The Facts about Hand Guiding Robots
Part 1 – Hand Guiding Robots
here are four methods for collaborative robot (or cobot) operation defined in the RIA 15.06-2012 safety standard, and each has its own place in manufacturing operations. Of the four, hand guiding seems to get the least amount of attention. In the safety standard, section 5.10 (Collaborative Operation Requirements) defines the requisites necessary for having robots function in collaborative operation as complying with one or more of the following:
- 5.10.2 Safety-rated monitored stop
- 5.10.3 Hand guiding
- 5.10.4 Speed and separation monitoring
- 5.10.5 Power and force limiting by inherent design or control
Hand guiding is simply defined as having equipment, such as a hand guiding handle, positioned near the robot tool or end-effector. This equipment includes both an emergency stop and an enabling device, similar to a live-man switch found on a teach pendant. Many automation users view hand guidance simply as lead through teach, which is the ability to move the robot freely to teach points or paths in the operation. This opinion is fairly common, but teaching by demonstration is just the beginning among the many areas that could benefit from using hand guidance techniques.
A frequent opinion is that hand guidance applications face limitations when dealing with longer reaches or heavier payloads. This is because there are only a few large cobots on the market. It's true that most power and force-limited collaborative robots may not be suited for very large tasks. However, it's essential to recognize that the majority of robots can be used in collaborative scenarios.
At the core of collaborative robots or collaborative operation is “collaboration”- to work jointly with others. Collaboration with a robot is frequently thought of as working hand-in-hand with the robot to complete a task. Hand guiding essentially involves an operator using their hand to lead or move the robot, representing a type of collaborative operation that truly embodies the essence of teamwork.
Remember that the best way to use collaborative robots is to have them and the operator work together only when needed, while each handles their own tasks in separate areas. It’s not much different when sharing a work station with another person. When integrating tools to assist operators, the devices should increase efficiency and decrease stress or strain. If you're always reaching or moving around your partner, whether they're a person or a robot, it makes the whole process less efficient. It is important to examine the task carefully and consider the solution you want. This will help you find the best collaborative robot for your needs. In part 3 of this article, we’ll review a few collaborative applications for both small and large companies.
Part 2 – Hand Guiding - Flexibility and Functionality
According to section 5.10.3 of the RIA 15.06-2012 safety standards, hand guiding equipment needs to have an e-stop and enabling switch. However, in cases where hand guiding is used on a robot that meets the requirements of power and force limiting collaborative operation, the e-stop and enabling switch may not be necessary. For these reasons, it really helps when there are multiple hand guiding options. FANUC offers two types of hand guidance handles, one includes the necessary integral safety for standard robots, and the other is wireless and works with the CR series of power and force limiting robots.
A product with many functional options is similar to a well-equipped toolbox—though you might not use every tool constantly, having them available can assist users in overcoming obstacles efficiently when needed.
The FANUC hand guiding product has a variety of built-in features, or tools for teaching-based applications. The hand guidance software is configured to teach paths or points, and a simple push button triggers the action.
What is point based teaching? In point-based teaching, the user guides the robot using the hand control to a specific spot and then presses a button to save that position. The user continues to guide the robot to the next position and records the point. Repeating this process can quickly generate a complete motion program for the entire application. Point based teaching is an intuitive process that’s especially easy for those who have never used or programmed a robot.
What is path based teaching? For some processes, recording the robot’s complete path motion is required. This method applies to applications like sanding or polishing over a complex contour surface when it’s essential to have a smooth path that follows a shape. Hand guiding software automatically records the robot's positions during movement. It then replicates the entire path with accuracy. The operator simply presses and holds the teaching button and then moves the robot along the path. As the robot moves, positions are generated at preset intervals. Once the motion is complete and the button is released, the path is generated in the program. If fine tuning is needed, each position can be individually modified to achieve the perfect path.
Another great feature of the hand guiding handle is a button to control the tooling. Each press of the button will toggle the state of the tool. This is especially useful in robotic applications where an operator needs to move a part from one location to another. There are programs that can restrict the gripper's operation at the pick-up or drop-off points. This ensures the operator does not accidentally release the item outside the designated areas. Some applications might require slower, more precise robot motion in critical areas. A button is included that can automatically change the motion of the robot under hand guidance control to a slower speed for better control of the robot’s position.
In other situations, it may be best to limit the robot’s motion to only linear movement, not allowing rotation of the tool. A button is included to switch the motion profile from rotational articulation to only linear motion.
The more extensive wired hand guiding device features an extra button. This button is used to program applications that need maximum process control and flexibility, like multistage operations. It's also useful when local safety rules demand that the robot be operated with both hands.
This extra button shows that the hand guidance part of the application is finished. It lets the robot go back to working on its own when safety rules are followed, like when the operator leaves the area. Depending on your application, you may not need all of the tools available with FANUC’s hand guiding product, but each feature is built in and ready at a moment’s notice.
Part 3 – Hand Guiding Applications
Now that we know what hand guiding collaborative operation is, and all of the features that are available with the product, how are companies using this product?
As stated in Part 1 of the article, it is usually advisable to categorize hand guiding applications based on their functions.
Application Example 1 - This application has an operator using a manual lift assist device to load parts into an assembly station that feeds into the rest of the line. The operator walks the lift assist device to the part rack and picks the part, then walks the part to the assembly station and loads it into the fixture. Once the part is in place, the operator moves the lift assist device out of the way so it doesn’t interfere with the rest of the operation. Rather than automatically substituting the lift assist with a hand-guiding robot, let's analyze the functions of the application individually.
Part 1 is an autonomous robot operation requiring the robot to pick a part out of a rack and bring it to the operator. Setting up a light screen between the robot and the operator will enable the robot to run safely in automatic mode when properly configured per the risk assessment. This allows the robot to relieve the operator by handling the repetitive and heavy lifting part of the process.
Part 2 begins once the robot picks the part and brings it to the light screen. At this point the operator reaches through the light screen, which puts the robot in a safety rated zero speed check. Once the enabling switch is activated, the robot motion is in the operator’s control who then guides it into the assembly area where the part is loaded into the fixture. Once the part is released, the operator guides the robot back through the light screen. When the enable switch is released, the robot returns to the safety rated zero speed check until the light screen is cleared. The robot can then resume autonomous mode and return to the part rack for the next part. The operator performs the assembly operation and then sends the part down the line to the next station. By not having to get parts manually from the part rack, the operator’s time is freed up to perform additional value-added work.
System Advantages - By saving time, it might be possible to decrease the number of assembly stations on the line, as the operator can complete extra tasks during the time allocated for the first station. An additional benefit is that by the end of the shift, the operator will be less tired from not having to walk between the first station and part rack for each part cycle.
Application Example 2 - This example involves an existing collaborative weld inspection station. This Safety Rated Monitor Stop system has the robot bringing a welded frame into a shared workspace. Once the robot is stopped, the weld inspector enters the shared space and inspects the weld. On occasion when welds need to be touched up, the part may not be at the ideal angle to weld. Instead of requiring a technician to go to the cell and jog the robot, hand guidance is used. The hand guiding handle is attached to the tooling in a convenient location for the weld inspector to access.
System Benefits - Enabling hand guiding allows the part to be easily moved to the right position for weld touch ups. This also allows the inspector to view multiple sides of the part by manually moving it with the hand guiding handle. This application now incorporates two types of collaborative operation and is a great example of how sometimes multiple types of collaborative operation can be engineered together to provide the ideal manufacturing solution.
Application Example 3 - A good starter/DIY application involves using hand guidance to simplify a vision process where part styles or trays are manually changed. The system setup first requires the operator to place a tray of parts on a table. The robot uses vision to find the tray and the first part, and then begins the process.
As part trays change, the robot’s viewing position must be adjusted. Using hand guidance can relieve the operator from having to put the robot into teach mode to make ‘vision find’ changes on the teach pendant. Once this function is pre-programmed, the operator can make needed changes using the hand guidance tool. The extra process button on the hand guidance tool communicates that the operator has moved the robot by hand to a new ‘vision find’ position. The robot then uses the new position taught with hand guidance until the next part tray change.
System Benefits - For new users or do-it-yourselfers, this method is extremely easy to use compared to modifying a robot program, and helps save valuable time.
Application Example 4 – Many high mix / low volume welding shops are experiencing a lack of trained and qualified welders. Adding hand guidance to an arc welding robot allows an operator with basic welding knowledge to easily teach programs to weld their small batch parts. The operator uses hand guidance to move the welding torch so the wire is in the proper position for the weld joint. The buttons on the hand guidance hardware provide a simple user interface that make it easy to create an entire program for any part. The operator can then let the robot weld the part while they move on to the next weld station.
System Benefits - Robot hand guidance alleviates the need for the welder to be proficient in jogging and programming the robot with the teach pendant. When the welder can easily program the robot, they can keep production going at different stations with many types of parts.
As more small and medium manufacturers use robots for different tasks, hand guidance tools and methods will grow in function and become easier to operate.
