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Milling
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Theoretical ConsiderationsThe cutting speed V in milling is the peripheral speed of the cutter:
where,
Note that the thickness of the chip in slab milling varies along its length because of the relative longitudinal motion between cutter and workpiece. For a straight-tooth cutter we can determine the approximate undeformed chip thickness, tc, (chip depth of cut) from the equation:
where,
As the value of t, becomes greater, the force on the cutter tooth increases. Feed per tooth is determined from the equation:
where,
The cutting time t is given by the expression:
where,
Based on the assumption that lc < l (although not always true), the material removal rate is:
where,
The distances that the cutter travels in non-cutting cycles of the milling operation are important economic considerations and should be minimized. Although we can calculate the power requirement in slab milling, the tangential, radial, and axial forces acting on the cutter are difficult to calculate because of the many variables involved, particularly tool geometry. The upper bound technique provides a method of computing an upper value for the cutting forces. These forces can also
be measured experimentally for a variety of conditions. From the
power, however, we can calculate the torque on the cutter spindle.
Although the torque is the product of the tangential force on the
cutter and its radius, the tangential force per tooth will depend
on how many teeth are engaged during the cut.
Source: Kalpakjian, Manufacturing Processes for Engineering Materials. |
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