Robots Are Asked to Do More and to Be Team Players, Too

Robots exhibited at NPE2018 will be faster, smarter, more connected, and, in some cases, more “collaborative.” Interviews with leading robot suppliers showed remarkable unanimity about the overall points of emphasis: new control features to speed cycles, facilitate maintenance, and ease programming; increasing integration of robot and machine controls; and growing industry reliance on automated cells with multiple downstream operations integrated beside the press. This last emphasis is bringing a wider range of robot types to plastics shows—SCARA types, delta or “spider” types, and a growing variety of “collaborative” concepts. Six-axis jointed-arm robots are also likely to be more plentiful than ever at this NPE, but they are facing competition from five-, six-, or seven-axis linear robots sporting servo wrists.

 

Faster, Stronger, Smarter

Robots overall are becoming faster, carrying heavier loads, and are easier to program. More sophisticated programming is shaving every possible fraction of a second off of cycle time by executing multi-axis movements simultaneously, anticipating the movements of the clamp and ejectors, and establishing optimum standby positions. Smarter robot controls can learn and adjust timing and positions for such automatic cycle optimization. On the other side of the coin, some controls actually slow down the robot when the cycle permits, saving wear and tear by ensuring the robot doesn’t move any faster than necessary to get where it is going on time.

The speed, precision, and programmability of servomotors has largely replaced pneumatics on takeout robots—both on the main axes and on wrist rotation. As you’ll see at NPE, servo sprue pickers are also having their day—becoming, in fact, mini robots. One supplier notes that servo pickers offer benefits for controlling orientation of demolded parts. However, there’s general agreement among robot vendors that pneumatics will have a place in simple pick-and-drop applications for some time to come.

The constant pressure to squeeze out higher productivity also means less patience with “flutter” of the robot’s vertical axis due to acceleration, deceleration, and machine shock and vibration. Robot suppliers have worked steadily to reduce mass and increase stiffness of robot arms to minimize inherent vibration tendency. They also use software for active vibration suppression—controlling acceleration/deceleration and using small robot counter-motions to dampen vibration (analogous to noise-canceling headphones).

Ease of programming has been a steady trend (see the Plastics Technology cover story this past November). Some vendors have approached this, in part, by ensuring a consistent interface among all models in their line; another strategy has been to apply a similar look and approach to programming six-axis, jointed-arm robots and linear or Cartesian models.

 

Decoding ‘Industry 4.0’

One thing seems certain: The biggest splash at NPE will come from the wave of technological innovation and futuristic enthusiasm known variously as Industry 4.0 or the Smart Factory or the Internet of Things. That wave has charged across the ocean from Europe, where new protocols for machine-to-machine and machine-to-central-computer communications are being developed under the leadership of the German machinery association, or VDMA.

            Although much of plastics machinery used here comes from Europe, the concept of Industry 4.0 has not achieved the same degree of familiarity on this side of the Atlantic. “Molders here are more at the stage of ‘What is it, and why do I need it?’ They want to know how much change it will bring to their operations, what it will cost, and how they will benefit,” says David Preusse, president of Wittmann Battenfeld, Inc., Torrington, Conn. (wittmann-group.com).

            Jim Healy, v.p. of sales and marketing for Sepro America, Warrendale, Pa. (sepro-america.com), agrees that the banner of Industry 4.0 may fly over many machinery booths, but the attitude of U.S. visitors will be mainly one of curiosity. “They’re on a fact-finding mission to learn about what it means and what it means to them. If Industry 4.0 is about connectivity between machines, then robots have been ‘Industry 4.0’ for years, thanks to standardized control protocols. That connectivity goes several steps further in automation cells that may involve not only a molding machine and a robot, but also insert feeders, secondary robots, complex end-of-arm tooling, in-mold sensors or vision systems, post-mold handling, inspection, finishing, stacking, and packing.”

            Adds Preusse, “Industry 4.0 will likely be the most common theme found at NPE. Companies will illustrate how they are using elements that tie into this new Smart Factories era.” He said these can include:

 

 •  Molding cells with the robot, press, and auxiliaries all connected together;

 •  Mold setup recipes for robots and other auxiliaries stored on the injection machine for faster mold changes;

 •  Web service support;

 •  MES collection of production data;

 •  Smartphone apps to get production status or alerts;

 •  Predictive-maintenance monitoring of cell equipment;

 •  “Smart molding” process solutions;

 •  Production traceability;

 •  Remote access and control.

 

            That’s an awful lot to digest, and Chris Parrillo, national sales manager of Yushin America, Inc., Cranston, R.I. (yushinamerica.com), thinks the best way for molders—especially those from small to mid-sized firms—to approach the topic is to “break it down into manageable chunks.”

            One of those chunks is predictive maintenance, which is an emerging theme that will be sounded by injection machine suppliers and builders of auxiliary equipment. The idea is for a robot “to monitor its own internal systems and detect problems as they develop, so it can warn of a maintenance issue before a catastrophe strikes on a weekend shift,” explains Dino Caparco, Yushin’s engineering operations manager.

Some of early signs of this trend for robots will be appearing at NPE. For example, look for features such as monitoring gripper vacuum levels to warn of leaks or other problems before the robot loses its grip. Other approaches may include vibration sensing and monitoring servomotor torque and amperage load to detect bearing misalignment, insufficient lubrication, damaged rails, and/or fatigue of the robot arm due to repeated flexing.

Another closely related “chunk” of Industry 4.0 is remote monitoring and web-service support. Such features have become increasingly common for molding machines and are now spreading to robots.

Still another related trend under the broad umbrella of Industry 4.0 is varying degrees of integration of robot controls with those of the injection press, which can range from “mirroring” of the robot control interface on the operator panel of the press to actual sharing of data between the robot and press—a more complex issue when different vendors are involved.

 

More Automation = More Capable Robots

Anyone who has attended a major plastics show recently will have noticed that exhibits of a machine standing on its own molding parts have become less common than elaborate automated cell demonstrations involving multiple upstream and downstream operations. This reflects a gradual transition occurring in molding plants. “We’re seeing more beside-the press automation,” says Yushin’s Parrillo. “More inspection, packaging, assembly, and product serialization using hot stamping, laser engraving, barcode labeling, and RFID chips.”

            “We’re seeing more and more being done with takeout robots,” adds Caparco. “That means higher speeds and more complex end-of-arm tooling for jobs like insert molding—or in-mold labeling—combined with part removal.”

            One consequence is that Parrillo and Sepro’s Healy see growing interest in use of machine vision to assist robots. They attribute this to molders’ increased emphasis on quality and to the declining cost and increasing miniaturization of vision components. It thus becomes ever more cost-effective to mount cameras on the mold, machine frame, or the robot in order to check for short shots, color, proper degating, proper insert loading, and complete ejection from all cavities. There is also a growing trend to use vision for 100% inspection of parts for dimensional measurement, label orientation, and surface flaws. As many as 16-18 parameters can be checked at once—on every part.

            Attendees at the last NPE in 2015 will have noted the ability of vision-guided robots to play basketball or miniature golf. In the real world, this translates into ability to locate parts on a conveyor and orient them for stacking and packing. Healy notes that vision applications today typically still rely on custom solutions; the future will almost certainly bring more plug-and-play simplicity. Check out this year’s exhibits—maybe the future isn’t far off.

            In Healy’s view, the trend toward cell automation means you will likely see more six-axis, articulated robots at this year’s NPE. Notwithstanding the extreme versatility of such robots, Healy, Preusse, and Parrillo agree that jointed-arm robots are better applied to downstream functions than to pulling parts out of a mold. As compared with linear robots, they are less attractive in speed, reach, payload capacity, and size of the work envelope that needs guarding—not to mention cost and additional programming effort. On the other hand, they may be advantageous in low-headroom circumstances.

            For the most part, however, Sepro, Wittmann, and Yushin agree that a linear robot with a servo wrist can have five to seven degrees of freedom that compete favorably with jointed-arm types. At NPE, you’re apt to see linear robots operating alone, or in pairs—handing off from one to another—or teaming up with jointed-arm robots for downstream operations. Notes Yushin’s Parrillo, “We are finding more and more molders mounting takeout robots on a floor-standing frame and using them for various tasks outside of the mold, like degating, packing, inspection, and assembly.”

            Downstream cell operations are fertile ground for other kinds of robots that may be less familiar to NPE attendees. One is SCARA robots, a type of very fast, extremely compact device typically used in assembly operations to pick and place small, lightweight parts. They typically have three or four axes of freedom and speeds of up to 200 picks/min. They can access extremely confined spaces. A second type of high-speed, light-duty robot is the “spider,” delta, or parallel robot, which has started appearing with greater frequency at plastics shows. It has three arms connected to universal joints at the base. It can have three to six degrees of freedom and is capable of up to 300 picks/min. Recent show demonstrations have employed these robots to reposition multicavity parts after they have been demolded by a linear robot.

            A newer type of robot that has been gaining attention lately is so-called “collaborative” robots (or “cobots”), which are typically distinguished by modest cost, easy lead-through-teach programmability, and—most important—ability to operate safely around humans without hard guarding (see PT, Feb. ’16 cover story). Typically based on six- or seven-axis, jointed-arm designs (sometimes with two arms on a single base or pedestal), these robots use onboard vision and torque sensors (and sometimes a touch-sensitive skin) to sense unintended contact with a foreign object and react very quickly to halt further movement. They are generally considered suitable for pick-and-place operations downstream of a molding machine, not for machine tending. An ever-growing number of vendors are coming out with such robots, so there may be new entries of this type at NPE. You will almost certainly find new capabilities introduced for this class of robots at the show. (See, for example, PT January Keeping Up.)

            Builders of linear and jointed-arm robots are quick to point out that most cobots are limited in speed and torque for safety around human operators, and also limited payload capacity. On the other hand, molders appreciate the reduced need for hard guarding that hinders maintenance and setup operations.

Makers of conventional robots are responding with new ways to make standard linear and jointed-arm robots more collaborative by adding software and external safety devices, such as laser scanners

or light curtains. When a human approaches within a certain distance, the robot slows down to a fraction of its normal speed; if the human approaches even closer, the robot halts completely. But when the human backs off, the robot automatically resumes first slow-speed motion, and then full speed as the human moves completely outside the safety zone. (See short.ptonline.com/collaborat and PT, March ’17 Close-Up.)