Robots in time with speed requirements

Nick Buckley examines new system technologies enabling synchronised robots to deliver twice the speed in half the time.

Nick Buckley* examines new system technologies enabling synchronised robots to deliver twice the speed in half the time.

EVEN though robotic solutions continue to prove their worth in terms of shorter cycle times, increased throughput, improved quality and higher accuracy, there are times when multiple robots are needed to meet required production times.

Traditionally synchronising robots to work together had not been simple. Robots need to work cooperatively, while at the same time avoiding any collisions that could cause extensive damage which can be extremely costly, both from a repair and a downtime perspective.

Although the welding industry was an early adopter of automation, it remains a process that is undergoing continuous refinement as robotic welding still needs to be engineered differently from a manual system as there are many factors that need to be considered when setting up an automated welding facility.

These requirements include considerations such as accuracy, controls, servicing, repeatability, reliability, area, rotations, fixtures, programming, tracking systems, maintenance, weld monitors, welding process, positioners, loading/unloading and parts transfer.

Automated welding requires the robots to have the manoeuvrability/flexibility within the robot arm (axis) necessary to complete a wide range of motion. This enables the robot arm to approach the work from the correct angle so that the part/s can to be welded correctly.

Welding systems that operate non stop also require appropriate maintenance procedures to be adhered to. Continuous production line interruptions can be avoided or minimised with proper robotic system design. However due to the repetitive nature of the design, recalibration or reprogramming is required as set intervals.

In addition, other considerations must also be evaluated and then allowed for if thought to propose a real risk to production. An example might be a manufacturing line where there are many robots working sequentially — in the case of a welder failing, do you plan for immediate replacement or build into the system the capability that enables the welding to be distributed to other functioning robots?

Robots in action

These considerations were taken into account when MAR was commissioned to design and install a robotic welding system in a manufacturing facility in Melbourne, Victoria. The system was to automate the welding of components to a Hydro-formed metal frame as well as handling of the frame to and from an existing injection molding machine.

MAR has two standardised portable welding cells based on the ABB IRB2400L industrial robot system and the Fronius welding systems. These moveable cells have proved to be extremely popular with clients. The standardised cell design has enabled a much shortened delivery time from order, an easy user friendly setup system as well as been extremely competitively priced. Based on this unit, the estimated time for the one robot to complete the set task was under 90 seconds.

However, after initial discussions, other complexities to the design of the system were brought to light.

The two brackets and six patches had to be presented and welded to the frame within the cell.

The client also had a Fanuc robot that was used for loading and unloading the welded frame into an injection molding machine. This process/robot would have to be integrated with the welding system and to work with the ABB robots.

Then the frame needed to be returned to the original place of entry into the welding cell after the injection molding is completed, which required this time to be halved to meet overall production times. I.e. reduced from sub 90 seconds down to below 45 seconds.

The final solution

The design for the completed process required a combination of technologies to be brought together including safety systems, advanced programming, dual robots, and the integration of disparate systems.

The operator loads the metal frame to be welded onto the jig which is then automatically clamped. The ABB positioner indexes the frame into the cell so it is perfectly aligned, and the brackets and patches are presented and the two ABB robots complete the welding. The Fanuc robot then takes the welded frame for the injection molding process and the Fanuc robot, using its double sided gripper, then returns the molded bar back onto the jig, The jig then returns to point of entry and the frame is unloaded.

The advanced functionality of ABB’s control software enabled the two robots, the positioners and other devices, to work in fully coordinated operation. This is made possible by the processing power of the IRC5 control module computer that makes the path calculations ensuring that at no stage there is any risk of collision while the robots complete their set tasks.

No matter how complex the requirements are, there are many examples in the welding industry of how coordinated robots have been set up. Robots can be programmed to work on parallel assembly lines, returning ‘just-in-time’ to carry out programmed tasks. This type of solution offers total freedom of motion and the optimum working position regardless of the task. This also eliminates the need for extra jigs and manual labour involved in mounting objects, while substantially cutting lead times.

Traditional, sequential robot tasks can also be streamlined. Because every robot motion is synchronised, process flow can be optimised and throughput times reduced. With every robot knowing what the other is doing, risk of collision is also minimised.