Patent ID: 11878369
Assignee: CHENGRUI ZHANG
Field: Machine tools (Mechanical engineering)
Classification: CPC B  Y | IPC B

Claim 0:
1. A laser scanning welding method for lap joints based on linear energy density regulation comprises:
step 1: wiping welding surfaces of two metal plates of a same material with anhydrous ethanol to remove surface oil stains and dust, ensuring that there is no gap between the two metal plates during overlap;
step 2: placing the two metal plates of the same material in an overlapping manner on a welding operation platform, and clamping the two metal plates with fixtures to ensure that relative positions of the two overlapping mental plates are fixed during a welding process;
step 3: adjusting a position of a welding focus plane to make a laser focal plane locate on an upper plate plane of the two overlapping metal plates and a deflecting angle of a scanning galvanometer be 5° to prevent a laser from reflecting and burning a laser head along an original direction;
step 4: setting process parameters of laser scanning welding;
step 5: calculating parameters of a circular scanning power regulation strategy and setting power correction values for a lower plate of the two overlapping metal plates, wherein the parameters of the circular scanning power regulation strategy are determined by a method as follows:
obtaining a time interval t between adjacent power regulation positions through a formula (1) as follows:, t
      =
      
       1
       
        f
        ·
        N
       
      
     
     ;
    
   
   
    
     (
     1
     )
    
   
  
 

wherein, in the formula (1), f is a scanning frequency of the scanning galvanometer, the scanning frequency is the number of cycles of a laser beam on a scanning pattern per unit time, and a unit of the scanning frequency is hertz (Hz); and N is the number of segments for segmented power regulation, power regulation values are different between different power regulation segments, and power regulation values of same power regulation segments are the same, i.e., a precision of power regulation is limited by the number of segments N for the segmented power regulation, the higher the number of the segments, the higher the precision of the power regulation, therefore, a power regulation strategy is adjusted according to the number of the segments N for the segmented power regulation;
obtaining a central angle θi corresponding to an ith power regulation position of circular scanning;
wherein main control information issued by an upper computer comprises laser beam position information and laser device power information, and a value of θi is obtained through a formula (2) as follows:, θ
       i
      
      =
      
       
        
         360
         ⁢
         °
        
        N
       
       ·
       j
      
     
     ;
    
   
   
    
     (
     2
     )
    
   
  
 

in the formula (2), within a same cycle, a value range of i is related to the number of the segments N for the segmented power regulation, and the value range of i is obtained through a formula (3) as follows:

0≤i≤N−1  (3);

after obtaining the value range of i from the formula (3), obtaining an angle increment Δθ of the adjacent power regulation positions through the formula (2);
obtaining a projection distance xi of the adjacent power regulation positions of the scanning galvanometer along a direction perpendicular to a welding direction, wherein xi at the ith power regulation position is obtained through a formula (4) as follows:, x
       i
      
      =
      
       
        A
        2
       
       ·
       
        
         ❘
         "\[LeftBracketingBar]"
        
        
         
          sin
          ⁡
          (
          
           
            θ
            i
           
           +
           
            Δ
            ⁢
            θ
           
          
          )
         
         -
         
          sin
          ⁢
          
           θ
           i
          
         
        
        
         ❘
         "\[RightBracketingBar]"
        
       
      
     
     ;
    
   
   
    
     (
     4
     )
    
   
  
 

in the formula (4), A is a scanning amplitude, which is a maximum distance of the scanning pattern along the direction perpendicular to the welding direction; when the scanning pattern is a circle, the scanning amplitude A is a diameter of the circle;
using linear energy density of the laser beam to represent a magnitude of laser energy per unit length with a unit of the linear energy density being joule per millimeter (J/mm); and obtaining linear energy density wi of the circular scanning on the direction perpendicular to the welding direction through a formula (5) as follows:, w
       i
      
      =
      
       
        
         p
         i
        
        ·
        t
       
       
        x
        i
       
      
     
     ;
    
   
   
    
     (
     5
     )
    
   
  
 

wherein, in the formula (5), pi is a power regulation value of a laser device on the ith power regulation position, and t is the time interval between the adjacent power regulation positions, which is determined by the formula (1);
substituting the formula (4) into the formula (5) to obtain a relationship among the linear energy density wi, the central angle θi, and the power regulation value pi of the circular scanning on an x-axis through a formula (6) as follows:, w
       i
      
      =
      
       
        
         p
         i
        
        ·
        t
       
       
        
         A
         2
        
        ·
        
         
          ❘
          "\[LeftBracketingBar]"
         
         
          
           sin
           ⁡
           (
           
            
             θ
             i
            
            +
            
             Δ
             ⁢
             θ
            
           
           )
          
          -
          
           sin
           ⁢
           
            θ
            i
           
          
         
         
          ❘
          "\[RightBracketingBar]"
         
        
       
      
     
     ;
    
   
   
    
     (
     6
     )
    
   
  
 

taking a power regulation value p0 of a first power regulation position as a reference power regulation value, and obtaining, based on a principle of same linear energy density of different power regulation positions on the x-axis, a relationship between the power regulation value p0 of the first power regulation position and the power regulation value pi of the ith power regulation position through a formula (7) as follows:, p
         0
        
        ·
        t
       
       
        
         A
         2
        
        ·
        
         
          ❘
          "\[LeftBracketingBar]"
         
         
          
           sin
           ⁡
           (
           
            
             θ
             0
            
            +
            
             Δ
             ⁢
             θ
            
           
           )
          
          -
          
           sin
           ⁢
           
            θ
            0
           
          
         
         
          ❘
          "\[RightBracketingBar]"
         
        
       
      
      =
      
       
        
         p
         i
        
        ·
        t
       
       
        
         A
         2
        
        ·
        
         
          ❘
          "\[LeftBracketingBar]"
         
         
          
           sin
           ⁡
           (
           
            
             θ
             i
            
            +
            
             Δ
             ⁢
             θ
            
           
           )
          
          -
          
           sin
           ⁢
           
            θ
            i
           
          
         
         
          ❘
          "\[RightBracketingBar]"
         
        
       
      
     
     ;
    
   
   
    
     (
     7
     )
    
   
  
 

wherein, in the formula (7), the first power regulation position serves as a starting position, thereby θ0=0° and sin θ0=0;
using the reference power regulation value p0 to represent the power regulation value pi of the ith power regulation position, and obtaining the power regulation value pi through a formula (8) as follows:, p
       i
      
      =
      
       
        
         p
         0
        
        |
        
         
          sin
          ⁡
          (
          
           
            θ
            i
           
           +
           
            Δ
            ⁢
            θ
           
          
          )
         
         -
         
          sin
          ⁢
          
           θ
           i
          
         
        
        |
       
       
        sin
        ⁡
        (
        
         Δ
         ⁢
         θ
        
        )
       
      
     
     ;
    
   
   
    
     (
     8
     )
    
   
  
 

when power values of the laser scanning welding are not regulated, obtaining an input energy E0 for each scanning cycle through a formula (9) as follows:

E0=P·T  (9);

wherein, in the formula (9), P is an initial laser power when the power values of the laser scanning welding are not regulated, and T is a scanning cycle of the scanning welding, which is obtained from the scanning frequency f, then T is obtained through a formula (10) as follows:, T
      =
      
       1
       f
      
     
     ;
    
   
   
    
     (
     10
     )
    
   
  
 

based on input energies remaining unchanged after the power values of the laser scanning welding are regulated and before the power values of the laser scanning welding are regulated, a formula (11) is obtained as follows:, P
       ·
       T
      
      =
      
       
        
         ∑
          
        
        
         i
         =
         0
        
        
         N
         -
         1
        
       
       ⁢
       
        
         p
         i
        
        ·
        t
       
      
     
     ;
    
   
   
    
     (
     11
     )
    
   
  
 

substituting the formulas (1), (8), and (10) into the formula (11) to obtain the reference power regulation value p0 through a formula (12) as follows:, p
       0
      
      =
      
       
        N
        ·
        P
        ·
        
         sin
         ⁡
         (
         
          Δ
          ⁢
          θ
         
         )
        
       
       
        
         
          ∑
           
         
         
          i
          =
          0
         
         
          N
          -
          1
         
        
        ⁢
        
         
          ❘
          "\[LeftBracketingBar]"
         
         
          
           sin
           ⁡
           (
           
            
             θ
             i
            
            +
            
             Δ
             ⁢
             θ
            
           
           )
          
          -
          
           sin
           ⁢
           
            θ
            i
           
          
         
         
          ❘
          "\[RightBracketingBar]"
         
        
       
      
     
     ;
       
     and
    
   
   
    
     (
     12
     )
    
   
  
 

wherein, in the formula (12), the number of the segments N for the segmented power regulation and the initial laser power P of the process without the regulation are both known or settable, thereby the reference power regulation value p0 is obtained; then, the power regulation value pi of the ith power regulation position is obtained from the relationship between the reference power regulation value p0 and the power regulation value pi in the formula (8); and
step 6: processing according to the circular scanning power regulation strategy and the power correction values, and completing a lap welding of the two metal plates of the same material.