With advancements in manufacturing processes and materials, components in many industries are more precise with a new level of complex shapes. There is significant demand to create parts and assemblies that perform better, last longer, and cost less to make. Manufacturers are increasingly focused on robotics or other automated systems to produce, assemble, and inspect these components. The new generation of robotic manufacturing cells incorporates advanced metrology sensors that enable them to perform tasks more accurately and with greater versatility. These robotic cells are typically referred to as Metrology Enhanced Automation (MEA).

Quality’s Evolving Role

This metrology enhanced automation cell is being utilized to verify operational accuracies for drilling in an aerospace environment. In a real-time control loop, the planned trajectory of the robot is constantly monitored by a Leica Absolute laser tracker. As the end effector starts to move or drift from the desired path, the deltas are then fed back into the robot kinematics and the process repeats.

Forward-thinking manufacturing professionals understand the value of bringing the quality function closer to the shop floor where parts are made. The goal is to be able to feed dimensional data back into the process quickly to improve the next part. While this is a good objective, what if quality became an integral part of the manufacturing process instead of just getting close?

New MEA systems embed metrology sensors within the manufacturing cell to create a robotic system that is more adaptable to part and process variability and can complete the inspection process at the same time. Envision this solution as a more ubiquitous and integrated quality system where metrology sensors act much like our own human senses and allow us to adjust to the world around us.

The Integrated Metrology and Manufacturing Cell

This Leica Absolute Tracker is being used in Spain for the MEGAROB automated platform for high-accuracy manufacturing of medium and large components. The MEGAROB project developed a flexible, sustainable, and automated platform using a spherical robot, a seven-degrees-of-freedom-enabled Leica Absolute laser tracker, and an overhead crane.

A good example of a MEA system is a laser tracker integrated into a robotic cell. Laser trackers use encoders and a laser interferometer to measure points in three-dimensional space to a high accuracy. In the marketplace today, there are multitudes of laser trackers measuring components in aerospace, automotive, shipbuilding, and virtually any industry that manufactures products the size of a small car or bigger. The typical laser tracker accuracies are ±.001" within a 20-foot radius. The portable measurement system can also measure up to 262 feet with slightly less accuracy.

The laser tracker essentially becomes part of a feedback loop and can track the position of the robot’s tool center point (TCP). Alignment features on a part or fixture can also be measured in the same coordinate system. The robotic cell can acclimate to the variability in a part or adapt to how it may be loaded into an assembly or drilling fixture. This same feedback loop can enhance a robot’s positional accuracy by comparing the robot’s TCP readings to the actual position as measured by the laser tracker. Correctional data is transmitted to the robot at speeds up to 1,000 Hz.

Metrology assisted machine control and robotic guidance using laser trackers is a reality for plant operations today. Commercial off-the-shelf robots coupled with Leica Absolute trackers are used for inspection, assembly, and manufacturing operations such as drilling, eliminating the need for very expensive fixed tooling, multiple operators, and many days to accomplish these tasks.

The extraordinary result is a robot that performs anywhere from two to six times more accurately than the robotic cell could do without the integrated laser tracker. The robotic cell can also execute the final inspection on the part, eliminating the need to send a part to a separate inspection room. A key aspect of this process is that the accuracy and integrity of the quality system remains independent of the robot itself.

Planning for Success with Integrated Robotic Cells

An advanced MEA robotic system can be designed to include a single cell with a robot that can pick up a drill head or a noncontact metrology tool like a Leica T-Scan scanner.

There are a variety of sensors and technologies being integrated with an automated cell, depending on the unique application, such as laser line scanners, structured light solutions, and vision systems. Moreover, creating systems that use sensors to adapt to their environment is a key part of the Smart Factory concept. All of these new capabilities make it extremely critical that MEA systems are designed from the beginning to maximize efficiency.

The thought process should not just be automating the existing process, but rather how a manufacturer can change the entire value chain of a part based on today’s proven technologies. If the deliberation is not broad enough, there is a risk of limiting the capabilities of the MEA system and a company’s return right from the start. It is in the early stages of building a system where minds can come together to create the scope of work, consciously deliberate the whole process, and not simply automate a single step. This process is sure to generate a return on investment (ROI) that is two to five times greater for the manufacturer.

A Case in Point

To gain a better understanding of the potential of implementing MEA systems and rethinking the entire value chain, consider a hypothetical example of an aircraft assembly requiring drilling and fastener installation. The value of a robotic inspection cell only will be compared with a metrology-enhanced robotic drill cell that combines multiple operations into a single manufacturing cell.

In the first scenario, the typical robotic inspection cell consists of a robot with a metrology sensor, part fixtures, safety systems, and software. These systems are typically well built to move fast and handle the rigors of a shop floor environment. The benefits provided are reduced labor, improved data accuracy and reliability, and increased speed at which parts are verified. The payback depends on inspection complexity, volume of parts, and the value. A manufacturer can typically see a good payback on investment in 2 to 2-1/2 years and in many applications, this may be the right solution for the job.

In the second scenario, the whole value chain is considered and metrology equipment is integrated into the manufacturing systems. Remember in this example, the focus is on a typical aerospace part that requires a manual drilling operation and fastener installation, which is a common task in that industry. The manual drilling process requires a laser-drilled pilot hole and expensive fixtures to assemble the parts within engineering tolerances.

By taking into account the entire value chain of the part, an advanced MEA robotic cell can be scoped and designed to include a single cell with a robot that can pick up a drill head or a noncontact metrology sensor that provides realtime feedback to the robot. In this scenario, the cell that is created can perform a quick check on components and align to the assembly, allowing a less-expensive fixture. With precise repeatability, parts can be drilled using a robot — a vast improvement over a manual, not-so-accurate process. The robotic drill head can be adapted to the part and eliminate the need for pilot holes. And lastly, final inspection can be performed utilizing a metrology device that is independent of the robot.

By “deep-thinking” the process and implementing a robotic cell that integrates metrology, there will be multiple touch-points of impact on a part’s entire cost, cycle time, precision, and scrap rate. Typical payback periods of one year or less can often be achieved with a more advanced cell.

Challenge the Status Quo

In today’s competitive global environment, manufacturers with a data-driven mindset are challenging the status quo and seriously pursuing new, efficient ways to produce parts. New hybrid technologies such MEA are changing the conversation about automation and delivering fresh solutions that arm robotic cells with precision and the capacity to autonomously adapt to the variability of a manufacturing process.

Realizing the value of a Smart Factory is not an all-or-nothing proposition. The evolution of advanced manufacturing will be achieved through incremental improvements. This seismic shift toward using actionable information to improve processes and productivity is forcing manufacturers to rethink the role of technology in general, and advanced metrology sensors specifically. The capabilities are real and being leveraged by forward-thinking manufacturers right now.

This article was written by Steve Starner, Director of Business Development – Aerostructures, at Hexagon Manufacturing Intelligence, North Kingstown, RI. For more information, visit here.