Diseño del Circuito electrico para una calibradora por peso

Misr J. Ag. Eng., January 2006

192

UTILIZATION OF ELECTRONIC CIRCUITS TO OPERATE A GRADING PROTOTYPE MACHINE FOR SOME FRUITS

AND VEGETABLES ON WEIGHT BASE

S.M. Gomaa*, H.M.H. Sorour**, O.M. Kamel***, and E.M. Ghazy****

ABSTRACT The constructed automatically grading prototype was tested and

evaluated in Rice Mechanization Center (R.M.C.) by using two different types of fruits. The performance evaluation was conducted during grading the Cara potato and Navel orange under four feed speed, four grading unit belt speeds and two positions of starting weight

The measurement which were accomplished in the present study include physical and mechanical properties for Cara potato and Navel orange. That they can be exploited in designing and fabricating the proposed grading prototype, productivity, efficiency and costs of the constructed grading prototype have been determined.

Results indicated that the grading prototype is quite successful for grading both Cara potato and Navel orange under study. The optimum operational conditions for obtainging a maximum grading efficiency were 0.14 m/s feeding chain speed, 0.30 m/s weight belt speed and 0.125 m starting weight position.

Technical evaluation showed that the productivity valnes of the grading prototype machine were 0.369 and 0.530 Mg/h for Cara potato and Navel, orange respectively at the optimum operational methods. The cost of material and fabricating of automatically grading prototype was 5000 LE. The total costs (fixed + variable) of machine was 3.87 LE/h, but the total costs were 10.49 and 7.30 LE/Mg for both Cara potato and Navel orange at the optimum operational methods.

1.INTRODUCTION

rading includes two basic processes. The first one is sorting the product for removing undesirable and rotten material; such a process runs in most cases manually and by dint of trained workers. The second process

is sorting out the product into categories in term of distinctive features suchlike shape, size, weight or maturity degree; such a process runs either manually or mechanically yet, the whole process of grading runs

G*Prof. of Agric. Eng.,Agric. Mech. Dept., Faculty of Agric.,Kafr El-Sheikh, Tanta Univ. **Assoc. Prof. of Agric. Eng.,Agric. Mech. Dept., Faculty of Agric.,Kafr El-Sheikh,

Tanta University ***First under Secretary and Head of Agric. Mech. Sector, Ministry of Agriculture. ****Agric. Eng., in Rice Mechanization Center (R.M.C)

Misr J. Ag. Eng., 23(1): 192 – 216


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mechanically, it is preferred, since manual grading is less efficiency and more costly. Actually, the mechanical methods of grading counts are difference in characteristic as for as the fruit is concerned- like length, width, weight, etc. In case of fruits that are of systematic dimension, size- related methods are best; while in case of fruits that are not of systematic dimensions, weight- related methods are most fitting.

Electronic grading is one of the modern grading systems, which is applied to both processes and has been studied and implemented for different agricultural products such as citrus, apple, tomatoes and potatoes. It includes the presentation of objects separately to a measuring unit; individual measurement of objects, classified by means of signal processing and routed by a transport mechanism in different direction, and the use of different successively operating components, such as sensors and actuators, each performing a specific task.

Brennan et al. (1979) stated that many fruits (e.g. apples. pears and citrus fruits) and vegetables (e.g. potatoes, carrots and onions) are sorted by weight. Typical weight sorting machines carry fruits in tared canvas pockets attached to pivoted beams fitted with counterbalance weights. As the beam pass along the sorter, the beam fulcrum is moved towards the counterbalance weight until such time as the weight of the fruit causes the beam to tip discharging the fruit into padded chutes in weight categories. They add that recent development in weight-sorting machines involve the use of Electro-mechanical and hydrostatic transducers to sense weight differences and improved devices, often computer-controlled, for directing the weighed units into collection chutes. A novel approach to the problems of high-speed weighing is represented by a machine, which measures electronically the cross-section dimensions of potatoes at 0.635 cm. intervals along their length axes. These dimensions are converted into weights by a computer, which then sorted the potatoes into 4 weight categories at rates up to 4500 kg/h.

Mcrae (1985) showed that the application of electronics to weighing systems has led to the development of high-speed check-weighers and belt-weighers. These use load transducers, which can weigh about five objects per second.

Peleg (1985) reported that another class of weight sizers employs a single weighing mechanism (electronic scale), which weight all fruits in a single file. An electromechanical or elector optical memory apparatus counts and signals a mechanical push-off or activates a compressed air stream, which sends the appropriate fruits to their respective side delivery belts or packing bins. The main disadvantage of weight sizers is the relatively long time required to weight each fruit. Even “continuous flow” scales actually have a weighing cycle of about 1or 2 s. The length of the weighing cycle is proportional to the accuracy of the scales. Thus, throughput is quite limited if a reasonable weighing


194

accuracy is specified. Another drawback is relatively high cost and considerably more complexity, as compared to dimensional sizer.

Ball (1986) reported that the produce must be fed singly over any weigher system. The mechanical method for this is to channel it into a single stream in a chute of vee section, and deposit it onto a cupped singulator conveyor. Feeding the weigher spacing on the singulator is achieved by running it faster than the channel feed, so that each item is taken away before the next one drops. The cups on the singulator are shaped in an attempt to allow them to hold only item, so that doubles and trebles are eliminated. This is often aided by sloping or vibrating the cups, and hand correction can be applied at this stage. The singulator and weight grader tend not to run at 100 percent cup filled capacity. This better ensures that each cup contains only one item.

According to Amin, (1994). The grading productivity has been calculated by using the following equation:

1 ...................................................................................................... 60

T

xMC

G

Where: C = Grading productivity of the machine, Mg / h; M = Mass of classified fruit, Mg and TG = Grading time, min. Peleg (1985) and Amin (1994) cited that the efficiency of grading for

an outlet can calculated according to the following equation:

2.................................................................................................. 1001 M

M

Where: M1 = Mass of the fruits falling within the size category of an outlet, kg

and M =Total mass of pre-classified fruits for the outlet, while

the total grading efficiency is the summation for all outlet, kg.

The main objective of the present study was to construct and fabricate an

automatic grading prototype for grading some vegetables and fruits on weight base. The electronic circuits have been designed and utilized to operate the grading prototype automatically. The physical and mechanical properties of the Cara potato tubers and Navel orange fruits had been investigated to determine the main operational and designing parameters affecting the performance of the proposed grading prototype.


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2. MATERIALS AND METHODS

Materials:

a. Tested crops: Cara potato and Navel orange crops were used in the present study.

b. Automatically grading prototype:

An automatic grading prototype on the weight basis has been constructed and developed locally at the engineering workshop of Ric Mechaichition Center, Meet EL-Dyba, Kafer EL-Sheikh Governorate. (R.M.C). It grades the different vegetables and fruits automatically on the weight basis. The fabricated automatic grader is sketched in Fig.1 and it consists of the following main parts:

1- Frame; 2-Feeding unit; 3- Weight and grading unit; 4- Distribution unit 5- Transmission system and 6- Control system.

1- Frame:

The grader frame consists of three parts which are main frame , distribution unit frame and feeding unit frame.

The main frame of the fabricated grading prototype has been was manufactured from square shape iron steel. Another four square sectors were vertically fixed on it . A free wheel was fixed at the ends of each bar.

The distribution unit frame was used for carrying the distribution unit, and constructed from hollow cylinder made from metal sheet, the distribution unit is fixed on the top of the cylinder. Three iron bars have been fixed on the cylinder sides to carry the distribution table.

The feeding unit frame has been constructed from angle steel bars. The feeding chain and hopper are fixed on it. This frame consists of two opposite right triangles, between of them a feeding chain which is fixed on three gears in the triangle vertexes. It is driven by means of the gear fixed in the right angle by another chain connecting with the transmission unit. The feeding hopper is fixed on the chord of the right triangle in its down end.

2- Feed unit:

The main function of the feed unit is to feed the weight and grading unit with single fruits at equal times which could be controlled. The feed unit consists of the following main parts:


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a- Feed hopper:

A rectangular feeding hopper was designed fabricated and fixed on the feeding unit frame of the proposed grading. It was made from galvanized steel. The hopper dimensions were 50 cm length, 45 cm width and 67 cm height. To ensure that a shallow of fruits is presented in front of the feeding spoon (cups), this hopper is divided by means of lateral slider diaphragm to avoid the spoon from passing through a dense layer of fruits. Consequently, reducing the damage, which may occur to the fruit sprouts during the grading operation. The base sides of the hopper sloped gradually at angle over the repose angle of about 38 deg of the fruit to keep the flow of fruits at continuos rate. To avoid the free falling of fruits from the hopper bottom at the outlet chamber, a semi-cylindrical tube with diameter of 10 cm and height of 20 cm was joined to the hopper bottom, which is regarded to be more than the distance between two consecutive spoons.

b- Feed chain:

The feed chain was made of iron with 364 cm length, 20 spoons have been fixed on the feed chain along the chain to pick the fruits from the hopper. This chain is mounted on three supported iron gears as shown in Fig.1. The three gears have been fixed on the right triangle vertexes. The fixed gear on the right angle of the triangle called the drive gear of the feeding chain. Another two gears fixed also on the shaft of the drive gear. One of them transmits the motion from the main operating motor to the shaft of the drive gear, Consequently transmits the motion to feeding unit. But, the second one transmits the motion from the shaft of the drive gear to the distribution unit.

OPERATING

ADJUST

+

DOWN

BALANCE ADJUST

Z ERO

UP

-

STANDBY

CATEGORY(4)

START

ON

POWER

OFF

-

CATEGORY(1)

CATEGORY(2)

CATEGORY(3)

OVER & LESS

ADJUST

-+

-+

-+

+-

+OFF

Maximum weight, Category(1)

Minimum weight, Category (1)




OFF

O N

Screen reset Auto.

Manual

Gram

Motor startAuto.

Weight adj. OVER LOAD

Feed hopper

Feed chain

Cub

Weight unit

Orientor

2

1

3

4

10

8

9

6

7

distribution disc frame

6

Synchronous unit

Distribution table

Control box109

7

8

No. Part name

3

4

5

12

Main frame

Dim. in cm.

5

11

12

Feed unit frame1112 Distribution unit frame

180

25027 88 75 60

85

Fig. 1: Schematic diagram of grading prototype machine


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c- Spoons (cups) of the feeding chain:

The spoons of the feeding chain have been constructed from aluminum metal. Each spoon has two turgids to pick and carry the single fruit from the hopper to the weight and grading unit.

d- Fruits orientation:

A cuboid orientor, which has been used in the fruits orientation, has been fixed in the upper angle of feeding chain frame. The orientor can be bind the fruits between its outer wall and feeding chain at changing the fruit orientation as a result for rotating it. So, the fruit fall from the end of orientor onto the weight and grading unit belt.

3- Weight and grading unit:

The weight and grading unit has been consisted of two hollow opposite rectangular frames. The electronic circuits required for adjusting the synchronization between the weight and distribution, infrared lamps concerning to the weight operation. There were two plastic rollers between the two frames, The weight and grading unit belt has been fixed on the back and front rollers. The back roller is rotated by electrical motor, 12 volt DC which is separated than the transmission group of the grading prototype. The weight and grading unit has been fixed on a free axial near the back edge of the weight and grading unit frame with the frame which carries the feed units. It was attached to the feed frame by means of two ball bearings. A bar has been fixed in the down part of the two rectangular frames, a slice of iron was connected in the center of the bar, which was fixed between two side of copper pulley connected on the middle of the weight sensor.

4- Distribution unit:

The distribution unit was mainly consisted of the main following parts:

a- Synchronous unit. b-The distributor disk. c- The distributor table.

a- Synchronous unit:

The feeder of the distribution unit called synchronous unit, it has been consisted of two gates which were formed semi-cylinder at closing it as shown in Fig.1. The synchronous unit received the weighted fruit and opened for falling the fruit into the gates of distribution unit. The gates of synchronous unit have been opened and closed by means of solenoid, which was controlled by using an electronic circuit.

b- The distribution disk:

The distribution disk has been consisted of two circular rings, which were constructed from metal sheet. The diameter of the outer ring was 70 cm


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but, the diameter of the inner ring was 20 cm. The distance between the outer and inner rings was divided into 10 equal sections each of them equipped with a vertical moving gate on the horizontal axial. It is fixed below each gate a spring for its attracting into an electromagnet.

A lead weight has been jointed with the inner back edge of each gate for adjusting the balance around the horizontal axial of the gate. The gates have been closed during the operation by electromagnets which take their orders from the gates control circuit.

The distribution disk was carried on a hollow roller which was attached to the distribution frame by means of two ball bearings. The distribution disk has been driven by means of a chain through out the power transmission unit consequently, the distribution disk is rotated. It has been fixed on the inner ring the electronic circuits required for closing and opening the gates which take their orders by wires connected with slippers which were fixed on the hollow roller.

c- The distribution table:

The distribution table is a circular disk, which was fixed below the fruits distribution disk. Number of baskets were put on the distribution table to receive the graded fruits. 5- Transmission system:

The transmission system has been consisted of two electrical motors were used for driving each of feeding and distribution units in addition to weight and grading unit. A main electrical motor, which has gear box (Model: M425-201), 100 volt AC, 25 W, 1400 -1700 r.p.m and variable speed, has been used for operating the feeding unit by means of a drive shaft. The motion is transmitted from the drive shaft to the distribution unit by means of chain, two gears and gear box with reduction ratio 10:1. An another electrical motor, 12 volt DC, 50 W, 40 r.p.m., variable speed was used for driving the belt of weight and grading unit. There were a synchronization between both of the feeding and distribution units by means of different gears in the diameter and number of teeth.

6- Control system:

The control system has been comprise number of electronic circuits for controlling in the feeding rates by means of the control in the feeding chain speed and weight and grading unit belt speed. The control system also weight the fruits singly by means of processor which has been controlled in the position of the fruit outlet according to its category which has been determined by means of a programming circuit. The control system consists of the following main electronic circuits:

a- Power supply circuits; b- Pulses generating circuit;


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c- Weight circuit; d- Programming circuit; e- Screen circuit and f- Controlled gates circuit.

a- Power supply circuits:

The main function of these circuits is to supply all the electronic circuits and its additional, namely: coil and relays, with the voltage required for their operating according to the design. Three groups of the power supply have been used in this design. b- Pulses generating circuit:

The main function of this circuit was to generate pulses which were used for determining the gates position. The pulses generating disk was a circular disk, its out circumference divided into ten equal sections by slits with 5mm depth in the same direction of center. These slits were numbered from zero to nine and were used to generate the synchronization pulses (Clock pulses). On the other hand, an another slit is located between the ninth slits and the zero slits at a small distance from the disk center and it was used to generate the reset pulses. This disk has been fixed in the driven shaft of the distribution unit and during its rotating passes between two group of photo coupler each of them has been consisted from infrared transmission LED(Light Emitting Diode) and infrared receiving LED.

The clock and reset pulses have been generated during rotation the disk and at locating the slit between the transmission and receiving LEDs the infrared rays pass from the transmission LED through the slit to the receiving LED consequently, a pulse has been generated. When the disk rotates one round, ten pulses are generated for determining the position of gates. After generating the ten clock pulses and before starting a new cycle of the pulses generating disk, a reset pulse has been generated as a result for passing the infrared rays through the slit located between the ninth slit and the zero slit. c- Weight circuit:

The main function of the weight circuit was to determine the weight of the graded fruits as a volt value. This circuit has been consisted of the following electronic circuits:

1. Sensor; 2. Amplifier and zero adjusting circuit; 3. Volt to frequency convertor circuit; 4. Timing circuit;

a-Starting weight position circuit; b-Timer circuit;

5. Frequency pass controlling circuit and 6. Frequency to volt convertor circuit.


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1- Sensor:

A piezoelectric sensor, Germany made Type DW1, has been comprised electronic circuit which convert the pressure on the sensor disk to mA (milli Ampere).

2- Amplifier and zero adjusting circuit:

The main function of this circuit was to amplify the sensor signal using a variable resistor. The weight and grading unit presses on the sensor during the grading operation consequently, a volt is generated which is suitable with the weight and grading unit. During motion the fruit with the weight and grading unit belt, a volt is generated from the sensor as a result to the fruit pressure on the sensor.

3- Volt to frequency convertor circuit:

The main function of this circuit was to convert the output voltage from the sensor, which was amplified, to frequency as linear regression (one volt equal 1000 Hz).

4- Timing circuit:

The timing circuit, which has been used in this designing, consisted of two main parts. The first part included starting weight position circuit. But, the second one was timer circuit. a- Starting weight position circuit:

The main function of this circuit was to determine the position of the weight starting on the weight and grading unit belt by using transmitter and receiver LEDs. During the motion of the fruit on the weight and grading unit belt, it passes between the receiving and transmitting LEDs consequently, it prevents conveying the ray from the transmitter to the receiver thus, it gives signal which was used for operating the timer circuit. b-Timer circuit:

The main function of the timer circuit was to determine the time of sample weight with a high accuracy where, the mistake ratio was not exceed about one per million. At passing the fruit between the transmitter and receiver LEDs, a pulse has been generated from the starting weight position circuit for operating the timer circuit to generate and determine the time of the sample weight, its value 100 ms.

5- Frequency pass controlling circuit:

The main function of this circuit was to control in passing the generated frequency as a result to weight the fruit during the operation interval of the timing circuit.


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6- Frequency to volt convertor circuit:

The main function of this circuit was to convert the frequency resulting from weight the fruit, during the determining time, into volt and its enlarging in addition to fixing this volt until it was compared in the programming circuit with the determined volt for each grading category.

d- Programming circuit:

The main function of the programming circuit was to determine the maximum and minimum weight of each grading category and showed the value of weight by screen during programming operating. e- Screen circuit:

The main function of this circuit was to display the fruits weight during the grading operating or display the weight during the programming operation addition to display the value of belt speed of weight and grading unit during adjusted its speed belt f- Gates control circuit:

The main function of the gates control circuit was to control in opening the gate which carries a fruit determined category in its falling position. The main gates control circuit has been consisted of ten similar circuits in the function and construction, each of them controls in the open of a determined gate. g- Signals transmission circuit:

The main function of the signals transmission circuit was to convey the data concerning with the fruits category from the gates control circuit into the distribution unit to carry out the orders. This circuit has been consisted of two main circuits as follows:

1-Parallel to sequent data converting circuit. 2-Sequent to parallel data converting circuit.

1- Parallel to sequent data converting circuit:

The main function of this circuit was to convert the signals passing from the parallel to sequent for transmitting it into the distribution unit by means of one slipper instead of ten slippers 2- Sequent to parallel data converting circuit.

The main function of this circuit was to convert the transmitted signals by means of slipper from sequent to parallel and its distributing for the relays in order to control the opening and closing the gates.

At carrying the gate with fruit during the grading operation, the gate stays closed until reaching the convenient position of the fruit weight consequently, the signal passes through the transistor of this gate which cut off the electrical


202

current about the coils by relay and the magnetic field avoid thus, the gate is opened and the fruit falls in the suitable position.

METHODS:

Mass of fruit :

One hundred sample for each Navel orange and Cara potato were randomly selected to determine the average mass of each fruit by using an electronic balance with an accuracy of 0.01 g.

Coefficient of friction:

Coefficient of friction for the Cara potato and Navel orange have been measured by using two friction surfaces which were smooth rubber and galvanized steel. According to (Abd El-Mageed and Abd Alla, 1994) the fruits or tubers have been placed over the friction surface and the tension force on the fruit surface was gradually increased and stopped when the fruit begin to move. Coefficient of friction has calculated using following equation:

3 .......................................................................................... ...... tan M

P

Where: μ = Coefficient of friction, dimensionless; P = Force required to start fruit movement on the horizontal plan, N; M = Mass of fruit, N and θ = Angle of friction, deg.

Rolling angle:

The rolling angle has measured by using an inclined plan with two types of surface galvanized steel and smooth rubber. The orange fruit or potato tubers have been placed on the horizontal surface of the inclined plat one by one and then by gradually increasing the angle of inclination, until the fruit begin to roll, and the recorded angle is considered as the rolling angle of the fruit or tuber.

Impact height:

Impact height of potato tubers and orange fruit were accomplished by free fall dropping of each sample from different height ranged from 0.3 to 2 m. The tested sample have been marked and sorted for weeks in room temperature (Amin, 1994). The bruised samples were separated based on the visual inspection of discoloration appeared on the flesh surface of the impacted fruits and tubers.

Productivity:

The productivity and efficiency of grading machine have been determined according to (Amin, 1994). The productivity has been calculated according the following equation:


203

4 ............................................................................................. ...... 60

T

MC

G

Where: C = Productivity of the machine, Mg / h; M = Mass of classified fruit, Mg and TG = Grading time, min.

Grading efficiency: The grading efficiency of each outlet has been calculated according to

the following equation:

5 ...................................................................................... ...... 001 1 MM

i

Where:

ξ i = Grading efficiency of fruit, %; MI = Mass of the classified fruits for each outlet, Mg and

M = Total mass of the fruits for each outlet in the machine, Mg. The total efficiency of the grading machine has been calculated using the

following equation:

6 ....................................................................... .... 001 x 3 2 1

MMMM

Where: ξ = Total grading efficiency of the machine, % ; M1 + M2 + M3 = Masses of the proposed

classified fruits for first, second and third outlets, Mg. and

M = Total mass of the fruits for each outlet in the machine, Mg. Power unit requirements for the machine operation:

The consumed power ( kW ) has been estimated by using the multi-meter, 700 volt (AC), 10 ampere- (Japan made) to measure the line current strength and the electric potential. The electric power required for operating the grading machine has been computed according to (Abd-Alla et al. 2000) by using the following equation:

7 ..................................................................................... ...... 1000

cos

EIPeL

where: PeL = The electric power required by the graing machine, kW; I = Electric current, Ampere; E = Electric potential, Volt and

Cos θ = power factor, equal 0.64.


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The power unit required operating grading achine has been calculated by using the following equation:

Power unit = power, kW / poducivity, Mg.

Cost of grading operation:

The total cost of grading machine includes charges for ownership and operation. Ownership costs are seemingly independent of use and are often called fixed costs or overhead costs. Fixed costs include depreciation, interest on investment, taxes, housing and insurance. Costs for operation vary directly with the amount of use and are often called variable costs, or operating costs. Variable costs include repair and maintenance, electricity and labour. Grading cost LE/ h or LE/ Mg for the proposed grading machine was estimated according to (El -Khawaga, 1999) as follows: A- Fixed costs (FC ): 1- Depreciation (D):

9....................................................................................................... - L

SPD

Where: D = Depreciation cost, LE; P = Machine purchase price, LE; S = Salvage value at the end of machine life (0.1 P), LE and L = Machine life, year.

2- Interest (I):

10................................................................................................ 2 - iSPI

Where: I = Interest on investment. LE / year and i = Interest rate, decimal.

3- Taxes, housing and insurance cost: The taxes, housing and insurance costs had been assumed to be 2 % of

the purchase price of the machine (P). Then:

Fixed costs ( LE / year ) = D + I + 0.02 P Fixed costs ( LE / h ) = (D + I + 0.02 P) / yearly operating hours.

B- Variable costs (VC ): 1- Repair and maintenance costs (RM):

The repair and maintenance costs (RM) = 100 % depreciation cost / total operating hours per year, LE/ h. 2- Energy (Electricity) cost (E):

E = Energy consumption (kW.h) x power price (0.25 LE/ kW), LE/.h. 3- Labour cost (La):

La = 1.5 (LE/h) x 2 labours


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= 3 LE/h. Then:

Variable costs (VC ) LE/h = RM + E + La

C- Total costs (TC ): Total costs (LE/h) = Fixed costs (LE/h) + Variable costs (LE/h).

D- Important assumptions: The following assumptions indicated in Table 1 were used for estimating

the cost of the proposed grading machine:

Table 1: Assumption for cost of the machine

No Item Value 1 Machine price ( P ), LE 5000 2 Salvage value ( S ), LE 10 % of ( P ) 3 Housing and insurance ( Hi ), LE 2 % of ( P ) 4 Interest rate ( i ), LE 12 % 5 Energy price ( e ). 0.25 LE/ kWh 6 Machine life ( L ), year. 8 7 Yearly operation ( h ), hours. 2000

The present study aims to: 1- Design, fabricate and test a locally automatic grading prototype for

grading some vegetables and fruits on the weight basis 2- Test and evaluate the grading prototype performance and efficiency

under different operation methods. a) Four feed speeds: 0.14, 0.17, 0.21 and 0.24 m/s; b) Four speeds of weight unit belt: 0.3, 0.45, 0.6 and 0.75 m/s and c) Two positions of starting weight: 0.08 and 0.125 m from connected

point between weight and grading unit and sensor. 3- Estimate the cost of the machine production.

The automatic grading prototype has been fabricated, tested and evaluated technically and economically under different operating conditions at the development section and engineering workshop of Rice Mechanization Center, Kafr EL-Sheikh, Governorate, Agricultural Engineering Research Institute, Egypt during 2003, 2004 and 2005 years.

3. RESULTS AND DISCUSSION

1- Physical properties of the graded fruits:

The physical properties of the Cara potato tubers and Navel orange fruits have been measured as one of the important factors affecting on the designing and fabricating the weight grading prototype and also affecting the transporting, handling and exporting operation of these fruits. The physical properties, which have been measured of the potato tubers, include length, width, thickness,


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volume, mass, density, shape index, length shape and thickness shape the physical properties, which have been measured of the Navel orange fruits, include length, diameter, shape index, volume, mass and density as tabulated in Table 2.

Table 2: Physical properties for Cara potato and Navel orange.

Items Crop Length,

mm

Width,

mm

Thickne

ss, mm

Shape

index

Length

shape,

Thickne

ss

Mass,

g

Volume,

cm3

Density,

g/cm3

Av.

Potato 71.70 63.10 50.40 1.28 14.30 80.07 133.2 120.2 1.11

Orange 72.50 72.40 ----- 1.00 ----- ----- 191.50 230.3 0.8

Max.

Potato 88.00 81.00 66.00 1.53 45.90 99.00 198.00 185 1.25

Orange 84.00 84.00 ------ 1.10 ------ ------ 295.00 153.0 0.5

Min.

Potato 55.00 50.00 41.00 1.09 0.13 61.98 77.00 70.0 0.9

Orange 60.00 63.00 ----- 0.80 ------ ------ 114.00 423.0 1.2

S.D.

Potato 7.32 6.04 9.29 0.11 9.30 7.36 31.92 29.5 0.1

Orange 4.60 4.51 ------ 0.04 ------ ------ 43.25 42.8 0.2

C.V.

Potato 10.21 9.59 10.49 8.54 61.30 9.15 23.03 23.6 7.2

Orange 6.34 6.23 ------ 4.00 ------ ----- 22.64 18.6 18.8

2-.Mechanical properties:

a- Coefficient of friction :

The suitable surface which gives high value of friction coefficient between the grading machine surface and the tested fruits surface must be found to satisfy the design requirements. The average values of static Coefficient of friction (μ) for the potato tubers and orange fruits have been determined on a various surfaces used for the proposed design (galvanized and smooth rubber). The values of coefficient of friction were 0.5 and 0.41 for potato tubers and orange fruits, respectively, using smooth rubber sheet surface. The corresponding coefficient of friction were 0.76 and 0.55 for potato tubers and orange fruits, respectively, using galvanized steel. The previous mentioned results revealed that, the maximum value of friction coefficient was 0.76 which was obtained using the galvanized steel surface with Cara potato . But,


207

minimum value was 0.41 due to using the smooth rubber sheet surface with Navel orange.

b-.Rolling angle:

The rolling angle was an important factor which was used for determining the slope of the inner surface of tuber tank in addition to determine the slope of the transport belts. The rolling angle on smooth sheet rubber and galvanized sheet surfaces for potato tubers and orange fruits have been measured. The experimental work has been conducted at one position of fruit movement where the long axis of fruit was laid vertical to the direction of motion.

The obtained values of rolling angle at smooth sheet rubber and galvanized sheet surfaces were 0.27 rad ( 15.7 deg) and 0.29 rad (16.59 deg) respectively, for the Cara potato. The corresponding values for Navel orange were 0.08 rad (4.59 degree) and 0.11 rad ( 6.45 degree) using smooth sheet rubber and galvanized steel surfaces, respectively. It can be noticed that the rolling angle on the smooth sheet rubber surface was smaller than which was recorded with the galvanized steel surface for the two tested fruits. However, the potato tubers recorded higher angles of rolling than which were achieved with the orange fruits.

c- Impact height:

Impact height must be studied as one of the important factor for determining the height which caused the fruit damage and the corresponding potential energy of fruit to avoid damage. The maximum impact heights, which caused damage for potato tubers and orange fruits, were 1.7 and 1.5 m, respectively. While, the corresponded impact height which cased bruise of potato and orange were 1.4 and 1.3 m, respectively. The above mentioned results had been considered at calculating the proper dropping height of fruits at different positions of the grading prototype. In general, the maximum used height 10 cm.

3- Efficiency of grading prototype:

a- Effect of the feed speed on the grading efficiency:

The effect of increasing the feed chain speed from 0.14 to 0.24 m/s on the grading efficiency of the constructed automatic grading prototype for all speeds of weight and grading unit belt in range of 0.3 - 0.75 m/s and at two positions of starting weight of 0.08 and 0.125 m under different fruits ( Cara potato and Navel orange ) has been indicated in Table 3. It can be noticed that increasing the feeding chain speed during the grading process tended to


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decrease the grading efficiency of the automatic grading prototype for all the belt speeds and starting weight position under two different grading crops.

The obtained grading efficiencies from the automatic grading prototype were 91.7, 88.2, 63.3 and 55 % at feed chain speeds of 0.14, 0.17, 0.21 and 0.24 m/s respectively, with belt speed of 0.3 and starting weight position of 0.08 m for the Cara potato. The other belt speeds and starting weight positions had the same above mentioned trend. The results indicated that increasing the feed chain speed from 0.14 to 0.24 m/s caused a corresponding decrease in the grading efficiency of the automatic grading prototype of about 40 % at 0.30 m/s weight belt speed and 0.08 m starting weight position. This trend may be attributed to increase the fruit speed on the weight unit belt as a result to increase feeding chain speed consequently, decrease the fruit stay interval on belt thus, decrease the accuracy of the weight and increase the overlapping percentage which tends to decrease the efficiency.

Also, the feed chain speed of 0.14 m/s achieved the maximum grading efficiency compared with the other feed speeds for all the belt speeds and starting weight positions. While, the minimum grading efficiency had been obtained with the maximum feeding chain speed of 0.24 m/s. Using the automatic control for adjusting speed of the feeding chain by means of electronic circuits has been caused increasing the feed uniformity consequently, increasing the grading efficiency.

Table 3: Effect of feed speed on the grading efficiency as percentage of Cara potato and Navel orange fruits under different weight belt speeds and starting weight positions.

Feed speed,

m/s

Starting weight

position,

m

Weight belt speed, m/s

Cara potato Navel orange

0.30 0.45 0.60 0.75 0.30 0.45 0.60 0.75

0.14 0.080 91.7 91.5 86.0 85.0 95.0 94.2 93.3 88.0

0.125 95.0 95.0 89.0 88.0 98.3 98.0 96.7 93.3

0.17 0.080 88.2 85.0 85.0 82.5 94.0 93.3 90.0 85.8

0.125 92.5 90.0 87.5 85.0 96.0 95.7 93.3 88.3

0.21 0.080 63.3 72.5 80.0 82.5 63.3 80.0 82.0 83.0

0.125 67.5 77.5 84.2 85.0 65.8 84.2 85.0 86.0

0.24 0.080 55.0 63.3 65.0 79.2 60.0 71.7 78.3 79.0

0.125 61.7 68.3 70.0 82.5 65.0 78.3 81.7 82.0


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b- Effect of the weight belt speed on the grading efficiency:

From Table 3, it has been concluded that, at the lowest values of feeding chain speeds (0.14 and 0.17 m/s), increasing the weight belt speed tended to decrease the grading efficiency of the automatic grading prototype at all the starting weight positions and the tested fruits.. But, the grading efficiency of the automatic grading prototype increased when the speed of weight belt increased at the highest values of feeding speeds (0.21 and 0.24 m/s).

However, at the minimum values of feeding chain speeds, increasing the weight belt speed tended to decrease the grading efficiency for all the starting weight positions and graded fruits. This trend may be attributed to decrease the fruit stay interval on the weight and grading unit belt consequently, increasing the fruit weight interval until the pocket of Synchronous feed unit was opened which caused overlapping as a result to vary the synchronization time.

But, the grading efficiency of the automatic grading prototype has been increased when the weight belt speed was increased at the maximum values of the feeding chain speeds for all the starting weight positions and the graded fruits. The reason for this was due to increase the fruit stay interval on the feeding chain therefore the fruit take the same weight belt speed and synchronize with the pocket of synchronous feed unit opening.

The results also indicated that the weight belt speeds of 0.30 m/s recorded the highest grading efficiency at the minimum values of feeding chain speeds ( 0.14 and 0.17 m/s) while, it achieved the lowest grading efficiency at the maximum values of feed chain speeds (0.21 and 0.24 m/s) for all the other variables under study. From Table 3, it can be noticed that the results for grading Navel orange fruits take the same above maintained trend for Cara potato tubers.

c- Effect of starting weight position on the grading efficiency: The obtained data in Table 3 represents the values of grading efficiency

as affected by the starting weight position under different speeds of feedi chain and weight belt for the Cara potato and Navel orange. It can be noticed that, for all the feeding chain and weight belt speeds, the starting weight position of 0.125 m has been accomplished the maximum values of grading efficiency compared with the 0.08 m starting weight position for both type of graded fruits.

It can be also seen from the same Table, for all the starting weight positions, feeding chain and weight belt speeds, the grading efficiency of the automatic grading prototype was higher at grading the orange fruits compared with the Cara potato tubers. This reason may be due to increase the uniformity of fruit shape, which has a spherical shape, consequently increasing the accuracy of the weight thus, increasing the grading efficiency. But, the potato


210

tubers had not uniform shape which affects on the weight accuracy therefore, the grading efficiency.

Finally, the effect of study variables on the grading efficiency could be concluded as follows:

for all the weight belt speeds and starting weight positions, increasing the feeding chain speed tended to decrease the grading efficiency for the automatic grading prototype.

Increasing the weight belt speed tended to decrease the grading efficiency at the minimum values of feed chain speeds (0.14 and 0.17 m/s) and increasing the grading efficiency at the maximum values of feeding chain speeds (0.21 and 0.24 m/s) for all the starting weight positions and the graded types.

For all the feeding chain and weight belt speeds, the starting weight position of 0.125 m accomplished the highest values of grading efficiency compared with the other starting weight position of 0.08 m with the potato tubers and orange fruits.

The automatic grading prototype recorded higher grading efficiencies with the orange fruits compared with the potato tubers for all the starting weight positions, feeding speed chain and weight belt speeds.

The optimum conditions for grading both Cara potato tubers and Navel orange fruits, which had been recorded the maximum grading efficiency, were using the automatic grading prototype at feeding chain speed of 0.14 m/s, weight belt speed of 0.30 m / s and weight starting position of 0.125 m.

4- Productivity of automatic grading prototype:

The data presented in Table 4 represents the calculated productivity of the automatic grading prototype as affected by the feeding chain speed under two different types of crop.

Table 4: Effect of feed speed on the grading productivity for Cara potato tubers and Navel orange fruits.

Feed speed, m/s

Productivity, Mg/h

Potato tubers Orange fruits

0.14 0.369 0.530

0.17 0.448 0.644

0.21 0.553 0.795

0.24 0.632 0.909


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0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26Feed speed, m/s

Pro

duct

ivit

y

40

50

60

70

80

90

100

Gra

ding

eff

icie

ncy

Productivity Efficiency

Fig. 1: Relationship between feed speed, efficiency and grading productivity of Cara potato.

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.12 0.14 0.16 0.18 0.2 0.22 0.24 0.26

Feed speed, m/s

Prod

ucti

vity

40

50

60

70

80

90

100

Gra

ding

eff

icie

ncy

Productivity Efficiency

Fig. 2: Relationship between feed speed, efficiency and grading productivity of Navel orange.

The productivity of grading prototype increased as a result to increase the feeding chain speed for the two graded fruits. Increasing the feeding chain speed from 0.14 to 0.24 m/s tended to increase the productivity of the automatic grading prototype by 71.3 % during grading the potato tubers. While increasing the feeding chain speed tended to increase the productivity of grading prototype which has been increased by 71.5 % during grading the Navel orange.

From the above data presented in the previous Table, it can be noticed that the obtained productivity values, during grading the orange fruits were higher than which were given with the potato tubers for all the feeding chain speeds. This trend may be attributed to increase the fruit weight average than the tuber weight average but, graded number of fruits equal graded number of tubers per time unit.

The results also illustrated that the productivity of automatic grading prototype increased by 43.8 % in case of grading the orange fruits compared with the potato tubers at feed chain speed of 0.24 m/s. On the other wise, for the potato tubers and orange fruits, increasing the feeding chain speed tended to increase the productivity and decrease the grading efficiency of the automatic prototype as shown in Figs. 1 and 2


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5- Power unit required for grading operation:

The power required for operating the automatic grading prototype had been consumed for driving both of feeding unit chain, distribution disk and weight and grading unit belt as well as the power required for operating the solenoid of synchronization unit. The automatic grading prototype has been operated at 220 volt and 1.7 ambere so, the power required for grading prototype operation was approximately constant i.e. 0.374 kW at the different operating conditions. The data listed in Table 5 represent the calculated power unit for operating the automatic grading prototype as affected by the different feeding chain speeds under two different types of the graded crops. Table 5: The Power unit consumed during grading Cara potato tubers

and Navel orange fruits.

Feed speed, m/s

The power unit consumed, kW/Mg

Potato tubers Orange fruits

0.14 1.01 0.71

0.17 0.83 0.58

0.21 0.68 0.47

0.24 0.59 0.41

6-Cost analysis:

The cost evaluation for the grading machine at suitable operating method at feeding chain speed 0.14 m/s. The results presented indicated that the total fixed cost was 0.5 LE/h while , the variable cost was 3.37 LE/h at the lowest feeding chain speed of 0.14 m/s. However, the total costs required for grading operation were 3.87 LE/ h.

The total cost of Cara tubers grading using the automatic grading prototype was 10.49 LE/ Mg while it was 7.30 LE/ M g for Navel orange fruits. For all the feeding chain speeds, the grading costs for Navel orange fruits were less than which were recorded with Cara potato tubers. This may be attributed to increase the grading productivity in case of grading Navel orange fruits compared with Cara potato tubers.

4- Summary and conclusion

1. The grading efficiency of the automatic grading prototype has been increased when the feed chain speed decreased for all the weight belt speeds and starting weight positions under two graded fruits.


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2. The results indicated at the lowest values of feeding chain speed (0.14 and 0.17 m/s), increasing the weight belt speed tended to decrease the grading efficiency of the automatic grading prototype at all the starting weight positions and the tested fruits

3. For all the feeding chain and weight belt speeds, the starting weight position of 0.125 m has been accomplished the maximum values of grading efficiency compared wit the 0.08 m starting weight position with the different graded fruits.

4. The automatic grading prototype recorded higher grading efficiencies with the orange fruits compared with the potato tubers for all the starting weight positions, feeding speed chain and weight belt speeds.

5. The optimum conditions for grading both Cara potato tubers and Navel orange fruits, which had been recorded the maximum grading efficiency, were using the automatic grading prototype at feed chain speed of 0.14 m/s, weight belt speed of 0.30 m/s and starting weight position of 0.125 m.

6. The productivity of grading prototype increased as a result to increase the feeding chain speed for the two graded fruits. Increasing the feeding chain speed from 0.14 to 0.24 m/s tended to increase the productivity of the automatic grading prototype by 71.3 % during grading the potato tubers.

7. The obtained productivity during grading the orange fruits were higher than which were given with the potato tubers for all the feed chain speeds.

8. The power required for grading prototype operation was approximately constant i.e. 0.374 kW at the different operating conditions.

9. The power unit consumed for driving and operating the automatic grading prototype decreased when the feeding chain speed increased for the two graded fruits.

10. The total cost of Cara tubers grading using the automatic grading prototype was 10.49 LE/ Mg while it was 7.3 LE/ Mg for orange fruits. For all the feeding chain speeds, the grading costs for orange fruits were less than which were recorded with potato tubers. This may be attributed to increase the grading productivity in case of grading orange fruits compared with potato tubers.

5. REFERENCES

Abd-Alla, H. El.; S.M. Radwan ; M.M. El-Kholy and M.S. Radwan (2000). A weight grading machine for different fruits and vegetable Misr J. Agric. Eng., 17(3): 675-696.

One American dollars = 5.85 Egyptian pound (LE) according to price of 2005.


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Abd El-Mageed, H.N. and H. E. Abd-Alla. (1994). A simple machine for grading fresh tomatoes. J. Agric. Sci., Mansoura Univ., 19 (9): 3033 – 3047.

Amin, E. A. (1994). Development of grading machine for some Egyptian farm crops. J. Agric. Sci., Mansoura Univ., 19 (7): 2398 – 2411.

Balls, R.C. (1986). Horticultural engineering technology fixed equipent and buildings. Macmillan Publishers 18-31.

Brennan, J.G.: J.R. Butters: N.D. Cowell and A.E.V.Lilly (1979). Food engineering operations (Second Edition). Applied Science Pub. Limited London 36-39.

El-Khawaga, S. E. (1999). Developing of a harvesting machine for some fruit crops. Unpublished Ph. D. Thesis, Agric. Mech. Dept., Fac of Agric., Mansoura. Univ.

Mcrae, D.C. (1985). A review of developmments of potato handling and grading. J. Agric. Eng. Res., 31: 115-138.

Peleg, K. (1985). Produce handling, packaging and distribution. AvI Pub. Comp., INC. Westport, Connecticut. 91-103.


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الملخص العربى

استخدام الدوائر االليكترونية لتشغيل نموذج آلة تدريج لبعض ثمار الفاكھة والخضر على أساس الوزن

٤عصام محمد غازى – ٣أسامة محمد كامل – ٢حسين محمد سرور – ١سمير محمود جمعة

يث تؤدى الى تعتبر عملية التدريج من أھم عمليات تداول المنتج الزراعى بعد عملية الحصاد، حونظراً لتباين ثمار الخضر والفاكھة فى .رفع جودة المنتج النھائى سواًء لالستھالك المحلى أو للتصدير،

صفاتھا الطبيعية من حيث الشكل والحجم والوزن واللون ودرجة النضج والصالبة وغيرھا مما يؤثر ً على جودة الثمار بصفة عامة أثناء عمليات التداول المختل فة وبالتالى تقل قيمة العائد النھائى للمنتج، سلبا

من ھنا تظھر أھمية عملية التدريج فى المحافظة على جودة الثمار مما يؤدى إلى تقليل نسبة الفاقد فى وتجرى عملية التدريج إما يدويا أو . عالوة على تلبية احتياجات المستھلك بالسعر الذى يناسبه، المحصولوقد أدى قصور آالت التدريج الحجمى فى . اء عملية التدريج بالطرق الميكانيكيةويفضل إجر، ميكانيكيا

تدريج اكثر من محصول الى زيادة تكاليف عملية التدريج مما أدى الى االتجاه الى استخدام آالت التدريج .الوزنى والتى تعتبر من اكثر الطرق المناسبة لتدريج المحاصيل الزراعية باختالف أنواعھا

ذلك نظ راً لعدم توفر ماكينات التدريج الصغيرة فى المزارع المتوسطة والصغيرة فى مصر وكعدم مالئمة ماكينات التدريج الكبيرة وارتفاع تكاليف تشغيلھا فإن ھذه الدراسة تھدف إلى تصنيع وتطوير

ة ى وتقييم آلة لتدريج ثمار الفاكھة والخضر على أساس الوزن باستخدام الطرق اإللكتروني ا يساعد عل ممغيل اءة التش عة وكف ادة س راء . زي رة إلج ال صنف ابوس ارا والبرتق اطس صنف ك ار البط م اختي د ت ولق

.االختبارات المعملية والحقلية على اآللة

:متغيرات الدراسـة )أبو سرة( و برتقال صنف ) كارا( بطاطس صنف : نوع المحصول] ١[ ).ث/ م ٠.٢٤، ٠.٢١، ٠.١٧، ٠.١٤: ( سرعة جنزير التغذية ] ٢[ ).ث / م ٠.٧٥، ٠.٦، ٠.٤٥، ٠.٣: ( سرعة سير وحدة الوزن] ٣[ م من نقطة ارتكاز وحدة الوزن على حساس ٠.١٢٥و ٠.٠٨نقطتان لبداية عملية الوزن على أبعاد ] ٤[

.الوزن

:أھم النتائــج المتحصـل عليھـا

د ة عن ة الكلي ا حوالى بلغت اإلنتاجي امالت التشغيل الموصى بھ ا جرام ٠.٣٦٩مع ساعة /ميج .ساعة بالنسبة لمحصول البرتقال/ميجا جرام ٠.٥٣و ، بالنسبة لمحصول البطاطس

ة غيل لآلل اءة تش ى كف ت أعل ة ) ٪ ٩٥(كان ر التغذي د سرعة جنزي ارا عن لصنف البطاطس ك .م ٠.١٢٥بداية الوزن من ث و مسافة نقطة /م ٠.٣٠ث وسرعة سير وحدة الوزن /م ٠.١٤

ة اءة تشغيل لآلل ة ٪ ٩٨.٣كانت أعلى كف ر التغذي د سرعة جنزي ال ابوسرة عن لصنف البرتق .م ٠.١٢٥ث و مسافة نقطة بداية الوزن من /م ٠.٣٠وسرعة سير وحدة الوزن ) ث/م ٠.١٤(

أثبتت التجارب المعملية عدم وجود أى تلف داخلى أو خارجى للثمار المدرجة . ة اء عملي امالت التشغيل الموصى أثن د مع ة المستھلكة عن أوضحت الدراسة أن حسابات الطاق

وات١.٠١تدريج محصول البطاطس كانت ا كانت / كيل وات ٠.٧١طن بينم طن بالنسبة / كيل .لمحصول البرتقال

.جامعة طنطا-كلية الزراعة بكفر الشيخ - قسم الميكنة الزراعية -أستاذ الھندسة الزراعية .١ .جامعة طنطا - كلية الزراعة بكفر الشيخ - قسم الميكنة الزراعية - أستاذ الھندسة الزراعية المساعد .٢ اع الميكنة الزراعيةوكيل أول وزارة الزراعة ورئيس قط .٣ .الجيزة -الدقى–مركز البحوث الزراعية –بمعھد بحوث الھندسة الزراعية -مھندس زراعي .٤ ٢٠٠٥جنيھا مصريا طبقا السعار عام ٥.٨٥= الدوالر االمريكى


216

ا امالت التشغيل الموصى بھ د مع ١٠.٤٩بلغت التكليف الكلية لتدريج محصول البطاطس عن .ميجا جرام بالنسبة لمحصول البرتقال/ جنيه ٧.٣٠طن بينما كانت / ه جني

:التوصيات: سـابعاً

:من النتائج المتحصل عليھا يمكن التوصية باآلتى ال والبطاطس .١ ار البرتق اً لثم ا إليكتروني تحكم فيھ وزن ي ى أساس ال دريج عل ة ت يمكن تصنيع آل

.خامات المحلية وبمواصفات فنية عاليةبكفاءة تدريج عالية وبجدوى اقتصادية من ال :قيم مؤشرات أداء آلة التدريج كاآلتى .٢

ث/ م ٠.١٤انسب سرعة لجنزير وحدة التغذية. ث/ م ٠.٣٠انسب سرعة لسير وحدة الوزن. م ٠.١٢٥انسب مسافة لنقطة بداية الوزن.

تقبليا ضرورة دراسة إمكانية استخدام اآللة فى تدريج العديد من محاصيل الخضر .٣ ة مس والفاكھ .مما يعظم االستخدام االقتصادى لآللة

دريج .٤ وزن بوحدة للت ى أساس ال دريج عل تبدال وحدة الت فى الدراسات المستقبلية ابضا يمكن اسة مع ضرورة اجراء ) اللون ( على أساس الحجم أو درجة النضج دون إجراء أى تعديالت على اآلل

امامقارتة لتحديد اى الطرق افضل استخد

٢٠٠٥جنيھا مصريا طبقا السعار عام ٥.٨٥= الدوالر االمريكى

Diseño del Circuito electrico para una calibradora por peso

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