USD

Use Compact Industrial Robots to Make Any Shop More Productive

By Richard A. Quinnell

Contributed By Digi-Key's North American Editors

Major manufacturers have long used dedicated industrial robots to boost efficiency and throughput in their production lines, giving them cost advantages that smaller operations could not match. But industrial robots are no longer exclusive to large-scale production. Smaller, general purpose robots are now available to boost productivity for a wide range of operations, working alongside humans as partners in workspaces as small as two square feet.

This article looks at what has held robots back from large-scale deployment in smaller operations as co-worker robots and why that has changed. It then introduces example robots in the form of manipulator arms from KUKA Robotics Corp. and shows how they can be applied in both large and small facilities.

The rise of robotic co-workers

Several factors have historically limited industrial robotics to large scale operations. A principal factor was the difficulty in generating a return on investment (ROI). Early industrial robots required considerable design effort and were customized—unique to their task. As a result, they could only handle a narrowly defined range of operation. The resulting cost and inflexibility meant that the robot had to offer substantial efficiency and throughput improvements over manual methods and be utilized in a high-volume production line to justify its implementation. Small to mid-sized facilities could seldom meet such conditions.

To maximize benefit, most industrial robots for large-scale operation have also tended to be large and fast, working with materials and at speeds beyond human capabilities (Figure 1). The momentum of the robot can be high enough to injure or even kill any worker struck while in the movement path. To keep workers safe, large industrial robots need to be isolated behind cages or other barriers with interlocks so that human entry into their operating space will shut them down.

Image of traditional industrial robotsFigure 1: Traditional industrial robots tend to be large and fast-moving, requiring protective cages to ensure worker safety. (Image source: KUKA Robotics Corp.)

The introduction of compact robotic manipulator arms, such as the AGILUS KR 3 R540 from KUKA Robotics, has given industrial facilities managers more options (Figure 2). These devices provide a generic, off-the-shelf platform offering considerable operational flexibility at a relatively modest cost. Coupled with suitable end-effector attachments such as grippers or tools mounted at the end of the robotic arm, these generic platforms greatly expand the range of activities for which a robotic system can be created to generate a suitable ROI. Further, these robotic arms can readily be programmed for different movements or repurposed with different end-effector mechanisms when their initial applications expire, extending their payback potential.

Image of AGILUS KR 3 R540 manipulator arms from KUKA RoboticsFigure 2: Manipulator arms, such as the AGILUS KR 3 R540 from KUKA Robotics, are bringing ROI for industrial robotics within reach of small to mid-size operations. (Image source: KUKA Robotics Corp.)

Another key feature of these compact industrial robotic arms is their ability to fit into compact workspaces and integrate with existing production efforts. Unlike their more massive cousins in large manufacturing facilities, compact robots can also serve as a partner to human operators rather than a replacement for them. Such compact collaborative robots—or cobots—are designed for physically close human collaboration without the need for protective cages or other such barriers to keep humans out of harm’s way as the robots go through their paces. Compact robotic arms are less massive and move more slowly than traditional industrial robots, allowing compact robots to stop on contact, minimizing the potential for injury. Further, they often have proximity sensors built in to help avoid collisions entirely.

A growing number of vendors have begun producing compact industrial robotic arms targeting small to mid-size operations. One representative example is the KUKA Robotics AGILUS family, which has three versions. The AGILUS KR 3 R540, mentioned earlier, is the smallest. It operates within a two foot square footprint and can handle loads of up to 3 kilograms (kg), making it suitable for numerous assembly and materials handling applications. The AGILUS KR 6 R900-2 handles up to 6 kg and the AGILUS KR 10 R1100-2 up to 10 kg. All three have the same overall form and behavior and are available in kits, complete with a controller unit and handheld operator unit for controlling, monitoring, and programming the robot's activity.

The mechanical design of the AGILUS devices gives insight into the flexibility of robotic arms in general (Figure 3).

Diagram of six axes of motion in compact industrial robotic armsFigure 3: Six axes of motion provide flexibility in the mounting and reach of compact industrial robotic arms. (Image source: KUKA Robotics Corp.)

Like many robotic arms, the AGILUS devices have six movement axes: a rotating base (A1), a base arm (A2), a link arm (A3), an in-line wrist that can rotate (A4) and bend (A5), and a rotating mounting flange (A6) where end-effector devices are attached. Axes A2 to A5 work together to position the center of the wrist anywhere within the vertical operating profile, shown in Figure 4(a), while the rotating base can direct that vertical profile almost anywhere around the arm (Figure 4(b)). The center of mass for the end effector attachment can be offset from this position, as shown. The arm can be mounted on a floor, bench, cart, wall, or ceiling as desired without impeding operation.

Diagram of robotic arm position optionsFigure 4: Robotic arms can position the center of their wrist within a vertical region (a) oriented nearly anywhere around the robot's location (b). (Image source: KUKA Robotics Corp., modified by Digi-Key Electronics)

Controlling a robot's movement with all these axes used to require sophisticated programming skills, but that has now been simplified. Robotic arms typically come with a controller computer and a user interface tablet that allows a user to move the robot using simple directional buttons to reach desired "waypoints." Logging a series of waypoints defines the complete sequence of motions the robot can follow automatically. Some robotic systems also allow the user to manually position the robot arm to desired waypoints instead of using the directional buttons.

Both approaches serve to "teach" the robot by example what movements it is to execute, which it will then be able to repeat upon command. The ability for the user to teach rather than code not only simplifies initial robot setup for a task, it allows for easy adaptation of movement as requirements evolve. The control tablet further allows the user to refine and correct movements as needed during production activity.

These types of robotic arms with simplified control programming provide an off-the-shelf foundation for industrial automation solutions, serving as the position manipulator for an end-effector mechanism appropriate for the task to be performed. Such end-effector mechanisms can range from simple grippers for pickup, position, and place operations, to machine tools such as screwdrivers and drills, to complex systems such as soldering irons and paint sprayers. The target application will dictate what end-effectors and system integration efforts are needed to create a full solution.

End-effector mechanisms designed for many common operations are available from robotic arm vendors as well as third-party system integrators. For picking up and manipulating objects, for instance, there are grippers with jaws, two or three fingers, and magnetic or vacuum pickup mechanisms available from a host of different vendors. Drills, screwdrivers, grinders, and blades for fabrication and assembly applications can also be found.

Complete application solutions are even becoming available as stock solutions from robotic arm vendors. KUKA Robotics, for example, offers a series of "ready2 use" systems for riveting, paint spraying, arc or spot welding, and micro-screw fastening applications, among others (Figure 5). These systems include end-effector system elements, controller elements, and system software along with the robotic arm as a pre-configured automation package.

The painting package, for instance, was developed in conjunction with mechanical and plant engineering firm Dürr Group and is based on the AGILUS KR 10. It includes the atomizer, pump, and color changer for high and low pressure, one or two component, water or solvent-based paint applications. The Dürr EcoAUC control unit regulates the painting process while the KUKA KR C4 controller handles robotic arm motion.

Image of painting system from Dürr Group and KUKA RoboticsFigure 5: Compact industrial robots that are complete system solutions for common applications are now available "off-the-shelf", such as this painting system from Dürr Group and KUKA Robotics. (Image source: Dürr AG)

But users are not limited to such pre-configured systems when applying compact robot technology in their operations. Because of the robotic arm's installation and movement flexibility, ease of programming, and versatile end-effector attachment flange, a wide variety of custom applications are possible. The key is to identify repetitive tasks in an existing production process that the robot can assist with or take over from human operators.

Siemens, for instance, is using a small robotic arm in its electric motor production for the stator component. The stator is made of punched magnetic sheet steel with an aluminum bearing plate that needs machining to bring within tolerances. The robotic arm has taken over the repetitive task of taking workpieces out of a carrier, placing them in an automatic lathe for machining, removing the finished workpiece, cleaning it in an air blast, and placing it into a measuring station to check the tolerances.

The robot's controller works in conjunction with other pieces of equipment to scan the workpiece barcode for tracking purposes, and to move the measured workpiece either to a carrier for transport to the next processing station or to a holding station for a human operator to make adjustments or replacements as needed. The robot arm's safety features allow the human and robot to operate in the same workspace without protective fencing or other barriers that might impede workflow.

Tasks requiring repeatable precision are also suitable for robotic handling, even for small production runs. ALNEA, for instance, has set up a robotic arm to handle selective soldering in its SMT production line. Selective soldering is needed when components might be damaged by the heat involved in bulk wave or reflow soldering. Hand soldering an SMT device requires both a steady hand and careful timing to avoid solder bridges and heat damage.

In the ALNEA application, the robotic arm provides the steady hand while the end-effector soldering iron’s control system ensures both the temperature and timing of the soldering operation are within set parameters (Figure 6). With the first units of a production run, the human operator sets the soldering parameters and trains the robot arm on the movement sequence. Operators then help position the pc board and components for robotic soldering during the rest of the production run. The company saw a 50% reduction in production time by using the robot for selective soldering.

Image of robotic arms performing selective soldering in pc board productionFigure 6: Robotic arms can provide the steady hand and precision positioning needed for applications such as selective soldering in pc board production. (Image source: KUKA Robotics Corp.)

The task to be automated may not even need to be a complete operation to prove economically beneficial. For example, the BMW Group has integrated a robotic arm into its existing workflow for the production of reinforced side members in automobiles simply to relieve the human operator from a repetitive task requiring precision that human operators found difficult to sustain throughout a work shift. The task was to position a number of metal reinforcement plates at points along the frame prior to inserting the frame into an automated welding station. However, the strain of repeatedly performing this otherwise simple task of positioning resulted in increased errors and reduced throughput as the day wore on.

BMW inserted the robotic arm into this operation specifically to take on the task of properly positioning the plates once the human operator had counted out the right number of plates and provided them to the robot. No other changes to the workflow were required. But by assuming the precision placement portion of the operator's task, the robot reduced fatigue-induced errors and ensured sustained production throughput throughout an entire shift. The robot's safety features allowed it to work alongside the human operator without a need to modify the workspace.

Conclusion

Industrial robots have traditionally been associated with large industrial facilities, mainly due to cost, complexity, and safety. However, an ever widening array of repetitive tasks, from simple positioning to painting complex shapes, are becoming economically feasible for compact industrial robots.

With their modest space requirements, simplified programming, falling costs, and ability to readily and safely integrate into an existing, human-centric workflow—without the need for physical barriers—such robots are able to gracefully join the workforce without disruption. Now, industrial automation is no longer just for large, high-volume operations with deep pockets: small shop operations can also incorporate a robotic hand.

Disclaimer: The opinions, beliefs, and viewpoints expressed by the various authors and/or forum participants on this website do not necessarily reflect the opinions, beliefs, and viewpoints of Digi-Key Electronics or official policies of Digi-Key Electronics.

About this author

Richard A. Quinnell

Richard Quinnell has been an engineer and writer for 45 years, covering topics such as microcontrollers, embedded systems, and communications for a variety of publications. Prior to becoming a technical journalist he spent more than a decade as an embedded systems designer and engineering project manager for companies such as the Johns Hopkins University’s Applied Physics Laboratory (JHU/APL). He has degrees in electrical engineering and applied physics, with additional graduate work in communications, computer design, and quantum electronics.

About this publisher

Digi-Key's North American Editors