Well, hello Miss Charlotte
The German family firm Pilz is transforming assembly lines with smart controls that allow man and ‘cobot’ to work safely side by side with no safety cages.
• One of the 9,000 workers at BMW’s Spartanburg car factory in South Carolina is known to her colleagues as Miss Charlotte. She is a stocky grey-blue robot, as tall as one of her smaller co-workers. She boasts a highly flexible arm with a small roller on the end. This roller moves at a constant pressure along the sides of a door panel lining no faster than a human being would do it. Thirty seconds later Miss Charlotte has moved to the next car door.
It is significant that the BMW workers have given a name to the robot working beside them on the assembly line. It highlights a profound change. Until recently robots were only accepted in factories if they were securely separated from the human workers by a metal grille. Now robots are no longer things to be afraid of; instead, they have become colleagues. Some of the credit for that is due to the German family firm of Pilz, which calls itself the “safety ambassador”.
Pilz’s headquarters are in Ostfildern near Stuttgart, south-west Germany. The firm has more than 2,200 employees, a turnover of €306m (£270m) in 2016, and 40 subsidiaries around the world. About 70% of its production is exported. It is one of Germany’s unknown world market leaders. Unknown because its products, which include electronic control and monitoring devices, sensors and switches, are only sold to the manufacturers and operators of machines and engineering plant. For the uninitiated, the most visible Pilz product is the safety relay and switchgear PNOZ (Pilz emergency automatic shutdown) installed in control cabinets and triggered by the red emergency buttons prominently attached to countless industrial machines – from assembly lines and packaging machines to printing presses, rollercoasters, wind turbines and stage scenery.
In an emergency the patented device, which has become a generic name around the world, does not simply cut off the electricity supply but brings the machines to a controlled stop so there are no breakages, no load crashes and the machine can be restarted quickly. According to Pilz, PNOZ is the world’s most widely used safety relay. Together with Pilz sensors, light grids, laser scanners, camera and control systems, it has made the company’s name in the safety business.
Pilz was founded in 1948 as a glassblowing workshop, and first made apparatus for medical technology. During the rebuilding of Germany’s factories after the war, the firm turned to control and monitoring components for machines – for example, two-hand controls for presses, to ensure operators keep their hands out of danger when the press is in motion.
Peter Pilz, son of the founder, then moved further into electronics and programmable memory controllers, boosting sales through the firm’s first subsidiaries. When he died in a plane crash in 1975, his wife, Renate, carried on the work – first employing a manager, then taking over herself in 1994 – and this year she has handed the job on, to her daughter and son. It was under Renate Pilz’s management that the number of employees rose to 2,200 and it was she who made sure that Pilz invested nearly 20% of its turnover in research and development and set up its own thinktank for smarter production.
Her work bore fruit, and allowed Pilz to get into the robot sector at an early stage. In 2016, there were an estimated 1.8m robots in factories around the world (including about 200,000 in Germany). That figure is forecast to rise to 3m within two years and Germany is the world’s fifth largest robot market. Most of them are still classic industrial robots, slogging away at high speed and tremendous power in protective cages. But lightweight robots with low load capacity working at human speed are increasingly being used. They can be put to work in the same area as their human colleagues without any safety fencing. The most advanced “cobots” (collaborative robots) can even learn movements if given a demonstration. “It used to be the case that man and machine had to be separated as safely as possible,” says Klaus Stark, head of innovation at Pilz. “Now that principle has been turned on its head. Humans and machines work at the same place and at the same time, just like colleagues.”
The potential for this man-robot collaboration is huge – in nursing care, household cleaning, operating theatres, but initially and above all in the automation of simple assembly work. “The low entry prices and the great media interest in the technology triggered downright hype,” wrote the Fraunhofer Institute for Industrial Engineering (IAO) in a 2016 study on the “initial experiences of user companies” with cobots. It concluded: “The new technology works! But are the new robots really safe?”
The year before a robot had killed a worker at the Volkswagen works in Kassel, north of Frankfurt; while setting up the robot, the young man was trapped by the robotic arm and crushed against a metal plate. The incident hit the headlines, feeding fears that these machines would not only eliminate jobs but might also constitute a deadly danger at work. However, the robot involved was a classic industrial model in a safety cage.
In fact, the number of accidents at work – including fatal ones – has been falling in Germany for more than 20 years. In 2016 there were 424 deaths. According to figures reported by Germany’s statutory accident insurance, in 2015 there were 183 notifiable accidents involving robots, or 304 if robot-like plant is included. These are very low figures compared with nearly 44,000 accidents involving the operation of machines and the figures are minute compared with the total of about 877,000 work-related accidents.
Pilz can claim some of the credit for the improvement. Its products include pressure mats that detect when a person is approaching and slow down or halt the robot; tactile skin membranes that cover the robot arms like a sweater and control its movements when a human approaches; and safety doors that only permit access to people with the requisite smart card. There are also lots of job-specific sensors, camera systems for three-dimensional room surveillance and laser scanners that surround the robot with grids of beams and shut it down if these are broken.
If accidents still happen, despite all the precautions, Stark says it is often because people tempt fate. “You just cannot imagine the lengths people will go to outsmart the safety systems.” It might be to retrieve a dropped tool, to loosen a jammed conveyor belt or simply to save themselves a few extra steps.
Robots must always be made safe around human colleagues. In certain circumstances contact is permitted, for example with classic pick-and-place applications. Otherwise the machine would not be of any real assistance. So robots rated as “incomplete machines” under the EU machinery directive must be turned into “complete machines” by having their safety inspected on site in the factories and when they actually work. Only then are they awarded the CE (Conformité Européenne) label.
That is why Pilz sends its own team to tour factories and enhance the safety of robots made by various manufacturers. The engineers reduce the impact of potential collisions by rounding edges and corners on the robot grippers, fitting padding or enlarging the contact areas. Finally, they take a collision-measuring instrument out of their big plastic cases: with springs of 12 different strengths. The sensors on the apparatus measure the force and pressure the robot might exert on different parts of a person’s body in a collision. A worker may still receive a knock or squeeze, but there should be no pain or injury.
According to Stark, this works well with Miss Charlotte in Spartanburg and with several dozen lightweight robots in BMW’s other factories: in Leipzig they apply glue to windshields; in Dingolfing, southern Bavaria, they insert bevel gears weighing several kilos into gearboxes human employees are working on at the same time – all in a very confined space, all without any protective screens.
However, Stark warns: “Robots can only detect human beings indirectly, despite all the sensors, cameras and other aids. They don’t know if what they have detected is a coat stand, a cardboard box, a shadow or a human hand or head.” That is why there is no solution – or at least no affordable solution – to the question posed by a saw manufacturer who wanted to be sure that fingers would be detected before they met the saw blade. “There is so much dust and debris churned up that at the moment that is technically very complicated.” Frozen meat pushed over saws by human hands encased in gloves for the meat industry poses another tricky problem.
“Safety is often seen as a necessary evil, a tiresome ‘add-on’,” says Stark. And safety technology is not terribly sexy, he admits. Pilz does not send rockets to the moon with the world looking on with open mouths. “But I still see our work as highly ethical, because by taking many small and large steps we protect people – and investments. For engineers, few other things are as meaningful.”-