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Wide Spectra of Quality Control Part 16

Tham khảo tài liệu 'wide spectra of quality control part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 440 Wide Spectra of Quality Control Only bars of small section compared to the disc opening can be cut with this method. The advantage is an economy in material thanks to the narrow cutting path disc thickness plus 0 1mm max. . Processing of prismatic pieces is only possible for end cuts. Because of the limited free space within the central opening supporting tooling design is critical. The plain wire saw method as said above is now widely used for mass production of silicon wafers for electronics as for solar cells. The km long wire runs back and forth and follows a complex path to achieve multiple cutting planes on several ingots today up to seven with diameters exceeding 320mm . The abrasive slurry usually cheap corundum is poured on the wire where it holds by capillarity. The cutting action depends on the grain adherence to the wire with the result of decreasing efficiency with cut depth. Wire diameter and cutting path are comparable to internal disc saw. This method therefore requires a correction of the planarity afterwards. The specific arrangement of this equipment is only fit for slicing and has no interest for the shaping of prismatic scintillators. Wires with sintered abrasive have been successfully developed to correct the weak sides of the plain wire. Typical diameter is 0 25mm with an 80 pm diamond grain coating. The 2km wire is expensive 1 m order and fragile processing parameters and lubrication have to be carefully adapted to dedicated machine tools fig. 10 . Fig. 10. Wire saw abrasive wire Wire length 2km @ 2 m Wire O.D. 0 25mm Diamond grain 80 Hm Wire path 0 3mm Wire speed 5 to 10m s Feed 25 to 50Hm s Feeds of 50 pm per minute can be achieved with an excellent planarity and a very low subsurface damage. Parameter optimisation also aims at reducing the wire wear. By combining the feed with the crystal rotation a symmetric end-cut is possible cropping with a balanced stress relief fig. 11 . The machine open configuration allows cutting long side .