Maintaining cobots09 January 2023

Cooperative robots (cobots) can augment job roles and come with minimal maintenance requirements. Who steps in when repairs are needed?

Rob Breedon, operations service manager, ABB Robotics UK & Ireland, says the use of cobots is limited by a perception that they remove jobs. He believes job roles can be augmented by these machines. For example, the company offers a Wizard software solution that enables cobot users to programme more accurate solutions like welding paths or vision inspection paths.

“They can be simply taught in-situ and can be easily adapted to suit production variants. Users who may have done the welding or quality inspection tasks would now take on a new opportunity through training to apply their experience to now programme the cobot to do the mundane task.”

Universal Robots (UR) strategic service director Annelie Dyring-Bro also recognises the same perks with the company’s own cobots. “By automating menial factory tasks, employees will be able to dedicate their time to more stimulating and fulfilling roles. This will lead to increasing demand for technological skills, such as robotics technicians, engineers and programmers.”

Assessing risk

ABB’s cobots – pictured in manufacture above – can operate unguarded following the successful completion of a risk assessment, which is usually carried out by a stakeholder in the product on a case by case basis, depending on the environment, application and product.

The individual needs to understand what process operation will be carried out and under what conditions while also grasping the likelihood of the associated hazards involved and the potential outcome if the worst were to happen. Risk assessments are usually text-based. The hazards can be reassessed and mitigated if there are any changes to the controls, environment or process. The template usually consists of a list of operations versus the risks associated and then the controls put in place.

“Each element has a potential ‘x’ likelihood calculation based on a 1-5 grid, that then gives you your risk rating from low to extreme,” Breedon continues (table pictured below). “Hazards can be being struck by a cobot – though low impact through design, it should be considered in a risk review.”

For example, a cobot moving quickly in an empty locked room with a sharp object as an application would present a high probability of the hazardous situation occurring (P), but the impact (I) would be low due to the controlled environment (5P x 1I – Risk rating of 5). If this scenario played out in an open room full of people, P would be the same due to the speed and application, but I is higher (5P x 5I).

Turning away from the operational risks, cobots come with simplistic maintenance requirements, according to Breedon. “The gearboxes in most cases use harmonic grease for extended service intervals and most of the components on a cobot arm can be exchanged lineside with limited down time. Motor changes are plug-and-play, with four bolts into a dry gearbox coupling to prevent grease or oil contamination or spillage. This exchange in relation to a larger wet-coupled motor significantly reduces downtime and quantity of tools.”

Hardware and software

For software updates, ABB’s RobotStudio tool allows the user to alter or add programmes. Once created, a back-up of the virtual system can be created and loaded into the customer’s production system. “If both systems are identical, this removes the requirement for manual programming and downtime of the machine.”

Dyring-Bro explains that UR provides hardware maintenance based on manuals that offer recommendations on inspections. This allows the customer to plan maintenance and ensure the cobot works optimally. Users can also download minor and major software releases from the support website free of charge.

Part of UR’s maintenance process includes a visual inspection which can either be carried out by the UR partner or the customer to check for wear and damage on the cobot arm and cables.

“It also depends on the application that you are using and how many hours the cobot is running,” Dyring-Bro continues. “Many times, the customer has a maintenance plan itself and most of them involve looking at the cobot at the same time.”

ABB can also conduct a post-installation check to ensure the cobots are installed within the specification. In addition, carrying out this process throughout the machine’s life enables it to identify if there are any discrepancies from normal performance.

“Estimated failures are predicted against a global baseline. Predicted failures are usually estimated from the utilisation, environment, application, and duty of the mechanical unit,” adds Breedon. “This is then correlated against a mechanical unit’s technical specification to component level.”

Being remote

However, not all support requires the intervention of an engineer. ABB offers a cobot range and technical support that customers can access through phone, email or virtual assistance via a video call.

Also, UR provides training for the customer to learn basic programming skills. As part of the service, UR provides service manuals and other technical documentation to support the usage of the cobot. The user also has access to support and service from UR and its four UK distributors, as well as certified system integrators to help the cobot to stay operational.

BOX: Going spare

ABB says that the company only uses and recommends OEM spares and consumables throughout the lifecycle of the product. Once a product becomes obsolete, ABB initiates a remanufacture process, so spare products can be used again. This process allows the customer to supply its cobot for full remanufacture.

“Remanufacture can only be supplied by the OEM, with this service being conducted in our specialist facility in the Czech Republic, where we return the product to its original specification and performance,” says Breedon. “This involves a complete component strip-down, wear-and-tear replacement and recalibration and test.”

Ben Spencer

Related Companies
ABB Robotics Ltd
Universal Robots (UK) Ltd

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