Eastman Kodak Company (Rochester, NY) has adopted insert molded AURUM Thermoplastic Polyimide end caps for the fuser roll assembly of the KODAK 3100 Duplicator high speed copy machines and KODAK LIONHEART Power Printing Systems including the KODAK 1392 Printer and KODAK IMAGESOURCE 92p Printer. According to Jennifer Giuliano of engineering plastics manufacturer Mitsui Chemicals, Inc. (Purchase, NY), AURUM is an extreme heat resistant thermoplastic polyimide designed to withstand high loads and high velocities at temperatures exceeding 500°F which can be conventionally injection molded to tight and consistent tolerances using high-performance injection molding machines. The AURUM® insert molded end caps are supplied by Pixley Richards, Inc, a leading custom injection molder of high - temperature thermoplastics to the automotive, business machinery, and electronics industries. The powder metal insert over which the AURUM polyimide is injection molded to form the composite end cap is manufactured by Alpha Sintered Metals.

  The end cap, also known as a gudgeon, has traditionally been an all-plastic component injection molded from a high heat resistant polyimide -- most recently AURUM. In the electrostatic-type copier, an AURUM gudgeon is attached to each end of a fuser roll core made of a thermally conductive material such as aluminum. The aluminum core is heated internally by a quartz lamp, and the actual fusing surface of the fuser roll that permanently fixes the toner to paper or transparencies is typically made of a thermally conductive polymer, such as silicone rubber. The gudgeon is responsible for transferring rotational motion and for providing support to the frame of the machine. In addition, the gudgeon acts as a thermal barrier to protect an expensive steel bearing, positioned between the gudgeon and frame, from excessive heat transfer. The gudgeon also provides a low friction, wear resistant surface to extend the life of the bearing. In operation, the gudgeon is subject to operating temperatures of 450°F, with spikes as high as 480°F, and torque levels of 60 ft lbs.

As a cost-reduction project, a high-performance metal/plastic composite gudgeon was designed in 1995 by Kodak engineers. The patent for the AURUM /metal composite gudgeon, filed in December 1995 by Allen Kass and Robert Lancaster both employees of Kodak, was issued July 22, 1997 (US Patent No.5,649891). The composite gudgeon consists of glass fiber reinforced AURUM Thermoplastic Polyimide injection molded onto a powder metal insert made of grade 303 stainless steel. The reinforced AURUM compound is supplied by RTP Company (Winona, MN), a compounder of thermoplastic materials including the RTP 4200 Series of AURUM materials. The composite gudgeon also provided a variety of functional advantages including low thermal conductivity of the metal section and extended component life. The strong bond between the AURUM and metal insert is derived from a combination of mechanical engagement and shrink fit. The AURUM section, as in the all-AURUM gudgeon design, serves as a thermal barrier to minimize heat transfer to the bearing, and as a low friction and wear resistant surface at elevated temperatures.

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  During development of the AURUM/metal composite gudgeon, approximately 200 composite gudgeon prototype samples were insert molded by Pixley Richards and supplied to Kodak for life testing in machines, with one lifetime equivalent to approximately 1 million copies. A number of manufacturing issues were addressed by Pixley Richards. Primary, was the development of a capable interface between AURUM and the stainless steel insert. Pressures, temperatures, and fill rates were adjusted to achieve the correct balance producing a solidly knit part, while not overstressing the stainless steel insert which forms a significant part of the cavity. AURUM demonstrated an ability to withstand a wide variety of processing conditions. Care was needed during these trials to ensure that the ultimate process parameters would also be capable in high-volume production manufacturing.

  Ian MacLeod, the Vice President of Engineering at Pixley Richards acknowledged, "There are limits when processing high performance materials. AURUM seems to allow you to stretch those limits better than many other performance materials." Once positive, field performance results for the first 200 AURUM/metal composite gudgeon samples were confirmed, another 800 production-quality samples were molded by Pixley Richards for field machine testing by Kodak.

  According to Allen Kass, Product Engineer for Roller Development & Manufacturing at Kodak, AURUM was selected over an extensive list of other engineering plastics, including PPA and PPS, for the all-plastic and subsequently metal /plastic composite gudgeons, "because of the good stability of AURUM when exposed to operating temperatures up to 480°F. An additional property of AURUM was its high tensile strength at room temperature and at 400°F."

  Kodak's dimensional requirements for the metal insert specified a close tolerance flange thickness and a groove perpendicular to the direction of pressing on the body of the insert. Both of these features required machining after sintering which Alpha Sintered Metals performs in-house. Alpha selected a 400 ton multi-action press, a pure dry hydrogen atmosphere was selected for sintering so finish machine operations could be accomplished economically.

  The original all-AURUM gudgeon, which was a direct replacement for a glass - filled thermoset polyimide, was molded by Pixley Richards on a 185 ton machine using AURUM processing conditions of 22,000 psi injection pressure, barrel temperatures of 730°F - 770°F, and a mold temperature of 400°F.

  These parts were made in the original thermoset mold tooling with minor modifications. Because the cavities were designed for a thermoset part, the product was not optimized to utilize the unique characteristics of AURUM.

  The AURUM /metal composite gudgeon was developed to take advantage of these capabilities. Processing requirements were dramatically different due to the requirement of the stainless steel powdered metal insert, yet the AURUM was able to achieve the final needs of Kodak. Process pressures needed to be much lower (i.e., 7000 psi) to prevent damage or collapse of the stainless steel insert and melt temperatures needed to be elevated substantially to achieve the lower pressures, while gaining good knit line strength and density. Ian MacLeod noted, "Although the process window was substantially narrowed, it is still a viable manufacturing process and will run in a trouble free manner. Few materials tolerate this range well".

  Injection molded AURUM Thermoplastic Polyimide components are utilized in a variety of other demanding applications such as automotive transmission thrust washers, check balls, and oil seal rings; wear and friction components for business machinery, industrial compressors, appliances, and power tools; jet engine and aircraft components; high-performance gears; and high-purity components for semiconductor wafer and hard disk handling and manufacturing equipment. AURUM® is also extruded as a monofilament, thin-wall tubing, wire and cable insulation, and rod.

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