Plasma Cleaning and Coating of Metal Strip
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Solution Overview
Problem
Conventional PVD coating processes for metal strips face significant contamination issues due to residues from the cleaning process, which disrupt the coating process and require frequent maintenance, especially when dealing with advanced and ultra-high strength steels with thick oxide layers.
Innovation Solution
A method and apparatus that separate the cleaning and coating processes, using a plasma cleaning technique in a low to medium vacuum environment, followed by a gas stream to remove residues, and employing a gas bearing lock to maintain pressure differences and prevent contamination, allowing for reduced air locks and improved residue removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PVD coating processes are used, then coating can be applied to metal strip, but residues from cleaning process contaminate the deposition chamber requiring frequent maintenance
Solution Approach 1:
The apparatus is divided into separate cleaning and coating zones with different pressure levels. The cleaning chamber operates at higher pressure (0.1-100 mbar) while the deposition chamber maintains lower pressure (10^-4 to 10^-6 mbar), physically segmenting the contamination sources from the clean environment.
Solution Approach 2:
A gas stream acts as an intermediary medium to transport residues from the cleaning chamber through the deposition chamber to the exhaust system. The gas flow carries contaminated particles away from the deposition zone without requiring direct contact or breaking the vacuum seal.
2Manufacturing precision
If plasma cleaning technique is used to remove thick oxide layers, then cleaning effectiveness is improved, but residues contaminate the deposition chamber
Solution Approach 1:
Residues are extracted from the cleaning chamber environment and removed via a dedicated gas stream pathway. The gas flow captures sputtered particles and oxide residues, transporting them directly to the exhaust system without allowing them to settle in the deposition chamber.
Solution Approach 2:
A pneumatic gas stream is used to remove residues from the cleaning process. Gas is introduced into the cleaning chamber at controlled flow rates to entrain and transport particulate residues away from the metal strip surface and through the deposition chamber to external exhaust.
3Device complexity
If pressure in cleaning chamber is increased to reduce air locks, then number of air lock sections is reduced, but residue removal becomes more challenging
Solution Approach 1:
The gas stream operates continuously throughout the cleaning and transition process, maintaining constant residue removal capability. Gas flows continuously through the cleaning chamber and deposition chamber, ensuring residues are constantly swept away rather than accumulating during the transition between pressure zones.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach minimizes contamination in the deposition chamber, reduces maintenance stops, and achieves superior adhesive bonding properties for Zn-based and Zn-Mg coated steel strips by maintaining consistent pressure and effectively removing residues, thus enabling continuous operation with reduced costs.
Implementation Method 1
cleaning the metal strip by magnetron or plasma etching in a cleaning chamber
Implementation Method 2
evaporating a metal in the connected coating chamber
Implementation Method 3
applying the vapour to the substrate via a confinement chamber
Implementation Method 4
a gas stream is maintained through the cleaning chamber to remove residues resulting from the cleaning of the metal strip
Implementation Method 5
by using a gas bearing lock between the cleaning chamber and the deposition chamber
Data Source
Figure 1~2
Figure 3a
Figure 3b
AI summary
The invention relates to a method and an apparatus for cleaning and coating a metal strip wherein the metal strip is cleaned in a cleaning chamber connected to a deposition chamber and wherein the vacuum pressure in the cleaning chamber is kept in the range of 0.01 - 100 mbar and the vacuum pressure in the deposition chamber in the range of 0.01 - 10 mbar.