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Engineering Plastics used in lenses are now used in aircraft and automobiles because of their outstanding reliability. Engineering Plastics offer many advantages over metallic materials in addition to being substantially lighter in weight. Let's compare characteristics of the two major raw materials used in optics chassis; metal and plastics.
Plastics provide outstanding characteristics in workability, adiabatic efficiency, thermal resistance, chemical resistance such as anti-acid and/or alkali, etc. Lightweight is another important benefit of plastics. While the specific gravity of aluminum is about 2.8 against water, plastics is about 1.3-1.4, almost half of aluminum.
While plastics render these ideal characteristics making them useful for so many applications, conventional plastic materials had one drawback -- strength. Engineering Plastics have thus been developed to provide significant strength for industrial and commercial applications, thereby overcoming the prominent weakness of conventional plastics. Engineering Plastics are now widely used in sophisticated products ranging from driving mechanisms and gears in high-end audio equipment and VCR's to chassis of almost all racing cars including those used in "Indy 500" that is deemed to be the most severe race requiring the highest level of endurance. Engineering Plastics provide the same and often times more durability than metallic materials, and they do not rust, nor make noise by friction.
In addition, Engineering Plastics provide the benefit of "self lubrication" that makes their surfaces naturally smooth and slippery. This eliminates the need for lubricating oils, and brings a great advantage in constructing optical products like lenses. Obviously, a problem such as oil scattering inside the lens barrel can be avoided. Unfortunately, no material can be perfect in every respect.
Engineering Plastics are high-performance materials, developed because of technological needs to go beyond the boundaries of conventional plastics. In other words, Engineering Plastics were developed as a result of huge R&D investments and use of highly advanced technologies by raw material manufacturers. Those expenditures are naturally reflected in the costs of Engineered Plastics. While the cost of conventional general-purpose plastic materials is about 200-300 Yens ( US $0.80-$1.10 per pound) per kilogram, that of Engineering Plastics is many times more. However, a mere comparison of costs at raw material stage is not appropriate. It should be compared on a fair playing ground, i.e. a total cost of processing one component machined from metallic material versus one processed from Engineering Plastic material.
Machining a sophisticated-shaped component from metallic material requires many more phases of processing and is much more time-consuming, especially when stringent adherence to given tolerances is required. Conversely, the components made from Engineering Plastics can be made automatically, one after another, in a method called "Injection Molding" as long as metallic toolings (molds) are made with sufficient accuracy.
When the component is small enough, ten to twenty pieces can be made in one shot, several shots per minute, efficiently and automatically. However, in case of lens parts, because of very high accuracy, one piece can be made in one shot. Manufacturing, with accuracy, and without the need for finishing processes, becomes possible when Engineering Plastics and advanced Injection Molding technologies are combined.
So, even if costs of raw materials are high, the total manufacturing cost will ultimately be reduced by the use of Engineering Plastics. The engineering capability of injection molding and the degree of accuracy of molds used are key to successful use of Engineering Plastics.
We at Tamron have our own factory which is specialized and exclusively engaged in fabrication of metallic molds thereby ensuring that complicated-shaped components in Tamron lenses are high quality and accurate.
Many of the Engineering Plastic components used in Tamron lenses are made of Poly-Carbonate materials. Poly-Carbonate is an ideal raw material for making precision parts because of its ability to provide stabilized dimensions necessary for parts production. For a long time, its use in consumer products had been withheld due to the need for high temperatures in processing. However, this problem has been solved by mixing various chemicals to make the poly-carbonate at lower temperatures. Today, Engineering Plastics (Poly-carbonate-made components) are used in helmets, camera bodies, lens barrels, gears in watches, racing cars and spaceships to name just a few applications.
Tamron's advanced technologies in the field of Engineering Plastics are integrated with advanced Aspheric technology and other superior optical designs. All of these are packed into recent Tamron CCTV lenses.