DESIGN OF CRANKSHAFT
INDUSTRIAL ENGINEERING ASSIGNMENT ON
DESIGN of CRANKSHAFT
Submitted to Prof. Narayana Rao K.V.S.S. as a part of PGDIE 40 curriculum By Sunit Mhasade (Roll no: - 105) Parasram Parihar (Roll no: - 72) Sapanjit Mohanty (Roll no: - 88) Sudhir Kumar (Roll no: - 101) Ramchandra (Roll no:- 83)
2ND August 2010 Page 2 of 25
INDEX 1.
INTRODUCTION
2.
FORCES ACTING ON CRANKSHAFT
3.
MATERIAL SELECTION
4.
DESIGN PROCEDURE OF CRANKSHAFT
4.1
DESIGN PARAMETERS ASSUMED
4.2
CHEMICAL COMPOSITION
4.3
DESIGN PROCEDURE
4.4
BALANCING OF CRANKSHAFT
5. CRANKSHAFT DRAWING
6. MANUFACTURING PROCESSES
7. PROCESS FLOW CHART
8. REFERENCES
Page 3 of 25
CHAPTER -1 INTRODUCTION
Crankshaft (i.e. a shaft with a crank) is a central component of any internal combustion engine and is used to convert reciprocating motion of the piston into rotatory motion or vice versa. Crankshafts come in many shapes and sizes from small ones found in two-stroke small engines to giant ones found in diesel engines in ships. Crankshafts in automotive engines also vary, each one unique to its engine type and make. The crankshaft main journals rotate in a set of supporting bearings ("main bearings"), causing the offset rod journals to rotate in a circular path around the main journal centers, the diameter of which is twice the offset of the rod journals. The diameter of that path is the engine "stroke": the distance the piston moves up and down in its cylinder. The big ends of the connecting rods ("conrods") contain bearings ("rod bearings") which ride on the offset rod journals.
The crankshaft consists of the shaft parts which revolve in the main bearings, the crankpins to which the big ends of the connecting rod are connected, the crank arms or webs (also called cheeks) which connect the crankpins and the shaft parts.
Page 4 of 25
In the world of component design, there are competing criteria, which require the engineers to achieve a perceived optimal compromise to satisfy the requirements of their particular efforts. Discussions with various recognized experts in the crankshaft field make it abundantly clear that there is no ‘right’ answer, and opinions about the priorities of design criteria vary considerably. In contemporary racing crankshaft design, the requirements for bending and torsional stiffness (see the Stiffness vs. Strength sidebar) compete with the need for low mass moment of inertia (MMOI). Several crankshaft experts emphasized the fact that exotic metallurgy is no substitute for proper design, and there's little point in switching to exotics if there is no fatigue problem to be solved.
High stiffness is a benefit because it increases the torsional resonant frequency of the crankshaft, and because it reduces bending deflection of the bearing journals. Journal deflection can cause increased friction by disturbing the hydrodynamic film at critical points, and can cause loss of lubrication because of increased leakage through the greater radial clearances that occur when a journal's axis is not parallel to the bearing axis
The crankshaft, depending upon the position of crank, may be divided into the following two types:
1. Side crankshaft or overhung crankshaft, as shown in Fig.(a), and 2. Centre crankshaft, as shown in Fig. (b)
Page 5 of 25
Fig (a)
Fig (b)
The crankshafts are subjected to shock and fatigue loads. Thus material of the crankshaft should be tough and fatigue resistant. The crankshafts are generally made of carbon steel, special steel or special cast iron. The crankshafts are made by drop forging or casting process but the former method is more common. The surface of the crankpin is hardened by case carburizing, nitriding or induction hardening.
In this report we will be concentrating upon the design of crankshaft used in TATA Idica Vista car. The model selected is Quadrajet Aura. The engine runs on 4 cylinders. The detailed parameters of the engine are mentioned in chapter
Page 6 of 25
CHAPTER -2 FORCES IMPOSED ON A CRANKSHAFT Our selected engine is Combustion Ignition Diesel Engine. The obvious source of forces applied to a crankshaft is the product of combustion chamber pressure acting on the top of the piston. High-performance, contemporary highperformance Compression-Ignition (CI) engines can see combustion pressures in excess of 200 bar (2900 psi) which will produce a force of 16529 Kgs acting on a small 4.00 inch diameter piston. This kind of huge force exerted onto a crankshaft rod journal which produces substantial bending and torsional moments and the resulting tensile, compressive and shear stresses. However, there is another major source of forces imposed on a crankshaft, namely Piston Acceleration. The combined weight of the piston, ring package, wristpin, retainers, the conrod small end and a small amount of oil are being continuously accelerated from rest to very high velocity and back to rest twice each crankshaft revolution. Since the force it takes to accelerate an object is proportional to the weight of the object times the acceleration (as long as the mass of the object is constant), many of the significant forces exerted on those reciprocating components, as well as on the conrod beam and big-end, crankshaft, crankshaft, bearings, and engine block are directly related to piston acceleration. Combustion forces and piston acceleration are also the main source of external vibration produced by an engine.
In addition to these reciprocating forces and the resulting moments, there is a rotating mass associated with each crankpin, which must be counteracted. The rotating mass consists of the weight of the conrod big end(s), conrod bearing(s), some amount of oil, and the mass of the crankshaft structure comprising the crankpin and cheeks. These rotating forces are counteracted by counterweight masses located in appropriate angular locations opposing the rod journals
Page 7 of 25
CHAPTER -3 MATERIAL SELECTION Medium-carbon steel alloys are composed of predominantly the element iron, and contain a small percentage of carbon (0.25% to 0.45%, described as ‘25 to 45 points’ of carbon), along with combinations of several alloying elements, the mix of which has been carefully designed in order to produce specific qualities in the target alloy, including hardenability, nitridability, surface and core hardness, ultimate tensile strength, yield strength, endurance limit (fatigue strength), ductility, impact resistance, corrosion resistance, and temperembrittlement resistance. The alloying elements typically used in these carbon steels are manganese, chromium, molybdenum, nickel, silicon, cobalt, vanadium, and sometimes aluminium and titanium. Each of those elements adds specific properties in a given material. The carbon content is the main determinant of the ultimate strength and hardness to which such an alloy can be heat treated. In converting the linear motion of the piston into rotational motion, crankshafts operate under high loads and require high strength. Crankshafts require the following characteristics
High strength and stiffness to withstand the high loads in modern engines, and to offer opportunities for
downsizing and weight
reduction Resistance to fatigue in torsion and bending Low vibration Resistance to wear in the bearing areas
Thus the forged steel crankshafts offer higher strength and stiffness and the other material characteristics than the cast iron alternative
Page 8 of 25
CHAPTER -4 DESIGN PROCEDURE Bearing Pressures and Stresses in Crankshaft The bearing pressures are very important in the design of crankshafts. The maximum permissible bearing pressure depends upon the maximum gas pressure, journal velocity, amount and method of lubrication and change of direction of bearing pressure. The following two types of stresses are induced in the crankshaft. 1. Bending stress ; and 2. Shear stress due to torsional moment on the shaft
The following procedure may be adopted for designing a crankshaft.
1. The crankshaft must be designed or checked for at least two crank positions. Firstly, when the crank-shaft is subjected to maximum bending moment and secondly when the crankshaft is subjected to maximum twisting moment or torque. 2. The additional moment due to weight of flywheel, belt tension and other forces must be considered. 3. It is assumed that the effect of bending moment does not exceed two bearings between which a force is considered.
4.1) DESIGN PARAMETERS ASSUMED Now, we have to design the crankshaft required for TATA Indica vista car. We have selected Quadrajet AURA model. The technical specifications are as mentioned below... TATA INDICAVISTA: Model: QUADRAJET AURA Number of Cylinders Type of Engine ( Inline / ‘Vee’ engine ) Bore / Stroke (D/L) Cylinder spacing
4 Cylinder, SDE Common Rail, 1248 cc, Inline Diesel, 475IDI engine 69.6 / 82 assume Page 9 of 25
Power @ speed Torque @ speed Reciprocating mass ( Piston Assy + Con.rod reci.mass ) Rotating mass ( Con.rod rotating mass + Crank mass ) Connecting rod length Compression ratio Engine type
75 PS (55KW)@ 4000 rpm 190 Nm@ 1750 RPM Assume Assume Assume 17.6 :1 Compressor Ignition (CI) Engine
Lets us assume the other [parameters required for designing of crankshaft as below... Mass of piston mass of connecting rod crankpin mass Mass of web Centre Of Gravity radius Crank radius reciprocating mass rotating mass ratio of r/l – λ Cylinder pitch Weight of flywheel
1.36 0.60 0.25 0.25 37.96 39.5 1.56 1.12 0.31 84.00 1 .00
kg kg kg kg mm mm kg kg mm Kg
Page 10 of 25
4.2) CHEMICAL COMPOSITION OF CRANKSHAFT
Thus the material used for crankshaft of Indica Vista 475 IDI engine is 40Cr4Mo3 The complete chemical composition of the material is as given below...
4.3) DESIGN PROCEDURE Based on the chemical composition of the material we will now design the crank shaft dimensions. Thus the design of crankshaft is to be made by considering the two positions of crank. A. when the crank is at dead centre (or when the crankshaft is subjected to maximum bending moment) and B. When the crank is at angle at which the twisting moment is maximum.
Page 11 of 25
A)
When the crank is at dead centre At this position of the crank, the maximum gas pressure on the piston will transmit maximum force on the crankpin in the plane of the crank causing only bending of the shaft. The crankpin as well as ends of the crankshaft will be only subjected to bending moment. Thus, when the crank is at the dead centre, the bending moment on the shaft is maximum and the twisting moment is zero. The various forces that are acting on the crankshaft are indicated as below.. This engine crankshaft is a single throw and three bearing shaft located at position 1, 2 & 3.Lets us assume following data for engine
We can calculate the various forces acting on crank shaft connecting rod (Fp), Horizontal and vertical reactions on shaft, and the resultant force at bearing 2 & 3 by below formulae.
Now the piston force Pmax = P * no of cylinders 1248 *10-6*4000 = 55*4/1248*10-6*4000 = 44.07
Page 12 of 25
Piston force Fp
= π/4 * D2*p = π/4*(69.6)2*44.07 = 167.67 KN
Assuming the distance between the bearing 1 &2 as b = 2D = 2*69.6 = 13902 mm b1 = b2 = b/2 = 69.6 We know that due to piston gas load, there will be two equal horizontal reactions H1 & H2 at bearings 1 & 2 respectively.. i.e
H1 = Fp/2 = 167.66/2 = 83.83 kN= H2
Assuming that the length of bearing to be equal i.e. c1=c2=c/2 We know that due to weight of flywheel acting downwards, there will be two vertical reactions V2 & V3 at bearings 2 & 3 V2 = V1 = W/2 = 9.8/2 = 4.9 N Since, the belt is absent in engine, neglecting the belt tension exerted by belt. i.e.
T1 + T2 = 0
Now, lets design various parts of crankshaft (a) Design of crank pin Crankpin is also subjected to shear stress due to twisting moment. Thus we can calculate bending moment at centre of crankpin and twisting moment on crank pin and the resultant moment. Let,
dc = Diameter of crank pin in mm lc = length of crank pin σallow = allowable bearing stress for crank pin = 83 kg/mm2
Bending moment at the centre of crank pin is Mc = H1 * b2 = 83.83 * 69.6 = 5834.56 kN mm Page 13 of 25
We know that Mc = π/32 * (dc)3 * σb 5834.56 x 103 = π/32 * (dc)3 * 83 dc = 89.46 mm say 90 mm Now, the length of crank pin lc = Fp/(dc*pb) = 167.67x103 / (90 * 10) = 186.28 mm
--
(say pb =10)
(b) Design of left hand crank web The crank web is designed for eccentric loading. There will be two stresses acting on the crank web, one is direct compressive stress and the other is bending stress due to piston gas load (Fp). The crank web is subjected to the following stresses: i. Bending stresses in two planes normal to each other, ii. Direct compressive stress and iii. Torsional stress We know that the thickness of crank web is t = 0.65 *dc + 6.35 = 0.65* 90 + 6.35 = 64.85 = say 65 mm Also width of crank web is, w = 1.125 * dc +12.7 = 1.125 * 90 +12.7 = 113.95 = say 115 mm The maximum bending moment on crank web is Mmax = H1 (b2 –lc/2-t/2) = 83.83 (69.6- 186.28/2-65/2) = - 4697.83 kN mm The bending moment is negative; hence the design is not safe. Thus the dimensions are on higher side.
Now lets assume,
hence,
dc lc
= 45 mm = 372.57 mm
Page 14 of 25
This is very high, which will require huge length of crank shaft. To have optimum dimension of crankshaft lets assume length of crank web as. lc = 24 mm and check whether these dimensions are suitable for the load exerted by the piston, & other forces Now,
t w
= 35.6 & = 63.32 = say 68 mm
This thickness is also on higher side, lets assume thickness of crank web as t = 13.2 mm As compared to width of crank web thickness is more Bending moment, M = 4275.33 kN mm Section modulus Z = 1/6 *w*t2 = 1/6 * 68 * 13.22 = 1974.72 mm3 Bending stress, σb = M/Z σb = 2.165 kN/mm2 The compressive stress acting on crank web are σc = H1 / (w*t) = 83.83 / (68 * 13.2) = 0.09339 kN/ mm2 The total stress acting on crank web is σT = σb + σc = 2.2583 kN/ mm2 Thus total stress on crank web is less than allowable bending stress of 83 N/mm2 Hence, the design is safe (c) Design of right hand crank web From balancing point of view, the dimensions of right hand crank web i.e thickness and width are made equal to the dimensions of left hand crank web
Page 15 of 25
(d) Design of shaft under flywheel There are two types of bending moments acting on shaft. Bending moment due to weight &, bending moment due to belt tension. Neglecting the belt tension, lets design shaft diameter... Let, ds = diameter of crank shaft Since the length of bearings are equal l1= l2 = l3 = 2(b/2-lc/2-t) = 2(139.2/2- 24/2-13.2) = 88.8 mm Assuming the width of flywheel = 200 mm C = 88.88 + 200 = 288.88 mm Cosidering the space for gearing and clearance, Let C = 300 mm Bending moment due to weight of flywheel , Mb = V3 * C = 4.9 x 103* 300 = 1470 x 103 kN mm Also the bending moment of shaft is Ms = π/32 * ds3 * σallow 1470 x 103 = π/32 * ds3 * 83 ds = 56.50 mm say 60 mm B)
When the crank is at an angle of maximum twisting moment The twisting moment on the crankshaft will be maximum when the tangential force on the crank (FT) is maximum. The maximum value of tangential force lies when the crank is at angle 30º to 40º for constant pressure combustion engines (i.e. diesel engines). When the crank is at angle at which the twisting moment is maximum, the shaft is subjected to twisting moment from energy or force stored by flywheel. The above design parameters can be cross checked for the factor of safety while designing by considering the crankshaft at an angle of maximum twisting moment. If the factor of safety is more than 1 then the design is safe. Considering this, we have to various forces acting on crankshaft at different twisting angles.
Page 16 of 25
4.4)
BALANCING OF CRANKSHAFT
The crankshaft and the connecting-rod convert the reciprocating motion of the piston into one of rotation. The crankshaft is made very stiff, since it is subjected to severe and varying twisting and bending stresses, due to the combustion pressures and also to the “inertia” effects of the reciprocating parts. The latter effects are the forces due to the acceleration and deceleration of the piston and connectingrod in their strokes. The twisting or turning action on the crankshaft, which is generally spoken of as the Torque, is constantly changing; this fact necessitates a stronger shaft than for a steady motion. The manner in which the torque varies in the case of a single cylinder engine is as shown in below graph.
It will be observed that firing stroke gives the greatest torque. In this case the greatest torque is no less than 8 times the mean value. These vibrations are caused by the irregular turning or torques on the crankshaft, due to the firing strokes of the different cylinders. This force tends to twist the crankpin ahead of the rest of the crankshaft. And when the force against the crankpin recedes, it tends to untwist or move back into its original relationship with the rest of the crankshaft. This twist – untwist action, repeated with every power impulse, tends to set up an oscillating motion in the crankshaft To absorb these uneven forces and the output end of crankshaft is connected with flywheel. The flywheel absorbs the uneven torques/ forces and transmits the power smoothly. Let us calculate the various forces acting on Page 17 of 25
crankshaft at each change in angle of crank when the piston changes its position. Our engine is having 4 cylinders; hence, the forces induced at each change in angle of crank at each location of cylinder are to be derived. Consider following data for calculating the horizontal, vertical, rotating and counter forces. After analysing various parameters the various forces acting on crankshaft at different twisting angles are calculated as below... Crank Angle
First
Second
order
Order
Cylinder 1 Rotaing Force
Conter Force Vert. Dirn -341.08
Second Order
Cylinder 2 Rotaing Force
Horz. Dirn 0.00
Force
Force
-675.16
209.99
Vert. Dirn -485.25
Conter Force
Horz. Dirn 0.00
Vert. Dirn 341.08
First
Second
Order
Order
Cylinder 3 Rotaing Force
Horz. Dirn 0.00
Force
Force
-675.16
209.99
Vert. Dirn -485.25
Conter Force
Horz. Dirn 0.00
Vert. Dirn 341.08
Horz. Dirn 0.00
Cylinder 4 Rotaing Force
First
Second
Order
Order
Force
Force
675.16
209.99
Vert. Dirn 485.25
Conter Force
force
Force
0.0
675.16
209.99
Vert. Dirn 485.25
1.0
675.06
209.86
485.17
8.47
-341.03
-5.95
-675.06
209.86
-485.17
-8.47
341.03
5.95
-675.06
209.86
-485.17
-8.47
341.03
5.95
675.06
209.86
485.17
8.47
-341.03
-5.95
2.0
674.75
209.48
484.95
16.93
-340.87
-11.90
-674.75
209.48
-484.95
-16.93
340.87
11.90
-674.75
209.48
-484.95
-16.93
340.87
11.90
674.75
209.48
484.95
16.93
-340.87
-11.90
3.0
674.24
208.84
484.58
25.40
-340.61
-17.85
-674.24
208.84
-484.58
-25.40
340.61
17.85
-674.24
208.84
-484.58
-25.40
340.61
17.85
674.24
208.84
484.58
25.40
-340.61
-17.85
4.0
673.52
(θ)
Horz. Dirn 0.00
First Order
Horz. Dirn 0.00
Vert. Dirn -341.08
Horz. Dirn 0.00
207.95
484.06
33.85
-340.25
-23.79
-673.52
207.95
-484.06
-33.85
340.25
23.79
-673.52
207.95
-484.06
-33.85
340.25
23.79
673.52
207.95
484.06
33.85
-340.25
5.0
672.59
206.80
483.40
42.29
-339.78
-29.73
-672.59
206.80
-483.40
-42.29
339.78
29.73
-672.59
206.80
-483.40
-42.29
339.78
29.73
672.59
206.80
483.40
42.29
-339.78
-29.73
88.0
23.56
-209.48
16.93
484.95
-11.90
-340.87
-23.56
-209.48
-16.93
-484.95
11.90
340.87
-23.56
-209.48
-16.93
-484.95
11.90
340.87
23.56
-209.48
16.93
484.95
-11.90
-340.87
89.0
11.78
-209.86
8.47
485.17
-5.95
-341.03
-11.78
-209.86
-8.47
-485.17
5.95
341.03
-11.78
-209.86
-8.47
-485.17
5.95
341.03
11.78
-209.86
8.47
485.17
-5.95
-341.03
0.00
-485.25
0.00
341.08
0.00
-209.99
0.00
-485.25
-23.79
90.0
0.00
-209.99
0.00
485.25
0.00
-341.08
0.00
-209.99
0.00
341.08
0.00
-209.99
0.00
485.25
0.00
-341.08
91.0
-11.78
-209.86
-8.47
485.17
5.95
-341.03
11.78
-209.86
8.47
-485.17
-5.95
341.03
11.78
-209.86
8.47
-485.17
-5.95
341.03
-11.78
-209.86
-8.47
485.17
5.95
-341.03
92.0
-23.56
-209.48
-16.93
484.95
11.90
-340.87
23.56
-209.48
16.93
-484.95
-11.90
340.87
23.56
-209.48
16.93
-484.95
-11.90
340.87
-23.56
-209.48
-16.93
484.95
11.90
-340.87
178.0
-674.75
209.48
-484.95
16.93
340.87
-11.90
674.75
209.48
484.95
-16.93
-340.87
11.90
674.75
209.48
484.95
-16.93
-340.87
11.90
-674.75
209.48
-484.95
16.93
340.87
-11.90
179.0
-675.06
209.86
-485.17
8.47
341.03
-5.95
675.06
209.86
485.17
-8.47
-341.03
5.95
675.06
209.86
485.17
-8.47
-341.03
5.95
-675.06
209.86
-485.17
8.47
341.03
-5.95
180.0
-675.16
209.99
-485.25
0.00
341.08
0.00
675.16
209.99
485.25
0.00
-341.08
0.00
675.16
209.99
485.25
0.00
-341.08
0.00
-675.16
209.99
-485.25
0.00
341.08
181.0
-675.06
209.86
-485.17
-8.47
341.03
5.95
675.06
209.86
485.17
8.47
-341.03
-5.95
675.06
209.86
485.17
8.47
-341.03
-5.95
-675.06
209.86
-485.17
-8.47
341.03
5.95
182.0
-674.75
209.48
-484.95
-16.93
340.87
11.90
674.75
209.48
484.95
16.93
-340.87
-11.90
674.75
209.48
484.95
16.93
-340.87
-11.90
-674.75
209.48
-484.95
-16.93
340.87
11.90
268.0
-23.56
-209.48
-16.93
-484.95
11.90
340.87
23.56
-209.48
16.93
484.95
-11.90
-340.87
23.56
-209.48
16.93
484.95
-11.90
-340.87
-23.56
-209.48
-16.93
-484.95
11.90
340.87
269.0
-11.78
-209.86
-8.47
-485.17
5.95
341.03
11.78
-209.86
8.47
485.17
-5.95
-341.03
11.78
-209.86
8.47
485.17
-5.95
-341.03
-11.78
-209.86
-8.47
-485.17
5.95
341.03
270.0
0.00
-209.99
0.00
-485.25
0.00
341.08
0.00
-209.99
0.00
485.25
0.00
-341.08
0.00
-209.99
0.00
485.25
0.00
-341.08
0.00
-209.99
0.00
-485.25
0.00
271.0
11.78
-209.86
8.47
-485.17
-5.95
341.03
-11.78
-209.86
-8.47
485.17
5.95
-341.03
-11.78
-209.86
-8.47
485.17
5.95
-341.03
11.78
-209.86
8.47
-485.17
-5.95
341.03
272.0
23.56
-209.48
16.93
-484.95
-11.90
340.87
-23.56
-209.48
-16.93
484.95
11.90
-340.87
-23.56
-209.48
-16.93
484.95
11.90
-340.87
23.56
-209.48
16.93
-484.95
-11.90
340.87
358.0
674.75
209.48
484.95
-16.93
-340.87
11.90
-674.75
209.48
-484.95
16.93
340.87
-11.90
-674.75
209.48
-484.95
16.93
340.87
-11.90
674.75
209.48
484.95
-16.93
-340.87
11.90
359.0
675.06
209.86
485.17
-8.47
-341.03
5.95
-675.06
209.86
-485.17
8.47
341.03
-5.95
-675.06
209.86
-485.17
8.47
341.03
-5.95
675.06
209.86
485.17
-8.47
-341.03
360.0
675.16
209.99
485.25
0.00
-341.08
0.00
-675.16
209.99
-485.25
0.00
341.08
0.00
-675.16
209.99
-485.25
0.00
341.08
0.00
675.16
209.99
485.25
0.00
-341.08
0.00
361.0
675.06
209.86
485.17
8.47
-341.03
-5.95
-675.06
209.86
-485.17
-8.47
341.03
5.95
-675.06
209.86
-485.17
-8.47
341.03
5.95
675.06
209.86
485.17
8.47
-341.03
-5.95
362.0
674.75
209.48
484.95
16.93
-340.87
-11.90
-674.75
209.48
-484.95
-16.93
340.87
11.90
-674.75
209.48
-484.95
-16.93
340.87
11.90
674.75
209.48
484.95
16.93
-340.87
-11.90
0.00
341.08
5.95
Thus performance of the resultant vertical and horizontal forces for the balancing of crankshaft can be plotted as below... Vert Component Horz Component
Resultant moment acting between cylinder 1 & 2 80.00
Moment of Force (N-m)
60.00 40.00 20.00 0.00 -20.00 0
90
180
270
360
450
540
630
720
-40.00 -60.00 -80.00 Crank Angle
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CHAPTER -5 CRANKSHAFT DRAWING Thus, after conducting successful balancing test we can say the design is satisfactory for given loads. The final dimensions of the crankshaft are as given below.
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CHAPTER -6 MANUFACTUTING PROCESSES Crankshaft is usually outsourced for production by the automobile industry. Belgaum in Karnataka is the home of the biggest cluster of crankshaft machining units in India. The units are mainly deploying the old-fashioned turning process for machining of the pin and web portions in a crankshaft. This requires multiple set-ups of the component in the machine. In the process, crankshafts have to be loaded on different machines with special work holding fixtures to complete the machining task. All this takes considerable amount of time and also results in inconsistent component accuracies due to the different set-ups. Material for crankshaft is forged steel of specifications 40Cr4Mo3. The major manufacturing operations are given below.. Operation Description no 005 Forging Inspection: The appropriate crankshaft material in the form of forging will be received from stores and visually inspected as per the drawing and placed in workplace area. 020 Crank web milling Journal Milling, Crank pin 025 milling: 030 There is special type of milling cutter used for 035 journal & crankpin milling, as shown. This cutter is of a special design with cartridges mounted on the periphery and sides for simultaneous milling of the pin and web of a crankshaft. The spindle is driven through a gearbox by a 37kW motor. The spindle head is mounted on slide units, which are driven by servomotors through ball and lead screws. While one of the servomotors controls the feed movement of the cutter, another one is used to index the milling head in various positions. The spindle head slide is provided with a hydraulic counterbalance system.
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045 050
080 090 095
070 105
075
125
130
140
Drilling :
Drilling of crossed oil Drilling of crankpin Drilling of flywheel hole flange Grinding: Surface grinding is done for journal, main journal and crank pin. One of the critical steps in the manufacturing of forged steel crankshafts is the grinding of the sidewalls. Crack detection Since the material is forging there is possibility that the material may have internal flaws which will be exposed during machining. Hence before sending material for further operations the cracks are detected by magnaflux method Nitriding A case hardening process that depends on the absorption of nitrogen into the steel. a much higher surface hardness is obtainable when compared with case-hardening steels; they are extremely resistant to abrasion and have a high fatigue strength. Dynamic Balancing
Lapping and super finish The crankshaft surface is ground to super finish so as to avoid cyclic fatigue failure of crankshaft due to any surface cracks, burrs. Journal Grading and bearings selection Generally the bearings are selected as per the shaft / crankpin diameter. If shaft dia slightly lesser than the recommended bearing size then the next bearings are selected and the diameter is changed according to bearing size. The top and bottom bearing and its selection on crank shaft is as shown below...
The complete process chart is as given below... Page 21 of 25
CHAPTER -7 PROCESS FLOW DIAGRAM
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CRANKSHAFT ASSEMBLY
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CHAPTER -8 REFERENCES
1. http://knol.google.com 2. http://cars.tatamotors.com 3. Machine Design by Sri R S Khurmi and Sri. J K Gupta, Chapter-32 Internal Combustion Engine parts 4. http://www.scribd.com 5. http://www.wikipedia.org 6. www.corusengineeringsteels.com 7. http://www.epi-eng.com/ 8. http://www.peterburford.com.au/crankshaft.php 9. Advanced design for crankshaft and sliding bearings in reciprocating engines by Elena Galindo, R&D and Product Engineering Department, COJINETES DE FRICCION, Madrid, Spain 10. Design and Development of the Valve Train for a Racing Motorcycle Engine by Steve Sapsford
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