Castings

Gravity/Permeanant Mold castings

Overview:

Gravity die casting is where molten metal fills up a mold cavity, with the primary force on the molten metal, as the name suggests, is gravity. Generally the mold cavity is made of a steel, where sand or steel cores can be used to create more intricate and complex shapes.

Tooling costs tend to be lower for gravity die-cast components, and in addition the level of porosities are lower as well. However per unit costs tend to be higher since the wastage of material is also higher. Full simulation capabilities can be employed if necessary. Draft angles are crucial to the manufacturability of the part. Our engineers can help you design for manufacturability.

Specification:

Aluminum: LM25/A356, A319/LM4, and others, up to 100 lbs

Infrastructure and Quality:

Testing equipment: spark electrode testing,

Machinery List: furnace capacity, corebox size/weight, molding machine

Sand Casting

Overview:

Sand castings are just what the name suggests, a casting where the cavity is made by sand. The molten metal is poured into a cavity made of sand. Generally the surface finish is poorer than other casting methods and the final cast material will have a higher silicon content.

However, sand castings have the most competitive per unit cost and the most competitive tooling cost as well. Shape forms are generally simpler and most sand castings are followed by secondary processes.

Specification:

Similar to gravity die casting specs

Infrastructure and Quality:

Testing equipment: spark electrode testing,

Machinery List: furnace, pattern boxes

Pressure Die Casting

Overview:

Pressure die castings, as the name suggests, a die casting form where the pressure for the material flow is created by a mechanical means, generally a plunger. The die cast components have a very good surface finish, and can be made relatively inexpensively on a per unit cost basis. However, since the material is under pressure sealing of the tooling is most important. Hence the tooling cost for pressure die castings are among the highest.

Since a good seal is important, the air within the cavity has limited ability to escape when the material is pressed in, hence the level of porosities in pressure die castings are higher than other castings techniques. Our engineers can help you design for manufacturability.

Additionally pressure die castings require large machines and capital, where as the other casting methods may not.

Specification:

Needs aluminum with higher silicon content

Infrastructure and Quality:

Testing equipment: spark electrode testing,

Machinery List: up to 1200 ton injection molding, fem analysis of die filling/underfilling

Investment Castings

Overview:

One of the oldest casting methods. A wax mold is made and placed in a sand or ceramic plaster outer case. The wax is then melted once the outer mold has hardened, upon which the material to be casted is poured. When the material solidifies, the plaster is broken and the part is made.

With investment castings, the unit cost is significantly higher than other casting methods. The limitation on investment is determined by the length of travel of the material and the maximum cross sectional area.  The tooling cost of short runs can be made more competitively, however larger volume tooling costs are higher.

One important consideration to keep is with investment castings, the surface finish is largely superior to other casting methods.

Specification:

Various steels, stainless steels, and non-ferrous compounds

Infrastructure and Quality:

Testing equipment: Varies—based on requirements

Machinery List: — just molding machines and furnaces

Grey and Ductile Iron Castings

Overview:

Ductile iron is a relatively new form of castings, where magnesium is added to force the nodulation of carbon. Ductile iron has a larger carbon content in the form of nodules followed by a primarily ferrite matrix. Ductile iron grades generally trade off the strength to the percent elongation. The purity of the steel/iron that is used to make the ductile iron can have a large impact on the quality of the casting.

Generally ductile iron castings have test bars that are poured with each heat, and these can be used to identify the casting quality. Control of the melt is extremely important, as under-cooling can cause various negative formations to occur including dendritic and kisch type forms.

Grey iron castings are an older, cheaper form of casting. A foundry that pours ductile iron may also pour various grades of Grey iron. Metallurgical composition control is less severe for grey irons. However, the cost of grey iron is lower than that of ductile iron.

Specification:

350/22 – 700/2

Infrastructure and Quality:

Testing equipment: tensile testing machine, nodularity check microscope, spark chemistry measurement, brinnel hardness tester, izod impact testing.

Machinery List: furnace capacity, load tonnage,

Steel Castings

Overview:

If weldability is of concern, steel castings offer an excellent alternative to ductile iron. However, due to the nature of steel and the multiple phase changes that the casting goes through in the solid state, a higher rate of defects can occur than grey or ducile iron castings of the same design.

The key for a good quality steel castings is making sure the cooling rate is uniform throughout the casting process.

Specification:

350/22 – 700/2

Infrastructure and Quality:

Testing equipment: tensile testing machine, nodularity check microscope, spark chemistry measurement, brinnel hardness tester, izod impact testing, x-ray analysis.

Machinery List: furnace capacity, load tonnage,