Vacuum-formed baths without visible thicker lines - where lines transfer to invisible face when pressurising preform in female tool

摘要

Thermoplastic sheet is vacuum formed into a deep moulding under low pressure so as to remove thicker lines from its external face. The sheet is gripped, heated, and placed on a male tool, the space beneath is evacuated, so stretching the sheet and producing thicker lines/marks on its outside face. A second/female tool is applied to meet it at the edges, the space above the sheet is then evacuated or, alternatively, the space beneath is pressurised so as to draw the sheet into the female; in the last stage the thicker lines/marks move from the outside to the inside face. Visible thickness variations eliminated (caused by cooler areas in the mould), suitable for producing e.g. moulded baths.