Machine Design

NC router shapes ice art

When they founded Ice Sculptures Ltd., Grand Rapids, Mich. Randy Finch and Derek Maxfield were restaurant chefs and award-winning carvers of decorative ice sculptures.

When they founded Ice Sculptures Ltd., Grand Rapids, Mich. (, in 1994, Randy Finch and Derek Maxfield were restaurant chefs and award-winning carvers of decorative ice sculptures.

Today they make sculptures as varied and ambitious as a 12 15-ft map of the world, a working Ferris wheel featured in Ripley's Believe It or Not, and corporate logos for business meetings. The marriage of a CNC router and CAD/CAM software lets the team quickly cut intricate sculptures and sell them for about the price of a floral arrangement.

A dolphin centerpiece is a representative example. Finch first scanned a dolphin silhouette into CASmate CAD software and established cutting paths with vectorized lines. That file went to TPC Win, proprietary CAM software for the shop's three-axis Cam Tech Industries CNC router, where toolpaths and cutting parameters were assigned.

The shop makes its own ice with a Clinebell icemaker. The machine freezes the ice from the bottom up while continually circulating any unfrozen water. Impurities and minerals are kept in motion and then siphoned off, producing dense, clear ice. "The denser ice is harder and lasts at least twice as long as refrigerator ice," says Finch. One 150 lb, 20 5-in. block of ice makes five 12-in.-high, 15-lb dolphin centerpieces.

In the "machine shop" — a 28°F freezer — Finch puts the ice block on a sheet of CorrPlast, a corrugated plastic material, to protect the router's 52-in.-sq table from cutter overruns. Wet "snow" packed around the block edges solidly freezes the block and the aluminum table together. No clamps are needed to hold down the work piece. Blocks must be located carefully on the table, because the dolphins are cut initially to only half depth, after which the block is flipped over to complete the second side.

The first operation roughs out the dolphin shape with an end mill. "We cut down by 0.25 in., move it over, then cut down another 0.25 in.," explains Finch. The cutter runs at 100% feed — 240 ipm — and 2,100 rpm. Maintaining high feedrates helps clear out the snow, crucial because heated air from the router can cause it to readhere to the cut surface and make it rough. The next operation uses a woodcutting roundover bit to smooth the 0.25-in. steps left by the roughing operation. A smaller end mill then cuts fine detail and thin lines on the fin or the mouth at about 40% feed or 96 ipm, but at the same 2,100-rpm spindle speed. Keeping spindle speed up and tools sharp avoids chipping. Freezer temperature also plays a role. Optimal temperature is about 28°F. Any colder and the ice becomes more brittle.

An ice pick and a rubber mallet are used to release the block from the table. The block is flipped over, positioned, and checked for alignment by running a toolpath with the depth of cut set above the ice surface. The toolpaths for the second side are mirror images of those for the first, except cutting depths leave 0.25 in. around the perimeter of each dolphin. The final step runs a separate program that cuts along the outside silhouette. The centerpieces require minimal finishing. Carvers may use a hand tool to smooth out edges or add final details. A warm water bag rubbed over the surface acts like sandpaper and polishes it. Dolphins are mounted on an ice base, wrapped in bubble wrap, and shipped in a Styrofoam box.

"Each dolphin takes about 12 min to complete," says Finch. "A skilled sculptor, working with conventional tools, might be able to make a dolphin of comparable quality in about an hour." The NC router lets the company turn out as many as 250 centerpieces for a single function. Once in place, a dolphin melts evenly and lasts about 6 to 8 hr.

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