Plasma cleaning and laser cleaning are advanced surface preparation methods used to enhance the quality of surfaces before manufacturing processes such as welding, coating, and adhesive bonding. While laser cleaning utilizes light energy to eliminate contaminants, plasma cleaning employs an ionized gas known as plasma.
Many manufacturers struggle to understand the differences between these two non-contact cleaning techniques, as both eliminate the need for solvents or chemicals—unlike traditional chemical cleaning. Additionally, they are increasingly preferred over abrasive methods like sandblasting and dry ice blasting.
What is Plasma Cleaning
Plasma cleaning is a method that utilizes plasma—an ionized gas— to remove surface contaminants by carbonizing them. Plasma is created by heating gas molecules, such as argon or oxygen, to a point where they become ionized, meaning the atoms and molecules carry an electric charge.
This versatile cleaning process is effective on a variety of surfaces, including plastics, metals, and ceramics. It excels at removing organic contaminants such as oil, dust, electrolytes, and paint. However, it is less effective against other types of contaminants, like rust and oxides.
What is Laser Cleaning
Laser cleaning is a process that employs laser ablation to eliminate surface contaminants. A concentrated beam of light, directed at the surface, transfers energy to the contaminants. As they absorb this energy, their chemical bonds with the substrate break, causing them to vaporize into dust and fumes.
Primarily used for metals, laser cleaning is also effective on ceramics and stone, but it is generally unsuitable for plastics and rubber. This method can remove a wide range of pollutants, including oxides, corrosion, paint, oil, dust, and electrolytes. However, it is less efficient at removing thick mill scale.
Main Differences Between Laser Cleaning and Plasma Cleaning
1.Speed of the Cleaning Process
Laser cleaning is significantly faster than plasma cleaning. The latter has a relatively slow duty cycle due to the time spent moving mechanical parts compared to the actual cleaning time.
Laser cleaning employs ultra-fast rotating mirrors (galvo mirrors) to direct the laser beam. For instance, in battery manufacturing, it takes only about 100 microseconds to move the laser from one cell to the next when preparing surfaces for welding.
In contrast, plasma cleaning requires a nozzle to move above the surface using a gantry system. These mechanical movements are slower than galvo mirrors, resulting in a lengthier cleaning process, especially in battery manufacturing where the nozzle must be positioned over each cell.
2.Mechanical Strength of Welds
When preparing surfaces for welding, laser cleaning yields stronger and more consistent welds than plasma cleaning. This is crucial in industries with stringent specifications, such as the battery sector, where quality assurance demands 6 sigma (3.4 defects per million) or even 7 sigma (0.02 defects per million).
Welds treated with plasma cleaning typically fail under 1000 gf (grams-force) and often struggle to meet specification limits, with a Process Capability Index (Cpk) below 1. In contrast, laser-cleaned welds break between 3000-5000 gf, consistently achieving a Cpk close to 2.
3.Cleaning Quality
In some instances, plasma cleaning can leave behind carbonized residues that are difficult to remove, even with secondary cleaning steps. This is particularly problematic for manufacturers dealing with oxides.
Laser cleaning, like plasma cleaning, varies in effectiveness depending on the contaminants. When the contaminants absorb the laser's wavelength effectively, they are vaporized, leaving no residue on the surface. For example, 1,064 nm wavelength that is well-absorbed by various contaminants, including oxides, dust, oils, coatings, and electrolytes. However, certain contaminants, like clear coats, may not be effectively removed with this wavelength.
4.Roughness Level
Laser cleaning systems can clean and roughen surfaces, providing comprehensive surface preparation for applications such as adhesive bonding. In contrast, plasma cleaning is limited to removing contaminants without altering the surface roughness.
Plasma technology was once the preferred method for cleaning applications that required avoiding solvents, abrasives, and chemicals. However, rapid advancements in laser technology have since improved its effectiveness and efficiency.
As a result, many manufacturers are now transitioning from plasma cleaning to laser technology to meet their production demands for speed and consistency.
