By Christopher Logue, Emerson
This plug-and-play paint automation solution incorporates industrial-grade intelligent devices and industry-standard communication technologies to streamline OEM development of advanced painting and coating robotics systems.
Whether applying the color and clear coats to an automobile or laying down powder coat material used to create a durable equipment protection layer, robotic application systems are a preferred way to efficiently produce quality finishes on a high-performance, mass-production basis. But to make these systems work well, robotic painting OEMs must marry two different and uniquely complex technologies — motion control and paint application — to create an orchestrated solution that is artistic and technically proficient.
Figure 1: Architected with valve, instrumentation, controllers, and other products from the company’s expansive portfolio, this Emerson paint automation solution accelerates OEM efforts to bring high-performance and data-rich painting robots to market.
The paint application portion of this equipment carries a specific and unique set of challenges associated with the pressure and flow of the atomizing air, which must be carefully controlled to avoid overspray, waste, and other undesirable conditions. To avoid re-inventing the wheel, robotic painting OEMs are keen to find packaged solutions offering proven performance for paint application to speed their development cycles and allow them to focus on the already complex motion control tasks associated with robot and part handling.
Incorporating a complete packaged paint application automation solution is one way these OEMs can simplify their design efforts and obtain high-quality results. Even better, when these packaged solutions are based on commercial off-the-shelf (COTS) elements, designers find other benefits, including compact footprints, extensive instrumentation for monitoring operational characteristics, and industry-standard communications connectivity to transmit the information from floor to cloud (Figure 1).
Beyond the broad strokes
Painting is dogged by several challenges, some obvious and some less so. Applying the material in just the right amount to result in an optimal finish, while avoiding overspray, is perhaps the most basic attribute of an effective painting system. Some equipment designers might be tempted to err on the side of delivering too much material to ensure the target part is sufficiently coated, but paint costs money, and some esoteric materials are very expensive.
Overspray is more than just an issue of getting some paint on a part where it is unwanted. Much of the overspray settles out in the painting area, generating what is sometimes called paint sludge. This paint sludge is an environmental issue, and there can be significant costs associated with removing and properly disposing of it. Some estimates based on past projects indicate that 20% to 30% of paint is lost to overspray, and this can be a major issue, for example with painting all parts of a car, which can result in over 3kg of paint sludge per vehicle. Extrapolating this out with sludge treatment costs of over $300 per ton means that worldwide, this one industry may be paying over $100 million to address the issue.
Another consideration for optimizing the paint application process is efficiently managing compressed air usage and quality. Generating, drying, and filtering the volume of compressed air required for painting operations requires significant energy, so minimizing air usage provides immediate and ongoing savings.
Paint spraying involves much more than pushing the material out through a nozzle. Modern systems may use combinations of turbines, needle valves, and atomizer devices. Many automated styles use dual shaping air, with an “inner” shaping airflow that propels the paint and an “outer” shaping air flow acting as a guide to promote a tighter pattern. These pressure blends may need to be changed dynamically during operation, such as when transferring material into a corner, or to overcome electrostatic effects.
Covering all the requirements
The primary way to overcome these and other challenges is to closely monitor and control the spraying airflow, pressure, and quality of multiple flow streams concurrently — not only with high accuracy, but also with fast response times. This naturally requires integrating a range of digital instrumentation, control valves, and sensors.
Some of the major components and features include:
• Air preparation with a filter/regulator
• Dew point sensor
• Flow/pressure sensor
• Dual-coil proportional valve for flow control
• Modular solenoid valve and input/output (I/O) assemblies
• Locally integrated closed-loop control for these devices
Some of these components, such as the air preparation and dew point sensor, can be in a common area off-board the robot. However, for best control purposes, many of the devices need to be suitable for mounting right on the robot itself, where space is limited, and weight carries a high penalty. Excessive weight constrains the robot movement performance or, in the worst case, demands upsizing the robot design at significant cost.
The technical skill and timeline required to choose from various component options, specify the best-fit devices, parameterize the valves, and then integrate and test the result is intimidating to say the least. Additionally, the design team must be familiar with the mechanical aspects, electrical/controls, and the nuances of paint handling.
For these and other reasons, a packaged solution addressing all these requirements in a modern and standardized manner would be welcomed by any paint application robot design team.
Getting the fine details right
Recognizing these needs in this large and elite market space, one manufacturer has developed a packaged paint automation solution excellent for accelerating design efforts, maximizing performance, and minimizing the total overall cost.
The solution incorporates several high-performance components pre-assembled on a backpanel using a plug-and-play concept. Devices include a modular pneumatic solenoid manifold and I/O platform with the ability to control up to three airflow streams using dual-coil proportional valves, each with a dedicated flow sensor. As part of the solution, a filter/regulator, dew point sensor, and overall air flow sensor are offered for upstream usage to supply one or more systems.
Figure 2: The Emerson paint automation solution delivers plug-and-play high-performance, using robust devices and application-specific tuning in a form factor optimized for the unique installation needs onboard an industrial robot.
Many thoughtful design features are incorporated into this solution to enhance its performance in various paint automation applications:
• Lightweight and compact valve bodies: The solenoid and I/O manifold components incorporate durable polymers where possible to reduce weight. All valve devices are engineered with minimized footprints.
• Smart proportional valves: The dual-coil valves consume no air, and they operate with an exceptionally fast response time of just 80ms. With patent-pending self-control adaptation, they incorporate on-board PID control for closed-loop control in concert with a flow sensor, and they are pre-programmed for this paint spray application. They can be dynamically commanded to achieve the necessary flow rates on the fly during painting operations.
• Floor-to-cloud connectivity: The proportional valves are available to support standard industrial communications protocols, including EtherCAT and PROFINET. Dew point sensors connect using standard Modbus TCP PoE, while the flow sensors use 4-20mA. This connectivity provides the bandwidth and responsiveness essential for reporting operational and diagnostic data up to the host system, and for flow commands to be sent to the paint automation solution.
Some individual products available on the market might be technically capable of approaching the necessary performance, and others might be sufficiently small to fit onto a robot. However, this solution is specifically engineered and pre-packaged based on robust components to deliver the necessary operational performance and long life, even in such a heavily used and always-in-motion application (Figure 2).
Transforming automated painting into a fine art
Key differentiators for this paint automation solution include the deep integration of all intelligent components and the seamless connectivity they provide to higher-level systems. The entire assembly reports up to PLCs or other types of edge controllers for providing complete control, and it interacts with HMI/SCADA systems for clear visibility. Regardless of how small or how large a painting robot OEM is, the design team will gain ready access to world-class technologies by incorporating this paint automation solution into their paint robot systems.
Emerson
emerson.com
Filed Under: AUTOMATION