The “clean room” of the automotive industry is not classified according to ISO. Most of the critical areas, such as transmissions, fuel injector assembly shops, and spray booths were not originally designed to meet the requirements of a "clean room," but were still designed as unsorted clean rooms. However, engineers at automakers are increasingly aware of the need to maintain cleanliness during the production process, and the current development of this increasingly stringent control trend is also accelerating.

Clean room design

   In a relatively large vehicle assembly environment, oil mist and metal particles are emitted from robots and other assembly equipment to be dispersed into the air. Precise mechanical components must be cleaned and processed. The core of solving this problem lies in setting up dust-free areas or protected areas, separating spray paint from important production areas, and avoiding cross-contamination. Control of air pollutants cannot allow it to enter production areas such as engine and transmission assembly areas.

   The accumulation of contaminant particles in an improper location of the assembly can impair its function or cause it to be completely scrapped. Diesel injection technology is a good example. Since 1996, this technology has rapidly improved over the five years, resulting in higher and higher injection pressures and smaller and smaller nozzle sizes. The maximum pressure of the high pressure pump is above 2000 bar, and the fuel is injected into the combustion chamber through a hole with a diameter of approximately 100 μm. It is not enough to ensure that different components are highly clean when producing such systems, and the assembly process must also be carried out in a highly clean environment.

   The injection system shows that many automotive components must maintain a high degree of surface cleanliness, but these critical areas are often concentrated in the interior of the component. Many components use a very complex metal structure that is shaped to a final shape and includes media through holes or interior surfaces that require a high degree of cleanliness. The only way to check the cleanliness of such components is to use a cleaning procedure to extract all particulate contaminants and analyze the cleaning solution. In order to do this, particulate contaminants are generally deposited on the filter membrane, followed by microscopic analysis or gravimetric analysis.

   In the manufacturing environment, the particles that people pay attention to are generally relatively large in size. They do not spread like smoke and fall onto the surface of the component, so they are completely different from the air control scheme in semiconductor clean rooms. In addition, the range of people's attention is also becoming narrower and narrower. The size of the largest contaminants to be controlled is between 80 and 120 μm, and the smallest is between 40 and 60 μm, such as metals and pollutants. These users' goals are no different from those of conventional clean room users: they prevent the product from appearing defects and functional defects with the naked eye.

 Automotive Manufacturing Industry Room/Clean Room Overview:

   German automotive supplier Siemens has used a purification class 10,000 facility for its fuel injector assembly plant more than a decade ago. Eight years ago, as a cleanroom consultant, I designed a fuel injector assembly facility for Ford Motor Company with a purification class of 10,000. Its design concept is closer to a typical semiconductor facility than to a traditional automotive production line.

   We have sampled the air in the “clean room” of the car. The results show that the volume of the pollutant particles is relatively large, usually around 50 μm or more. The production of these particles is mainly due to poor positive pressure and lack of air lock chambers and passages, as well as the pre-cleaning treatment of instruments, workers, and components. We found that after we implemented the following measures, we can achieve the requirements of the cleanroom class.

1. Before entering the clean room, clean the instruments, personnel and parts;

2. Seal the building with controlled multi-level pressure, temperature and humidity control devices;

3, HEPA filtration;

4, enhance the process to reduce the production of particles / precipitates;

5, protective outerwear;

6, clean;

7. The two-door configuration separates adjacent spaces, including shipping and receiving areas.

 Aviation Clean Room/Clean Room Overview:

   NASA's space operations to the solar system's celestial bodies must be able to sustain their lives, or they may need to maintain their lives in a basic state of evolution. They have strict restrictions on the maximum number of spores on the spacecraft surface; along with the clean room With the improvement of the efficiency of regulations, these restrictions are likely to slowly decrease. Of course, other airline clean room requirements are basically the same. Several promising technologies can help contractors reduce spore counts, achieve acceptable levels, quickly determine microorganisms, and determine the detailed genome of spacecraft microbes.

   NPR 8020.12 allows alternative methods for dry heat sterilization at 125°C as long as procedures and quality control are approved by the NASA Planet Protection Officer (PPO). Then, these methods are listed in the approved PP (planetary protection) plan. By referring to specification figures, aircraft hardware drawings can use these unique microbial reduction methods. Microbial barriers can be used to prevent re-contamination of previously sterilized areas; pressures of at least 1,244 Pa (5 inches of water) can meet the need to prevent microbial invasion. High efficiency air filter HEPA (0.3 μm, efficiency 99.97%) is also a recognized high-efficiency microbial barrier. NASA requires that the spacecraft be assembled in a clean room with a minimum of ISO Class 8 (Fed. Std. 209E Class 100,000).

   For a Mars landing mission, the maximum number of spores the entire spacecraft can allow is 300,000 (or <300 bacterial spores/m2); all other targets still have a probabilistic slope requirement. Each surface area of each spacecraft can have a volume of 300,000 spores, which applies to non-special areas of Mars (most surfaces), and a total of 500,000 including organisms within the hardware (such as canned capsules). Pirates and other spaceships that come into contact with "special areas" or find life must meet the requirements of 300,000 and reduce the surface bioburden to 10,000 by dry heat sterilization, which means that all visible spores on the surface of the spacecraft will not exceed 30. One.

   Most aerospace cleanrooms have unknown microbial deposition rates and surface microbial populations, and usually do not have a microbiology laboratory that can be put into immediate use. When building a suitable microbiology laboratory to implement NPR 5340.1, the first thing PP programs need to do is make their clean rooms as sterile as possible. A temporary laboratory can be built for this purpose, using a Class 100 (ISO Class 5) clean bench and equipped with a desktop thermostat. The use of commercially available settling plates (capturing microbial radiation dust) and tryptic soy agar (TSA)-based contact plates (determination of the clean room surfaces) can be performed on clean rooms (including thermal vacuum chambers, acoustic and vibration installations) , and preliminary testing of related equipment. These programs are primarily designed to detect and count the number of heterotrophic, mesophilic, and aerobic/anaerobic microorganisms. The most likely organisms to survive in space and in the planetary environment are hihalogens, certain species of Bacillus and extremophiles.

   Therefore, with the development of science and technology, human space activities or the possibility of alien immigrants are realized, such as deep space station (lab), moon space station, immigration Mars and so on. To prevent unpredictable risks, high-tech clean rooms must be constructed to simulate the space for human survival and development. Provide necessary support for human activities.