Question

A straight-teeth horizontal slab milling cutter is shown in the figure. It has 4 teeth and diameter (D) of 200 mm. The rotational speed of the cutter is 100 rpm and the linear feed given to the workpiece is 1000 mm/minute. The width of the workpiece (w) is 100 mm, and the entire width is milled in a single pass of the cutter. The cutting force/tooth is given by F = Ktcw, where specific cutting force K = 10 N/mm2, w is the width of cut, and tc is the uncut chip thickness. The depth of cut (d) is D/2, and hence the assumption of  d D << 1 is invalid. The maximum cutting force required is ______ KN (round off to one decimal place).

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Answer :

Correct answer is : 2.5

Number of teeth z = 4

cutting force/teeth F = Ktcw

specific cutting force K = 10 N/mm2

Depth of cut, d = D/2 hence  d D << 1 is invalid

width of cut, w =100 mm

rotational speed N = 100 rpm

diameter of cutter, D = 200 mm

Linear feed to workpiece f = 1000 mm/minute

Maximum uncut chip thickness is

tc, max = f sin θ =  f N z 1 ( 1 2 d D ) 2

tc, max f N z 1 ( 1 D D ) 2 = f N z

tc, max f N z = 1000 100 × 4 = 2.5 mm

Fmax = Kt c, maxw = 10 × 2.5 × 100 = 2500 N = 2.5 kN

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