

[0011] By using hydraulic cylinder zeroing and calibration platform centering, the contact between the rolls and the calibration disc is automatically calibrated, and die deviations are corrected in real time, improving the accuracy and efficiency of calibration and ensuring the precision and consistency of the die on the production line. Simultaneously, judging the fit between the calibration disc and the roll gap and the deviation of the hydraulic cylinder stroke ensures that the center of the calibrated die matches the actual working die center, reducing the risk of uneven wall thickness in the rolled tubes.

[0012] As a further aspect of the present invention: Step S6 includes: pushing the calibrated stand into the continuous rolling mill stand, adjusting the stand to the working position, and using a re-inspection standard part to place between the rolls to inspect the actual roll pattern. If it fits well with the edge of the roll and the gap is within 0.1mm, it is allowed to be put into production. Otherwise, repeat steps S1 to S6 until it meets the requirements, so as to ensure the accuracy and consistency of the actual roll pattern and reduce the roll pattern deviation on the production line.

[0013] As a further aspect of the present invention: in step S1, the hydraulic cylinder on the calibration platform is adjusted to the zero position using a standard frame, and the center of the calibration platform is corrected to improve the accuracy of the calibration platform and reduce the calibration error.

[0014] As a further aspect of the present invention: In step S2, the calibration disc gauge corresponding to the mounting frame is installed, the level of the calibration disc gauge is measured using a level, and the level of the calibration disc gauge is corrected to the range of 0°~0.2° to ensure that the calibration disc gauge is aligned with the horizontal plane, reduce the measurement error caused by the abnormal tilt of the calibration disc gauge, and improve the accuracy of hole calibration.

[0015] As a further aspect of the present invention: the calibration disc used in step S2 is of the theoretical die shape, so that the calibration disc matches the desired die shape, thereby enabling rapid and accurate calibration of the die shape of the continuous rolling mill stand; the gap in step S5 is the gap between the R2 segment arc of the calibration disc and the roll.

[0016] As a further aspect of the present invention: in step S3, after filling the roll base with a corresponding thickness pad to compensate for the change in roll diameter, the frame is pushed into the frame calibration table.

[0017] By adding a shim of appropriate thickness under the roll base, variations in roll diameter can be effectively compensated for, ensuring the accurate and stable position of the frame on the calibration table. This compensation measure also addresses the impact of roll diameter variations on the die shape, maintaining proper alignment between the frame and the calibration table, thereby guaranteeing the accuracy and consistency of the die shape.

[0018] As a further aspect of the present invention: the re-inspection standard is manufactured according to the designed hole shape, and the manufacturing precision and shape of the re-inspection standard are consistent with the designed hole shape, ensuring the accuracy and reliability of the measurement. Using the re-inspection standard for inspection allows for a direct comparison of the consistency between the actual hole shape and the designed hole shape, helping to promptly detect and correct any hole shape deviations.

[0019] As a further aspect of the present invention: the formula upon which the dimensional relationship between the gasket and the gap in step S5 is based is:

[0020] ;

[0021] in, This refers to the total dimensions of the gasket. The size of the gap, Correction shim values ​​are used to ensure that the hydraulic hopper stroke deviation of the three rolls is less than 1mm.

[0022] Based on the formula relating the dimensions of the shims to the gap, the dimensions of the corrected shims are calculated to compensate for variations in the thickness of the pads under the roll base, adjusting the roll surface position to achieve the ideal roll pass. Furthermore, controlling the hydraulic cylinder stroke deviation of the three rolls to less than 1mm ensures uniform metal flow during continuous rolling, thereby reducing the unevenness of the rough tube wall thickness.

[0023] The application of this continuous rolling mill pass calibration method in the field of steel pipe rolling technology has the following advantages and effects. First, by accurately assessing the deviation between the actual pass and the designed pass and making timely corrections, the uniformity of the steel pipe wall thickness and the consistency of its geometry can be guaranteed, thus improving the quality of the steel pipe. Second, adopting automatic calibration and online re-inspection can improve the efficiency and accuracy of calibration, reducing human error and production downtime. Furthermore, by using re-inspection standard parts and precise measuring tools, precise control of the pass can be achieved, improving the stability and reliability of the production process. Simultaneously, by adjusting the mill stand and using compensating shims, the radial variation of the rolls and the adjustment requirements of the mill stand can be addressed, ensuring the uniformity of metal flow and the consistency of rolling quality during continuous rolling. Attached Figure Description

[0024] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] Figure 1 Schematic diagram of the rack calibration platform;

[0027] Figure 2 This is a schematic diagram showing the contact between the roll and the calibration disc gauge;

[0028] Figure 3 A schematic diagram of the structure for calibrating the disc gauge;

[0029] Figure 4 This is a schematic diagram showing the fit between the roll and the re-inspection standard part;

[0030] Figure 5 A schematic diagram of the gaps in Case Study 1;

[0031] Figure 6 A schematic diagram of the gaps in Case Study 2;

[0032] Figure 7 This is a schematic diagram of the gap in Case Study 3.

[0033] In the diagram: 1. Roll base; 2. Roll; 3. Calibration disc gauge; 4. Re-inspection standard parts; 5. Hydraulic cylinder; 6. Top slide plate. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. In this specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as limiting the present invention's method for calibrating the pass profile of a continuous rolling mill stand.

[0035] Furthermore, in the following detailed description, numerous specific details are set forth for ease of explanation to provide a thorough understanding of the embodiments disclosed herein. However, it will be apparent that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and apparatuses are illustrated to simplify the figures.

[0036] According to an overall technical concept of the present invention, such as Figure 1-7 As shown, a method for calibrating the pass pattern of a continuous rolling mill stand is provided, including the following steps: S1, zeroing the hydraulic cylinder and centering the calibration table; S2, installing the calibration disc gauge; S3, filling the shims; S4, automatic calibration; S5, offline correction of the pass pattern; S6, online re-inspection of the pass pattern.

[0037] Specifically, step S4 includes: starting automatic calibration, the hydraulic cylinder 5 of the frame calibration table pushes the top slide plate 6 of the roller 2 swing arm until the roller 2 contacts the calibration disc 3 arranged in the center of the calibration table; and recording the stroke values ​​of the three hydraulic chambers at this time.

[0038] Step S5 specifically includes: measuring the gap between the calibration disc gauge 3 and the roll 2 with a feeler gauge. If the calibration disc gauge 3 and the edge of the roll 2 fit well and the gap is within 0.1mm, and the deviation of the stroke values ​​of the three hydraulic chambers is less than 1mm, then it is allowed to move to the production line for re-inspection; otherwise, the corresponding gap shims are filled or removed under the roll base 1 to correct the roll surface position until it meets the requirements.

[0039] By zeroing the hydraulic cylinder 5 and centering the calibration platform, the contact between the roller 2 and the calibration disc 3 is automatically calibrated, and the die deviation is corrected in real time, improving the accuracy and efficiency of calibration and ensuring the precision and consistency of the die on the production line. Simultaneously, judging the fit between the calibration disc 3 and the roller 2 and the deviation of the hydraulic cylinder stroke value ensures that the center of the calibrated die matches the actual working die center, reducing the risk of uneven wall thickness in the rolled tubes.

[0040] Step S6 includes: pushing the calibrated stand into the continuous rolling mill stand, adjusting the stand to the working position, and using the re-inspection standard part 4 to place between the rolls 2 to check the actual pass shape. If it fits well with the edge of the roll 2 and the gap is within 0.1mm, it is allowed to be put into production. Otherwise, repeat steps S1 to S6 until it meets the requirements, to ensure the accuracy and consistency of the actual pass shape and reduce the pass shape deviation on the production line.

[0041] In step S1, the hydraulic cylinder 5 on the calibration platform is adjusted to the zero position using a standard frame, and the center of the calibration platform is calibrated to improve the accuracy of the calibration platform and reduce calibration error.

[0042] In step S2, the calibration disc 3 corresponding to the mounting frame is installed, the level of the calibration disc 3 is measured using a level, and the level of the calibration disc 3 is corrected to the range of 0°~0.2° to ensure that the calibration disc 3 is aligned with the horizontal plane, reduce the measurement error caused by the abnormal tilt of the calibration disc 3, and improve the accuracy of hole calibration.

[0043] The calibration disc gauge 3 used in step S2 is the theoretical die shape, so that the calibration disc gauge 3 matches the desired die shape, thereby enabling rapid and accurate calibration of the die shape of the continuous rolling mill stand; the gap in step S5 is the gap between the R2 segment arc of the calibration disc gauge 3 and the roll 2.

[0044] In step S3, after filling the roll base 1 with a corresponding thickness pad to compensate for the change in roll diameter, the frame is pushed into the frame calibration table.

[0045] By adding a shim of appropriate thickness under the roll base 1, the variation in the diameter of roll 2 can be effectively compensated, ensuring the accurate and stable position of the frame in the calibration table. Furthermore, this compensation measure can resolve the impact of roll 2 diameter variation on the die shape, maintaining the correct alignment of the frame and the calibration table, thereby guaranteeing the accuracy and consistency of the die shape.

[0046] The re-inspection standard part 4 is manufactured according to the designed hole shape. The manufacturing precision and shape of the re-inspection standard part 4 are consistent with the designed hole shape, ensuring the accuracy and reliability of the measurement. Using the re-inspection standard part 4 for inspection allows for a direct comparison of the consistency between the actual hole shape and the designed hole shape, helping to promptly identify and correct any hole shape deviations.

[0047] The formula used to determine the dimensional relationship between the gasket and the gap in step S5 is as follows;

[0048] ;

[0049] in, This refers to the total dimensions of the gasket. The size of the gap. Correction shim values ​​are used to ensure that the hydraulic hopper stroke deviation of the three rolls is less than 1mm.

[0050] Based on the formula relating the dimensions of the shims and the gap, the dimensions of the corrected shims are calculated to compensate for changes in the thickness of the pads under the roll base 1, adjust the roll surface position, and achieve the ideal roll pass. Furthermore, controlling the hydraulic cylinder stroke deviation of the three rolls 2 to be less than 1mm ensures uniform metal flow during continuous rolling, thereby reducing the unevenness of the rough tube wall thickness.

[0051] The application of this continuous rolling mill pass calibration method in the field of steel pipe rolling technology has the following advantages and effects: First, by accurately assessing the deviation between the actual pass and the designed pass and making timely corrections, the uniformity of the steel pipe wall thickness and the consistency of its geometry can be guaranteed, thus improving the quality of the steel pipe. Second, the use of automatic calibration and online re-inspection can improve the efficiency and accuracy of calibration, reducing human error and production downtime. Furthermore, by using re-inspection standard parts 4 and precise measuring tools, precise control of the pass can be achieved, improving the stability and reliability of the production process. Simultaneously, by adjusting the mill stand and using compensation shims, the radial variation of the rolls 2 and the adjustment requirements of the mill stand can be addressed, ensuring the uniformity of metal flow and the consistency of rolling quality during continuous rolling.

[0052] The following is an implementation example of this continuous rolling mill pass calibration method:

[0053] Implementation Case 1:

[0054] S1. Hydraulic cylinder zeroing and calibration table centering.

[0055] Use a standard frame to adjust hydraulic cylinder 5 on the frame calibration platform to the zero position and calibrate the center of the calibration platform;

[0056] S2, Install the disc meter

[0057] The calibration disc gauge 3 is installed on the corresponding rack, and the level of the calibration disc gauge 3 is 0.13° when measured with a level.

[0058] S3, filler pad

[0059] The diameter of roll 2 on stand 1101 is reduced by 5mm. 2.5mm thick shims are filled on both sides under roll base 1. Then the stand is pushed into the stand calibration table.

[0060] S4, Automatic Calibration

[0061] When automatic calibration is initiated, the hydraulic cylinder 5 of the calibration table pushes the top slide plate 6 of the roller 2 swing arm until the roller 2 contacts the calibration disc 3 arranged in the center of the calibration table. Record the stroke values ​​of the three hydraulic chambers at this time: 1101R1: 834.93mm, 1101R2: 833.9mm, 1101R3: 834.23mm.

[0062] S6, Offline Correction Hole Type

[0063] The clearance between the 3R2 arc segment of the calibrated disc gauge and roll 2 was measured using a feeler gauge. The clearance on the R1b side of stand 1101 was 1.25 mm. Figure 5 As shown, adjust the shims on the bearing base of roll 2, with R1a side of frame 1101 adjusted by -1mm and R1b side adjusted by +0.5mm. Measure the gap between each roll 2 again; it should be less than 0.1mm. Record the stroke values ​​of the three hydraulic chambers at this time: 1101R1: 834.02mm, 1101R2: 833.7mm, 1101R3: 834.23mm. The deviation of the hydraulic chamber stroke value is less than 0.6mm, allowing it to be moved to the production line for re-inspection.

[0064] S6, Online Hole Type Re-inspection

[0065] After calibrating the stand, push it into the continuous rolling mill stand. After adjusting the stand to the working position, use the re-inspection standard part 4, which is made according to the design pass shape, to place between the rolls 2 to check the actual pass shape. The re-inspection standard part 4 fits well with the edge of the roll 2, and the gap is within 0.1mm. It is allowed to be put into production.

[0066] Implementation Case 2:

[0067] S1. Hydraulic cylinder zeroing and calibration table centering.

[0068] Use a standard frame to adjust hydraulic cylinder 5 on the frame calibration platform to the zero position and calibrate the center of the calibration platform;

[0069] S2, Install the disc meter

[0070] The calibration disc gauge 3 is installed on the corresponding rack, and the level of the calibration disc gauge 3 is 0.09° when measured with a level.

[0071] S3, filler pad

[0072] The diameter of roll 2 on stand 1462 is reduced by 5mm. 2.5mm thick shims are filled on both sides under roll base 1. The stand is then pushed into the stand calibration table.

[0073] S4, Automatic Calibration

[0074] Automatic calibration is initiated. The hydraulic cylinder 5 of the calibration table pushes the top slide plate 6 of the roller 2 swing arm until the roller 2 contacts the calibration disc 3 arranged in the center of the calibration table. The stroke values ​​of the three hydraulic chambers are recorded at this time: 1462R1: 836.82mm, 1462R2: 837.36mm, 1462R3: 837.43mm.

[0075] S5, Offline Correction Hole Type

[0076] Use a feeler gauge to measure the gap between the calibrated disc gauge 3R2 arc segment and roll 2. The gaps on the R2b and R3a sides of stand 1462 are 0.75mm and 0.75mm respectively. Adjust the shims on the roll 2 bearing base to +1mm on the R2b and R3a sides of stand 1462. Measure the gaps of each roll 2 again; they are less than 0.15mm. Record the stroke values ​​of the three hydraulic chambers at this time: 1462R1: 836.89mm, 1462R2: 837.01mm, 1462R3: 837.21mm. The deviation of the hydraulic chamber stroke values ​​is less than 0.5mm, allowing for re-inspection on the production line.

[0077] S6, Online Hole Type Re-inspection

[0078] After the calibrated stand is pushed into the continuous rolling mill stand and the stand is adjusted to the working position, the re-inspection standard part 4, which is made according to the design of the pass shape, is placed between the rolls 2 to check the actual pass shape. The re-inspection standard part 4 fits well with the edge of the roll 2 and the gap is within 0.1mm. It is allowed to be put into production.

[0079] Implementation Case 3:

[0080] S1, Hydraulic cylinder 5 zeroing and calibration platform center correction

[0081] Use a standard frame to adjust hydraulic cylinder 5 on the frame calibration platform to the zero position and calibrate the center of the calibration platform;

[0082] S2, Install the disc meter

[0083] Install the calibration disc gauge 3 on the corresponding rack, and use a level to measure that the levelness of the calibration disc gauge 3 is 0.1°;

[0084] S3, filler pad

[0085] The diameter of roll 2 on stand 1126 is reduced by 5mm. 2.5mm thick shims are filled on both sides under roll base 1. Then the stand is pushed into the stand calibration table.

[0086] S4, Automatic Calibration

[0087] Automatic calibration is initiated. Hydraulic cylinder 5 on the calibration platform pushes the top slide plate 6 of the roll 2's swing arm until roll 2 contacts the calibration disc 3 positioned at the center of the calibration platform. The stroke values ​​of the three hydraulic chambers are recorded at this point. 1126R1: 840.4mm, 1126R2: 839.33mm, 1126R3: 839.05mm;

[0088] S5, Offline Correction Hole Type

[0089] The clearance between the calibrated disc gauge 3R2 arc segment and roll 2 was measured using a feeler gauge. For stand 1126, the clearance on the R1a side was 0.4mm and on the R3a side was 0.35mm. Adjusting the shims on the roll 2 bearing base, the clearance on stand 1126 was -0.5mm on the R1a side, -1mm on the R1b side, and +0.5mm on the R3a side. The clearance was measured again and found to be less than 0.05mm. The stroke values ​​of the three hydraulic chambers were recorded: 1126R1: 839.29mm, 1126R2: 839.38mm, 1126R3: 838.87mm. The deviation of the hydraulic chamber stroke values ​​was less than 0.5mm, allowing for re-inspection on the production line.

[0090] S6, Online Hole Type Re-inspection

[0091] After the calibrated stand is pushed into the continuous rolling mill stand and the stand is adjusted to the working position, the re-inspection standard part 4, which is made according to the design of the pass shape, is placed between the rolls 2 to check the actual pass shape. The re-inspection standard part 4 fits well with the edge of the roll 2 and the gap is within 0.1mm. It is allowed to be put into production.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calibrating the pass profile of a continuous rolling mill stand, characterized in that, Includes the following steps: S1. Zeroing the hydraulic cylinder and centering the calibration platform; S2. Installing the calibration disc gauge; S3. Filling the shims; S4. Automatic calibration; S5. Offline correction of the hole pattern; S6. Online re-inspection of the hole pattern; In step S2, the calibration disc gauge corresponding to the mounting frame is installed, the level of the calibration disc gauge is measured using a level, and the level of the calibration disc gauge is corrected to the range of 0°~0.2°. The calibration disc gauge used in step S2 is the theoretical die shape. In step S5, when the die shape of the frame to be inspected is completely consistent with the design die shape, the R1 and R2 segments of the calibration disc gauge can completely fit with the arc in the middle of the roll. If there is a deviation in the die shape of the frame to be inspected, the gap between the R2 segment of the disc gauge and the roll is measured. Step S4 specifically includes: starting automatic calibration, the hydraulic cylinder of the frame calibration table pushes the top slide of the roll swing arm until the roll contacts the calibration disc arranged in the center of the calibration table; and recording the stroke values ​​of the three hydraulic chambers at this time. Step S5 specifically includes: measuring the gap between the calibration disc gauge and the roll with a feeler gauge. If the calibration disc gauge fits well with the edge of the roll and the gap is within 0.1mm, and the deviation of the stroke values ​​of the three hydraulic chambers is less than 1mm, then it is allowed to move to the production line for re-inspection; otherwise, the corresponding gap shims are filled or removed under the roll base to correct the roll surface position until it meets the requirements. The formula used to determine the dimensional relationship between the gasket and the gap in step S5 is as follows; ； in This refers to the total dimensions of the gasket. The size of the gap, The correction shim value is used to ensure that the hydraulic compartment stroke deviation of the three rolls is less than 1mm; Step S6 includes: pushing the calibrated stand into the continuous rolling mill stand, adjusting the stand to the working position, and using a re-inspection standard part to inspect the actual roll shape between the rolls. If it fits well with the edge of the roll and the gap is within 0.1mm, it is allowed to be put into production. Otherwise, repeat steps S1 to S6 until it meets the requirements.

2. The continuous rolling mill stand pass calibration method according to claim 1, characterized in that, In step S1, the hydraulic cylinder on the calibration platform is adjusted to the zero position using a standard frame, and the center of the calibration platform is calibrated.

3. The continuous rolling mill stand pass calibration method according to claim 1, characterized in that, In step S3, after filling the roll base with a corresponding thickness pad to compensate for the change in roll diameter, the frame is pushed into the frame calibration table.

4. The continuous rolling mill stand pass calibration method according to claim 1, characterized in that, The re-inspection standard parts are manufactured according to the designed hole shape.

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