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Simple Invention Speeds Up Metal Investment Casting Process
New process cuts time by at least 33%
Shells being heated to pour metal
Shells after removing wax
pattern in autoclave
• Faster cycle time for dipping shell• Can build a shell with 6 layers plus a seal coat in an 8 hour shift using 1 hour cycle time• Need lots of air flowing over the shell between coats• Appears to be easier to immerse tree into fluidized bed with
AMS additive• It is possible to reduce cycle time to 30-45 min
• Characteristics of the shell after 1 hour when it is ready for redipping
• Surface of the shell is hard• Shell still contains moisture• We say the shell is dippable: we do not say the shell is dry• Shell materials does not peel off in the slurry when the shell is redipped
• Time line to build shell, remove pattern and pour metal – 1 hour cycle time• Day 1
• Build shell in one shift• Dry shell overnight
• Day 2• Remove pattern• Heat shell and pour metal
Shells after metal has been poured
Metal part – before and after final finishing processes
Dan McGuire1 and Eric Hellstrom2
1University of Wisconsin-Whitewater, 2University of Wisconsin-Madison and Florida State University; Patent # 7,278,465, Support from WiSys
Clinton L. Atwood http://www.wtec.org/loyola/rp/10_01.htm
Wax patterns with and without 1st coat
Applying stucco in fluidized bed
Summary• We have developed a new, simple, inexpensive
process that drastically decreases the time needed to build a shell for investment casting.
• The heart of the invention is an amorphous mineral silicate that is added to the stucco.
• No change in other materials and the fabrication methods
• Time reduced by at least 33%• Cost reduced by at least 25%
• Same basic process currently used for metal investment casting. • Useable with fluidized bed and rainfall method for wax, Styrofoam, and all burnable patterns
• Major modification is to the stucco:We add amorphous mineral silicate (AMS) plus an organic (e.g., corn starch) to the stucco. • No changes in slurry• AMS and corn starch are mixed
with stucco• Can be used with all standard
stuccos - zircon, silica, alumino-silicate, alumina
• Can use additives in all stucco coats• Some companies choose not
to use it in the face coat- primary stucco because the first layers dry so quickly
• No changes when applying stucco with fluidized bed
• Add one step before redippingwith rainfall method to remove
loose stucco
• Time line to build shell, remove pattern, and pour metal – 45 min cycle time • Day 1= 12 hour shift
• Build shell• Remove pattern• Heat shell and pour metal
• Other factors• Shell is lighter so it takes less heat to bring shell to pour temperature• Does not use any drying accelerants, like alcohol• Green, environmentally friendly, non-toxic• Potential to recycle shell• Shell breathes• Shell has larger Modulus of Rupture (MOR) than traditional shell• Compatible with all standard metals
• Light alloys – aluminum, brass, bronze• Cast iron• Stainless steels
• Modified shell breaks off casting more easily and in larger pieces than traditional shell
• Cost should be about 25% less expensive than traditional shell
For licensing contact:
Paul PucciWARF608-262-4924 ppucci@warf.org
For more information on the process see:
www.FoundrySolutions.net
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