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This paper presents a novel fixed and free abrasive combined wire sawing which uses the diamond wire with surface abrasive-groups interval distribution and combines with free SiC abrasives slurry to obtain sliced surface that can be textured by acid etching. During the sawing process, the ability that the free abrasives lapping the sawn surface has a positive correlation with the elasto-hydrodynamic (EHD) pressure, and the appropriate size of the free abrasives is related to the minimum film thickness of the cutting coolant. In this paper, the EHD action during the FFACWS is analyzed, and the film thickness equation and Reynolds equation of the sawing area are deduced. The influences of feed speed, wire speed, wire tensioning force, cutting coolant viscosity, core wire diameter, and surface structure parameters on EHD pressure and film thickness are analyzed, which provides theoretical reference for selection of the free abrasives diameter and analysis of their lapping effect on the slice surface. The research results show that the EHD pressure changes periodically in the direction of the wire axis in the entire sawing area. The change period is the same as a structural change period of the abrasive area (AA) and the bare wire area (BWA) on the wire surface. In one period, there are two EHD pressure peaks. The size range of free abrasives should be greater than the protruding height of the fixed abrasives on the diamond wire and less than the minimum film thickness in BWA, so that the free abrasives can be constrained in BWA to lap the slice surface. [ABSTRACT FROM AUTHOR]

There are large brittle fracture pits on the surface of photovoltaic polysilicon wafer cut by diamond wire saw, because of the problems such as poor flow of cutting fluid and difficulty in chip discharge. At the same time, the anti-corrosion amorphous layer on the wafer surface can obviously block the subsequent acid etching and texturing reaction. In order to solve these problems, a new type of diamond abrasives-helix-distribution saw wire is used as the sawing tool to obtain the surface characteristics of photovoltaic polysilicon wafer suitable for acid texturing, then research on wire sawing photovoltaic polysilicon based on controlling subsurface microcrack damage depth control is carried out. The concept of high-quality cutting abrasives (HQCA) is defined, and the cutting process of polycrystalline silicon is numerically calculated based on the established new type diamond wire model, the influence of the process parameters and the structural parameters of the saw wire on the cutting characteristics is analyzed, and the reasonable matching between the process parameters and the saw wire parameters is discussed. The study results show that the number and proportion of HQCA in all abrasive grains involved in sawing can be increased by increasing the workpiece feed speed or reducing the moving speed of saw wire, properly reducing the abrasive concentration on the saw wire surface or increasing the abrasives size, or setting the ratio of axial distance between the abrasive area on wire surface and the bare wire area as 1:1. In this case, the formation of the wafer surface tends to be removed in the way of material microbrittleness, and the subsurface crack depths are in the optimal etching depth range. The number and proportion of HQCA remain basically unchanged when the workpiece feed speed changes in constant proportion to the wire speed, and the screw pitch of the abrasive groups on the surface of the saw wire has little effect on it. [ABSTRACT FROM AUTHOR]