Manufacturers often ask how to achieve a clean space without using a cleanroom. There are many reasons to do this, including achieving a reasonable process flow and assuring economic competitiveness. A clean space involves basic design and structure. There is an initial capital outlay for micro-environments and facilities design. Achieving a clean space involves coordinating engineering planning and production activities with the facilities group, the customer, and with safety/environmental professionals. Employee practices may also have to be addressed.
The first question, albeit a semi-dramatic question, is: what is my motivation? There are many reasons for setting up a clean area outside of a formal cleanroom. Do you need clean air? Clean water? Clean process chemicals? Product protection? Worker protection? Customer satisfaction? An actual clean area? The perception of a clean area?
What does the customer expect?
Where particles in the air must be controlled, some sort of HEPA filtration is required. If the customer has formal or contractual requirements for a cleanroom, building a cleanroom is the only way to proceed. In other instances, a mini-environment may be a more economical and technically-superior approach.1 A mini-environment where the processes are conducted by observant, well-educated personnel can be more successful than a stand-alone cleanroom where general employee practices are not as well defined.
However, there are also perceptual and expectation requirements. These requirements may first appear during a site inspection by a prospective customer. One group took what appeared to be the logical step of adopting a bench with filtered air flow for final cleaning prior to the final finishing process. The prospective customer was not impressed. The expectation was the presence of a clean environment that looked like an independent room.
Aside from customer perception, it is important to define the clean space, to define the contamination sources, to define how the product might become contaminated; this means starting with what some may consider to be the non-glamorous, mundane parts of cleaning and contamination control. We often assert that contamination control starts early-on in the assembly process. This means that, for example, the machine shop may require clean areas and clean practices.
Initial critical cleaning
Immediate cleaning after machining is one of the most effective paths to achieving product quality. Since cleaning involves three steps (washing, rinsing, and drying), it is crucial to assure that these steps are carried out promptly and effectively.
Initial cleaning processes typically do not require the complexity of a multi-stage precision cleaning system with ultrasonics. Benchtop cleaning may use a simple immersion bath or a spray system. Unfortunately, the cleaning products that are used may be poorly-controlled or may even be unspecified—the process is inherently considered to be unimportant. Household, consumer products may be used. A safety or environmental professional may decree a change in the cleaning chemistry, perhaps with admirable air quality or worker safety motivations. However, if the required cleaning efficacy is not achieved, undesirable (sometimes catastrophic) impact on product quality has been observed. Defining a clean area may start in the machine shop; this means that the processes have to be specified at the engineering level.
Applicators, peripherals, environmental controls
A rag is not just a rag. Handwipe cleaning often involves application of the cleaning agent using brushes, cloth, or paper towels. To achieve a clean area, you have to specify the appropriate applicator. This is always a compromise because applicators inherently introduce some level of particulate or chemical contamination.2 Achieving a clean area in a shop involves specifying the applicator for the cleaning agent.
Evaluate gloves and other protective equipment. Particularly at non-cleanroom stages of production, the Industrial Hygienist may be in charge of specification. Of course the worker has to be protected. However, product contamination also has to be minimized. As an engineer or process designer, the ball has to be in your court as well; so you may need to coordinate (i.e. negotiate) with the safety professionals.
Drying and storage
Often, parts are dried using shop air. This air may contain oil; and the net result of attempts at drying may be deposition of both thin film and particulate contaminants. Coordinating with the facilities group and monitoring shop air is an important step in achieving a clean area.
Storage and transport
Parts may be machined and then stored either in the shop or in a storage room where air quality and access are not controlled. If parts are stored in a shop, there can be gradual accumulation of process fluids, dust, and other soils; and there is a tendency to move the parts from place to place. Set up a protocol for protecting and storing the parts after they have been machined and cleaned.
Invest in an enclosed storage space, specify that parts be stored in that space immediately after cleaning, and limit access to that space. Even a simple enclosed, clearly-identified clean space can improve productivity. It can also improve customer perception.
We think of controlled environments, particularly of mini-environments, as protecting the product. However, mini-environments may have other purposes; and those purposes may conflict with product protection. For example, we want to keep contaminants away from the part. However, minimizing worker exposure to airborne hazards involves different airflow patterns than are used in product protection. Meeting community exposure and environmental requirements may result in containing the chemical within the manufacturing plant. Some booths and mini-environments are being designed to be multi-functional, to protect workers, the environment, and the product. As a process designer, or as the person involved in contamination control and process improvement, it is productive to interface early on with safety and environmental professionals as well as with facilities engineers. Taking a holistic approach to selecting the appropriate mini-environment is likely to lower the initial overall capital outlay and will result in less cumbersome processes.
Even if a formal access controlled and highly filtered cleanroom is not a requirement, consider the functions that a cleanroom provides when planning a clean workplace. Look at how product can become contaminated. Observe such factors as air flow, personnel practices, and proximity of contaminating sources.
Simple, low cost changes can make a big difference. For example, covering street clothes with a lab smock and providing a closet to remove fuzzy sweatshirts and jackets from the work environment can go a long way towards promoting the perception and actually achieving a cleaner working environment.
1. B. Kanegsberg and E. Kanegsberg, "Controlled Mini-Environments," Controlled Environments Magazine, August 2006.
2. Howard Siegerman, "Wiping Surfaces Clean," Vicon Publishing, 2004.