MoldMaking Technology

AUG 2018

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Page 20 of 83 19 This zoomed-in view shows a cutting tool's edge that does not have any coating applied. It is almost impossible to detect the difference between the uncoated tool and the tool with the proprietary coating. finishing, there are part features that can benefit from other types of geometries. We are starting to see the development of indexable tooling that incorporates larger radii. When this is designed into indexable, precision tooling, it allows for shorter cycle times because one can take greater stepdowns and still maintain a good finish. Die and mold builders will undoubt- edly find a home for this type of tooling." Ed Francis, vice president of Imagineering at Crystallume (Santa Clara, California), says that many mold shops have started to hard mill as much as possible to cut down or elimi- nate the machining of graphite electrodes for EDM. "This eliminates multiple instances of fixturing the mold as various operations are performed on it," he says. "However, it is still a challenge for very fine detail since the small diameter tools with the reach required may deflect too much. The tolerances on the molds and parts that moldmakers produce have also become tighter—a couple of microns in some cases—neces- sitating that the tolerance of the cutting tools also becomes tighter. Customers sometimes ask me what kind of exotic molds require these new, tight tolerances, and I tell them to think of a multi-blade razor where one blade is a few tenths taller and peels off a layer of your skin. Even a commodity item like a razor needs these types of tolerances." Bill Pulvermacher, director of Product Marketing for YG-1 Tool Co. (Vernon Hills, Illinois), says, "The challenges are always about the time, the repeatability of the processes and the surface quality to reduce or, even better, avoid hand pol- ishing." He says that customers also are requesting carbide- grade indexable inserts to machine the finish. Kedar Bhagath, chief technical officer at Tungaloy America Inc. (Arlington Heights, Illinois) says, "Inserted-type cutters are desired for cost savings and to avoid regrinding, while head-exchangeable types also help to avoid having to regrind edges." Steve McBride, manager of the High Tech Group for OSG USA (Glendale Heights, Illinois), says that typically, in deep hole drilling of over three times the tool diameter, it is acceptable to do multiple pecking. This means that the machinist drills three times the diameter in one peck and then begins pecking or drilling in smaller depths until the required depth is reached. "These multiple pecks cost a lot of cycle time. A machinist may have a drill that will drill up to 30 times the diameter in one continuous peck and at faster feed rates. The reduction in cycle times is mind boggling for anyone who has not used one," he says. Smoothing the Roughing Process Drew Strauchen, vice president of Marketing and Business Development at Haimer USA (Villa Park, Illinois), says, "We are see- ing more customers using anti-pullout shanks in con- junction with high-helix end mills for roughing, in which the helix is greater than 30 degrees." He explains that I-machining (also called full-radial engagement trochoidal milling) has become a popular machin- ing method for roughing, but because of higher degrees of engagement between the high-helix end mill and the work- piece, the process often generates greater pullout forces for end mills with diameters larger than 0.375 inch. Forces that can cause the end mill to twist and pull out like a corkscrew opening a bottle of wine. "Using an anti-pullout shank pre- vents the cutting tool from pulling out of the tool holder because special drive keys match the spiral-shaped grooves on the cutting-tool shank, creating frictional clamping forces and a positive locking form-fit," he says. "This also helps increase Customers are starting to adapt more complex machining strategies like optimized roughing and complex five-axis machining using barrel-style cutting tools into their daily manufacturing processes. Images courtesy of Crystallume. This zoomed-in view shows a cutting tool's edge with a proprietary two- to three-micron diamond coating. This image provides a zoomed-in view of a cutting tool's edge. The cutting edge here has an 18- to 20-micron standard diamond coating, which is very detectable.

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