What’s the Difference Between Six-Axis, SCARA, and Cartesian Robots?


Posted on: May 22nd, 2020 by SDC

By Ashley Belliveau

 

WHAT’S THE DIFFERENCE BETWEEN SIX-AXIS, SCARA, AND CARTESIAN ROBOTS?

 

Robotic arms are on the rise, with many manufacturers seeking to automate tasks to increase speed and productivity and improve accuracy. Specifically, six-axis, selective compliance articulated/assembly robot arms (SCARAs), and Cartesian robots are among some of the most commonly used robotic arms in industrial automation. With several types of robotic arms on the market, it’s important to know the capabilities as well as the differences among them in order to select the best robot for your application.

 

What is a Six-Axis Robot?

Yaskawa six-axis robot

Six-axis robots are mounted on a pedestal and offer the most directional movement and control of all three robots. The six axes allow the robot arm to move in the X, Y, and Z planes, as well as position itself using roll, pitch, and yaw movements.

Because of its greater flexibility, six-axis robots are ideal for a wider variety of applications, including, but not limited to, those that require:

  • Welding
  • Palletizing
  • Machine tending

 

What is a SCARA Robot?

Epson SCARA robot.

SCARA robots are often compared to a human arm. Mounted on a pedestal, its circular work envelope is created by four-axis motions: X, Y, and Z planes, with a fourth theta axis at the end of the Z plan to rotate the end-of-arm tooling. This allows for SCARAs to move with greater flexibility on a horizontal plane.

SCARA robots are ideal for applications requiring fast, repeatable, and articulate point-to-point movements, including but not limited to:

 

What is a Cartesian Robot?

Cartesian robot.

Cartesian robots, also known as gantry robots, work from an overhead grid, using motors and linear actuators to position a tool. The work envelope of a Cartesian robot is rectangular, the size of which is determined by the grid. If there is enough overhead space available, the grid can be very large if needed.

Cartesian robots have three directional movements: X, Y, and Z. Its rigidity enables these robots to be very precise, which is why Cartesian robots are ideal for straight-line insertions and many material handling applications.

 

Six-Axis vs. SCARA vs. Cartesian: Choosing the Best Robot

Six-axis, SCARA, and Cartesian robots provide excellent solutions for pick and place, assembly, packing, and more. However, as described above, each type of robot has its unique features and advantages, and choosing the best type of robot affects both the cost and success rate of the design. Here are some considerations when choosing a robot for your application.

 

Load Capacity

Maximum payload (or the weight a robot arm can lift) varies from robot to robot. When comparing robotic arms, it’s important for a robot’s load capacity to exceed the total weight of the payload. Because all the joints on both SCARA and six-axis robots are located at the end of the arm, these robots have limited payload capacity and are better suited for small part assembly. On the other hand, Cartesian robots have a larger payload due to its overhead grid and therefore can provide better accessibility to larger parts.

 

Orientation

Orientation is another factor to consider when choosing between Cartesian, SCARA, and six-axis robots. In this instance, orientation has two meanings:

  • How the robot is mounted
  • How the robot moves parts

Both should align when choosing a robot. For example, a Cartesian robot, which is mounted overhead, may be better suited to an application where only a few movements are needed and there is little room on the ground floor. For more intricate part handling that requires a wider range of motion, a SCARA or six-axis robot, which can rotate parts at various angles and positions, may be more suitable for the application.

 

Speed and distance

The type of robotic arm that’s integrated will impact cycle times, so it’s important that a robot’s speed ratings correlate with your output and productivity goals. As a general rule of thumb, Cartesian robots tend to more commonly used for high-speed material handling and assembly applications compared to SCARA and six-axis robots. Also, because of its overhead grid, Cartesian robots are more ideal for moving parts over longer distances, whereas SCARA and six-axis robots are more limited on a pedestal.

 

Experts in Robotic Integration

At Steven Douglas Corp, we evaluate every new project and integrate the best robotic technology for the application. As robotic integrators for FANUC, Epson, Yaskawa/Motoman, and many more, our controls engineering team has extensive experience and training to successfully recommend, implement, and program the optimal robot for your part and application. Contact SDC today to discuss your upcoming automation project. In the meantime, check out some of our past projects.

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