How Clean Are Paint Shop Cleanrooms?
Product Announcement from Hosco Finishing System Components
Although great strides have been made in paint shop cleanrooms, there are still major opportunities to improve their cleanliness, especially with improvements in the design and construction of the paint circulation and supply systems . . .
By S. Thomas Boyce and Jan Pitzer
Hosco Livonia, MI
During the past 15 years, the automotive industry has developed a significant number of paint technologies to address the needs of the environment, product appearance and durability. Along with the development of new coatings, most new facilities have incorporated cleanroom environments in which these materials are applied.
The main reason for cleanrooms is to improve the quality of the paint finish by reducing sources of dirt contamination on a wet film. This dirt contamination causes some manufacturers to repaint the entire car rather than making spot or panel repairs. But, by eliminating dirt contamination and the resulting defects, expensive repair procedures can be avoided.
Until recently, most of the emphasis on eliminating dirt contamination in cleanrooms has been focused on the people working in the paint shop. Early evaluation of the sources of paint defects indicated that 60% of these defects were caused by dust particles, lint, hair, dandruff, powder, cotton fibers and other pollutants carried by workers, supervisory personnel and visitors working around the paint shop (see image). Therefore, anyone entering a cleanroom must wear lint-free coveralls and a hair bonnet as well as pass through an air shower compartment that may contain a shoe scrubber. These steps are designed to remove contaminants that can cause flaws in the paint finish. There is also a psychological benefit to this procedure because it conditions people to be aware of all sources of dirt and to think about their surroundings, which affect the quality of their work.
But, what about the other 40% of dirt sources, such as agglomerated paint particles, color carry over during the color change process and paint line cleaning? The newer high-solids and waterborne basecoat materials are much less forgiving than the older low-solids solvent-borne paints. They are more prone to shear degradation, agglomeration, foaming and skimming, all of which can contribute to a greater potential for introducing dirt into the paint circulation system.
From an equipment standpoint, much of the work in paint circulation systems during the past 10 years has been focused on the paint mix room. The development of lower shear pumps, low shear agitation methods, low shear regulators and new mix tank designs with liquid level controls and automatic filling have greatly improved the overall operation of the paint supply system. In addition, the choice of the proper grades of stainless steel and passivated systems has reduced or eliminated the gelling of paint caused by metal ions, lowering the potential for dirt to enter the paint supply system.
While there are some continuing refinements of the storage and pumping supply systems, most of the emphasis on the management of dirt has shifted in recent years to the piping system. READ MORE.....