What process is used to create smooth, even surfaces on materials through pressure and heat?

Calendering is the process used to create smooth, even surfaces on materials through pressure and heat. This technique typically involves passing a material, often in the form of sheets or films, between multiple rollers that apply pressure while simultaneously heating the material. This combination of pressure and heat allows the material to be flattened and smoothed out, resulting in a uniform thickness and surface finish.

Calendering is particularly useful in industries that produce rubber and plastic products, as it enhances the properties of the materials while achieving the desired surface quality. The smoothness achieved through this process is essential for ensuring the materials can perform their intended functions efficiently, such as in the production of tires, linoleum, or other flexible materials.

The other processes listed do not primarily focus on creating smooth surfaces through heat and pressure. Machining, for instance, involves cutting away material to achieve desired shapes and surface finishes, but it does not utilize rolling or pressing. Welding is a joining process that typically involves melting and fusing materials together and does not emphasize surface smoothness. Forging is primarily used to shape metal through compressive forces but also does not specifically target surface finish in the same way that calendering does.