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
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