3D printing system for preparing a three-dimensional object with an autoclave

A three-dimensional printing system for preparing a three-dimensional object made at least partially of an expanded polymer comprising:

• an autoclave;
• and a printer configured to prepare an expanding or expanded polymer melt and deposit a strand of the expanding or expanded polymer onto a surface;
• the printer comprising a feed section, a cooling section, a heating section, a tubular section configured to prevent the expanded or expanding polymer from flowing upstream into the feed section or the cooling section, the feed section, the cooling section, the tubular section, the heating section and the terminal printing head section being arranged in this order from an upstream end to a downstream end of the printer, and
• a terminal printing head section including a die configured to deposit the expandable, expanding or expanded polymer strand onto the surface,
• the tubular section located downstream of the cooling section and comprising at least one O-ring that reduces an inner diameter of the tubular section such that the inner diameter of at least a part of a length of the tubular section is smaller than an inner diameter of the cooling section located upstream of the tubular section and is smaller than an inner diameter of the heating section.