By: Christian Stevenson, Sr. Engineer, FANUC America
Companies all over the world are evaluating their production operations to determine how to increase productivity. That’s a key reason why the demand for robotics and automation is growing at a rapid pace.
Mobile robots have become a popular solution for a variety of industries, including eCommerce, where the robot can move quickly from one location to another to pick products for order fulfillment. Now, many industries are looking at using cobots on a
mobile platform to offset the shortage of skilled workers, improve productivity, meet critical deadlines, and maximize ROI.
Companies that machine parts not only face labor shortages and productivity issues but are now challenged by customer demands to handle low-volume, high-mix work. A very flexible and safe solution is mounting a cobot to a mobile platform like an autonomous
mobile robot (AMR). This type of
mobile robot solution makes it easy for one worker to move the robot to different machines around the plant floor and quickly set it up
for any number of tasks – a huge benefit that allows companies to meet their customers’ demands and, at the same time save time and money. It also allows skilled employees to stay in the cobot’s work cell to handle other tasks while
the cobot does the repetitive loading and unloading.
Mobile Manipulator Demonstration
FANUC recently demonstrated flexible machine tending featuring its latest CRX-20iA/L cobot mounted on a platform. An OTTO 100 AMR docked under the platform was used to lift and transport the cobot to autonomously complete a variety of common
tasks found in any job shop, including part kitting, washing and machine tending. This system, designed and built by Capriol (West Bloomfield, MI), is an excellent example of how a cobot’s capabilities can be expanded, turning it into a
true mobile manipulator.
Powerful AMR
The OTTO AMR, yielding about two hours of runtime, is used to power the equipment onboard the platform between the cobot and the AMR. Much more than a simple mechanical link between the two, the platform contains the necessary equipment to power the cobot
with the AMR’s batteries, wireless communication equipment for the cell PLC and I/O connections for application-specific sensors.
So, in this example, the AMR’s batteries last for two hours. At the two-hour mark, the AMR swaps places with another fully charged AMR. A stable secondary power supply (UPS) enables the cobot to finish its cycle, and the system continues to run with
no lost productivity.
Localizing with 2D Vision
When using mobile manipulators, a docking station’s position and orientation must be verified every time using some form of localization to ensure repeatable robot motion. What can impact repeatability?
- When a mobile robot docks at a station, repeatability can vary by several centimeters.
- Since floors are not perfectly level, any small dip or bump can significantly change the position of the cobot’s end-of-arm tool.
2D Vision can solve the issues within seconds. This is accomplished by adding a vision target (a camera calibration grid) to each station and teach all the target’s positions. When the mobile manipulator arrives at a station, a 2D camera takes several
images of the target and calculates its position and orientation relative to the robot. This establishes the target’s position, and all subsequent robot motion at the station is just as accurate as when it was first taught.
CNC Servicing
There are many ways for a CNC machine to communicate with a mobile manipulator. The recent demonstration attempted to mimic a human operator as much as possible, so vision was used for communication between the CNC and the rest of the cell.
When the machine finishes a cycle, it opens the door and uses the stack light to indicate service is required. The mobile manipulator arrives at the machine and checks the light to confirm it’s ready. After completing tasks at the machine, the robot
presses the cycle start button and checks the stack light a final time to verify the machine is running before it leaves the station.
Another application might use networked communication to talk to the CNC machine, potentially yielding a more efficient solution. In this case, the CNC machine can signal when it is almost finished with a cycle, and a mobile manipulator can be dispatched
early so it arrives right as the machining cycle completes, improving efficiency.
Collaborative Technology
The CRX-20iA/L used on the mobile manipulator is a power and force-limited collaborative robot. The mobile manipulator system also has laser scanners mounted on two corners offering 360-degree coverage. These two safety-rated systems (the cobot
and the area scanners) can be used together to achieve a safe system.
For low-risk tasks, the FANUC cobot provides safe operation without the need for safety scanners. If higher speeds are required or the task is riskier, such as handling a sharp part, then safety scanners can be used to prevent the arm from moving when
operators are near. The key here is flexibility - the power and force-limiting features of the cobot can be augmented by the area scanners to achieve a safe system in a way that makes sense for each unique application.
Mobile Robot Navigation
There are several advantages of utilizing an AMR like the OTTO 100 to transport a mobile cobot/manipulator, including:
- Flexibility to respond to unexpected obstacles by automatically rerouting around obstructions.
- Large wheels allow the AMR to travel over factory floors, even those that are cracked or have bumps.
- Straightforward route map setup – it takes just one manual drive around the site, and the AMR’s map is set. The map is then populated with stations, chargers, and other points of interest.
OTTO’s robust Fleet Manager software enables everything from programming simple waypoints to defining complex factories integrated into building infrastructure. Changing machine location or workflow is as simple as adjusting destinations on the
map – the AMR handles everything in between.
Maximizing Return on Investment (ROI)
Before investing in a mobile manipulator system, it’s important to work with a reliable automation supplier who will conduct a thorough review of your operation to be sure the automation is used efficiently. In the above example demonstration, a
cobot performs different tasks at each station. An alternative and possibly more cost-effective approach might be to use fixed robots at each station to perform process tasks and only use the mobile manipulator to move parts between stations and fixtures. This keeps the mobile manipulator moving as much as possible, allowing it to service more stations versus using it to perform tasks at each station.
Mobile machine tending is an investment that pays off in consistency and flexibility. Machine loading is performed with robotic precision and part throughput doesn’t change from shift to shift. Robots don’t attend meetings and they don’t
mind working three shifts. Thinking long-term, a mobile solution is the most flexible: a rail-mounted robot may initially be faster, but changes are expensive and require significant rework. A mobile solution easily accommodates layout changes,
expansions, and even complete workflow changes.
Another way to look at ROI is employee satisfaction and retention. By automating the strenuous and repetitive tasks of loading and unloading CNC machines, you can reduce the risk of employee injury, making their jobs much safer. When your employees can
focus on higher value tasks, they will be more satisfied with their workplace, thereby decreasing turnover and limiting your need to specifically hire manual laborers in those positions.
Summary
When it comes to machine tending, there are always checks and balances to review before implementing any new equipment or processes. Thinking long-term, a mobile manipulator is a very flexible solution that can help you meet customer deadlines, maximize
your productivity and help you overcome labor challenges.
Imagine implementing a system like the one highlighted in this article to tend CNC machines, then a couple years later an inspection station is required. With a mobile solution, this workflow change can be quickly implemented by programming the robot
at the new inspection station and simply adding a destination to the map. Alternatively, if you are strictly a manual operation, major changes to the process would require additional manpower and scheduling – but what happens if you’re
not able to fill the jobs? And, if a linear rail had been previously installed, an expansion may not even be possible – where would you find the additional floorspace?
A mobile solution’s flexibility is its most important benefit and a key reason behind the growth of mobile robots in automation. If you’re considering automating one or more machining process, you may want to take a closer look at a mobile
solution. For more information contact FANUC.
Christian Stevenson is a senior engineer in FANUC America’s General Industries and Automotive Segment. His responsibilities include strategic application support, world-class tradeshow cells, and guiding new product development, including collaborative and mobile robot applications. Christian started his career at FANUC in 2018 after graduating with a Bachelor of Science in Mechanical Engineering from the University of Michigan.