SHOP SOLUTIONS
challenges. Some of our large Inconel parts sell for over $100,000, so we’re used to high-stakes machining. But our tool life on the prototypes run was so poor, we knew the pro- duction order would be miserable. Most of the tools couldn’t complete a single part without needing to replace it. We had to do something different,” said Hurst.
fi nishing work on the outside of the part. It came out to an 8000% productivity increase per tool.” The CoroMill indexable cutter produced similar results,
Knust-Godwin’s switching to a Plura ballnose end mill held in a hydraulic CoroChuck increased tool life to 80 parts per end mill.
VERO Watches enthusiastically accepted the prototypes. Knust-Godwin was soon facing an order for 105 complete watch sets, so they called Grant Gregory, south central pro- ductivity engineer for Sandvik Coromant (Fair Lawn, NJ). Gregory said the problem of poor tool life during prototyp- ing could be solved for production orders by switching to hydraulic toolholders and high-quality cutting tools. Gregory’s recommendations included replacing the ER-style collet hold- ers used to hold the various end mills and drills with Coro- Chuck 930 high-precision hydraulic chucks, greatly improv- ing tool runout and security. Instead of a 0.50" (12.7-mm) diameter solid carbide end mill, roughing was done with a CoroMill 390-07 indexable cutter with GC1130 grade carbide inserts. And the 0.0625" (1.5-mm) ballnose “import” end mills were replaced with CoroMill Plura 1630 grade cutters. The results were dramatic. Hurst said he was previ- ously using two ballnose end mills—a regular length and a stub—to semifi nish and fi nish machine each watch body. By switching to a Plura ballnose end mill held in a hydrau- lic CoroChuck, tool life increased to 80 parts per end mill. “It was an unbelievable improvement,” Hurst said. “Feeds and speeds, depth of cut—everything was the same, ex- cept the one Plura end mill was actually doing 90% of the
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AdvancedManufacturing.org | December 2016
roughing out the entire 105-piece order on a single set of inserts. Tool life improved even with the legacy tooling. In one case in which a 0.032" (0.8-mm) square nose end mill was responsible for cutting a groove on the crown interior, tool life im- proved by 400% by switching to the CoroChuck. “That was the smallest improvement we saw with any of the tools,” said Hurst. “We’d long sus- pected that better tooling would make a difference, but never had this sort of head-to-head comparison.” Granted, the Sandvik end mills cost substantially more than the legacy tooling, but the cost per part still came in at roughly one sixteenth that of the less-expensive cutters, Hurst said, not counting the disrup- tion and downtime of frequent tool changes due to dull cutters.
“Tool life was defi nitely an issue,” Cameron Birse said.
“We had all these three-dimensional surfaces blending into other three-dimensional surfaces, so any time you had to change tools it was a big deal. I think much of the improve- ment came from the carbide, but those hydraulic pencil-style holders defi nitely helped as well. It was a massive benefi t.” Knust-Godwin delivered the watch parts as promised. And because of the greater tool life and surface fi nish achieved with the Sandvik Coromant tooling, Hurst and oth- ers there are looking forward to the next order. “The Houston machining industry has never been very good about diversifi - cation,” said Hurst. “It has always been about the oil fi eld, so when things slow down it’s tough to transition into different markets and actually make it successful. We’ve learned some things from this job and that’s always a good thing. And I can honestly say, even if we never make another watch body again, we’re going to be reevaluating our cutting tools, and how we’re holding them.” For more information from Sandvik Coromant, go to
www.sandvik.coromant.com/us, or phone 800-726-3845; for more information on Knust Godwin, go to
www.knust-
godwin.com; for more information on VERO watches, go
to.www.vero-watch.gcom
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