310 Каталог INGERSOLL 2011 Режущий инструмент и инструментальная оснастка Стр.312

Каталог INGERSOLL 2011 Инструмент и оснастка Стр. 312 0310 Lab2u

INCREASE FEED RATES BY UNDERSTANDING AND APPLYING RADIAL CHIP THINNING FACTORS Radial Chip Thickness Limitations on a cutting tool's performance are generally established in terms of maximum chip load. Since commonly used speed and feed calculators show only Advance Per Tooth (APT) chip load and APT tend to be used interchangeably. This is an area of misunderstanding which can be significant. Chip load actually refers to chip thickness not APT. APT is defined as the increment of feed that takes place in the time necessary for the cutter to rotate the distance between cutting edges. Mathematically it is: A pt J - RPM x T where: IPM Feed rate (inches min) RPM Spindle speed (rev min) T Teeth The chip thickness is the "bite taken by each cutting edge as it performs its work. For a typical end mill in a radial Depth Of Cut (DOC) exceeding two-thirds the diameter of the cutter the chip thickness increases until it equals the APT at the centerline of the cutter. The chip thickness then decreases to nothing as the cutting edge exits the cut (Figure 1). Thus APT is a constant for a given operation and the chip thickness is variable changing cyclically. Peripheral cutting: When end mill cuts are shallow in relation to the cutter diameter the Actual Chip Thickness (ACT) is less than the APT. This chip thinning effect allows much higher feed rates (Figure 2). For example assume the following parameters: 2.000 diameter end mill Two-effective 500 Surface Feet per Minute (SFM) .12 radial Width Of Cut (WOC) .005 chip thickness 955 effective RPM Even though the APT in this case is .0105 the ACT (or chip load) is only .005. A two-effective 2.000 diameter end mill had an APT of .0105 and a chip thickness of only .005. The Radial Chip Thinning Factor (RCtF) is the ratio of chip thickness to APT or in this example .48. Mathematically the RCTF can be expressed as: where: 1 2xWOC Eff. Dia. RCTFD Diameter of cutter WOC Radial Width Of Cut Whenever the radial DOC is equal to or greater than the effective cutter radius the RCTF is equal to 1. 312