force measurement in plain milling

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In milling operation cutting tool observes 3 dimensional forces. So for long life of tool the measurement of force is required.

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FORCE MEASUREMENT DURING PLAIN MILLING:

FORCE MEASUREMENT DURING PLAIN MILLING Submitted in partial fulfillment of the Degree of Bachelor of Technology in MECHANICAL Engineering SUBMITTED BY:- ROHAN KUMAR SHARMA

CONTENTS:-:

CONTENTS:- INTRODUCTION METHODS TYPES OF DYNAMOMETER BASICS OF DYNAMOMETER MILLING DYNAMOMETER

INTRODUCTION:

INTRODUCTION Milling is the machining process of using rotary cutters to remove material from a work piece advancing (or feeding) in a direction at an angle with the axis of the tool. Milling operation:- Plain milling Face milling End milling Side milling Thread milling etc.

PowerPoint Presentation:

Plain milling:- Plain Milling, also called Surface Milling or Slab Milling, is milling flat surfaces with the milling cutter axis parallel to the surface being milled. Generally, plain milling is done with the work piece surface mounted parallel to the surface of the milling machine table and the milling cutter mounted on a standard milling machine arbor. The arbor is well supported in a horizontal plane between the milling machine spindle and one or more arbor supports.

FORCE MEASURMENT IN PLAIN MILLING:

FORCE MEASURMENT IN PLAIN MILLING FORCE MESURMENT IN MILLING COMPRISES THE ESTIMATION AND MESURMENT OF `THE PHYSICAL VARIABLES INTO ANOTHER SUITABLE VARIABLE WITH THE HELP OF TRANSDUCER AND THEN BY READING AND CALIBRATING VALUE OF FORCE IS EVALUATED. REQUIRMENT FORCE MEASURMENT This information knowing the cutting forces enable engineers or anybody estimation of cutting power consumption. It has to be minimum as far as possible. Now in cutting some power is consumed that has to be known and then we should act accordingly. Estimation of cutting power consumption - for selection of motor, machine tools is driven by some motors and what should be the specification of that motor? When we design a machine tool, we design the power drive and in the power drive, we have to select one say motor what should be the power of the motor and what should be the rpm or speed of the motor and that requires knowing the cutting force.

METHODS OF MEASURING FORCE:

METHODS OF MEASURING FORCE THERE ARE TWO METHODS FOR MEASURING MACHINING FORCE IN ANY MACHINING OPERATION INDIRECT METHOD:- USES BASIC MATHEMATICAL AND MECHANICAL PRINCIPALS TO EVALUATE THE FORCE. DIRECT METHOD:- USES TRANSDUCER AND OTHER EQUIPMENT TO EVALUATE THE MACHINING FORCE.

INDIRECT METHOD:

INDIRECT METHOD In this method the firstly deflection of tool is determined and then with the help of the deflection formula for cantilever beam = Deflection of beam is measured by using dial gauge . Since the value of deflection is very low so highly sensitive dial gauge is used to measure the deflection. After evaluation of value of L and deflection the value of machining force is deduced.

DIRECT METHOD:

DIRECT METHOD In this method dynamometers are used. A dynamometer or "dyno" for short, is a device for measuring force, torque, or power.  This method is more reliable and precise than indirect method Dynamometer uses transducers . A transducer is a device that converts a signal in one form of energy to another form of energy.

TYPES OF DYNAMOMETER:-:

TYPES OF DYNAMOMETER:- DYNAMOMETER USED IN DIRECT METHOD IS DIFFERENCIATED ON THE BASIS OF THE USED THERMOCOUPLE IN THE DYNAMOMETER. THESE ARE THE FOLLOWING TRANSDUCER:- POTENTIOMETER LVDT(linear variable deferential transformer) CAPACITIVE PICKUP TYPE PIZEOELECTRIC CRYSTAL

BASICS OF DYNAMOMETER :

BASICS OF DYNAMOMETER While milling operation tool is considered as cantilever beam. And when force acts on the tool then tool tends to bend. So then the upper portion of the tool undergoes the tension and the lower portion undergoes in the compression. So then the resistance of the tool changes. So R1,R2 is the resistance of the tension part and the R3 and R4 depicts the resistance of the compression . So using the whitstone bridge circuit the delta voltage is measured and then the deflection is calibrated by the voltage. So thus the value of deflection is evaluated.

PIEZEOELECTRIC TYPE DYNAMOMETER:

PIEZEOELECTRIC TYPE DYNAMOMETER PIEZEOELECTRIC EFFECT:- When piezoelectric crystal is subjected to pressure, then some emf will be generated at the end. And when voltage provided to it changes its size. WORKING:- Crystal is connected to metallic plates say copper plates and then subject to a pressure, because of the pressure at the end some emf will be generated and this emf is proportional to the pressure of the force that may exerted from the crystal. Now this force can be the cutting force. So this can be connected to the cutting tool or it can be connected that the entire force will be transmitted on to the crystal through this copper plates. So by calibration here, if you calibrate force P and emf here and you get a curve. You apply known force known force that is known pressure; you get certain value of epsilon.

ADVANTAGES OF CRYSTAL DYNAMOMETER:

ADVANTAGES OF CRYSTAL DYNAMOMETER IT IS MORE SENSITIVE THAN STRAIN GAUGE TYPE DYNAMOMETER. IT IS MORE ROBUST. IT HAS VERY LOW CROSS SENSITIVITY. VERY QUICK TIME RESPONSE. MORE STABLE AGAINST TEMP. AND HUMIDITY.

MILLING DYNAMOMETER:

MILLING DYNAMOMETER Milling dynamometer, the work piece is mounted on a plate the plate is rest resting on four supports they are call octagonal rings and that is fixed in the base plate that is fixed on the based this is the base plate. Now here what is octagonal ring this is called octagonal ring or O ring. If the O ring or octagonal ring fixed over here say fixed over here and apply a force Pz then the stress will develop here . Then the developed stress is measured by wheatstone bridge dynamometer or crystal dynamometer.

REFERENCE:-:

REFERENCE:- http://textofvideo.nptel.iitm.ac.in/112105126/lec10.pdf http://www.kistler.com/ch/de/applications/cuttingforce/knowhow http://www.technovolt.ro/cataloage/kistler/DINAMOMETRE%20%20FIXE%20SI%20ROTATIVE.pdf

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