The Selective Compliance Articulated Robot Actuator or SCARA is one of the manufacturing robots that is a variation of articulated robotics. The SCARA robot has three vertical axes of rotation, while the standard articulated robotic has only one. The success of SCARA robots can be directly attributed to its method of working. The SCARA robot performs work on a flat surface and it tolerates and adjusts to some inaccuracies in its work, making it one of the excellent manufacturing robots. These inaccuracies can be handled by the SCARA robot quite easily. For example if a non-SCARA robot tried to insert a peg into a hole and the hole was not in the position that was expected, the robot could not accurately account for the misplacement. Thus it would not be able to complete the work. If a SCARA robot tried to insert the peg into the same hole that was out of place, the robot could adjust to the new hole position and complete the insertion operation.
The articulated robotic, which has a high degree of utility, has 6 degrees of freedom. These are
- a waist,
- a shoulder,
- an elbow,
- a wrist that has the ability to roll,
- a wrist that has the ability to pitch, and
- a wrist that has the ability to yaw.
Even with all these abilities the articulated robotic has its limitations. The SCARA robot has only three of the degrees of freedom of other articulated robotics: a waist, a shoulder, and an elbow. To this is added a fourth linear degree of freedom. It is this last capability, which is called a Z axis, that adds a vertical ability to the other three rotational abilities. The SCARA robotic has the ability to move vertically. This is a capability that the non-SCARA robotic does not have, it gives the SCARA robot the ability to raise and lower the end effector where the work is done.
After a 40 year history the SCARA robot is still very useful as one of the manufacturing robots. This device is still the champ for moving payloads from point A to point B with tasks like dispensing, pick and place operations, assembling products, and loading products on pallets. Being able to carry heavier payloads, having better working relations with other work stations on the line, and an increase in the abilities and variety of end effectors has caused an upsurge in the deployment of SCARA robots. Articulated robotics have taken some of the work that was previously done by SCARA robotics because of the speed and lower implementation cost of the articulated. There are some jobs that SCARA robotics do that no other robots can do, so among the manufacturing robots they have a bright future ahead.
New improvements will keep the SCARA in demand. Installation of the newer version is easier now because of reduced footprint and less cabling requirements than other manufacturing robots. Several models have reduced wiring over what was required in earlier models, while increasing scalability and flexibility. These models have easy, safe operation that will produce up to 1600 mm per second. The new SCARA models are perfect for high speed assembly and packaging for electronics, automotive, and food industries. They are also employed in a wide variety of other applications including, but not limited to, pace maker assembly, DNA testing, chainsaw assembly, electric toothbrush assembly, and computer hard drive assembly. There are thousands of applications that the SCARA robotics can do, with little ramp up. These devices are built to reduce cycle times and maximize the work envelope usage, there is no dead space in the envelope like with earlier models. The best of the automation equipment will now support conveyor tracking, vision guidance, and general machine control. Payload capacities are going up as well to the 20 kilogram level, while increasing the inertia to a very fast pace. Having that increase in strength is not always the best thing, some applications require very finite control to be able to handle the smallest most delicate objects. New SCARA robotics can do this.
While the abilities of SCARA robotics have gone up, the ease of installation and use of the tools has gone up as well. Models are now available that require no programming experience to get them up and running. The integration features have expanded also. The machines are coming with Ethernet capabilities ready to go, pallet loading abilities built-in, and vision abilities on-board. Units can be mounted almost anywhere, floor, table, wall, or ceiling, whatever is best for the application. Factory floor space is economized and production speed is moving fast with very flexible machines. The main drawback of this device is the cost of the software which requires inverse kinematics for linear interpolated moves. A minor drawback is the amount of overhead space that some models might require. The SCARA robotic has come a long way and will continue to fill the needs of automation for years to come.
