Manufacturing Science MACHINABILITY DYNAMOMETER MACHINE TOOL VIBRATION Presented By AMIT KUMAR ME-1 (3rd) 1214340023

CONTENT INTRODUCTION MACHINABILITY Machinability of ferrous metal Machinability of non ferrous metal Thermally Assisted Machining SURFACE FINISH DYNAMOMETER Mechanical dial gauge type Strain gauge type MACHINE TOOL VIBRATION

INTRODUCTION We all know that the term machinability refers to the case with which a metal can be machined to be acceptable surface finish.. Machinability is a term that describes the ease or difficulty with which a metal can be machined. It can be measured by the life of the cutting tool or the material removal rate in relation to the cutting speed used. The good machinability indicates; 1. Good surface finish and integrity. 2. Long tool life. 3. Low surface and power requirement

Machinability Machinability is defined in terms of: Surface finish and surface integrity Tool life Force and power required The level of difficulty in chip control Good machinability indicates good surface finish and surface integrity, a long tool life, and low force and power requirements Machinability ratings (indexes) are available for each type of material and its condition

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Machinability: Machinability of Ferrous Metals Steels If a carbon steel is too ductile, chip formation can produce built-up edge, leading to poor surface finish If too hard, it can cause abrasive wear of the tool because of the presence of carbides in the steel In leaded steels, a high percentage of lead solidifies at the tips of manganese sulfide inclusions Calcium-deoxidized steels contain oxide flakes of calcium silicates (CaSO) that reduce the strength of the secondary shear zone and decrease tool–chip interface friction and wear

Machinability: Machinability of Ferrous Metals Effects of Various Elements in Steels Presence of aluminum and silicon is harmful, as it combine with oxygen to form aluminum oxide and silicates, which are hard and abrasive Thus tool wear increases and machinability reduce Stainless Steels Austenitic (300 series) steels are difficult to machine Ferritic stainless steels (also 300 series) have good machinability Martensitic (400 series) steels are abrasive

Machinability: Machinability of Nonferrous Metals Aluminum is very easy to machine Beryllium requires machining in a controlled environment Cobalt-based alloys require sharp, abrasion-resistant tool materials and low feeds and speeds Copper can be difficult to machine because of builtup edge formation Magnesium is very easy to machine, with good surface finish and prolonged tool life Titanium and its alloys have very poor thermal conductivity Tungsten is brittle, strong, and very abrasive

Machinability: Thermally Assisted Machining In thermally assisted machining (hot machining), a source of heat is focused onto an area just ahead of the cutting tool Advantages of hot machining are: Reduced cutting forces Increased tool life Higher material-removal rates Reduced tendency for vibration and chatter

Surface Finish Surface finish influences the dimensional accuracy of machined parts, properties and performance in service Surface finish describes the geometric features of a surface while surface integrity pertains to material properties The built-up edge has the greatest influence on surface finish

Surface Finish A dull tool has a large radius along its edges In a turning operation, the tool leaves a spiral profile (feed marks) on the machined surface as it moves across the workpiece Typical surface roughness is expressed as

Surface Finish and Integrity Factors influencing surface integrity are: Temperatures generated Surface residual stresses Plastic deformation and strain hardening of the machined surfaces, tearing and cracking Finish machining is considering the surface finish to be produced Rough machining is to remove a large amount of material at a high rate

DYNAMOMETER It is a device which measures cutting forces accurately during cutting process It should have rigid body to avoid deflection in cutting process Commonly used tool dynamometer are Strain gauge type Mechanical dial gauge type

Strain gauge The dynamometers being commonly used now-a-days for measuring machining forces desirably accurately and precisely (both static and dynamic characteristics) are • strain gauge strain gauge may be of one, two or three dimensions capable to monitor all of PX, PY and PZ. For ease of manufacture and low cost, strain gauge type turning dynamometers are widely used and preferably of 2 – D (dimension) for simpler construction, lower cost and ability to provide almost all the desired force values.

Mechanical force gauge Mechanical dial gauge Mechanical force gauge

MACHINE TOOL VIBRATION In machine tool and cutting processes, machine stiffness plays important role in accuracy and surface finish. Low stiffness creates vibration. Effect Of Vibration Poor surface finish It damages tool component It creates noise pollution Losses of dimensional accuracy of the workpiece

FORCED VIBRATION SELF EXCITED VIBRATION It is caused by some periodic force present in the machine tool i.e. from gear drives, misalignment of motors and pump and due to improper balance of machine tool component. The function of forced vibration is to remove the forcing elements , change the cutting speed and the tool geometry.. SELF EXCITED VIBRATION Self excited vibration is generally caused by the interaction of the chip removal process and the structure of the machine tool. These vibrations generally have high amplitude than forced vibration. This vibration is removed by increasing the dynamic stiffness of the system and by damping.

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