3D printing sand casting production process

Sand casting is a common casting process when it comes to the production of castings. Casting, one of the ways of metalworking, is a metalworking method in which liquid metal is poured into a casting cavity that fits the shape of the part, and after it cools and solidifies, a metal part blank with a certain shape, size and properties is obtained. However, the more complex the structure and shape of the casting, the more troublesome the mold shaping becomes. Rapid prototyping technology makes the difficulty of the molding process independent of the complexity of the physical entity to be shaped. As a result, many of the molding tasks for today's sand cast molds are performed with 3D printers, a valuable technological feature that has allowed it to grow by leaps and bounds to best fit the competitive environment of the contemporary manufacturing market.

The very hot additive manufacturing technology (often referred to as 3D printing technology) is a breakthrough in manufacturing principles, which does not require any special auxiliary tools, and is not limited by the size of the batch, can be directly from the CAD 3D model quickly transformed into a three-dimensional solid model, and the product cost is almost independent of the complexity of the parts, especially suitable for complex, with a fine internal structure of the parts manufacturing; and The manufacturing flexibility is so high that a single machine can be used to manufacture a wide variety of shapes of parts.

Rapid prototyping technology requires only 30% to 50% of the traditional processing methods and 20% to 35% of the cost of the direct manufacturing of product samples or molds. 3D printing prototypes have been widely used in the mechanical, electronic, automotive, aviation, aerospace fields, with the improvement of the technology, has brought a revolution in manufacturing.

Rapid prototyping as a casting mold can be used for sand casting, investment casting, ceramic precision casting, and plaster precision casting. The direct 3D printing of the sand mold eliminates the need for a model of the traditional process, and the geometric information of the mold CAD model (including process information such as the pouring system) precisely controls the accumulation process of the molding material and directly manufactures the mold, which is a major change in the traditional casting process.

So how do casting and 3D printing fit together?

Molds for industrial parts are made up of a whole set of combinations put together and assembled.

This whole set of molds can be completed by 3D printing technology. In the CAD file of the 3D printer, the whole set of molds is "lying flat" on the printing table.

Since the sand 3D printer has more space in the molding cylinder, the engineers were able to import many model files before printing for cost saving reasons. So before each print, the model data looked dense.

The process of 3D printing involves laying down a layer of sand, curing it with a bonding agent, and then layering it on top of each other. The material of the sand mold is quartz sand, and since resin is used to bond the sand material together, this sand is also called resin sand. The layer thickness of the resin sand material can be as low as just 300 microns (the thickness of three human hair strands).

Once printing is complete, cleanup and pickup are also required.

Let's take an example of how a turbine industrial part is made and see how this part is manufactured.

In the third step, we see the "combination of 3D printed molds and traditional molds". Because a set of molds is often made of sand core and external mold together, the structure of the sand core is relatively complex, and the external mold is relatively simple. So many manufacturers for cost considerations, only use 3D printing to produce sand core, the outer mold or use the traditional process manufacturing. Of course, it is possible to directly print and manufacture in one piece.

The traditional sand manufacturing process is generally: CAD design → process simulation → mold part production → tooling fixture manufacturing → sand manufacturing → casting. After using 3D printing, the process is CAD design → process simulation → 3D printing sand model → casting. The original often takes a month of the cycle, now just a few days to complete, greatly reducing the production cycle, and eliminating a lot of manual work.

The following are some application examples.

Advantages of 3D printing sand casting

● Time saving: short delivery lead time

● Cost saving: Build without tools

● High flexibility for quantity, shape design and variation

● Almost any complex geometry

● Complex cores can be built as a whole and rebuilt precisely

● Size: from small parts to 2000 x 1000 x 1000 mm

● No storage and maintenance costs compared to conventional mold building

● Arbitrary hybrid manufacturing method and combination with traditional techniques

● Parts / Reverse Engineering