sand casting

core definition

Sand casting, also known as sand casting, is the most traditional and widely used casting method. The principle is to use molding sand (mainly composed of quartz sand, binders, etc.) to manufacture molds, and then pour molten metal into the cavity of the mold. After it cools and solidifies, the mold is broken to obtain castings.

Main process flow

Mold making: Based on the part drawing, make a model of wood, metal, or plastic that matches the shape of the casting (usually considering shrinkage allowance).

Styling:

Molding: Place the model into a sand box, fill it with molding sand and compact it tightly. After flipping the box, remove the model and leave a cavity in the sand mold.

Make the upper mold: Use the same method to make the upper sand box and create channels for the pouring system (gates, risers, etc.).

Core making: For the inner cavity or complex holes of castings, it is necessary to make a separate core with core sand and place it in the lower mold cavity.

Box closing: Accurately combine the upper and lower molds with the core, fasten them with fixtures or pressure iron, and form a complete mold cavity.

Pouring: The molten metal is smoothly injected into the mold through the pouring system.

Cleaning of falling sand: After the metal solidifies and cools down, open the sand box, take out the casting, remove the surface molding sand and sprue, and perform post-processing such as grinding.

main advantages

Lowest cost: Raw materials (molding sand) are inexpensive and reusable, and molds (especially wooden molds) are easy to make and cost-effective.

Extremely adaptable: not strictly limited by casting materials (steel, iron, copper, aluminum alloys, etc.), size (from a few grams to hundreds of tons), and shape complexity.

Flexible production: suitable for both single piece and small batch trial production, as well as large-scale mechanized production.

main drawback

Poor casting accuracy and surface smoothness: large dimensional tolerances, rough surface, usually requiring subsequent mechanical processing.

Low production efficiency: There are many processes, especially the labor intensity of shaping and sand removal, and the production cycle is relatively long.

Quality stability control is difficult: it is prone to casting defects such as sand holes, pores, sand sticking, and sand inclusions.

Poor working environment: There is a lot of dust and loud noise during the production process.

Application field

Sand casting is the cornerstone of the casting industry, suitable for almost all fields that require metal blanks, especially for:

Large and heavy-duty castings: machine tool bed, engine cylinder block, large valves, water and electricity equipment base.

Complex structural blanks: box type and frame type parts.

Ordinary castings with low requirements for surface and dimensional accuracy: various municipal facility manhole covers, pipeline fittings, and foundation components.

In summary, sand casting holds a fundamental and unshakable position in casting production due to its unparalleled cost advantages, material adaptability, and production flexibility. Although it may not be as accurate and efficient as some modern precision casting processes, it is still the preferred and most economical forming method for the vast majority of conventional, large, or small batch castings.