Enhancement of conventional baby diaper making machine process using Programmable Logic Controller
K.Balasubramanian, R.Jeyakumar, R.Ramamoorthi, R.Sivasubramanian and N.Ramachandran
Department of Mechanical Engineering
Sri Krishna College of Engineering and Technology, Coimbatore, TamilNadu, India [email protected]
Abstract- The usage of baby diaper increasing tremendously day by day. In order to capture the market, the cost of the diaper should be reduced. The production cost is important to reduce the cost of the diaper. The main disadvantage of using conventional machine is less productivity. In order to improve the productivity the conventional machine should be modified. The main objective of this work is that to materialized the idea of automating the diaper making machine which in turn increase the productivity and quality of the diaper. Some of the additional stages are added to the machine which uniquely perform certain functions like sealing, stitching helps the machine to produce a diaper which is in par with the current diaper available in the market in terms of shape and quality. In the present paper discuss the design of programme logic control (PLC) based automated baby diaper making machine. Ultimately, this improves the quality of the diaper and the productivity of the machine.
Keywords – baby diaper, PLC, diaper making machine, productivity I.INTRODUCTION
The diaper is a sponge like piece of clothing so that the children can wear as they are incapable of bladder control or bowel movement. The users also include elders those who with physical or mental disability. Sometimes, it is also common for the people who working in extreme conditions like astronauts. The diapers can be made with cloth or disposable materials. Cloth diapers composed of layers of fabrics as micro fibers and can be washed and reused multiple times. Disposable diapers contains absorbent chemicals and thrown away after use. Disposable diapers are most widely. Most disposable diapers consist of three sheets (Fig. 1), each having particular functions designed to impart utmost comfort to users. The top sheet of diaper is a soft porous nonwoven fabric which will be in contact with the baby’s skin directly. Hence, it is designed in such way that it transfers urine to the next layer called absorbent layer and hence the top sheet remains dry. The properties of various nonwoven superabsorbent core fabrics used in disposable diapers discussed by different authors (1-10).
Fig.1 Structure of modern disposable diapers [11]
The usage of baby diapers globally indicates that one child uses about 4 to 5 diapers per day - thus a typical child will use about 4100 disposable diapers a year [12]. Hence, automatically there will a very high competitive market of baby diapers. Consequently, one has to reduce the cost of the diaper in order to capture a market place. The costs involved for manufacturing diaper are raw material cost, machine cost, manpower cost, energy and infrastructure.
Apart from raw material cost, the machine performance in terms of quality and minimization of waste also considered. The machine technology available in the market can be classified into two types of technology,
viz, Lo-Tech and Hi-Tech (13). They have collected the data from the market and studied the two types machines based on the performance and cost of the final product and concluded that Hi-Tech machine was best compare to lo- tech machine in terms of performance, quality and cost of the diaper.
In the present work, the authors have studied the manually operated diaper machine and its disadvantages and present the design of PLC based diaper machine to overcome the disadvantages of manually operated diaper machine and productivity of the diaper making machine.
II.PROPOSED DESIGN 2.1 Existing machine and its disadvantages –
The authors have studied the various mechanisms, materials and circuits involved in the conventional diaper making machines. The extrusion rollers were used in the processes ranging from wood pulp extrusion to the final packaging of the diapers. The main disadvantages of manually operated diaper machine are (i) the amount of raw material is to fed for a single cycle of process determined manually (ii) the material feed is hand driven (iii) placing of wood pulp is also manual (iv) the quality of the seal is low because of the lack of a proper temperature control system (v) the productivity is less. Similarly, the disadvantages of industrial automated machines are (i) the initial investment is very high (ii) current consumption is relatively high (iii) maintenance is a key concern (iv) the size of the machine is too large to be accommodated in a domestic environment.
2.2.Proposed design –
First, it is decided that the conventional extrusion rollers should be replaced by roller conveyor to bring down the cost. The key idea is to feed the raw materials via main conveyor. Through the course of its path various processes, viz, loading, sealing, stitching, cutting etc., are carried out automatically. The signals for the various processes that are being done are sent from a master Programme Logic Controller (PLC) which is preprogrammed for the purpose.
The block diagram explains the overall working of the machine.
Fig.1 Block diagram of machine working
The overall working of the machine can be listed as (1) feeding of the raw materials (2) placing of the wood pulp (3) Heating and sealing (4) sewing (5) cutting (6) collection of waste materials.
2.2.1 Feeding of the raw materials
The feeding of the raw materials plays a major role in the diaper making process. The two basic raw materials that are used for the diaper are (i) polyethylene (ii) non woven fabric. The feeding of these materials is done by the following procedure. The individual layers of the raw materials are wound over separate rollers and are mounted on the machine bodies in appropriate position with the help of ball bearings or plumber blocks which give them a free rotation. The tail end of the each material is collectively connected to the main spindle of the main conveyor motor. Through the course of passage of these materials there are many rollers which facilitate the movement and compression of these raw materials (fig.2).
Poly- ethylene
Non woven
fabric
Conveyor motor Placing of
wood pulp Heating and
sealing
Stitching and cutting
Fig.2 Feeding the raw materials
2.2.2 Placing of wood pulp
The placing of the wood pulp is accomplished by a drop box and a robotic hand mechanism (Fig.3). Some of the features are given below. A drop box with appropriate clearances for placing the wood pulp in its standard dimensions is designed. This drop box at its bottom most layer has hole provision for a single wood pulp to pass through it. The robotic hand placed at the rear end of the drop box pushes the wood pulp and places it appropriately in its position.
The signal for the hand is sent on the system timing and other processes to be carried out.
Fig.3 Placing of wood pulp 2.2.3 Heat sealing and profile cutting
This process is primarily implemented to bring all the three layers of the product in to single coherent layer so that it facilitates the further processing. A part of the profile it cut in this section so that the remaining part facilitates the connection of the piece with the main raw material. The heat sealing is done at a pre tested appropriate temperature approximately 150.2°C. The temperature at which the non woven materials melt and forming a bond between the polyethylene layers (fig.4).
Fig.4 Heat sealing and profile cutting
2.2.4 Sewing (Lycra stitching)
The stitching of Lycra thread is brought it here in order to bring the shape of the diaper to a standard shape. This feature is added to make the diaper shrink longitudinally and have a cup shaped structure so that it remains to the body of the child as close as possible and prevents leakage. This ultimately increases the quality of the product. The stitching which was done already manually is been implanted automatically. Ordinary over loop stitching machine is used to carry out the stitching process. The motorized sewing machine is used so that the pulses can be given to the motor from the PLC according to the timing cycle of the process. The implementation of the presser bar lifter is accomplished with the help of a piston cylinder arrangement which lifts the presser foot according to the pulses it receive. This mechanism is implemented to avoid continuous stitching and excess material wastage. When the piston cylinder is given a pulse it lifts the presser foot and then so that the conveyor moves and then the stitch for the next unit starts. In the intermediate gap there is no stitching and there is a free moving of the material.
2.2.5 Cutting
This process is done so that the longitudinal ends are cut from the raw materials and so that each unit is separated (fig.5). This is done with the help of a die with two cutters and a optimal amount of temperature to cut the Lycra attached to the piece. At the end of this process each product gets separated from the parent raw material and gets collected in the collector box at the bottom.
Fig.5 Cutting 2.2.6 Collection of waste materials
At the end of all the processes the remaining material containing the hole of the shape of the product will be collected.
This process facilitates the waste collection at a single place so that it does not require any manual intervention (fig.6).
Fig.6 Waster material collection
III.MACHINEMODELANDPLCPROGRAMME
The overall machine diagram was planned, designed and drafted using the software Solidworks (Fig7). The machine body will be fabricated with iron rods which are hollow square shape with blunt edges for more strength and prevention of failure. The heating will be done by single point temperature controller with a comprehensive feedback loop using a thermocouple. Controller is used because of sharp heating temperature. The heating element that is used should be coated with Teflon material so as to provide uniform heating and to prevent the top most layers from getting adhere to the heat conducting element. The material properties are read carefully for the purpose of heat sealing. At a temperature of 150.2°C all the layers melt and fuse with each other. The conventional Lycra stitching machines are closely observed for its working and same features are implemented in the normal stitching machine including the tension adjustments and the width of the stitch. The auto lifting mechanism or the presser foot lift mechanism is implemented in the course of automation with the help of separate components.
The pneumatic circuit is very important as for as automation concern. The pneumatic circuit is used for automating the baby diaper machine is shown in fig.8.
The PLC is used for automation of electromechanically processes,viz, control of machinery on factory assembly lines, amusement rides, lighting fixtures etc.,Unlike general purpose computers, the PLC is designed for multiple inputs and outputs arrangements. These connect the PLC to sensors and actuators. PLC reads limit switches, analog process variables and complex position system. On the actuator side, PLC operate electric motor, pneumatic or hydraulic cylinders, relays, solenoids etc. , PLC programs are typically written for this application on personal computer and then downloaded. The program is stored in the PLC either in battery backup RAM or non volatile flash memory. A single PLC can be programmed to replace thousands of relays. The sample ladder logic diagram for few steps of baby diaper making machine is shown in fig.9.
Fig.7 Schematic diagram of baby diaper machine
Fig.8 Pneumatic circuit for diaper making machine
Fig.9 Ladder logic diagram for diaper making machine (few steps only)
IV.CONCLUSION
Thus in the current era of automation just by using the available technologies “Baby Diaper Machine” is automated.
Hence, it increases the productivity of the product and facilitates the ease of handling of the machine. The following are the advantages of using such machine.
Easy to operate
Can install in the home itself or small area
Low maintenance and long life
Low current consumption
Make a baby diaper as quickly as possible
Incredible profit potential ACKNOWLEDGEMENT
The author would like to acknowledge the following students Mr.K.G.Venkatbalaji, Mr.R.Venkkataraman and Mr.K.Vishwas for successful completion of design part for making baby diaper making machine.
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