Patent Publication Number: US-2023158605-A1

Title: Air management system for laser welding with airflow optimizing deflector

Description:
INTRODUCTION 
     The present disclosure generally relates to laser welding and more specifically, to airflow management and optimization in laser welding to avoid the effects of weld zone plume emissions for positive effects on workpiece weld quality. 
     In laser welding, a high density light source is employed to melt the material of the parts to be joined. Multiple parts are typically placed in contact with each other or with no more than a small gap at a faying interface between the parts. The laser beam is passed across the faying interface by the welding machine to fuse the parts together. At the point where the laser beam intersects the parts, a pool of melted material is formed in a heated area that comingles the material of the parts being joined. 
     In some forms of laser welding, both melted material and metal vapor may be formed. The metal vapor may displace a region of melted material in the melt pool, such as at point the laser beam enters the parts. The region of displaced material may be referred to as the keyhole. Vaporization of some material may occur, such as due to high density laser energy heating the material to a boiling point. As the vaporized material leaves the material surface, recoil pressure is generated which pushes the melt surface causing displacement. Small particles may be emitted in the form of a plume of opaque material. The plume may dampen the laser beam during its route to the workpiece. The metal vapor may also agglomerate into larger sized particles, which when approaching or surpassing the size of the laser beam&#39;s wavelength, may significantly attenuate the laser&#39;s power from reaching the workpiece. Effects of the plume may include inconsistency of laser power reaching to the material which may cause quality issues such as insufficient laser penetration, spatters, and cavities. 
     Accordingly, it is desirable to provide systems for laser welding that effectively and efficiently overcome the effects associated with plume formation and other emissions. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     SUMMARY 
     In various embodiments, systems with air management aspects are provided for laser welding to reduce the effects of plume forming actions and for optimizing airflow with deflectors. In a number of embodiments, a system for a welder includes a blower to generate an airflow stream. A plenum receives the airflow stream, directs it toward the workpiece, and defines an outlet facing the workpiece to expel the airflow stream toward the workpiece. A deflector adjacent the outlet is formed as a conical section converging from the plenum toward the workpiece, and is defined by an angled wall with an open center. The deflector concentrates the airflow stream to impart a velocity increase to the airflow stream after leaving the outlet and to impart a favored directional component to the airflow stream toward a weld zone. 
     In additional embodiments, the deflector includes a smooth surface that the airflow stream follows, and the smooth surface is configured to reduce turbulence of the airflow stream. 
     In additional embodiments, the angled wall of the deflector is disposed at an angle in a range of approximately 35-40 degrees relative to vertical. 
     In additional embodiments, the deflector extends from a top proximate the plenum to a bottom distant from the plenum, wherein the top is disposed radially inside the opening, in entirety. 
     In additional embodiments, the deflector extends from a top proximate the plenum to a bottom distant from the plenum, wherein the top is disposed radially outside the opening, in entirety. 
     In additional embodiments, the deflector has a height in a direction from the plenum toward the workpiece, of approximately three centimeters. 
     In additional embodiments, the deflector is formed by additive manufacturing with a surface quality configured to limit airflow friction. 
     In additional embodiments, the welder is configured to generate a laser beam configured to follow a path. The plenum is an annular shaped plenum with an open center. The deflector is an annular shaped deflector with an open center aligned with the plenum&#39;s open center around the path of the laser beam. 
     In additional embodiments, the deflector is joined to the plenum with an airtight joint. 
     In additional embodiments, the welder includes a fixture with clamps configured to engage the workpiece. The weld zone is defined between the clamps and the deflector is configured to concentrate and direct the airflow stream to a point between the clamps. 
     In a number of additional embodiments, a welder is configured to weld a workpiece at a weld zone. A blower is configured to generate an airflow stream and a plenum is coupled with the blower to receive the airflow stream and to direct the airflow stream toward the workpiece. The plenum defines an annular outlet configured to face toward the workpiece and to expel the airflow stream toward the workpiece. A deflector is disposed adjacent the outlet, and is formed as a conical section converging from a top proximate the plenum to a bottom distant the plenum. The deflector is defined by an annular wall with an open center to concentrate the airflow stream to impart a velocity increase to the airflow stream after leaving the outlet and to impart a directional component to the airflow stream toward the weld zone. 
     In additional embodiments, the deflector includes a smooth surface adjacent the airflow stream. The airflow stream follows the smooth surface and the smooth surface reduces turbulence of the airflow stream. 
     In additional embodiments, the annular wall of the deflector is disposed at an angle in a range of approximately 35-40 degrees relative to vertical, and the deflector is axisymmetric. 
     In additional embodiments, the top of the deflector is disposed radially inside the opening, in entirety. 
     In additional embodiments, the top of the deflector is disposed radially outside the opening, in entirety. 
     In additional embodiments, the deflector has a height from the top to the bottom, of no more than three centimeters. 
     In additional embodiments, the deflector is formed of a rigid material by additive manufacturing with a surface quality configured to limit airflow friction. 
     In additional embodiments, the welder generates a laser beam configured to follow a path. The plenum comprises an annular shaped plenum with an open center. The deflector comprises an annular shaped deflector also with an open center. The open centers are aligned around the path of the laser beam, and the deflector extends radially inward further than the plenum. 
     In additional embodiments, the deflector is joined to the plenum with an airtight joint. The plenum is spaced from the welder by a gap, and the deflector is configured to induce an induced flow through the gap. 
     In a number of other embodiments, a system includes a welder configured to weld a workpiece at a weld zone. A blower is configured to generate an airflow stream. A plenum is configured to receive the airflow stream and to direct the airflow stream toward the workpiece. The plenum defines an annular outlet configured to face toward the workpiece and to expel the airflow stream toward the workpiece. A deflector is disposed adjacent the outlet. The deflector is formed as a conical section converging from the plenum toward the workpiece. The deflector is defined by a wall with an open center. The wall is disposed at an angle of approximately 35-40 degrees relative to vertical. The deflector is configured to concentrate the airflow stream to impart a velocity increase to the airflow stream after leaving the outlet and to impart a directional component to the airflow stream toward the weld zone. The welder includes a fixture with clamps configured to engage the workpiece. The weld zone is defined between the clamps and the deflector is configured to concentrate and direct the airflow stream to a point between the clamps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG.  1    is a schematic illustration of a laser welding system, in accordance with various embodiments; 
         FIG.  2    is a fragmentary, schematic illustration of a part of the laser welding system of  FIG.  2   , showing a plenum and deflector area, in accordance with various embodiments; 
         FIG.  3    is a section view taken generally through the line  3 - 3  indicated in  FIG.  2   , in accordance with various embodiments; 
         FIG.  4    is a fragmentary, schematic illustration of a part of the laser welding system of  FIG.  2   , showing a plenum and deflector area, in accordance with various embodiments; 
         FIG.  5    is a section view taken generally through the line  5 - 5  indicated in  FIG.  4   , in accordance with various embodiments; and 
         FIG.  6    is an illustration of a welding process application of the laser welding system of  FIG.  1   , in accordance with various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     As disclosed herein, systems are provided that include airflow optimization through an air management system that creates generated, plume managing, airflow in laser welding operations. In a number of embodiments, forced and induced airflow is generated near the source of the welder&#39;s laser light beam. A deflector concentrates the airflow, increases velocity of the airflow, imparts a strong directional vector to the airflow magnitude, and counteracts airflow disturbing influences. The deflector effectively and efficiently reduces the effect of plumes and other emissions generated above a weld zone. The generated flow stream distribution consistently moves the plume away from the weld zone, avoiding laser energy loss due to plume effects and improves weld quality. In a number of embodiments, the deflector is configured as a conical section, such as a conical convergent nozzle. The deflector reduces airflow turbulence and defines an effective airflow direction. The resulting airflow enhances protection of the laser&#39;s optics lenses, and also increases airflow amount and magnitude toward the weld zone to move more plume away from the weld zone. Improvements of up to 25% gain in mass flow rate from the weld area have been demonstrated. The results include weld quality improvements. 
     With reference to  FIG.  1   , illustrated is a welding system  20  employing aspects that create optimized, generated airflow for quality weld production. In general, the welding system  20  includes a welding machine  22 , an air management system  24 , and a workpiece  28 . The welding machine  22  may be any of a variety of types of welders and in the current embodiment is a laser welding machine. As such, the welding machine  22  includes a light source  30 , a reflector  32 , optics  34 , a power supply  36  and a controller  38 . The light source  30  is powered and controlled by the power supply  36  and the controller  38  to generate light into a resonant cavity  40 . The light is expanded and then reflected by the reflector  32  through the optics  34  to emerge as a concentrated beam  42  focused to a point at the workpiece  28 . The welding machine  22  is configured to move the beam across the workpiece  28  along a designated welding route. The air management system  24  may include an airflow module  25  disposed beneath laser optics  34 . In embodiments, the optics and the airflow module may be held by robot arm/gantry system  26 . The laser power used in certain embodiments such as automotive applications may range from 1 kw to 10 kw. The generator may be configured as stand-alone equipment standing on the floor, with fiber optics delivering the laser light from the laser generator to the laser optics  34  to for laser welding. 
     The beam  42  is directed at the workpiece  28  and as such passes through an air space that is subject to air movement and contaminant exposure. The workpiece  28  may be plural parts, such as for joining at a faying interface  44 . The beam  42  is directed at the faying interface  44  creating a melt pool  50 . In the current embodiment, keyhole type laser welding is employed. As the high energy-density beam  42  traverses along the faying interface  44 , the melt pool  50  develops. The surface material being directly hit by the beam heats up to evaporation point and evaporates. As the metal vapor leaves the surface, it generates recoil pressure which forces away the melt beneath forming a deep and narrow cavity referred to as a keyhole  52  that penetrates the molten material. Near-surface plasma emissions  54  may occur and particles may flow out of the weld pool  50  and the keyhole  52  forming a plume  56 . The plume  56  may dampen the beam  42  from reaching the workpiece  28 . It has been discovered that characteristics of the plume  56  may be related to surrounding airflow velocity and direction. It has further been discovered that fixtures of the welding machine  22  proximate to the weld pool  50  create airflow profiles that exacerbate the effects of the plume  56 . For example, clamps  60 ,  62  used to hold the workpiece  28 , such as to maintain an acceptable gap size at the faying interface  44 , may create airflow vectors that direct the plume  56  into the path of the beam  42 . In addition, fixtures such as the clamps  60 ,  62  may block or redirect airflow concentrating the plume  56 . It has also been discovered that beam damping from the plume  56  may cause varying laser power decreases at the workpiece  28 . Even when employing monitoring, the controller  38  may be unable to make changes to compensate for these variations. As a result, consistently maintaining the keyhole  52  may not be possible leading to closing and opening that increases spatter, plume emissions, and may lead to reduced weld quality. In addition to damping of the beam  42  by the plume  56 , spatter may cloud or damage the optics  34  of the welding machine  22 , and is therefore undesirable. 
     Accordingly, to reduce effects of the plume  56  the current embodiment employs an air management system  24  to create an optimized airflow profile to effectively move the plume  56  out of the path of the beam  42 , including to overcome any effects such as those caused by the clamps  60 ,  62 . The air management system  24  generally includes a blower  72 , a plenum  74  and a deflector  76 . The blower  72  generates pressurized airflow that is delivered to the plenum  74 . The blower  72  may be of a variety of constructions such as a motor driven squirrel cage centrifugal fan or other arrangement. The plenum  74  may be of an enclosed annular shaped construction and may completely surround the beam  42  near its exit from the optics  34 . The plenum  74  has an open center  78  through which the beam  42  may pass. The pressurized airflow, along with induced airflow drawn through a gap  78 , is expelled through a deflector  76  toward the workpiece  28  in a stream  80 . The stream  80  is optimized to disperse the plume  56  out of the path of the beam  42  and away from the weld zone, reducing or eliminating unwanted plume  56  effects. For example, the stream  80  is generated as a vector with sufficient velocity and uniform directional strength to redirect the plume  56 . In addition, the stream  80  is directed on a relatively small area of interest that may increase the downward momentum force of the air stream  80  and overcome airflow disturbances, such as those caused by fixturing or turbulence. As a result, protection from contamination is provided for the optics  34 , and airflow in the weld zone is beneficially directed for better quality laser welding. 
     Referring to  FIG.  2   , a schematic illustration shows the area of the air management system  24  that faces the workpiece  28  (i.e. the bottom of the air management system  24  of  FIG.  1   ). The blower  72  directs airflow into the plenum  74  through a duct  82 . The plenum  74  is generally annular in shape with an open center  79 . Referring additionally to  FIG.  3   , the plenum  74  defines a chamber  84  into which the duct  82  directs airflow, and includes an outlet  86  that is directed at the workpiece  28 . In the current embodiment, the outlet  86  is in the form of an annular slot through which airflow is directed generally downward toward the workpiece  28 . The deflector  76  is attached to, or integrally formed with, the plenum  74  adjacent the outlet  86 , and at or near its bottom surface  88 . 
     The deflector  76  is shaped as a conical section defined by an annular wall  90 , and may be described as a conical convergent nozzle with an open center  89  aligned with the open center  79  of the plenum  74 . The deflector  76  is formed of a relatively thin material by the annular wall  90  with an inner surface  92  and an outer surface  94 . The bottom  96  of the deflector  76  has a smaller diameter than the top  98  of the deflector  76  drawing the airflow stream  80  toward the beam  42 . In this embodiment, the deflector  76  is disposed slightly above the bottom surface  88  so that the outlet  86  is disposed radially outside the deflector  76 . Accordingly, the airflow stream  80  exiting the outlet  86  passes along the outer surface  94  of the deflector  76 . As the stream  80  passes the bottom  96  of the deflector  76 , additional induced airflow  100  is drawn through the gap  78  joining the stream  80 . 
     Positioning the deflector  76  at or near the bottom of the plenum  74  locates the top  98  adjacent the inside  102  of the outlet  86  and proximate the plenum  74 . The bottom  96  of the deflector  76  is located distant from the plenum relative to the top  98 . This leaves the area of the outlet  86  from its inside  102  to its outside  104  completely open and unobstructed all the way to the workpiece  28 . Close proximity of the deflector  76  to the outlet  86  optimizes the ability of the deflector to define the characteristics of the stream  80  as it is directed at the workpiece  28 . This ability is improved by providing an airtight joint  106  between the top  98  of the deflector  76  and the plenum  74 . In addition, optimized airflow is created by the deflector  76  with a height  108  of three centimeters, or of approximately three centimeters, from the top  98  to the bottom  96 , and with an axisymmetric shape to create an axisymmetric stream  80 . The height  108  is selected to minimize airflow loss due to friction on the wall  90 . The material of the deflector  76  is selected to have a surface quality to limit friction and provide laminar flow with the air flowing efficiently and smoothly increasing in speed across the boundary layer. The material of the deflector  76  may be a plastic, a metal, or a polymer, exhibiting a smooth inner surface  92  to reduce turbulence and exhibiting a sufficiently rigid form to maintain shape under application of the air flow. In a number of embodiments, the deflector  76  may be economically manufactured by printing using an additive manufacture process. 
     Referring to  FIGS.  4  and  5   , an alternative placement of the deflector  76  is illustrated. In this configuration, the deflector is disposed with the top  98  of the wall  90  at the bottom surface  88 , radially outward from, and adjacent to, the outside  104  of the outlet  86 . Other attributes of the deflector  76  are the same or similar to those of the arrangement of  FIGS.  2  and  3   . The deflector  76  is again shaped as a conical convergent nozzle with an open center  89  aligned with the open center  79  of the plenum  74 . The deflector  76  is formed of a relatively thin material by an annular wall  90  with an inner surface  92  and an outer surface  94 . The bottom  96  of the deflector  76  has a smaller diameter than the top  98  of the deflector  76  directing the airflow stream  80  toward the beam  42 . In this embodiment, the deflector  76  is disposed at the bottom surface  88  so that the outlet  86  is disposed radially inside the deflector  76 . Accordingly, the airflow stream  80  exiting the outlet  86  passes along the inside surface  92  of the deflector  76 . As the stream  80  passes through the deflector  76 , additional induce airflow  100  is drawn through the gap  78  joining into the stream  80 . 
     Positioning the deflector  76  at the bottom of the plenum  74  locates the top  98  adjacent the outside  104  of the outlet  86 . This positions the deflector  76  so that is between the area of the outlet  86  from its inside  102  to its outside  104  and the workpiece  28 . Close proximity of the deflector  76  to the outlet  86  optimizes the ability of the deflector to define the characteristics of the stream  80  as it is directed at the workpiece  28 . This ability is improved by providing an airtight joint  106  between the top  98  of the deflector  76  and the plenum  74 . In addition, optimized airflow is created by the deflector  76  with a height  108  of three centimeters, or of approximately three centimeters, from the top  98  to the bottom  96 , and with an axisymmetric shape to create an axisymmetric stream  80 . The height  108  is selected to minimize airflow loss due to friction on the wall  90 . The material of the deflector  76  is selected to provide laminar flow with the air flowing efficiently and smoothly increasing in speed across the boundary layer. The material may be a plastic, a metal, or a polymer, exhibiting a smooth inner surface  92  to reduce turbulence and of a sufficiently rigid form to maintain shape under the applied air flow. Again, the deflector  76  may be economically manufactured by printing using an additive manufacture process. 
     Referring to  FIG.  6   , the welding machine  22  has a fixture  110  that includes the clamps  60  and  62 . A weld zone  112  is defined between the clamps  60  and  62  and at the workpiece  28 . Both the inner ( FIGS.  2 - 3   ) and outer ( FIGS.  4 - 5   ) locations of the deflector  76  direct the airflow stream  80  in an optimized fashion to the weld zone  112 . In each case, the deflector  76  extends radially inward further than the plenum  74 . Specifically, the stream  80  is directed between the clamps  60  and  62  and along and around the beam  42 . Up to a 25% gain in mass flow rate from the weld area has been demonstrated by inclusion of the deflector  76 . The wall  90  of the deflector  76  is angled/tapered so that it is disposed at an angle  114  relative to vertical  116 . The angle  114  is consistent around the perimeter of the deflector  76  and may be within a range of thirty-five to forty degrees (35°-40°) in magnitude relative to vertical  116 . In an embodiment, the stream  80  is optimized with an angle  114  of thirty-seven and one-half degrees (37.5°). These parameters have been found to effectively disperse and redirect the plume  56  away from the weld zone  112  and out of the path of the beam  42 . 
     Accordingly, a system includes a laser welder with an airflow management system that effectively avoids plume and spatter effects producing quality welds. Forced and induced airflow may be generated near the source of the welder&#39;s laser light beam. A deflector concentrates the generated airflow, increasing velocity and imparting a strong directional vector to the airflow magnitude. Airflow disturbing influences such as turbulence are overcome to reduce the effects of plumes generated above the weld zone. The airflow management system boosts and directs air flow onto the welding site and moves away the plume. Consistent laser energy input into the workpiece and consistent weld quality are provided. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.