Gear trains used in Lexmark's Optra family of laser printers have 11 gears molded from DuPont™ Delrin® acetal resins. The gears drive the printer's toner drum, fuser rollers and other rollers that move paper or other media through ink transfer and fusion operations and finally to an output tray.
The printers use eight spur gears, both compound and single-face types, and three highly loaded helical gears located near the printer's motor. One of the helical gears meshes with a stainless steel gear cut in the motor shaft. Other gear meshes in the printer are plastic to plastic.
Smooth, reliable operation. Precision molded to close tolerances, the gears run freely, quietly and without vibration that can cause imaging imperfections, according to Lexmark. The natural lubricity of Delrin® minimizes friction, reducing heat levels and power requirements.
Environmental resistance. Thanks to the moisture resistance, heat resistance and thermal stability of Delrin®, the gears perform reliably over the long term in hot, humid environments. Temperatures inside the printers range up to 60°C (140°F).
No maintenance. The low wear of Delrin® virtually eliminates gear replacement over the projected life of the printers, according to Lexmark.
Technical assistance. DuPont engineers assisted Lexmark in material selection and part design, saving on development costs and time.
Materials Selected and Why
The resins used are Delrin® for the spur gears and Delrin® for the helical gears. Both fill needs for dimensional stability, high strength, low friction and wear, and high molding productivity. For the helical gears, Delrin® meets more stringent requirements for low wear and friction in contact with both stainless steel and plastic gears at high PV loads.