Though industrial robots have their individual strengths, manufacturers should consider the requirements of their application before deciding which to purchase. The payload, stroke length, precision and flexibility needed will all influence whether a linear or articulated robot is the right choice.
The existing infrastructure should also be a factor, and which type of robot would integrate more effectively. Three of the most popular robot types are Cartesian, six-axis and SCARA robots.
Cartesian robots are a common choice in industrial applications. They operate by moving along three orthogonal axes using the Cartesian Coordinate system.
They are also known as linear robots, as they move in a straight line along a support frame, rather than rotating.
Cartesian robots do not offer as much in terms of flexibility as articulated robots. They are an excellent choice for processes that require strength and reliability, but for applications requiring more degrees of freedom, an articulated robot may be more suitable.
The rectangular work envelope on a Cartesian robot means that more of its footprint is active workspace, with no ‘dead zone’.
This is more circular in a six-axis robot, meaning that there is more dead space, but the larger number of axes allows more range in the types of movement that can be done.
The footprint of a Cartesian robot is well defined and thus can be easily integrated into existing infrastructure. They may require a lot of space to install and run but can be mounted overhead or on walls depending on the size, saving space on the ground floor.
Speed is another important factor to consider — speed impacts cycle times, so the speed capabilities of the robot should fit manufacturer requirements in terms of productivity and output. Cartesian robots are a great choice for processes requiring high speed and fast acceleration over a range of distances.
Another attractive feature of Cartesian robots is the ease of programming, installation, and use. Programmes can be reconfigured in the event of design changes or if a new process is required. Factors such as speed, stroke length and precision can all be easily altered depending on the requirements of the application.
A single controller can also be used to control multiple robots. Though more specific programmes can be designed for higher level processes, basic functions can be programmed even by those without prior experience.
Though industrial robots can offer long-term financial savings, initial cost and ongoing expenditures should also be taken into account.
Cartesian robots are generally lower in cost than articulated robots. They also tend to be reliable, thus incurring lower costs in maintenance and downtime.
The actual application that robots are required for should also be considered. The speed and rapid acceleration of Cartesian robots, along with their precision in positioning make them a great choice for a range of industrial processes including pick-and-place, loading, 3D printing and material handling applications.
They can be fitted with a variety of effectors, brackets and controls to suit individual requirements. In terms of reliability, cost reduction and productivity, they can be highly beneficial to an industrial operation that requires high speed and high precision.
Articulated robots, such as six-axis robots, are typically mounted on a pedestal. Compared to Cartesian robots and four-axis models, such as SCARA robots, they offer a larger range of motion, with additional flexibility in movement and directional control.
Along with moving vertically and horizontally, they can also roll, pitch and yaw — rotating around the X, Y and Z axes, respectively. Thanks to this flexibility, six-axis robots can carry out movements that simulate the actions of a human arm.
When someone refers to a robot arm, they are typically describing a six-axis.
Six-axis models can also operate between different planes and levels, increasing the possible applications these robots can be used for.
For more complex applications requiring sophisticated motion sequences, such as automotive assembly, articulated robots are a more effective choice.
Compared with Cartesian robots, the payload capacity of six-axis robots is more limited, as weight must be carried on an extended arm component rather than a rigid support frame.
This should be considered if applications require the movement of heavy payloads. Six-axis robots are usually mounted on a pedestal, which also limits their reach.
Programming a six-axis robot is more complex than its linear counterparts due to the complexity of movement. They must be designed to work in a three-dimensional space with multiple rotary motions. However, they can also be programmable to adapt to changes in operation and are multi-application capable.
In terms of financial expenditure, six-axis robots do tend to be more costly, but this is justified if the application is more complex.
Though their configuration may limit payload size and distance, the superior directional control and flexibility of six-axis robots allows them to carry out movement that linear robots cannot.
With their increased versatility, six-axis robots can be used for intricate tasks including pick-and-place, assembly, welding, machine tending, palletising, and handling, among many others. They are also suitable for painting, packaging, and material removal.
SCARA (Selective Compliance Articulated Robot Arm) robots have a parallel axis joint layout, making them compliant on the X-Y axis and rigid on the Z axis.
SCARA robots have a smaller footprint, especially in comparison with Cartesian robots, and the pedestal is unobtrusive, making integration into the workspace relatively easy. As with other articulated robots, they have a circular work envelope.
This does result in more ‘dead space’ than with a linear robot, but as they do have four-axis movements within this space they have good flexibility of motion.
SCARA robots’ smaller size may limit their potential applications in comparison to six-axis robots, which are available in a greater size range, but makes them suitable for small-scale processes that require speed and precision. They also have a reduced reach as they are mounted on a fixed pedestal.
As with six-axis robots, the payload capacity on SCARA robots is lower than Cartesians, as its joints are located at the end of the arm.
This results in more unsupported mass, making them more suitable for applications using smaller and more lightweight parts.
They are faster than both Cartesian and six-axis robots due to the rigidity of their design, allowing rapid motions and superior levels of repeatability, making them ideal for highly precise assembly applications
Generally SCARA robots are lower in cost than six-axis robots and have an excellent price to performance ratio in high speed tasks, but are still more costly to implement than Cartesian robots.
They do not have the same level of freedom of movement as a six-axis robot, but are still versatile enough for a diverse range of applications. Processes that could benefit from SCARA robots include high speed pick-and-place, materials handling, packaging, palletising and depalletising, machine loading, and small parts assembly.
Though industrial robots offer a multitude of benefits, it is still important that they are maintained effectively to reduce downtime and lost revenue.
Industrial automation can be complicated, but there are options available for all processes and operations. To fully reap the benefits, considering all aspects of an application is key.
Making the right choice can bring significant increases in productivity and efficiency along with reductions in costs and downtime.