Six use cases for collaborative robots

The field of collaborative robotics has expanded in 10 years and is the fastest-growing global industrial robotics market segment. Leading that expansion are six application areas. The most common collaborative robot applications are pick and place, machine tending, packaging and palletizing, process tasks, finishing tasks, and quality inspection. A collaborative robot (also known as a cobot) is a robot with the ability to safely work alongside human workers to complete a task. Technology accessibility through ease of deployment is similarly integral to the collaborative robot definition.

A robot that can operate alongside and interact with its co-workers opens up many new possibilities for task automation, but many of these possibilities could go unfulfilled if the robot system is not easy to program, affordable, and flexible enough so it can be re-deployed to different tasks on short notice.

Flexible collaborative robot systems are being deployed in many applications and industries globally. Below are six of the most common collaborative robot application areas along with advice on how to implement a collaborative robot into the application, and what accessories are required.

1. Pick-and-place collaborative robots

A pick-and-place task is one in which the robot is required to pick up a workpiece and place into another location and or orientation. The handling of the workpiece is the key action rather than any other process. In the simplest instance products will be presented to the robot in a uniform layout tray or pallet or on a conveyor in predictable position, where in more complex cases a vision system may determine product orientation. A pick-and-place task is an excellent first collaborative robot automation application because its highly repetitive nature and simple movements make set up easy.

Accessories for pick and place

End-effector: Either a vacuum cup or a gripper could be suitable, depending on work piece size and shape. If it has a smooth, flat upper surface and will be placed in the same orientation it was picked, a vacuum-based effector is a good choice. If there are no flat surfaces, or it needs to be placed in a different orientation, then an adaptive gripper may be required.

Vision system: If the products arriving for the robot to pick are in a non-standard position or orientation then it may be necessary to integrate a simple vision system to detect the orientation of the part.

Programming: Programming a pick-and-place application is often straightforward. Move to a pick location, activate the end-effector, then move to a place location and deactivate the end-effector. In the simplest case, both pick-and-place locations could be fixed, but often one or both positions need to be adjusted each cycle, as they are in a grid or stack orientation (palletizing or seek functions in the software can help), or vision guidance. Cameras and other plug-and-play products may be certified by the collaborative robot manufacturer. Certified products include grippers, software, accessories and other end-effectors and accessories. Plug-and-play products are designed to work seamlessly and reduce deployment time.

2. Machine tending collaborative robots

Machine tending is another common application task. Machines being tended include computer-numerical control (CNC) machines, injection molding machines, laser engravers and metal-stamping presses. The robot picks a blank unprocessed product from a tray, stack, conveyor or some other feeder configuration, and places it into a fixed location in a machine.

Once the machine cycle is completed, the robot removes the completed part and puts in another blank. If the machine cycle is long enough to allow it, one robot can tend multiple machines simultaneously, accelerating the return on investment (ROI). Due to the small footprint of some collaborative robots, they often can be installed to leave space for an operator to access the machines if needed and without adjusting factory layout.

Accessories for machine tending

End-effector: A machine tending application will often use a dual-gripper configuration, with one gripper picking and placing the blank, and one the completed part. This reduces cycle time with the robot handling both parts in one movement inside the machine.

Vision system: If the products arriving for the robot to pick are in a non-standard position or orientation then it may be necessary to integrate a simple vision system to detect part orientation.

Programming: Robot movements for a machine tending application are often simple, moving between ingoing and outgoing product positions and the fixed machine position. Some input/output (I/O) interfacing is usually required for the robot to tell the machine when the part is in place and the cycle can begin, then for the machine to tell the robot that the cycle has finished and ready for the next part. For machines like CNC or injection molding, additional signals will be required to synchronize the handover of the part and to let the machine know when the robot is outside the machine so the door can be closed.

If the robot is tending multiple machines, some additional logic will be necessary to decide which machine to tend to next if the cycle times aren’t identical.

3. Packaging and palletizing collaborative robots

Before any product leaves a factory or facility, it is likely it needs some form of packaging before shipping. Packaging and palletizing tasks could involve packaging a product by placing it into a shrink-wrapping machine, picking packaged products from a conveyor and collating them into boxes, or placing these boxes onto a pallet for shipping.

Rigid products arriving in standard orientation are easy to handle, though a simple vision system may be required to detect orientation of parts if not uniform. If less rigid products, such as sachets, are presented and need to be tightly packed into boxes, extra consideration on the handling method is required, but still possible.

For businesses running high-mix low-volume production, rapid product changeover is key, so an easy programming interface allows for reconfiguration of an application within minutes.

Accessories for packaging and palletizing

End-effector: Packaging and palletizing tasks are often handled with an array of vacuum cups to pick up and release products. In the simplest form, these can be attached to one flat plate, but also can be set up so positions are reconfigurable, allowing different-sized products to be picked with the same tool.

Conveyor tracking: Synchronizing robot movement with a conveyor to pick products on the fly is simple with a conveyor tracking wizard. Connect a position sensing encoder to input channels in the controller (or via Modbus fieldbus), configure the direction and speed ratio, and the robot is ready to track the movements of a variable speed conveyor. If this is an end of line conveyor, where the products hit a mechanical stop at the end, it is not necessary to track the movement of the conveyor as the pick position is fixed.

Vision system: If the products arriving for the robot to pick are in a non-standard position or orientation then it may be necessary to integrate a simple vision system to detect the orientation of the part.

I/O interfacing: A few inexpensive light sensors (photoelectric) connected to the controller will allow the robot to detect the presence of arriving products and the box into which parts are to be placed.

Programming: Setting up the program for this type of application is similar to a pick-and-place application, with the pick often from a fixed position, triggered by a sensor input. The place positions will vary for packing into boxes or palletizing, with either a horizontal offset within a layer, or a vertical offset between layers, easy to set up in the software. For a more complex palletizing pattern, it may make more sense to enter the dimensions and locations of the place positions parametrically instead of teaching/offsetting them manually.

4. Process tasks (gluing, dispensing or welding) for collaborative robots

For process tasks such as gluing, dispensing or welding, the key details are the same: The robot moves a tool through a fixed path while the tool interacts with the workpiece. In each of these process tasks, it takes a significant amount of time to train a new employee to control numerous variables required to attain an excellent quality finish. If this control can instead be copied directly from one robot to another, the process becomes more straightforward.

A traditional robot welding system requires significant welding and robot programming expertise to set up and is often more expensive than a welding torch alone.

Accessories for process tasks

End-effector: A process tool such as a welding torch, sealant, glue or solder paste dispenser, is required. The tool often does not need to be designed for robotic operation, which may reduce integration costs. Turning the tool on and off is achieved using standard digital I/O signals, with the potential addition of an analog signal to control deposition rate.

Programming: Programming software process move option maintains a constant transmission control protocol (TCP) speed, meaning if the robot tool is depositing material at a constant rate, the system achieved constant coverage throughout the programmed path. The simplest method of programming a process task is defining the key waypoints within a process move along with blend radii, allowing the robot to curve around the corners in the path.

If the system is required to deal with a large number of rapidly changing parts, for which the computer-aided design (CAD) models and computer-aided modeling (CAM) process paths are available, then it may be more convenient to import these paths into the robot program rather than teaching them manually. This can be achieved with third-party software packages, outputting programs from the CAD/CAM data to be executed on the collaborative robot system.

5. Finishing tasks (polishing, grinding or deburring) for collaborative robots

A finishing task requires the robot end-effector to apply a force across the surface of a workpiece to remove a certain amount of material. Polishing, grinding and deburring differ in amount, form and location of material to be removed, but the robot’s requirements are essentially the same.

When a person completes a finishing task with a manual tool, this often requires the worker to apply a large amount of force to the workpiece, generating a significant amount of vibration which can lead to injury over time. Such injury could be avoided with robotic operation. Finishing tasks often use the process move command mentioned in the processing task, and a robot can either be manually taught the path to complete the task, or it can be exported from CAD/CAM data directly to a program.

Force control also can make the robot more robust when dealing with parts of different dimensions. This can either be achieved with the robots’ internal force sensing capabilities or a wrist-mounted external force torque sensor depending on the sensitivity required.

Accessories for finishing tasks

End-effector: A finishing tool is required for this type of application, which could either be designed for general purposes (manual) or specifically robotic purposes. While manual tools are generally cheaper, and can be powered on and off by the robot, their controls are often controlled by push buttons, while robot tools include an I/O interface for direct control.

Force torque sensor: If the task at hand requires force control in the sub-Newton range (phone case polishing, for example) then users may want to consider adding additional sensing to the robot for finer scale force control.

Programming: Programming for a finishing task in its simplest form is very straightforward by navigating along a fixed path and activating the tool at the relevant points

6. Quality inspection for collaborative robots

Quality Inspection involves full inspection of a finished product, especially one that is the result of a precision engineering process, often requiring high-resolution images to be captured from many angles to confirm all of the surfaces and dimensions conform to the required specifications. The cameras capturing these high-resolution images are expensive so requiring, for example, 10 cameras to inspect a product is not cheap.

If one camera is mounted on a robot and moved around the product to all of the fixed capture positions, however, the costs of this type of automated inspection system significantly drops. In a fully autonomous application, the robot also may be equipped to move the parts in and out of the inspection jig, either from a tray or conveyor, which requires minimal supervision.

Accessories for quality inspection

Vision systems: The main accessory involved in a quality inspection application is the vision system, including the camera and software to process the images. Often the system required will be a more high-end system than the vision system used to locate a part for the robot to pick it. Configuration doesn’t necessarily have to be complicated thanks to increasingly capable vision processing algorithms.

End-effector: If the robot also is required to handle the part in and out of the inspection location, then a gripper should also be mounted on the robot alongside the camera to move the part.

External jig: Once the robot places a part, it may need to be clamped in place in a jig to fix the position.

Programming: Setting up this type of application is generally straightforward. In the instance the robot does not need to handle the part directly; the program will consist of moving to fixed waypoints then triggering the camera via digital I/O or Ethernet communications. A pick-and-place operation also may be added to this in case the robot handles the part.

[subhead]Lowering the automation barrier

The common applications discussed here can be rolled out in a very short period, especially when using the wide range of plug-and-play accessories available with some collaborative robots as part of an ecosystem where automation is accessible for all.

First-time collaborative robot adopters can learn a lot of the required skills for implementation with free interactive online training aimed at newcomers to robotic automation. By giving existing staff the opportunity to operate and program a collaborative robot system makes a robotic implementation more rewarding. Using easy-to-implement collaborative robots also provides a more attractive workplace environment for new staff.

Joe Campbell, senior manager, applications development, Universal Robots. Edited by Mark T. Hoske, content manager, Control Engineering, CFE Media, mhoske@cfemedia.com.

KEYWORDS: Collaborative robots, robot applications

Most-common collaborative robot applications include pick and place, machine tending and packaging.

Plug-and-play effectors ease implementation and can speed set up in other applications.

Programming, machine vision, I/O connections and training are among other considerations.

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