Automatic Weighing

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A project report on automatic weighing and packaging

Transcript of Automatic Weighing

MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

CHAPTER 1 INTRODUCTION

In Industry weighers & weighing mechanisms are to be very accurate. Without this accuracy, extraction figures are meaningless. Weigher is the necessity either to weigh or to weigh the final products to calculate extraction rate. Low cost automatic weighing machine using latest technology of servo control and Programmable Logic Control (PLC) was designed and developed considering the advantages of electronic weighing and linear motion guide ways moving accuracies. The results of studies carried out for automatic weigher indicated that the equipment could be used as weigher. Statistical analysis indicated that there was no significant difference in mean value of measurements from set weights and measured weights at the 95% probability level. Automatic weighing equipment can be successfully used for weighing and dosing of products into bags, containers in automated production processes. Automatic weighing machine consists of hopper, weigher with hooks arrangements for empty bag & drop hole mechanism. Full open to half open or full close of the gate operates through drop hole mechanism is used to fill the specified quantity of matter into the bag which affects the accuracy of weighing. Continuous monitoring of set weight and matter feeding was absent. Conventional filtering methods employed in dynamic weighing systems have limitation in improving accuracy and throughput rate .Fluctuations in the bulk density of the raw materials in volumetric or rotary charger dosing results in alterations in weight. Weighing machines equipped with platform scales or beam balances with dials do not ensure the required accuracy of weighing batch materials. Mechanical scales are not reliably precise and their applications in automatic lines are complicated. Mechanically operated weighers are obsolete and maintenance oriented. Electronic weighers are sophisticated and calibrate themselves by using built in

calibration procedures and saves the data themselves. Load cells are widely used in a variety of industrial weighing applications such as wending machines and weighing systems. Load cells interfaced with integrated electronics convert the weight force to an electric signal and deliver the output signal to an automation system. Linear motion guide ways accompanied with precision ball screw can greatly enhance moving accuracy. Hence, considering the advantages of DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING Page 1

MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

electronic weighing accuracy and linear motion guide ways moving accuracy, the present project is undertaken to design and develop state of art technology i.e. low cost automatic weighing machine using latest technology of servo control and Programmable Logic Control (PLC) concepts. The equipment works on the basic principle of batch weighing. Working flow diagram is as shown in the Figure.1. Raw material to be weighed is automatically fed to the weighing hopper through a quantity regulating servo slide. The movement of the slide is controlled by precision linear motion guide way assembly which is driven by brushless servo motor. Feeding of the material from the collection hopper to the weighing hopper is done in coarse and fine feed. Automatic weighing cycle starts with wide opening of the servo slide followed by weight register by the load cells. During rapid movement of the servo slide, more quantity of material is passed to the weighing hopper. As the weight of the weighing hopper is nearing to the set weight, servo slide moves slowly to provide fine feeding of the grain. As soon as the weight of the material in the weigher hopper achieves the set value, the servo gate of the storage hopper closes and the weigh hopper gate opens to discharge the set quantity of material on to a downstream process line. Micro controller registers and updates the exact quantity of material discharged. When the weigh hopper becomes empty, weigh hopper gate closes and the storage hopper servo slide opens for the next weighing cycle. The below figure shows how the process will go in the project . Firstly the the product which is to be packed must be check that in what form it is present then the product is to placed in hopper in bulk.

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MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

Figure 1.1 Flow chart of process.

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MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

CHAPTER 2 PROJECT DESCRIPTION2.1 ShutterThe shutter is made up of iron in which we have use the iron sheet and ball bearings which help in rotating the sheet according to our requirement . In this the size of the sheet is kept in such a way that it covers the mouth of hopper from the bottom . The length and breadth of sheet is kept (9x18 inches). The ball bearing which are used in it are such that when sheet is connected to the motor used it drives the shutter forward & backward movement . Fig 2.1 sow the real shutter.

Figure 2.1 Closed Shutter When the shutter moves in forward direction the path beside it left vacant which show that the process is going on . Fig. 2.2 show the ball bearing & open view of shutter.

Figure 2.2 Opened Shutter

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MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

2.2 HopperA hopper is a large pyramidal shaped container used in industrial processes to hold particulate matter that has been collected from expelled air. Hoppers are usually installed in groups to allow for greater collection quantity. They are employed in industrial processes that utilize air pollution control devices such as dust collectors, electrostatic precipitators, and bag houses/fabric filters. Steel is the typical material of choice for hopper construction . Hopper walls are insulated in order to protect the outside environment and personnel from the discarded contents. Oftentimes, the bottom - 1/3 of the container is heated to eliminate the possibility of condensation inside the hopper. The greatest difficulty associated with the removal of dust from the hopper is the compaction of the ash. Moisture content, particle shape and size, and vibration are all factors that contribute to the compaction. Typically vibrators are installed on the outer walls of a hopper to shake and release the dust.

Figure 2.3 Hopper

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MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

2.3 LCD interfacing with Load CellThe circuit shown below is of an 8051 based bi directional motor whose direction can be controlled using 2 push button switches. The circuit is very similar to the previous one except for the two push button switches . These pushbutton switches are interfaced to P0rt 3 of the microcontroller. Resistors R2 and R3 are the pull down resistors for P3.0 and 3.1 respectively. The code for the above project is so written that initially when power is switched ON, the motor remains OFF. When push button switch S2 is pressed P1.0 goes high and P1.1 remains low. The motor runs in the clockwise direction and this condition is maintained until S3 is pressed. When push button switch S3 is pressed the logic of P1.0 and P1.1 toggles making the motor to run in the opposite direction and this condition is maintained until the next press of S2.

Figure 2..4 Interfacing of LCD with DC Motor

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MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

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MINOR PROJECT REPORT

AUTOMATIC WEIGHING AND PACKAGING MACHINE

CHAPTER 3 COMPONENTS DETAILS3.1 LOAD CELL The heart of any weighing system is the load cell. Whilst they are not exciting to watch, load cells are highly accurate transducer which provides the user with information not generally obtainable by other technology due to commercial factors. Load cells are designed to sense force or weight under a wide range of adverse conditions; they are not only the most essential part of an electronic weighing system, but also the most vulnerable. In order to get the most benefit from the load cell, the user must have a thorough understanding of the technology, construction and operation of this unique device. In addition, it is imperative that the user selects the correct load cell for the application and provides the necessary care for the load cell during its lifetime. Understanding these important issues and properly maintaining the load cells will ensure trouble free weighing for a long period of time.

3.1.1 Origin of load cell The sensing or spring element is the main structural component of the load cell. The element is designed in such a way that it develops a strain, directly proportional to the load applied. Sensing elements are normally made of high strength alloy steels (nickel plated for environmental protection), precipitation - hardened stainless steels, heat treated aluminium alloys, or beryllium copper alloys. By bonding strain gages to a precisely machined element, the force applied can be identified in terms of resistance change. The strain gages, usually four or a multiple of four, are connected into a Wheatstone bridge configuration in order to convert the very small change in resistance into a usable electrical signal. Passive components such as resistors and temperature depending wires are used to compensate and calibrate the bridge output signal.

DEPARTMENT OF ELECTR