What is a Parallel Kinematics Machine (PKM)?

Updated: 2008/9/30

 

Articulate Arm Robots

      The first electrical robots was developed in the beginning of 1970 as a technology that should replace human workers in fields of hard monotone and hazardous work like spot welding, arc welding and handling etc. The target was to build a robot with a large work envelope and a great flexibility without any requirement of high accuracy and stability which wasn"t required for the applications in question. To achieve these goals the technology used is a so called serial linkage technology meaning that every additional axis is mounted on the previous one, see picture to the right. This technology has the advantage of being able to move the mechanics in all directions giving the required flexibility and envelope however without accuracy and stiffness.

                                              

Traditional Machine Tools

      It is well known in the industry that all CNC Machine Tools has a very high requirement of accuracy and stiffness to be able to manufacture parts for an industry that requires microns of accuracy in combination with a high chip removal capacity. However, what people normally do not realize is that all traditional Machine Tools on the market are also based on a serial linkage technology, like the robots, with all the disadvantages in the areas of accuracy and stiffness that comes with it. So, to compensate for this “bad” technology the Machine Tool manufacturers have to design the machines with massive structures and wide beds to make sure that the serial linkage system maintain the accuracy and stiffness also in the end of the last linkage. However, these massive structures and wide beds totally eliminate the flexibility that is significant for robots.                      

                                      

Parallel Kinematics Machines

      The dream of all developers in Machine Tools have always been to combine the flexibility and envelope of the robots with the accuracy and stiffness of traditional Machine Tools. In the last 20 years the focus of this development has been Parallel Kinematics Machines so called PKM. This technology means that the motions in X, Y and Z are performed by three or more parallel axis"s that gives an outstanding stiffness and accuracy with a maintained flexibility and envelope, see picture below. The first machine that actually proved this technology was the Tricept, a PKM machine, developed by Karl-Erik Neumann, that in 1994 already performed real work in the industry. In 2004, the Exechon technology was invented that brought the PKM technology to the next level.