Question

The top surface of a rectangular work part is machined in a peripheral milling operation. The work part is 735 mm long by 50 mm wide by 95 mm thick. The milling cutter, which is 65 mm in diameter and has five teeth, overhangs the width of the part equally on both sides. Cutting speed = 60 m/min, chip load = 0.20 mm/tooth, and depth of cut = 7.5 mm.

(a) Determine the time required to make one pass across the surface, given that the setup and machine settings provide an approach distance of 5 mm beforeactual cutting begins and an over travel distance of 25 mm after actual cutting has finished.

(b) What is the maximum material removal rate during the cut?

(c) If the workpiece has surface scale, would you recommend conventional milling or down milling? Why?

Answer 1

a) Number of revolutions

Feed rate =

Approach Distance =

Given an approach distance of 5 mm before actual cutting begins and an over travel distance of 25 mm after actual cutting has finished. Hence machining time is given by:

b) maximum material removal rate =

c) For conventional milling the cutter rotates in a direction opposite to the table feed and for down milling the cutter rotates in a same direction to the table feed. Conventional milling has maximum chip thickness is at the end of cut while down miliing has maximum chip thickness at the begginning of the cut. Conventional milling is a smooth process and is hence preferred for workpiece having surface scale.