Sand Casting for Commercial Vehicle Applications
Components used in commercial vehicles must have strength, toughness, and a little ductility. Good heat transfer properties and low density are bonus factors. These requirements push part designers to the family of cast iron alloys, and this is a metallurgy where Impro can help.
Impro has the ability to sand cast a wide range of cast iron alloys, producing parts weighing up to 1,200 pounds and 60” x 47” x 23” in size. (Larger parts are possible at low production rates.) Here’s more about our capabilities, processes and expertise.
Cast Parts for Commercial Vehicles
Commercial trucks, agricultural vehicles and construction machinery all use large numbers of castings. Brackets of various types, housings, flywheels, wheel hubs and knuckles are just a sample. These must be rugged enough to survive thousands of hours use, high loads and extreme climatic conditions. Those used in or around the engine and transmission should also have good thermal conductivity and ideally, some acoustic dampening capabilities.
Two challenges for manufacturers of these parts are their physical bulk and the low, (relative to automotive,) quantities required. Part size and weight, which can be several times larger than automotive components, complicate handling and dictates the use of significant larger machinery. Relatively low quantity production makes it difficult to justify automation. Together with the larger volumes of metal needed, these factors tend to increase production costs.
In most cases the best material for meeting these toughness, mass and durability goals is cast iron. Cast iron takes three main forms:
- Compacted Graphite Iron (CGI – vermicular graphite iron)
Gray iron is of limited value in commercial vehicle applications, as it lacks ductility, which makes it very brittle. Ductile iron overcomes this problem, but has less dampening capability and lower thermal conductivity. (High SiMo-Ductile Iron, High Nickel Ductile Iron, and Austempered Ductile Iron offer improved properties for some applications.)
CGI falls between gray and ductile iron. It’s some 75% stronger than gray iron, and 75% stiffer. It’s also lighter, which is useful in vehicle applications.
Ductile iron and CGI are produced by “inoculating” the molten metal with magnesium immediately before pouring. This turns what would otherwise be flakes of graphite into nodules that don’t have the same propensity to initiate cracks.
Sand Casting Commercial Vehicle Components
As sand casting uses inexpensive patterns to form the mold cavity in sand, it’s a process suitable for small to medium quantity production runs. Costs are reduced further by using green sand, (technically, bentonite clay,) rather than resin sand, although surface finish and overall precision are not as good.
Patterns must be designed specifically for the alloy being cast, as shrinkage rates vary. (CGI shrinks more than gray iron, though less than ductile iron.) Cores, used to form internal features, must be designed with the same points in mind.
Impro’s Commercial Vehicle Capabilities
Impro operates foundries with an extensive range of sand casting equipment in Mexico and China. Both green and resin sand processes are available. Impro casts gray, ductile and CGI alloys.
Levels of automation vary in relation to flask size and production rate. Castings weighing up to 16,000 pounds and occupying a volume of 165” x 126” x 39” are possible by pit pouring, albeit at low rates of output.
Complimenting our sand casting operations, Impro also offers an extensive range of precision machining services. With these we can provide a total manufacturing service, from casting to delivery of machined components ready for assembly.
Contact us to learn more about our commercial vehicle component sand casting and machining capabilities.