Additive manufacturing makes an ancient art new again

Back in the day, we had Industrial Arts. You might know it as shop class. There I learned to operate bandsaws and engine lathes, drill presses, and hand tools. I used these things to make gifts for family members, hand-crafted objects that would soon be stuffed into the deepest reaches of the pantry, or perhaps placed on a shelf in the garage. A bookend in the shape of Minnesota. A set of plastic salad spoons. A pair of aluminum candlestick holders.

It’s this last gift that I want to talk about. Of all the now-forgotten gifts produced during my formative years, it was the sand-casting of candlesticks that I most enjoyed. The precise placement of the patterns within the flask, followed by the tamping of the green sand and careful assembly of the cope and drag (the top and bottom halves of a pattern or mold). It was glorious work. And the best part? Donning asbestos-lined gloves and pouring molten metal. What’s not to love?

So enamored was I with the sand-casting process that I dreamed of one day being a patternmaker and working in a foundry. Had I taken that vocational path, however, I might now be out of a job—forced to spend my days lamenting over sprues and lost wax. The reason is because—once again—3D printing has changed everything.

It started in the mid-90s, after 3D Systems developed its SLA-based QuickCast technology, followed by the introduction of various brands of 3D printers able to print wax patterns and cores. Goodbye, traditional patternmaking.

I recently learned of another significant shift within the foundry industry. It’s called sand printing, a type of binder-jet technology that essentially glues the individual particles of green sand together. No more tamping, no more painstaking assembly of the cope and drag. Just 3D-print the mold and get pouring.

ExOne makes sand printers. So does voxeljet. In fact, its VX4000 boasts a build volume of 4 meters by 2 meters by 1 meter high (157" x 78" x 39") and is said to be the largest such printer in the world.

As with any additive technology, sand printing offers lead times and production costs a fraction that of conventional moldmaking processes. Design freedom is far greater (though still bound by the physics of molten material flow), while surface quality and accuracy are both significantly improved.

Granted, future high school students will miss out on the opportunity to cast aluminum candlestick holders for their mother, but there’s always turning. What’s not to love?

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