Material handling is one of the most labor-intensive and expensive aspects of manufacturing. Assembling a pair of Nikes, for example, requires up to 40 pieces of material to be stacked and heated to create the shoe upper, which is the flexible part that sits on top of your foot. It can take a human worker up to 20 minutes to arrange those materials.
A Silicon Valley-based startup is helping Nike assemble shoe uppers more than 20 times faster than humans. Using Grabit‘s electroadhesion-based robotic grippers, Nike can now manufacture its shoe uppers in as little as 50 seconds.
Over the course of an eight-hour shift, Grabit’s Stackit robots can help make 300-600 pairs of Nikes. At this pace, Nike’s return on investment (ROI) would be two years. The robots reportedly cost $100,000 each. Grabit customers pay a fee for the software and have to periodically replace the electroadhesive pads.
Nike is a firm believer in Grabit’s technology. The sneaker giant not only acquired a minority stake in Grabit in 2013, it is installing about a dozen Stackit robots throughout factories in Mexico and China.
Grabit says the apparel industry is a $200-$300 million market for robotics makers. This article examines Grabit’s technology and how it found the perfect robot arm for its grippers.
Grabit’s Stackit robots don’t mimic human grasping
Electroadhesion is the static electricity that makes your hair stand up when you rub it against a balloon. It’s apparently adept at helping robots grasp objects in a novel way.
Unlike many of today’s robots, Grabit doesn’t try to mimic human grasping techniques. Instead, it uses static electricity. The grippers use a flat pad of electrodes that create an electric field that adheres to most surfaces. This allows the grippers to pick up objects.
Grabit says its technology is capable of handling an egg, soft fabric, or a 50-pound box. Greg Miller, Grabit’s CEO, says electroadhesion enables it to do things robot grasping companies that use human-like techniques are unlikely to ever accomplish.
Grabit’s search for the perfect robot arm
Before the Stackit robots could assist a company’s manufacturing process, Grabit had to find the perfect robot arm for its electroadhesion grippers. Grabit was intrigued by a Japanese circuit board manufacturer that mounted one of its grippers onto a Toshiba Machine robot. But despite initial excitement, the Toshiba robot did not meet the requirements.
“Choosing the wrong robot could have a detrimental effect on the entire design of the system,” explained Miller. “Two members of our team already had extensive experience in robot design, and both had been involved in the development of several SCARA robots. This prior understanding of industrial robots enabled us to fine tune our requirements before approaching any manufacturers.”
After selecting a handful of potential robot manufacturers, including Toshiba Machine, Grabit planned an extensive test and selection procedure to examine the potential of each one.
“The process looked at several factors,” said Harsha Prahlad, Grabit’s co-founder and chief technology and products officer. “Because of the vast applications for Stackit, we needed a robot with a large reach, that would not lose the high levels of precision needed for exacting material handling applications like the shoes from Nike. What’s more, because Grabit’s electroadhesion gripper is so large, the robot needed to be able to withstand a big moment of inertia and offer the ability to rotate accurately.”
Finding a customizable robot at a competitive price point proved difficult, but manufacturing in the footwear and apparel industry is driven by costs. Combined with the further financial pressure of low labor rates in many manufacturing countries, Grabit needed a cost-effective robot.
“Meeting Stackit’s ‘twenty times faster’ productivity goals rely heavily on the inertia of the gripper and ensuring that the settling time of the robot remained accurate. But the robot also needs to move fast enough to provide customers with the cycle times we wanted,” explained Prahlad. “It became plainly obvious that there was no standard robot that could meet every one of our requirements.”
Grabit uses a modified Toshiba Machine THL1000 SCARA robot
Grabit choose a modified Toshiba Machine’s THL1000 SCARA robot, a horizontal multi-joint machine with four controlled axes. The THL1000 has a reach of 39.3 inches and allowable moment of 0.2kg/m2. And because it uses absolute encoders, the robots’ repeatability in X-Y is 0.01mm.
The robot offers a maximum payload of 22 pounds against a total mass of 81.5 pounds. With a tested load of 2kg, the machine can achieve a cycle time of just 0.48 seconds.
“Grabit’s electroadhesion technology was not only impressive, but innovative enough that we were keen to get involved,” explained Nigel Smith, CEO of TM Robotics, which is Toshiba Machine’s American and European distributor. “Grabit’s experts knew exactly what they needed, and our close collaboration led to an insightful process of experimenting and fine tuning the capabilities of our existing Toshiba Machine robots.”
Building a custom transmission
Grabit’s requirements were unusual. Unlike many robotics applications, there was no need for a lot of complex motion. Grabit did not require the range of movement provided by a standard, six-axis robot.
Grabit also wanted to use its own control system. So it needed deep access to low-level internal control code, and the control package needed to be small enough to fit into a tight design.
Following some adjustments, the Toshiba robot was still not stabilizing fast enough. Due to the inertia of the gripper, followed by the time taken for the gripper to rotate and the robot to settle and stabilize, it was unable to hit the cycle times the company had targeted.
To hit Grabit’s desired cycle time of 0.48 seconds, TM Robotics actually built a special transmission for the system.
“TM Robotics’ support and customization process was not limited to phone calls and e-mails,” explained Prahlad. “Working in collaboration with Grabit’s knowledgeable robot engineers, they were able to talk to us in a language our technical team understands and allowed us to fine tune the machine to our exact requirements – not many robot companies allow for that level of personalization.”