innovations CASTING
outer edge to gain more material in the center for the pouring channel. “The pouring angle had to be
very low to prevent the liquid metal from hitting the diameter core with velocity and therefore create splash- ing causing defects in the casting,” Schweisthal said.
Piad also suggested shortening the length of the 15 cooling fi ns to avoid fi lling problems. T e fi ns in the fi nal design were given a thickness and depth that allowed each to be fi lled without fail. “T e sections of the die which form the cooling fi ns represented a special
challenge,” Schweisthal said. “T e core packet needed to be designed in segments to allow venting of each fi n in the die. Without proper venting, the fi ns would not fi ll.”
For more information on the permanent mold process, visit
www.piad.com.
New Aluminum Design Achieves Lighter,
peake, Va., for a marine exhaust pipe. “T ey were asking for the world,”
A
C Foundry, Battle Creek, Mich., had its work cut out for it when it received a quote from Volvo Penta, Chesa-
said Brian Shaughnessy, the metal- caster’s plant manager. T e two-piece aluminum water cooled exhaust pipe for catalyzed engines was converted from a three-piece non- catalyzed cast iron exhaust system. T e fi nal cast piece produced by AC Foundry met environmental standards, reduced the component’s weight and eliminated a gasket, a potential leak point. T e casting, a universal part for
Catalyzed Exhaust Pipe For Marine Engines to design because of its complex re- quirements, such as a thick core coupled with thin outer walls and heavy sections that were diffi cult to manipulate. AC Foundry had to perform numerous simulations and experiments before pro- ducing the fi nal design, project engineer Shane Sovia said. “It was an extremely diffi cult learn-
ing curve for both of us, with a lot of stress and a lot of time not knowing if it
three diff erent marine engine plat- forms, has a 19 x 7 x 8.5-in. envelope and weighs 12.1 lbs., an overall 38-lb. weight reduction. Lower weight improves a boat’s acceleration, reduces time to plane out and increases top-end speeds while consuming less fuel. An emissions law passed in Califor- nia in 2008 left Volvo Penta needing to catalyze its boat engines and control the temperature of its exhaust systems. Catalyzing a boat engine helps reduce the amount of exhaust emissions released into the environment. From previous tests in the industry, alumi- num proved to be the best material for the job. T e pipe now meets new emis- sions standards. After searching for metalcasting
facilities throughout the world, Volvo Penta decided on AC Foundry due to its willingness to take on the project and ability to do permanent mold, semi- permanent mold and sand molding. T e casting proved to be challenging
The catalytic converter works (from top to bottom) to reduce the amount of exhaust emissions, hydrocarbons and nitrogen oxides released into the environment.
50 | METAL CASTING DESIGN & PURCHASING | Sept/Oct 2011
was even possible,” Shaughnessy said. T e customer wanted a minimum amount of core prints on the casting to avoid warranty claims and improve the part’s appearance. (A core print is a pro- jection that attaches to a pattern to form a recess in the mold at a point where a core is to be supported.) T rough casting geometry, the fi nal design had only two core prints that required plugging in the assembly process. To eliminate an isolated heavy section, the oxygen sensor boss was redesigned through geometry incorpora- tions in the pipe core to minimize the amount of aluminum in that area. Gating, the portion of the runner in a mold where molten metal enters the casting, was also incorporated into the cores. T e project made AC Foundry more
conscious of the fi ner details of the casting process necessary for complex designs, such as keeping core and mold sands to specifi cations, meeting specifi c temperatures and sand moisture, and controlling pressures. T ese processing techniques overcame fi lling, core gas evolution/venting and solidifi cation is- sues that arose from the casting’s heavy section and large surface areas. “It was a tough development pro-
cess, but now that we [completed] it, we have a unique environmental innovation that gives us an advantage in the marine market that no one else has,” said John Marsh, project manager and engineering administrator at Volvo Penta. Since the casting is universal to
three engine platforms, Volvo Penta’s production and assembly effi ciency has increased.
For more information visit
www.acfoundry.com
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