Effect of tool oscillation on surface condition and plastic flow of resin in local friction heating

For the purpose of the improvements of the surface condition and plastic flow of resin in local friction heating (LFH) of resin sheet, low-frequency oscillation with a frequency of 8.3 Hz in the tool axis (vertical) direction was applied to a rotating tool. A rod-shaped tool with a flat end was vertically pushed with a rotation rate of 6000 rpm and horizontally fed with a feed rate of 10 mm/min against the sheet in LFH. The sheet was frictionally heated and incrementally deformed by the rotating tool. The LFHed top surface of the sheet was classified into (a) smooth surface (arithmetic mean roughness Ra ≤ approximately 30 μm) in the advancing side (AS) of the tool and (b) rough surface (Ra ≥ approximately 50 μm) in the retreating side (RS) of the tool in LFH with/without tool oscillation. The AS top surface area was expanded by approximately 0.1 in fraction by the tool oscillation, and the surface roughness was approximately 25% lower than that without tool oscillation. On the other hand, the plastic flow of the sheet in the LFHed part was reduced by approximately 7% in the vertical direction. This is due to (a) increase of the plastic flow to the backward of the tool feed direction, (b) reduction in the stirring amount of the sheet by periodical intermittent contact between the tool and resin, and (c) periodical intermittent pushing to the sheet surface in the vertical direction.