Recently, there has been a massive surge of interest in what has been coined “collaborative robotics” or “cobots.” The allure of cobots is that they are marketed as being safe, inexpensive and easy to use.
While this is all true on some level, anyone looking to purchase a cobot for use in a manufacturing facility needs to investigate and perform due diligence. In doing so, fabricators and manufacturers can make an educated purchase and avoid being disappointed with a not-so-trivial capital investment.
Safety first
As far as safety goes, there are two standards that focus on requirements and guidelines for the safe use of industrial robots: RIA 15.06 and ISO 10218. These standards separate cobots into four categories. The first category is safety-rated monitored stopage, which requires zero robot motion while the operator is in the collaborative working space of the cobot. Typically, this is where the collaborative space is monitored by a laser scanner or safety mat; while an operator is in the location, the cobot will not move. Fanuc has been using robots in this manner for well over a decade.
The second category is when the cobot is utilizing a type of hand guidance or operated assisted device to solely control the motion of the cobot. The third category is when the speed and space of the cobot is actively monitored and adjusted based on location of the operator within the collaborative working space. The cobot always maintains a fixed safety distance between itself and the operator and when that distance is violated, the cobot stops.
The fourth category of cobots is where power and force are limited by inherent design or control. This simply means the cobot, by design, is limited to a minimal amount of force when contact is made between operator and cobot. Most of the newer cobot manufacturers have concentrated their efforts toward creating cobots that fall into this fourth category.
Addressing safety concerns includes taking into consideration the application in which the new cobot will be used. Applying a cobot in a lab or classroom environment is completely different than using it in a regular factory environment. Some manufacturers envision finding a low-cost robotic solution for their shop floor with little to no safety hardware associated with it that works side by side with operators assisting them with their job tasks day in and day out.
But for manufacturers looking to utilize automation in an interactive environment with humans, it is up to you to ensure operator safety. The only way to completely ensure safety is to perform a complete risk assessment. This means following predefined steps and verifying that every aspect of the cobot and operator interaction is discussed and identified. Then, rating the identified risks and determining if those risks can be eliminated or mitigated.
For example, a cobot that performs a pick-and-place function may seem simple enough, but what if that cobot handles a sharp or hot object or harmful chemicals? While the cobot may move slowly enough to not cause injury if contacting the operator, what if that operator were to contact the tool holding a sharp or hot object? If the cobot is welding, there may be minimal risk from impact of the cobot, but what about the hot weld wire, smoke, bright UV light and electrical risks associated with the process?
You must consider the application when purchasing a cobot. You can’t assume the manufacturer or distributor is going to do it for you.
Cost factors
The next area of consideration for investing in a cobot is cost of ownership. Anyone who has ever purchased a used car will fully understand this premise: The cheapest vehicle on the car lot may look lucrative from the onset, but it will not take long before you incur additional expenses. This is referred to as the cost of ownership, and it applies to almost everything, whether it’s cars, televisions, computers or cobots.
For a cobot, consider how long it is designed to run before you have to invest in parts to maintain it. There is a specific metric referred to as Mean Time Between Failure (MTBF) for industrial equipment. This is a typical measurement for how long a piece of hardware or component will last before it is expected to fail. A reputable robotic OEM should have an MTBF value for its equipment of around 80,000 to 100,000 hours.
After all, you are looking to purchase an “industrial” robot. The last thing you want to do is purchase a solution and then immediately start the planning phase for its replacement in a few years because of an inferior product or lack of replacement parts when something does fail.
If the application requires the cobot to interact with other pieces of hardware, you may need an interface. For instance, if you want a cobot to assist an operator with welding, you will want to understand what options are available to “interface” between the cobot and welding equipment. This interface allows the cobot to communicate with the welder to allow it to control the welding process and other features. Find out what brands and types of welding equipment the cobot can communicate with.
Furthermore, find out what other types of features are available to assist you with your manufacturing process. Do you want a cobot that requires you to have to program each part because your parts vary slightly? Or would you like a cobot that can make the necessary adjustments using software options like touch sensing or seam tracking to ensure the welds are going into the right places every time and not have to reprogram every single part?
You would rather see your cobot doing work instead of seeing your cobot programmer giving it constant attention. It doesn’t help your bottom line if you have a new capital asset and an operator tied up on the same job.
Easy to use
This leads to the final area of consideration, which is ease of use. This term gets thrown around quite a bit, but in this case, you want to understand how much effort it will take to get your new cobot not just up and moving but doing the actual work you bought it to do. Most customers can have their cobot powered up and ready to program in under an hour depending on its size and power requirements.
While important, this is not a significant contributor to your ownership experience. Programming your application for the cobot is where you will invest a majority of your time. And depending on the application, the cobot manufacturer will have software and hardware options to aid in significantly reducing the amount of time required to have the cobot performing its task. If it’s doing a simple pick-and-place operation, it typically does not require anything more than the ability to control a gripper of sorts.
However, if the cobot is welding, there are multiple parts of the process that the cobot needs to control. For example, when placing the weld, if there is any variation in the weld fit-up, you will need to accommodate it with software options that do it automatically or by adjusting your programs manually for each part. If you have any variation in the surface conditions of your weld, you will also need to adjust for those conditions automatically or by adjusting your programs manually. For example, if the part has a heavy layer of mill scale, rust or oil, will the cobot make several attempts to initiate the arc or will it attempt once and then wait for manual intervention?
If your collaborative application is such that it is designed to assist your more skilled operator with a job like welding, you do not want your them to constantly have to stop their work in order attend to a cobot that should be doing its own welding. You want it to have the same ability to adjust to its environment just like your operator and not have to stop every time it encounters adversity.
If the goal is to have limited operator interaction, then a cobot may not be the right solution. A standard robot requires more safety content, but it also provides much more capability. Just like with any other major purchase, you will want to do some research to make sure you are getting the best value for your dollar.
