Riding the railsRiding the rails

When West Pharmaceutical Services set up a Class 10,000 cleanroom at its operation in Stolberg, Germany to produce infusion bottle closures, it wanted a stable process from end to end. The closures use a new design for the polyolefin infusion bottles that have steadily grown in popularity over the last few years.

Departing from previous multipart closures, West’s one-piece design greatly simplifies downstream handling and sterility maintenance. The closure consists of a rigid shell of HDPE or PP and two sealing zones of TPE through which needles can be inserted when the closure is in use. The shell is molded in one machine, and then transferred by robot to a second machine where the TPE is molded onto it. The TPE is then covered by an aluminum seal to guarantee sterility. To achieve these benefits, all production activity from molding to the hermetically sealed final packaging has to be done within the cleanroom environment.

One might think that this requirement dictates that all the machinery needed for molding, inspecting, and packaging the closure must be located within the cleanroom. Well, not quite. West is using an increasingly popular approach to holding sterility in a molding cleanroom: Only the clamps of the injection machines are inside the cleanroom.

The Krauss-Maffei C Series machines feature a cantilevered clamp area in their standard configuration. Since there is nothing under the clamp, inserting the clamp end through a wall opening is easy. The design also allows many options for part removal, whether by robot, conveyor, or dropping. West decided to mount the injection machines on rails so the clamp could be easily removed from the cleanroom for mold changing and maintenance.

The airlock seal around the molding machine is very secure when the clamp end is in the cleanroom. It is equally, if not more, secure when the machine is withdrawn. An oversized nose panel on the clamp end forms a tight seal against the wall. The overpressure maintained in the cleanroom keeps dust from entering while the clamp is moved in or out. During operation, the control panel swivels to face into the cleanroom.

The investment West Pharmaceutical made to keep the entire process within the cleanroom was substantial, but it earns dividends every day. The closures do not have to undergo a separate cleaning process before being packaged, since all is done within the cleanroom. When the hermetically sealed packages reach the plants where they will be filled, they can be unpacked and used under sterile conditions, again avoiding a separate cleaning operation.

Editor’s note: See “First Moldmaker, Then Molder, Then Cleanroom Expert,” September 2002 IMM, for another report on cleanroom infusion bottle caps.