For the manufacture of Injection Moldings under clean-room conditions,  special  precautions have to be taken to meet the requirements of the various cleanliness classifiations. Division into classes of cleanliness between 1 and 100,000 is standardized. The number indicates the permissible number of particles. According to federal standards, a class 100,000 clean room, for instance, will have been tested and certified to contain no more than 100,000 0.5-pm particles per cu ft (0.028 cum) of air, and no more than 700 5-um particles per cu ft. A class 10,000 rating means no more than 10,000 0.5-pm or larger particles per cu ft, and no more than 65 5-um or larger. Class 1,000 and 100 clean rooms are rated according to similar criteria.

           Fresh outdoor air contains about 1,500,000 particlesku ft. A typical hospital operating room is a class 1,000 clean room.

            Most Injection Molding clean rooms, if they are rated at all, are in the class 100,000 range It depends on the products being molded. Injection Moldings manufactured under clean room conditions are used in various sectors of the fabricating industry. Examples include electronics, pharmaceuticals, and foodstuffs industries, biotechnology, and medical applications, as well as aeronautics and aerospace.

            Basically, there are two possibilities for the fabrication of injection moldings in a clean room: (1) Either the machine is installed and operated totally within the clean room and the product packed next to the production line, or (2) clean-room conditions are applied only in the working area of the machine. In the latter case, the cost is lower, but the interfaces needed for handling the injection molding parts and mold changes are critical.

            IMMs have to be constructed so that contamination, wear, and leakage are minimized. In  fact, these  conditions  cannot  be  eliminated, but by careful machine design they can be kept to a very low level. Since the clean room depends on air circulation, the machines have to be built so that good air circulation is possible in the working area between the mold and injection unit. Further more, no soiling and only a small amount of wear should occur in this area.

            In addition, the injection mold has to be designed in such a way that it meets
the extremely high cleanliness requirements. Normally required  greasing of dowel pins,ejection mechanisms, and core pulls is not possible, since the contamination and wear generated would neutralize the clean-room conditions. However, if special materials and dedicated know-how are used, the molds can be run dry, that is, without external lubrication.
            If  parts have to be packed without handling next to the machine, removal by robot (Chap. 10) is essential. Robots are normally installed above the mold. Any abraded particles will therefore fall directly into the mold and lead to contamination. This means that robots also have to meet stringent cleanliness and minimal abrasion requirements.
            Raw materials (virgin or recycled) that are to be used for injection molding under clean-room conditions must themselves be produced under these cleanliness conditions. Only a few material suppliers offer such materials. Special testing and careful packing in vacuum-tight containers are essential if processing under clean-room conditions is to be problem-free.
            All  auxiliary  equipment  (Chap.  10) required for production that affects clean-room conditions must come up to the same high standards. This applies especially to cooling and heating equipment; conveying devices; and all pipe, tube, and other couplings. Products must be protected by reliable special packaging. As soon as possible after molding, the parts must be packed in containers so as to exclude subsequent contamination.
            Release agents should never be used during clean-room processing. Every molding should be fully documented  with information about particle level during production, temperature of feedstock materials, purity of batch  (determined  on batch samples), and injection molding conditions during production. The customer should receive these data in the form of an enclosed quality certificate (Chaps. 12 and 13).
            As demands for parts molded in a clean-room environment increase, more molders are becoming interested in clean-room production and particularly in how IMM features influence cleanliness. As an example, particles can be monitored and filtered, but the oil and grease thrown into the air by IMMs can become a problem. Hydraulic-oil mist from the oil storage tank, hydraulic cylinder, or toggle mechanism is the machine’s biggest potential polluter. Oil and grease are needed for machine operation, but cannot be allowed on molded parts. Oil mist can be reduced by sealing the oil storage tank and venting excess mist outside the room. The entire tog-
gle mechanism can be enclosed to eliminate drippage that ordinarily would fall from the toggle joints to a machine’s base. Full-drip trays can be placed under all manifold and hydraulic components to catch any oil that is lost during maintenance.
            Other special features can be incorporated in the machine to minimize  the throwing off of particulates. Greaseless nylon bushings and shoes for the movable platen can be used to cut down on grease contamination with-out sacrificing performance. Totally enclosed fan-cooled motors can help minimize dust in the area of the molding machine. The coils of a standard electric motor are open to the air and collect dirt that can be blown into the room when the motor is started. An enclosed
motor will collect less dirt.
             Because the maintenance of a clean atmosphere is so expensive, clean rooms have to be as small as efficient operation will allow. Machines are placed close together, which generates annoying levels of heat and noise, if not actual part contamination. Heat should be reduced both for comfort and to maintain the
balance of cooling, filtering, and humidity in the room. The machine’s barrel is the major contributor of heat, although the press’s motor and hydraulic system contribute  to the problem, A thermal blanket around the barrel will help contain the heat, or a heat shield can be used and incorporated into a system to vent the heat outside the room. The major source of noise is vibration from motors and pumps resonating in the machine base. This vibration can be reduced by securing motors
on rubber mounts and connecting pumps to the base with a rubber hose instead of metal pipe.

             Advances in microprocessor technology along with mechanical design modifications have improved clean-room molding productivity. Programmable  microprocessor controls can continuously monitor the temperatures, pressures, and timing under which a piece was molded. Molders of pharmaceutical pieces and food packaging are required to provide government agencies with documen tation of molding conditions, and other molders may be required to do so in the future
Machine controls equipped with linear po tentiometers to monitor distances, pressures and flows can give a molder hard-copy documentation of injection and clamp settings This printed record can fulfill the FDA’s GMP (good manufacturing practices) obligation and allow the fast and accurate setup of repeat runs of delicate precision parts. 
             IMMs designed for clean-room use are usually identifiable by their   stainlessstee gates and white paint. These cosmetic additions make the machine easier to clean, an advantage whether or not the machine is in clean room. Molders of electronic parts and food packaging often choose to use machine with clean-room features to keep their molding shops clean even if they do not maintain any areas that have clean-room certification. For these molders, the decision to operate a
clean-room shop is based on the expectation of profitability. 
             The complete package of clean-room options described  above can add surprisingly little to the cost of an injection molding machine-usually  less than 10%. The number of clean machines will continue to grow as more molders are able to make these design features work for them.