Ingersoll has developed a new worm-machining process based on an inexpensive replaceable carbide-tipped milling tool that can cut cycle time by 3-to-1 and triple the tool service interval. Moreover, it does away with the hobbing machine and all the supply-chain issues associated with re-grindable HSS hobs. The setup that makes it all possible is a modified standard Chip-Surfer replaceable-tip milling cutter, tapered to exactly match the required tooth form, running on a four-axis mill.
“In most cases, a worm blank is put on a mill sometime in the process anyway, at least to cut a keyway,” says Ingersoll tool engineer Jeremy Bradley, who developed the process. “So it’s a matter of adding an operation on the mill, rather than transferring the part to an entirely different machine for that single tooth hobbing operation.”
In its first application, the Chip-Surfer based process completes the worm in a single pass, reducing cycle time for tooth forming from 14 minutes to four. The replaceable tip costs about 2/3 less than a single regrind on the previous $400 high-speed steel (HSS) hob. Mounted on an alloy steel shank, it lasts through 60-80 pc, vs. 200 between resharpenings before. Tip changes now take only a minute and can be done in the spindle to a 0.0005” repeatable accuracy to datum with no touching-off required. By contrast, swapping out the hob interrupted the operation for 15 minutes and did involve touching-off.
Most worms are fabricated in three basic operations, inevitably requiring two transfers among machines. First the barstock is turned to generate the hub and worm ODs. Next, they are milled to create such non-tooth related features such as flats and keyways. Finally comes the hobbing, on its own machine.
“The Chip-Surfer for worm cutting qualifies as a ‘modified standard’ more than a “special,’” says Bradley. “We simply impart a taper, to match the tooth form, on a standard cylindrical Chip-Surfer blank. All the other features—rakes, clearances, helix, gullet, etc.—are standard and proven. There is none of the risk associated with complete ‘specials.’ Supply chain risks are also vastly reduced vs. form-matched HSS worm hobs, which are ‘specials’ by definition and bring in the uncertainties of the ‘regrind carousel as well,” he added.
“This solution could create a sea change in worm manufacturing,” says Konrad Forman, Ingersoll North American milling product manager. “Besides helping legacy worm manufacturers, it opens up a new market segment for shops that don’t own hobbing machines. The tool covers virtually all mainstream worm applications. Any shop with a 4 axis mill can now quote a worm job.”
Worm machining is just the latest success for modified standard Chip-Surfers and their replaceable-tip feature. Other typical applications include slotting and cavity milling and replacements for endmills, solid carbide or HSS, in a host of other settings. Compared with HSS, the tool cuts much, much faster and lasts much, much longer. Compared with solid carbide endmills, the replaceable-tip delivers all the benefits of expensive carbide but uses up to 90% less of it. When mounted on an alloy steel shank, it also eliminates the risk of brittle failures due to vibration or excessive lateral forces.
For more information, visit www.ingersoll-imc.com.
