The SCARA acronym stands for Selective Compliant Assembly Robot Arm or Selective Compliant Articulated Robot Arm.

In 1981, Sankyo Seiki, Pentel

Pentel

is a privately held Japanese company that produces stationery products. Pentel is also the inventor of non-permanent marker technology. Most Pentel products are manufactured in Japan, Taiwan and France. Yukio Horie, who was the President of the company until his death in 2010, had invented the...

 and NEC

NEC

, a Japanese multinational IT company, has its headquarters in Minato, Tokyo, Japan. NEC, part of the Sumitomo Group, provides information technology and network solutions to business enterprises, communications services providers and government....

 presented a completely new concept for assembly robots. The robot was developed under the guidance of Hiroshi Makino, a professor at the University of Yamanashi

University of Yamanashi

The is a university that has campuses in Kofu and Tamaho, Japan. It was founded in 1949 by a merger between Yamanashi University and Yamanashi Medical University...

. The robot was called Selective Compliance Assembly Robot Arm, SCARA. Its arm was rigid in the Z-axis and pliable in the XY-axes, which allowed it to adapt to holes in the XY-axes.

By virtue of the SCARA's parallel-axis joint layout, the arm is slightly compliant in the X-Y direction but rigid in the ‘Z’ direction, hence the term: Selective Compliant. This is advantageous for many types of assembly operations, i.e., inserting a round pin in a round hole without binding.

The second attribute of the SCARA is the jointed two-link arm layout similar to our human arms, hence the often-used term, Articulated. This feature allows the arm to extend into confined areas and then retract or “fold up” out of the way. This is advantageous for transferring parts from one cell to another or for loading/ unloading process stations that are enclosed.

SCARA's are generally faster and cleaner than comparable Cartesian systems. Their single pedestal mount requires a small footprint and provides an easy, unhindered form of mounting. On the other hand, SCARA's can be more expensive than comparable Cartesian systems and the controlling software requires inverse kinematics

Inverse kinematics

Inverse kinematics is a subdomain of kinematics, which is of particular interest in robotics and computer animation. In contrast to forward kinematics, which calculates the position of a body after a series of motions, inverse kinematics calculates the motions necessary to achieve a desired...

 for linear interpolated moves. This software typically comes with the SCARA though and is usually transparent to the end-user.

External links

• Why SCARA? A Case Study – A Comparison between 3-axis r-theta robot vs. 4-axis SCARA robot by Innovative Robotics, a division of Ocean Bay and Lake Company