Robotic automation has long helped aerospace, automotive, and electronics OEMs cut their manufacturing costs. Yet, by one estimate, only about 5% of the U.S. medical manufacturing industry is exploiting the technology. Phil Baratti, manager applications engineering at Epson Robots, Carson, Calif., (robots.epson.com), says many medical designers continue working with conventional assembly ideas and have not advanced to building on design-for-automated-assembly principles. However, this should change as recent improvements to robotic technology let even small and mid-sized firms cut costs assembling, inspecting, transferring, and packaging parts such as stents, shunts, and catheters.

Current robotic systems that target medical manufacturing conform to industry requirements such as CFR Part 11. And because robots can perform more precise movements than a person, designers can think about building smaller, thinner, and more complex parts. Precise handling comes from PC-based controllers that don't require programming with complex ladder diagrams. The controllers are a logical step because many companies already familiar with using personal computers.

Additionally, the robotic systems let designers simulate and accurately prove-out robotic lines in a virtual world before cutting metal or connecting wire in the real world. This lowers costs, reduces risks, and shortens lead times because such simulation allows determining in advance factors such as cycle time, how many robots are needed, and whether a line will fit in a certain tight space.

Companies can purchase robots directly from their manufacturer or work with an integrator. These firms help select and install the correct robot as well as design, test, and verify programs to run it. Some integrators also build associated packaging equipment and components in the robot's end-of-arm tooling (EOAT).

From gantry to 3D vision

The simplest robots are gantries or Cartesian systems, according to application engineer Mark Handelsman at Fanuc Robotics America Inc., Rochester Hills, Mich., (FANUCrobotics.com). “Gantries have rectangular work envelopes and their their EOAT moves in linear X, Y, and Z directions,“ he says. “Sometimes the units also move along an additional guiderail. Articulated robots, on the other hand, move in a spherical work envelope with a jointed arm that can reach above, below, behind, and in front of parts. The robots usually have four to six axes or joints (sometimes up to twelve), which, starting at the base, are numbered 1 through 6.“ Of course, robotic movement is directed by a program, but it can also be guided by a camera.

Handelsman says a simple example of a robotic system comes from a packaging line in which the robot takes a product from a known location, puts the part in a box, and feeds the box to packaging equipment. “One integrator, ESS Technologies, specializes in packaging medical devices,“ he says. “To build such a system, engineers at the company first import a 3D IGES model of the medical product into the RoboGuide software, along with conveyor, feeder, and packaging-equipment drawings from suppliers,” he adds.

The next step mathematically defines the system frames, which tell the robot where it is with respect to the part and the packaging equipment. Programming the robot is then a simple matter of using a teach pendant to show the robot where to move.

“The software includes a digital version of the teach pendent. Using it tells the digital robot to move one way or another. Hitting Record saves the locations,“ says Handelsman. “Robots can be programmed a few different ways. Users can, for instance, key in just X and Y locations, which is easiest for most. Designers would program the arm to go, say, up 100 mm and over 50 mm and the software takes care of the arm's movement. For the detail oriented, users can also program each robotic joint to move a certain number of degrees. Another option lets users specify pitch, or how far the end of the part moves up or down. They can program yaw, or how far the part moves sideways. Even roll, is programmable.“ Such precise movements might be useful, for instance, to ensure a syringe tip doesn't get caught while putting the device in a tray.

“Our robots have integrated vision for applications in which parts shift as they might in trays, get scattered on conveyors, or are randomly piled on top of each other,“ says Handelsman. “Users would just need to load the optional vision software and hook up a camera directly to the robot's CPU. The camera acts as the robot's eyes. It helps direct the robot by recognizing part patterns.“

Vision systems can be 2D, with one camera, for locating parts placed randomly in a plane, such as on a conveyor. Some Fanuc systems use a camera with a laser to put a red X of light on top of the product. The camera finds the cross, calculates how much it is distorted depending on the part orientation, and from that tells the robot where the part is. This is useful in applications in which parts are loosely stacked or randomly located in bins or boxes.

“In one application, we designed a complete line that assembles and packages a medical device, places it in a blister card, loads multiple cards into a carton and, finally, into a case and onto a pallet,“ says sales and marketing director Walter Langosch at ESS Technologies Inc., Blacksburg, Va., (esstechnologies.com). “The process involves seven robots including several LR-Mate six-axis robots and 16 other pieces of equipment.“

In this assemblage, robots pick parts from a product feeder, and assemble them with other components. The end-of-arm-tooling, which the company designed and built, includes a forced-sensing technology that tells the robot when the product is grasped properly. Another robot picks up items as they travel from one station to the next and passes them in front of a camera for inspection.

Another uses a vision-guidance system to pick up the bottom of a small, oblong plastic housing, assemble components in it, check their location, and then completes the assembly with the other half of the housing.

“Robotic systems such as these can help even small companies compete in a global economy,“ says Langosch. “For instance, one customer ships products to China. The product integrity is so critical that a whole shipment could get returned if just one insert were missing out of 100,000. By checking every one, robotics and vision inspection eliminated this problem.“

Three lines of code

Robot manufacturer Epson also makes several kinds of systems including gantries, articulated arms, and Scara (Selectively Compliant Assembly Robotic Arm) robots. Scaras target high-speed assembly tasks and are especially good for applications requiring some flexibility, such as inserting a round pin in a hole without binding. All the robots have integrated vision and can handle inspection too, according to regional manager Jay Hallberg. “It typically takes only about an hour to set-up a robot and camera, calibrate the system, teach the part, and write a simple program that tells the robot to find the part, pick it up, and place it,“ he says. “Once a vision-controlled system is set-up, operators need know only three lines of code to run it, V-Run, V-Get, and V-Set.“

Document-process control, a frequent requirement for medical devices, is simplified because the robots capture part dimensions in real time and archive them in the PC-based controller, says Hallberg. The controller has an open architecture that lets users add third-party hardware, such as data-collection boards, or software, such as Labview, to interpret data.

One recent application used a vision system with several cameras to find and pick up 0.004-in.-diameter stent wires. “Multiple cameras are necessary because the ends of the wires are often bent. The cameras locate the tips of the wires, letting robots know exactly where to pick them up,“ says Hallberg. “The device manufacturer used to have 22 people in this process. With a robotic system, the company requires only three individuals.“

EOAT: It's more than an end effector

“End effector“ is a generic name for end-of-arm-tooling (EOAT) that robots use to move or assemble parts, says Dan Peretz, director automation product management, De-Sta-Co Inc., Madison Heights, Mich., (destaco.com). “We are standardizing effector components, which we supply to most robotic manufacturers. We don't supply the tooling that actually touches the part because most manufacturers prefer their proprietary designs. That's because the part's dimensions might change several different times while designing the robot system and before the machine is even shipped. And each change affects how tooling, such as fingers, will grab the part.“

Peretz's firm supplies off-the-shelf and customized grippers. The most basic grippers use pneumatics to push and pull a wedge that opens and closes the gripper jaws. A robotic manufacturer or integrator would design the fingers separately. The company also provides linear slides, which let robots grab different sized parts with more dexterity than conventional fingers, and rotaries, rotation devices that turn a gripper from 0 to 180°. Also available are toolchangers, which allow using multiple end effectors on a robot, and compliance devices, which help to align parts during assembly.