Difference between SCARA, Six-Axis and Cartesian Robots

Both high-volume manufacturing lines and small-scale operations use robots to automate their activities. What type of robots to use and when depends on many factors. Because of several benefits that robots offer, their use is increasing not only on manufacturing lines with high volumes, but for executing tasks in many smaller-scale tasks as well.

Implementing robots is becoming simpler. Use of all types of robots is on the rise, including SCARA or Selective-Compliance-Articulated Robot Arms, six-axis and Cartesian types. Robots automate several tasks by accelerating cycle times and increase throughput by eliminating bottlenecks. Not only this, advanced controls are making robots more user-friendly and their backend programming requirements are declining. In several cases, online tools let OEMs and end users select and configure robot features quickly.

For example, packaging of products requires a robot that can pick boxes off a high-speed conveyor and place them on a pallet. This requires a cantilever action as the picker has to extend a full meter for grabbing the boxes and moving them down to the floor and on to a pallet. This application is best suited to a Cartesian robot, and it is also the most cost-effective.

Many creative and new applications are increasingly using robots of all types. However, use of Cartesian robots is specifically proliferating because of standardized components such as modules and linear servomotors along with operator-friendly controls that lower their costs and boost their performance. Cartesian robots are also called gantry robots. These are mechatronic devices using motors and linear actuators for positioning a tool. Their movement is linear in the three axes, X, Y and Z.

In contrast to the Cartesian robots, six-axis and SCARA robots are typically mounted on a pedestal. Similar to the Cartesians, SCARAs also move in the X, Y, and Z-axes and planes, but they have a theta-axis at the end of the Z-plane for rotating the end-of-arm tooling. Vertical assembly operations usually benefit from such SCARA robots, for example, when inserting pins into holes, as the SCARA robots can do this without binding. However, the reach of a SCARA robot is limited, since the joints are load points and need robust bearings with high-torque motors for handling loads when the arm extends.

One can think of six-axis robots as Cartesian robots consisting of a basic system building block but customized for specific activities. For example, pick and place activities become simpler because six-axis robots can move up and down, forward and back, and can yaw, pitch and roll for offering more directional control as compared to SCARAs.

SCARA robots are better suitable for jobs that require precision. They have predefined ratings of accuracy that makes it easy to define their repeatability of movement. However, that also means these robots lock their owners into one level of accuracy at the time of purchase, which makes SCARA and similar six-axis robots rather expensive.

SCARA and similar six-axis robots may also come equipped with defined motion and speed specifications that allow them to deliver better performance right out of the box. However, they may cost more since they usually have proprietary controllers for executing complicated tasks and require more programming for making complex movements