Who's afraid to cut to zero? Most U.S. mold shops still leave extra stock on the cores and cavities of the molds they machine. This practice is unnece

To go from milling machine to mold press to perfect molded part with the first shot is the dream of many mold shops.

"There's no reason a mold shop can't achieve that goal," says Keith Kauzlarich, vice president of Single Source Technologies (SST) in Auburn Hills, Michigan. "The process to machine molds that need no benching or spotting exists today. Most mold shops in the United States simply haven't embraced the technology that this process requires," he says.

A high percentage of mold shops habitually leave at least 0.001 to 0.003 inch of extra material on cavities and cores. This practice ensures the shop that there is sufficient stock to allow for hand grinding, polishing and other adjustments without exceeding the dimensional tolerances on the mold. It also allows for a safety factor to compensate for the margin of error in parts of the customary moldmaking technology, such as:

* CNC programs that cannot generate tool paths that match the geometry to a tighter tolerance band than the stock allowance.