pipe bending

AProject Report On

DESIGN AND FABRICATION OF SHEET METAL ROLLING MACHINE

Submitted By

HARSHDEEP SINGH

INAYATULLAH FAROOQUI

Under the guidance of

Prof. ALVI

Mr. H. Vishwakarma

Submitted as a partial fulfillment of

Bachelor of Engineering B.E. (Semester VIII), MECHANICAL

[2013 - 2014] from

Rizvi College of Engineering New Rizvi Educational Complex, Off-Carter Road,

Bandra(w), Mumbai - 400050

Affiliated to

University of Mumbai

CERTIFICATE

This is certify that the project report entitled "Title of the Project"

Submitted By

HARSHDEEP SINGH INAYATULLAH FAROOQUI

of Rizvi College of Engineering, MECHANICAL has been approved in partial fulfillment of require- ment for the degree of Bachelor of Engineering.

Prof. ALVI Prof.Mr. H. Vishwakarma Internal Guide External Guide (If any)

Prof.Hussain Dr. Varsha Shah Head of Department Principal

Prof. ———————- Prof. ———————— Internal Examiner External Examiner

Date:

Acknowledgement

Put your acknowledgement here. Refer below for a sample.

I am profoundly grateful to Prof. Alvi for his expert guidance and continuous encouragement throughout to see that this project rights its target since its commencement to its completion.

I would like to express deepest appreciation towards Dr. Varsha Shah, Principal RCOE, Mumbai and Prof. Hussain, HoD MECHANICAL whose invaluable guidance supported me in completing this project.

I am particularly grateful to Mr. H. Vishwakarma (BISHNU AND CO.) who allows me to work in the company.

At last I must express my sincere heartfelt gratitude to all the staff members of MECHANICAL who helped me directly or indirectly during this course of work.

HARSHDEEP SINGH

INAYATULLAH FAROOQUI

ABSTRACT

The component that can be manufactured using 3-roller bar bending machine are circular washer having internal radius more than 150mm, circular collars, component used for balancing of wind tower assembly, high stiffness spiral spring, etc. For parametric specification of 3-point bar bending machine, it is necessary to analyze the stress induced in rollers and gear teeth radial force. Thus Finite element modeling is necessary and suitable software must be selected for analysis and observation.There are many useful software are available in the market like ANSYS V-13, LS DYNA, ABAQUS and soon. Hence the 3-point bending machine consists of number of individual parts which to be model and assembled. The AUTODESK INVENTOR professional 2013 is best suitable for modeling of this machine (AUTODESK provides ease of man-machine interface, mating of parts both transitional to rotational, constrain edge- surface etc.). It also assists for part detailing and presentation.The finite element analysis is carried out using ABAQUS 6.10 for solving stress distribution across the rolling rollers with billet displacement of 67mm, stress distribution with roller rotation, Gear drive analyses for minimum load case without billet and Gear drive analyses for maximum load case with billet thickness. It also requires the gear train mechanism with the motor to drive roller, to transfer torque to overcome the vertical load acting during operation, and speed reduction for ease bending & rolling process. Thus analysis of load acting on the gear tooth is necessary to set the minimum inside radius of roll for 3-roller bending machine.

Keywords :Bar Bending Machine, Autodesk Inventor, Hyper Mesh, Abacus 6.1, Stress Analysis, and Spur Gear

Contents

1 Introduction 11.1 PROBLEM DEFINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 LITERATURE REVIEW 3

3 PROCESS OF ROLLING 4

4 STRESSES INDUCED IN SHEET METAL 64.1 Stresses in tangential direction and inner moment bending calculus . . . . . . . . . . .

64.2 Stresses in tangential direction and inner moment bending calculus . . . . . . . . . . . 8

5 A Design process 12 5.0.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.0.2 Concept of Iteration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.0.3 Definition Stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.0.4 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.0.5 Preliminary stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.0.6 Manually operated pipe bending machine . . . . . . . . . . . . . . . . . . . . . 15

6 Lead screw 17 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.2 Design for Lead Screw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.3 Assumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.4 POWER SCREW FORCE AND TORQUE ANALYSIS . . . . . . . . . . . . . . . . . . 18 6.5 INSIGHT OF THREAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6.5.1 DETERMINATION OF THE FORCES WHICH ARE ACTING . . . . . . . . 18 6.6 STRESS IN THREAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6.6.1 Axial Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.6.2 Shear stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6.6.3 TORSIONAL STRESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6.7 MANUFACTURING FASTENERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.7.1 THREAD ROLLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.7.2 ADVANTAGE OF ROLLING V/S CUTTING . . . . . . . . . . . . . . . . . . 21 6.7.3 HEAD FORMING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.7.4 STRENGTH OF STANDARD BOLTS . . . . . . . . . . . . . . . . . . . . . . 22

7 GEAR 23 7.1 INTRODUCTION: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.2 GEAR NOMENCLATURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7.3 GEAR TOOTH THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7.4 FUNDAMENTAL LAW OF GEARING . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7.5 The Involute Tooth Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.6 Mesh Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 7.7 Changing Center Distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.8 DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7.8.1 Assumptions: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 7.8.2 Virtual Number of teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.9 Lubrication in gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.10 Manufacturing of gears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7.10.1 Forming Gear Teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7.10.2 Casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 7.10.3 Machining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 7.10.4 Roughing Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 7.10.5 Finishing Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

8 Bearing 30 8.1 Material Combination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 8.2 Thrust Bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 8.3 Bearing Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

9 Rollers and Idlers 33 9.1 Shaft loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 9.2 Attachments and Stress concentrations . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

9.2.1 Designing to Avoid Stress Concentrations . . . . . . . . . . . . . . . . . . . . . 34 9.3 Force Flow analogy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 9.4 Design considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

10 Coupling 37 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 10.2 Rigid flange coupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

11 Gear reduction box 42

12 Power unit Assembly 44

13 Modelling 46 13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

14 Future scope of Project 49

15 Test Cases, Project Time Line & Task Distribution 51 15.1 Test Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

15.1.1 Case 1: Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 15.1.2 Case 2: Procurement of parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 15.1.3 Case 3: Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

15.1.4 Case 4:Load testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 15.2 Project Time Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

References 52

APPENDICES 52

A Project Hosting 53

List of Figures

1.1 three roller bending machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 manual pipe bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3.1 Process of rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.2 Steps in rolling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 Radial distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 4.2 mechanical scheme of processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 4.3 Plastic bending stress distribution system . . . . . . . . . . . . . . . . . . . . . . . . .7 4.4 Bending scheme on bending roll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 4.5 .- Bending moments at the plastic bending with cold-hardening. . . . . . . . . . . . . .9 4.6 Scheme of positioning rollers with three and four symmetrical rollers. . . . . . . . . . . 11

5.1 5.2

6.1

8.1 8.2 8.3

9.1 9.2 9.3

A DESIGN PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Manually operated pipe bending machine . . . . . . . . . . . . . . . . . . . . . . . . . 16

ACME Thread profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Material comination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Thrust bearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Bearing mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Roller and Idler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Force flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Method to remove stress concentration . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

10.1 Rigid protected typeflange section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

11.1 Details of reduction box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

12.1 Induction motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 12.2 Comparison table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Chapter 1 Introduction

Chapter 1

Introduction

It has been seen that the 3-roller bending machines are widely using in many industries for many different applications such as, sheets are bent and roll to form a shell like structure which are used in pipe line. I & L channel are bending to a required angle used to form structural stress (roofing) in construction industries. Some of them are used for conical bending which are costly to produce using conventional machines. As discussed above the two rollers A & B are connected to the shaft and are driven by the gears, each rollers are interconnected by individual gear having same number of teeth on it to facilitate same rotary motion to it. For construction of various structures as well as integral part of machines

Figure 1.1: three roller bending machine

various cylindrical sections are widely used. Such cylindrical sections are manufactured by various methods and 3-roller conical bending process is one such process. It consists of two bottom rollers and a top roller. Metal plates with specified contours are rolled without decrease in thickness to get the desired cone angle. The plate undergoes plastic deformation and it is cold forming process and hence it has higher. Dimensional accuracy. 3-roller shell bending process has four stages:

1. static bending,

2. forward rolling,

3. backward rolling, and 4.

unloading.

The motor used here to generate a required torque consists of 7.5 HP with 960 rpm of speed. We know that thisspeed cannot be used directly as a output speed and the torque obtain from this motor is also very less, so tomanipulate the value of torque and to reduce the input speed on to the roller A&B a proper gear train is necessary. Thisgear train is properly designed and used in this 3-roller bar bending machine.A component for balancing of wind blades & wind tower assembly can easily mass produced by the application of3-point bar bending machine. A unique process for manufacturing the above circular component is divided into 3 steps(clearly explained in component chapter). It was estimated that the processing speed for manufacturing this component by3-point bar bending machine can greatly advance

Rizvi College of Engineering, Bandra, Mumbai. 1

Chapter 1 Introduction

by the amount of around 30 to 40% than that of using conventionalmachine. Although the use of raw material for above manufacturing purposes is minimized up to 35-55%both conditionwill sets the component MRP with lesser cost. This idea brought the Bishnu and co. to process the abovecomponent by using 3-roller bar bending machine.

1.1 PROBLEM DEFINATION

By reviewing all the above paper brings further experimental study on 3-roller bar bending machine. This study shows the bending of bar into required radius of curvature having greater thickness with shorter width. Bending of this thick sheet executes higher load on center roller of machine. As the thickness of the sheet increases the load acting on the top roller also increases, thus for rolling of thick material brings changes in design parameter (mainly on sheet thickness t). Hence, this problem can be related to bending of rectangular bar at the mid span and bending moment equation. Consider abar having a depth & width of 207 respectively is to be bend in a circular curve by radius R (i.e. radius of curvature). Baris made up of mild steel having youngs modulus of E=2.1GPa (210KN/mm2).

By visualizing the figure we can state that the load acting on the above roller is more than the roller acting as a resistance to bend (A & B).

Thus the steps executing on this problem are listed below:

• Analytical calculation of load and stress acting on the rollers.

• Calculation of required deflection at the mid span which is required to bent the bar to obtain radius

of curvature R.

• Design of gears and gear trains.

• Calculation of speed reduction factor from input to the output •

Estimating of torque for input motor power.

• Modelling parts and assembly of 3-roller bar bending machine. •

Analyzing of stress distribution across rollers.

• Analyses of radial load on gear & pinion contact tooth

Figure 1.2: manual pipe bending


Chapter 2 LITERATURE REVIEW

Chapter 2

LITERATURE REVIEW

Himanshu: Himanshuhas done bendability analysis for bending of steel plates on heavy duty 3-roller bendingma- chine. In this experiment they found out the equivalent thickness, equivalent width and maximum width analytically &based on power law material model. Ahmed Ktari: have done Modeling and computation of the three-roller bending process of steel sheets.This experiment consists of two-dimensional finite element model of this process was built under the Abaqus /Explicit environment based on the solution of several key techniques, such as contact boundary condition treatment, material property definition, meshing technique, and so on. Jong GyeShin: has done the experiment on Mechanics-Based Determination of the Center RollerDisplacement in Three- Roll Bending for Smoothly Curved Rectangular Plates. The objective of this paper is to develop a log- ical procedure to determine the center roller displacement, in the three-roll bending process, which is required in the fabrication of curved rectangular plates with a desired curvature. M K Chudasama: have done the experiment on Analytical Model for Prediction of Force during 3-RollerMulti-pass Con- ical Bending. In this paper, the total deflection of the top roller required is divided in steps to get the multipassbending. M. B. Bassett, and W. Johnson: The bending of plate using a three rollpyramid type plate bending machine, J. strain Analysis

Processmanual, maintenance manual, machine capacity chart and technical specification of rolling- machine,M/s Larsen& Toubro ltd,Hazira, Surat, India.


Chapter 3 PROCESS OF ROLLING

Chapter 3

PROCESS OF ROLLING

In the first stage the plate is kept between top roller and bottom rollers as shown in Figure and the top roller is given vertical displacement to get the required bend. In next stage the bottom rollers are driven using motors in forward direction to get the roll bending of the plate. Similarly the rollers are driven in reverse direction to get better dimensional accuracy of the final product. The bent plate is than unloaded by raising the top roller. For continuous single-pass four roll thin plate bending a model was proposed considering the equilibrium of the internal and external bending moment at and about the plate-top roll contact. They had considered varying radius of curvature for the plate between the rollers and proposed a mathematical model to simulate the mechanics in a steady continuous bending mode for four-roll thin plate bending process and also investigated Influence of material strain hardening on the mechanics of steady continuous roll and edge-bending mode in the four-roll plate bending process For continuous multi-pass bending of cylinder on 3-roller bending machines with non compatible (cylindrical) rollers, Gandhi et al. had reported the formulation of spring back and machine setting parameters They incor- porated the effect of change of flexural modulus during the deformation in the formulation to study the effect on spring back prediction. For plane strain flow of sheet metal subjected to strain rate effects during cyclic bending under tension He also included

Figure 3.1: Process of rolling

Bauschinger factors in the model for stress reversal. The roll bending process is used for years, it can be observed from the literature reviewed that conical bending process is untouched area as far as force prediction is concerned. Even in the industries the normal practice of plate roller bending still heavily depends uponthe experience and the skill of the operator. Working to templates, or by trial and error.


Chapter 3 PROCESS OF ROLLING

Figure 3.2: Steps in rolling


Chapter 4 STRESSES INDUCED IN SHEET METAL

Chapter 4

STRESSES INDUCED IN SHEET METAL

The working by bending of work-pieces creates inner of this in deformed zone stresses in tangential and radial directions. The metal strata placed to curving center are pressed in tangential directions, becoming shorter and in especially cases are stretchingin transversal direction. The metal strata placed to external piece are stretching in tangential direction and in especially cases are pressed in transversal direction, making the piece narrowing. Between the stretching and pressing strata is founded the neutral stratus M-N . The neutral status with the radius nis founding displaced to the curving center before the weight center, what is placed on the median arc with radius m. The radius value where the tangential direction stresses are null and is not produced the deformation in tangential direction is determined by the following relation.

Figure 4.1: Radial distribution

Practically, it is considered that the neutralstratus position coincides with the medianstratus with nradius when the relativeradius bending has the value.

4.1 Stresses in tangential direction and inner moment bending calculus

200and even less, theinfluence exercised by elastic deformation ofmaterial near neutral stratus very little, thus can be considered that the plastic deformation zone are spreading until neutral stratus,corresponding by scheme at figureBarely, can be considered in neutralstratus is reached the material flowing stress,cThe



Figure 4.2: mechanical scheme of processing

radial stresses by pressing notproduce resistant moment in bending process.This requests the work-piece material atradial direction compression in bending zonewith maximum 10% of material flowingstress cvalue.Because the sheet metal bending on machineswith rollers is making with relative radiusr/smuch more than 5 value, it can consider thattransversal section, while the broad workpiecesis take place with a very little breadthdeformation, because the great work pieceresistance deformation opposed the neutral stratus coincides with the medialstratus If it is approximated the real coldhardening characteristic of material atrequirement in tangential direction with alinear curve, correspondently figure the realtan- gential stress can be determinate byrelation Or, if we consider the geometry of bending If the bended

Figure 4.3: Plastic bending stress distribution system

work-piece has the sectionb x s and is bending on median stratus with mradius, the inner forces moment M,according in figure 3, can be definite byrelation

In relation (7), the double of first integralrepresent the transversal section staticallymoment S, and the double of second integralis the transversal section inertial moment . Thus, relation can be written



If it is multiplied and divided with thebended work-piece section resistancemodulus W, is obtained

If it take account thatS/Wfrom relationis a section characteristic and is noted K1, and is a physics and material characteristic and is noted K2, the relation (9) become The coefficient K1, because depend onlyby geometrical transversal section form canbe named the profile coefficient.The coefficient K2 express coldhardening intensity of plastic banded material,can be named strengthening coefficient.

4.2 Stresses in tangential direction and inner moment bending calculus

A plan work-piece bended on a rollerproperly figure, start from section wherethe curvier radius of median stratus is null,and is finalized in section , where themedial stratus curvier radius is - .To calculate the torque Mt what to be applied on roller, it is considered a size Ls

Figure 4.4: Bending scheme on bending roll

Taking account figure 5, the mechanical workof inner forces Li, for plastic bending of the work-piece size Lscan be determined byrelation The inner moment value creates theCurvier a current section betweensection can be calculate witrelation , what become: Replacing the My relation in relation andmaking calculus, it is obtained:



Figure 4.5: .- Bending moments at the plastic bending with cold-hardening.

Taking account by the moment make at thebending on roller, relation (13) can be written thus:

Taking account by the moment make at thebending on roller, relation (13) can be writtenthus:

where Mt is defined by relation (21) in Nm;Mf friction moment necessary for defeatingrolling friction resistance between rollers and work-piece and rollers bearings in Nm; tangentialperipheral speed of rollers, in transmission efficiency from electricmotor to rollers.



Figure 4.6: Scheme of positioning rollers with three and four symmetrical rollers.


Chapter 5 A Design process

Chapter 5

A Design process

Figure 5.1: A DESIGN PROCESS

5.0.1 Introduction

The notion of useful work is basic to machines functioning, as there is always some energy transfer involved . The mention of forces and motion is critical to our concern as in converting energy from one form to another , machine creates motion and develop forces . it is engineers task to define and calculate those motion , forces and changes in the energy in order to determine the size shape and material needed for each of the interrelated parts of the machine.

The goal in machine design is to size and shape the parts(machine elements) and choose the appropriate material for manufacturing process so that machine is expected to perform its intended function without failure .In this design project there is negligible acceleration so static force analysis will be



suffice . Static force analysis deals with structure which are to be designed against failure to external loading. The process of design is essentially an exercise in applied creativity. Various design process have been defined to help organize to attack upon un-constructed problem definition is vague for which many solution exist .some of this design process as shown below consist of 10 steps but can be extended to 25 steps.

• Identification of need

• Background research

• Goal statement

• Task specification

• Synthesis •

Analysis • Selection

• Detailed design

• Prototyping and testing

• Production

The initial step is Identification of need, usually consist of an ill defined and vague problem statement. The development of the Back ground Research is necessary to fully define and understand the problem after which it is possible to re state the goal in a more reasonable and realistic way than the original problem statement. Step (4) calls for the creation of detailed set of task specification which bound the problem and limit the scope .The synthesis step (5) is the one in which as many alternative possible design approaches are sought , usually without regards of quality and value .We can also state this step as ideation and invention step in which largest number of creative solution are generated.

In step (6) the solution of the previous steps are analyzed and they are accepted , rejected and modified . the most promising solution is selected at step 7 once the acceptable design are filtered and once the way is finalised then the Detailed design is done where all the loose ends are tied up complete engineering drawing is made , vendors are identified and manufacturing specification is defined . The actual construction of the working design is first done as a proto type in step (9)anfinally in quantity in production at step (10)

5.0.2 Concept of Iteration

The above description may give an erroneous impression that this process can be accomplished in a linear fashion as listed .on the contrary iteration is required within the entire process moving from any step back to any previous step in all possible combination and doing this repeatedly . The best ideas are generated at the step (5) will invariably be discovered to be flawed when later analyzed. Thus the step of the ideation will be necessary in order to generate more solution thus the return to the background phase may be necessary to gather information . the task specification may be may need to be refined if it turn out to be unrealistic.



5.0.3 Definition Stage

The first definition of the project in clear and concise manner is sheet metal rolling machine that means bending long rectangular plates into cylinders. Machine should be semi-automatic which means load is applied manually and driven by electrical power unit. Bending of the sheet should be based on the three roller bending concept.

5.0.4 Assumptions

• Plate is always having line contact with the roller which is parallel to roller axis during the process.

• The forces acting during the bending are larger than the self weight of the plate. So theself weight of the plate is neglected.

• The shift of the neutral plane is zero, i.e., it is considered to be at the center line of the plate

thickness.

• Frictional force at the bottom roller and the plate interface is always tangent to the roller surface.

• Rollers are assumed to be rigid. Roller material and plate material is assumed to have stable microstructure throughout the deformation process.

• Deformation occurs under isothermal conditions and E, i.e., Modulus of Elasticity Remains con-

stant during the process.

• Plane section remains plane, before and after the bending. Blank thickness (t) remains constant

during and after the bending.

• Baushinger effect is neglected. Blank is having uniform/constant radius of curvature for the sup-

ported length of the blank between two bottom rollers.

• Further simplifying assumptions are discussed as and when required during the Formulation.

5.0.5 Preliminary stage

• This stage we will define the experimental setup and the design outline that we have to go with. The reasons and justification for these decisions are documented.

• The design sketches so submitted will clearly explain the intentions of a designer and will be

understandable to another engineer or even to one self after the time has passed.

• It is an observed and experienced fact that the 90

• The purpose of the PDR is to insure that the project is on schedule for going into the detailed design phase. Having others from outside your group look over your project will hopefully result in an improved product. The design review is informal, but sloppiness in presentations will not be viewed favourably.

• In this stage we have studied various products in the market and then defined our criteria of going

further with the design so intended for the purpose

• This machine is available in more than 20 different sizes that cover a pre-bending range of wall

thicknesses of up to 320 mm. Standard sizes can be built with roll lengths of up to 4 500 mm. Special designs with roll lengths of up to 8 000 mm are feasible.



5.0.6 Manually operated pipe bending machine

Bending machines are fabricated from 30mm square section tubing to provide a rock solid frame which moreThan stands up to the rigors of daily use. The frame is designed to give maximum stability, minimizing the risks of sideways movement or skidding across floors, making operation as easy and effective as possible. The formers, which are key to creating a perfect bend, are machined cast aluminum. This means they can provideA superior and highly accurate bend as the machined area provides a perfect profile to support the pipe and gives Excellent contact and virtually no movement. By comparison, most other brands use non machined die casts.



Figure 5.2: Manually operated pipe bending machine


Chapter 6 Lead screw

Chapter 6

Lead screw

6.1 Introduction

The nuts and bolts might seem to be one of its least interesting but the fact is one of the most fascinating. The success and failure of design can hinge on a proper selection and use of its literally thousands of different designs of fasteners are offered by vendors we will investigate the application of screw as a fastener can be arranged to take tensile load, shear load or both which can have significant bending to load carrying abilities.

Figure 6.1: ACME Thread profile

6.2 Design for Lead Screw

Selection of the material for screw and nut Screw Plane carbon steel Nut At Caste Iron

6.3 Assumption

• Type of thread i] Square thread

• Dimensions do = 55



• 2 TPI let us select fine thread as they are more resistant to vibration and this is due to the fact that the helix angle in this case is small than the course thread from P.S.G. pg. no. 5.69 we get for do = 55 mm we get minor

• dia as 52 So,

• Pitch circle dia = = 53.

• Determination of the pitch P We know that the thread is configured with 2 TPI So Pitch = 9

• Now for square thread hl = 0.5 P a = 0.25 r = 0.12 H = hi + a = 1.25

6.4 POWER SCREW FORCE AND TORQUE ANALYSIS

The nut is turned and the torque is applied so as to turn it and the screw translates up to lift the load p up or down to lower it. There need to be some friction at the load surface to prevent the screw from turning with the nut. Once the load is engaged then it is not a problem.

6.5 INSIGHT OF THREAD

Screw thread is essentially an inclined plane that has been wrapped around a cylinder to create a helix if we un word the helix of one revolution of the helix it would look like a below shown fig.

The above fig. shows the free body diagram of the same nut as it slides up and down. Here we can see the friction force, that will always oppose motion.

6.5.1 DETERMINATION OF THE FORCES WHICH ARE ACTING

Where is the coefficient of friction between screw and nut. Now solving the above equation we get the below shown expression.

Now, The screw torque Ts required to lift the load is

we can also express the above equation in the form of lead L rather than the screw torque is not only the sole contribution to the torque, but the thrust collar also contribute a friction torque.

But in our case we do not have the thrust bearing so it want play any role in the calculation of torque.

6.6 STRESS IN THREAD

When the nut engages the thread, theoretically all the thread in engagement should share the load. In actuality, inaccuracies in the thread spacing, cause virtually all the load to be taken by the first pair of threads. Thus the conservative approach in calculating the thread stress is to assume the worst case of one thread pair is taking entire load equally or the other extreme case is to assume that all the engaged threads share the load equally. Now both the assumption can be used to calculate the stress in thread.



The true stress will be between these values. Most likely to come closer to one thread value.

6.6.1 Axial Stress

A power screw can see the axial loads ton either tension or compression. In our case it will be compression and so Buckling analysis in done for the same.

6.6.2 Shear stress

One possible failure mode involves stripping of the thread either out of the nut or off the screw, which, it either of these scenarios occur is dependent on relative strength of the nut and the screw material. If the nut material is weaker then it may, strip from the major diameter. If the screw is weaker then it may strip the thread along with minor diameter and if the strength of both are same then it may strip on the



pitch circle diameter.

In any event we must assume degree of load sharing among the threads in order to calculate the stress. One approach is to consider that since complete failure requires the thread to strip all can be considered to share the load equally. This is probably a good assumption as long as nut or the screw is ductile to allow each thread to yield as the same assembly begins to fail. However if both the parts are brittle as in our case and the thread is poor one can envision each thread taking the entire load until it factures and passes the job to the another thread.

Again the reality is between both the ends. If we could express the shear area in terms of number of thread then we could define the degree of load sharing. Striping area at minor diameter d1 = minor dia w1 = Factor defining % of pitch occupied by metal at minor diameter. P = pitch striping area at major diameter

6.6.3 TORSIONAL STRESS

The torque that twist the screw is dependent on the screw nut interface, if the screw and nut are well lubricated, less of applied torque is transmitted to the screw. If the nut is rusted the screw all applied torque will twist the screw. To accommodate the worst case of high thread friction, use the total applied



torque in the equation for the torsional stress in round section.

6.7 MANUFACTURING FASTENERS

Thread cutting several techniques are available for making threads. Internal thread are usually cut with the special tool called a tap that has desired thread form and looks like a screw. A tap is made up of hard end tool steel and has axial grooves that interrupt its thread provided the cutting edge in the shape of threads. A pilot hole is drilled with a proper size tap drilled and the lubricated tap is turned slowly into the hole while being advanced at the suitable rate. Nuts too large to tap are threaded in lathe, with thread shaped single-point cutting tool that has advanced axially through the hole by a lead screw to control its lead and pitch. External thread can also be cut with a single point tool in a lathe or alternative with a die, which is external thread equivalent to tap the rod to be threaded s the same size as to be the outside diameter of the thread. Specialized machines called screw machines are used to produce lead screws.

6.7.1 THREAD ROLLING

Another superior method for making external thread by thread rolling also called thread forming. Hard- ened steel dies in the form of threads are forced into the surface of the rod being threaded. The dies cold flow the material into thread shape. The final outside diameter of the thread is larger than the initial diameter of the rod, because the material is forced out into the roots and into the rest of the thread.

6.7.2 ADVANTAGE OF ROLLING V/S CUTTING

• The cold forming work-hardens and strengthens the material.

• The crest radii at the roots and the crest and introduces favourable compressive residual stresses at

threads.

• The disruption of the material shape into the thread form causes a re-orientation of materials grain.

• In contrast thread cutting interrupts the grain.

• All the above stated factors contribute to significant increase in strength.

• Rolled thread compare to cut threads have less waste than the cut threads as no material is removed

and the blank is consequently smaller in volume.

Thread rolling should be done after hardening the bolt, IF POSSIBLE, as thermal hardening process will relieve the desirable stress introduced by rolling.

6.7.3 HEAD FORMING

The heads of the bolts and screws are typically 899 cold formed in upsetting process.

The shank of the bolt to be gripped tightly in the cold heading machine with appropriate length stick- ing out. A die of desired head diameter surrounds this exposed end when the hammer comes down, it cold flows the material into the round head. IF POSSIBLE Heat & Treatment should be done.



6.7.4 STRENGTH OF STANDARD BOLTS

For our application we have selected entire range of bolts based on proof strength sp as defined by ISO specification. Proof strength can be defined as the stress at which bolt begins to take permanent set.


Chapter 7 GEAR

Chapter 7

GEAR

7.1 INTRODUCTION:

Gears are used to transmit torque and angular velocity in a wide variety of applications. There is also a wide variety of gear types to choose from. The simplest type of gear, the spur gear, designed to operate on parallel shaft and having teeth parallel to the shaft axis. Other gear types such as helical, bevel, and worm can accommodate nonparallel shafts.

Gears have a long history. The ancient Chinese South-Pointing Chariot, supposedly used to navigate across the Gobi desert in pre-Biblical times, contained gears. Leonardol Da Vinci shows many gear arrangements in his drawings. Early gears were most likely made crudely of wood and other easily worked materials, their teeth merely being pegs inserted in a disk or wheel. It was not until the industrial revolution that machines demanded and manufacturing techniques allowed, the creation of gears as we now know them with specially shaped teeth formed or cut into a metal disk.

7.2 GEAR NOMENCLATURE

the

shows two teeth of a gear with the standard nomenclature defined. The tooth height is defined by the


Chapter 7 GEAR

addendum (added on) and the dedendum (subtracted from), which are referenced to the nominal pitch circle. The dedendum is slightly larger than the addendum to provide a small amount of clearance between the tip of one mating tooth (addendum circle) and the bottom of the tooth space of the other (dedendum circle). The tooth thickness is measured at the pitch circle. and the tooth space width is slightly larger than the tooth thickness. The difference between these two dimensions is the backlash. The face width of the tooth is measured along the axis of the gear. The circular pitch is the arc length along the pitch circle circumference measured from a point on one tooth to the same point on the next. The circular pitch defines the tooth size. The definition of circular pitch Pc.

7.3 GEAR TOOTH THEORY

The simplest means of transferring rotary motion from one shaft to another is a pair of rolling cylinders. They may be an external set of rolling cylinders, as shown in or an internal set. If sufficient friction is available at the rolling interface, this mechanism will work quite well. There will be no slip between the cylinders until the maximum available frictional force at the joint is exceeded by the demands of torque transfer.

The principal drawbacks to the rolling-cylinder drive mechanism are its relatively low torque capa- bility and the possibility of slip. Some drives require absolute phasing of the input and output shafts for timing purposes. This requires adding some meshing teeth to the rolling cylinders. They then become gears.

7.4 FUNDAMENTAL LAW OF GEARING

the Conceptually, teeth of any shape will prevent gross slip. Old water-powered mills and windmills used wooden gears whose teeth were merely round wooden pegs stuck into the rims of the cylinders. Even ignoring the crudity of construction of these early examples of gearsets, there was no possibility of smooth velocity transmission because the geometry of the tooth pegs violated the fundamental law of


Chapter 7 GEAR

gearing, which states that the angular velocity ratio between the gears of a gearset must remain constant throughout the mesh. The angular velocity ratio mv is equal to the ratio of the pitch radius of the input gear to that of the out gear.

7.5 The Involute Tooth Form

From the involute as shown in fig. The involute of a circle is a curve that can be generated by unwrap- ping a taut string from a cylinder, as shown in Figure.

Note the following about this involute curve.

• The string is always tangent to the base circle.

• The center of curvature of the involute is always at the point of tangency of the string with the base

circle.


Chapter 7 GEAR

• A tangent to the involute is always normal to the string, which is the instantaneous radius of curvature of the involute curve.

Figure shows two involutes on separate cylinders in contact or in mesh. These represent gear teeth. The cylinders from which the strings are unwrapped are called the base circles of the respective gears. Note that the base circles are necessarily smaller than the pitch circles, which are at the radii of the original rolling cylinders, rp and rg. The gear tooth must project both below and above the rolling-cylinders surface (pitch circle), and the involute only exists outside of the base circle. The amount of tooth that sticks out above the pitch circle is the addendum, shown as ap and ag for pinion and gear, respectively. These are equal for standard, full-depth gear teeth.

There is a common tangent to both involute tooth curves at the contact point, and a common normal, perpendicular to the common tangent. Note that the common normal is, in fact, the strings of both involutes, which are collinear. Thus the common normal, which is also the line of action, always passes through the pitch point regardless of where in the mesh the two tooth are contacting. The pitch point has the same linear velocity in both pinion and gear, called the pitch-line velocity. The angle between the line of action and the velocity vector is the pressure angle .

7.6 Mesh Geometry

The points of beginning and leaving contact define the mesh of the pinion and gear. The distance along the line of action between these points within the mesh is called the length of action Z, defined by the intersections of the respective addendum circles with the line of action, as shown in Figure. The distance along the pitch circle within the mesh is the arc of action, and the angles subtended by these points and the line of centers are the angle of approach and angle of recess. The arc of action on both pinion and gear pitch circles must be the same length for zero slip between the theoretical rolling cylinders.


Chapter 7 GEAR

7.7 Changing Center Distance

When involute teeth (or any teeth) have been cut into a cylinder with respect to a particular base circle to create a single gear, we do not yet have a pitch circle. The pitch circle comes into being only when we mate this gear with another to create a pair of gears, or gearset. There will be some range of center-to- center distances over which we can achieve a mesh between the gears. There will also be an ideal center distance that will give us the nominal pitch diameters for which the gears were designed. However, the limitations of the manufacturing process give a low probability that we will be able to exactly achieve this ideal center distance in every case. More likely, there will be able to exactly achieve this ideal center distance in every case. More likely, there will be some error in the center distance, even if small.

If the gear tooth form is not an involute, then an error in center distance will cause ripple, in the output velocity. The output angular velocity will then not be constant for a constant input velocity, violating the fundamental law of gearing. However, with an involute tooth form, center-distance errors do not affect the velocity ratio. This is the principal advantage of the involute over all other possible tooth forms and is the reason why it is nearly universally used for gear teeth. Figure shows what happens when the center distance is varied on an involute gearset. Note that the common normal still goes through the pitch point, and also through all contact points within the mesh. Only the pressure angle is affected by the change in center distance.

7.8 DESIGN

Since we have reverse gear meshing so we use helical gear as they are quite and dont make noise as parallel Helical gears mesh with the combination of rolling and sliding with the contact starting at the one end and whipping at the another across its face width.

• Power to be transmitted Pm = 10 Hp

• Input speed to the pinion = 15 rpm

• Output speed desired = 4 rps

• Assume helix angle B1 = B2 = 170

• Pressure angle = 200 for involute profile

• Velocity ratio = i = 3.5

7.8.1 Assumptions:

Let us take tooth profile as n = 200 full depth Gear Quality we have selected prevision cut gears to control dynamic load and wear Type of gear standard Sn gear has been selected Helix angle For1 Pinion Right Hand Helix B1 = 170 For Gear Left Hand Helix B2 = 170


Chapter 7 GEAR

Number of teeth on pinion (Z1) and gear (Z2)

7.8.2 Virtual Number of teeth

We can then define a virtual number of teeth Ne as the quotient of the circumference of a virtual pitch circle of radius re and the normal pitch Pc. This defines a virtual gear that is equivalent to a spur gear with N teeth thus giving a stronger tooth in both bending and surface fatigue than a spur gear with the same physical number of teeth as the helical gear. The larger number of virtual teeth also reduces under- cutting in small pinions, allowing a lower minimum number of teeth for helical gears than for spur gears.

7.9 Lubrication in gear

to avoid premature failure from one of the surface-failure. Such as adhesive or abrasive wear. Controlling temperature at the mesh interface is important in reducing scuffing and scoring of the teeth. Lubricants remove heat as well as separate the metal surfaces to reduce friction and wear. Sufficient lubricant must be provided to transfer the heat of friction to the environment without allowing excessive local temperatures in the mesh.

The usual and preferred approach is to provide an oil bath by housing the gears in an oil-tight box, called a gearbox. Gear rotation will carry the lubricant to the meshes and keep the unsubmerged gears oiled. The oil must be kept clean and free of contaminants and should be changed periodically. A much less desirable arrangement, sometimes used for situations in which a gearbox is not practical, is to periodically apply grease lubricant to the gears when they are stopped for servicing. Grease is merely petroleum oil suspended in a soap emulsion. This topical, grease lubrication does little for heat removal and is recommended only for low-velocity, lightly loaded gears.

Light oils (10-30W) are sometimes used for gears with velocities high enough and/or loads low enough to promote elastohydrodynamic lubrication (see components, extreme pressure (EP) lubricants are often used. These are typically 80-90W gear oils with fatty-acid type additives that provide some protection against scuffing under boundary-lubricated conditions.

7.10 Manufacturing of gears

Several methods are used to manufacture gears. They can be divided into two categories, forming and machining. Machining further divides into roughing and finishing operations. Forming refers to the direct casting, molding, drawing or extrusion of tooth forms in molten, powered, or heat-softened materials. Roughing and finishing are material removal techniques used to cut or grind the tooth shape into a solid blank at room temperature. Roughing methods are often used alone without any subsequent finishing operation for nonprecision gears. Despite their name, the roughing processes actually create a smooth and accurate gear tooth.

7.10.1 Forming Gear Teeth

In all tooth-forming operations, the teeth on the gear are formed all at once from a mold or die into which the tooth shapes have been machined. The accuracy of the teeth is entirely dependent on the quality of the die or mold and in general is much less than can be obtained from roughing or finishing methods.


Chapter 7 GEAR

7.10.2 Casting

Teeth can be sand cast or die cast in various metals. The advantage is low cost, as the tooth shape is built into the mold. No finishing operations on the teeth are typically done after casting, though they could be.

7.10.3 Machining

The bulk of metal gears used to transmit power in machinery are made by a machining process from cast, forged, or hot-rolled blanks. Roughing processes include milling the tooth shape with formed cutters or generating the shape with a rack cutter, a shaper cutter, or a hob. Finishing processes include shaving, burnishing, lapping, honing, or grinding. Each of these methods will be briefly described.

7.10.4 Roughing Processes

Gear Shaping Gear Shaping uses a cutting tool in the shape of a gear which is reciprocated axially across the gear blank to cut the teeth while the blank rotates around the shaper tool as. It is a true shape generation process in that the gear-shaped tool cuts itself into mesh with the gear blank. The accuracy is good, but any errors in even one tooth of the shaper cutter will be directly transferred to the gear. Internal gears can be cut with this method as well.

7.10.5 Finishing Processes

Lapping and Honing Lapping and Honing both employ an abrasive-impregnated gear or gear-shaped tool that is run against the gear to abrade the surface. In both cases, the abrasive tool drives the gear in what amounts to an accelerated and controlled run-in to improve surface finish and accuracy.


Chapter 8 Bearing

Chapter 8

Bearing

We use the term bearing here in its most general sense. Whenever two parts have relative motion, they constitute a bearing by definition, regardless of their shape or configuration. Usually, lubrication is needed in any bearing to reduce friction and remove heat. Bearings may roll or slide or do both simultaneously.

A plain bearing is formed by any two materials rubbing on one another, whether a sleeve around a shaft or a flat surface under a slider. In a plain bearing, one of the moving parts usually will be steel or cast iron or some other structural material in order to achieve the required strength and hardness. Transmission shafts, links, and pins are in this category. The parts that move against will usually be made of a bearing material such as bronze, Babbitt, or a nonmetallic polymer. A radial plain bearing may be split axially to assemble it to the shaft, or may be complete circle called a bushing. A thrust bearing supports axial loads.

Alternatively, a rolling-element bearing, which has hardened steel balls or rollers captured between hardened steel raceways, may be used to provide very low friction. Plain bearings are typically custom designed for the application, while rolling-element bearings are typically selected from manufacturers catalogs to suit the loads, speeds, and desired life of the particular application.

8.1 Material Combination

Some combinations of materials that have proven either successful or unsuccessful in engineering applications of bearings and sliders.

Some properties sought in a bearing material are relative softness (to absorb foreign particles), reasonable strength, machinability (to maintain tolerances), lubricity, temperature and corrosion resistance, and, in some cases, porosity (to absorb lubricant). A bearing material should be less than one-third as hard as the material running against it in order to provide embedability of abrasive particles. In addition, the compatibility on adhesive wear are of concern and these also depend on the mating material. Several different classes of materials can be useful as bearings, typically those based on lead, tin, or copper. Aluminium, alone, is not a good bearing material, although it is used as an alloying element in some bearing materials.

Gray Cast Iron and Steel are reasonable bearing materials when run against each other at low velocities. The free graphite in the cast iron adds lubricity but liquid lubricant is needed as well. Steel can also be run against steel if both parts are hardened and lubricated. This is a common choice in rolling-contact as in rolling-element bearings. In fact, hardened steel will run against almost any material with proper lubrication. Hardness seems to protect against adhesion in general.


Chapter 8 Bearing

Figure 8.1: Material comination

8.2 Thrust Bearing

Ball and roller bearings are also made for pure thrust loads as shown in Figure. Cylindrical-roller- thrust bearings have higher friction than ball-thrust bearings due to the sliding occurs between roller and raceways (because only one point on the roller can match the varying linear velocity over the raceways radii) and should not be used in high-speed applications.

Figure 8.2: Thrust bearing

8.3 Bearing Mounting

Rolling bearings are made with close tolerances on their inside and outside diameters to allow press- fitting on the shaft or in the housing. The bearing races (rings) should be tightly coupled to the shaft and housing to guarantee that motion only occurs inside the low-friction bearing. Press-fitting both rings can make for a difficult assembly or disassembly in some cases. Various clamping arrangements are commonly used to capture either the inner or outer ring without a press fit, the other being secured by pressing. The inner ring is usually located against a shoulder on the shaft. Bearing catalog tables provide recommended shaft shoulder diameters, which should be observed to avoid interference with seals or shields. Maximum allowable fillet radii to clear the rings corners are also defined by the manufacturers.


Chapter 8 Bearing

Figure shows a nut and lock-washer arrangements used to clamp the inner ring to the shaft to avoid a press fit. Bearing manufacturers supply special nuts and washers standardized to fit their bearings. Figure (b) shows a snap ring used to axially located the inner ring, which would be pressed to the shaft. Figure (c) shows the outer ring clamped axially to the housing and the inner ring located by a sleeve spacer between the inner ring and an external accessory flange on the same shaft.

Figure 8.3: Bearing mounting


Chapter 9 Rollers and Idlers

Chapter 9

Rollers and Idlers

The term shaft usually refer to rotating machine element, circular in cross section, which supports transmission element like gear, pulley and sprocket and transmit power. The shaft is always stepped with maximum diameter in the middle portion and minimum dia at two ends. Shafts are given specific names in typical application although all application involve transmission of power motion and torque. Ordi- nary transmission shafts are made up of medium carbon steel with the carbon content from 0.15 to 6.40 such as 3068 and 4068 these steels are commonly called machinery steel for the purpose where greater strength is required high carbon steel 45 c8 and 50 c8 alloy steels are also provided for the same purpose 16 Mn 5cr4. Alloy steels are costly compared to plane carbon steel but serves the purpose when it comes to strength, hardness and toughness, they also serve high resistance so corrosion as compare to plane carbon steel so the increase in the price of the same is justified.

9.1 Shaft loads

The loading on rotating transmission shafts is principally one of two types : torsion due to the transmitted torque or bending from transverse loads at gears, sheaves, and sprockets. These loads often occur in combination, since, for example, the transmitted torque may be associated with forces at the teeth of gears or sprockets attached to the shafts. The character of both the torque and bending loads may be either steady (constant) or may vary with time. Steady and time-varying torque and bending loads can also occur in any combination on the same shaft.

If the shaft is stationary (nonrotating) and the sheaves or gears rotate with respect to it (on bearings), then it becomes a statically loaded member as long as the applied loads are steady with time. However, such a nonrotating shaft is not a transmission shaft, since it is not transmitting any torque. It is merely an axle, or round beam, and can be designed as such. This chapter is concerned with rotating, transmission shafts and their design for fatigue loading.

Note that a rotating shaft subjected to a steady, transverse-bending load will experience a fully re- versed stress state as shown in Figure 9-1a. Any one stress element on even for steady bending loads, a rotating shaft must be designed against fatigue failure. If either or both the torque and transverse loads vary with time, the fatigue loading becomes more complex, but the fatigue-design principles remain the same, Chapter 6.

9.2 Attachments and Stress concentrations

While it is sometimes possible to design useful transmission shafts that have no changes in section diameter over their length, it is most common for shafts to have a number of steps or shoulders where the diameter changes to accommodate attached elements such as bearings, sprockets, gears, etc., as shown



in Figure, which also shows a collection of features commonly used to attach or locate elements on a shaft. Steps or shoulders are necessary to provide accurate and consistent axial location of the attached elements as well as to create the proper diameter to fit standard parts such as bearings.

Keys, are often used to secure attached elements to the shaft in order to transmit the required torque or to capture the part axially. Keys require a groove in both shaft and part and may need a setscrew to prevent axial motion. Snap rings groove the shaft, and cross-pins create a hole through the shaft. Each of these changes in contour will contribute some stress concentration and this must be accounted for in the fatigue-stress calculations for the shaft.

9.2.1 Designing to Avoid Stress Concentrations

The designer is always faced with the problem of stress concentrations at sections having abrupt changes of shape. The best that can be done is to minimize their effects. In general, the sharper the corner and the larger in magnitude the change in contour, the worse will be the stress concentration. For the stepped bar in Figure, larger D/d ratios and smaller r/d ratios give worse stress concentration. From these obser- vations, we can state some general guidelines for designing to minimize stress concentrations. 1. Avoid abrupt and/or large-magnitude changes in cross section if possible. 2. Avoid sharp corners completely and provide the largest possible transition radii between surfaces of different contours.

Figure 9.1: Roller and Idler

9.3 Force Flow analogy

Figure shows a shaft with an abrupt step and a sharp corner, while Figure 4-37b shows the same step in a shaft with a large transition radius. A useful way to visualize the difference in the stress states in contoured parts such as these is to use a force-flow analogy, which considers the forces (and thus the stresses) to flow around contours in a way similar to the flow of an ideal incompressible fluid a pipe or duct of changing contour. A sudden narrowing of the pipe or duct causes an increase in fluid velocity at the neck-down to maintain constant flow. The velocity profile is then concentrated into a smaller region. Streamlined shapes are used in pipes and ducts to reduce turbulence and resistance to flow. Streamlining our part contours can have similar beneficial effects in reducing stress concentrations. The force-flow contours at the abrupt step-transition in Figurea are more concentrated than in the design of Figure.

A similar approach of removing material to improve the force flow is seen in Figure 4-39a, which shows a snap-ring groove in a shaft with additional relief grooves provided on each side to smooth the effective transition of the cross-sectional dimension. The effect on the force flow lines is similar to



that shown in Figure 4-38c. Another common source of stress concentration is a key needed to torque- couple gears, pulleys, fly-wheels, etc. to a shaft. The keyway groove creates sharp corners at location of maximum bending and torsional stresses. Different key styles are available, the most common being the square key and the circular-segment. Woodruff key as shown in Figures 4-38b and 4-38c.

Another example of removing material to reduce stress concentration (not shown) is the reduction of the unthreaded portion of a bolt shanks diameter to a dimension less than that of the root diameter of the thread. Since the thread contours create large stress concentrations, the strategy is to keep the force-flow lines within the solid (unthreaded) portion of the bolt.

Figure 9.2: Force flow

9.4 Design considerations

Some general rules of thumb for shaft design can be stated as follows : 1. To minimize both deflections and stresses, the shaft length should be kept as short as possible and overhangs minimized. 2. A cantilever beam will have a larger deflection than a simply supported (straddle mounted) one for the same length, load and cross section, so straddle mounting should be used unless a cantilever shaft is dictated by design constraints. 3. A hollow shaft has a better stiffness/mass ratio (specific stiffness) and higher natural frequencies than a comparably stiff or strong solid shaft, but will be more expensive and larger in diameter. 4. Try to locate stress-raisers away from regions of large bending moment if possible, and minimize their effects with generous radii and reliefs. 5. If minimizing deflection is the primary concern, then low-carbon steel may be the preferred material, since its stiffness is as high as that of more expensive steels and a shaft designed for low deflection will tend to have low stresses.



6. Deflections at gears carried on the shaft should not exceed about 0.005 in and the relative slope between the gear axes should be less than about 0.03O 7. If plain (sleeve) bearings are used, the shaft deflection across the bearing lenth should be less than the oil-film thickness in the bearing 8. If non-self-aligning rolling element bearings are used, the shafts slope at the bearings should be kept to less than about 0.04 9. If axial thrust loads are present, they should be taken to ground through a single thrust bearing per load direction. Do not split axial loads between thrust bearings, as thermal expansion of the shaft can overload the bearings. 10. The first natural frequency of the shaft should be at least three times the highest forcing frequency expected in service, and preferably much more. (A factor of 10x or more is preferred, but this is often difficult to achieve in mechanical systems.

Figure 9.3: Method to remove stress concentration


Chapter 10 Coupling

Chapter 10

Coupling

10.1 Introduction

A coupling can be defined as a mechanical device that permanently joins two rotating shafts to each other. The most common application of coupling is joining of shafts of two separately built or purchased units so that a new machine can be formed. There is a basic difference between a coupling and a clutch can connect or disconnect two shafts at the will of the operator.

A wide variety of commercial shaft couplings are available, ranging from simple keyed, rigid couplings to elaborate designs that utilize gears, elastomers, or fluids to transmit the torque from one shaft to another or to other devices in the presence of various types of misalignment. Couplings can be roughly divided into two categories, rigid and complaint. Compliant in this context means that the coupling can absorb some misalignment between the two shafts and rigid implies that no misalignment is allowed between the connected shafts.

10.2 Rigid flange coupling

The rigid flange couplings have the following advantages: i) Rigid coupling has high torque transmitting capacity. ii) Rigid coupling is easy to assemble and dismantle. iii) Ridig coupling has simple construction. It is easy to design and manufacture.

The rigid flange couplings have the following disadvantages : i) It is a rigid type of coupling. It cannot tolerate misalignment between the axes of two shafts. ii) It can be used only where the motion is free from shocks and vibrations. iii) It requires more radial space.


Chapter 10 Coupling

Figure 10.1: Rigid protected typeflange section


Chapter 10 Coupling


Chapter 11 Gear reduction box

Chapter 11

Gear reduction box

First off, let me explain that gear reduction in the context of this help section refers to speed reduction in general whether it be by traditional gear, chain and sprocket, or belts. The goal of this section is to give anyone a basic understanding of what gear reduction is and how it can be used to help give an idea on how to implement it in a robot. Because there are different areas in a robot that could benefit from gear reduction we will focus on the most important one, the drive train. And, we will talk only about AC electric motors but the fundamental can be applied to other motors as well.

The reason that we need to know about gear reduction is because the output speed of a motor is usually too fast for normal use. Most DC motors at normal operating voltages spin at well over 1,000 rpm (revolutions per minute) and some even as high at 50,000 rpm for brushless DC motors. If we had a motor than spun at say, 3,000 rpm, and we attached a 6 inch wheel to it then the wheel would theoretically be able to move the bot at almost 54 miles per hour! That is way too fast to control in an arena due to other considerations that wouldn't happen but we'll get into that later. So we need to reduce the rate at which the wheel spins so that we get a robot that we can at least control. Hint, the quick way of determining the speed of a wheel is to multiply the diameter (in inches) of the wheel by the rpm and divide the result by 336.

Quite simply, gear reduction involves using gears/sprockets/pulleys of two different sizes to work together. Because they are of differing sizes they will have different circumferences (distance around the outer edge) and we can use this to our advantage. Let's take a look at what this circumference thing really means. To the left is a representation of a 4 inch diameter wheel.

Well, how do we determine the final reduction of a multistaged gearbox? It's really pretty easy. Mul- tiply the reduction of the first set of gear times the reduction of the next set times the reduction of the next set and so on until you have included them all. That will give you the total gear reduction. So, if we had a three stage gearbox where the first gear set was reduced 4:1, the second set reduced 5:1, and the third set 6:1 then we would multiply 4 x 5 x 6 to get 120:1. Now, let's use the motor that we talked about at the beginning and put this gearbox on it and then attach a wheel to the output shaft. Input rpm is 3000. With a 120:1 reduction we divide 3000 by 120 to get 125 rpm. If we attach a 6 inch wheel to that then our bot would move at 2.32 miles per hour. That's a little slow for our taste so we'll have to come up with a gear box that gives us what we are looking for. So, let's determine what type of reduction we would need to achieve a target speed of 15 miles per hour for our bot. First, we know that we are using 6 inch wheels and our motor spins at 3000 rpm and are target speed is 15 mph and our constant is 336. Plug them into this formula ((wheel size) x (motor rpm))/((target speed) x 336). If we plug in our numbers we would get (6 x 3000)/(15 x 336) = 3.57:1. It would be pretty hard to get that exact reduction


Chapter 11 Gear reduction box

but we can get close using a 10 tooth input sprocket or gear and a 35 or 36 tooth output sprocket or gear. But, also remember that the 3000 rpm is for an unloaded motor. Loaded motors will spin at a slower speed but determining that speed is beyond the scope of this help section.

Well, the two main disadvantages are 1 you lose speed and 2 you have added weight for the gear box. But, on the other hand, there are some great advantages to using gear reduction. First, you bring the bot down to a manageable speed. Second, the motor doesn't have to work as hard to spin the wheel which means it won't draw as much current from your batteries. And third, along those lines, the torque produced by the output is inversely proportional to the amount of reduction in the gear box. Say what? Basically, if you have a 4:1 gear box then the bot moves 1/4 as fast but has 4 times the torque!

The optimum configuration will give you greatest speed but still have enough torque to cause the wheels to break traction (peel out) before the motor stalls. That optimum configuration varies from bot to bot and is up to you to figure out how to best implement it with your own robot.

Figure 11.1: Details of reduction box


Chapter 12 Power unit Assembly

Chapter 12

Power unit Assembly

Figure 12.1: Induction motor

An induction or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is induced by electromagnetic induction from the magnetic field of the stator winding. An induction motor therefore does not require mechanical commutation, separate-excitation or self-excitation for all or part of the energy transferred from stator to rotor, as in universal, DC and large synchronous motors. An induction motor's rotor can be either wound type or squirrel-cage type.

In both induction and synchronous motors, the AC power supplied to the motor's stator creates a magnetic field that rotates in time with the AC oscillations. Whereas a synchronous motor's rotor turns at the same rate as the stator field, an induction motor's rotor rotates at a slower speed than the stator field. The induction motor stator's magnetic field is therefore changing or rotating relative to the rotor. This induces an opposing current in the induction motor's rotor, in effect the motor's secondary winding, when the latter is short-circuited or closed through an external impedance. The rotating magnetic flux induces currents in the windings of the rotor in a manner similar to currents induced in a transformer's secondary winding(s). The currents in the rotor windings in turn create magnetic fields in the rotor that react against the stator field. Due to Lenz's Law, the direction of the magnetic field created will be such as to oppose the change in current through the rotor windings. The cause of induced current in the rotor windings is the rotating stator magnetic field, so to oppose the change in rotor-winding currents the rotor will start to rotate in the direction of the rotating stator magnetic field. The rotor accelerates until the magnitude of induced rotor current and torque balances the applied load. Since rotation at synchronous speed would result in no induced rotor current, an induction motor always operates slower than synchronous speed. The difference, or "slip," between actual and synchronous speed varies from about 0.5 to 5.0% for standard Design B torque curve induction motors.


Chapter 12 Power unit Assembly

Figure 12.2: Comparison table


Chapter 13 Modelling

Chapter 13

Modelling

13.1 Introduction

The modelling of 3-roller bar bending machine consists of many number of part components and requires proper connectivity between its neighbouring components. A minute error in the assembly causes the machine a major damage during it run. Hence this machine build-up high stress on its component (gear, shaft & roller) during bending and rolling of billet. The modelling of this machine must be carefully selected; the best suited modelling software for the above machine is Autodesk Inventor Professional 2013.It contains some special features like error correction, mating transitional, mating rotational, mating constrain set, mating transverse to rotational, backup detailing, parting, presenting etc. these features makes convenient and ease of modelling. The 3-D model drawing created from solid edge are shown below.


Chapter 14 Future scope of Project

Chapter 14

Future scope of Project


Chapter 14 Future scope of Project


Chapter 15 Test Cases, Project Time Line & Task Distribution

Chapter 15

Test Cases, Project Time Line & Task Distribution

15.1 Test Cases

15.1.1 Case 1: Design

15.1.2 Case 2: Procurement of parts

15.1.3 Case 3: Fabrication

15.1.4 Case 4:Load testing

15.2 Project Time Line

The following table shows the expected flow of work for the accomplishment of the required result.

Table 15.1: Project Time Line

No. Describtion Duration Complexity Status

1 Literature Survey of basics process 1 week 4 Done

2 Literature Survey of various methods available for 3 weeks 4 Done

rolling

3 Design of various assembelled part 1 weeks 4 Done 4

Procurement of parts 1 week 3 Done

5 Fabrication of machine 2 week 5 Not Done


References

References

1. Bend ability Analysis for Bending of C-Mn Steel Plates on Heavy Duty 3-Roller Bending Machine, International Journal of Aerospace and Mechanical Engineering 1:2 2007, presented by Himanshu V. Gajjar, Anish H. Gandhi, Tanvir A Jafri, and Harit K. Raval. 2. Modeling and computation of the three-roller bending process of steel sheets, Journal of Me- chanical Science and Technology 26 (1) (2012) 123 128, presented by Ahmed Ktari, ZiedAntar, Nader Haddar and KhaledElleuch. (Manuscript Received July 9, 2010; Revised December 13, 2010; Accepted September 18, 2011). 3. Mechanics-Based Determination of the Centre Roller Displacement in Three-Roll Bending for Smoothly Curved Rectangular Plates, KSME International Journal Volume 15. No.12, pp. 1655-1663, 2001. Presented by Jong Gye Shin, Jang Hyun Lee, HyunjuneYim and Iu Kim. 4. Analytical Model for Prediction of Force During 3-Roller Multi-pass Conical Bending And Its Experimental Verification, international journal of mechanical engineering and robotics research, ISSN 2278-0149S, VOL.1, NO.3, October 2012, presented by M K Chudasama1* and H K Ra val. 5. Analyses of Non-Kinematic Conical Roll Bending Process with Conical Rolls, proceedings of the ASME 2010 International Design Engineering Technical Conference(IDETC), August 15-18, presented by zhengkunfengandhenrichampliaud. 6. Boresi, A. P. and Schmidt, R. J. and Sidebottom, O. M., 1993, Advanced Mechanics of Materials, John Wiley and Sons, New York. 7. Libai, A. and Simmonds, J. G., 1998, The Nonlinear Theory Of Elastic Shells, Cambridge University Press. 8. Timoshenko, S. and Woinowsky-Krieger, S., 1959, Theory of Plates and Shells, McGraw-Hill. 9. Shigley J, "Mechanical Engineering Design", p44, International Edition, pub McGraw Hill, 1986, ISBN 0-07- 100292-8. 10. Gere, J. M. and Timoshenko, S.P., 1997, Mechanics of Materials, PWS Publishing Company. 11. Cook and Young, 1995, Advanced Mechanics of Materials, Macmillan Publishing Company: New York.


Project Hosting

Appendix A

Project Hosting

The project is hosted at Google Code. The complete source code along with the manual to operate the project and supplementary files are uploaded.

Project Link : https://code.google.com/p/proquiz

QR CODE:


pipe bending

Documents

bending machine

machine autodesk

machine interface

analysis of load

gear drive analyses

gear tooth

guidance of

rolling rollers