MoldMaking Technology

AUG 2018

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20 MoldMaking Technology —— AUGUST 2018 Cutting Tools Because full-radial engagement trochoi- dal milling has become a popular machining method for roughing, new products like this anti-pullout shank are being introduced to prevent the cutting tool from pulling out of the tool holder. Here, special drive keys match the spiral-shaped grooves on the cutting-tool shank, creating frictional clamping forces and a positive locking form-fit. productivity because it enables faster permissible speeds and increased tool life." Ingersoll Cutting Tools's William Fiorenza notes that many cutting-tool companies continue to refine indexable insert designs to maximize the number of cutting edges per insert. "This provides for maximum economy when roughing," he says. "Additionally, insert rake-face geometries and edge prepa- rations continue to be optimized for specific material types and cutting conditions." He explains that rake-face geometries and edge preparations serve to reduce cutting forces through insert design features that create freer cutting and sheering action while still maintaining strength. They also help reduce cutting forces in short and long tool-reach milling applications, reduce the amount of heat that goes into the workpiece and do a good job of carrying away the heat produced during the cut- ting action via well-formed chips that absorb that heat. "The die and mold indus- try often contends with extended reach applications that require long length- to-diameter ratios," he says. "Well-designed insert geometries, cutting-edge preparations and coatings help them deal with these challenging applications as well as others, including interrupted cuts, re-cutting of chips, full-channel cutting or large radial engagements and milling specialty mold and die steels, soft non-ferrous materials and some high-temperature stainless steels." "Roughing with high speeds have become a reliable practice with customers," Kedar Bhagath of Tungaloy America Inc. says. "Customers are moving away from traditional button-insert cutters and adopting high-feed milling solutions that provide a constant approach angle of 10 to 17 degrees versus using a round insert where the approach changes for each DOC. Tooling materials are getting harder than the traditional P20 or H13, with anything over 36 HRC increasing the possibility of insert chipping and subsequent damage to the body of the tool if the cutting parameters are not optimum. Generally, machining of hard mold bases usually requires that the DOC and cutting speeds be lowered to achieve consistent tool wear. Yet, depending on the machines in question, larger DOC capabilities in high-feed machining are in demand, driving tool makers to develop better geometries and insert grades to higher reliability and consistency." OSG USA's Steve McBride says that OSG USA offers exchangeable head and solid-carbide end mills with three to six flutes that are specifically designed for machining very deep applications in the range of six to 20 times the tool diameter. "This depth range is very difficult to machine using typical end Image courtesy of Haimer USA. mills because of extreme tool push off," he says. "Most customers decide to use EDM on these deep applications, resulting in much longer cycle times and an overall higher cost. The bottom line here is that machining cycle times can be greatly reduced by using solid-carbide tools to eliminate EDM processes wherever possible." Jay Ball of Seco Tools says that many cutting-tool companies have invested heavily in advanced multi-flute geometries (with five, six, seven and nine being the most common) because more flutes enable faster feed rates which in-turn reduce cycle times. "By adding variable geometry to help break up chatter and harmonics, incorporating unique chip splitters to aid in chip evacuation in deep-pocketing applications and incorporating the latest in carbide substrates and coatings, multi-flute tools are leading the way in process optimization." However, with so many new strategies and cutting tools flooding the market, it can be hard to determine which advanced strategy is best for the customer's application, according to Ball. "Each strategy has its benefits, but there are also certain criteria that must be taken into consideration to make these strategies effective, like machine limitations (lack of rpm, horsepower, feed-rate capabilities and so on), not having the right programming software to take advantage of new strategies or simply that the specific component that the customer is trying to machine does not contain adequate features." For example, he says that optimized roughing is bet- ter-suited for straight-walled parts and is not always the best solution for complex 3D surfaces. "High-feed roughing would be a better option in this situation." Getting More Value Out of Every Cut Every machinist worth his or her salt knows how important it is to keep cutting tools in good, working I witness a lot of 'waste' in terms of carbide utilization. Simply put, most people are not using what they are paying for.

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