b'\x1b\x1a\x19 \x1f\x18\x1d\x17\x16Get With the ProgramPRICIEST TOOL MAY BE THE CHEAPESTBy Stas Mylek,throughout the cutting tests. optimal cost performance.CNC Software Inc. We chose D-2 tool steel with aWe chose a $100 machine-bur-hardness of 31 to 32 HRC as theden rate and calculated costs based T hose who track productivity andworkpiece material. Its dimensionson removing 1,000 cu. in. of mate-machiningperformancearewere16"24"2"(406.4mmrial, letting us extrapolate cost per-likely familiar with the concept of609.6mm50.8mm). We designedformance over a full run of parts.price versus cost of use. Despitea test part that would maximize theBased solely on tool price, tool D, at their familiarity, though, when theyvolume of material removed and$87.80, was the best choice (see chart talk to a cutting tool vendor aboutincorporated various part features. on page 33). Based solely on mrr, tool price, their reaction often is Yikes,We also chose a38 " (9.5mm) toolA, at $112.87, was best. We used mrr that tool is expensive! They reactto maximize in-cut time for the vol- to calculate the total amount of ma-this way because they dont under-stand how tool performance affectsUnlike traditional, the true cost of machining a particu- offset-based lar part. toolpaths, newer Many expensive cutting tools havetoolpath strategies been engineered for high efficiency.and technology can help keep machining When programmed to follow opti- performance at an mal CAM toolpaths and matched tooptimal level. a machine tools capability, they may offer total-cost-and-performance re-sults that are significantly better than lower-cost cutting tools.At our manufacturing lab, CNC Software Inc., Tolland, Conn., con-ducted tests comparing cutting tool prices and actual productivity costs.All images: CNC Software We wanted to discover if precon- ume of material to be removed. Thechining hours needed to cut 1,000 cu. ceived notions we hear about cut- tools varied in price, but we stayedin. of material using each cutting tool. ting tool costs were true. One no- within about a 25 percent differen- Factoring in both tool and machining tion is that productivity results for antial between the highest- and low- costs, tool A proved to be the best expensive tool will be essentially theest-priced tools. The tools ran at theperformer, at $1,025.43, compared same as a cheaper tool. same WOC (15 percent) and a DOCwith $1,620.89 for B, $1,737.41 for C We selected four solid-carbideabout 1.5 times diameter, or 0.500"and $1,772.45 for D.endmills, cutting a sample part(12.7mm), even though the mostThe recommended speeds and made from a familiar yet challeng- expensive tool was capable of ma- feeds varied from tool to tool. Rec-ing material. To maintain a levelchining at 2 times diameter. ommendations for the lower-cost playing field, we chose tools for cut- Our goal was to measure tooltools were conservative compared ting ISO P group steel and initiallylife, in-cut cycle time and material- with the pricier and top-performing used the cutting parameters forremoval rate when machining thetool. The lower cutting parameters surface speed (in sfm) and feed persame part. We wanted a methodcertainly influenced the final mrr of tooth (in ipt) recommended by eachcustomers could use to measurethe lower-cost tools. However, we tool vendor. We used Mastercamperformance, make decisions af- believed we could use Dynamic Dynamic toolpaths to ensure andfecting job profitability and deter- Motion to run these tools more ag-maintain a consistent chip thicknessmine which cutting tool providedgressively, knowing we could keep 30MARCH 2018GetwithProgram.indd 30 2/13/18 4:03 PM'