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Historically, sealing robots have been used in many applications that require tough ergonomic and environmental conditions. An industrial robot’s design and flexibility offer many advantages over the difficult labor constraints frequently posed to a manual operator. In addition, the perceived high cost factor has been negated due to many automotive OEMs embracing these technologies. Robots, like other computer-based equipment, become more affordable as the installed base grows. With today’s industrial workforce having at least a working knowledge of graphical user interface (GUI), the ability to program and control robots has become more intuitive and user friendly for the novice programmer.
The six-axis robot is a mature, stable product whose primary R&D costs have been well absorbed by the manufacturers and early adopters. Sealing robots are now positioned to help general industrial users increase competitiveness, product quality and workforce safety, all while reducing the environmental impact associated with applying many sealing materials.
Definition and CapabilitiesSealing robot is an industry term for a robot that has additional fluid handling technologies integrated into the robot that differentiate it from all other standard industrial robots. Sealing robots are built with numerous arm configurations so they can easily adapt and access difficult-to-reach areas of the part in question. Designing the robots’ optimal placement with relationship to the part typically yields optimum application results.
When sealing robots were first designed, they only had one function-to apply materials in difficult environments. As acceptance and use expanded, sealing robots grew beyond being a traditional robot with application equipment into a unique subset of industrial robots. Sealing robots now have the ability to control all aspects of application parameters, including air assist, atomization air, multiple fluid flows/guns/equipment, speed-proportional control, and anticipation parameters. To determine if a factory is a good candidate for robotic sealing automation, several limiting factors need to be considered.
Robotic sealing requires a repeatable part presentation window. The part presentation is routinely handled by guiding or trapping a part through mechanical methods. Alternately, robotic vision systems can be used to guide the robot to a nominal location on the part.
Sealing applicators usually require a tip-to-part distance of 5-150 mm. The more accurately a production conveyance presents a part to the robot, the more quality and material savings benefits can be achieved. An industry standard request of part presentation can be assumed at +2 to +75 mm, the latter typically requiring a vision solution. The importance of tolerance varies depending on the required application precision and the cost of sealing (material savings). For most standard applications, a simple pallet pin method part presentation provides enough stability/repeatability to make robotic sealing automation accurate and affordable.
Amount of Dissimilar Parts
Robots are very effective in a variety of sealing systems, from those using only a few parts to those that involve many hundreds of different parts. The primary environment where robots are not as effective is in “job shop” applications. An engineered piece that will be manufactured one time and never again is not a good candidate. Parts that will be manufactured over and over, even with major time gaps (months/years) between runs, can be easily sealed with today’s robotic technology. The robot memory will store part-specific programs indefinitely and call for them when required.
Part Size and Shape
A good rule of thumb is that if a factory operator can seal a part, a robot can seal the same part. In certain applications, however, the size or shape of the part is so unique that both factory operator and robot may struggle to reach all areas that require sealing. For very small parts, the work is often too fine to be done by hand or robot, and another process (e.g., heat cure) will be more effective. For very large parts, the robot might need to be moved via additional track systems and extensions to reach all areas, which is often not viable for smaller industrial operations.
Potential AdvantagesIncreased and more consistent product quality is the most widely regarded advantage gained by robotic automation of all types. For sealing robots, the most complete analysis must be identified by close examination of the production cycle as the quality improvement cascades through the entire production system.
An industry standard assumption is that a material savings of 5-50% can be achieved when manual operations are replaced by automation. This savings is achieved in three primary areas:
- Application geometry accuracies of ± 0.5 mm are common with robotics. If a substrate requires 4 mm diameter, +2 mm/-1 mm and is regularly produced by hand at 5-6 mm, a material “loss” of 20-50% can impact the producer with no knowledge of the additional expense. If the manual operator applies less than the minimum amount (e.g., 3 mm), the part will need to go through system rework or will pass through the system undetected, resulting in a leak or defective part or possibly causing additional warranty claims or damage to the associated operations. It is much more common to see the over-application situation because that generally meets the minimum application requirements, thus resulting in manufacturing compliance.
- Trigger accuracy offers a major quality and savings impact. Industry standards of less than 50 ms trigger time are common. This allows the user to accurately and consistently apply sealer to the part only where it is required for every cycle. When the applicator is repositioning, the material supply trigger is off, eliminating material loss resulting from the sealer being misapplied onto the part.
- Manual cleanup of the part is commonplace when inaccurate, unpredictable practices are in place during the manufacturing process. It is common that automated operations can deliver repeatable results to less than 3% variation.
It is becoming obvious that carbon footprint impact will soon be the baseline for a good community employer, and sealing robots have always been environmentally friendly. In addition to the environmental savings already discussed, increased accuracy enables sealing robots to provide reduced energy requirements. The need for less re-sealing of bad seals, combined with seals that can be achieved more quickly and in one pass, enables the sealing equipment (robot and sealing apparatus) to use less kilowatts per seal.
All savings aside, many sealer application environments are very unfriendly to the personnel who occupy them. PVC contains chemicals (e.g., mercury, dioxins, and phthalates) that are extremely unhealthy, and spraying the same product over and over can also result in a repetitive stress injury. Many employees initially see robots as a threat to their employment. In the case of many sealer chemistry situations, however, the benefits of moving the robot in and the person out far outstrip the disadvantages. In many cases, the employee can be moved to a safer, more rewarding position.
An Effective CombinationThe robot can be a great tool, but it is only a tool. The most common mistake is assuming that the robot is a sealer applications expert. On the contrary, it is only a contributor to the application process. The true expertise comes from competent support staff who keep the robot calibrated and at optimum functionality. With the combination of well-trained staff and maintained robots, along with their applications equipment, it is possible to increase quality and throughput while reducing costs and being a better corporate citizen.
For additional information regarding robotic sealing, contact the author at (248) 391-9000 or Paul.D.Cutean@us.abb.com, or visit www.abb.com/robotics.
Editor’s note: All photos are courtesy of ABB Robotics.