Beam Propagation And Focusing Properties Of Large Format Thick Plate Laser Cutting System

This thesis was based on two projects background "High-grade CNC machine tool and basic manufacturing equipment" which was a major project of high-power wide-format thick plate CNC laser cutting machine in charge of Wuhan FARLEY Cutting System Engineering Co.Ltd.,and the Wuhan Science and Technology Bureau’s project "More than 3*12 meter large-format laser cutting equipment integrated manufacturing technology research" to analysis of large-format laser cutting machine beam transmission and focusing characteristics.The main content is for the following four parts:(1)It has been expounded for the basic principles of beam transmission in optical path of cutting machine,calculated the expander,polarization,collimation,focusing process of beam in the optical path.Finally the focus light spot in diameter of the cutting machine output when focus lens’ focal length was 7.5 inches was 0.134 mm,and the focus light spot’s depth was 17 mm,the focus light spot in diameter when focal length was 10 inches was 0.18 mm,and the focus light spot’s depth was 31 mm.(2)Light path structure was analyzed,in order to get the uniform focal spot,It has designed an equal optical path structure,the ratio of optical path compensation mirror and processing head stroke was 1:2,the optical path was L1=A+Y+B+Y+C=(A+B+C)+2Y= L2 to obtain consistent output,and emphatically analyzed the cutting head part of the structure and composition,finally selected based on the bronze mirror reflection type cutting head,and with water,auxiliary gas,focus tracking,automatic focus unit auxiliary system,etc.(3)In order to adapt to more flexible production requirements,based on the original cutting head,the zoom focus system has been designed,used a lens with a fixed lens to adjust focal length of system,after calculating,we got the relationship of moving lens displacement ΔH and focus lens displacement ΔL and the relationship of moving lens displacement ΔH and focal spot changeable size ΔD。(4)According to the result of the relationship of moving lens displacement ΔH and focal spot changeable size ΔD,we used ZEMAX software to simulate the law of the spot changes of the focusing system,whenever lens move 1 mm,spot diameter variation magnitude is about 0.1 mm,the scope of the light spot diameter control also can be adjusted between 0.3 ~ 0.7mm,corresponding to the depth of focus adjustment range of 8.5 ~ 46.5mm.The result could be used for cutting thin plate,could also satisfy the carbon steel plate cutting thickness of 30 mm,non-ferrous metal sheet cutting thickness of up to 20 mm,which proves the practical value of the device.