Electrophotographic additive manufacturing with moving platen and environmental chamber

An electrophotography-based additive manufacturing system for printing a three-dimensional part, the additive manufacturing system comprising:

• a transfer medium configured to receive and transfer imaged layers of a thermoplastic-based powder for a three-dimensional part, and a thermoplastic-based powder for a soluble support from one or more imaging engines;
• a heater configured to heat the imaged layers on the transfer medium to at least a fusion temperature of the thermoplastic-based powder;
• and
• a layer transfusion assembly comprising:
• a movable build platform;
• a movable platen carried on the movable build platform and configured to accept imaged layers from the transfer medium using heat and pressure over time;
• and
• a chamber supported by the build platform, the chamber having one or more walls at least partially surrounding the movable platen and an opening in a top of the chamber, the movable platen movable vertically within the chamber on the movable build platform and the walls movable vertically independent of the movable platen.