DESIGN OF ORGANIC WASTE SHREDDER MACHINE

 INTRODUCTION

Waste management and disposal of the waste seems to be a major problem in developing countries where huge amount of waste has been generated due to enormous consumption. And after disposal of waste there lie an issue of size of the waste as the smaller size will have larger surface area so there will be more contact between bacterial environment and the waste particles for quick decomposition. So, this project will be helpful for designing and developing a shredder machine which would be a helping hand for organic waste management and recycling the waste into bio-gas and compost as a product.

What is Shredder?

 Shredder is a machine or equipment which is used to reduce the size of the bulky material into fine particle for recycling or destroying purpose. Shredders can be of many types based on the material being processed. 

 Fig Motor operated shredder machine

Based on the purpose of use, shredders can be categorized as consumer shredders and industrial shredders. Thus, a paper shredder normally falls into the category of consumer shredder as it is mostly used by consumers. Industrial shredders are typically heavy-duty and high volume systems used to process such recycling material streams as e-waste, plastic,wood, and paper. Industrial shredders are equipped with different kinds of cutting systems such as vertical shaft design, horizontal shaft design, single shaft, two shaft, three shaft and four shaft cutting systems.

The use of the shredder in waste management and recycling
 

It has been realized that large quantity of waste remains being un-utilized and without being recycled because of handling, storage, transportation and management. In waste management, industrial shredders for waste products play a very crucial role. The benefits of using mega-shredders in large-scale waste disposal systems recycling centres and municipal landfills are related to material reduction. Asphalt, rubber, wood, plastics and similar materials can be quickly condensed to a mere fraction of their original size. Also, bio-degradable waste decomposes faster when shredded. If properly shredded, the materials that are buried in landfills take much less space.

In today’s economic environment, communities and businesses are always looking for new ways of cutting costs and use of shredders provides new strategic options. There are two main purposes of shredding materials in a recycling process. Firstly, by reducing the volume of material through reduction, transportation and storage costs may be decreased. Secondly, automated shredders, particularly in e-waste recycling, also liberate materials for recycling. Such equipment is offered by several vendors. Many options are available, depending upon the specific application.

 

There are different types of shredder machine, some are described below:-

Pedal Operated Shredder Machine
 

Fig  pedal operated shredder machine 

 A pedal operated shredder machine mainly required two operators one for peddling, another one for feeding purpose.ie is the main disadvantage for this machine. In this concept, the bicycle mechanism for converting and transmitting human energy through paddling to rotational kinetic energy of flywheel is hereby proposed. The energy stored in the flywheel can then use for actual cutting process. This human energy output is in the low range and the processes could be operated intermittently can be considered for utilization.

 

Hand operated chaff cutter machine

 Fig. Hand operated chaff cutter machine

The above figure shown is hand operated chaff cutter machine. Chaff cutters are meant for cutting all kinds of dry & green fodder into small pieces for cattle. These chaff cutters can chop the green or dry f Paddy, Grass, Groundnut etc. These machines are also useful for cutting, dry coconut leaves, Dairy Farms, and Jute Industries etc. where chopping is required. The advantages of the product are eco-friendly and maintenance is very easy.

 

Machine operated Shredder Machine

Fig  Machine operated Shredder Machine

The currently available product for cutting of coconut leaves is as shown in figure 1.4. In the present model the outcome is in the stick form and later it must be crushed to obtain in powder form and the feeding of the coconut leaves in the existing model is of vertical type, which is difficult to feed the coconut leaves. It requires tractor PTO (Power take off shaft) machine cost also very expensive .To overcome from these problems the proposed model is developed.

OBJECTIVE


The objective of the current work is to make a low cost shredder machine. To fulfill the main objective of the work the following sub objectives are formed.


⦁    To design the components of organic waste shredder machine.

⦁    To manufacture a working model of the proposed design.

 

 Components used:

     

 

The different components that have been used in the shredding machine are described below:-

- Cutting Blade

Fig. Stationary Blade

 

Fig.Stationary Blade

 

  It is the main component of shredding machine which is used to cut the organic waste into small pieces by the action of torque produced by electric motor. In this shredder machine two types of blades are used to cut the material, one is rotating blade and another is stationary blade.

 

 

Single Phase Electric Motor

Single phase electric motor is used to generate power in the shredding machine which converts electric energy into mechanical energy. The specifications of electric motor are as follows:

Input Voltage    220 – 240 V, 60 Hz

Power    0.746 KW

Speed    2700 rpm

 

 

 

Shaft   

Shaft is the component in which blades are mounted. When the electric motor generate torque, which when transmitted to the shaft the blades mounted on the shaft experience torque and rotate in desirable direction resulting the cutting action.

Ball Bearing

 

 

Belt Drive

Belt drive is a mechanical drive which is used to transmit power from electric motor to the shaft where blades are mounted by driver and driven pulley. The ratio of driver and driven pulley is determined by the speed ratio between the speeds produced by the electric motor to the speed required to cut the organic waste.


 Mesh Plate

It is a plate having desired holes in it. Its main function is to prevent the passing of larger size particles through it to get desirable sized output. The dimension of blade is shown in figure

 

Fig. Mesh plate

 

Switch Board

Switch Board is used to start and stop the motor when required. It contains switch and indicator.

 

 

 

 

METHODOLOGY


The method of designing the shredder machine start with gathering the information of necessity of the shredding machine and collecting the data from the literature review for development of specific mechanism. After collecting the information we made our effort to identify the mechanism and their roles in shredding machine to get the desired output.

Design Procedure


The basic procedure of the design consists of a step by step approach from specification about the functional requirement of the product to the complete description in the form of drawing of final product.

Fig Flow chart diagram of design process

 

First of all, we defined a specification of the shredding machine according to the requirement to cut organic waste. In order to cut organic waste a cutting torque is defined corresponding to required cutting force. Depending upon the specification that can fulfil the desired function different mechanisms are studied.

In order to reduce the cost of the shredding machine we have selected a simple mechanism. For example we have used a single shaft where number of blades are mounted and driven by an electric motor through belt drive system.

While selecting material we focused on the material that is easily available and also have strength compared to its cost. In case of cutting blades we have used mild steel and for belt drive, mineral-tanned leather is used as belt material. The design calculation of different components are explained below.
 

(a) Design of pulleys: 

 

Cutting force (F) =190. 

 

Torque required to generate cutting force,

 

(Treq)= F×r ……….eqn (1) 

 

Treq = 190×0.05 = 9.5 Nm. (r= 5cm) 

 

For electric motor 

 

P = 0.746 KW, N = 2700 rpm 

 

From power and torque relation,

 

 P= (2𝜋𝑁𝑇)/60 ……….eqn (2)

 

 N= (𝑝×60) /(2𝜋𝑇) = (0.746×1000×60) /(2𝜋×9.5) = 747.87 rpm

 

 From speed ratio,

 

 𝐷2 /𝐷1 = 𝑁1 /𝑁2 = 2700 /749.87 = 3.6 ……….eqn (3)

 

 Ratio of 𝐷2 /𝐷1 = 3.6

 

 If we take the driver pulley diameter as 5cm then, 

 

D2= 3.6×5 = 18 cm=180mm (Since the available pulley size is 20cm)

 

 Therefore, driver and driven pulleys of diameter 5cm and 20 cm are taken.

 

 

 Now to find the centre distance between two pulleys,

 

 v = (𝜋𝐷2𝑁2)/ 60 = (𝜋×0.20×747.87)/ 60 = 7.83 m/s ……….eqn (4)

 

 

 

An empirical formula to select centre distance from the condition of longevity of the belt,

 

 C = (0.07 to 0.1)v , assuming C=0.07×v

 

 C= 0.07× 7.83 = 0.5481 m =54.81 cm.

 

 Length of the belt (for open belt system),

 

 L= 2C + (π /2) (D1+D2) + {(D2−D1) ^2}/(4C) ……….eqn (5)

 

 L= {(2×54.81) /100 } + [(π/ 2) × {(20+5)/100 }]+ { ( 20−5 100 )^2/(4× 54.81 100) }

 

 = 1.49 m ~ 1.5 m =150cm 

 

 

 

(b) Design of shaft: 

 

Power transmitted by belt,

 

 P= ( T1−T2) v ……….eqn (6)

 

 T1−T2 = {(0.746×1000)/ 7.83} = 95.27 ……….eqn (7) 

 

𝜃 =180+Sin-1 {(𝐷2−𝐷1)/2𝐶}= 180+ Sin-1 {( 20−5)/( 2×54.81)} = 187.86 deg =3.28 rad 

 

From tension ratio, 

 

𝑇1 /𝑇2 = 𝔢^(𝜇𝜃) ……….eqn (8)

 

𝑇1/𝑇2 = 𝑒^(0.4×3.28) = 3.71 (value of 𝜇 is taken from design data book 

 

T1=3.71 T2 ……….eqn (9)

 

From eqn (7) and eqn (9),

 

T2×(3.71−1) = 95.27 

 

T2 = 35.15 N 

 

From eqn (9),

 

T1 = 3.71 × 35.15 = 130.42 N

 

 

Bending moment calculation:

 

For horizontal deflection of shaft, Taking linear equilibrium condition, 

 

RA+ RB = T1+T2 

 

RA+ RB = 165.57 ……….eqn (10) 

 

Taking equilibrium moment condition about A, 

 

RB = {165.57 × (299.5)}/ 270 = 183.66 N 

 

Fig. Free body diagram of force acting on a shaft for horizontal deflection .

 

 

From eqn (10),

 

RA = 165.57 – 183.66 = −18.09 N 

 

Bending moment, At A, BM = 0 

 

At B1, BM = −18.09 × (25/1000) = −0.45 𝑁𝑚 

 

At B2, BM =−18,09 × (25+20)/1000 = −0.81 𝑁𝑚 

 

Similarly, At B3, BM = −1.17 𝑁𝑚 

 

At B4, BM = − 1.53 𝑁𝑚 

 

At B5, BM = −1.9 𝑁𝑚 

 

At B6, BM = −2.26 𝑁𝑚

 

At B7, BM = −2.62 𝑁𝑚

 

At B8 , BM = −2.98 𝑁𝑚 

 

At B9, BM = −3.34𝑁𝑚 

 

At B10, BM = −3.7 𝑁𝑚

 

 At B11, BM = −4.07 𝑁𝑚 

 

At B12, BM=−4.43 𝑁𝑚 

 

At B, BM = −4.88 𝑁𝑚 

 

At C, BM = 0 𝑁𝑚  

 

Fig. Bending moment diagram for horizontal deflection 

For vertical deflection,

 

Mass of pulley (m) = 125 /981 N

 

 Fc = F + 1×9.81    (as 1 kg of mass is acting per blade)

 

 Fc = 190 + 9.81 = 199.81

 

Taking vertical equilibrium condition 

 

RA + RB = (199.81 × 12) + (125/ 981)

 
 RA + RB = 2397.85 N ……….eqn (11) 

 Fig.. Free body diagram of force acting on a shaft for vertical deflection

Taking equilibrium moment condition about A,

 

 RB × 270 = 199.81 (25+45+65+85+105+125+145+165+185+205+225+245) + (125/981 ) ×299.5 RB = 1199 N

 

 From eqn (11), 

 

RA = 2397.85 −1199.25 = 1198.6 N

 

To find bending moment, 

 

At A, BM = 0 At B1 , 

 

BM = 1198.6× 25 /1000 = 29.97 Nm

 

 At B2, BM = (1198.6× (25+20)/1000) – (199.81× 20/1000 ) = 49.94 Nm

 

 At B3, BM = (1198.6× )25+40)/1000 ) – (199.81× (20+40)/1000 ) = 65.92 Nm 

 

At B4, BM = (1198.6× (25+60)/1000 ) – (199.81× (20+40+60)/1000 ) = 77.9 Nm 

 

 

Similarly, 

 

At B5, BM = 85.89 Nm 

 

At B6, BM = 89.88 Nm

 

At B7, BM = 89.88 Nm 

 

At B8, BM = 85.89 Nm 

 

At B9, BM =77.9 Nm 

 

At B10, BM = 65.92Nm 

 

At B11, BM = 49.94 Nm 

 

At B12, BM= 29.97 Nm 

 

At B, BM= -0.07 Nm 

 

At C, BM= 0 NM 

Fig.4.10. Bending moment diagram for vertical deflection of shaft 

 

From figure, maximum bending occurs at point B5,

 

 Therefore resultant bending moment,

 

      

M = √{(89.88)^2 + (−2.62) ^2 }= 89.918 Nm ~ 89.92 Nm

 

 T = 9.5 Nm

                                                                       

Equivalent bending moment, Me= 1 /2 {𝑀 + √(𝑀^2 + 𝑇^2)} ……….eqn (12) 

                               

Me = 1 /2 {89.92 + √(89.92^2 + 9.5 ^2)} = 90.17Nm 

                                                          

Equivalent twisting moment, Te = √(𝑀2 + 𝑇 2) ……….eqn (13)

   

 = √(89.92^2 + 9.5^2) = 90.42 Nm 

 

For S.A.E. 1025 carbon steel(as carbon content 0.22 to 0.28 % content falls at the range of carbon content of mild steel having 0.04 to 0.3%) 

 

For S.A.E 1025 steel material, 

 

𝜎yp = 234 MN/m2

 

𝜏yp = 138 Mn/m2 

 

Factor of Safety   F.O.S= 4

 

 Now, Design stress = 𝑦𝑖𝑒𝑙𝑑 𝑠𝑡𝑟𝑒𝑠𝑠 /𝐹𝑎𝑐𝑡𝑜𝑟 𝑜𝑓 𝑆𝑎𝑓𝑒𝑡𝑦 ……….eqn (14)

 

 So, 𝜎 = 58.5 𝑀𝑁 𝑚2 ,    𝜏 = 34.5 𝑀𝑁 𝑚2

 

 From bending equation,

 

 𝑀𝑒 /𝐼 = 𝜎 /𝑦 ……….eqn (15) 

    

d = 3√{(90.17×64)/(𝜋×2×58.5×10^6)}  = 0.02504 m = 25 mm

 

Again from torsion equation, 

 

𝑇𝑒/ 𝐽 = 𝜏/ 𝑟 ……….eqn (16) 

            

So, d = 3√ {(90.42×32)/( 𝜋×2×34.5×10^6)} = 0.0237 m = 23.7mm 

 

Therefore, maximum diameter is 25 mm so standard diameter of shaft is 25 mm. 

 

The final layout of the model is shown in fig

Fig. Front view of shredding machine

 

 

 

 

 Fig. Top view of shredding machine

 

 

 

 

RESULT AND DISCUSSION

The different components of shredding machine are designed as per the design specifications. As per our design data the different components are fabricated. The different fabricated components of the machine are shown below:

 

 

Fig. Shaft

 

 

 

 

         Fig. Rotating Blade                               Fig. Stationary blade

  

                                 Fig. Blades and pulley mounted on shaft                               Fig.Clamp

 

 

    Fig.Stationary blades mounting arrangment

 

 

 

Fig.Front view of shredder machine  

Specifications are as follows:

After successful fabrication of working model of shredder machine, performance is evaluated to determine the shredding efficiency of the machine. The cutting rate of the machine has been found out as 16.08kg/hr at an operational speed of 710rpm. Hence the shredding efficiency is found to be 57.26%.

 CONCLUSION 

 

 This project provides a view of design about a waste shredder machine with respect to the required specification features. 

 

Proper evaluations of the design are performed and fabricated something even better instead of simply manually operated machine. The machine is designed taking into considerations the various parameters and specifications. The machine will be ideal equipment for chopping the organic residues to obtain organic compost. The shedding machine can be used in commercial as well as helping point of view for small business, providing organic compost to agricultural sectors also. 

 

The following important points were drawn from our work:

 

 Machine cost is low as compared to other shredding machine

 

 Easy maintenance 

 

 Highly skilled labours are not required for operating

 

 Less area occupied by the machine

 

 

 Since the beginning of a project can realize the importance of organic waste shredder for what they serve, realize the work can get done faster and more efficient when wastes are crushed. 

 

Future scope 

 

Development of semi-automatized into fully automatized Organic waste shedder.

 

Cutting rate can be further increased by developing the blade material. 

 

Better efficiency can be achieved by regulating the working speed.