Residue is a major concern for manufacturers. Consequences of inadequate residue removal include undesirable appearance (spotting, staining), poor coating adhesion, low yield, and catastrophic product failure. To successfully remove residue it is useful to understand what that residue is and where it came from. Also consider: what is it you are trying to clean? Changes in materials of construction of product you are manufacturing can impact cleaning and surface quality.
Suppose you add a new material of construction
A small change in one material of construction can necessitate a change in the cleaning process One manufacturer successfully fabricated bronze products – had been for decades. Then, they introduced a new product line containing brass. Both bronze and brass contain copper; brass is an alloy of copper and zinc. They thought: how different could manufacturing be? Very different! The brass parts exhibited significant surface quality problems. They had to modify the cleaning process.
Let’s consider introducing a product that contains a more porous material than has been used. More porosity means more surface. A porous material can entrap soil, both thin film and particles. Removing the soil requires more aggressive cleaning. In fact, the porous material can trap cleaning agent, so more thorough rinsing is needed. However, the solution may not be as simple as using a more aggressive cleaning agent or stronger cleaning force or higher temperature.
Any cleaning process is a “Catch 22” situation that involves balancing effective cleaning with good materials compatibility. With materials compatibility problems, the cleaning process itself causes damage. Examples include anything from product deformation or even dissolution to subtle surface changes. Surface damage can mimic residue. Surface damage can impact adhesion and overall product performance problems. Avoid surface damage by testing new materials of construction with dynamic compatibility studies – testing under a reasonable multiple of actual process conditions.
The bottom line: For cost-effective, quality production, re-evaluate the cleaning process when you introduce a new material of construction.
How many different products are you trying to clean at once?
In a general sense, attempting to clean many different materials of construction in a single process bath can spell disaster. Soils from one part can settle on another; you may end up with parts that are dirtier than they started. As we often explain, it’s not a good idea to clean your baby and your carburetor in the same bath. Even when parts are acceptably clean, dissolved residue of materials of construction can result in cross-contamination.
For this reason many successful manufacturers choose to invest in a separate cleaning processes, even separate cleaning machines, for high-value product. Segregating product lines does not necessarily mean purchasing new equipment. For example, for small scale ultrasonics applications, cleaning product lines in separate beakers can be a cost-effective option.
A note about the word “product”
For parts or components manufacturers, the product is the metal, glass, polymeric, or composites (or a combination) that constitute the component or final assembly that is being produced or repaired. It’s different in food, pharmaceuticals, or even coating manufacturing. The product in pharmaceutical manufacture is a powder or gel or liquid. Cleaning product-contact surfaces is also critical; when a new product is introduced, residue from the previous product becomes an acute contamination problem. Cleaning product contact surfaces is a topic for another issue of “Clean Source.”