Sand Casting in Automotive: High Quality, Low Cost, and Volume Flexibility

The automotive industry looks for high quality and low prices. Sand casting helps them have both. It’s a process that scales well, making it cost-effective for low to high volumes. It works with a wide range of metals and is capable of high finished part quality. However, it’s not appropriate for every automotive casting. Here’s information on when it is suitable.

Sand Patterns

All casting involves pouring liquid metal into a cavity where it cools and solidifies. In sand casting that cavity is formed in green or resin sand. “Green” refers to the sand containing moisture from the clay binder, and not to its color. Resin sand is where the sand is coated with a resin binder.

The cavity is made in two halves. A pattern replicating half of the part being made is placed into a box and sand is packed around it. The box is turned over and the pattern removed, leaving a cavity in the sand. The process is repeated to form a cavity replicating the other half of the part in a second box.

The two boxes are stacked together and metal is poured in through a hole in the upper box. Once it solidifies, the boxes are opened and the sand broken away to reveal the cast part.

Internal cavities in the cast part are created by placing cores in the sand mold. These are removed after casting, so the patterns must be designed to make this possible.

Beneficial Characteristics of Sand Casting

• The process can be automated for low-cost, high volume production
• Suitable for a wide selection of materials
• Green sand permeability helps reduce porosity and nonfills

Downsides to Sand Casting

• Slow cooling and solidification (sand insulates,) results in a coarse microstructure
• Minimum wall thickness is around 3/16”-¼”
• Patterns need a draft angle of 1- 2° to release from the sand, so perfectly vertical walls aren’t practical
• Parts may need considerable machining to produce tight-tolerance features like mounting holes and bores

Automotive Applications for Sand Casting

Sand casting is a good choice for a host of vehicle components. For example:

• Engine blocks –Iron is often used because it has sliding friction characteristics that let it perform well in cylinder bores.
• Cylinder heads – These require complex patterns and cores.
• Transmission cases, final drive housings and bellhousings – final drives are usually iron for vibration/noise absorption but the others are aluminum to save weight
• Brake cylinders – these are typically cast in iron and bored to size
• Wheel cylinders – typically cast iron and bored

Impro: Your Source For Automotive Sand Castings

The sand casting process is the most cost-effective production method of producing many automotive parts in materials like iron.

Impro has substantial expertise in iron sand casting for the automotive industry. If you’d like to learn more about our capabilities, contact us to schedule a discussion.