The debate about whether to automate plastics manufacturing plants is over, and automation won. The factories of today have robots almost everywhere to plug labour gaps, boost productivity and throughput, and improve production quality.
So with that debate over, the industry is already on to the next one: choosing the right type of automation for a particular job. A big part of this new discussion has traditional industrial robots on the one side, and a new type of mechanized helper on the other: collaborative robots, nicknamed cobots. While both can increase efficiency, productivity, and safety in a plastics plant, their distinct characteristics and applications make them suited for different scenarios. Cobots are designed to be mechanized teammates, working safely alongside humans in a shared workspace. Robots, on the other hand, take on those tasks that are repetitive, hazardous or require exceptional precision and/or high speeds, often working independently of human intervention.
Making well-informed decisions about which automation type best fits your specific needs and circumstances is one of the most important a processor will make. And the evidence suggests they don’t always choose wisely.
“A lot of plastics molders don’t seem to know exactly where cobots fit in the manufacturing space, and this leads them to take the wrong approach: buying a cobot and then trying to figure out on their own where to use it,” said A.J. Zambanini, director of sales and marketing for Canada and the U.S. with Sepro North America.
The right approach is to understand robots and cobots distinct characteristics, the OEMs and vendors say, and the differences – including strengths and weaknesses – between them in key areas such as integration, ease of use, cost, and how they fit into a work environment.
COMPARE AND CONTRAST
The primary difference between industrial robots and cobots is human involvement – the former are designed to replace human employees and must operate in a separate workspace, while the latter assist workers and can safely complete tasks alongside them. Traditional robots are typically larger, heavier, more powerful, have a greater range of motion, and – crucially – can handle heavy payloads. The specific payload capacity depends on the robot type – either SCARA, articulated, or Cartesian – and on the weight their wrists can support, but heavy-duty models are capable of lifting over 1,000 kilograms (kg). Which is why they remain the kings of industrial automation. “Cartesian robots, in particular, are still very well-suited for most injection molding applications and are preferred to other industrial robots due to their speed and overall footprint,” said Jason Long, vice president of sales with Wittmann USA.
Cobots, in contrast, have lower payload capabilities due to their design for safe human interaction and typically handle payloads of five kg or less – although some models are being beefed up in this regard. Fanuc’s CRX-25iA cobot offers a 30 kg payload capacity with full wrist articulation, for example, and its CR-35iB cobot has a 50 kg payload capacity. But questions remain. “Even with a cobot that can lift 20 kg or more, the question is, can it do it 24/7/365?” said John McCormick, president of Proco Machinery and its new stand-alone sister company Cobots Inc., which McCormick founded earlier this year to design and supply cobots for a range of industries, including plastics. “The cobot’s tooling has its own weight as well, which adds to the payload and to the mechanical stress,” McCormick continued.
Indeed, payload is a critical dividing line between robots and cobots, some OEMs say. “The equation we follow at Fanuc is, if a customer wants the automation to move anything heavier than 50 kg at a fast speed, that rules out using a cobot,” said Dale Arndt, director of engineering and integration with Fanuc Canada. “Going beyond that payload risks injuring someone when the cobot stops moving, and just dropping a large part could cause injury, so it wouldn’t be safe to share the workspace. For many industrial applications, these small payloads aren’t enough, which dictates using an industrial robot.”
SPEED BUMPS
Another trademark of traditional robots is speed. High-speed plastic automation can achieve impressive production rates, with some systems producing hundreds or even thousands of parts per minute, with cycle times as short as two seconds or even less. And high-speed robots keep getting faster. Wittmann’s Sonic 108, for example, is the latest in its Sonic line of high-speed robots. Optimized for high-speed parts removal in packaging and pick-and-place applications, the Sonic 108 is designed for cycle times below four seconds, with in/out times kept under 0.9 seconds.
Cobots can’t compete in this regard. Because they’re designed to work safely alongside humans, their speed typically ranges between 250 and 1,000 millimeters per second, which is slower than traditional industrial robots operating in safety cages – although cobots can operate at higher speeds when humans aren’t in the workspace, in applications such as opening boxes or stacking fragile items. While industrial robots also have safety features, such as emergency stop buttons and safety-rated monitored inputs, their primary focus is on efficiency and precision rather than direct human interaction. Which means they need controlled environments consisting of costly safety cages and light curtains and other sensors to keep operators protected; and they usually work separately from people. “As long as high-speed robots are behind safety cages with other safety features, and the workers stay clear, then there’s no danger,” said John McCormick. “But if a mistake is made with an industrial robot, you can still smash tooling and break things, which can be dangerous and expensive to repair.”
Cobots, by contrast, can’t do much damage because of their slow speed and low force, coupled with their smooth edges and soft padding to minimize the risk of injury in case of contact. “Even if the operator makes a mistake and crashes the cobot, usually it won’t damage anything,” McCormick said. But even though the safety settings on cobots can be adjusted as necessary depending on the application, a cobot can still be dangerous in certain circumstances. “Customers often assume that cobots never have to be guarded, but that’s not true,” said Tim Lavigne, business unit manager with Absolute Robot. “If the cobot is performing trimming and has a blade at the end of the arm, or a flame/heat element for heat-treating, it can be dangerous if a worker gets too close. And for heat-treating applications, even when the cobot stops moving because a proximity alarm is triggered, there’s still dangerous residual heat. So sometimes fencing is required.” Ironically, cobots actually require stricter safety guidelines since they interact directly with people, which might not be as stringent for traditional robots operating in isolated environments.
Ultimately, it’s critical to perform a risk assessment to ensure that an application is safe and suitable for using a cobot. “Are there pinch points we have to be aware of? Do we need excessive speed? Is the part too heavy? Is there a risk of dropping the part in the machinery being used to make it? All these variables must be considered,” Dale Arndt said. “Some customers worry that a risk assessment is complicated and time-consuming but, in many cases, it only involves a quick review of speed, payload, reach, and where the cobot is working, and it can be done by simulation. You can determine a lot in a very short period of time, and there are skilled integrators who can help with the assessment.”
COSTLY QUESTION
Despite their efficiency, traditional robots also come with high acquisition and installation costs, which may be prohibitive for some companies. Their installation is complex and may require significant modifications to the work environment, some OEMs point out, often needing specialist intervention; as well as specialized expertise for programming and operation, which can result in a steeper learning curve and longer setup times for robots compared to cobots. Also, a robot installation needs to comply with relevant safety regulations and standards; and the robot will have to be integrated with existing manufacturing systems and processes, which can be complex, require careful planning, and might raise cybersecurity concerns given the increasing connectivity of industrial robots.
Cobots, by comparison, are engineered to function autonomously, and are therefore easier to introduce onto the shop floor and can be easily programmed and operated without much training. Some brands are becoming more complex, however, albeit in the name of even easier deployment. Cobot maker Universal Robots recently unveiled its UR AI Accelerator, for example, a hardware and software toolkit said to enable the development of cobot applications powered by artificial intelligence. Company officials said the accelerator provides built-in demonstration programs to enable pose estimation, tracking, object detection, path planning, image classification, quality inspection, state detection, and more.
Unlike robots, cobots are also portable. “Moving an industrial robot from one line to another can be done, but it isn’t common; it’s highly specialized and typically focuses on doing one specific task very well,” A.J. Zambanini said. “Cobots can be moved around easily – especially when they’ve been mounted on casters – because they can adjust to various workspaces for general-purpose use.”
And as far as price, cobots are generally more affordable than traditional industrial robots – and with lower startup costs – but the price can vary based on features, complexity, and application. In any case, they’re not cheap. “Typically, cobots range from $10,000 to $50,000,” said John McCormick. “They were overpriced in the early days, and prices are coming down as more offshore brands become available, but it’s still an investment the customer should take seriously.” There’s no one-size-fits-all answer here: Cobots are a good option if you want flexible automation without breaking your budget, some OEMs say, while traditional robots are often more expensive upfront, but that higher initial cost can be offset by their increased efficiency and productivity. “Generally, robots and cobots have the same integration requirements, but maybe for some applications a cobot might not need true safety guarding,” said Jason Long.
As with any piece of capital equipment, robotic automation systems will develop performance issues if the owner doesn’t follow the OEM’s recommended maintenance schedule, which may vary by robot type and usage. Common maintenance tasks with both robots and cobots generally include daily visual checks, cleaning optics and sensors, ensuring proper airflow, inspecting cables and bolts, and regularly performing grease and gear maintenance. Software updates, sensor recalibration, and testing of braking systems are also important.
“In theory, cobots may require less maintenance than robots because of usage patterns: the tasks aren’t as demanding and they may not be running full-out 24/7,” said Tim Lavigne. “But to ensure best performance, a cobot should be on the same preventive maintenance schedule as an industrial robot.” Cobots also have a unique maintenance need in that the speed decelerations as human workers get too close can eventually affect the unit. “The act of repeatedly slowing down or stopping completely will gradually alter a cobot’s positioning,” Lavigne said. “So over time, you’ll have to examine the point positions and adjust the cobot so that it keeps hitting the mark exactly.”
Due to their often-heavy-duty applications, industrial robots are typically built to be robust and durable, with a long operational life. Depending on regular maintenance, updates, and component replacements, the average lifespan typically ranges from 10 to 20 years. A cobot isn’t designed for the same degree of ruggedness, and its lifespan typically ranges from 30,000 to 40,000 hours of operation, the OEMs say, which translates into roughly four to five years of continuous operation. But some of this is pure speculation at present. “It’s still early days for cobots, and we still don’t know what the lifespan is for some brands,” said John McCormick. “But whether it’s five years or even 10, a cobot can be replaced much more easily than a traditional industrial robot.”
COBOT OR NOT?
With all this in mind, when a processor must choose between traditional industrial robots and cobots, OEMs say, consider a few important things. The first is how they fit into your work environment. “A crucial point with a cobot is to make sure it’s going into an actual collaborative environment,” said A.J. Zambanini. “I’ve seen instances where the cobot is handling something inherently unsafe, like a metal bender – that metal bender is itself a hazard, no matter how slowly the cobot works. So you really have to understand the environment that it’s going to work in.” Furthermore, the OEMs say, if your tasks change often, like packaging different products, cobots can adjust quickly; if your production is repetitive, like assembling identical items, industrial robots are probably better for the job. “I divide it along the line of process simplicity,” said Dale Arndt. “Our robots are being used right across the spectrum, from non-routine tasks to very repetitive tasks, but if the task is simple, a cobot makes sense.”
Another consideration is the requirement of the application. “For repeatable tasks, ideally away from the confinement of a cycle time, cobots are an excellent option,” Tim Lavigne said. “But if you need to keep pace with a cycle time or handle high-precision placement, an industrial robot would be the proper selection.”
The amount of available workspace is another factor, including floorspace, ceiling height, and the layout of existing equipment and workstations. “If you have a smaller workspace with people working nearby, cobots are safer,” said John McCormick. “Industrial robots work best in larger spaces where they don’t need to interact with people and where there’s room for safety infrastructure.”
The skill level at a particular company can also play a role in deciding. “If your team doesn’t have programming experience, cobots can be easier to use,” A.J. Zambanini said. “If your team has technical skills, industrial robots offer more advanced options and benefits.”
Finally, consider your company’s automation endgame, including how your needs may change over time and whether the chosen solution will be able to adapt. If the goal is to improve safety and reduce physical strain on workers, cobots are a good way to go, OEMs say; if you need high-speed production, industrial robots will deliver better results. In industries facing labour shortages, cobots can provide a reliable and efficient solution. And on the principle that a chain is only as strong as its weakest link, cobots can also be a way to reduce a shop’s vulnerability due to unmotivated workers. “The reality is, many shops have a nucleus of dedicated workers who are very reliable, but also a fringe number of lower-paid workers – usually on the night shift – who aren’t always reliable,” John McCormick said. “These are the workers that can be replaced by cobots.”
And sometimes you don’t have to choose. Robots and cobots can be used together in a single application, particularly in scenarios where a human worker needs to be close to the robot. “Typically, a traditional robot will unload the parts from the injection machine and place them on a conveyor, and the cobot will pick up the parts at the end of the conveyor for boxing or other assembly applications,” said Jason Long. At the NPE 2024 trade show in Orlando, Fla., last year, Sepro demonstrated a molding cell where a standard Sepro Cartesian robot handled part extraction and placement and a cobot module from collaboration partner Yasakawa packed the finished parts into totes. “Each did what it was best suited to handle,” said A.J. Zambanini. “The cobot packing unit operated independently, meaning it required no integration or communication with the molding machine or extraction robot.”
In the end, both traditional robots and cobots can enhance a plastic manufacturing plant’s operation. Cobots are tailored to collaborate with human workers, simplifying programming and boosting safety for team-oriented jobs; whereas traditional robots excel in precision and efficiency, and are ideal for repetitive or hazardous tasks that require minimal human interaction. Understanding which type of automated helper to use can boost your productivity and ensure a safer, more innovative workplace. This knowledge is the key to making informed, effective decisions in automation.
