The work envelope refers to the area surrounding an Industrial robot where it can perform useful work.
What determines it? The robot's range of motion and access. Having a proper understanding of a robot's work envelope helps ensure you choose one suitable for your needs.
The dimensions of a work envelope don’t include the additional reach granted by tools attached to the robot's joints.
Also, unreachable areas outside the work envelope are known as the “dead zone.”
The size and shape of a robot's work envelope depend on a number of factors:
The number and type of joints determine how freely the robot can move.
In manufacturing, Six-Axis articulated arms are popular because their rotary joints enable a large, complex range of motion that even exceeds a human’s.
On the other hand (pun intended), robots move linearly along the x, y, and z axes, limiting their reach but providing very high speeds and precision.
The length of the robot arm and any extensions or end-effectors (think of them as exchangeable robot hands, or gripers) directly impact how much area the robot can cover.
Some robots have fixed arm lengths, while others are modular or telescopic, allowing you to add segments to expand the reach.
The maximum weight a robot can lift and move affects what it can handle within its work envelope.
Heavier payloads typically mean a smaller area of movement to maximize stability and control. Conversely, lighter payloads tend to mean more flexibility and dexterity.
Surroundings also have a huge impact on a robot’s effective work envelope. Obstacles, pinch points, and interference from peripheral equipment can all limit the range of motion.
The ideal environment for most robots is open, clutter-free, and specifically designed with their dimensions and capabilities in mind.
If you’ve been paying attention, then you’ve probably surmised that the work envelope for Industrial robots is a big deal.
Choosing a robot with the appropriate work envelope is basically the difference between success and a possible task/robot or environment/robot incompatibility.
Here are the main types of Industrial robot and their work envelopes:
Cartesian or Gantry robots have a large work envelope but a much more limited range of motion.
These robots move along a fixed grid of X, Y, and Z axes. making them a good fit for pick and place or material handling over a wide area. However, their bulky nature restricts their ability to perform tasks requiring complex movements or angular orientations.
Some systems can cover areas as large as 20 meters by 3 meters by 1.5 meters, and their payloads range from a few kg. to several hundred.
On the other hand, SCARA robots have a cylindrical work envelope and 4 axes of motion. Their arms rotate horizontally and vertically but cannot reach behind themselves (they can’t scratch their own back, in other words). SCARAs are excellent at assembly and packaging.
SCARA Industrial robots typically have a work envelope of 400mm to 1000mm and lighter payload capacities of up to 20 kg.
Six-Axis or Articulated Arm robots (or 6DOF, “Six Degrees of Freedom” robots) offer the most complex work envelope because they’re able to rotate in all directions.
Their human-like (and above) range of motion makes them versatile and suitable for welding, painting, Pick and Place, and machine tending.
They typically have a reach ranging from 650mm to 3,000mm. Their payload capacity can vary widely, from a few kilograms to over 1,000 kilograms for larger models.
Your robot’s work envelope is not set in stone, and if you want to get the most out of it, you need to learn about a few strategies and tools.
Here are a few ways to expand a robot’s range of motion and access more areas for automation:
How and where you position the robot can have a big impact on its work envelope.
Mounting the robot overhead, on a rail system, or even upside down can provide access to areas that wouldn’t otherwise be reachable. Overhead mounting, in particular, uses the robot’s full range of vertical motion.
Additionally, rail-mounted robots can travel along a guided track to extend their horizontal range. Some robots are designed to operate upside down (now, that’s a sight!), with inverted joints and motors.
This is not just cool-looking: inverting the robot provides access to the undersides of parts, machinery, or conveyors.
Attachable tools and end-effectors are available to physically extend the robot’s reach. Extension arms, also called robot risers, are lengths of rigid material that attach to the robot arm to lengthen its reach.
Vacuum grippers and other end-effectors are also available to attach to the end of the extension arm, so the robot can lift and manipulate parts from a distance.
Some robots can be fitted with extra joints to increase their degrees of freedom and maneuverability.
You can install: wrist units, elbow units, and shoulder units to provide extra pivot points and a more human-like range of motion. With additional joints and extension tools, a standard Six-Axis robot can gain access to nearly any point in its work cell.
Understanding the work envelope of Industrial robots is synonymous with understanding a robot's capabilities and limitations.
This can be essential when selecting the right robot for your application. While some robots offer expansive work envelopes, others are more compact but highly flexible.
But, the good news is, for many robots, the work envelope can be extended depending on your needs – and your existing setup.
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