The use of 3D printing in sand and investment casting

Published - 17th Nov 2020

3D printing, otherwise known as additive manufacturing, can be used alongside traditional casting processes to give product designers greater design freedom and faster turnarounds in development.

When people think of 3D printing, they often think of direct metal printing techniques such as DMLS (direct metal laser sintering) and EBM (electron beam melting) which use a focused heat source to melt metal powder or wire to form components layer by layer. Whilst at face value such techniques could be seen as an alternative process to casting, in practice there is very little overlap in application.

In this article, we will look at how the 3D printing of sand, wax and polymers can be harnessed to complement existing casting processes and bring additional benefits to customers.

3D printing in sand casting

Haworth Castings specialises in sand casting, a process in which molten metal is poured into a mould made of sand, which contains a hollow cavity of the desired shape. If apertures are required within a casting, sand cores are used.

In traditional sand casting, both the mould and the core are produced using a pattern, which must be manufactured in advance out of resin. Sand 3D printing allows us to bypass this step and produce the mould and core without the need for patterns. The printer produces the mould and core directly by bonding sand layer by layer from a CAD model. This significantly reduces the time and cost required for new product development.

3D printing with sand also enables greater freedom of design, meaning we can produce highly complex mould and core shapes and, in some cases, features that simply are not possible using the traditional method.

The use of 3D printing in sand casting is beneficial for new product development, particularly where speed to market is a factor, as it reduces the time and cost associated with producing prototype parts and moving through multiple design iterations. It is also particularly suitable for low volume, highly complex components where the casting has intricate features and internal voids. For this reason, it lends itself well to applications for certain industry sectors such as high-performance automotive.

3D printing in investment casting

Also known as lost wax casting, this process is used at our sister company Investacast to produce components across a wide range of industries in a number of different alloys.

The investment casting process begins with the production of a tool from which a sacrificial wax replica of the component to be manufactured is produced. The wax is then coated in a ceramic slurry which solidifies to form a hard shell around the wax. The wax is then burned out, leaving a hollow shell into which the molten metal is poured.

By 3D printing the wax replica of the part, often in wax but sometimes in a polymer material, the need to produce hard tooling at the start of the casting process is removed. The benefits are much the same as previously mentioned for sand casting: the reduction of time and cost from the new product development process; and enabling greater design freedom.

Typically, the end to end processes for investment casting are longer than for sand casting, which makes the use of 3D printing all the more beneficial for investment casting projects with tight timelines or where the design is not fixed. It is particularly suitable for low volume, highly-complex components with intricate features.

3D printing of prototypes

Another area in which 3D printing is particularly useful is in the production of prototype component models, as an aid to technical discussions in product development.

The ability to see and handle a design in three dimensions is helpful for product refinement and decision-making, allowing designers and engineers to assess features such as radii and draft angles.

Whereas casting or machining prototypes can be slow and costly, direct 3D printing in polymer allows faster design verification and the ability to make rapid design iterations. Customers can see prototypes at an early stage, speeding the process up and allowing them to innovate more freely. Only once the design is finalised do we commit to tooling and pouring metal.

3D printing complements traditional casting

Metal casting is one of the oldest manufacturing methods, dating back more than 5,000 years. Today, innovations in 3D printing complement these traditional processes to give customers even greater flexibility.

By 3D printing moulds and cores in sand, we enable greater design freedom, reducing the time and cost of new product development, and the ability to produce complex features that would otherwise not be possible.

At Haworth Castings we are proud to combine traditional casting methods with the latest innovations in 3D printing to provide an end-to-end service for our customers. For more information please email us today at: sales@haworthcastings.co.uk or call +44 (0)1794 512685.