Machine Design Final Report

Project Report ME3052

Automated String Hopper Making Machine

By

Index No. Name

080456A K.Sanjeevan

080515F Ushan G.A.C

Department of Mechanical Engineering University of Moratuwa

Sri Lanka

01stApril 2012

Group No: 37

37

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Abstract

Goal of this project is propose the detail design and drawings of automated string hopper making machine for large food industry applications. String hopper making machine is a device that squeezing the string hopper with following categorized efficiency such as time, human effort, safety, cleaning and quality during string hopper making. In this design, it is mainly notified about cost of the machine as well as time efficiency. This designed machine can squeeze string hopper using screw extruder with electric power, and extruded out using rotating conveyer from machine die to away as near to operator. Therefore, production rate of the string hopper making machine is high compared with other manual and commercially available machines.

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Table of Contents

1 Background ........................................................................................................................................... 1

1.1 Introduction .................................................................................................................................. 1

1.2 Problem definition ........................................................................................................................ 1

2 Literature Review .................................................................................................................................. 2

2.1 Available machines and their disadvantages ................................................................................ 2

2.1.1 Disadvantages of machines ................................................................................................... 3

2.2 User needs analysis ....................................................................................................................... 3

2.3 Engineer’s perspective of the design ............................................................................................ 4

3 System design and methodology .......................................................................................................... 4

3.1 Methodology ................................................................................................................................. 4

3.2 Concept Generation ...................................................................................................................... 5

3.2.1 Methods of string hoper making .......................................................................................... 5

3.2.2 Functional Analysis ................................................................................................................ 5

1.1.1 Morphological chart .............................................................................................................. 6

3.2.3 Details chart of concept morphological ................................................................................ 7

3.3 Concept screening ......................................................................................................................... 8

3.4 Final selection ............................................................................................................................... 9

4 Summary of Calculations .................................................................................................................... 10

4.1 Power calculation ........................................................................................................................ 10

4.2 Barrel design ............................................................................................................................... 10

4.3 Motor selection ........................................................................................................................... 10

4.4 Coupling design ........................................................................................................................... 10

4.4.1 Design for key...................................................................................................................... 10

4.4.2 Design for flange ................................................................................................................. 10

4.4.3 Design for bolts ................................................................................................................... 10

4.5 Worm gear design ....................................................................................................................... 11

4.5.1 Strength calculation and material selection for worm and gear ........................................ 11

4.5.2 Design of worm gear ........................................................................................................... 11

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4.5.3 Design of worm shaft .......................................................................................................... 12

4.5.4 Design of worm gear shaft .................................................................................................. 12

4.6 Main Shaft design ....................................................................................................................... 12

4.7 Selection of bearing .................................................................................................................... 13

4.7.1 Bearing of main shaft calculation ....................................................................................... 13

4.7.2 Bearing of worm shaft calculation ...................................................................................... 13

5 Final Design ......................................................................................................................................... 13

5.1 Machine Specification ................................................................................................................. 13

6 CAD Model of the machine ................................................................................................................. 14

7 Advantages & Limitations of The machine ......................................................................................... 16

7.1 Advantages .................................................................................................................................. 16

7.2 Limitations................................................................................................................................... 16

8 Suggested Improvements ................................................................................................................... 16

9 References .......................................................................................................................................... 17

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List of Figures

Figure 1 Full automated machine and their important parts ....................................................................... 2

Figure 2 Lalit idiappam machine ................................................................................................................... 2

Figure 3 Typical available machine ............................................................................................................... 2

Figure 4 Functional analysis for string hopper making machine .................................................................. 5

Figure 5 Flange coupling ............................................................................................................................. 10

Figure 6 Details of worm and gear .............................................................................................................. 11

Figure 7 Forces acting on the worm and gear ............................................................................................ 11

Figure 8 Free body diagram of main shaft .................................................................................................. 12

Figure 9 Cad models of machine elements ................................................................................................ 14

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List of Tables

Table 1 Morphological chart ......................................................................................................................... 6

Table 2 details of morphological chart ......................................................................................................... 7

Table 3 Concept screening chart................................................................................................................... 8

Table 4 Final selection ................................................................................................................................... 9

Table 5 Design parts .................................................................................................................................... 15

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1 Background

1.1 Introduction

Food behaviours of developing countries like Sri Lanka are gradually getting changing in case of consuming fast foods. They have used to take instant food such as ready to eats. Most of them take simple food like bread, hoppers and string hoppers for their breakfast & dinner.As a matter of the fact these foods has a great selling market. So it clearly says there need to be an improvement in these food industries. From that we would like to pay attention to the string hoppers making industry.

String Hoppers is a Sri Lankan’s traditional food made by steaming process. This is made with rice flour after passing much process. It is served for the breakfast or dinner as main food with hot chilli coconut sambol, hot chilli powder gravy or sweet tasting white gravy made with coconut milk. Mainly string hoppers are eaten only in Sri Lanka, but it’s not like that main food. In India, Singapore, Malaysia & most of Asian countries eat string hoppers but with different names. In South India “PittuMayam” is “Indiappa” in Sri Lanka *1+. It’s a piece of evidence that we mainly eat string hoppers, for our breakfast or dinner and it´s a very famous dish in every part of the island, no matter you are rich or poor all Sri Lankans love to eat string hoppers.

1.2 Problem definition

String hopper is more favourable food in Sri Lankan context of food consuming. Therefore making string hopper is important as well as having significance difficulties. This string hopper making device is commonly made with a handheld hand-made wooden device consist of a small cup have a cylindrical through bore extend from its top to bottom. A metal plate with a large number of pores formed therein is mounted with screws at the bottom of the cup so that the bore forms a cylindrical tube therein for holding the rice dough. The cup has two grips extending outwards from its two opposite sides. A wooden cylindrical plunger having the corresponding size as the cylindrical tube is mounted on a carrier which also has two opposite side grip similar to the cup. The device is operated by placing the rice dough into the cylindrical tube of the cup and then inserting the plunger into the cylindrical tube and squeezing the grips of the plunger and the cup tightly towards another by hands so as to extrude the dough through the plate with the plunger to form the string hopper. While extruding the string hopper, the operator must also move the device in a circular motion so as to deposit the string hopper onto a steam tray for its subsequent cooking [2]. Following criteria describes the dominant problem in making string hopper.

o Health issue as lead to hand pain in traditional method. o Repetitive work it cause dullness to operator. o Low efficiency o Low productivity i.e. it can make bulk amount of string as need in once. o Cost factors – traditional method is more cost full to hire a person to squeeze string

hopper in case of food trader making with string hopper.

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2 LITERATURE REVIEW

In literature survey it has been seen that many types machines are developed to make string

hopper. Especially, in India the different types of machines are introduced in food industry such as “Lalit

Food Machines”, engineer mokan’s string hopper machine, Aarbee Engineering Industry’s Idiappam

Making Machine, etc. Most of the available machines are not adequate all the features that actually

needed by user. Further the available machines are not environment friendly as well as in economical

friendly. However the exiting devices have more powerful and making high production rate.

Furthermore the industrial machines are more bulky and expensive those are not coping with our

economy.

2.1 Available machines and their disadvantages

A. Aarbee Engineering Industry’s Idiappam Making Machine

Features

production capacity: 2,000 – 2,500 / hour

Idiappam die diameter: 100 – 110 mm

Idiappam thickness: adjustable

Machine construction: 100 % stainless steel

Power: 5000watts.

Operation: pneumatic with PLC controls.

Appearance: elegant

Size: 10 ft. (h) x 3 ft. (w) x 10 ft. (l)

Man power: one

B. Abc Agro & Food Machine India Private Limited Idiyappam Machines

Capacity – 250 pcs / hour onwards Power requirement – 3 hp, single phase Floor space - 2m x 2m x 2m

Figure 3 Typical available machine

Figure 1 Full automated machine and their important parts

Figure 2 Lalit idiappam machine

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2.1.1 Disadvantages of machines

Health issues:

Relatively large pressure must be exerted between the plunger and the cup in the operation, which requires a high degree of skill and effort to carry out the string hoppers. Furthermore, the device is unhealthy since it is difficult to clean any dough remains from the wooden cylindrical tube and between the cup and the metal plate. Those problems will cause to operators by hand pain, Arthralgia, hand spasms.

Repetitive work:

In traditional method, the movement of two hands squeeze and in circular motion in the same directions by several times is very dullness, awkward to carry out the process.

Low productivity:

Furthermore the overall production rate and efficiency are very low in traditional method and exiting machines.

The problem arises in making string hopper in home and as in edible industries is more difficult. If squeezing the plunger through the cup is difficult, it is possibly due to following reasons.

2.2 User needs analysis

Cheap

Most of the available machines are more expensive. So Machine Initial cost and

maintenance cost should be low

Quality

Machine’s product should be taste and quality like traditional one. And Machine

permanence should be high and functional and controlling also should be best

Safe

Machine parts and operation should not be harmful for the user

Less Power

Machine should have an efficient power controlling

Quickly

Machine able to extrude the string hopper quickly as well as conveyed out.

Portable

Machine should be easily moved by the user

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2.3 Engineer’s perspective of the design

Appropriate for Sri Lankan food industry

Reduce the time for making string hopper by making 10 string

hoppers per minutes

Size of the machine within the 1X1 m2 area and height as 1.5m

Power supply to the machine is less than 5kW

To transfer the power from power source to the machine with

Workability of the machine for large industries in urban area

Materials for the machine should be acceptable to food organization

code and conduct

Capacity of the machine around 5 kg of dough at the instant

Efficiency of the machine considered as more than 90%

3 SYSTEM DESIGN AND METHODOLOGY

Following units define the methodology of the project and system design with idea generation.

Further the concept generation and final selection of concept gives machine function and design

elements.

3.1 Methodology

Problem identification and define the scope of the project

Identify the user needs and define required specification

Conceptual design(Function analysis, Morphological chart and concept generation, analysis

and concept selection)

Draw the free body diagram and the velocity diagram and find requirements

Select proper material and make the design calculation of machine element

Design a 2D and 3D CAD model of the machine using solid works

Carry out through computer simulation of motion generation

Optimization and improvement of the overall design

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3.2 Concept Generation

3.2.1 Methods of string hoper making

As discussed above in literature survey there are various machines are available in the market. Hence

each machine has their own method to extrude the string hopper according to their construction. So

there is no proper method in making string hopper. The following section describe the major stages in

string hopper making as well as functions.

3.2.2 Functional Analysis

The following figure shows the functions of string hopper squeezing device which can

automatically getting the string hopper after feeding the dough to machine. These functions can be

performed different ways which are showed in following morphological chart.

Figure 4 Functional analysis for string hopper making machine

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1.1.1 Morphological chart

This chart describe the possible method to select concept which are mostly satisfying with above function

Table 1 Morphological chart

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3.2.3 Details chart of concept morphological

Table 2 details of morphological chart

Functions Concept 1 Concept 2 Concept3 Concept 4 Concept 5

Storing Within the cylinder for

batch process

Hopper with screw feeder

Hopper Within the cylinder for

batch process Hopper

Squeezing Power screw mechanism

Screw extruding

Sliding crank mechanism

Hydraulic system

2nd

Lever mechanism

Extruding Screw cup with holes

Screw cup with holes

Circular plate with holes

rectangle plate with

holes

Circular plate with holes

Shaping Rotating

mates Rotating

mates Manual Rotating mold Manual

Conveying Belt conveyer Rotating disk Manual Belt conveyer Manual

Power Source Manual Electric power Hand driven

Hydraulic power

(Electric power)

Hand driven

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3.3 Concept screening

Table 3 Concept screening chart

Concept Selection

Criteria

Concept

1

Concept

2

Concept

3

Concept

4

Concept

5

Can be operated by one person

10 10 10 10 10

High Storage Capacity 7 9 8 7 8

Capable of making several type

simultaneously 7 7 5 9 3

Can be used by disability

3 9 3 9 3

Easy to cleaning 7 5 5 7 8

Portability 7 5 5 5 7

Can be make various type foods

9 9 9 9 9

Redundant elements 5 4 7 3 8

Environmental safety 8 8 8 3 8

Easy to operate 5 9 5 9 5

Maintain free 5 5 5 3 8

Life time 6 8 6 4 8

Time consumption 7 9 7 9 3

Wastage 8 8 8 8 8

Power consumption 8 7 8 5 8

Total point

102

112

99

100

104

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3.4 Final selection

Table 4 Final selection

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4 SUMMARY OF CALCULATIONS

4.1 Power calculation

Evaluated torque = 1.7kNm Evaluated speed of rotating speed of the main shaft = 20 rpm Hence required minimum power of the machine= torque X angular velocities = 1.7 X 2 X π X 20/60 =3.56

kW Hence to overcome friction and other resistance power of the equipment 3.6kW

4.2 Barrel design

Material - Stainless Steel S43100 with allowable stress in tensile 140MPa and Safety factor is 2 Defined parameters for barrel Operating pressure of the barrel is 8MPa diameter D = 90 mm or R = 45 mm; P = 8 N/mm2; σt = 70MPa =

70 N/mm2; Then t=6mm

4.3 Motor selection

Motor selected as at speed 1000 rpm So required speed reduction is 50:1 Hence the worm and wheel is good for gear reduction and exerted torque will not affect motor

4.4 Coupling design

Coupling selected type as flange coupling because high torque transmission. Transmitting torque 1.7kNm d=35mm Hence L=52.5mm, d1=? , D=70mm, D2=140mm, D1=105mm, No of bolts is 3 Assume safety factor as 2 and Material-carbon steel .55% with Allowable Shear stress for shaft, bolt and key material = 282 MPa Crushing stress for bolt and key = 150 MPa Permissible Shear stress for cast iron = 30 MPa τs = τb= τk = 282 MPa = 282 N/mm2 ; σcb = σck =150 MPa = 150N/mm2 ; τc = 30 MPa =30 N/mm2

4.4.1 Design for key

Width of key, w = 12 mm and thickness of key, t = w = 12 mm

The length of key (l) is taken equal to the length of hub. ∴ l = L = 55 mm

4.4.2 Design for flange

T=

Since =6.929mm Take as 7mm

4.4.3 Design for bolts

Taken the number of bolts, n = 3 and pitch circle diameter of bolts, D1 = 3d = 3 × 35 = 105 mm Then calculated bolt size is M8 Other proportions of the flange are taken as follows: Outer diameter of the flange, D2 = 4 d = 4 × 35 = 140 mm Thickness of the protective circumferential flange, tp = 0.25 d = 0.25 × 35 = 8.75 say 10 mm

Figure 5 Flange coupling

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4.5 Worm gear design

No of starts is one Worm gear velocity ratio is 50:1 Ankle of pitch Pa=Pc =20mm Pressure angle Φ = 14.5°; μ = 0.05; λ Lead angle15.2°

1. Lead l =20mm 2. Normal pitch PN = 19.3mm 3. Pitch circle diameter Dw=60mm 4. Module of teeth m=7mm 5. Gear diameter DG=350mm 6. Outside diameter (DOG) =370mm 7. Throat diameter (DT) =360mm 8. Face width (b)=54mm 9. Radius of gear face (Rf) =32mm 10. Radius of gear rim (Rr)= 58mm 11. Face length (LW) = 100mm

12. Depth of tooth (h)= 13.72mm 13. Addendum (a) =6.36mm 14. Centre distance 205mm 15. Efficiency of the worm gearing η =82.84%

4.5.1 Strength calculation and material selection for worm and gear

Forces acting on the worm teeth

TW -tangential force

AW -axial force

4.5.2 Design of worm gear

a. Check for the tangential load Let – speed of the worm gear in rpm Tangential load adding on the gear =9.7142kN

Peripheral velocity of the worm gear, V = 0.733 ∴ Velocity factor =

=0.8911

Lewis factor y = 0.124 -

for involute teeth = 0.11

Worm gear material is phosphor bronze with σo= 84MPa

Figure 6 Details of worm and gear

Figure 7 Forces acting on the worm and gear

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Allowable Tangential load = (σ × ) b × πm × y = 9.777kN

b. Check for dynamic load

=

= 9.9653kN

c. Check for static load or endurance strength Assume - flexural endurance limit for phosphor bronze = 168 MPa Static load = = 21.945kN

d. Check for wear Assuming the material for worm as hardened steel, therefore hardened steel and phosphor bronze stress factor can be got from table31.5 reference [1].

K = 0.55 N Limiting or maximum load for wear = ×b×K=0.395kN

4.5.3 Design of worm shaft

Tgear=1.7kNm

Tworm =

=

=41.042Nm It known that tangential force on the worm,

WT = Axial force on the worm gear =

= 1440.07N

WA = Axial load on the worm

= 9714.28N

WR = Radial or separating force on the worm gear= WA . Tan Φ =2512.28N Material of worm shaft is carbon steel 0.55%carbon

4.5.4 Design of worm gear shaft

Material- Stainless Steel S43100 and with shear stress 200MPa – Diameter of worm gear shaft= 35mm Axial force on worm gear = 1440.07N Tangential force on worm gear = 9714.28N Radial force on worm gear = 2512.28N

4.6 Main Shaft design

Torque exerted on the shaft is T= 1.7 kNm

Safety factor as 3

Material - Stainless Steel S43100 with yield stress =0.6 tensile strength= 847MPa

As safety factor allowable shear stress 847/3 =282MPa

Since d=35mm

400mm

125mm 125mm

Self-weight

and

extruder

FT F

R

205

Figure 8 Free body diagram of main shaft

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Finally total bending movement affecting on the shaft also considered that were not affect with

diameter of the shaft as above calculated.

4.7 Selection of bearing

4.7.1 Bearing of main shaft calculation

Assumptions Average life = 10years at 8 hours per day

300 working days per year

Radial load = 2512.28N

Axial Thrust force when extruder extrude in word FT = 26228N

Axial load by worm = 1440.07N

Total axial forces =27668N

Hence selected 3 bearings are No 308 with Indian stranded

4.7.2 Bearing of worm shaft calculation

Assumptions Average life = 10years at 8 hours per day

300 working days per year

Operating speed N= 1000 rpm

There are 2 bearing has been decided to put in shaft

Radial force on worm = 2512.28N

Axial load on the worm 9714.28N

Finally radial forces on the each bearing =1256.14N

Axial forces on the each bearings = 4857.14N

Hence selected 2 bearings No are 308 with Indian standard

5 FINAL DESIGN

The project final design is having following specifications.

5.1 Machine Specification

Power of the machine is 3.6kW

Capacity of the machine at the instant is 5kg

production capacity: 500 – 600 / hour

Idiappam die diameter: 40-50 mm

Idiappam thickness: adjustable by changing die holes

Machine construction: stainless steel, other plastics material and aluminium alloys

Size: 1.25m. (H) x 1m. (W) x 1m. (l)

Man power: one

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6 CAD MODEL OF THE MACHINE

Figure 9 Cad models of machine elements

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Table 5 Design parts

PART NUMBER DESCRIPTION QTY.

1 Aluminium Table Frame

1

2 Teak wood table plate

1

3 Electric Motor

1

4 Worm

1

5 Worm gear

1

6 Extruder screw Not visible insight barrel 1

7 Barrel

1

8 Gear Box

2

9 Conveyer Pulley Not visible under rotating

conveyer 1

10 Rotating Conveyer

1

11 Conveyer pulley mount Not visible under rotating

conveyer 1

12 Die Plate

1

13 Clamp_60mm for die plate

1

14 Clamp_130mm with adapter and barrel

1

15 Adapter 130mm in front

1

16 IS 6455 SR - 03-40-S groove ball bearing

2

17 IS 6455 SR - 03-35-D sliding ball bearing no

308 5

18 Gear Shaft

1

19 Barrel Holder

1

20 Pulley38mm coupled with motor

1

21 Pillar Block for barrel

1

22 Flange coupling

2

23 B18.2.3.2M - Formed hex screw,

M8 x 1.25 x 50 --22CN 3

24 AM-M8-N nut 3

25 B18.2.3.1M - Hex cap screw, M10

x 1.5 x 70 --26N 6

26 B18.2.2.4M - Hex flange nut, M10

x 1.5, with 15 WAF --N 6

27 Pulley35mm main power transmission to

worm 1

28 Pulley 40mm for conveyer belt

1

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7 ADVANTAGES & LIMITATIONS OF THE MACHINE

7.1 Advantages

Strength

1. Reliable

2. No need of high technical knowledge

3. Even a female labor can participate this event

4. Low time consumption

5. Low pollution

6. Can use to assemble with various machine

Opportunities

1. Anyone can operate

2. Portable

3. Disability can use it

4. New concept for Sri Lankan market

5. Low noise pollution hence acceptable

7.2 Limitations

Weakness

1. High initial cost

2. Additional maintenance

3. Power source required

Threats

1. Cheap man power in Sri Lanka

2. Limits in usable area

8 SUGGESTED IMPROVEMENTS

The following criteria describes the improvement that are used to enhance string hopper making

machine design

The full automation may be introduced by PLC control panel and pneumatic valve.

The plastic material can be used in barrel to reduce the weight of the machine such as

ARAMID fiber plastic which is used in helmet manufacturing

It will introduce the sensor system such as limiting switch for safety improvement

Pneumatic or magnetic clutch can be used to stop between two operations (i.e. extruding

string hopper one after other should have interval to extrude dough).

Cam system could be used to improve above problem

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9 REFERENCES

*1+ R.S. Khurmi, J.K.Gupta “A Textbook of Machine Design”

*2+ A. W. Birley, B. Haworth and J. Batchelor, “Single-Screw Extrusion the Extruder

Characteristic” Physics of Plastics: Processing, Properties and Materials Engineering,

Hanser(1992) Chapter 4.

*3+ Peter Fischer, Johannes Wortberg “Single-Screw Extruders and Barrier Screws”

*4+ Chunguang Wang, Shaocong Dai and Roger I. “Tanner On the compressibility of bread

dough” Received May 17, 2006, final revision received August 23, 2006

[5] Design basis and hydrodynamic performance analysis of single-screw extruders