Patent Publication Number: US-2007095802-A1

Title: Laser treatment apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is related to commonly-assigned co-pending applications entitled, “LASER WELDING SYSTEM FOR WELDING WORKPIECE”, filed on Jun. 23, 2006 (U.S. application Ser. No. 11/473,965), “LASER SYSTEM AND METHOD FOR PATTERNING MOLD INSERTS”, filed on Jul. 28, 2006 (U.S. application Ser. No. 11/309,343), and “APPARATUS FOR PROCESSING WORK-PIECE”, filed on Jul. 31, 2006 (U.S. application Ser. No. 11/309,353). Disclosures of the above identified applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
      The present invention relates to treatment apparatuses, and particularly to a laser treatment apparatus.  
     DISCUSSION OF RELATED ART  
      Lasers have been used for surface treatments such as marking and machining of materials since shortly after their invention. Established techniques include laser cutting, laser drilling, and laser welding. These techniques have been applied to a wide range of materials including metals, ceramics, polymers, and natural products such as cotton and paper.  
      When using lasers to treat a workpiece, laser radiation is usually focused into a focal spot on the surface of a workpiece being treated and delivered in a sequence of pulses. Generally, laser treatment apparatuses make use of ablation and removal of unwanted materials of the workpiece as a result of melting and evaporation. Techniques involving laser treatment apparatuses have some advantages over other such techniques including higher efficiency and speed.  
      Several problems may be encountered in performing such laser treatment operations. For example, some molten materials maybe not evaporate in time during treatment, and the molten material that does not evaporate is deposited on the treatment region of the workpiece, causing heat to disperse non-uniformly. A number of recast layers and micro-cracks are formed on the treated surface of the workpiece thus reducing surface quality.  
     SUMMARY  
      An exemplary embodiment of the present laser treatment apparatus is provided.  
      The laser treatment apparatus includes a laser generation unit for applying a laser beam to a workpiece; a control unit configured for regulating and controlling laser generation of the laser generation unit; a focusing unit configured for focusing the laser beam generated by the laser generation unit onto the workpiece; a table for supporting the workpiece; at least one thermal electric cooler configured on the table for dissipating heat from a treatment position; and a feedback unit for receiving the laser beams reflected from the surface of the workpiece and generating and feeding a corresponding feedback signal according to the received laser beams back to the control unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Many aspects of the present laser treatment apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present laser treatment apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a schematic view of a laser treatment apparatus in accordance with a preferred embodiment; and  
       FIG. 2  is a schematic, enlarged view showing surface roughness of a product treated by the laser treatment apparatus of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Reference will now be made to the drawings to describe in detail the preferred embodiments of the present laser treatment apparatus.  
      Referring to  FIG. 1 , a laser treatment apparatus  100  according to a preferred embodiment of the present invention is shown. The laser treatment apparatus  100  includes a laser generation unit  110 , a control unit  120 , a focusing unit  130 , a table  140 , at least one thermal electric cooler  150  arranged on the table  140 , and a feedback unit  160 .  
      The laser generation unit  110  includes a laser  112 , a cooling system  114 , and a blocking shutter  116 . The laser  112  is adapted for generating a laser beam  118 , and can be a high power solid-state laser, such as Nd: GdVO4 (neodymium doped gadolinium vanadate) laser with a wavelength of 1060-1340 nm, Nd:YAG (neodymium yttrium aluminium garnet) laser with a wavelength of 1064 nm, or Nd: YVO4 (neodymium doped yttrium orthovanadate) laser with a wavelength of 1064 nm. Preferably, the laser  112  is a laser diode pumped solid-state laser. The cooling system  114  is attached to the laser  112  for regulating a temperature of the laser  112 . The blocking shutter  116  is configured for allowing the laser beam  118  to pass through itself and for regulating exposure of the workpiece to the laser beam  118  according to the control unit  120 . For example, if the blocking shutter  116  is completely opened, the laser beam  118  completely passes through the blocking shutter  116 . In this case, the exposure of the workpiece is maximum. If the blocking shutter  116  is completely closed, the laser beam  118  cannot pass through the blocking shutter  116 . In this case, the exposure of the workpiece is minimum.  
      The control unit  120  includes a data processor  122  and a controller  124 . The data processor  122  is adapted for processing the feedback signal from the feedback unit  160  and updating controlling parameters stored therein. The feedback signal can consist of information about a distance between the treatment position  220  of the workpiece  200  and the focusing unit  130 . The controller  124  is adapted for regulating and controlling the laser generation unit  110  to generate the laser beam  118  according to the updated controlling parameters of the data processor  122 . The updated controlling parameters of the data processor  122  include at least one of the following factors: laser pulse power, laser pulse energy, laser pulse duration, laser pulse repetition rate, and laser wavelength.  
      The focusing unit  130  includes a number of lenses configured for focusing the laser beam  118  onto the treatment position  220 .  
      The table  140  can be structured and arranged to be movable vertically and horizontally so that different positions on the workpiece  200  can be treated by the laser.  
      The at least one thermal electric cooler  150  is attached on a surface of the table  140  for dissipating heat from the treatment position  220 , and the at least one thermal electric cooler  150  can be disposed at any position of the surface of the table  140  according to need.  
      The feedback unit  160  includes a photoelectric detector. The feedback unit  160  is adapted for receiving the laser beams reflected from the surface of the workpiece  200  and generating and feeding the corresponding feedback signal according to the received laser beams back to the control unit  120 .  
      The laser treatment apparatus  100  further include a clamp  180  for fixing the workpiece  200 .  
      In addition, the laser treatment apparatus  100  may further include a gas blowing device  170 . The gas blowing device  170  is configured for blowing gas onto the treatment position  220  of the workpiece  200  to accelerate the evaporation of a gaseous portion of the workpiece  200  melted by the laser beam  118 . The gas blowing device  170  can be connected with the control unit  120  and be controlled by the control unit  120 .  
      A process for treating a workpiece with above-described laser treatment apparatus  100  should include the steps of:  
      (1) setting controlling parameters in the data processor  122 ;  
      (2) controlling the laser  112  to generate the laser beam  118  according to the controlling parameters from the data processor  122 ;  
      (3) placing a workpiece  200  on the table  140  and fixing it in place with a clamp  180 ;  
      (4) opening the blocking shutter  116  and directing the laser beam  118  into the blocking shutter  116  and focusing it onto the treatment position  220  of the workpiece  200 ;  
      (5) receiving the laser beams reflected from the surface of the workpiece  200  and generating and feeding a corresponding feedback signal of the position of the surface being treated on the workpiece  200  according to the received laser beams back to the control unit  120 ;  
      (6) processing the feedback signals by the data processor  122  to obtain updated controlling parameters and transmitting the updated controlling parameters to the controller  124 ;  
      (7) regulating the laser generation of the laser  112  according to the updated controlling parameters received by the controller  124 ;  
      (8) repeating the steps (2) to (7) until the workpiece  200  is processed and treated into a satisfactory product.  
      The workpiece can be made of steel, aluminum alloy, manganese alloy, titanium alloy, nickel alloy, tin alloy, copper alloy, lead alloy, and all kinds of low carbon steels.  
      Referring to  FIG. 2 , a schematic view showing a surface roughness of a product  300  treated by the laser treatment apparatus  100  is shown. The arithmetical mean deviation of the surface profile of the product  300  is labeled with a character Ra and the maximum peak height of the surface profile of the product  300  is labeled with a character Rp. Ra of the product  300  treated by the laser treatment apparatus is in the range from about 0.5 nm to 2 nm and Rp is in the range from about 1.5 nm to 6 nm. Therefore, the treated surface of the product  300  can be considered to be smooth.  
      An advantage of the laser treatment apparatus  100  is that the laser  112  can be adjusted during treatment, and the thermal electric cooler  150  can remove the superfluous heat formed by the molten material without evaporation in time to avoid recast layers and micro-cracks being formed on the treated surface of the product  300 .  
      While the present invention has been described as having preferred or exemplary embodiments, the embodiments can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the embodiments using the general principles of the invention as claimed. Furthermore, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and which fall within the limits of the appended claims or equivalents thereof.