Five Steps to Automating Your Paint Line

Robotic spray painting offers significant advantages in cost and time, particularly when rotary applicators are used to achieve the highest possible transfer efficiency.

There are many compelling reasons to invest in robotic spray painting equipment. Foremost on the list is quality improvement. Manufacturers cannot afford differences in paint quality to remain competitive. Robots ensure that spray gun parameters and spray movement are always identical, resulting in consistent and precise coating of every part. This translates to greater productivity. The precision provided by robotic spray painting also reduces material consumption by up to 30%. A dual-component proportioner such as Graco ProMix PD2K, which mixes material close to the gun, reduces paint and solvent waste. The addition of an electrostatic spray applicator designed to deliver high spray performance and quality will further increase transfer efficiency and reduce costs. An often-overlooked element is flexibility. Robots can be easily reprogrammed to perform new jobs and adjustments can be made during operation. Automation also provides the flexibility to change materials and colors more frequently, significantly simplifying your production planning. Robots prevent people from performing dangerous work, allowing them to focus on skilled jobs requiring decision-making and reasoning. Assigning repetitive tasks to robots reduces workplace injuries and job dissatisfaction. When it comes to the advantages of automating a spray line, there are five steps to consider before implementation.

Analyze the Cost

Robotic spray painting technology is often viewed as expensive. The initial investment can be substantial, but automating the final finishing process will increase output and reduce costs, providing benefits for years to come. Furthermore, automation costs decrease each year. However, when planning a transition to robotic spray painting, it is essential to develop a long-term plan to accurately calculate and understand the expected balance sheet savings. Working with energy-efficient existing equipment can provide maximum savings; however, opportunities are not limited to this and continue to grow.

Select an Applicator with High Transfer Efficiency

The ProBell Rotary Applicator is a new product recently introduced by Graco's Industrial Products Division. Designed for automatic spray applications such as the Industrial Spray Applications sector, ProBell is a rotary atomizer that can be mounted to a fixed position, a piston arm, or a robot. Liquid is transferred to ProBell via low-pressure feed and distributed by a head cup rotating at a maximum of 60,000 rpm. The high rotation speed exposes the paint to high centrifugal force, causing it to be pushed across the head cup surface. When the paint reaches the edge of the head cup, centrifugal force separates it into a fine cloud of liquid particles. ProBell delivers high-quality finish because the droplet size is finer and more consistent compared to other spray methods. Additionally, the cloud of paint droplets is directed or shaped by a dual air shaper cup. This allows the pattern of paint droplets to be shaped and transferred toward the part.

Add Electrostatic Effect

To achieve maximum transfer efficiency, an electrostatic effect is added to ProBell. A charge is generated by a 60/100 KV electrostatic power supply within the rotary atomizer. The head cup is charged and the charge is transferred to the paint as it passes through the head cup. Charged paint droplets are attracted by the grounded target. The electrostatic effect ensures excellent paint adhesion to the back of the part. Thanks to this electrostatic effect, the ProBell rotary atomizer provides excellent finish with extremely high transfer efficiency.

Prefer Modularity and Scalability

An important feature of the ProBell Applicator is its modular, scalable design. This design offers users the opportunity to start with small jobs using a single controller and later move to larger jobs, or set up a complete system at once. This modularity allows users to meet production needs without exceeding budgets. ProBell contains a maximum of four controllers: electrostatic control; speed control; electronic air control; and system logic control that provides a user-friendly interface for easy management of spray parameters. The ProBell Applicator is offered in configurations for fixed mounting, piston, gapless wrist robot, and gapped wrist robot. The gapped wrist robot allows users to remove the applicator from the robot without removing all hoses, making maintenance easier. A removable cover also simplifies maintenance. The turbine unit features a proven, durable design with no wear parts in the air bearing. The ProBell Applicator is lightweight and compact while offering mounting compatibility. This allows the use of robots or pistons with lower carrying capacity and enables spraying in confined spaces. In summary, the applicator's unique, scalable design and superior quality, high transfer efficiency and precise spraying capability make it easy to develop solutions tailored to the specific requirements of each mounting.

Spray Gas Cylinders Uniformly

With Graco rotary bell atomizers and proportioning systems, less paint waste is generated, greater uniformity is achieved in paint distribution, ultrasonic tests are improved, and time and cost spent on cleaning are reduced. Throughout a service life lasting ten years or more, gas cylinders must have the capacity to withstand various stresses such as exposure to harsh air conditions and resist damage that may occur during transport and storage. When it comes to spray painting gas cylinders to withstand these stresses, Carbo Kohlensäurewerke from Bad Hönningen, Germany, is the expert. This industrial gas manufacturer and supplier inspects and paints approximately 30,000 cylinders each year, ranging from small cylinders 20 cm in height and 50 mm in diameter to large models as tall as a human and 230 mm in diameter.

Time to Upgrade the Paint Shop

In 2016, it became clear that Carbo's paint shop would show signs of wear after ten years of reliable service and would need to be upgraded. Without electrostatic technology, a temporary solution was implemented that allowed painting to continue using spray guns. However, the spray gun's high level of overspray increased paint consumption and cleaning time, which added to the unit's operating costs. A new solution was needed, and Graco was asked to propose one. Graco first proposed the ProBell high-speed rotary bell product, which was used at Carbo for a four-month trial period before purchase. Gas cylinder painting uses a single color (RAL 7037 dusty grey) and a 2K water-based system. Different caps for the cylinders also need to be painted. For this application, a high-performance Graco ProBell rotary atomizer system was installed. This system provides high spray output and high transfer efficiency. Additionally, its lightweight and compact design means that even moving parts with low lifting capacity can be used. Carbo also installed a Graco M2K proportioning system. This ensures fixed mixing ratio, minimizes wash cycles and material waste, and provides a compact, user-friendly design. Since an isolated installation was required, a pump was installed in the existing plastic cabinet to prevent failure of the electrostatic system.

Higher Quality; Lower Cost

The ProBell rotary atomizer achieves uniform and precise paint thickness by providing repeatable, uniform paint application over the curved contours of the cylinders, so Carbo is satisfied with the painting results. This is extremely important. Excessively thick paint can cause problems during ultrasonic testing of cylinders. On the other hand, excessively thin paint can cause mechanical damage during truck transport due to cylinders colliding with each other. The transition to ProBell also made it possible to permanently reduce the thickness of the paint layer at the base of the cylinders. Previously, cylinders were painted with two spray guns—one moving and one stationary. The cylinder was painted in position 1 and then the base area was painted in position 2. Paint was applied without electrostatic technology, which sometimes resulted in excessively thick paint layers at the cylinder base. Now paint is applied to the cylinder base in a single process step with uniform, reduced thickness. The high level of overspray was also significantly reduced, along with the need to clean the ventilation system almost continuously. Whereas previously the interior walls needed to be cleaned weekly with approximately 10 worker hours spent on weekly intensive cleaning, now only four worker hours are needed with the setup cleaned every two weeks. Overall, Carbo succeeded in improving the quality of its painting process while permanently reducing costs. Automating spray lines has never been easier or more economical. The automation of spray lines should be approached as a long-term strategic decision and an excellent opportunity to redesign your process and discover your entire value stream. For more details on robotic spray painting or the ProBell Rotary Applicator in general, feel free to seek advice from Graco experts. Bart Clerx Finishing Product Marketing Specialist Graco