Warping happens when the extruded plastic cools and contracts. As the print cools down and shrinks slightly it starts to pull in on itself. Eventually the forces become so great that the print bends up from the platform. The best way to prevent this is with a heated build platform. By using a heated platform the plastic is kept just below the point where it goes solid, the so called glass transition temperature, and it therefore stays flat and connected to the platform. Although the heat from the platform is often enough it is also recommended to add a thin layer of glue to the platform to promote adhesion so that during printing the object does not move. Spread a thin layer of glue onto the platform. Then, with a moistened rag or piece of paper, spread the glue out evenly onto the platform. As the bed heats, the water will evaporate and leave a very nice thin and even layer of glue. It is also important to make sure your bed is levelled as perfectly as you can. The plastic must be squished onto the platform so that it bonds properly. Besides preventing the print from coming loose or warping it also makes the bottom layer nice and shiny.
Posted in: 3D Filaments