How to stop your model warping

Key Points
Keep the bed clean and warm
Level the bed properly
Put your printer in a consistent environment, e.g. no rapid temperature changes.

What is warping
Warping is the result of material shrinking whilst 3D printing. This causes the corners of the print to lift and detach from the build plate.

How does it occur?
Most often, warping appears when a model cools down too quickly while it is still being printed.
Material is heated up to extrude onto the printed bed. When the material is heated it expands and then cools and contracts. If material contracts too much, warping occurs.
Warping is often worse when the parts are made with solid fill and take up a lot of room on the build platform.

Materials most susceptible to warping
PC is more susceptible to warping than PLA
ABS is very susceptible to warping, especially when being used for large models.
Industrial materials such as PC and CPE+ needs an enclosure due to the high printing temperatures required to print them.
PLA is one of the best materials for large prints as it is less susceptible to warping

How to prevent it?
Carefully position your printer. Keep your printer outside the path of direct airflow, such as air-conditioning units or open windows.
Keep the printer doors closed, this makes the printing environment a warm and consistent environment.

Use a heated build plate- this keeps the material at a temperature just below the point where it solidifies. This is known as the, ‘glass transition temperature’. This ensures that the build stays flat and connected to the build plate.
Level the bed, otherwise layers won’t be able to stick to an un-even surface.
Make sure the first layer is firmly attached to the print bed. If the distance between the build plate and the nozzle is to wide, material can become loose easily. If you are having problems getting the first layer right, relevel the bed.
Make sure the bed is smooth and clean. With no oil or grease on it as this will reduce adhesion.
Use a brim this is a single-layer-thick flat area around the model. A brim will resist any upwards pull from corners trying to lift away from the bed.
Use a raft, this is a thick grid between the model and build plate which distributes heat evenly through the model. This is particularly useful when printing something which does not have a flat base.

Adjust initial layer settings, the first layer is the most important to make sure the print sticks to the bed. There are two important printer settings to monitor to do this that influence the initial layer height and initial layer speed. Typically a thicker first layer is more adhesive. As this means that calibrating the build plate is not as critical, but still advisable. It is important to have a slower first layer, this will prevent the head picking up material and dragging it across the build plate. Aim for a first layer with small tight, nearly seamless lines to get a smooth bottom layer.