There are two distinct method of
feeding the work when operating a cutter on milling machine.
Conventional milling
When the work is fed in a direction
that is opposite to the rotation of the milling cutter which is also known as
up cut milling. The up cut milling is very generally used.
Up Cut Milling |
Climb Milling
When the work is fed in a direction that is same as the direction of
rotation of cutter, which is also known as down cut milling. The down cut
milling is less commonly used. Though the down cut milling has certain
advantages over conventional milling, down cut milling impose
certain restrictions. Down cut milling cannot be used on all
machines except on those machines that are design to take up the backlashes
between the lead screw and its nut. Further the teeth of milling cutter come
into contact with, and begun to cut into, a heavy section of metal instead of a
zero edged section as in conventional milling.
Down Cut Milling |
Advantages of Climb Milling
(a) Increased Tool Life - Since
the chips pile up behind or to the left of the cutter, tool life can be
increased.
(b) Less Costly Fixtures Required
- Climb milling forces the work piece down instead of trying to lift as with
conventional milling; therefore, simpler holding devices are required.
(c) Improved Surface Finish - Chips
are less likely to be carried into the work piece by the cutter teeth, which
prevent damage to the work surface.
(d) Less Edge Breakout - Because
the thickness of the chip tends to get smaller as it nears the edge of a
workspace, there is less chance of breaking, especially with brittle materials.
(e) Lower power requirements - Since
a cutter with a higher rake angle can be used, approximately 20 percent less
power is required to remove the same amount of metal.
Disadvantages of Climb Milling
This method cannot be used unless
the machine has a backlash eliminator and the table gib have been tightened. .
It cannot be used for machining castings or hot-rolled steel since the hard
outer scale will damage the cutter.
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