| In order to adapt to the small batch and diversification of market demand,this paper systematically studied the feasibility of forming polyvinyl chloride(PVC)sheet using single point incremental forming(SPIF)technology,for the flexible manufacturing technology of thermoplastic polymer.Lubricants was optimized for selection.UMT was used to measure the friction coefficient.The lubricating effect of liquid soap,40 th oil,PTFE grease,lithium base grease and water of five different lubricants was compared with the maximum forming depth of the variable angle conical cup.The results show that the influence of the five lubricants on the formability of formed parts is from large to small: liquid soap,40 th oil,PTFE grease,water,lithium base grease.When water is used as lubricant,friction coefficient increases from small,basement is exposed,chips seriously,the surface is rough.When oil,PTFE grease and lithium base grease is respectively used as lubricant,the workpiece surface has a slight scar.So liquid soap is the most suitable lubricant for its best formability and surface quality.The effects of five process parameters and their interactions on the formability of PVC sheet,such as sheet thickness,feed rate,spindle speed,Z-axis feed rate and tool head diameter,were investigated by using orthogonal experiment,and the maximum forming angle was taken as experimental indicators.The results show that the effect of feed rate and spindle speed × tool head diameter on the forming properties of PVC sheet is very significant.The feed rate is smaller,sheet formability is relatively good;Z-axis feed rate is larger,the better the formability is;the spindle speed is too high to produce wear phenomenon;the influence of sheet thickness is negligible.The effects of four process parameters on the temperature rise during the forming process of PVC sheet were studied by choosing different feed rate,spindle speed,Z-axis feed rate and tool head diameter.The results show that the feed rate decreases,the time of contact between the tool head and the sheet increases,the temperature increases;the spindle speed increases,the heat generated by the friction increases,thetemperature increases;Z-axis feed rate and tool head diameter increase;The contact area between the tool head and the sheet increases,the heat generated by friction increases,the temperature rise.This paper was to study the forming precision of 50 o pyramids with different feed rate.Geomagic software was used to compare the measured parts of the outer surface of the fitting surface with the theory of outer contour;The radial deviation of pyramids was measured and calculated.The results show that the feed rate increases,the height deviation increases and the forming accuracy decreases.There are three main problems with the formed workpiece: the sidewall bulging due to uneven distribution of stress along the thickness direction inside the workpiece;the accumulation of residual stress leads to the spring back;and the distortion is associated with the tangential force.However,the use of alternate tool path can eliminate distortions.In order to study the influence of process parameters on the microstructure of PVC after forming,the deformation zone of 50 o pyramids was observed by S-3500 N scanning electron microscope,and three phenomena are discovered: the compatibility of the connection phase is improved;the dispersed phase is stretched to form voids;there is stress whitening at the edge of the hole,and there are many crazing around it.With the decrease of feeding speed,the increase of spindle speed,the increase of tool head diameter and the increase of Z-axis feed rate amount to 1.0mm,the compatibility of connecting phase can be better improved;the void is more and more bigger;the stress whitening near the hole is reduced. |
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