20-08-2012, 04:57 PM
Processes & Tooling
ProcessTechnology.ppt (Size: 3.18 MB / Downloads: 79)
Milling Processes
Milling is one of the basic machining processes. Milling is a very versatile process capable of producing simple two dimensional flat shapes to complex three dimensional interlaced surface configurations.
The Process
The milling process:
Typically uses a multi-tooth cutter
Work is fed into the rotating cutter
Capable of high MRR
Well suited for mass production applications
Cutting tools for this process are called milling cutters
Classifications
Milling operations are classified into two major categories:
Peripheral (side)
Generally in a plane parallel to the axis of the cutter
Cross section of the milled surface corresponds to the contour of the cutter
Face
Generally at right angles to the axis of rotation of the cutter
Milled surface is flat and has no relationship to the contour of the cutter
Combined cutting action of the side and face of the milling cutter
Operating Parameters
Feed direction - Conventional vs. Climb
Climb milling
Load of the cutter tends to “pull” the work into the cutter
This results in a small feed force and about 20% less Hp than conventional milling
Downward motion increases the load on the table ways
This method can “pull” the work into the cutter and scrap the work and/or damage the fixture and tool.
Machine must be very ridged to safely utilize climb milling(CNC machines)
USE CAUTION!
Milling machines
Two Major Classifications - Knee & Column and Bed
Knee & Column (Bridgeport type)
Basic job shop type mill
Column mounted to the base which is the major support frame.
Construction provides controlled motion of the worktable in three mutual perpendicular directions.
Knee moves vertically on the ways in the front of the machine
Table moves longitudinally on the ways on the saddle
Saddle moves transversely on the ways on the knee
Quill moves parallel in Z axis or, if head is rotated, X axis
Versatile general purpose machine
Metal Removal RelatedCalculations
Input parameters (con’t)
Depth of cut - Amount of material being removed.
Horsepower required for cut
Material removal rate (MRR) - volume of material being removed per unit of time
In a milling operation, you also have to take into account the thickness of the chip each tooth will remover per revolution as it advances into the work. This value is expressed in feed per tooth.