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CE1.2) This project was based on designing and fabricating a machine which can be used for the purpose of cutting duplicate keys of any kind of automobiles. Usually for two or four wheelers, two keys are supplied by the automobile manufacturer through dealers, of which one will be preserved in the bank, as most of the vehicles are financed by the financial institution. Only one key is left with the customers. So there are more chances of losing the key supplied by the manufacturer. The only remedy is preserving original key and make use of the duplicate key or vise-versa. So the objective of the project was to design and fabricate a machine which can duplicate the original key very precisely and accurately within short span of time, to avoid the user of the automobile from the helpless condition in the event of the loss of the keys. My responsibility was to perform the design procedure of various parts, do necessary calculations based on that, draw engineering drawings of some parts and co-operate with the project mates to do fabrication and assembly of the machine.
CE1.3) In the entire duration of the project, I regularly met project supervisor Prof. Anantharama, once a week. I also discussed different aspects with the Head of the Mechanical Engineering Department Prof. B.P. Yadav. In the course of the work, I must seek their opinion time so that I knew I was on the right path to the success of the project.
Prof. Anantharama B.
Head of Mechanical Engineering Department: Prof. B.P. Yadav
Under graduate student
Laboratory Assistant (Mechanical Engg. Deptt.): Mr. Dualat Ram
Personal Workplace activity
CE1.4) I planned to do the project in two stages. The first stage deals with designing of the machine and the second stage deals with its fabrication and final assembly. In the first stage I performed design considerations of various parts of the machine. I discussed with my project guide Prof. Anantharama about various calculations required to form design procedure to determine power rating of the electric motor, design of shafts, design of belts and pulleys, design of bearings and design of fixture.
CE1.5) Before starting the designing of machine, I should get clear understanding of the working principle involved and description of various parts and processes involved in the machine. From the course of Manufacturing Process, I knew in order to get high surface quality and accuracy of shape and dimension; use of grinding process is the best option. After discussion with project supervisor and project mates I followed four factors in the selection of the grinding wheel. There were four constant factors such as material to be ground, amount of stock to be removed, area of contact and type of grinding machine. There were four variable factors such as wheel speed, work speed, condition of machine and personal factor.
CE1.6) The average length of chip formation during surface grinding was calculated as follows:
L = (D/2)*@
D=grinding wheel diameter.
@ is very small angle.
Cos @ = [(D/2)-d]/D/2=1-2d/D
D=depth of cut
Also, Cos @[email protected]/2
Comparing the equations
W=width of cut in mm.
Total volume of material removed per unit volume=F*d*W
I had used following parameters in design procedure of grinding operation:
Depth of cut, length up to 80 mm, thickness up to 3 mm and the traverse motion of the fixture for the machining process.
CE1.7) Then I put my concentration on the design procedure for determination of the power rating of the electric motor, determination of size of driven pulley, belt tension, design of belt, pitch length of the belt, determination of the cutting forces etc. By using mechanical design strategies I had calculated power rating of electric motor in the following way:
Power required for machining is given by:
Pm = Ps * Zw
Where Ps = specific cutting energy.
Zw = metal removal rate = f * ap * Vtrav
f=cross feed = 5 mm/pass
ap= back engagement
Vtrav=traverse speed =250 mm/min
Therefore, Zw = 5 * 2 * 250 =2500 mm3/min=41.66 mm3/sec
Ps=4 GJ/m3 for brass or copper alloys
Power rating = Pe=Pm/--m=166.64/0.80
Or, Pe=0.277 HP
Nearest rating available in market was 1/3 HP=247.5 watts.
CE1.8) I used following specification for the grinding wheel used in my project A-60-P-BN
60-grain size (medium)
Resinoid bond is specified
After discussion with Mechanical design lecturer (H.O.D), I used diameter of driver pulley as D=165 mm and diameter of driven pulley as d=63 mm.
Speed of motor (n) = 1420 rpm.
where, N=rpm of grinding wheel=speed of driven pulley
Wheel speed (V)=(3.14*Dw*N*60)/1000
Using standard mechanical design formulations I had calculated belt tensions on tight side and on slack side. According to calculations they were observed as follows:
T1=belt tension on tight side=11.97 N
T2=belt tension on slack side=4.2 N
Cutting forces and radial forces were calculated as follows:
Pm=166.64 Watts (power required for machining)
V=33.10m/s (wheel speed)
Radial force Fy=2*Fz
Or, Fy=10.06 N
CE1.9) Horizontal and vertical forces on the cutter shaft were calculated by the bending moment diagram and found that design was safe. Design of bearing and fixture shaft used was also safe based on the bending moment diagram. My observations at the end of design process were as follows:
Specifications of motor
Power rating=247.5 watts (1/3 HP)
Speed= 1420 rpm
Frequency=single phase, 50 Hz.
Ambient temperature=40 0C
Start capacitor=50 micro farad.
Specifications of Cutter
Diameter of cutter=170 mm.
Thickness of cutter=2mm.
CE1.10) In the second stage of the project I had done the fabrication part using team effort of my project mates. After discussion with project guide I used the following material for the various components:
Name of the component Material used
Frame C-45 steel
Shafts C-45 steel
Supports mild steel
Fixture cast iron
Tracer support mild steel
Straps cast iron
I developed engineering drawings of the cutter shaft and fixed supporting shaft. By the co-operation of the laboratory assistant fabrication of the parts was completed on time.
CE1.11) At the end of the final stage of the assembly, base plate was first welded to the angle plates. The fixture supporting was fixed in between the supports. Fixture was allowed to slide the shaft without friction with lubrication of shaft and fixture. The two straps were assembled to fixture using bolts. These two straps act as clamping device and serve the purpose of holding work piece and master piece. Then tracer support was bolted to base plate in front of one of the clamp. Now cutting wheel was mounted on the cutter shaft at one end using flanges and nut. I faced some problems while mounting grinding wheel because of un-due tightness and excessive clamping, strain was developed. But it was sort out on time.
CE1.12) The machine was based on the principle of follow up system. The purpose of this system is to provide contour on a blank with corresponding to contour on the master piece. Such a system permits rapid reproduction of same parts with a fair amount of flexibility. The project was very important for me. Firstly it was a big project I attempted for the first time in which I applied theoretical and practical knowledge of mechanical design as well as of manufacturing process to get an actual situation by designing a machine which can make duplicate key using a master key in very small time. Secondly, I got the opportunity to make creation in science field independently. Thirdly, this project enhanced my strict consideration to the science research since I made lots of calculation for designing and fabricating a machine to get better results.