The process of removing contaminants from parts may not seem like a frontier in the green revolution. However, advances in chemical engineering are producing more effective, more environmentally friendly cleaners which also improve remanufacturers’ bottom lines.
Let’s examine how these new technologies can benefit you, how to begin and what you’ll need to consider.
There are four main reasons to update your aqueous cleaning process:
- Cost reduction and leverage: Better cleaning can reduce expenses, and because buyers choose remanufactured goods based on their lower cost, any decrease gives the remanufacturer greater marketing leverage.
- Cleaner products: Better cleaning means less time spent re-cleaning or reworking the product, lowering material expense and labor costs.
- Alkalinity: To create simple methods to handle any contaminant, some suppliers use products that depend on extremely high pH levels. This not only creates safety issues, it damages equipment and alloys.
- Waste processing: Disposal fees for cleaners with high pH, high chlorine content and a range of older technology additives can be quite expensive, and the new generation of cleaners is much better for the environment.
Begin From The End
So how do we redesign the cleaning process? Begin by considering your overall goals, and more specifically the end state you desire for your product. You may want to codify this as a specific cleanliness standard.
Then consider what effect changes in cleaning might have on the overall workflow in your plant. Are there limits on throughput time your cleaning process will have to meet? What will be the effect if the time spent cleaning the product increases or decreases significantly? If it decreases (which is more likely when redesigning a process) will there be ways workers can use the time gained for other tasks? What amount of rework will be acceptable?
An excellent resource for this phase is this infographic that Chemtool Incorporated has prepared, detailing an example process for removing heavy soils.
Consider Your Substrate and Soils
Substrates are the surfaces being cleaned; soils are the contaminants being removed.
Ask yourself these questions about your incoming parts:
- What metals are they composed of?
- What soils are typical?
- Is paint removal necessary?
- Will other coatings, such as a rust preventative, need to be removed?
- If incoming pieces are divided into subassemblies at some point, are they different enough that they will need separate cleaning processes?
- Is there rubber or other non-metals on the parts that will affect your choice of cleaner?
- Lastly, what waste treatment process will be used for the spent fluid? What processes will need to change if treatment requirements change?
This is a good point in the process to consult your cleaning supplier about what specific cleaners will be best for these materials and soils. For example, cleaners suited to ferrous alloys may damage aluminum. Some soils will be best cleaned with an alkaline mix, but welding marks will require treatment with acidic solutions. A little good advice will go a long way in helping you design a process that works well from day one.
To ensure consistent results, you’ll need proper control. The four major factors in cleaning process control are are spelled out in the acronym TACT: Time, Agitation, Concentration, Temperature.
Your process design will need to factor in allowing time for chemical reactions to occur and for monitoring the run. Time and temperature determine when (and to some extent, how) the chemical reaction will take place and for how long.
In order to ensure the right amount of reaction products reach the metal surface and interact with soils, you may need to create motion and/or pressure over time. Agitation can also help move soils well away from the substrate after cleaning.
This is the amount of available reactive components per unit volume of bath. Concentration and agitation determine the extent of the chemical reaction applied.
Higher temperature reduces the viscosity of soils and increases the chemical reaction rate.
As noted above, temperature and time determine when and how the chemical reaction will take place.
Completing the process
There’s much more to process redesign than we can cover here, which is why we’re making a free guide, Remanufacturing Cleaning: Problems, Solutions and Control. It not only goes into full depth on the subjects we’ve reviewed here, it includes a full glossary and discussion of control methods, disposal considerations and more. Download it, or our reman cleaning catalog, and get started today.