Assembling, welding and deformation preventing tool for thin-wall sealed container and manufacturing method and using method of assembling, welding and deformation preventing tool

Abstract

The invention provides an assembling, welding and anti-deformation tool for a thin-wall sealed container as well as a manufacturing method and a using method of the assembling, welding and anti-deformation tool, and belongs to the technical field of anti-deformation tools. Welding cushion blocks are arranged at the two ends of two semi-arc plates respectively, radius fine adjustment bolts are arranged on the welding cushion blocks, the two semi-arc plates are connected into a complete circular ring through hexagon nuts and threads of the radius fine adjustment bolts, positioning nuts are evenly arranged along the shapes of the semi-arc plates, and force application bolts are connected with the positioning nuts through threads. According to the welding and anti-deformation tool for the novel thin-wall sealed container, the tool can adapt to cylinders with various diameters by adjusting the initial positions of the bolts, and the manufacturing cost of tools with different models is reduced by adjusting the opposite openings of the end sockets. Eight evenly-distributed inner wall supporting points are provided while roundness correction is conducted, and the distances of the bolts extending out of the semicircular arc plates are controlled to be the same, so that even and powerful annular supporting can be provided to restrain welding deformation.

Description

Technical Field

[0001] The invention relates to the field of anti-deformation tooling, and in particular to a welding and anti-deformation tooling for a thin-wall sealed container, and a manufacturing method and a use method thereof. Background Art

[0002] When welding pressure vessel components, since the barrel is mostly welded into a circle after the whole plate is bent, there is a certain deviation between its overall roundness and the roundness of the butt end. Thin-walled sealed containers are particularly serious in terms of the lack of roundness at the butt end due to their weak self-supporting ability and welding deformation. The conventional solution is to use 1 to 2 jacks to apply radial force to make the butt end match the head as much as possible. This method is not convenient to operate, the rounding accuracy is low and not uniform, and it cannot provide uniform and effective circumferential support to prevent welding deformation during the welding process. Summary of the invention

[0003] The present invention overcomes the above problems in the prior art and provides a welding and anti-deformation tool for thin-walled sealed containers, as well as a manufacturing method and a use method. To achieve the above purpose, the technical solution adopted by the present invention is:

[0004] A welding and anti-deformation tool for a thin-walled sealed container, comprising a welding pad, a positioning nut, a force bolt, a semi-circular arc plate, a hexagonal nut and a radius fine-tuning bolt. Welding pads are respectively arranged at both ends of the two semi-circular arc plates, and the radius fine-tuning bolt is arranged on the welding pads. The two semi-circular arc plates are connected into a complete ring through the threads of the hexagonal nut and the radius fine-tuning bolt. The positioning nuts are evenly arranged along the shape of the semi-circular arc plates, and the force bolt is connected to the positioning nut through threads.

[0005] Preferably, the model of the positioning nut is M30, the model of the force bolt is M30*150, and the model of the radius fine-tuning bolt is M16*90.

[0006] Preferably, if the thin-wall sealed container is made of stainless steel, the semi-circular plate, positioning nut, force bolt, hexagonal nut and radius fine-tuning bolt are made of 304 stainless steel plate; if the thin-wall sealed container is made of carbon steel, the semi-circular plate is made of Q235B steel plate, and the positioning nut, force bolt, hexagonal nut and radius fine-tuning bolt are made of 35CrMoA.

[0007] Preferably, the positioning nuts are symmetrically arranged along the central axis of the semicircular plate and evenly arranged at intervals of 45 degrees on the semicircular plate, and the positioning nuts are evenly distributed on the outer edge of the semicircular plate.

[0008] Preferably, the radius fine-tuning bolt can fine-tune the tooling size by 0-20 mm.

[0009] A method for manufacturing a welding and anti-deformation tool for a thin-wall sealed container, the specific steps of the manufacturing method are:

[0010] Step 1: According to the inner diameter of the thin-wall sealed container, two semicircular arc plates with an outer diameter equal to the inner diameter of the container body and a width of one tenth of the inner diameter of the container body are manufactured;

[0011] Step 2: Remove 20mm from both ends of the semicircular plate, weld a welding pad 10mm away from the end of the semicircular plate, and weld a hexagonal nut on the welding pad;

[0012] Step 3: Weld 4 positioning nuts on the surface of each semi-circular plate at an interval of 45 degrees, and pass the force bolt radially through the end of the positioning nut on the side of the semi-circular plate close to the center of the circle.

[0013] A method for using a welding and anti-deformation tool for a thin-wall sealed container, the specific steps of the method are:

[0014] Step 1: Before installing the anti-deformation tooling, measure the positive and negative errors of the inner wall diameter of the thin-wall sealed container, and mark the data deviation on the outer wall corresponding to the thin-wall sealed container body. After confirming the deviation position, adjust the position with the largest negative deviation to a horizontal state; connect the two semi-circular arc plates together by screwing the radius fine-tuning bolt onto the hexagonal nut, and screw the radius fine-tuning bolt to the root to make the two semi-circular arc plates fit together;

[0015] Step 2: Place the anti-deformation tool inside the thin-wall sealed container, position the radius fine-tuning bolt in the vertical direction, and expand the tool diameter in the horizontal direction by screwing the radius fine-tuning bolt until the outer edge of the anti-deformation tool is equal to or close to the maximum diameter of the inner wall of the thin-wall sealed container in the horizontal direction, and then screw the eight force bolts onto the positioning nuts so that the eight force bolts are in contact with the inner wall of the thin-wall sealed container to complete the initial fixation;

[0016] Step 3: Divide the thin-walled sealed container in step 2 into eight equal parts in the direction of roundness, and measure the positive and negative values ​​of the errors at the eight equal parts of the thin-walled sealed container with a ruler again. According to the roundness of the thin-walled sealed container, adjust the screw-out size of the force bolts (3), that is, recover the size of the two force bolts (3) with positive roundness error values ​​to half of the positive error value, and screw out the two force bolts (3) with negative roundness error values ​​to half of the negative error value; then re-measure the roundness error with a ruler, check the change of the roundness of the thin-walled sealed container body, and adjust again with the same method until the roundness of the thin-walled sealed container is finally measured and guaranteed, and it can be determined that the calibration is completed;

[0017] Step 4: When there is an error in the roundness of the head, you can refer to the above method for correction, and then connect the thin-walled sealed container with the head after adjustment.

[0018] Preferably, when the tooling diameter is expanded in the horizontal direction in step 2, if the tooling cannot be expanded to the inner diameter of the container due to large resistance, the tooling should be expanded to a maximum size close to the inner diameter of the container and larger than the load deviation size of the barrel diameter.

[0019] Preferably, in step three, the roundness error is re-measured by a ruler and no adjustment is required if it is within 1 mm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Through the welding and anti-deformation tooling of the new thin-walled sealed container, the assembly joint can be adjusted, the deformation of the thin-walled sealed container during the welding process can be controlled, and the welding quality and welding pass rate of the thin-walled sealed container are improved; at the same time, this tooling operates in a narrow space, and the container outlet is small, so it needs to have a disassembly function.

[0022] The thin-wall sealed container welding and anti-deformation tooling has a simple structure, is easy to operate, and can be disassembled and folded, realizing the welding adjustment and anti-deformation support of thin-wall sealed container products. The thin-wall sealed container welding and anti-deformation tooling solves the problems of cylinder deformation correction and misalignment of the end cap during welding of such products.

[0023] The device has good versatility and a wide range of applications. By adjusting the initial position of the bolts, it can adapt to the adjustment of the cylinders and heads of various diameters, reducing the cost of manufacturing different types of tooling. In addition, because it provides 8 evenly distributed inner wall support points during rounding, and by controlling the distance of the bolts extending out of the semicircular plate to be the same, it can provide uniform and powerful circumferential support to suppress welding deformation. This type of thin-wall sealed container welding and anti-deformation tooling has been used in the manufacturing process of our company's pressure vessels, ensuring the smooth manufacturing of the products and has been well received. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a front view of a welding and anti-deformation tool for a thin-wall sealed container.

[0025] Figure 2 for Figure 1 Middle AA section view.

[0026] Figure 3 for Figure 2 Enlarged view of the middle part.

[0027] Figure 4 The present invention is a three-dimensional diagram of a welding and anti-deformation tool for a thin-wall sealed container.

[0028] Figure 5 The present invention is a top view of a welding and anti-deformation tool for a thin-wall sealed container.

[0029] In the figure: 1 is a welding pad; 2 is a positioning nut; 3 is a force bolt; 4 is a semicircular arc plate; 5 is a hexagonal nut; 6 is a radius fine-tuning bolt. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] like Figure 1-5 As shown, a welding and anti-deformation tool for a thin-walled sealed container, the welding and anti-deformation tool for a thin-walled sealed container includes a semi-circular arc plate, a positioning nut, a force bolt, a hexagonal nut and a radius fine-tuning bolt. Welding pads are respectively provided at both ends of the two semi-circular arc plates, and the radius fine-tuning bolts are provided on the welding pads. The two semi-circular arc plates are connected into a complete ring through the threads of the hexagonal nut and the radius fine-tuning bolt. The positioning nuts are evenly arranged along the shape of the semi-circular arc plates, and the force bolts are connected to the positioning nuts through threads.

[0033] Preferably, the model of the positioning nut is M30, the model of the force bolt is M30*150, and the model of the radius fine-tuning bolt is M16*90.

[0034] Preferably, if the thin-walled sealed container is made of stainless steel, the semicircular plate, positioning nut, force bolt, hexagonal nut and radius fine-tuning bolt are made of 304 stainless steel plate, bolt and nut to avoid carbon pollution; if the thin-walled sealed container is made of carbon steel, the semicircular plate is made of 15mm steel plate of Q235B material, and the positioning nut, force bolt, hexagonal nut and radius fine-tuning bolt are made of 35CrMoA material.

[0035] Preferably, the positioning nuts are symmetrically arranged along the central axis of the semicircular plate and evenly arranged at intervals of 45 degrees on the semicircular plate, and the positioning nuts are evenly distributed on the outer edge of the semicircular plate.

[0036] Preferably, the radius fine-tuning bolt can fine-tune the tooling size by 0-20 mm.

[0037] A method for manufacturing a welding and anti-deformation tool for a thin-wall sealed container, the specific steps of the manufacturing method are:

[0038] Step 1: According to the inner diameter of the thin-wall sealed container, two semicircular arc plates with an outer diameter equal to the inner diameter of the container body and a width of one tenth of the inner diameter of the container body are manufactured;

[0039] Step 2: Remove 20mm from both ends of the semicircular plate, weld a welding pad 10mm away from the end of the semicircular plate, and weld a hexagonal nut on the welding pad;

[0040] Step 3: Weld 4 positioning nuts on the surface of each semi-circular plate at an interval of 45 degrees, and pass the force bolt radially through the end of the positioning nut on the side of the semi-circular plate close to the center of the circle.

[0041] A method for using a welding and anti-deformation tool for a thin-wall sealed container, the specific steps of the method are:

[0042] Step 1: Before installing the anti-deformation tooling, measure the positive and negative errors of the inner diameter of the thin-walled sealed container (theoretically, the cross-section of the cylinder is circular, but in reality there will be deviations, the cylinder is not round, and forms an ellipse. The major diameter and minor diameter refer to the cylinder diameter plus the positive deviation and the cylinder diameter minus the negative deviation), and mark the data deviation on the outer wall corresponding to the cylinder of the thin-walled sealed container. After confirming the deviation position, adjust the position with the largest negative deviation to a horizontal state (3 o'clock and 9 o'clock directions); connect the two semi-circular arc plates together by screwing the radius fine-tuning bolt onto the hexagonal nut, and screw the radius fine-tuning bolt to the root to make the two semi-circular arc plates fit together, so that the tooling can be placed inside the container conveniently;

[0043] Step 2: Place the anti-deformation tool inside the thin-wall sealed container, position the radius fine-tuning bolts in the vertical direction (0 o'clock and 6 o'clock directions), and expand the tool diameter in the horizontal direction by screwing the radius fine-tuning bolts until the outer edge of the anti-deformation tool is equal to or close to the maximum diameter of the inner wall of the thin-wall sealed container in the horizontal direction, and then screw the eight force bolts onto the positioning nuts so that the eight force bolts are in contact with the inner wall of the thin-wall sealed container to complete the initial fixation;

[0044] Step 3: Divide the thin-walled sealed container in step 2 into eight equal parts in the direction of roundness, and measure the positive and negative values ​​of the errors at the eight equal parts of the thin-walled sealed container with a ruler again. According to the roundness of the thin-walled sealed container, adjust the screw-out size of the force bolts (3), that is, recover the size of the two force bolts (3) with positive roundness error values ​​to half of the positive error value, and screw out the two force bolts (3) with negative roundness error values ​​to half of the negative error value; then re-measure the roundness error with a ruler, check the change of the roundness of the thin-walled sealed container body, and adjust again with the same method until the roundness of the thin-walled sealed container is finally measured and guaranteed, and it can be determined that the calibration is completed;

[0045] Step 4: When there is an error in the roundness of the head, you can refer to the above method for correction, and then connect the thin-walled sealed container with the head after adjustment.

[0046] Preferably, when the tooling diameter is expanded in the horizontal direction in step 2, if the tooling cannot be expanded to the inner diameter of the container due to large resistance, the tooling should be expanded to a maximum size close to the inner diameter of the container and larger than the load deviation size of the barrel diameter.

[0047] Preferably, in step three, the roundness error is re-measured by a ruler and no adjustment is required if it is within 1 mm.

[0048] Example 2

[0049] like Figure 1-5 As shown, a welding and anti-deformation tool for thin-walled sealed containers is composed of a semicircular arc plate, a positioning nut, a force bolt and a radius fine-tuning bolt. The semicircular arc plate is used to match the inner diameter of the product and provide a circumferential force point. The positioning nuts are evenly distributed on the edge of the arc plate to determine the force point. The force bolt connects the arc plate through the positioning nut to apply a reverse force to the cylinder wall. The radius fine-tuning bolt is used to connect the two arc plates. In addition to the connection, the tool size can also be fine-tuned to make it fit the inner wall of the product more closely.

[0050] According to the inner diameter of the thin-walled cylinder, a suitable semi-circular arc plate is initially selected, and the semi-circular arc plates on both sides are connected by radius fine-tuning bolts. According to the material and wall thickness of the thin-walled cylinder, a certain number of positioning nuts (6-12 pieces) are uniformly welded, and the force bolts are passed through the positioning nuts radially. Adjust the radius fine-tuning bolts to make the tooling fit the inner wall of the cylinder more closely. According to the situation of the cylinder, the tightness of each force bolt is adjusted in a targeted manner to ensure that the roundness of the cylinder is matched with the roundness of the head, and at the same time, a uniform circumferential force is provided during welding to ensure that the welding deformation is controllable.

[0051] The semicircular arc plate is used to match the inner diameter of the product and provide a circumferential force point. The positioning nuts are evenly distributed on the edge of the arc plate to determine the force application point. The force bolt is connected to the arc plate through the positioning nut to apply a reverse force to the cylinder wall. The force applied to the cylinder body is adjusted by the length of the bolt screwed in to change the roundness of the cylinder body. Generally, 8 positioning nuts are evenly distributed at 45 degree intervals and inserted into the force bolt to achieve a relatively uniform internal support. The radius fine-tuning bolt is used to connect two arc plates. In addition to the connection, the tooling size can also be fine-tuned (0-20mm) to make it fit the inner wall of the product more closely.

[0052] A method for manufacturing a welding and anti-deformation tool for a thin-walled sealed container is as follows: according to the inner diameter of the sealed container product, two semicircular rings with an outer diameter equal to the inner diameter of the cylinder body and a width of one tenth of the inner diameter of the cylinder body are manufactured, and 20 mm is removed from each end of the semicircular ring so that it can be smoothly unfolded on the inner wall of the cylinder body. A welding pad is welded 10 mm from the end of the semicircular arc plate, a hexagonal nut is welded on the welding pad, and the two semicircular arc plates are connected into a complete circular ring in the cylinder body by using a radius fine-tuning bolt. In this way, the contact area between the tool and the cylinder body can be maximized. When the cylinder body is not round, a force bolt is used for adjustment. When the end of the force bolt contacts the inner wall, a gap that is convenient for measurement can be left, and the contact between the cylinder body and the semicircular arc plate will not be reduced due to the bolt extending too long from the arc plate, thereby reducing stability.

[0053] A method for using a welding and anti-deformation tool for a thin-walled sealed container is as follows: before installing the tool, first measure the major and minor diameters of the inner wall of the container. After confirming the direction of the major diameter, tighten the four force bolts at the edge of the semi-arc plate, and complete the initial fixation when the distance the bolts extend out of the arc plate is measured to be equal. The next step is to tighten the other four force bolts until the ends contact the inner wall of the container, and then begin to symmetrically adjust the distance the force bolts extend out of the semi-arc plate until the final measurement of the extension lengths of the eight bolts are all equal, which can be used to determine that the correction is complete. For individual severely deformed containers, the inner diameter shape is more elliptical. At this time, the radius fine-tuning bolts between the two semi-arc plates can be adjusted to facilitate the contact and positioning of the force bolts with the major diameter direction of the inner wall of the container.

[0054] Example 3

[0055] like Figure 1-5 As shown, a welding and anti-deformation tool for thin-walled sealed containers, the present invention is applicable to the installation of thin-walled container barrels and heads with a diameter of 400mm-2500mm and a wall thickness of less than or equal to 16mm. According to the inner diameter of the thin-walled barrel, two semicircular rings with an outer diameter equal to the inner diameter of the barrel and a width of one tenth of the inner diameter of the barrel are made, and 20mm is removed from both ends of the semicircular rings so that they can be smoothly unfolded on the inner wall of the barrel. Welding pads and hexagonal nuts are welded at the ends of the semicircular plates, and the semicircular plates on both sides are connected by radius fine-tuning bolts.

[0056] According to the material and wall thickness of the thin-walled barrel, 8 positioning nuts are welded evenly, and the force bolts are passed through the positioning nuts radially. Adjust the radius fine-tuning bolts so that the outer edge of the arc plate of the tooling fits the inner wall of the barrel to more than 1 / 2. Divide the barrel into eight equal parts in terms of roundness, measure the positive and negative values ​​of the roundness error of the barrel, and adjust the unscrewing size of the force bolt according to the roundness of the barrel (unscrew the force bolt with the closest negative roundness error value to a size equal to the error value), observe the changes in the roundness of the barrel, re-measure the roundness error, and adjust again until the roundness of the barrel is guaranteed to match the roundness of the head. This tooling can provide uniform circumferential force during welding, thereby improving the control of welding deformation.

[0057] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A welding and anti-deformation tool for thin-walled sealed containers, characterized in that: The welding and anti-deformation tooling for the thin-wall sealed container comprises a welding pad (1), a positioning nut (2), a force bolt (3), a semi-circular arc plate (4), a hexagonal nut (5) and a radius fine-tuning bolt (6). The two ends of the two semi-circular arc plates (4) are respectively provided with welding pads (1), and the radius fine-tuning bolt (6) is provided on the welding pads (1). The two semi-circular arc plates (4) are connected into a complete ring through the threads of the hexagonal nut (5) and the radius fine-tuning bolt (6). The positioning nut (2) is evenly arranged along the shape of the semi-circular arc plate (4), and the force bolt (3) is connected to the positioning nut (2) through threads.

2. The welding and anti-deformation tool for thin-walled sealed containers according to claim 1, characterized in that: The model of the positioning nut (2) is M30, the model of the force bolt (3) is M30*150, and the model of the radius fine-tuning bolt (6) is M16*90.

3. The welding and anti-deformation tool for thin-walled sealed containers according to claim 1, characterized in that: If the thin-wall sealed container is made of stainless steel, the semicircular plate (4), the positioning nut (2), the force bolt (3), the hexagonal nut (5) and the radius fine-tuning bolt (6) are made of 304 stainless steel plate; if the thin-wall sealed container is made of carbon steel, the semicircular plate (4) is made of Q235B steel plate, and the positioning nut (2), the force bolt (3), the hexagonal nut (5) and the radius fine-tuning bolt (6) are made of 35CrMoA.

4. The welding and deformation prevention tooling for thin-walled sealed containers according to claim 1, characterized in that: The positioning nuts (2) are symmetrically arranged along the central axis of the semicircular plate (4) and are evenly arranged at intervals of 45 degrees on the semicircular plate (4). The positioning nuts (2) are evenly distributed on the outer edge of the semicircular plate (4).

5. The welding and deformation prevention tooling for thin-wall sealed containers according to claim 1, characterized in that: The radius fine-tuning bolt (6) can fine-tune the tooling size by 0-20 mm.

6. A method for manufacturing a welding and anti-deformation tool for a thin-wall sealed container as described in claims 1-5, characterized in that: The specific steps of the production method are: Step 1: According to the inner diameter of the thin-wall sealed container, two semicircular arc plates (4) are manufactured, the outer diameter of which is equal to the inner diameter of the container body and the width of which is one tenth of the inner diameter of the container body; Step 2: Remove 20 mm from each end of the semicircular arc plate (4), weld a welding pad (1) at a distance of 10 mm from the end of the semicircular arc plate (4), and weld a hexagonal nut (5) on the welding pad (1); Step 3: Four positioning nuts (2) are welded on the plate surface of each semicircular plate (4) at intervals of 45 degrees, and the force bolt (3) passes radially through the end of the positioning nut (2) on the side close to the center of the semicircular plate (4).

7. A method for using a welding and deformation prevention tool for a thin-wall sealed container as claimed in claims 1 to 5, characterized in that: The specific steps of the method of use are: Step 1: Before installing the anti-deformation tooling, first measure the positive and negative errors of the inner wall diameter of the thin-wall sealed container, and mark the data deviation on the outer wall corresponding to the thin-wall sealed container body. After confirming the deviation position, adjust the position with the largest negative deviation to a horizontal state; connect the two semi-circular arc plates (4) together by screwing the radius fine-tuning bolt (6) onto the hexagonal nut (5), and screw the radius fine-tuning bolt (6) to the root to make the two semi-circular arc plates fit together; Step 2: Place the anti-deformation tool inside the thin-wall sealed container, so that the radius fine-tuning bolt (6) is located in the vertical direction, and by screwing the radius fine-tuning bolt (6), the tool diameter is expanded in the horizontal direction until the outer edge of the anti-deformation tool is equal to or close to the maximum diameter of the inner wall of the thin-wall sealed container in the horizontal direction, and then screw the eight force bolts (3) onto the positioning nuts (2) so that the eight force bolts (3) are in contact with the inner wall of the thin-wall sealed container, thereby completing the initial fixation; Step 3: Divide the thin-walled sealed container in step 2 into eight equal parts in the direction of roundness, and measure the positive and negative values ​​of the errors at the eight equal parts of the thin-walled sealed container with a ruler again. According to the roundness of the thin-walled sealed container, adjust the screw-out size of the force bolts (3), that is, recover the size of the two force bolts (3) with positive roundness error values ​​to half of the positive error value, and screw out the two force bolts (3) with negative roundness error values ​​to half of the negative error value; then re-measure the roundness error with a ruler, check the change of the roundness of the thin-walled sealed container body, and adjust again with the same method until the roundness of the thin-walled sealed container is finally measured and guaranteed, and it can be determined that the calibration is completed; Step 4: When there is an error in the roundness of the head, you can refer to the above method for correction, and then connect the thin-walled sealed container with the head after adjustment.

8. The method for using the welding and deformation prevention tooling for thin-walled sealed containers according to claim 7, characterized in that: When the tooling diameter is expanded in the horizontal direction in the step 2, if the tooling cannot be expanded to the inner diameter of the container due to large resistance, the tooling should be expanded to a maximum size close to the inner diameter of the container and larger than the load-reducing deviation size of the barrel diameter.

9. The method for using the welding and deformation prevention tooling for thin-wall sealed containers according to claim 7, characterized in that: In step 3, the roundness error is re-measured by a ruler and no adjustment is required if it is within 1 mm.

Images