Cartesian 3D Printer - the printer head moves along the XYZ axis and the base plate moves up and down. It is very versatile and can print various objects, from key chains, action figures to household tools such as screws, mugs and vase. It is also used in bio-engineering/medical engineering to print organs with stem cells. 

Delta 3D Printer - moves the printer head in all directions while the base plate stays static. The advantage of Delta 3D Printer is that it is not hampered by the inertia of the gantry such as the case with the Cartesian 3D Printing. Therefore, it can be said to print more detailed objects with more accuracy. It can print stamps, dolls, model trains and planes. 

Polar 3D Printer - it consists of an extruder that moves up and down while the base plate rotates. It can be used to print nuts, bolts, hardware, toy parts or sculptures.

Robotic Arms 3D Printing - Robotic arms are used to assemble parts in production lines. It has been used in the construction, aviation, automotive and manufacturing industries for decades now.