Faster to a cast part without a model: what is 3D sand printing?

Everyone is talking about 3D sand printing. It combines the traditional casting of sand molds with the direct additive production of molds in a 3D printer. Completely without a model.

This means that small batches in particular can be cast much faster, more efficiently, with less use of resources and often simply better.

For foundries, this opens the door to a new future. For all those who work with metal, it gives them the opportunity to discover a whole new side to casting.

“Printed Casting”: Printing a mold instead of a component

The principle and advantages of 3D printing no longer need to be explained to anyone. The technology has long been associated with more than just prototypes and non-critical individual parts. High-performance metal components are now also routinely produced using additive manufacturing. However, this is still only economical for smaller quantities. One of the most exciting developments in 3D printing is therefore the advance of hybrid manufacturing processes that combine the advantages of traditional and additive methods. This can result in hybrid end products or simply improve traditional processes through the strategic use of 3D printing. 3D sand printing does the latter. By printing molds directly in bonded sand, the expensive and slow upstream model making process is completely eliminated. The sand printer is located either directly in a foundry or at a service provider who prints molds “on demand” that are cast at a different location.

Off to the Job Box

The most common 3D sand printers have a printing area, the “job box”, with a build volume of 150 to 8000 liters and a length (usually the largest dimension) of just under one to 4m. Either individual large molds and cores or densely packed many smaller molds can be printed in this installation space. The CAD file of the workpiece to be cast is uploaded in order to optimize the design of the mould and cores for 3D sand printing. The print file is then fitted into the build volume, together with other parts if necessary, to ensure maximum utilization. The printing process itself is a binder jetting process, i.e. the original 3D printing principle, in which a binder is selectively applied to a surface, similar to an inkjet printer. This surface is a layer of powder (or sand) that is bonded with the binder jet. In this way, a workpiece, tool or mold is created layer by layer from the powder or sand bed.

Precise molds, proven casting

Various sands and binders, each with specific properties and advantages, are available for 3D sand printing (and have proven their worth). After printing, the molds and cores are freed from the unbound sand and assembled and prepared for casting. They are then cast in exactly the same way as traditionally produced sand molds and are indistinguishable from other castings in terms of their mechanical properties. 3D sand printers have a maximum theoretical “resolution” (e.g. 600 dpi). The actual resolution depends on other factors. As a rule, this high resolution means that sand printing processes can achieve greater precision and dimensional accuracy of the molds than would be possible with traditional models. The usual advantages of additive manufacturing also apply to sand printing: a high degree of design freedom, a short time to the first component, cost savings in tooling and a largely digital process.