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10   Phone: 516-328-3970 www.technocnc.com Technical Section to the tougher body construction (carbide), delivers the best edge finish, largest variety of geometry profi les available, can achieve greater feed rates, is the best tool for plunging into the workpiece and has relatively low cost. PCD Diamond tools are ideal for very abrasive materials. These type of tools,  however,  are  not  cheap,  perform  very  poorly  on nonabrasive materials, cannot plunge, and are limited to how fast they can route. Heat Heat generation in cutting tools should be avoided. Heat can change the properties of the tool and melt or burn the material being routed. This can lead to very poor surface finish, causing the tool to fail/break, or material melting and wrapping  onto  the  tool.  There  are  many  causes  of  heat buildup such as improper tool selection, incorrect machine feeds, incorrect spindle rpm and/or rotation, and improper toolpath programming. In order to minimize or eliminate the heat build up, you must avoid the above causes. To determine if you have programmed the feeds and speeds correctly, you can follow these simple formulas: Formula 1:  Chipload = chipload % x cutter diameter Formula 2:  Feed Rate = [chipload] x [# of fl utes] x [rpm]   A good starting point for determining chipload (thickness of the chip) is 2% of the cutter diameter  (example 1/4” cutter = .005). For softer materials, it is recommended to take 4% of the cutter diameter. 2%   Hard material:           Brass, hardwood, cast acrylic, solid surface 4%   Soft material:           Aluminum, MDF, particle board, extruded acrylic,           sintra, polycarbonate Chipload = [2% or 4%] x [cutter dia] Feed Rate = [chipload] x [# of fl utes] x [rpm] Example 1: 1/4” 2-flute endmill (Hard Material)      Chipload = .02 x .25 = .005   Feed Rate = .005 x 2 x 18000 = 180   Feed Rate = .005 x 2 x 12000 = 120   Feed Rate = .005 x 2 x 6000   =   60 Example 2: 1/4” 4-flute endmill (Hard Material)      Chipload = .02 x .25 = .005   Feed Rate = .005 x 4 x 18000 = 360   Feed Rate = .005 x 4 x 12000 = 240   Feed Rate = .005 x 4 x 6000   = 120 Note  that  for  each  cutter,  there  is  a  feed  rate  range that corresponds to the rpm range.  The number of flutes determines the range at which a cutter should be fed. The number of fl utes should be taken into consideration when cutting material.  3- and 4-flute cutters are best for high feed rates, while 1- and 2-fl ute cutters are best at lower feed rates.  Also, keep in mind that spindles have peak power at  higher rpm.  It is better to use a 2-fl ute cutter at 18000 rpm than a 4-fl ute at 9000 rpm. When dealing with material that melts, a thicker chip will reduce melting.  When cutting deep into these materials, it becomes important to remove the chips from the cut. Cutters with fewer flutes are better capable of removing these chips. Also, larger cutters are better for dealing with melting.