Small Assembly Robots with Big Gains
| By: Tanya M. Anandan, Contributing Editor
Our electronics are shrinking. Products are more customized. Product lifecycles are getting shorter. And labor is harder to find and more expensive. So what’s a manufacturer to do?
Take a closer look at flexible automation. Robots are getter cheaper, smaller, more precise, and easier to use. Your choices are expanding: Six-axis, SCARA, delta robots, or new dual-arms – they all have their advantages. They see, feel, grasp and assemble small components with confidence. Whether it’s in small spaces or clean rooms, big places or SMBs, in the 3C market, cosmetics, energy, auto or life sciences, small parts robotic assembly is on the rise.
Hard Automation vs. Flexible Automation
Hard automation, or fixed automation, involves equipment designed to accomplish a specific task, such as CNC milling. Flexible automation capitalizes on robots designed to achieve multiple tasks and lends itself to repurposing when your needs change.
“The return on investment is much greater than on any type of hard automation, because you can just create a new tool and put it on the end of the robot and you’re doing something completely different for another part,” says Alex Bonaire, Robotics Product Manager for Mitsubishi Electric Automation, Inc. in Vernon Hills, Illinois. “If you had a piece of hard automation, it can only pretty much do one thing and then you have to replace it.
“These days with the products being updated so frequently, every six months a new version of a television or a phone comes out,” says Bonaire, “think about all of the hard automation you would have to replace on a regular basis to support that. It’s very costly.”
We’re used to seeing flexible robotic automation on the automotive assembly line, moving large components around, positioning, welding, and painting them. But robots are also adept at small parts assembly.
“Many people think of using robots for the down and dirty, rough, big parts, or simple pick-and-place applications, picking it up from point A and dropping it off at point B,” says Bonaire. “But this is really where robots shine, putting things together that are very intricate and complex.
“If you pull out your phone and look at it, that’s a very complex piece of electronics,” he continues. “Even though some of that assembly is being done by hand, the designs are getting more complex and more intricate to where it isn’t reasonable and perhaps not even possible to do by human hands.
“With robots, you have a multifunction assembly tool. So one day it can be putting screws into a circuit board, and the next day or even in the same process, the robot can be doing inspection or some type of dispensing or finishing. It’s a Swiss army knife.”
This video demonstrates assembly of a thermal relay for industrial electronics. Three Mitsubishi RV-series six-axis robots use force sensing, vision, and interchangeable gripper fingers to assemble components.
At 0:13 seconds into the video, you see an arm-mounted Cognex camera with 2D vision to locate a component on the blue pallet and pick it up for insertion. At 0:27 seconds, you see a close-up of the robot gripper inserting the contactor into the housing of the thermal relay.
Force Sensing for Accurate Part Insertion
An integrated force sensor, also supplied by Mitsubishi and located between the robot arm and the gripper, is used to properly insert the contactor into the thermal relay housing. The sensor provides force feedback to the robot based on whether there is resistance during part positioning.
“With the force sensor it can execute a search routine to find out where there’s less resistance, and then based on that feedback, do a clean insertion without damaging anything,” explains Bonaire. “The programming is very simple. It’s looking for a threshold and once it hits that, it stops and tries something else. It just loops and loops until a threshold is reached.”
Once the contactor is properly inserted in the thermal relay housing, hard automation is used to change the orientation of the thermal relay body so it’s perpendicular. Then a second robot swoops in to insert the guard, or internal cover, that separates the different contact points. Bonaire says 2D vision is used in the cover insertion as well.
Servos for Variable Gripping
The servo gripper used in this application demo is also provided by Mitsubishi for plug-and-play convenience. Servo grippers are more common in small parts assembly, because they can open and close at various positions, accommodating differently sized and shaped parts.
“The other advantage of the servo gripper in small parts assembly aside from being very flexible due to the ability to adjust its stroke is that it also allows you to adjust the amount of grip force applied, so small parts can be handled without breakage,” says Bonaire. “When you’re picking up a very small piece of plastic, you need to make sure you’re not crushing it.”
Servo grippers provide an almost infinite range of positioning options. End-of-arm tooling manufacturers such as SCHUNK, Applied Robotics, and Robotiq also offer servo gripping solutions.
For more on smart EOAT, see the Latest Trends in Intelligent Robot End-of-Arm Tooling.
Mitsubishi’s servo gripper isn’t the only flexible solution. At 0:45 seconds into the video, you see a third robot swapping out its gripper fingers.
“We have four different sets of gripper fingers in there,” says Bonaire. “The fixture allows the robot end-of-arm tooling to interchange gripper fingers based on the task that it needs to perform. It picks up the right tool for the job.”
After the finger swap, the video continues with additional demonstrations of intricate assembly made possible with vision capabilities and advanced software.
3D Vision for Random Bin Picking
This robotic manufacturing video shows a similar small parts assembly process for circuit breakers, a real-world application at Mitsubishi’s manufacturing facility in Japan. Force sensing, vision, and other advanced technologies are featured throughout the video.
At 1:37 you see 2D vision highlighted, showing how the robot-mounted Cognex cameras are used for accurate part location and placement. At 1:54, the video highlights 3D vision used for bin picking. If you watch closely, you will see multiple bins of different parts. Guided by Mitsubishi’s 3D vision system, the robot picks parts in random orientations from the bins.
“The gray box attached to the robot arm with the Mitsubishi logo on it is part of the 3D vision system,” explains Bonaire. “Our system is a structured light 3D system where it uses a 2D camera and projects a series of patterns to determine where surfaces are, so that box is a mini projector.”
He says the 3D vision capability replaces a bowl feeder or vibratory feeder, or any traditional type of feeding system for part isolation.
“You don’t have to design, engineer, and build the feeding system,” says Bonaire. “You basically just present the parts to the robot and it will find them regardless of the orientation. With the vision, you can locate multiple parts with one system (as opposed to requiring four or five different bowl feeders).”
Cooperative Control and Interference Avoidance
The old adage that two hands are better than one holds true for robots, too. Cooperative control, also called coordinated motion, is demonstrated at 2:28 into the Mitsubishi video. Although this technology has been around for a solid decade, Bonaire says they are using it more often as applications call for it and end users discover its capabilities.
“If you know that you have the ability to take two robots and have them work together easily, then that can change your entire design,” he says. “Rather than have one robot do something to a part, set it down, and then have the next robot pick it up and do something separately, cooperative motion is more efficient.
“You can hand off parts between robots,” continues Bonaire. “You can also pick a part and then reorient it in real time while another robot is simultaneously executing some other task to the same part. It’s like using a Rubik’s Cube, turning one side while your other hand turns the other side. You can do more in a shorter amount of time. Also, if there’s a part that might be too large, they can both work together to pick it up.”
Bonaire says interference avoidance also helps make assembly processes more efficient.
“Traditionally, you had to program some type of handshaking routine in the robot code, where the robot says it’s at a particular location in space and then it sends out information to the adjacent robots to make sure they do not enter that workspace,” he explains. “That slows things down because the robot ends up waiting.
“With this interference avoidance function, it takes care of all of that automatically by establishing a reference of one robot to the next,” he continues. “Even though you can do it with traditional programming, it would be very difficult and time-consuming to create code that would do it as quickly.”
With interference avoidance technology, rather than waiting for one robot to talk to another robot, they act more like one machine.
How about one machine with two arms? Designed especially for the consumer electronics industry with a unique form factor and collaborative features for working side-by-side with its human coworkers, it’s ABB Robotics’ YuMi. See it in action.
All-in-One Control for Seamless Integration
Speaking of one machine, Mitsubishi’s iQ Platform not only speeds up the assembly process by reducing cycle time, it also shortens project lead time.
“We are the only company that has the ability to have direct robot control on the PLC rack all from the same manufacturer,” says Bonaire. “It reduces cycle time because there is less time spent communicating back and forth. You take advantage of everything being on a high-speed bus, but it also allows system integrators and customers to get up and running a lot faster because they don’t have to spend time figuring out how to get the robot to work with all the different automation hardware. Whether it’s I/O, network, even HMI screens, there’s very little setup.
“It also gives you the option to program the robot with ladder logic instead of just robot code,” adds Bonaire. “You have the option to do either.”
That’s the key to flexible automation. With robots, you always have options.
Robotic Assembly in Life Sci
As the North American Robotics Market Sets New Records in the First Half of 2015, it’s no surprise automation integrators see the demand firsthand.
“Over the last 10 years, we’ve seen at least 80 percent of our applications involve some form of robotics, whether it’s one or multiple robots,” says Marc Freedman, Owner and President of Dynamic Automation in Simi Valley, California. “And in the last five years, the increase was almost exponential. The majority of our work is done in the life sciences industry and the majority is assembly. These are components that you can usually hold in your hand.”
Established in 1986, Dynamic Automation is a preferred integrator for DENSO Robotics, FANUC and Stäubli, and works with other leading robot suppliers. The integrator also serves the energy, aerospace and automotive industries.
“Right now I have 15 different models of robots on my factory floor. They vary from a delta robot assembling pregnancy test kits to a 165-kg six-axis robot moving gears for an automotive application.”
Freedman says customers are coming to them asking for robotics.
“For example, the pregnancy test kit assembly machine that we’re building is the fifth generation. The other four generations don’t have any robotics on them. This is going multiple times faster and it’s a whole different technology we’re using. And we should be at this level. They are a very forward-thinking company and they continue to push us.
“In life sciences we could be coiling tubing and attaching an end fitting to it, or we could be building a very sophisticated test to detect HIV in the fields of Africa,” says Freedman. “Every day is different and then every application is different. The rates can vary from 30 parts a minute to 300 parts per minute. Historically for us, we’ve been using a lot of SCARAs.”
SCARAs vs. Six-Axis Robots
SCARA, which stands for Selective Compliance Assembly Robot Arm, is a four-axis robot commonly used in small parts assembly, where they excel at high-speed pick and place. SCARAs are typically less expensive than six-axis robots. There are fewer axes, fewer motors, and fewer components. But they’re not as dexterous as their vertically articulated cousins.
This video shows an Adept Cobra SCARA robot assembling small consumer brushes in a three-stage assembly process.
Credited for their greater dexterity and application flexibility, six-axis robots are growing in popularity in small parts assembly applications. (This article shows how delta robots are no slouches when it comes to small parts assembly, either.)
“As the six-axis robots have gotten smaller and more cost effective, we’ve been using more of those when we can,” says Freedman. “Our customers want to have the ability to change on the fly like everyone else. They want to have that versatility for the future.”
But sometimes space is a limiting factor. Freedman says floor space is of paramount importance to his typical customer base.
“We’re building cells on one chassis, on one table frame, or a few table frames that are all combined,” he explains. “Space and the landscape, and the ability to put everything in a small envelope, is very important. A lot of our equipment goes into clean rooms.
“One of the foremost things on our customers’ minds is the cost of the space in the clean room,” says Freedman. “Clean room space costs a lot of money to maintain, the HVAC requirements and all the cleaning requirements, so they are very conscientious about the footprint. We’re constantly trying to shrink all of those footprints. We’re trying to push all the robot vendors to shrink their platforms as well.”
In the Clean Room Space
One of Dynamic Automation’s clean room applications involves the robotic assembly of a reconstitution device that makes hemophilia factor therapy easier and faster for patients and caregivers. The reconstitution kit made by Baxter, now Baxalta after a division spinoff, helps quickly administer the drug into the patient’s system to aid with blood coagulation.
“It’s a three-part assembly with three major components: a drug, the device itself, and then a water vial,” explains Freedman. “The drug needs to be mixed with the water and then injected, so this device automatically reconstitutes the water and the drug in the appropriate ratio. It’s done very quickly and it’s very simple.
“It’s nice when we get to do something like this that has value added to society. We’ve done a number of applications like that, for example, some very complicated assembly devices for companies involved with the Bill and Melinda Gates Foundation for funding projects associated with world health.
“The metric that some of our customers use to track how we’re doing relative to our goals is how many lives have we saved or how many lives will we save, as opposed to how many parts are we putting out each month. It brings you a whole different perspective.”
Nevertheless, throughput is still important when you’re saving lives. Three DENSO HS series SCARA robots were chosen for this application because of their high speed to accommodate the 1,800 parts per hour machine rate.
“Accuracy is always a challenge for us,” says Freedman. “For these applications that may require just plus or minus one thousands of an inch, or we’re into microns, we need really accurate robots. For our specific applications, we’ve found that SCARAs provide more accuracy than comparably sized six-axis arms.
“It’s very important that we assemble the components in a way that won’t impact the seal and the integrity of the product. It has to be sterile when the person opens the kit. There’s a vial on one side of the device and a vial on the other side, and there’s a very sharp device that will pierce through the vials. During the assembly process, we need to be very close to that assembly, but we need to make sure we don’t pierce through it. We’re using servo actuators to do all that and force feedback to confirm it.”
Force Feedback, Vision for Delicate Assemblies
Load cell assembly force monitoring uses force sensors to track the entire assembly process to make sure they don’t exceed the maximum force.
“Glass vials can be very challenging,” explains Freedman. “Each one of those glass vials has totally different dimensional characteristics. The grippers are designed for clean room environments and have very specific dimensional tolerances. They come in on each side of the vial’s neck. We need to make sure we don’t scratch or crush the vial, but accurately grip it and have a strong and secure enough grip that it won’t change when we’re moving very rapidly at full speed.”
Vision technology plays an integral role in this medical device assembly application, as it does in many of Dynamic Automation’s builds.
“Many times the trays that these kinds of products come in are intended for one-time use, because the customers don’t want to spend a lot of money on them. They are molded parts, so the tolerances are too great for us to assume the vials are in the expected location for gripper engagement. That’s why we use a vision system to locate the product (in this case, the vial).
“The more DENSO and, in this case, Cognex communicate, and the more transparent and user friendly the technology is, not just for the integrator but also the customer, the better it is for the industry,” says Freedman. “I would say in our robotics applications, more than 50 percent have integrated vision. And that trend is continuing to increase.”
Coupled with robotic automation, vision is often used for inspection. In this video, see how nimble assembly robots, advanced vision capabilities, and expert integration improve machine cycle time.
Solar PV Assembly
Vision also plays an important role in an assembly machine for concentrated photovoltaic (CPV) equipment. Freedman says DENSO HS series SCARA robots were selected for this application due to their high- precision assembly, integrated Cognex vision guidance, and space-saving footprint.
“Originally, we had considered building custom Cartesian-style robotics for this application,” says Freedman, “but after a detailed cost analysis, using off-the-shelf SCARA robots not only saved us money, but also provided increased flexibility with less landscape required.”
The assembly components consist of a heat sink with a highly concentrated solar photovoltaic cell on top of it, the same technology on the cells used in space. On top of the cell is a glass magnifying piece to concentrate the solar light into the cell.
Built for CPV manufacturer Emcore, the full assembly line comprises three machines totaling 30 feet in length, each with rotary indexing dial plates, and a total of 12 SCARAs. The robots are dispensing a two-part adhesive to bond the cell and the glass magnifying piece. Vision guidance is used to accurately place the glass magnifier onto the solar photovoltaic cell for bonding. Electrical wires are stripped, pressed, and then welded to the substrate. Covers are riveted over the wires.
“There’s a lot of collision control programming that had to take place,” says Freedman. “Sometimes up to three robots were working in the same working envelope because they are all tightly positioned.”
Small parts assembly isn’t the only game in town. Freedman says they’re getting more involved in robotic automotive applications as West Coast companies set their sights on the auto industry.
“We’re handling much larger components and it involves more robotic safety,” he says. “One of the reasons we joined RIA is because we want to stay in tune with these ever-changing safety requirements. And our customers are requiring us to know these things. We’re constantly working with our customers and trying to educate them as well. A lot of our customers, the life science guys, they don’t have that long history of robotics. So they are just getting involved.”
Small Parts Assembly for SMBs
Like the life sciences industry, small and medium-sized businesses are starting to recognize the competitive advantage of robotic automation. For many, small parts assembly is in their wheelhouse and they need another SMB that understands their needs.
“We really focus on small automation,” says Ryan Guthrie, Executive Vice President of TM Robotics in Elk Grove Village, Illinois. “Our largest robot is only a 1.2-meter arm length.”
TM Robotics is in partnership with Toshiba Machine. The company markets and distributes Toshiba robots and works with systems integrators in territories outside of Asia.
“We’re focusing on the small parts, the pistons and buttons,” explains Guthrie. “We’re focusing on all the little elements that come together in larger assemblies. Small parts assembly, that’s where your local manufacturing is, that’s your mom-and-pop shop. It’s the small and medium-sized companies that are using these small and medium-sized robots.”
Guthrie describes a small parts assembly application for a leading European manufacturer of automotive electrical accessories. The ongoing application involves assembly of button clusters for auto interiors.
“Whether it be adjusting the heat in your BMW, or adjusting the mirror on your Ferrari, if it’s a button you press in your car, they probably assemble it.”
More Flexibility, Less Floor Space
New to robotics just a few years ago, the customer was assembling these automotive button clusters using hard automation. Guthrie explains.
“In a traditional automotive setting you might have a 15 or 20-station assembly line where each station would do a specific task. Station 1 puts the button in place, station 2 clicks it down, station 3 puts the appliqué on, station 4 puts the second button on, and it does this multi-step process.
“Instead of having all these different linear actuators, pneumatics, and hydraulic components to try to build bespoke machines,” continues Guthrie, “our customer standardized on one of our micro SCARA robots and then just changed the end-of-arm tooling at each station. They’re able to achieve multiple tasks with one robot. Instead of having 14 or 15 stations, they’ve got eight stations (with one robot each) assembled in a circle instead of linear, so it’s more compact for factory floor space.
“There are fewer stations overall, but then it still allows them to do the complexity of the different button consoles,” he adds. “Once they’re done with that particular product line, they retool the arms and they’re ready to go for the next batch.”
TM Robotics’ customer is using Toshiba TH180 four-axis robots for this application.
“We call it our micro SCARA with a 180-mm arm length and 2-kilo payload,” explains Guthrie. “It was selected because of its overall small size. They are trying to do a lot of assembly in a very compact space. They didn’t have room for the traditional small SCARAs that are used in assembly. They have a corner in a shop. So the small size of the robot, as well as the small size of the controller, allowed them to keep the overall footprint very small. They are able to fit eight robots in a space that’s about 6 ft by 6 ft by 6 ft tall.”
Intelligent end-of-arm tooling helps accomplish more with less. Less equipment, less floor space, more tasks per robot. In the auto button cluster application, TM Robotics takes full advantage of double-duty grippers, or in this case, triple-duty.
“One station might involve inserting the little rubber membrane behind the push button and then putting the plastic button over the top, and then they have to do that for three different buttons,” explains Guthrie. “They can do multiple picks and places with one robot because you can put multiple grippers on the robot itself. It’s capable of going to three different bowl feeders and grabbing part A, part B and part C, and bringing them all together onto that workstation. “
This video of a demo cell for a motor assembly shows a robot with a multifunction tool comprising three different tool assemblies capable of doing multiple tasks. In hard automation, Guthrie says that would have been three or four separate machines.
One of the key advantages of flexible robotic assembly is the ability to retool your robots for a fraction of the cost versus replacing entire machines when you’re using hard automation. Referencing again the button cluster application, Guthrie explains how his customer keeps step with the rapid pace of model changes in the automotive industry.
“By replacing hard automation with robots, once the project is complete it allows them to do a complete retool without having to re-engineer all the moving parts. All they’re doing is maybe changing the fingers on a gripper, or they’re changing the program on the robot. So instead of it coming from the left, maybe it comes from the right, or they pick two parts instead of one to do the assembly process.
“Robot automation gives them the flexibility to do all those different parts, whether it’s exotic material handling for some of the high-end cars, or your standard Ford Focus stereo controls, and everything in between. The robot gives them that flexibility.”
He says the product lifecycle changeover is about every 18 months. His customer typically retools their robot arms at these intervals.
“They’re able to achieve a completely new product range using the same capital investment from the first product range. So it keeps their costs down overall.”
“In most of the cases, they’re using standard off-the-shelf pneumatic actuators, whether it’s a parallel gripper or a three-jaw chuck-style gripper,” says Guthrie. “Because they have in-house engineering, they’re able to custom design fingers that work for each of their products. When you’re looking at retooling an application after a certain product group is finished, you’re talking about a few hundred dollars worth of materials versus thousands or hundreds of thousands of dollars (to replace outmoded hard automation).
“It’s often just two or three screws and the finger comes off, and you put a new one on.”
Vision for Precision
Guthrie says inspection is a critical step in the assembly process. The cell uses machine vision to ensure that part quality and tolerances are met.
“These are the shiny knobs and buttons that people see in the car, so they want to make sure that there are no blemishes. Each part undergoes full inspection before it leaves the assembly machine.”
He says in cases where tolerances are particularly tight, the customer also uses vision to verify part placement. Even if a part is slightly crooked in a jig, the robot can adjust its coordinates on the fly. Guthrie challenges any human to the submillimeter accuracy achieved by these robots.
“Take the button in your car that you might use to lower your window on a sunny day. The button that you’re touching doesn’t actually contact the electrical mechanism that makes the window work. There’s generally a plunger in between, which protects the electrical circuit. That plunger is the size of a pencil tip. In this particular application, they’re putting six to eight of these plungers into an assembly in 5 seconds.
“A well-trained assembly technician might be able to keep up with a robot in short bursts, but to be able to keep up that speed throughout an entire shift, and in this case throughout three shifts, it’s just not humanly possible,” says Guthrie. “In a lot of cases, they’re doing less than 5 seconds per station, so they’re pushing out tons of parts. And they are running 24/7. You would have to be a robot to do that (pun intended).”
Guthrie says the application’s return on investment was evident before the first robot was installed.
“Every 18 months they basically had to re-engineer a complete machine any time there was new product that came through. It’s really hard to recycle the components from hard automation.
“Where with robotic automation, they pull the robot off of base number 1 and put it on base number 2, put a new tool on it, and they’re done,” continue Guthrie. “The outright cost might be more, but it’s a one-time cost. After one product change, these robots paid for themselves. Then they’re able to continue making parts for a much lower bottom line.
“Now you also have a lot less engineering time. You’re not designing all these bespoke elements for each product, so it helps reduce the overall cost of production.”
Guthrie says his customer was surprised to discover that the robots weren’t as complex to program as they had feared.
“They actually become incredibly proficient with the machines in a very short period of time, which allowed them to really utilize them to their full capability. I think we had a two-day training session and that’s all it took for them to hit the ground running.
“They are also very happy with the lack of maintenance required to keep them running,” adds Guthrie. “Their preventative maintenance schedules have become much simpler by using the robots versus hard automation.”
Clean, Consistent Assembly
Robotic assembly takes on a whole new importance in processes prone to contamination, such as in the personal care consumables market. In another TM Robotics application, robots replaced manual assembly in the cosmetics industry.
This video shows multiple assembly processes for mascara products at one of TM Robotics customers in France. Tubes, brushes and caps are assembled and palletized/depalletized in various stations using SCARA robots and clever conveyor systems. Guthrie says one of the biggest advantages of robotic automation in this application was repeatability.
“It was a process that previously was done manually. In that case, you always have that chance of human error, whether it’s putting a piece in backwards or upside down, or not paying attention and missing a piece. As they’re trying to do so many parts per hour, it’s inevitable that a human can get distracted. Robots don’t get distracted.”
Cleanliness is another important advantage in the personal care industry.
“A human is not necessarily the most hygienic creature on Earth,” says Guthrie. “We sneeze, we cough. With the advances in electronics and the superior quality of the internal elements, robots are very clean machines. They lend themselves very nicely to the food, pharmaceutical and medical industries, where cleanliness is a requirement.”
Learn more about these clean machines in Robot–Scientist Collaboration (and Separation) in Lab Automation.
In any small parts assembly application, robots can’t do it alone. Vision and other kinds of sensors, software and end-of-arm tooling make it possible. Even hard automation plays a role in the overall solution.
“The robot is just one element of these multiple subsystems that come together to make an automated system,” says Guthrie. “On their own, each of these individual components can’t do much, but when working together and pairing up with robots and bowl feeders, to gripper systems, to conveyor systems and indexers, you’re able to put together this complex machine that’s able to achieve amazing things.”
For more amazing applications, check out Robotic Assembly: Shrinking Footprint, Expanding Market.
RIA Members featured in this article:
Mitsubishi Electric Automation, Inc.