Cobot Considerations for Safety and Functionality

Collaborative robots, also known as “cobots,” feature sensor technology designed to enable humans to safely work alongside them in a common work zone without risk of injury. Cobots are used in myriad industries to facilitate all sorts of automated processes. The most common cobot application for machine shops is tending a machine tool, but I’ve seen shops also use them to automate inspection, assembly and so on.

That said, numerous factors come into play in terms of establishing a safe collaborative work environment. Here are three considerations for shops that are eyeing this type of automated technology for their shop floors.

Consider the Gripper

For general purposes, cobot grippers can be divided into four main types, each distinguished by the methods used to power and/or control the gripper itself. Per Universal Robots, these include:

Pneumatic grippers. This gripper technology uses compressed air and pistons to operate its “jaws” or “fingers.” Most commonly found in two- and three-finger configurations, pneumatic grippers are versatile tools that can be used in a wide range of applications.

Hydraulic grippers. Powered by hydraulic fluids, hydraulic grippers provide more gripping power than their pneumatic counterparts, making them well suited for heavy duty applications. However, with that power comes some disadvantages, including the added complexity of a pump, reservoir and oil handling. Consequently, hydraulic grippers tend to require more maintenance than other gripper types.

Electric grippers. These grippers are a popular choice for many cobot applications, including machine tending. While they don’t offer the same level of gripping power as hydraulic grippers, they are suitable for applications that require high speed and light/moderate gripping force. Electric grippers usually come in two-jaw and three-jaw configurations, with three-jaw grippers often being chosen when cylindrical objects need to be handled.

Vacuum grippers. While a machine shop likely wouldn’t use vacuum grippers for machine tending, they could be used for manipulating cardboard in a packaging cell.

These grippers use the difference between atmospheric pressure and a vacuum to lift, hold and move objects. Typically, the vacuum (or “vacuum flow”) is generated by a miniature electromechanical pump or a compressed air-driven pump. The vacuum flow must be uninterrupted to ensure that the cobot can safely hold the object it has picked up.

Compressed air-type grippers produce between four and 10 times more power than their electromechanical counterparts, which makes them a good fit for lifting heavy weights. However, electromechanical-driven vacuum grippers shine in applications requiring a high degree of mobility.

Advantages of vacuum grippers include the ability to handle many different types of items (even when those items are imperfectly positioned) and a lower price compared to other types of grippers. Disadvantages include added electricity costs to power compressed air or vacuum pumps and sensitivity to dusty conditions.

Important questions to ask when selecting a gripper for a cobot include:

• Will the gripper be handling a single item or a mix?
• What types of items will be handled?
• What shape are the items that the gripper must handle (flat, curved, irregular and so on)?
• Is it necessary for the gripper to provide data feedback?
• What payload capacity will the gripper need?
• Will the gripper need to operate in tight spaces?

Consider an Integrator

Some shops choose to use an integrator (a company that comes on location to integrate the cobot onto a machine shop floor), while others choose to do the integration themselves. The choice generally depends on the robot/cobot expertise of the shop and its comfort level with installing a cobot on its own.

Robot integrators have a lot of experience working with different cobot brands, and they are familiar with the different interfaces and installation. For first-time cobot users, a shop might feel more confident using an integrator. However, machine shops and their engineers can be more critical to the integration process than an integrator because they know their machines and automation needs best.

A past Modern Machine Shop article by Senior Editor Julia Hider titled “Avoiding a Failed Automation Integration” notes that whether or not a shop will need an integrator also depends on the complexity of the application. Complexity increases when shops want to automate multiple machines or add peripheral equipment such as conveyors.

But how complex is too complex for a DIY application? In the article, John Tuohy, a former account manager for FANUC America, suggests a simple rule of thumb. The value of a robot integrator shines when shops have questions such as “Can I add vision? Can I add force sensing? Can I pick from this conveyor? Can I put this robot here? Can I tend more than one machine?”

Even easy-to-program cobots might require integrators if the application is complex, he says. Integrators can also help with:

• The connection between the machine tool and automation system. For applications that don’t use a cobot, which is designed for easy setup, an integrator can handle the connection between the machine tool and the robot. Connection varies by machine tool brand. “Sometimes the connection is very difficult to make on your own,” Tuohy says.
• Fixing failed integrations. Integrators will stand behind their work so that if a problem does occur down the road, shops have an expert to lean on. (Integrators can also help shops fix failed DIY integrations, which Tuohy says is a not-uncommon problem.)
• Grippers and other peripheral equipment. Successful integrators understand not only robotics but also all of the processes that surround them, including end-of-arm tooling, workholding, fixtures, machine tools and accessories such as cameras and force sensors. These devices add complexity and introduce potential problems. “Every extra mechanical device can be a point of failure,” Tuohy points out. Integrators can help shops avoid the issues associated with these accessories.

Consider a Risk Assessment

Actually, don’t consider it: Do it.

Cobots need a risk assessment just as their traditional industrial robot counterparts do. In fact, Universal Robots says its cobots have 17 levels of safety protocol, which are adjusted to each individual shop’s unique safety requirements.

Installation adjustments per a risk assessment are said to be much easier with cobots than with robots. For example, the company says that, in the past, a shop would have a risk assessment for a traditional industrial robot and might then have to possibly increase the size of the safety fence or make other costly changes.

With a cobot, it might just be a matter of changing the force, speed or other variables within seconds to fit the risk assessment. So, from an ease of integration standpoint, shops can make changes, software-wise, that turns into hardware and be ready to go within hours.

For an inexperienced shop that has not done a risk assessment for automation, Joe Campbell, former senior manager, strategic marketing and application development at Universal Robots, recommends visiting the Robotics Industry Association (RIA) website, robotics.org, to take the fundamental training on robot safety and risk assessment it offers prior to beginning the risk assessment process.

“The RIA has cost-effective training packages,” Campbell says. “However, if you do not have anybody on your team who has time to do this, then maybe you should go outside the company. The RIA has a collection of skilled consultants who will visit a company to help.” He recommends possibly hiring a consultant for the first cobot integration, and then after the first experience, a shop is likely to understand the process and will not need to hire a consultant the next time.

Technical specification ISO/TS 15066:2016 is another good starting point that helps facilitate cobot integration. The specification offers guidance to conduct more sophisticated preliminary risk assessments of both the cobot system and the environment it will share with humans.