Tour of Signicast Corporation--Hartford, WI

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  • Tour of Signicast Corporation--Hartford, WI

         On Wednesday, March 23, 2016, our annual combined ASME/SAE tour was held at Signicast Corporation in Hartford.  This year, the tour was organized and planned by SAE.  Just over eighty members toured the highly automated, state of the art facility that produces quality investment castings.

              As our group toured the plant, the guide described in detail the steps involved to produce investment castings:

    1. Creation of prototype parts—3D additive manufacturing is used to create the initial wax patterns.  Sample parts are then poured and inspection by CMM is used to verify the customer’s dimensions.
    2. Manufacture of production tooling— Several large six axis CNC machines provide in-house capability to produce the large tools for injection molding of the wax patterns.  Programming is performed in a separate area.  Tool room machinists then assemble the components.  No blueprints are used on the shop floor--computer workstations provide access to all drawings.  With the abundance of software, computers and robots, software licensing becomes a major expense.
    3. Injection molding of wax patterns--The patterns are molded similar to the injection molding of plastic parts.  Parts are then automatically unloaded and placed on conveyor systems.
    4. Assembly of patterns to sprues forming clusters—  Multiple wax patterns are assembled into one complex pattern and attached to a wax sprue with the result known as a pattern cluster, or tree.
    5. Dipping of assembly into slurry by robots— The first step (priming) is to dip the pattern clusters into a solution of fine refractory material with excess material allowed to drain off.  The next dip involves a (stucco) coarse ceramic particle slurry.  Other dipping operations may be used, and, robots perform the planned sequences.  The slurries consist of common refractory materials such as silica, zircon, aluminum silicates and alumina.  We were allowed to feel these slurries—this was a hands on/in tour.
    6. Drying/Dewax-- The coating is now allowed to thoroughly dry which can take 16-48 hours.  The molds are then turned upside down and placed in a furnace to melt and vaporize the wax patterns.  It should be noted that the mold must be strong enough to withstand the pouring and dewaxing heat and pressures, but not so strong that it is difficult to remove the ceramic mold after pouring.
    7. Burnout and preheating.  The mold is then subject to a burnout which heats the mold and removes moisture and residual wax.  The mold is then preheated to allow the metal to stay liquid longer to fill in any details.
    8. Pouring operation--  Liquid metal is then poured into the mold, either by robot or by hand.
    9. Divesting--  The shell is then removed by pressure and media blasting.  Rough and final finishing removes the sprues and cleans up the casting.                                                                                                                                                                                                                   As we toured the factory, the level of automation was impressive.  ASME Magazine recently reported that by 2025, over 45% of factory jobs will be automated.  With Signicast’s high level of automation, driverless vehicles and automated material handling resulted in a minimum of workers visible throughout our tour.                                                                                                                                                         With over eight hundred workers, forty some engineers and five foundries, all working together, Signicast is a leader in the manufacture of investment castings.  We thank the management and tour guides for their time and expertise to present a quality tour.
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