The manufacture of everything from toothbrushes to autoparts can benefit from the use of atmospheric plasma and flame surface treatment during assembly and decorating operations. These technologies increase material surface energy to promote bonding with inks, adhesives, paints and other coatings, and their use is growing. To bring these solutions to the factory floor, specialty integrators are called upon to develop material handling and automation of the treatment process. Here’s a look at the technology, and how one integrator worked with a supplier to automate the flame treating process of an automotive parts manufacturer.
“Companies in the medical, automotive, packaging, consumer products, wire & cable, sporting goods, furniture, and others markets find that surface treatment improves bond strength, increases throughput, and can also reduce cost,” says Mark Plantier, vice president of marketing for Enercon Industries Corp. (Menomonee Falls, Wis.), a maker of custom surface treating solutions with 30 years of experience of combining reliable power supply technology with innovative treater station designs. The company's product line includes the Plasma3 atmospheric plasma system, a wide range of bare and covered roll corona systems, and unique flame treatment systems featuring PowerFlame burner technology.
Flame and atmospheric plasma are the two leading surface treatment technologies. A flame plasma is formed when a flammable gas and atmospheric air are combined and combusted to form an intense blue flame. The surfaces of materials are made polar as species in the flame plasma affect the electron distribution and density on the surface. This polarization is made through oxidation. In addition, functional groups are deposited on the surface. This increases the surface receptivity to inks, adhesives, and other coatings.
“Flame can be used to treat both small and large surface areas with burner designs available in widths to match the specific application,” explains Plantier. “While combustion control technology ensures modern flame treaters provide repeatable treatment results, a series of interlocks are used for safety. System integrators incorporate these interlocks into the overall work cell, which can vary from basic to quite elaborate.”
Because the relationship between the surface treating equipment supplier and the system integrator is critical to an end user’s ultimate satisfaction, Enercon has partnered system integration companies in a variety of ways. Jerry Schmit, senior applications engineer for Midwest Engineered Systems Group (Pewaukee, Wis.), says, “Each customer’s requirements are unique to their operation and space available. We’ve had projects where we’ve integrated an Enercon flame treater with a conveyor, and we’ve also constructed entire rooms where parts are transported in, treated and then exit the room for additional processing.”
“We enjoy working with Enercon because of their depth of knowledge in surface treating," says Schmit. “Their solutions can be used in virtually any application or industry requiring improved adhesion. And, since they offer free lab testing with a broad range of treatment solutions, we know the end user is always getting the best technology for their specific application.”
It’s essential for the integrator to gain an understanding of the surface treating equipment selected for the application. Variables to be taken into account include dwell time and the distance required between the surface treating head and the surface to be treated. Additionally strategies for automating the process to achieve the customer’s desired output requirements need to account for safety interlocks and feedback between the automation components and the surface treater controller.
Flame plasma surface treating
Most often, projects are dedicated to a specific product and treatment pattern, says Plantier. However, occasionally a customer will want to maximize its automation investment and be able to perform multiple operations within the same work cell. Enercon and Midwest have partnered on a few projects like this, including one for an automotive parts application that required pretreatment prior to applying an adhesive.
The customer needed to flame treat two very different parts. The system requirements in this case included building a safe system that utilized robotics for efficiency and repeatability that could deliver a part-to-part cycle time of 60 seconds or less, and achieve an inherent surface energy (also called a dyne level) of 50 dynes or greater.
Midwest developed a program that allows operators to scan a unique a bar code for each part, which automatically loads the correct program. “The material handling component uses sensors to verify the correct part is in place, in this case a dashboard,” says Schmit. “The part is presented to the robot, the flame treater is activated, and a multi-axis robot executes a path enabling the treatment head to follow a precise treatment pattern for the part.”
The sequence of operations for the system were as follows:
- Operator scans the barcode of the part to be processed;
- Operator manually places the part on the fixture at the “Operator Load Station”;
- Operator presses the cycle start button;
- The rotary table indexes the part to the “Robot Treating Station”;
- The robot automatically flame treats the part;
- The finished part rotates back to the operator and the operator unloads the part.
“While the robot is flame treating the parts, the operator is able to load another part onto the open fixture. This enables continuous operation of the system and optimizes the cycle time from part to part,” says Schmit.
Atmospheric plasma surface treating
Similar to flame systems, atmospheric plasma systems are used to modify surfaces prior to printing, bonding, painting, decorating and coating. Plasma systems clean, etch and functionalize surfaces to promote adhesion on surfaces that would be otherwise unresponsive. “For many applications the use of atmospheric plasma enables our customers to eliminate hazardous chemicals and primers, or reduce their costs by switching to a more cost effective coating,” says Plantier.
Atmospheric plasma systems are different from flame systems in that they do not require gas, operate at lower temperatures, and offer options for variable chemistry plasma for difficult-to-treat applications. Within the plasma range, there are two main technologies: blown arc and blown ion.
Blown-arc air plasma is formed by blowing atmospheric air past two high voltage power electrodes; it is sometimes referred to as “corona treatment.” A common use for this technology is prior to pad printing, as might be done on a polypropylene toothbrush.
“Blown-ion systems generate a concentrated blown-ion discharge that bombards a material surface with a high-velocity stream of charged ions,” explains Plantier. “Positive ion bombardment facilitates a micro-etching or scrubbing (ablation) effect, which can remove (desorb) organic and inorganic contaminants from the surface of an object. Particles positively charge the object's surface increasing its surface energy and making it more receptive to inks and coatings.”
An advantage of blown-ion systems is their focused treatment profile, which enables treatment of both flat areas and recesses. These treatment heads may be statically mounted or integrated with a robot to execute complex treatment patterns.
Applying graphics to toothbrushes is one common use of atmospheric plasma systems. Others include pretreatment of headlamp assemblies prior to bonding, wire and cable applications prior to printing, and other applications requiring precise treatment patterns.
Midwest’s Jerry Schmit says, “The emergence of projects related to surface treating has presented us with opportunities to break into new market segments.” For Enercon, integrators such as Midwest provide expertise in material handling, general automation and robotics programming so their clients can maximize the performance of the company’s surface treating solutions.