Task 1 As it was discussed earlier in our lectures, the rate of tool wear strong
ID: 2250387 • Letter: T
Question
Task 1 As it was discussed earlier in our lectures, the rate of tool wear strongly depends on the cutting temperature, therefore, any measures which could be applied to reduce the cutting temperature would reduce the tool wear as well. Tool wear is the breakdown and gradual failure of a cutting tool due to regular operation. Every tool will experience tool wear at some point in its life. Excessive wear will show inconsistencies and have unwanted effects on your workpiece, so it is important to avoid tool wear in order to achieve optimal end mill performance. Tool wear can also lead to failure, which in turn can lead to serious damage, rework, and scrapped parts The figure shows the process parameters that influence the rate of tool wear rature Tool wear Cutting tool wear as a function of basic process With the aid of examples and schematics diagrams, provide a standard report of a limited 1500 words size to explain all the parameters shown in the figure [4096]Explanation / Answer
Fluids
In metal cutting process, heat is generated due to plastic deformation of metal, friction between chip and rake face of the tool and rubbing between the flank and work. This increases the temperature of both tool and workpeice .temperature affects the life of tool causing tool wear and tool failure.cutting fluids are used to reduce the temperature and tool wear.
Cutting conditions
Cutting speed
The cutting speed affects the tool life greatly. increasing cutting speed increases the tool temperature and shortens the tool life.cutting speed varies according to the hardness and type of material.
Increasing cutting speed by 20%,decreases the tool life by 50%. Increasing cutting speed by 50% decreases tool life by 80%.
Cutting at low cutting speed (20-40m/min) tends to cause chattering. thus tool life is shortened.
FEED
When cutting with general holder,feed is the distance a holder moves per workpeice revolution. In Milling, feed is the distance as feed per tooth
Decreasing feed rate results in flank wear and shortens the tool life.
Increasing feed rate increases cutting temperature.
Increasing feed rate improves machining efficiency
DEPTH OF CUT
Changing deprh of cut doesn't effect tool life greatly.
Small depths of cut result in friction when cutting the hardened layer of workpeice. thus tool life is shortened.
CUTTING TOOL SHAPE
In single point cutting tool ,
CUTTING TEMPERATURE
The possible detrimental effects of high cutting temperature on cutting tool are:
TOOL MATERIAL
Cutting tool material must be harder than the material of the workpiece,even at the high temperature during the process.
The cutting tool material must have the following properties.
Cemented carbides:harder than tool steels,but less tough.
Cutting ceramic:They are even harder than cemented carbide.but can't be used for machining steel,due to very high wear.
The heat treatment and its extent on the tool surface also influence the the tool wear.
WORK MATERIAL
CONTACT STRESSES
The high contact stress between the tool rake face and the chip causes severe friction at the rake face as well ,there is a friction between the flank and machined surface.
The shear stress is the stress among the contact stress influence the cutting and removal of the metal.
As the shear stress increases, the heat devoleped also increases causing tool wear
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