Castings possess many inherent advantages that have long been accepted by the design engineer and metal parts user. In terms of component design, casting offers the greatest amount of flexibility of any metal forming process. The casting process is ideal because it permits the formation of streamlined, intricate, integral parts of strength and rigidity obtainable by no other method of fabrication. The shape and size of the part are primary considerations in design and in this category; the possibilities of metal castings are unsurpassed. The flexibility of cast metal design gives the engineer wide scope in converting ideas into an engineered part. The freedom of design offered through the metalcasting process allows the designer to accomplish several tasks simultaneously. These include the following:
• Freedom of design to optimize functionality and manufacturability.
• Net or near-net shape design.
• Intricate components can be produced as single cast part.
• Few restrictions on part weight or size
• Almost all metals and alloys can be cast.
• Optimal appearance.
CASTINGWELDMENT
Heat Sinks for Headlight
An OEM for a headlight subassembly was looking for an alternative to plastic for daytime running lamp and turn signal mounts. Diecast aluminum was chosen over plastic for its heat sink characteristics, which would conduct heat away from the LED bulbs. Aluminum also allowed for consistent dimensions at the bulb mounting surfaces, which were required to be parallel. The assembly also required tight tolerances for the lens hole position, which provided wiring access for the bulbs. The part needed a rigid material to hold up to component assembly and mounting.
--By Jiten Shah, president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Feature-Rich Casting Made Possible With Lost Foam
In order to incorporate all the desired components and features into a part for a new engine series for reduced emissions, an agriculture equipment manufacturer partnered with Grede Holdings LLC’s lost foam casting company in Columbiana, Ga. A lost foam-based design allowed lower cost by eliminating bolt-on components and reduced weight by significant reduction in draft angles. The overall one-piece, 97-lb. design incorporated a water pump volute, EGR passage and coolant return passage, idler pulley mounting pedestal and alternator mounting bracket, trust washer face and various as-cast passages and openings. Cast iron offered significant noise reduction, corrosion resistance and bolt torque retention compared to the alternative aluminum design.
--by Jiten Shah, president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Designers Steer Capabilities in Consolidation
Creative casting design with a sound understanding of the casting process and its limitations allowed engineers at ThyssenKrupp Waupaca, Waupaca, Wis., and John Deere to work together to consolidate multiple castings and weldments into one auxiliary drive casting for a tractor engine. The casting is a common part across multiple tractor options.
The design reduced part numbers, eliminated inflated inventory levels and successfully met limited space and weight restrictions. The supplier produced the part via vertically-parted green sand molding, which is a cost effective molding process with tight dimensional accuracy and reproducibility and good as-cast surface finish. It’s a flaskless molding process, meaning molds are created without a metal or wood frame, which improves cycle times.
--by Jiten Shah, president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and
manufacturing veteran.
Polaris Casting Heavy on Looks, Short on Parts
The Polaris Core concept motorcycle's structural frame is a one-piece casting and the winner of the 2009 Casting of the Year contest sponsored by Metal Casting Design & Purchasing. The part incorporates the gas tank, air inlet, air intake box, electrical routing, and seat and motor mounts. It was converted from a steel fabrication of more than 30 parts. The 51-lb. aluminum casting reduced the weight of the assembly by 35%.
--by Jiten Shah, president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Instrument Panel for BMW Hits Right Notes
The 12.5-lb. diecast magnesium instrument panel cross car beam for BMW's X5 SUV was converted from an engineered plastic and steel stamped fabrication weighing more than 25 lbs.
--by Jiten Shah, president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Cast Cradle Throttles Steel Design
This semi-permanent mold casting is welded to four aluminum extrusions to form the engine cradle for a Cadillac CTS. The A356 aluminum part achieved a mass reduction of 40% and consolidated a 32-piece steel design into one component. By carefully positioning cores in metal dies, the 33.5-lb. part achieved 0.16-in. wall thickness, providing a weight savings of 2.2 lbs. over previous designs and making welding easier.
Scroll over the arrows on this interactive map for information on each design element.
--by Jiten Shah, president of Product Development & Analysis (PDA) LLC, Naperville, Ill., and a 25-year casting design and manufacturing veteran.
Fab to Aluminum Casting Conversion for Computer Processor
This article was originally published in the March/April 2009 issue of Engineered Casting Solutions.
Pixellexis, a developer of high speed processing units that boost the performance of computer workstations, wanted to make a splash with its next foray into parallel processing. The equipment would be targeted to the movie industry, which uses parallel processing to work with the large files associated with digital film and images. That the processing unit had to work seamlessly was a given, but Pixellexis wanted its LexiGrid series to look the part when it was up for audition.
The night that precipitated a conversion to casting for the Agri-Speed Hitch was icy. But it was a fire that was the catalyst.
With bitter cold blowing outside, the hitch’s manufacturer saw its facility go up in flames when a continuously running furnace started a small fire. The high winds of the storm intensified the flames once they started, and before long the small agricultural firm lost almost everything, including the tooling and inventory for its farm equipment hitch.
When it comes to steel, casting offers benefits such as design flexibility, isotropic properties and welding ease over fabrications. Making these benefits work is simply a function of understanding steel castings and fabrications.
The major decisions and steps needed to convert a nine-piece steel weldment into a one-piece casting for a cement mixer truck are detailed in this casting conversion tutorial.
By Michael Gwyn, Advanced Technology Institute, North Charleston, South Carolina and Alfred Spada, Executive Editor
How do you spot a conversion opportunity for casting? On the floor of your manufacturing and assembly operation, you undoubtedly have seen components currently made up of several stamped, wrought or machined metal parts. Could they be redesigned to a single cast metal component for improved performance? How do you determine if the potential performance gain or cost savings would make the redesign viable?
The choice of whether a component is best manufactured as welded, assembled, machined or cast component is based on the component’s geometry, production costs and requirements in application. This article looks at these issues and provides a framework for analyzing weldments and assemblies as possible conversion candidates.
WELDMENT
