Built To Spec: Class 100,000 in 10,000’s clothing

Cleanroom slated for Class 100,000 status gets bumped to 10,000 after five months of production

by David Herron

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Adding a Class 10,000 or 100,000 cleanroom was the next logical step in meeting the growing industry needs for Aircom Manufacturing Inc. (Indianapolis).

The most prevalent cleanroom requirement for injection molding, including medical and pharmaceutical, is a Class 100,000 environment, so the molded, metal and assembled products manufacturer decided to build just that with plans to someday convert the space into a Class 10,000 cleanroom. The new cleanroom is 2500 square feet and can house up to 10 injection molding presses, which yield annual volumes in the millions and typical for pharmaceutical packaging and delivery systems. The cleanroom is staffed by no more than a dozen people per shift, depending on the number of presses running and the level of automation.

Because Aircom had no immediate requirements for cleanroom molding, the construction schedule was not critical, and construction of the first cleanroom began in July 1998. Products began rolling off presses in April 1999.

Building the cleanroom

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Metal fabrication and machining can bring about additional particulate threat. Also, the 1960s building designed for manufacturing had to be transformed into a cleanroom, while retaining as much of the various mechanical and electrical systems as practical. In Indianapolis, good contractors and construction personnel would not be difficult to find. Hands-on cleanroom experience, however, is sparse. That intensified the challenge to build a cleanroom in the middle of an existing manufacturing facility that is doing traditionally “dirty” work in an area of the country with a relatively low number of cleanrooms.

The overriding design principle was simplicity. The general contractor, B.J. Wirth Corp. (Carmel IN), worked with Aircom and subcontractors with a goal of designing and building a cleanroom, using low-cost conventional construction methods and materials such as metal studs and drywall, that could support a Class 10,000 environment. The project began by constructing a rectangular room surrounded by a 2-foot service chase. The walls and floor are both coated with washable epoxy and the dropped ceiling consists of 2-foot x 4-foot vinyl panels, light covers and HEPA filters. The east and west walls have 5-foot x 8-foot windows and telephones to reduce unnecessary entrance into the cleanroom.

Next, three air handling systems were put in place. The existing HVAC system was used for that area of the building along with some additional filtering and booster fans to circulate air through the 10 HEPA filters in the middle section of the room. A small amount of outside air is brought in to maintain the desired positive pressure in the room. The east and west sections of the room were each equipped with five HEPA filters that filter re-circulated air from the cleanroom. Return air vents for each system are located around the perimeter of the room near the floor.

As in the other areas of the cleanroom design, the goal was to use molding equipment that would do the necessary job with a minimal contribution to the particle count. Cincinnati Milacron Roboshot electric presses were chosen for clean, oil-free, and quiet operation. Material dehumidifying hoppers and material feeding equipment reside outside the cleanroom with supply connections in the ceiling above each press. All other utilities, such as electricity and chilled water run inside of utility columns next to each press to eliminate exposed wiring and piping that make routine cleaning more difficult.

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Finally, Aircom needed to get people, parts and equipment in and out of the cleanroom with the least possible contribution to the particle contamination. In order to do this, all necessary personnel enter and exit through a gowning room with interlocking doors. The gowning procedure includes walking over a series of tacky mats and putting on a bouffant cap, lab coat and shoe covers. All parts leaving the cleanroom for inspection must exit through a compartment leading to the QA lab. Parts are never returned to the cleanroom after being inspected in the QA lab. All other equipment or parts entering or leaving the cleanroom must go through the equipment pass-through. The equipment pass-through is a 10-foot-x-10-foot room with two sets of interlocking doors, one set of doors leading to the plant and one set of doors leading to the cleanroom. Any item entering the cleanroom through the equipment pass-through must be cleaned with isopropyl alcohol.

Contamination control

With the cleanroom complete, attention was turned to contamination control. The approach was to eliminate any unnecessary source of particle contamination. For this reason the cleanroom looks conspicuously barren. Each station has a press, a cleanroom chair and a cleanroom table. No paperwork, QA or other procedures are done in the cleanroom and nothing is stored in the cleanroom. Also, traffic through the cleanroom is severely restricted. Molds are designed to run without an operator when feasible, minimizing the greatest contribution to particle contamination in a cleanroom, people. Strictly limiting contamination at the source has, thus far, been a very effective means of controlling contamination.

Another important factor in contamination control is the education of those people working in the cleanroom. Although Aircom was fortunate to have employees with prior cleanroom experience, it is critical that everyone entering the cleanroom be trained in the correct procedures for entering and working in the cleanroom. All employees must pass a test before working in the cleanroom. It is equally critical that employees understand the importance of following correct procedures every time whether or not immediate results can be seen. For example, employees must believe that it is important to clean a piece of equipment before bringing it into the cleanroom even if it already looks clean.

In September 1999, after five months of production, particle counts were found to be below requirements for a Class 100,000 cleanroom, so Aircom had the area recertified as a Class 10,000 facility. Average counts were less than 360 particles per cubic foot “at rest,” and Aircom has future plans to build additional Class 10,000 or 100,000 cleanrooms.

David Herron is director of sales and marketing at Aircom.


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