302 Каталог INGERSOLL 2011 Режущий инструмент и инструментальная оснастка Стр.304

Каталог INGERSOLL 2011 Инструмент и оснастка Стр. 304 0302 Lab2u

MILLING APPLICATION & SELECTION GOING BACK TO THE BASICS OF FACE MILL DESIGN TO SELECT A TOOL TO MATCH YOUR APPLICATION When milling with an indexable face mill the workpiece machine and fixturing must all be as rigid as possible. This will help ensure efficient use of this type of tool and produce the results required. Only cutters using indexable carbide inserts will be discussed here. Proper cutter diameter. For maximum efficiency two-thirds of the cutter diameter should engage the workpiece. In other words the cutter diameter should be 1-1 2 times the width of cut desired. Climb milling using this cutter diameter to width of cut ratio will ensure a favorable entry angle into the workpiece (Fig. 1). If uncertain as to whether the machine has enough horsepower to operate the cutter under this ratio it may be best to divide the axial depth of cut into two passes (or more) to maintain as closely as possible this cutter diameter to width of cut ratio. Climb Milling Negative Axial Rake H I Negative Geometry Applying cutter geometry. Insert cutting edges may be positioned relative to both radial and axial planes in positive neutral or negative rakes. Neutral rake is generally not used due to the shock of the entire cutting edge impacting the workpiece simultaneously. The combination of radial and axial rakes determines the shear angle. Three basic combinations are available: negative radial and axial positive radial and axial negative radial positive axial and positive radial negative axial. Double negative geometry is the traditional starting point for rough milling cast iron and steels when horsepower and rigidity are adequate. The double negative insert design provides the strongest possible cutting edge and can withstand heavier chip loads and considerable cutting forces (Fig. 2). The increased cutting forces generated by this geometry will consume more horsepower. Double negative cutters also require greater machine workpiece and fixture rigidity. Fig. 2 Fig. 1 Fig. 3 Positive Geometry Double positive geometry provides the most efficient cutting action due to its increased shearing angle. Although not as strong as double negative entry impact and cutting forces are greatly reduced making it a good choice for older less rigid machines or where horsepower is limited. With double positive geometry the peripheral edge in both the radial and axial planes leads the insert through the workpiece creating a true shearing action. This makes it the best choice for non-ferrous materials and many soft gummy stainless steels (Fig. 3). Negative radial positive axial geometry combines some of the advantages of both double negative and double positive. Negative radial rake provides strong cutting edges while positive axial rake creates a shearing action. A positive axial rake directs chips up and away from the workpiece. This prevents chip recutting and takes heat away from the work surface and the cutting edge. Positive radial negative axial geometry reduces power consumption while still providing a strong corner cross-section. 304