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The high-complexity sand core for a water-jacket casting, 3D-printed by voxeljet using its cold-curing inorganic binder (cold IOB) technology.

Cold Inorganic Sand Bonding for 3D Printing

Aug. 1, 2023
Sand printing processes for molds and cores continue to attract interest with new functions and capabilities – now including the environmental, precision, and other advantages that foundries attach to inorganic sand bonding.

Sand printing has made considerable advances to become competitive for higher-volume core and moldmaking operations, and the recent introduction of a new capability for printing inorganically bonded sand seems set to continue that trend. In June, voxeljet AG introduced a patent-pending, cold-curing inorganic binder (cold IOB) technology for forming sand molds and cores without the need for microwave curing after the shape is printed.

voxeljet supplies large-format 3D printers and offers on-demand 3D printing to foundries and other manufacturers. The new “warm” inorganic binder process is a part of voxeljet’s Industrialization for Core Printing project, which developed an automated manufacturing cell to print cores for BMW’s aluminum foundry in Landshut, Germany. Because there is no curing process required for the cold IOB process, capital equipment and operating costs are reduced for the ICP installation.

Inorganic sand binding offers a range of advantages for foundry operations, including the elimination of off-gases when molten metal is poured into a mold, and the possibility for higher casting yields as gas-related defects are eliminated. Inorganic binders are effective at forming complex core geometries, with good surface quality and precision detailing. Foundries also note that finished parts produced from these molds and cores have less sand adhesion, which simplifies and saves cost on handling.

It’s also noted that bonding sands without chemicals reduces the foundries’ consumable costs.

voxeljet emphasized that the molds and cores produced using its cold IOB process technology exhibit “high dimensional accuracy (and) very good detail resolution and edge sharpness.” Of particular note, those qualities will promote the effectiveness of 3D printing larger molds and cores, which is a matter of competitive concern to many foundries.

Typically, warm inorganic binder processes involve a microwave curing step after forming, to dry the sand cores. The voxeljet cold IOB technology only requires drying after printing, which takes place outside the machine. The company notes that the process can be used on all voxeljet platforms, and is being tested on the VX1000 and VX1000S printers. It will be available soon on the VX2000 series machines.

Foundries are showing an increasing interest in inorganic binder processes, especially in view of expanding emissions regulations and corporate standards that prioritize environmental performance. This includes automotive foundries, obviously. According to the developers, the cold IOB technology is particularly well-suited to prototyping processes and medium-volume production.

"The introduction of cold IOB technology is an important step toward further adoption of printed cores and molds with inorganic binders in the foundry industry," claimed voxeljet CEO Dr. Ingo Ederer. "Our goal is to provide innovative solutions that not only increase efficiency, but also help promote the sustainability of metalcasting."