Continuous mixer takes on performance, serviceability challenge.Harrison Steel Castings Steel casting is a manufacturing process in which molten metal is poured into a mold, allowed to solidify within the mold, and then the mold is broken and the solid piece is taken out. Co., a producer of steel castings for the construction equipment industry, saw a need to add a third core production line at its nobake facility in Attica, Ind. The firm decided to add a continuous mixer to produce large cores of 500-3,000 lbs. (227-1,361 kg). Harrison initially favored the design advantages of twin-screw turbo head mixers because of their record of excellent sand mix quality combined with easy cleaning and low wear. The new requirement, however, necessitated more frequent changes from silica silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. to zircon zircon Silicate mineral, zirconium silicate, ZrSiO4, the principal source of zirconium. Zircon is widespread as an accessory mineral in acid igneous rocks; it also occurs in metamorphic rocks and, fairly often, in detrital deposits. to chromite chromite (krō`mīt), dark brown to black mineral. It is an iron-chromium oxide, FeCr2O4, with traces of magnesium and aluminum. sand for numerous mold-facing and backing-sand formulations. This type of mixing application traditionally had been handled using zero retention single-screw mixers, which accommodate quick changes of mixed sand formulas. However, in the past, easy cleaning and low wear frequently were given lower priority in order to achieve faster change of sand formulation. Harrison was unwilling to compromise its objective and began discussions with engineers at Dependable Foundry Equipment Co., Tualatin, Ore. Dependable manufactures both twin-screw turbo head mixers and zero-retention single-screw mixers in addition to mixers of other designs. Harrison wanted a mixer that achieved "the best of both worlds," namely fast sand formulation changes using aggregates of dissimilar density plus excellent sand mix quality, low wear and easy cleaning. The two companies studied the Dependable Pacemaster twin-screw continuous mixers to try to find a way to accomplish faster sand formulation changes. Dependable and Harrison recognized that zero-retention mixers need more time to restart To resume computer operation after a planned or unplanned termination. See boot, warm boot and checkpoint/restart. after stopping for hand tucking or other tasks that require a pause in mixer discharge. Twin-screw mixers do not have this delay and instead offer easy turbo head cleaning and low wear. Equally important, they are well-known for good first/middle/ last sand mix quality, even with materials of dissimilar density. Additionally, by establishing a programmable logic controller See PLC. (hardware) Programmable Logic Controller - (PLC) A device used to automate monitoring and control of industrial plant. Can be used stand-alone or in conjunction with a SCADA or other system. (PLC) job record for each mold, twin-screw mixer controls became workable with new programming techniques to anticipate desired sand formulation changes. Thus, pre-reloading the sand conveyor belt conveyor belt One of various devices that provide mechanized movement of material, as in a factory. Conveyor belts are used in industrial applications and also on large farms, in warehousing and freight-handling, and in movement of raw materials. in the mixer primary arm eliminates objectionable delays and wasted sand. Select No. 002 at www.moderncasting.com/info |
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