“We get parts absolutely dripping with oil; we can’t coat them.”
“We get parts that look OK. Sometimes the deposition works; other times it doesn’t.”
“We have to inspect all incoming parts; and we have to clean nearly all of them or our yield goes down.”
We hear these refrains from manufacturers and assemblers at the middle or the end of a supply chain, and the problem is increasing. Here are some root causes and some actions you can take to protect your production line and to strengthen your competitive position:
Costs. When cleaning is considered to be a task that is not value-added, it is more likely to receive a lower priority. For example, neither the supplier nor the recipient may appreciate the technical and economic benefits of cleaning sooner rather than later. Baked- or dried-on soils are adherent. The longer a soil remains on a part, the more adherent it becomes. Therefore, it is usually more effective and less costly to clean as early in the process as possible. (A common analogy is a lasagna pan that has been left overnight before cleaning.)
Part of the problem is that it is sometimes difficult to assign a value-added amount to a cleaning process. However, a value can frequently be determined using a double-negative approach. The value added is the negative value or cost of not cleaning. Suppose inadequate cleaning decreases yield. Parts may need rework or become scrap. Dysfunctional or unusable product means a substantial investment of time and resources. In such instances, a positive value-added figure can be calculated for the cleaning step.
Regulatory Restrictions. Regulatory drivers—both safety and environmental—are sometimes responsible for decreased cleaning. Many effective cleaning agents have been removed from production or are subject to use restrictions. In general, the more effective a chemical is at breaking the bonds holding soils to the surface, the greater the likelihood that it will break bonds that shouldn’t be broken—thus harming either workers or the environment. Destruction of UV-protecting ozone (good ozone) in the upper atmosphere led to the phase-out of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Many of them are good solvents for manufacturing oils and other soils. Creation of smog-producing ozone (bad ozone) in the lower atmosphere is driving restrictions on volatile organic compounds (VOCs), including those that are key ingredients in many water-based cleaning products.
A company may adopt a new cleaning agent or cleaning process due to environmental regulations without a clear understanding of how it will impact the next steps in the process. Products may arrive dripping in oil because the manufacturer has discontinued cleaning to avoid costs of process change and costs of permitting. Or they may clean the parts only to find that in order to avoid corrosion, they have to store the parts in a protective “light oil.” This means they may be depositing a new soil on the parts.
Costs, Communication Problems. Where outsourcing is adopted for economic reasons, communication and specification of requirements may be lowered in importance. This can be false economy. One recurring complaint is that parts from foreign suppliers do not show consistent cleanliness. There can be many reasons for this. For example, soils become more adherent with time, so if parts are not adequately cleaned before shipping, the long transit time increases the burden of cleaning by the recipient. In addition, with a geographically diverse supply chain, there may be less than optimum communication of all the processes used by the supplier, including industrial fluids. We have seen instances, for instance, where several metalworking fluids appeared to be used, without documented technical data sheets or safety data sheets.
Expectations, Requirements. Parts may not actually be dirtier than they have been, but expectations and requirements for cleanliness may have increased. This is especially true for high-value components in aerospace, electronics and medical devices arenas.
So what can I do? The most effective action a manufacturer can take is to become educated about cleaning and cleaning processes. However, the details of what you do depend on where you stand in the supply chain—and on the supplier/customer relationship. With such knowledge, expectations and requirements can be more made more definitive.
What if the customer ships contaminated parts? If you do contract work that involves surface finishing like plating, deposition, or an engineered coating, the situation becomes a bit more complex, especially if your customer is no longer doing adequate cleaning and expects you to fix the situation. Cleaning is costly. If you are new to the field, it is worth the time to investigate the types of soils you are likely to encounter. The cleaning system has to be aggressive enough to remove a range of soils without damaging the parts. In addition, if there are a range of metals and other materials of construction, you may run into galvanic interaction, especially if you have to clean parts received from an assortment of customers. This can result in damaged parts, particularly where aqueous systems are used. The bottom line is that you may have to change out the process baths.
Some manufacturers doing surface finishing add a surcharge if they have to do extra cleaning. Obviously, you do not want to lose established customers, so adding a cleaning system might be a necessity. However, going forward with new contracts, it is important to factor in the expenses of cleaning incoming parts.
Increased expectations for the final product also have to be considered, particularly for new products. It is important to determine if the current cleaning process is adequate to achieve good coating performance.
How can you get your suppliers to do a better job of cleaning? If the supplier can institute or improve a cleaning process before the part is shipped, it may be possible to avert a more complicated and more expensive cleaning process later in the assembly flow. Clean early, clean often. We do not advocate adding steps to an assembly process unless those steps provide value (a little bit of cleaning can often go a long way). A simple dip or wash off or brush off may be all that is needed at an early stage. Since soils become more adherent the longer they remain on the surface of the substrate, any actions that can reduce storage and shipping times can make the job of getting and keeping a part clean easier. This may be a point to consider when deciding whether to use a distant supplier.
Whenever a part is transported, whether across the globe or across a room, packaging and transport conditions can make a difference in the cleanliness of the part when received. Rather than immersing a part in oil before shipping, changes in packing conditions might impart the needed corrosion protection but reduce the process time and complexity.
If the soil changes, the cleaning processes may need to be modified. It is important to be aware that some of the process fluids might change due to technical, economic or regulatory drivers. For instance, many lubricants and oils have been reformulated to lower the amount of VOCs in the composition. These reformulated materials may be distributed even in areas that are not subject to severe air quality regulations.
If your manufacturing facility is responsible for calling the shots, it might be possible to make effective cleaning part of the contractual requirements. Of course, such arrangements have to be made up-front. In addition, cleaning requirements have to be realistic and achievable by the initial fabricator. A large manufacturer might impose stringent cleaning requirements on the supplier, providing them with a large book of “approved” cleaning processes. On close inspection, the instructions may be unclear, contradictory, or may even reflect practices that are long out of date. It is far better to involve the supplier in setting up cleaning requirements procedures, and then hold them to those requirements.
What if you are a supplier, and you a do a terrific job of cleaning? If you are on top of the game with respect to cleaning and contamination control, you can gain points with your customers. A customer who is aware that his supplier is proactive—and that the incoming product is less likely to require extra cleaning and is less likely to fail—is more likely to be a repeat customer. You can build a competitive edge by including your cleaning practices and process documentation as part of your publicity.
ABOUT THE AUTHORS
Barbara Kanegsberg and Ed Kanegsberg (the Cleaning Lady and the Rocket Scientist) are experienced consultants and educators in critical and precision cleaning, surface preparation, and contamination control. Their diverse projects include medical device manufacturing, microelectronics, optics, and aerospace.