With origins in Bronze Age China, sand casting is one of the world’s oldest fabrication processes. Today, it’s valued for its versatility and its ease of use for complex parts and short production runs. The sand-casting process starts with a mold made of compacted sand and special materials that help it retain its shape. Molten aluminum is then poured into the mold before it’s allowed to cool completely. There’s more to the process, though, and we’ll discuss it below.
Pattern Creation
Before aluminum casting can be done, a pattern must be made. Most are composed of metal, plastic, wood, or plaster, but other materials may be used depending on the project’s requirements. The pattern is an exact replica of the finished part’s exterior, so it will include a dimensional allowance for shrinkage. When a cast is hollow, it may include internal patterns that leave cavities in the finished product. These are typically made of collapsible, easily removable materials.
Mold Construction
The next step in the sand-casting process is to build a mold using sand that can withstand high heat. Also known as refractory properties, these qualities allow for faster drying and easier part removal. In most cases, a bonding agent such as clay is mixed into the sand, which allows for more complicated castings. The materials are stabilized with chemical binders or high heat, surrounding the pattern pieces. Molds are also created by machining sand blocks, which is common in product development and the fabrication of rarely used parts.
Metal Pouring
Next, the molten aluminum is poured into the mold. This step is the riskiest part of sand casting, which means it’s essential that the caster follows all safety recommendations. Molten metals are poured carefully and slowly into the sand mold. It’s important to fill the mold in a single pour so the aluminum cools evenly and product defects are minimized.
Part Removal
Once they’ve cooled, finished parts are removed in what’s known as a shakeout. Here, the sand mold is broken, and its fragments fall away before they’re collected and saved for future reuse. Some castings use harder materials, so these molds must be cracked or blasted open with a pressurized stream of water.
Cleaning and Finish Work
Finally, it’s time to finish the job. A caster removes gates, runners, and other components from the product and begins grinding or sandblasting if required. These finishing steps strip away extra metal and leftover sand. If a product must meet strict tolerances or dimensions, detailed machining may be necessary. In some instances, non-destructive product testing is performed before the finished parts are sent to the customer.
Quality Sand Casting in Ohio and Indiana
Sand casting is a cost-effective, simple, and versatile option to produce metal parts. We have the equipment, tools, and skills to provide superior quality and service throughout the process. Contact us online or call today to discuss project specifications or to learn more about our sand casting services.
