A thermoforming apparatus having a mould 108 with an internal vacuum chamber 111 and a quench 110 for cooling a thermoplastic sheet 104 while it remains on the mould. Because the quench cools the sheet, conventional cooling lines are eliminated from the mould. A preferred process of using the thermoforming apparatus includes drawing a heated sheet 104 over the mould 108, creating a partial vacuum in the vacuum chamber 111 of the mould to maintain the sheet on the mould and quenching the sheet on the mould in a quenching tank 113. A preferred process of manufacturing a mould with an interior vacuum chamber includes forming an impression of the mould in a casting media, suspending a vacuum line or vacuum cabinet within the impression and pouring molten material around the vacuum line or vacuum cabinet to form the mould at least partially surrounding the vacuum line or vacuum cabinet. Vacuum holes are drilled through the mould from the mould face to the vacuum chamber.