Method Used To Effectively Produce Nanofiber Engineering Essay

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Electro spinning is a profound method used to effectively produce nanofiber. It shrinks the polymer from a micron range to a nanometre range producing a fine fibre with many advantages properties. These nanofiber can be used in many applications, namely in filtration, textile manufacturing, composites and mainly in medical applications such as wound dressing, tissue engineering scaffolds, artificial organ components, drug delivery, implant material etc.

The nanofiber diameter can be varied by many factors such as the intensity of the electric field strength, concentration of the polymer solution, distance from needle tip to collector, collector speed in the case of a rotating collector, the nozzle diameter and flow rate. The diameter in turn affects the mechanical properties of the fibre and other properties such as the porosity.

In the use of tissue engineering scaffolds this fine fibre is very useful as it has a very high surface area to volume and surface area to mass ratio, high porosity and a small pore size and are relatively defect free.

Scaffolds are temporary artificial structures capable of supporting three-dimensional tissue formation. They serve purposes such as cell attachment and migrations, enable diffusion of vital cell nutrients, it should be biodegradable etc. The properties of the scaffold required, such as porosity, mechanical strength, elasticity etcetera depends entirely on the type of tissue that will be cultured in the scaffold and varies from type to type.

Contents

Acknowledgement

Summary

Overview of the Project

Introduction

Background

Aims and Objectives

Literature Review

Tissue Engineering

Scaffold

Electrospinning

Factors effecting Scaffold Properties

Design of the Electrospinning system

Part description and material selection

Manufacture

Conclusion

Conclusion

Recomendation

References

Introduction

Background

Tissue Engineering (TE) is a vast and emerging interdisciplinary field that caught the eye of many intellectuals and has been researched on over the past two decades but its applications are still not completely exploited. In the recent past however, an advancing amount of research is being conducted to globally revolutionize the way to ameliorate the health and quality of life of millions of people. TE combines the knowledge and technology of cells, engineering and materials methods and suitable biochemical and physic-chemical factors to create repair or replace tissues and organs using a three dimensionally shaped, degradable biomaterial scaffolds with cells and growth factors, which are however not always simultaneously used. Moreover the TE approach to treatment has an advantage of not having the limitations of the current orthodox therapies; such has having to locating donors with the same blood group. A good example of TE is manmade dermis (skin).

Scaffold is a three dimensional substrate and acts as a guide and mechanical support for tissue re-formation. Ideally they should acquire the following properties; appropriate surface chemistry and microstructures to facilitate cellular attachment, high porosity with interconnected pores, good mechanical properties (stiffness and tensile strength), biocompatibility, large surface area to volume ratio (which is much larger in the case of Nanofiber compared to Microfiber), flexibility, it should have a favourable biodegradation rate with no unfavourable by-products and also have the ability to promote extracellular matrix (ECM) secretions. It should be able to mimic the ECM in the supporting cells proliferation and organization.

Scaffolds can either be synthetic or natural. However, synthetic polymers are more commonly used as they can be custom-built to provide a broad variety of required properties and thereby being predictable. Natural polymers however are inherently capable of binding with cells much better. Hence, the type of polymer selected for the manufacture of the scaffold will depend entirely on the type of tissue that it will grow.

There are many conventional methods in which scaffolds can be fabricated, they include a number of processing techniques such as drawing [only viscoelastic materials that can undergo strong deformations can be used] , template synthesis [this method cannot make one-by-one continuous nanofiber], phase separation [time consuming], self assembly [also time consuming], Electro spinning [can fabricate fibres with controllable diameters and also produce fibres with a high surface area to volume ratio thereby this seems an attractive method that could be further developed for one-by-one mass production of nanofiber from various polymers] .

Electro spinning which was derived from the word 'electrostatic spinning' provides a simple and versatile method to shrink polymer fibre materials from micrometers to a submicron or nanometre range. It uses an electric charge to draw very fine fibres from a polymer melt or a polymer solution.

Electro spinning can be also done using a co-axial system to produce Core-Sheath Fibre. In this method, two solutions namely the core and sheath solutions which contain two different polymers are spun together. Generally a synthetic polymer is selected for the core and a natural polymer is selected for the sheath. The end result would be a sheath-core bi-component nanofiber with novel hybrid properties at the submicron level.

Aims and Objectives

This project emphasises on the development of a cost effective electro spinning system to produce nanofiber tissue engineering scaffolds.

The first phase of the project was carried out by a group of engineers to design the system followed by the material selection. During this phase extensive research was conducted on scaffold properties, Electrospinning process and the parameters in the Electrospinning process that would affect the scaffold properties, to build a solid background knowledge on what the system is supposed to do and how it should work to give the best results. Further research was extended into the types of manufacturing techniques. The second phase of the project was concentrated on the manufacturing of the system.

The objectives of the project on the whole are as follows;

Research on the Electrospinning process and the parameters that could be altered

Analyze the designed Electrospinning system carefully

Prepare a cutting list search for suppliers and order the required materials and components

Manufacture all the parts

Assemble the Electrospinning system together.

If time persists run tests on the system using polymers such as Polyethylene oxide (PEO)

The detailed design has to be completely analyzed the required parts have to be ordered and then skilfully manufactured as even a minute defect could lead to the catastrophic failure of the system.

Literature Review

Tissue Engineering

Tissue engineering TE is "a rapidly growing area that seeks to create, repair and/or replace tissues and organs by using combinations of cells, biomaterials, and/or biologically active molecules" defined by The National Institute of Biomedical Imaging and Bioengineering (NIBIB) [1] . It is the use of physical, chemical, biological, and engineering processes to control and direct the collective performance of cells. Tissue engineering was started in 1985, since then major progress has been made toward understanding, controlling and using tissue engineering technology in living organisms. This technology is likely to produce innovative products in the health care sector to save human lives from the earliest diagnostic testing to the advanced stages of therapy [2] .

TE is considered a type of biomedical engineering form to build up the environment for regeneration induction whereby the regeneration of tissue and organs are naturally induced to therapeutically treat disease by artificially accelerating the proliferation and differentiation [3] .

Tissue engineering will produces a remarkable enhancement in medical care for millions of people worldwide and simultaneously reducing the medical expenses drastically. To date the medical sector is facing many problems in organ transplants due to shortage of donor organs. Many patients die being unable to receive a transplant or waiting for the transplant, more over organ transplants come at an extraordinary cost to the patient. Further complications in organ transplants are encountered when the donor is influenced by infectious bacteria or virus such as Hepatitis or HIV. In addition there are many reported cases where the donor organ is rejected by the immune system of the recipient and the patient will have to be on medication for the rest of the life to suppress the activity of the immune system. But then again these drugs would damage the kidney and liver. Surveys show that despite all the effort and cost involved in transplanting the survival rates of these organ transplants are significantly low [4] . Having all these effects and influences in consideration the Tissue Engineering approach looks very promising. This is done by first isolating a tissue from the patient and then it is cultured and seeded onto a biomaterial scaffold, which is a sculptured porous sponge and will act as a temporary support. Then the cells attach to the scaffold and reorganize themselves by proliferation, synthesizing extracellular matrix and migrating along the scaffold to form tissue. This is grown outside the body in a bio reactor and then grafted into the patient for further growth. This technique can be used either to accelerate the repairing or replace defective or damaged tissue which could be caused by disease, injury or age. The rate of healing may vary from patient to patient depending on their individual healing potentials.

This technique decreases the cost drastically while elevating the health care properties and the quality of life on the whole.

Nanofiber Scaffolds

Tissue engineering also involves the fabrication of scaffolds to support cellular in-growth and proliferation. These scaffolds are very crucial in the field of regenerative medicine and their properties vary depending on the type of tissue being repaired or regenerated. Scaffolds usually serve at least one of the following purposes:

Allow cell attachment and migration

Deliver and retain cells and biochemical factors

Enable diffusion of vital cell nutrients and expressed products

Exert certain mechanical and biological influences to modify the behaviour of the cell phase

To achieve the goal of tissue reconstruction, scaffolds must meet some specific requirements. It should have high porosity and adequate pore size which is essential to facilitate cell seeding and diffusion throughout the whole structure of both cells and nutrients. It should be biodegradable so that scaffold will not require surgical removal once the tissue is grown and should also break down without producing any harmful by-products. The rate of biodegradability is very crucial, it should not degrade to fast which will compromise the mechanical support to the tissue and it should not be too slow such that by the time the tissue is grown it should break down leaving behind just the new tissue to take the entire load and blend in with the surrounding and be part of it

Several requirements have been identified as crucial for the production of tissue engineering scaffolds [5] : (1) the scaffold should possess interconnecting pores of appropriate scale to favour tissue integration and vascularisation, (2) be made from material with controlled biodegradability or bioresorbability so that tissue will eventually replace the scaffold, (3) have appropriate surface chemistry to favour cellular attachment, differentiation and proliferation, (4) possess adequate mechanical properties to match the intended site of implantation and handling, (5) should not induce any adverse response and, (6) be easily fabricated into a variety of shapes and sizes. Bearing these requirements in mind, several materials have been adopted or synthesised and fabricated into scaffolds [6] .

Electrospinning

Electro spinning is a process that can produces scaffolds in the form of non-woven meshes containing fibres ranging in diameter from tens of microns to tens of nanometres.For this process either natural or synthetic polymers can be used can be used. Natural polymers eliminate concerns regarding rejection for the immune system while the synthetic polymers are very advantageous as they can be tailor made to meet the required properties such as mechanical properties and rate of biodegradability [7] . Clearly, the electro spinning process can eventually be developed to achieve successful utilization in vivo on a routine basis.

Nanofiber scaffolds can be produced by conventional melt, dry, or wet spinning processes. Generally a wet solution of a polymer and solvent is pumped and the solvent evaporates leaving behind the polymer fibre to be collected or a polymer melt is extruded and subsequently drawn. These collected fibres in the form of non-woven mesh have a very large surface area to unit mass ratio and a large percentage of the volume of this mesh consists in the form of interconnected porosity7. For the generation of finer fibres, ranging from 15 nm to 10 μm or greater, electrospinning is a broadly useful technology. Electrospinning relies on the application of an electrostatic force to drive fibber formation.

Interest in the electro spinning technology was recently revived when Reneker et al. first demonstrated that a multitude of polymers could be electro spun [8] and refined the associated theory [9] . Hundreds of different natural and synthetic compositions have been electro spun into thin fibers since 1990.

The elements required for electro spinning include a polymer source, a high voltage supply, and a collector [10] . When an electric potential is applied between the polymer source and collector, charge accumulates and is forced to the surface of an emerging polymeric droplet at the end of a metal needle. In electro spinning, the force of the electric field overcomes the cohesive force of the solution, often dominated by surface tension, and an electrically charged jet of polymer-containing solution erupts. As the jet moves toward the collector plate, it is elongated by electrostatic interactions between charges on nearby segments of the same jet. Meanwhile, the solvent evaporates and finally the jet solidifies into a fiber. Typical electro spinning processes create very long fibers that can vary in diameter along the length from one half to as much as twice the average diameter. The diameter of these fibers may be considerably larger than the nanometer scale.

In general a highly viscous polymer solution or melt is placed in a syringe with a millimetre sized nozzle which is supplied by a high voltage electric supply. This is pumped using a syringe pump to form a liquid droplet. When sufficient voltage is applied to the liquid droplet it becomes charged and electrostatic repulsion counteracts the surface tension and the droplet is stretched. Increasing the intensity of the electric field further causes the hemispherical fluid at the tip of the nozzle to further elongate to form a conical shape known as a Taylor Cone. Further increasing the intensity of the electric field causes a critical point to be reached where the repulsive electrostatic force overcomes the surface tension and the charged get of fluid is ejected from the tip of the Taylor cone. The jet extends in a straight line for a certain distance, and then bends and follows a looping and spiralling path. The electrical forces stretches the charged jet to a great extent and the jet becomes very thin. The whipping process caused by electrostatic repulsion indicated at small bends in the fibre also helps in the elongation of the fibre. During the intervening time when the fluid is in flight the solvent evaporates leaving behind a charged polymer fibre and also the charge migrates to the surface of the fibre. In the case of the melt the discharged jet solidifies when it travels in air. This is then collected at the grounded or oppositely charged collector which can either be a flat tray or a cylindrical collector which would be rotated at high RPM to obtain a continuous and one-by-one nonwoven fibre.

Polymer Solution

or Melt

Or Melt

Figure 1 - Schematic drawing of the Electro spinning process [Landcuo]

Factors effecting Scaffold Properties

To investigate the effects of some of the key process parameters, electro spinning at different conditions had been conducted. The parameters studied were concentration, capillary-screen distance (C-SD), electric potential at the tip and flow rate. Fig. 2 shows the effect of capillary-screen distance (C-SD) on the fibre diameter.

Figure 2: Effect of increasing capillary-screen distance

Distinct bead like structures can be seen. It can also be seen that with increasing capillary-screen distance (C-SD), the average fiber diameter decreases. This is true for fibers spun at different concentrations, electric potentials and flow rates. Fig. 3 shows the FESEM pictures of the fiber.

Figure 3: Effect of increasing capillary-screen distance on the fibre. The average diameter of fibers decreases with increasing capillary-screen distance.

Comparing Figures 2  & 3, it can be inferred that the bead like structure is predominant at lower concentrations. With increasing concentration of the polymer solution (keeping other parameters constant) the average fiber diameter increases. Again, with increasing capillary-screen distance (C-SD) the average fiber diameter decreases. Similar trends were observed at higher concentrations. At lower capillary-screen distances, blobs are observed that should not be mistaken as beads. Fig. 4 shows FESEM micrographs of 25-wt % Estane (in DMAc) that were electro spun at 10 kV & 3ml/h.

Figure 4: Effect of increasing capillary-screen distance

A noticeable feature that shows up is the marked Fracture points. This results due the solution being too viscous that it resists any deformation during the whipping process and breaks, instead of undergoing drawing. These Fracture points were also observed in fibers electro spun at higher flow rates. At high concentrations and flow rates a broad distribution of fiber diameter was observed. With increasing electric potential (keeping other parameters constant) the fiber diameter decreases as is shown in Fig. 5.

Figure 5: effect of fiber diameter on increasing the electric potential.

With increasing electric potential, the polymer jet is discharged with a greater electrostatic repulsion that causes it to undergo higher levels of drawing stress. This results in the decrease of the fiber diameter. However, at higher electric potential the fiber diameter distribution becomes increasing broader. Hence the control of the process at high electric potential, flow rate & concentration becomes increasingly difficult.  Fig. 6 summarizes the effects of the different process parameters.

Figure 6: Effect of process parameter on fiber diameter, produced by Electro spinning

Design of the Electrospinning system

There are many types of Electrospinning systems such as, Multi Jet Electrospinning [11] system where jets are formed from two or more nozzles or systems that produce a Core-Sheath fibre this is when two solutions ideally a natural polymer for the outer sheath and a synthetic polymer for the core are electrospun together. These systems are very complex and due to its complex nature may be expensive to manufacture. Therefore, this system was designed to be simple and hence was more cost effective.

The system was designed such that the important parameters that would alter the scaffold properties could be adjusted. And it was dimensioned such that the entire system can be placed into the safety cabinet in the engineering research lab. Thus ensuring the safety since it uses a very high voltage. The novel design is shown below in figure??

System specification

Voltage Supply

Power = 50 W

Input voltage = 220/240 V

Output voltage ≈ 7 kV

Motor

Speed = 2200 rpm

Shaft size =2.3 mm

Idle / Max current = 0.4 A/ 9A

Syringe Pump

Max No. Of Syringes = 1

Linear Force = 9kg

Min / Max Step Rate = 1 step per 30s / 400 steps per second

Part Description and material selection

Cabinet

The cabinet encloses the entire system and the Electrospinning process takes place inside the cabinet. The cabinet also control the ambient conditions. This is important since for an example, if there are strong winds the Nanofiber mesh won't be collected on the collector as required.

The cabinet has to be manufactured such that its door can be opened and closed with ease. And it should be locked and kept in place when closed. The cabinet has two rollers on either side of the cabinet so that the tray can slide in and out smoothly. The rubber stoppers on the cabinet door would act as mounts and support the tray when it is pulled out. It would also act as a damper to reduce vibrations.

Material: Polycarbonate

Lock

Rollers

Rubber Stoppers

Tray

All the parts in the system are mounted to the tray and can slide into and out of the cabinet. The tray is pulled out of the cabinet to make adjustment to the system or to collect the Nanofiber scaffold so that there would be no need to reach in and make adjustments in a tight constrain of space. Holes are drilled into the tray to mount the parts and components and also to pass electrical wires, so that the Electrospinning process won't be disturbed.

Material: Polycarbonate

Holes

Shape to support rollers

Test Stand and platform

The needle tip is rested in the notch on the platform. The platform could be adjusted up and down the test stand with the help of the platform screw as shown in figure ?? below. This will vary the distance between the collector and the needle tip. So the required screen to capillary distance could be obtained by just adjusting the platform.

The Test stand is made in two parts, the lower plate and the rod and they are connected using a screw.

Material: Platform / Test Stand - Cast Iron

Platform screw

Platform

Needle Tip

Test Stand

Needle Tip

It is a capillary with a small diameter. A high voltage electric potential is connected to the tip which is required for the Electrospinning process. The end of the tip is insulated so that the test stand and the platform do not conduct. To obtain this shape of the needle tip, as shown in figure the needle is carefully bent without being damaged.

Material: Stainless Steel

Collectors

The system can accommodate two types of collectors a flat plate and cylindrical collector as shown in figure ?? below. Depending on the requirements on the type of scaffolds produced either one could be used. Both the collectors can be removed from the holder after the Electrospinning process to remove the Nanofiber mesh. The cylindrical collector is connected to a motor. The rotational speed of the collector can be varied using the motor control unit to the desired speed for the process. One terminal of the high voltage supply is connected to the cylindrical collector. So the produces fibre will get attracted to the oppositely charged collector and hence will be channelled to the collector and can be collected.

Material: Flat Plate - Aluminium

Cylindrical - Brass / Nylon

Collector holder

The collector holder is manufactured so that it has a grove in which the flat plate collector can slide into place and a hole in which the cylindrical collector can be set in place.

Material: Aluminium

Motor and motor Holder

The motor is connected to the cylindrical collector at one end and it is controlled by a control module so that the speed of the collector can be varied. The speed can be varied to change the diameter of the Nanofiber produced. The motor is held in place by the upper and lower motor holders.

Material: Holder - Aluminium

Syringe pump

The syringe pump will pump the polymer solution at a constant and controlled rate to the needle tip via a connecting tube; the rate depends on the type of fibre produced.

Voltage Supply

A step up voltage supply is used to produce a very high electric potential between the collector and the needle tip usually up to about 7 kV.

Development of the Electro spinning System

The development of this system involves mainly machining.

Through machining unwanted or surplus materials is discarded in order to get a desired shape. This process is carried out usually using a cutting tool, and usually using a power-driven machine. Other than making a component from a stock material, machining is used as a secondary procedure to give shape and to give a level of precision to a manufactured component. The secondary procedure cannot be attained if not by machining. It is also important to note that some machining processes have shape restrictions.

The traditional machining operations comprise of the following;

Turning- In this operation a workpiece is rotated as a primary method of moving metal against the cutting tool.

The principal machine tool used- Lathes

Milling - However in this operations the cutting tool rotates at high rpm, the cutting edges come in contact against the workpiece when the workpiece is moved towards the cutting tool.

The principal machine tool used- Milling machine.

Drilling- A rotating cutter with cutting edges are brought at the lower limit which comes in contact with the workpiece to either produce holes or be refined.

The principal machine tool used- Drill press but sometimes on lathes or mills.

Other conventional machining operations include shaping, planning, broaching and sawing. Machining is also contained by grinding and similar abrasive operations.

Turning

Turning can be defined as the machining of an external surface while the workpiece is rotating to produce cylindrical parts. There is a single-point cutting tool which is fed parallel to the axis of the workpiece at a distance that will remove the outer surface of the workpiece.

Adjustable cutting factors in turning

The factors that would affect the end product of the workpiece in a basic turning operation are type of material and type of tool, speed, feed and depth of cut et cetera. The latter three factors (namely speed, feed, and depth of cut) can be controlled by the operator to give desired output the operator does not have much preference. Although speed, feed, and depth of cut are the three primary factors it is important to note that the other factors also have a large influence.

The three primary factors of turning operation:

Speed- This factor is always referred to the spindle and the workpiece. It is important for the operator to remember that when 'speed' is stated in revolutions per minute (rpm) it refers to their rotating speed. At the same time, in particular turning operation, the important factor is the surface speed, or the speed at which the workpiece material is moving past the cutting tool. Surface speed (surface feet per minute, sfpm) is referred to the workpiece and basically is the product of the rotating speed times the circumference (in feet) of the workpiece and this calculation has to be done before the cut is started. Surface speed for every different diameter of the workpiece has to be calculated separately as they will have a different cutting speed, even though the rotating speed remains the same

Feed- This factor is always referred to the cutting tool. Feed is the rate of progresses of the tool along the path at which it is being cut. On most power-fed lathes, the federate is directly related to the spindle speed. Thus is expressed as inches per revolution (ipr) where the inches is of tool advance and the revolution is of the spindle.

Depth of Cut- This factor is basically self explanatory. As the layer is being removed from the workpiece, the diameter of the workpiece is reduced by twice the depth of cut. Measurements such as the distance from the uncut surface of the work to the cut surface or the thickness of the layer being removed from the workpiece can be measured using vinier calliper or electronic moniter of the machine.

LATHE RELATED OPERATIONS

Boring- Imagine you have workpiece with a hole; either drilled, result of core casting, et cetera and you wish to increase the diameter of the hole, well this is where the term boring comes in. Like the title says, It is done in a lathe, the workpeice is held in a face plate or chuck. Holes may be bored straight, tapered, or to irregular contours.

As concentricity is an important characteristic of bored holes the advantage of boring is that if eccentricity occurs while drilling a hole on a workpiece and the drill drifted off the center line, boring that workpiece will make the concentric with the axis of rotation of the workpiece. Therefore boring can be concluded to be internal turning while the tool is parallel to the rotation axis of work piece.

Facing- Facing is the fabrication which produced a flat surface as a result of a tool's being fed at the end of the rotating piece.

Unless the work is held on a mandrel, if both ends of the work are to be faced, it must be turned end for end after the first end is completed and the facing operation repeated. The cutting speed should be determined from the largest diameter of the surface to be faced. Facing may be done either from the outside inward or from the center outward. In either case, the point of the tool must be set exactly at the height of the center of rotation. Because the cutting force tends to push the tool away from the work, it is usually desirable to clamp the carriage to the lathe bed during each facing cut to prevent it from moving slightly and thus producing a surface that is not flat. In the facing of casting or other materials that have a hard surface, the depth of the first cut should be sufficient to penetrate the hard material to avoid excessive tool wear

Parting- With the help of a cut-off tool a section of the workpiece can be detached and this operation is known as Parting. The tool should be set exactly at the height of the axis of rotation, be kept sharp, have proper clearance angles, and be fed into the workpiece at a proper and uniform feed rate.

Threading. Nowdays this can be produced by other method but lathes provides the most adaptive and essentially simple procedure of threading. It is also the first machine that could be used for cutting threads. Therefore they are used for this job specially, when the workpiece's nonstandard size or configuration does not allow them to be made at a low price.As thread cutting is a form-cutting operation, for a lathe machine. To do threading two basic requirements must be fulfilled; accurately shaped and properly mounted tool. The shape of the tool and its position relative to the workpiece results in the thread profile.

The next condition is that the tool must move longitudinally in a specific relationship to the rotation of the workpiece. This movement is assembled through the use of the lead screw and the split unit, which provides positive motion of the carriage relative to the rotation of the spindle.

Milling

The machine for holding the workpiece, rotating the cutter, and feeding it is known as the Milling machine. In Milling, materials are cut away and the workpiece is fed past a rotating multiple tooth cutter. The cutting action of the many teeth around the milling cutter provides a fast method of machining. The end result may be flat, angular, or curved

Peripheral Milling-

In the case of peripheral milling, the 'milled surface' is generated by teeth situated on the periphery of the cutter body. Also that the cutter rotation axis is generally in a plane, parallel to the workpeice's surface that is to be machined.

Face Milling

Face milling, is done by first choosing a workpeice. Next the cutter is mounted on a spindle having an axis of rotation perpendicular to the workpiece surface. The milled surface results from the action of cutting edges located on the periphery and face of the cutter.

End Milling

In this type of milling the cutter rotates on an axis vertical to the workpiece. It can be tilted to machine tapered surfaces. Note that cutting teeth are situated on both the periphery of the cutter body and the end face of the cutter.

METHODS OF MILLING

Up Milling

Up milling or conventional milling is when the direction of the cutter rotation opposes the feed motion. For example, if the cutter rotates clockwise , the workpiece is fed to the right in up milling.

Down Milling

Like-wise, down milling or climb milling is when the direction of feed motion is the same as cutter rotation. For example, if the cutter rotates counter clockwise , the workpiece is fed to the right in down milling.

It can be concluded that the chip formation in down milling and up milling are opposites. As the cutter tool mills, the full chip thickness it starts decreasing.

Preliminary work done

The first twelve weeks was spent on researching the past and current work carried out on electro spinning to have a better understanding and knowledge on the electro spinning process and the factors that influence the fibre produce by electro spinning such as the voltage applied, distance between the nozzle and collector, viscosity of the solution or melt, surface tension and flow rate.

Secondly the design process of the electro spinning system conducted by the group was closely observed to have a thorough understanding on the working principles of the system.

Thirdly a study on the manufacturing processes such as turning, milling and drilling was conducted to be able to manufacture the electro spinning system with ease and with a good precision. The designed system will have to be manufactured by me the following semester. The resulting fibres that I will have to produce by electro spinning will be directly influenced by the accuracy of the manufacture. Hence, this part is very crucial in the project.

Conclusion

The work done this semester was entirely research based in order to obtain a better understanding on the project. The research conducted was summarised above. All the work done this semester and the plan for the work in the future is described in detail below.

Plan of attack

The first step is to build up a sound background study in Tissue Engineering. Then moving into detail, the area of scaffolds and then the electro spinning process required to fabricate the tissue engineering scaffold. With a good understanding in the subject I was able to analyse the design of the novel electro spinning system by my design group. I was able to grasp all their progress during weekly meetings. This gave me a good outlook of the system that I have to fabricate. Then obtain the cutting list for the design group and order the parts required with the help of the staff in the workshop. Once the parts have arrived the machining process of the system can be started manufacturing the system part by part. Then all the machined parts and a few pre fabricated ordered part will all be put together to assemble the system. Then test the system to check if it is functional and then fine tune it to obtain the required results. Finally if time permits manufacture scaffolds and run a few basic tests on its mechanical properties. The table below list the work plan in detail with the time stamps.

Work plan for spring semester

The proposed work plan for the next semester is given below. Regular supervisor meeting will be an integral part of the project throughout the next semester. Keeping all the records in the log book will be continued further and a weekly progress of the project will be presented to the tutor.

Week

Date

Proposed work

1

25th Jan - 30th Jan

Order parts required

 

 

2

1st Feb - 5th Feb

Check received parts and start manufacturing

 

 

3

8th Feb - 12th March

Machining

 

 

5

15th March - 19th March

Complete all machining and assembled system

 

 

7

22nd March - 31st March

Finalize system and test

 

 

8

1st April - 2nd April

Compiling all data

 

 

9

5th April - 9th April

Finalizing project

 

 

Running final test on system

 

 

11

12th April - 16th April

preparing for the final presentation

 

 

preparing final report

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