DESIGN OF SELECTIVE TEA 
PLUCKING MACHINE 
by 
R.P.P. Krishantha 
mmw 
UWIVFRSSTV :: : r/:r??AT,JiVA, sri lawka 
ii/10RATUV..'A 
Supervised by 
Dr. M.A.R.V. Fernando 
This thesis was submitted to the Department of Mechanical Engineering of the University 
of Moratuwa in partial fulfillment of the requirements for the Degree of Master of 
Engineering in Manufacturing Systems Engineering 
" 06 
v29 
Department of Mechanical Engineering -y&. \ - 7 (p&z) 
University of Moratuwa 
Sri Lanka 
July 2006 
University of Moratuwa ^ 1 
87893 
8 7 8 9 3 
Declaration 
This Dissertation paper contains no material which has been accepted for the award of 
any other degree or diploma in any University or equivalent institution in Sri Lanka or 
abroad, and that to the best of my knowledge and belief, contains no material previously 
published or written by any other person, except where due reference is made in the text 
of this Dissertation. 
I carried out the work described in this Dissertation under the supervision of 
Dr. M.A.R.V. Fernando. 
The Dissertation Proposal prepared by R.P.P. Krishantha is recommended and forward 
for onward action please. 
(Signature of Student) 
Name of Student: R.P.P. Krishantha 
Reg. No : 02/9639 
(Signature of Supervisor) 
Name of Supervisor: Dr. M. A.R. V. Fernando 
ii 
Acknowledgement 
I would like to express my sincere gratitude to Dr. M.A.R.V. Fernando, Senior Lecturer, 
University of Moratuwa, for guiding through the literature survey and for his guidance 
and inspiration to make this project a success. I would also like to thank Dr. A. G. T. 
Sugathapala, the Head of Mechanical Department, Dr. G.K. Watugala, Senior Lecturer, 
Dr. P.A.B.A.R. Perera, Senior Lecturer, and Mr. H..K.G. Punchihewa Lecturer, 
University of Moratuwa, Sri Lanka. 
I would like to thank the Coordinator Dr. U. Kahangamage, Senior Lecturer, University 
of Moratuwa, for the coordination and enthusiastic support extended during this special 
research project. 
Finally, I would like to thank all the staff members of the Department of Mechanical 
Engineering in "Manufacturing Systems Engineering" Master of Engineering Course. 
My special thanks go to Dr. M.A.R.V. Fernando for enlightening me with the concept of 
the Selective Tea Plucking Machine which was awarded the Best Innovation at 
"Innovations UOM 2005" the exhibition held on 16 t h - 18 t h September 2005 at BMICH. 
R.P.P. KRISHANTHA 
iii 
Abstract 
This thesis focuses on the research project is "Selective Tea Plucking Machine". 
According to my literature survey I have found that Tea plucking machines are designed in 
many countries but they are designed only for plucking and selecting method. These 
machines are very large and expensive. It is used only for flat land. However this at present 
is a completely manual process and is responsible for a substantial portion of the cost of 
tea manufacture. 
In manual plucking, plucking tea leaves are retained between fingers till reasonable 
amount of leaves are collected. Then 'holding between fingers' often cause some degree 
of crushing leading to commencement of premature fermentation. Therefore quality will 
be reduced. Thus it has become essential to mechanise this process to improve 
productivity, yet retaining the high quality and accuracy of selective plucking. 
Due to above technical and financial restrictions facing with research as well as depth of 
expected research study to be performed by using own methods to design low cost and 
portable machine. 
In this context is carried out considering selective plucking method. Further, considering 
the ergonomics aspects are essential for this design, it is useful to operate this machine 
without fatigue. It is based on less weight of the machine, holding and bag (container) 
arrangement. It is understood that the given detailed of the cutting mechanism and the tea 
leaves are transported to the bag (container) with suitable convey system. 
This report contains literature survey, field test, design details, and economic feasibilities. 
iv 
List of Illustrations 
(Page 1 of 2) 
4 
f 
Page# 
Figure 1.1 Tea State 1 
Figure 1.2 Tea leaf 3 
Figure 1.3 Tea bush 5 
Figure 1.4 Plucker with bamboo basket 7 
Figure 2.1 Banji 9 
Figure 2.2 Bud+ 3 ' units 13 
Figure 2.3 Tea plucking machine (Georgia) 15 
Figure 2.4 Tea plucking machine (Japan) 16 
Figure 2.5 Tea plucking machine (Sri Lanka) 16 
Figure 2.6 Tea plucking machine (Kenya) 17 
Figure 7.1 Strap arrangement 26 
Figure 7.2 Holding arrangement 27 
Figure 7.3 Holding grip arrangement 27 
Figure 8.1 Rotating cutter, Type I 35 
Figure 8.2 Rotating cutter, Type II 35 
Figure 8.3 Rotating cutter, Type III 36 
Figure 8.4 Parallel two belts (Horizontally) 37 
Figure 8.4 Parallel two belts (Vertically) 37 
Figure 8.6 Selection of structure, Type I 39 
Figure 8.7 Selection of structure, Type II 40 
Figure 8.9 Position of the Motor, Type I 40 
Figure 8.9 Position of the Motor, Type II 41 
Figure 8.10: Position of the Motor, Type III 41 
Figure 8.11: Ergonomically Design of Tea Plucking Machine 42 
Figure 8.12: Ergonomically Design of the Container 43 
V 
+ 
List of Illustrations 
(Page 2 of 2) 
Page# 
Figure 9.1 Transmission belt 45 
Figure 9.2 Transmission belt with Tea leaves 46 
Figure 9.3 Worm and Wheel diagram 48 
Figure 9.4 Basic model of the tea plucking machine 53 
Figure 9.5 Drawing of the Tea plucking Machine 54 
Figure 9.6 Field test 55 
Figure 10.1: Drawing of a Modified cutter 57 
Figure 10.2: Modification drawing with cutter 58 
Figure 11.1: Shape of the cutter 62 
Figure 11.2: Handgrip supporter 63 
•f 
vi 
• 
4 
List of Tables 
Page# 
Table 3.1: Sri Lanka Tea exports (during November-2005) 18 
Table 3.2: Sri Lanka Tea exports (at the end of the year-2005) 18 
Table 3.3: Sales of the Colombo tea auction (September-2005) 19 
Table 8.1: Selection of cutting mechanism 31 
Table 8.2: Tea leaves transferring in to bag 32 
Table 8.3: Selection of Power source 33 
Table 8.4: Selection of Tea leaves 34 
^ Table 8.5: Selection of Power transmission 38 
'} Table 9.1: Field test reading 44 
Table 9.2: Cutting force data 45 
Table 9.3: Sample test results 47 
Table 9.4: When k=2, rotational speed of the Transmission cable 50 
Table 9.5: When k=2.5, rotational speed of the Transmission cable 50 
Table 9.6: When k=2.75, rotational speed of the Transmission cable 51 
Table 9.7: Field test result of tea leaves 51 
* 
Table 11.1: Cost calculation of the machine 59 
Table 11.2: Projected manufacturing cost 60 
vii 
m 
Table of Contents 
Title 
Declaration 
Acknowledge 
Abstract 
List of Illustrations 
List of Tables 
List of Contents 
Page# 
1 
ii 
iii 
iv 
v 
vi 
vii-x 
4 
Chapter 1 - Introduction 
1.1 History of Tea in Sri Lanka 
1.2 Plucking system 
1.3 Plucking styles 
1.4 Time of plucking 
1.5 Different type of basket 
Chapter 2 - Introduction of plucking methods and machines 
2.1 Why is plucking so important? 
2.2 What is good plucking? 
2.3 Do not pluck coarse leaf and immature shoots 
2.4 Removal of (BJVNJIS 
2.5 Plucking 
2.6 Tea plucking machines in different countries 
Chapter 3 - Output quantity of finish production 
Chapter 4 - Problem involving in plucking 
Chapter 5 - Objectives 
1-2 
3-4 
5 
6 
6 
7 
8 
8 
8 
8-9 
9-10 
11-14 
15-17 
18-19 
20 
vni 
21 
V 
4 
Chapter 6 - Details of research 22 
6.1 Details of research up to now 22 
6.1.1 TRI (Tea Research Institute) project 22 
6.1.2 Machines in other countries 22 
6.1.3 Patent literature 22 
6.1.3.1 The concept of the present tea plucking machine 22 
6.1.3.2 Another tea plucking machine 23 
Chapter 7 - Ergonomics 24 
7.1 Basic aims of ergonomics for the plucking machine 24 
7.2 Benefits of ergonomics for the plucking machine 24 
7.3 Muscular work 25-27 
Chapter 8 - Need for a tea plucking machine 28 
8.1 User needs 28 
8.2 Engineering perspective 28-29 
8.3 Main problems 29 
8.4 Secondary problems 29 
8.5 Design tree diagram 30 
8.6 Selection of the best method 31 -43 
Chapter 9 - Cutting force calculation 44-52 
9.1 Basic model of the tea plucking machine 53 
9.2 Drawing of the tea plucking machine 54 
9.3 How to work portable machine 55 
Chapter 10 - Field test of the plucking machine 56 
10.1 Drawing of a modification cutter 57 
10.2 Modification drawing 58 
Chapter 11 - Estimate cost of making prototype 59 
11.1 Cost calculation of the machine 59 
ix 
4 
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mi 
t 
11.2 Projected manufacturing cost for 20 number of machine 60 
Chapter 12 - Discussion 61-63 
Reference 64 
Appendices 65-67 
Appendices A A1-A2 
Appendices B B1-B2 
Appendices C C1-C2