Methods & tools: the rich picture: a tool for reasoning about work context

A monocrystalline silicon ingot is grown from molten silicon by progressively lifting a monocrystalline seed from the molten silicon, which is disposed within a crucible in a furnace, through mounting the seed on a graphite pull shaft. The pull shaft is surrounded by a bellows, which is connected to a carriage to which the pull shaft also is connected. A seal, which is carried by the bellows structure, seals the pull shaft in its rotary motion. Because the bellows structure and the pull shaft are both connected to the carriage, there is no relative linear motion therebetween so that there is no necessity to seal for linear motion of the pull shaft. A pair of lifting mechanisms is connected to diametrically opposite sides of the carriage to support the carriage and to exert a lifting force on the pull shaft along its longitudinal axis. The crucible also must be raised as the level of the molten silicon is depleted due to the formation of the ingot on the seed at the end of the pull shaft. This is because there is an optimum heating zone, which is an isothermal zone and is relatively small, within the furnace, and it is necessary for the level of the molten silicon to be maintained within this zone. The crucible is lifted through being connected to a carriage, which is supported and lifted by a similar arrangement to that for lifting the carriage to which the pull shaft is connected.