Method of moulding and mould tool

A mould tool comprising:

• a first tool part defining a first mould cavity portion;
• a second tool part defining a second mould cavity portion, wherein at least one of the first and second tool parts is moveable towards and away from the other of the first and second tool parts in a mould closure direction such that the first and second mould cavity portions cooperate to define a mould cavity for moulding a workpiece;
• and,
• a cavity alignment system comprising:
• a temperature control system configured to control the temperature of a first zone of the first tool part to thereby effect thermal expansion and/or contraction in the first zone of the first tool part in a direction normal to the mould closure direction;
• a sensor configured to measure movement of a part of the first tool part in response to the said thermal expansion and/or contraction in the first zone of the first tool part;
• and,
• a controller configured to control the temperature control system in response to feedback from the sensor to thereby control the position of the first mould cavity portion relative to the second mould cavity portion in a direction normal to the mould closure direction.