Description:A METHOD FOR DETERMINING DISTORTION AND DIMENSIONAL ACCURACY IN WELDING AND ADDITIVE MANUFACTURING

FIELD OF INVENTION:

[001] This invention is directed to a method for determining distortion and dimensional accuracy in welding and additive manufacturing.

[002] The invention makes the use of a simple camera image and MATLAB image processing toolbox to accurately capture/measure the distortion/warpage in welding and dimensions in additive manufacturing.

BACKGROUND OF INVENTION/PRIOR ART:

[003] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[004] Fusion welding process involves the application of heat for melting both the consumable, if used and base material locally to effect joining of materials by solidification of the molten pool. Application of localized heat input in fusion welding leads to the distortion, which results from the expansion and contraction of the weld and the adjacent base metal during the heating and cooling cycle of the welding process leading to change in dimensions. Additive manufacturing (AM) is a modification/extension of a welding process, wherein the entire component/shape is made by melting the consumable using a fusion welding process and deposition of material layer by layer instead of localized joining as in the case of welding. In case of both welding and Additive manufacturing (AM), the dimensional accuracy of the welded or built component is of prime importance to ensure its suitability for the intended application. Hence, distortion, if occurred, has to be corrected which involves huge time and money. In case of AM, the control is even more critical. On the other hand, measurement of angular distortion accurately in plates will help in devising a suitable correction mechanism or to prevent it from occurring by presetting in the reverse direction before welding. When it comes to 2-Dimensional buckling, it is complex to measure to calculate the clamping force required to clamp the sheet before welding. An accurate measurement and extent of buckling in different directions can aid in designing a suitable fixturing/clamping mechanism. Also, understanding the extent and direction of distortion can help in devising the proper sequence to prevent it from occurring.

[005] Different techniques, both contact and non-contact types are available for measuring the change in dimensions or dimensional accuracy. The available non-contact types are laser or optical based Coordinate Measuring Machine (CMM) based or CT scan based systems, which are expensive.

[006] In view of the above, a simple non-contact tool for measuring the dimensions will be of great use in weld based manufacturing.

PRIOR ART :

[007] The technique of using a simple image capturing and comparing with the stored intensity data to accurately detect/measure the distortion and buckling angle is not reported before. However, reference may be made to the following:

[008] EU patent WO2021127762A1 discloses an image capturing and image formation of the V-groove in the butt-welding using industrial camera to estimate the volume of the metal inside the groove after welding. This system is also used for making corrections in the welding parameters to adjust itself to the volume deposited per pass.

[009] EU patent CN108620714B relates to online image capturing and analysis of the GMAW welding process to detect the deviation of the electrode from the molten pool.

[0010] EU patent CN106141382A is directed to the welding groove edge detection to automatically correct the position of the welding electrode position towards the centre of the molten pool.

[0011] EU patent CN109752384A relates to the use of image capturing and analysis to automatically detect the defect in a welded box.

[0012] EU patent CN110899973A pertains to the use of image analysis technique to find out the correlation between wire morphology and surface defects in welded steel strips to adjust the wire feeding system and achieve the desired quality.

[0013] All the prior arts mentioned above are discussing the use of image analysis technique for seam tracking, defect identification, etc. and none of the arts did an attempt to find the distortion angle using the edges of the welded specimen.

[0014] Conventional measurement of the distortion uses the mechanical dial gauge and buckling in sheet metal is measured by tracing the path of the edge using a ruler. Both of these methods are both time consuming and inaccurate. Buckling usually happens in two planes. To capture buckling in two planes is difficult with the ruler tracing method. Alternately, expensive non-contact CMM or CT based systems are used.

[0015] The present invention is pertinent to determination of the distortion, buckling angles and slopes of the welded plate and sheet using a simple image capturing and analysis.

OBJECTS OF THE INVENTION:

[0016] Primary object of the invention is to provide a method for determining distortion and dimensional accuracy in welding and additive manufacturing, which is simple.

[0017] An object of the present invention is to provide a method for determining distortion and dimensional accuracy in welding and additive manufacturing, which uses a simple RGB image based technique for determination of distortion angle of the welded plate.

[0018] Another objective of the invention is to provide a method for determining distortion and dimensional accuracy in welding and additive manufacturing, which determines the localized buckling angle and slope of the welded sheet metal using the same technique.

[0019] Still another objective of the invention is to provide a method for determining distortion and dimensional accuracy in welding and additive manufacturing, which uses the technique for measurement of dimensions/accuracy of additive manufactured component.

[0020] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION:

[0021] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0022] In the instant invention a camera is used to capture the images of the part/component in three directions and the image processing is performed using MATLAB to accurately detect the distortion in welding or the dimensional accuracy of the component in additive manufacturing. A normal RGB camera is used to capture the image of the plates and sheets before welding. RGB (Red Green Blue) image taken using the camera prior to welding shall be stored in the MATLAB as an array of matrix consisting of data as the intensity of red, green and blue colors. After welding, with an undisturbed set up, an image is captured post-welding. Sudden change in intensity is used to define the edge of an object. The detected edge is extracted and compared with the pre welded image of the work piece to evaluate the distortion angle. The first image is used as a base to estimate the distortion angle of the welded plate. The same principle is used to estimate the local slope and angle of the 2-D buckling in sheet metal welding.

[0023] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0024] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0025] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[0026] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

Figure 1 shows: the detected edge image of the captured RGB image from an RGB camera, wherein the 1st image in that figure is the reference image, through which the distortion is measured and with that as reference, the second image shows the post welded detected edge image with the distortion angle measured with respect to the 1st image.
Figure 2 shows: the control points obtained from the buckled sheet metal post welding.
Table 1 shows: table regarding the slope and angle of each control point obtained.

[0027] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0028] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0029] Weld distortion occurs due to the localized heating of joint edges to fuse the material, which creates non-uniform stresses in the component because of expansion and contraction of the heated material. Initially, compressive stresses are created in the surrounding cold parent metal when the weld pool is formed due to the thermal expansion of the hot metal or heat affected zone (HAZ)) adjacent to the weld pool. The pattern reverses and tensile stresses occur on cooling when the contraction of the weld metal and the immediate HAZ is resisted by the bulk of the cold parent metal. The magnitude of the thermal stresses induced into the material can be seen by the volume change in the weld area on solidification and subsequent cooling to room temperature.

[0030] If the stresses generated from thermal expansion/contraction exceed the yield strength of the parent metal, localized plastic deformation occurs. Plastic deformation causes a permanent change in the component dimensions and distorts the structure. In case of additive manufacturing, the repeated heating and cooling to building layer by layer may lead to warpage due to the combined effect of various forces encountered by the build.

[0031] It is difficult to predict the weld shrinkage dimensions prior to welding precisely.
[0032] Also, in order to preset the metal before welding, a sample welding with similar conditions can be done to measure the degree of distortion after welding. The distorted angle is measured to preset the joint prior to welding so that the desired weld joint is achieved post welding.

[0033] The present invention makes a disclosure regarding a technology pertaining to a method for determining distortion and dimensional accuracy in welding and additive manufacturing.

[0034] In the present invention, an image capturing and analysis method is designed as a non-contact tool to measure the distortion or change in dimensions. Prior welding, images of the plate/sheet are captured in all the three axes. The captured image is stored and made as a reference. After welding, images of the component are again taken in all the three directions. The captured images after welding are compared with the reference image using the MATLAB image processing toolbox. The change in shape/dimensions with respect to the original image is measured to capture the distortion that has happened in the structure because of welding.

[0035] According to another embodiment of the invention, the technique can also be used to determine the buckling in both the planes with localized angles and slopes from the captured post welding image.

[0036] The distortion profile and angle for a welded plate measured using the described technique is shown in Fig. 1. The buckling profile of the sheet metal is shown in Fig.2. The angle and slope of the obtained points are shown in Table 1.

The present invention has the following provisions:
- A method suitable for detecting edge from a normal RGB image.
- A simple optical based non-contact method suitable for obtaining distortion angle.
- An optical based method suitable for obtaining local control points, slopes and angles of the buckled sheet.
- A method to measure the dimensions of additive manufactured component.

ADVANATGESOF THE INVENTION:
- Simple in construction;
- Cost effective;
- Efficiently serves the purpose;
- User friendly.

WORKING OF THE INVENTION:
- Capturing images of the plate/sheet in the three axes Prior to welding;
- Storing the captured image, which is made as a reference;
- Taking images of the component in the three directions post welding;
- Comparing the captured images after welding with the reference image by image processing toolbox;
- Determination of the change in shape/dimensions with respect to the original image to capture the distortion that has occurred in the structure because of welding.

[0037] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0038] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0039] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0040] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0041] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0042] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0043] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:WE CLAIM:

1. A method for determining distortion and dimensional accuracy in welding and additive manufacturing comprising steps of:
- capturing images of the plate/sheet in the three axes Prior to welding;
- storing the captured image, which is made as a reference;
- taking images of the component in the three directions post welding;
- comparing the captured images after welding with the reference image by image processing toolbox;
- determination of the change in shape/dimensions with respect to the original image to capture the distortion that has occurred in the structure because of welding.

2. The method as claimed in claim 1, wherein the image processing toolbox includes MATLAB.

3. The method as claimed in claim 1, wherein the technique is used to determine the buckling in both the planes with localized angles and slopes from the captured post welding image.