There are many types of industrial robot available today. Although some are fairly specialised most are highly adaptable. The most common, the 6 axis anthropomorphic arm, is widely recognised as the standard robot arm and available in a range of sizes but even then there are significant variations to be aware of. Robots are classified according to a number of features but the main two are reach and payload. The payload is simply how much the robot can carry on the end of the arm, note this includes any gripper or tool. The reach is obviously the area the robot can get to and is measured to the faceplate of the last axis as the tool can vary.
The 100 to 250kg payload 6 axis robot with 2m to 3m reach.
These are the mainstay of the industrial robot industry and are found in almost every car plant in the world, usually in lines of 100 or more. Capable of carrying a heavy, water cooled spot welding gun and positioning it to within 0.1mm they have become strong, fast and exceptionally reliable. ABB, Fanuc, Kuka, Yasakawa, Comau, Kawasaki and Nachi all have models. They are not just used for welding, they are also used for assembly, machine tending, packing and a thousand other applications. Because they are produced in such large numbers these are among some of the best value robots, especially on the burgeoning second hand market.
5 to 20kg welding/ handling robot.
Like their bigger brothers these robots are also used in many other applications but one of their biggest markets is again in automotive. This time MIG welding parts such as doors, chassis members, wishbones etc. Because of this these robots are typically very nimble and have brilliant path following accuracy. Again reliability and speed have been gained over decades of hard use and abuse with many chassis lines running around the clock for many years.
20kg to 100kg capacity “middleweight” 6 axis robot
The medium size industrial robot is rarely used in the automotive industry but is used in many others including die casting, plastics and handling. Because of their combination of useful payload and compact size they are becoming more popular.
Delta or “spider” robots have been around for 20 years now and are high speed pick and place specialists. Used a great deal in food processing they are often equipped with vision systems to allow the robot to pick scattered parts from a high speed conveyor. Most delta robots have a low capacity (sub 5kg) and a small work envelope. However there is now some variation, with lower and higher capacity deltas available from Fanuc.
Collaborative robots are the latest big thing in the robotics industry. These robots are designed to work alongside the human workforce and there are several ways in which this can be done. Lowering the acceleration and power of the arm, laser scanners to detect people, having force feedback to detect collisions and even padding the arm allow the robots to be safer to work around.
The main benefit of Collaborative robots is they do not need the guarding and other safety systems required on a traditional robot. This saves space and cost but is also very valuable in modern production where flexibility is important. Collaborative robots are also usually very easy to reprogram so they can be repurposed within minutes.
Rethink robotics Sawyer robot is a more practical follow up to their Baxter dual arm robot. Designed for machine tending the Rethink approach is slightly different to other robots. Joints are compliant and flexible, the arm is taught through leading it to each position manually. Although this type of teaching has been about for many years, especially for paint robots, it is unusual that this is the prime programming tool.
These beasts are often huge machines with payloads of 1000kg or more although really anything over 250kg would fall into this definition. Kuka’s Titan was the first 1000kg capable robot and many of the manufacturers seek to have the worlds biggest and strongest robot in their line up. Real world applications include transferring automotive bodies from line to line and moving large drums of chemicals.
Palletising robots, or indeed palletizing robots are robots designed specifically for handling work. This usually involves stacking onto shipping pallets- however they are also commonly used for unstacking and transfer from line to line of items. The key feature is that the top arms of the robot forms a parallelogram. This keeps the end of the robot horizontal in all positions and eliminates two axis of movement. This makes the robot cheaper to produce, simpler to program and most importantly reduces weight allowing increased payload and speed. In many palletising applications cycle time is critical and one specialist palletiser robot can be as fast as two “standard” 6 axis machines. In this picture the robots are picking up flat boxes using mechanical grippers. Suction grippers could also be used in an application such as this and would allow the robot to more easily pick up varying sizes of item, but with two disadvantages; suction cups wear over time and cannot hold on as tightly as a mechanical grip, sometimes limiting the acceleration that the robot can use in an application- hence limiting cycle time.