Case Study: One-of-a-Kind Kawasaki Robot Cell for Vision-Guided Aerospace Part Assembly

Unlike many of today’s manufacturing sectors, the aerospace industry tends to stray away from automation. While automated machinery is commonly found on the aerospace factory floor, robotic arms are a rare sight due to low production volumes and the delicate nature of creating such specialized parts.

This aerospace part supplier teamed up with Waterloo, Ontario-based integrator SYSTEMATIX to design a cell for installing nutplates, an irregular part with over 200 variations that holds the external skin of the aircraft to the frame. Although this complex application doesn’t necessarily sound like an ideal candidate for automation, high performance Kawasaki robots and 3D vision products cut down cycle times, increased product consistency and decreased manpower for a boost in overall efficiency.

Challenges

• Monotonous and time-consuming process led to low employee retention
• In-depth employee certification and training required
• Frequent inconsistent product quality 

Tough & Tedious Application

There were multiple reasons why the nutplate installation process was chosen for automation. In order to meet strict quality requirements for parts, all employees had to undergo intensive training and certification for each part they produced, and document their work in real time. The monotonous nature of the nutplate installation process also created retention issues for the manufacturer, who struggled to train and staff enough workers to keep up with production goals.

Quality Control

Because of the integral role the nutplate plays in the construction of the aircraft, the height of the nutplate rivets need to be exact. Prior to automation, human operators had to shave the rivets to the exact height needed, due to inconsistent rivet heights. Human error was costing the company time and generated more waste due to added process requirements.

Solution

• Supplier worked with integrator SYSTEMATIX to create one-of-a-kind robotic cell
• Three different Kawasaki R series robot models installed – RS005N, RS010N & RS080N
• Matrox imaging software and LMI locators correctly identify 225 part types

This 39-second-per-nutplate install process begins with an operator loading a cart with one of 225 possible parts, and entering the part number into the human/machine interface (HMI), which relays the job number to the robotic arms and to the programmable logic controller (PLC). The first robot, a Kawasaki RS080N, is equipped with three end-of-arm tools and a scanner on one common frame so no tool changes are required. The RS080N determines the part position by using 3D vision to scan three distinctive part features. Using the collected data, the robot readjusts its head accordingly, making sure the part is aligned on the correct plane.

After the part is aligned, the RS080N robot’s drill head end-of-arm tool (EOAT) grips the part, then drills and countersinks two rivet holes for the nutplate installation. The RS080N then releases the feature and rotates the arm to retrieve the correct rivets out of four possible lengths, and at one of two specific pitches, from the rivet slide tooling.

While the RS080N is retrieving the rivets, the RS010L robot picks up a nutplate, and uses vision cameras to verify that it is the correct nutplate out of 28 possible types. From here, the robot places the rivet on the nutplate locating tool. Cameras perform a vision check before placing the nutplate on the tooling to ensure it is clear to receive a new nutplate.

The robot then places the nutplate on a turntable so the RS005N robot can apply sealant, which is a customer requirement to ensure corrosion resistance by encapsulating the nutplate and rivet combination. The RS005N robot conducts two vision checks at this point in the process: one before the sealant application to verify the proper nutplate location, and another one after application to ensure the sealant was properly applied.  

From here, the turntable rotates so the RS010L can pick up the complete tooling package, which includes the nutplate and nutplate-locating tool. The RS010L robot scans the same three part features that were previously scanned by the RS080N to ensure proper plane alignment for installation, and grips the part at the defined feature. While the RS010L robot holds the part in place, the RS080N robot enters the area and the two heads marry – the RS080N robot’s rivet vacuum head places rivets inside the head of the RS010L robot, which installs the rivets into the part.

Once the rivets have been installed, the RS080N pulls back and the robot heads separate. The RS010L safely releases the part and rotates to drop off the dirty tooling, and the RS080N rotates the EOAT to the correct position for crimping the rivets, which completes the process.

Traditionally, this application would have been split into several cells. However, due to budget constraints and limited floor space, the entire assembly process was condensed into one cell. Initially this seemed undesirable, but the compact design of this cell produces a fully completed nutplate without work-in-progress stations, which ultimately would have slowed down production.

Integrator Support

Because robotics are used so infrequently in aerospace manufacturing, the supplier teamed up with an integrator, SYSTEMATIX. They helped design an adaptable, long-term solution that could meet cycle time requirements while identifying irregular part types in a multitude of configurations. To tackle this multifaceted project, SYSTEMATIX’s vision expert used a complex, curved part to develop and test the robot sequences for locating multiple installation points. Then, the drilling and riveting tools were added.

Vision, Precision & Speed

Throughout this complex process, you likely noticed a common theme: the importance of 3D vision.  Matrox imaging software and LMI locators play a vital role in this application, which requires robots to correctly identify 225 part styles, 28 different possible nut plate configurations, all of which can be installed at two different pitches. The supplier chose Kawasaki robots because of the open architecture and ability to handle more advanced processes.

“I’ve touched almost every robotic arm out there... One reason I like Kawasaki is the ease of working with the programs, especially the AS Language,” P.J. said. “It’s one of the driving forces why we use Kawasaki.”

One of many unique aspects of this application is how closely the robots work together. The heads of the RS080N and the RS010L robots have to connect without colliding – an action that wouldn’t be possible without highly repeatable and reliable robots. Kawasaki’s R series of general purpose robots fit this criteria, with repeatability ranging from ±0.02 mm to ±0.06 mm as payload increases (3 kg to 80 kg).

“The arms are very robust; they don’t wander,” project leader P.J. said. “The arms have to go to some very exact positioning, and we’ve not had a single issue with that. They’re very precise.”

When developing this system, SYSTEMATIX leveraged Kawasaki’s hardware and software safety option, Cubic-S, to ensure the robot heads didn’t collide while installing the rivets. Using this software the integrator created zones for the robots to avoid, which prevented crashes with fencing or other equipment.

The high-speed capabilities of these robots also helped the supplier increase throughput. The lightweight arm along with high-output, high-revolution motors provide industry leading acceleration and high-speed operation. The acceleration rate automatically adjusts to suit the payload and robot posture to deliver optimum performance and the shortest cycle times.

Results

• Cycle time reduced by 26 seconds
• 97% consistency achieved
• Number of operators reduced from 3 to 1
• Cell creates fully completed part– no work-in-progress stations needed

Since installation, the supplier has experienced the benefits of automation firsthand. Drastically shortened cycle times, increased product consistency and reduced manpower helped them reach the cost reduction and increased production goals they had set from the beginning.

Automation has also streamlined the nutplate assembly process by eliminating Alodining. When the rivets were shaved by hand, operators had to apply Alodine^®, a chemical film that prevents aluminum corrosion, in order to protect the parts. Now, the supplier no longer has to take the time to apply the material, and the amount of Alodine^® they have to purchase is reduced.

But when asked where they’ve seen the biggest improvement, P.J. cited consistency without hesitation. After being in production for just over one year, the cell has virtually eliminated part inconsistencies. They have achieved 97% consistency – a statistic that greatly affects their bottom line through both cost and time savings.

“Now we’re increasing our production time with (the robot cell)… It’s operating 24 hours a day now and we’re relying on it to get the production numbers we need,” P.J. said. “The reality is we’re relying on the robotic cell – it’s the main part of the process now.”