Thursday, April 05, 2007
Thinking big: this shop specifies large machine tools not just for today, but also with an eye to the machining possibilities of the future. To prepar
Coast Composites doesn't know of any cutting tools that can mill Invar faster than 1,200 ipm. This is the feed rate of the fastest passes the shop takes in Invar today. Even so, when this shop in Irvine, California, ordered two more five-axis gantry machines for milling Invar molds, company president Jerry Anthony insisted that the machines be able to cut at 2,500 ipm.
Those machines are in the shop now, and they are performing well. They are not cutting at anywhere near their top feed rate but that's OK, says Mr. Anthony. Cutting tools will evolve, and the machines will be ready when they do. With X-Y-Z travels of 30 by 12 by 6 feet, the machines are too big to consider replacing as cutting conditions get better.
Besides, cycle times have improved at the same programmed feed rates. How is this possible? In a word: acceleration.
The big machines are nimble. To meet the 2,500 ipm requirement, machine tool builder Henri Line (Granby, Quebec) applied linear motors in all three linear axes. Four motors drive the gantry along the X axis; one moves the cross slide in Y; and two linear motors move the spindle vertically in Z.
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