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ABSTRACT:
Automation is the rage of the engineering world. The cutting of vegetables is one of the time consuming task in our day to day life. In order to overcome the difficulty, automation in cutting vegetables has been introduced which involves the pneumatics and the power consumption is negligible. Neglecting manpower and manual effort, pneumatic vegetable cutting machine has been invented which solely becomes an extra-ordinary alternative to the existing manual model. It involves a pneumatic cylinder powered with a solenoid valve with the help of high pressure obtained from the compressor which is being converted into the reciprocating motion. The piston in the pneumatic cylinder is connected with the ram which in turn reciprocates to cut the vegetables with the help of blades connected at the bottom. Thus this involves no power consumption and human effort, thereby eliminating the limitations of the existing model.
INTRODUCTION
1.1 GENERAL INTRODUCTION:
In the late 90’s, automation was the rage of the engineering world. The best of the minds, rallied day and night to bring forth improvements of significant magnitude, something which could make an impact in the day-to-day life. Today, its’ a plethora of fields which have embraced with automation, from manufacturing to food processing, biomedical and pharmaceutical industries. In such a scenario, domestic applications have also been developed with the common man in mind. Of late, processes which were manual before are slowly being converted to semi-automated and automated nature. Manual cutting of vegetables is still prevalent, in hostels and educational institutions, marriage catering services and even in restaurants, which can cater to a whole set of varying customer tastes and preferences. The amount of vegetables to be cut for the dishes always remains higher than actually what’s consumed. The associated difficulties like time constraint, contamination, etc. make it pretty difficult for any person handling the job. Therein, arose a need to automate the process of vegetable cutting, and here we are with a proposal which can aid in easing the load off the people associated with it.
A machine or device for chopping vegetables and fruits that is to be used directly or canned. Some vegetable cutters are designed for the use in the home. Commercial vegetable cutters are used by the restaurants and in food industries. The simplest type of vegetable cutter consists of a metal screen with blades and two handles. A more complex type is designed not only for cutting but also for shredding, grating and juicing. In such a device, interchangeable (usually disc) blades are attached to a shaft that is turned manually.
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1.2 EXISTING VEGETABLE CUTTER AND ITS DEMERITS:
The manual vegetable cutter is the one which is currently available in the market. The cutter operates on the concept of ‘rotating grid’, wherein, the cutting grid is rotating inside a casing, powered by man. The vegetables are fed through the hopper arrangement, at the top. The cutting grid rotates at a high manual power which cuts the vegetables as they pass through them. The cutting grids are varied according to the need of the customer. The shapes of the cut vegetable vary with the change in cutting grids. The above mentioned cutter has some demerits regarding to its operation. First of all, the vegetable feeding is not automatic, and a person has to devote his time to feed the vegetable one by one, till the required quantity is cut. The cutter is approximately priced at a range of Rs.2500, inclusive of shipping cost and taxes. It is a manual one, for those who run a mid-level catering business. Therefore, considering all these demerits, an idea for a pneumatics powered cutter is conceived.
Some of the key problems, which were identified for the initiation of this work, are manual power of the existing automated system, additional labour, time consumption in manual cutting and chances of contamination in manual cutting.
GENERAL PRECAUTIONS:
• The vegetable cutter must only be used by trained personnel, who are perfectly familiar with the safety regulations contained in this manual.
• Provide timely trainee personnel that may have to be in the vicinity of the machine.
• Even though the machine is equipped with safety devices, avoid putting ones hand close to the moving parts.
• When intervening for the cleaning or maintenance of the Vegetable cutter (and thus the protective devices are removed), carefully evaluate the degree of risk involved.
• During the cleaning or maintenance, maintain ones concentration on the operation being performed.
• Do not use the Vegetable cutter for frozen products, meat and fish with bones and any non-food products.
• Do not intervene directly in repairing the machine, but call an authorized technician. - Always use the press with pestle to cut the merchandise
• To avoid any kind of problem, do not overfill the conductor and do not press too hard.
“Design and development of vegetable cutting machine”:
The investigation on the existing vegetable cutting machine reviews the following drawbacks such as the contamination, additional manpower and time consumption caused by manual processing. The setup involves a rotating grid, and has a reciprocator motion along casing, while the cutting grid remains fixed. The entry of vegetable into the grid apparatus is controlled by using a manual. The vegetables are fed directly. A tray is placed at the bottom of the apparatus to collect the vegetable pieces after processing. The intricacy involved with such a system is the type of vegetables it can process. The system is advantageous in the fact that existing is a manual one, and the manual power is high. The proposed work is benefitted by pneumatic power, which is abundant.
2. Subrata Talapatra, Md. Shakil, Pritom Kumar Mondal, Md. Saiful Islam
“Implementation of Tools for the Development of a Vegetable Chopper”:
In the era of industrialization, automatic machines become an integral part of human life. These machines help to reduce the time needed to do a specific task. Nowadays, human life becomes more competitive and faster than the previous. Slicing vegetables are a risky and time-consuming task in our busy life. This project is aimed at solving above stated problems by introducing a special product named Vegetable Chopper. This chopper is mainly designed to reduce human effort and make the job of chopping vegetables much easier and faster.
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Its main features are fully automated, portable, less power consumption and changeable stainless steel sharp blades, etc. This product is designed and established by following a structured product design process and with the help of a board of design engineers. Finally, this paper also suggests various techniques and opportunities of product planning in manufacturing industries as future recommendations.
3. Odior, A. O.
“Development of a Meat Slicing Machine Using Locally Sourced Materials”:
In an attempt to facilitate the processing of meat which is a daily nutritional food requirement of man, a meat slicing machine has been developed. The machine consists of a cutting blade, a meat feeder, a meat tray, a meat clamp, the crank mechanism and a control unit. The machine was designed to enhance the hygienic slicing of meat for both domestic and commercial consumption and it can accommodate from one to six cutting blades which are spaced 6.5mm from each other to give a meat slice thickness of 5mm per slice. It takes an average of 4 seconds to cut a slice and one hour for 2.673 tonnes.
4. C.P.N. Awili; B. V. Omidiji and I. I. Awili
“Design of manual vegetable slicing machine”:
A vegetable slicing machine was designed and constructed. It can be powered manually which takes care of power failure problems, and can be used in rural area where there is no electricity supply. The vegetable is fed into the machine through the hopper made of aluminium sheet to the slicing drum which carries slicing blades made of stainless steel. The chute constructed of stainless steel accepts the sliced vegetable and released it out with the aid of gravitational force. The result obtained shared that the rotating speed has significant effects
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on the slicing capacity, slicing efficiency, and sliced vegetable geometry. The higher the rotating speed, the higher the slicing capacity and the lower the slicing efficiency.
5. Nikhil S Raut, Ashwin Mahindrakar
“Review on solar food cutter with shaft mounted speed reducer for agricultural field application”:
Indian agriculture has a lot of dependency on farm labour for many kinds of operation. The main products of the farm are needed to be harvested. Now-a-days the cutting of fruits; flowers and vegetables are done by snips. Hence the main purpose now-a-days is to reduce the labour hours. For this purpose the development of the cutter and then the shaft mounted speed reducer gear box is to be done. After development of cutter, the stress developed at the cutting edge and force acting on entire linkage will be measured.
COMPONENT DETAILS:
The components used for constructing the pneumatic vegetable cutting machine are detailed along with its specifications as follows,
3.1. Container
3.2. Pneumatic cylinders
3.3. Solenoid valve
3.4. Hoses and Connectors
3.5. Cutting blades
3.6. Square plate
3.7. Frame
3.8. Collecting tray
3.1. CONTAINER:
The safe storage of food for home use should strictly adhere to guidelines set out by reliable sources, such as the United States Department of Agriculture. These guidelines have been thoroughly researched by scientists to determine the best methods for reducing the real threat of food poisoning from unsafe food storage. It is also important to maintain proper kitchen hygiene, to reduce risks of bacteria or virus growth and food poisoning. The common food poisoning include Listeriosis, Myctoxicosis, Salmonellosis, E.coli, Staphylococcal food poisoning and Botulism. There are many other organisms that can also cause food poisoning. There are also safety guidelines available for the correct
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methods of home canning of food. For example, there are specific boiling times that apply depending upon whether pressure canning or water bath canning is being used in the process. These safety guidelines are intended to reduce the growth of mould and bacteria and the threat of potentially-fatal food poisoning.
The container is a storage equipment which is attached in the overall setup for housing the vegetables for cutting operations. It’s a square shaped column which rests the pressure plate arrangement from the activation of pneumatic cylinder along the cutting blades. It provides guide path to the plate for providing pressure inside the container in order to force the vegetables or the content inside the container against the blade in order to motivate the cutting operations.
3.1.1. THE SPECIFICATIONS OF THE CONTAINER:
Length of the container - 150 to 200 mm
Breadth of the container - 150 to 200 mm
Height of the container - 200 to 250 mm
Carrying capacity of the container - 0.5 to 1 kg
Material - Mild steel plates
Thickness of the walls - 2 to 5 mm
3.2. PNEUMATIC CYLINDER:
Cylinder is a device which converts fluid power into liner mechanical force and motion. These cylinders are widely used in industrial pneumatic systems. These cylinders are also called as linear motors and reciprocating motors pneumatic cylinders are designed for a variety of services. Pneumatic 8
cylinders transforms the flow of pressured fluid into a push or pull of the piston rod since out system uses double acting cylinders we shall see some details about them.
Double acting cylinders are in one in which fluid force can be applied to the movable element in two directories. The force exerted by the compressed air moves the piston in two directories in a double acting cylinder. They are used particularly. The piston is required to perform work not only on the advance movement but also on the return. In principle, the stroke length is unlimited, although bucking and bending must be considered before we select a particular size of piston diameter, rod length and stroke length.
The main component of any pneumatic system is the cylinder, which receivers air under pressure and the pressurized air helps to move the piston to and fro.
The amount of air delivered into the cylinder into the cylinder decides the rate of doing work. A cylinder is a hollow circular section with the top and bottom flange provided to prevent the leakage of air.
The compressed air is used to actuate the piston. In order to move the piston to and fro, the air is supplied to the top and bottom of the cylinder alternatively.
Cylinder is mainly classified into two types namely,
Single acting cylinder.
Double acting cylinder.
In single acting cylinder, using the spring provided around the piston rod attains the return stroke, but it is not efficient. So, the double acting cylinder is used in which the return stroke is attained using compressed air.
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3.2.1. DOUBLE ACTING CYLINDER:
In this the force exerted by the compressed air moves the piston in two directions. They are used partially when the piston is required to perform work not only on the advance movement but also on the return stroke. This principle, the stroke length is unlimited, although bucking and bending must be considered before selecting the particular size of piston diameter, rod length and stroke length.
3.2.1.1. SPECIFACTIONS OF DOUBLE ACTING PNEUMATIC CYLINDER:
• Stroke length : Cylinder stoker length 160 mm = 0.16 m
• Quantity : 1
• Seals : Nitride (Buna-N) Elastomer
• End cones : Cast iron
• Piston : EN – 8
• Medium : Air
• Temperature : 0-80 º C
• Pressure Range : 8 N/m².
3.2.2. PNEUMATIC CYLINDER DESIGN:
3.2.2.1 Design of Piston rod:
Load due to air Pressure.
Diameter of the Piston (d) = 40 mm
Pressure acting (p) = 6 kgf/cm²
= 6 ×0.981
= 5.886 bar = 0.5886N/mm2
Material used for rod = C 45
(Data book page no 1.12)
Yield stress (σy) = 36 kgf/mm²
= 36×98.1
= 3531.6 bar
= 353.16N/mm2
Factor of safety = 2(data book page.no 8.19)
Force acting on the rod (F) = Pressure x Area
= p x (Πd² / 4)
= 0.5886 x {(Π x 40² ) / 4 }
F = 739.6 N
Design Stress (σy) = σy / F0 S
= 353.16 / 2 = 176.5N/mm2
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∴d = √4F/π [σy]
= √ (4×739.6)/ π[176.5]
∴ Minimum diameter of rod required for the load = 2.3 mm
We assume diameter of the rod = 15 mm
3.2.2.2 Length of piston rod:
Approach stroke = 160 mm
Length of threads = 2 x 10 = 20mm
Extra length due to front cover = 12 mm
Extra length of accommodate head = 20 mm
Total length of the piston rod = 160 + 20 + 12 + 20
= 212 mm
By standardizing, length of the piston rod = 210 mm.
Material removal rate = 0.25 kg/sec (according to loading)
3.3 SOLENOID VALVE:
The directional valve is one of the important parts of a pneumatic system. Commonly known as DCV, this valve is used to control the direction of air flow in the pneumatic system. The directional valve does this by changing the position of its internal movable parts.
This valve was selected for speedy operation and to reduce the manual effort and also for the modification of the machine into automatic machine by means of using a solenoid valve. A solenoid is an electrical device that converts electrical energy into straight line motion and force.
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Solenoids may be push type or pull type. The push type solenoid is one in which the plunger is pushed when the solenoid is energized electrically. The pull type solenoid is one in which the plunger is pulled when the solenoid is energized. The name of the parts of the solenoid should be learned so that they can be recognized when called upon to make repairs, to do service work or to install them.
3.3.1 SUMMARY OF SOLENOID VALVES:
A Solenoid valve is a mechanically operated valve. The valve is controlled by a mechanical through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold.
Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.
There are many valve design variations. Ordinary valves can have many ports and fluid paths. A 2-way valve, for example, has 2 ports; if the valve is open, then the two ports are connected and fluid may flow between the ports; if the valve is closed, then ports are isolated. If the valve is open when the solenoid is not energized, then the valve is termed normally open (N.O.). Similarly, if the valve is closed when the solenoid is not energized, then the valve is termed normally closed. There are also 3-way and more complicated designs. A 3-way valve has 3 ports; it connects one port to either of the two other ports (typically a supply port and an exhaust port).
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Solenoid valves are also characterized by how they operate. A small solenoid can generate a limited force. If that force is sufficient to open and close the valve, then a direct acting solenoid valve is possible. An approximate relationship between the required solenoid force Fs, the fluid pressure P, and the orifice area A for a direct acting solenoid value is:
Where d is the orifice diameter. A typical solenoid force might be 15 N (3.4 lbf). An application might be a low pressure (e.g., 10 psi (69 kPa)) gas with a small orifice diameter (e.g., 3⁄8 in (9.5 mm) for an orifice area of 0.11 in2 (7.1×10−5 m2) and approximate force of 1.1 lbf (4.9 N)).
When high pressures and large orifices are encountered, then high forces are required. To generate those forces, an internally piloted solenoid valve design may be possible. In such a design, the line pressure is used to generate the high valve forces; a small solenoid controls how the line pressure is used. Internally piloted valves are used in dishwashers and irrigation systems where the fluid is water, the pressure might be 80 pounds per square inch (550 kPa) and the orifice diameter might be 3⁄4 in (19 mm).
In some solenoid valves the solenoid acts directly on the main valve. Others use a small, complete solenoid valve, known as a pilot, to actuate a larger valve. While the second type is actually a solenoid valve combined with a pneumatically actuated valve, they are sold and packaged as a single unit referred to as a solenoid valve. Piloted valves require much less power to control, but they are noticeably slower. Piloted solenoids usually need full power at all times to open and stay open, where a direct acting solenoid may
only need full power for a short period of time to open it, and only low power to hold it.
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A direct acting solenoid valve typically operates in 5 to 10 milliseconds. The operation time of a piloted valve depends on its size; typical values are 15 to 150 milliseconds.
A direct acting solenoid valve typically operates in 5 to 10 milliseconds. The operation time of a piloted valve depends on its size; typical values are 15 to 150 milliseconds.
WORKING OF A SOLENOID VALVE:
The solenoid valve has 5 openings. This ensure easy exhausting of 5/2 valve. The spool of the 5/2 valve slide inside the main bore according to spool position; the ports get connected and disconnected. The working principle is as follows.
Position-1:
When the spool is actuated towards outer direction port ‘P’ gets connected to ‘B’ and ‘S’ remains closed while ‘A’ gets connected to ‘R’.
Poisition-2:
When the spool is pushed in the inner direction port ‘P’ and ‘A’ gets connected to each other and ‘B’ to ‘S’ while port ‘R’ remains closed.
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3.3.3 TYPES OF SOLENOID VALVE:
Many variations are possible on the basic, one-way, one-solenoid valve described above:
• one- or two-solenoid valves
• direct current or alternating current powered
• different number of ways and positions
SPECIFICATIONS OF SOLENOID VALVE
Type : 5/2 Valve
Material : Aluminum and plastic
3.3.5. APPLICATIONS:
Solenoid valves are used in fluid power pneumatic and hydraulic systems, to control cylinders, fluid power motors or larger industrial valves. Automatic irrigation sprinkler systems also use solenoid valves with an automatic controller. Domestic washing machines and dishwashers use solenoid valves to control water entry into the machine. Solenoid valves are used in the paintball industry, solenoid valves are usually referred to simply as "solenoids." They are commonly used to control a larger valve used to control 16
the propellant. In addition to this, these valves are now being used in household water purifiers.
Solenoid valves can be used for a wide array of industrial applications, including general on-off control, calibration and test stands, pilot plant control loops, process control systems, and various original equipment manufacturer applications.
3.4. HOSES AND CONNECTORS:
It is provided for the passage of compressed air from the compressor outlet to the operating valve. Two separate pipes also connect the operating valve with the working cylinder pressure drop through and airline depends on the flow rate, pipe diameter, and pipe length and pipe geometry. It can be determined directly for straight pipes of any given length. A small chaining bore size can have marked effect on pressure drop, whereas even doubling the pipe length, will only result in doubling the pressure drop.
Typically a rubber hose is constructed of an extruded inside synthetic rubber tube that has the sole purpose to keep the conveyed fluid in the hose. The elastomeric nature of rubber requires that a reinforcement layer be wound or braided around the tube in order to hold the internal pressure. The reinforcement layer(s) are either textile or steel (or both). To protect these inner layers of the hose from the ambient conditions, an outer synthetic rubber cover is extruded around the reinforcement.
The combination of a hose and hose fitting(s) to make a hose assembly, is a critical process that needs to be carried out by professionally trained personnel who follow strict assembly instructions. Improperly assembled hose fittings can separate from the hose and may cause serious injury or property damage from whipping hose, or from fire or explosion of vapour expelled from the hose. 17
Hose and fitting selection must be made so that the published maximum recommended working pressure of the Hose and fitting are equal to, or greater than the maximum system pressure. Surge pressures or peak transient pressures in the system must be below the maximum working pressure of the hose assembly. Surge pressures and peak pressures can usually only be determined by sensitive electrical instrumentation that measures and indicates pressures at mili-second intervals. Mechanical pressure gauges indicate only average pressures and cannot be used to determine surge pressures or peak transient pressures.
The power transmitted by means of a pressurised fluid varies with pressure and rate of flow. The size of the components must be adequate to keep pressure drops to a minimum and avoid aging due to heat generation or excessive fluid velocity. Parker uses the internationally recognised hose dash size as a measurement of the size of their hoses. This size is a measurement of the inside tube of the hose – not the wall outer diameter.
The minimum bend radius of a hose refers to the minimum radius that the hose may be bent through whilst operating at the maximum allowable published working pressure. Bending radius is not a measurement or indicator of hose flexibility. The catalogue specified values of bending radii are based on international or Parker specifications and have been proven through rigorous impulse testing of the hose assemblies. Bending the hose below the minimum bending radius leads to loss of mechanical strength and hence possible hose failure. A minimum straight length of 1, 5 times the hose’s outside diameter (D) shall be allowed between the hose fitting and the point at which the bend start.
3.4.1. SPECIFICATIONS OF HOSE AND CONNECTOR
3.4.1.1. HOSE
• Max pressure : 10 x 10 ⁵ N/m²
• Outer diameter : 6 mm = 6 x 10 ˉ ³m
• Inner diameter : 3.5 mm = 3.5 x 10 ˉ ³m
3.4.1.2. CONNECTOR
• Max working pressure : 10 x 10 ⁵ N/m²
• Temperature : 0-100 º C
• Fluid medium : Air
• Material : Steel
FLOW CONTROL VALVE:
Flow Control Valves are fitted to all the distribution tubes. This valve is made of brass. Both the ends have stepped surface to insert hoses. A handle is provided to control the flow of oil in every valve.
3.4.2.1 Technical Data:
Size : ¼”
Medium : Air
Port size : 0.635 x 10 ֿ² m
Pressure : 0-8 x 10 ⁵ N/m²
Quantity : 1
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3.4.3 PURPOSE:
This valve is used to speed up the piston movement and also it acts as a one – way restriction valve which means that the air can pass through only one way and it can’t return back.
By using this valve the time consumption is reduced because of the faster movement of the piston.
3.5 CUTTING BLADES
A blade is the portion of a tool, weapon, or machine with an edge that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape surfaces or materials. A blade may be made from a flaking stone, such as flint, metal (usually steel), ceramic, or other material. Blades are one of humanity's oldest tools, and continue to be used for combat, food preparation, and other purposes. During food preparation, knives are mainly used for slicing, chopping, and piercing.
In combat, a blade may be used to slash or puncture, and May also be thrown or otherwise propelled. The function is to sever a nerve, muscle or tendon fibres, or blood vessel to disable or kill the adversary. Severing a major blood vessel typically leads to death due to exsanguination. Shrapnel wounds via the fragments' blade-like nature.
Blades may be used to scrape, moving the blade sideways across a surface, as in an ink eraser, rather than along or through a surface. The angle at which the faces meet is important as a larger angle will make for a duller blade while making the edge stronger. A stronger edge is less likely to dull from fracture or from having the edge roll out of shape.
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The shape of the blade is also important. A thicker blade will be heavier and stronger and stiffer than a thinner one of similar design while also making it experience more drag while slicing or piercing. A filleting knife will be thin enough to be very flexible while a carving knife will be thicker and stiffer; a dagger will be thin so it can pierce while a camping knife will be thicker to it can be stronger and more durable. A strongly curved edge, like a talwar will allow the user to draw the edge of the blade against an opponent even while close to the opponent where a straight sword would be impossible to pull in such a fashion. The curved edge of an axe means that only a small length of the edge will initially strike the tree, concentrating force as does a thinner edge whereas a straight edge could potentially land with the full length of its edge against a flat section of tree. A splitting maul has a convex section to avoid getting stuck in wood where chopping axes can be flat or even concave. A khopesh or falchion or kukri is angled and/or weighted at the distal end so that force is concentrated at the faster moving, heavier part of the blade maximising cutting power and making it largely unsuitable for thrusting where a rapier is thin and tapered allowing it to pierce be moved with more agility while reducing its chopping power compared to a similarly sized sword.
A serrated edge, such as on a saw or a bread knife, concentrates force onto the tips of the serrations which increases pressure as well as allowing soft or fibrous material (like wood, rope, bread, vegetables) to be expand into the spaces between serrations. Whereas pushing any knife, even a bread knife, down onto a bread loaf will just squash the loaf as bread has a low elastic modulus (is soft) but high yield strain (loosely, can be stretched or squashed by a large proportion without breaking), drawing serrations across the loaf with little downward force will allow each serration to simultaneously cut the bread with much less deformation of the loaf. Drawing a smooth blade is less effective as the blade is 22
parallel to the direction draw but the serrations of a serrated blade are at an angle to the fibres. Serrations on knives are often symmetric allowing the blade to cut on both the forward and reverse strokes of a cut, a notable exception beingVeff serrations which are designed to maximise cutting power while moving the blade away from the user. Saw blade serrations, for both wood and metal, are typically asymmetrical so that they cut while moving in only one direction. (Saws act by abrading a material into dust along a narrow channel whereas knives and similar act by forcing the material apart. This means that saws result in a loss of material and the serrations of a saw also serve to carry metal sward and sawdust out of the cut channel.)
Fullers are longitudinal channels either forged into the blade or later machined/milled out of the blade though the later process is less desirable. This loss of material necessarily weakens the blade but serves to make the blade lighter without sacrificing stiffness. The same principle is applied in the manufacture of beams such as I-beams. Fullers are only of significant utility in swords. In most knives there is so little material removed by the fuller than it makes little difference to the weight of the blade and they are largely cosmetic.
3.5.1 DIFFERENT SHAPES OF BLADES FOR CUTTING OPERATIONS
• A normal blade has a curving edge, and straight back. A dull back lets the wielder use fingers to concentrate force; it also makes the knife heavy and strong for its size. The curve concentrates force on a smaller area, making cutting easier. This knife can chop as well as pick and slice. This is also the best single-edged blade shape for thrusting, as the edge cuts a swath that the entire width of the knife can pass through without the spine having to push aside any material on its path, as a sheep foot or drop-point knife would. 23
• A trailing-point knife has a back edge that curves upward to end above the spine. This lets a lightweight knife have a larger curve on its edge and indeed the whole of the knife may be curved. Such a knife is optimized for slicing or slashing. Trailing point blades provide a larger cutting area, or belly, and are common on skinning knives.
• A drop point blade has a convex curve of the back towards the point. It handles much like the clip-point, though with a stronger point typically less suitable for piercing. Swiss army pocket knives often have drop-points on their larger blades.
• A clip-point blade is like a normal blade with the back "clipped". This clip can be either straight or concave. The back edge of the clip may have a false edge that could be sharpened to make a second edge. The sharp tip is useful as a pick, or for cutting in tight places. If the false edge is sharpened it increases the knife's effectiveness in piercing. As well, having the tip closer to the centre of the blade allows greater control in piercing. The Bowie knife has a clip point blade and clip-points are common on pocket knives and other folding knives.
• A sheepsfoot blade has a straight edge and a straight dull back that curves towards the edge at the end. It gives the most control, because the dull back edge is made to be held by fingers. Sheepsfoot blades were originally made to trim the hooves of sheep. Their shape bears no similarity to the foot of a sheep.[8]
• A Wharncliffe blade is similar in profile to a sheep's foot but the curve of the back edge starts closer to the handle and is more gradual. Its blade is much thicker than a knife of comparable size. Wharncliffes were used by sailors, as the shape of the tip prevented accidental penetration of the work or the user's hand with the sudden motion of a ship. 24
• A spey point blade (once used for neutering livestock) has a single, sharp, straight edge that curves strongly upwards at the end to meet a short, dull, straight point from the dull back. With the curved end of the blade being closer to perpendicular to the blade's axis than other knives and lacking a point, making penetration unlikely, spey blades are common on Trapper style pocketknives for skinning fur-bearing animals.
• Leaf blade with a distinctive recurved "waist" adding some curved "belly" to the knife facilitating slicing as well as shifting weight towards the tip meaning that it is commonly used for throwing knives as well as improving chopping ability.
• A spear point blade is a symmetrically-shaped blade with a point aligned with the centerline of the blade's long axis. True spear-point blades are double-edged with a central spine, like a dagger or spearhead. The spear point is one of the stronger blade point designs in terms of penetration stress, and is found on many thrusting knives such as the dagger. The term spear point is occasionally and confusingly used to describe small single-edged blades without a central spine, such as that of the pen knife, a small folding-blade pocket knife formerly used in sharpening quills for writing. Pen-knife may also nowadays refer to the blade pattern of some of larger pocket knife blades that would otherwise be termed drop-point designs.
• A needle point blade has a sharply-tapered acuminated point. It is frequently found on daggers such as the stiletto (which had no sharpened edges) and the Fairbairn-Sykes fighting knife. Its long, narrow point reduces friction and increases the blade's penetrative capabilities, but is liable to stick in bone and can break if abused. When the needle point is combined with a reinforced 'T' section running the length of the blade's spine, it is called a reinforced tip.
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• kris or flame-bladed sword. These blades have a distinct recurved blade form and are sharpened on both sides, typically tapering to (or close to) a symmetrical point.
• Referred to in English speaking countries as a "tanto" or "tanto point" (a corruption of the Japanese word tantō though the tip bears no resemblance to a tantō) or a chisel point. (Chisel point only refers to the straightness of the edge that comprises the end of the blade and not to the knife edge being ground on just one side.) It is similar to, but not the same as, some early Japanese swords that had kamasu kissaki ("barracuda tip"), a nearly straight edge at the tip whereas the typical "tanto point" as found in the west has a straight edge. The barracuda tip sword was sharp but also fragile whereas modern tanto point are often advertised as being stronger at the tip for having nearly the whole thickness of the blade present until quite close to the end of the knife. Knife tests have shown that penetration ability of this style of blade is comparatively poor but it is possible, if the tip is strong, that more force can be applied allowing greater penetration without damaging the tip.
• The lower illustration is a modified tanto where the end is clipped and often sharpened. This brings the tip closer to the centre of the blade increasing control of the blade and improves penetration potential by having a finer point and a sharpened back edge.
• A hawkbill blade is sharpened on the inside edge and is similar to carpet and linoleum knives. The point will tear even if the rest of the knife is comparatively dull. Thekarambit from Far South-East Asia is a hawkbill knife which is held with the blade extending from the bottom of the fist and the tip facing forward. The outside edge of a karambit may be sharp and if so may also feature a backwards facing point. 26
• An ulu (Inuit woman's knife) knife is a sharpened segment of a circle. This blade type has no point, and has a handle in the middle. It is good for scraping, and sometimes chopping. The semi-circular version appears elsewhere in the world and is called a head knife. It is used in leatherworking both to scrape down leather (reducing thickness), and to make precise, rolling cuts for shapes other than straight lines. The circular version is a popular tool for slicing pizzas. One corner is placed at the edge of the pizza and the blade is rolled across in a diameter cut.
3.5.2 SECIFICATIONS OF CUTTING BLADES
Material - Steel
Length - 150 to 200 mm
Height - 15 to 20 mm
Number of blades used - 8 to 10 nos.
3.6. SQUARE PLATE:
A surface plate is a solid, flat plate used as the main horizontal reference plane for precision inspection, marking out (layout), and tooling setup. The 27
surface plate is often used as the baseline for all measurements to the work piece, therefore one primary surface is finished extremely flat with accuracy up to 0.00001 in or 250 nm for a grade AA or AAA plate. Surface plates are a very common tool in the manufacturing industry and are often permanently attached to robotic type inspection devices such as a coordinate-measuring machine. Plates are typically square or rectangular.
The importance of the high-precision surface plate was first recognised by Henry Maudslay around 1800. He originated the systems of scraping a cast-iron plate to flatness, rubbing marking blue between pairs of plates to highlight imperfections, and of working plates in sets of three to guarantee flatness by avoiding matching concave and convex pairs.
Unlike most instruments of mechanical precision, surface plates do not derive their precision from more-precise standards. Instead they originate precision by application of the principle of "automatic generation of gages". In this process, three approximately flat surfaces are progressively refined to precise flatness by manual rubbing against each other in pairs with colouring matter in between then hand scraping off the high points. Any errors of flatness are removed by this scraping, since the only stable, mutually conjugate surface shape is a plane. Joseph Whitworth, who had been an apprentice with Maudslay, described this process to the British Association in 1840 in his paper The Mode of Producing a True Plane as he related during his chairman's address in 1856 at the inaugural meeting of the British Institute of Mechanical Engineers in Glasgow. Whitworth, born in 1803, worked as an apprentice for Maudslay from 1825 but had left by the time he started his own business in 1833. His 1840 paper, and this past work for Maudslay, has led to some writers claiming Whitworth as the originator of the surface plate scraping technique, not Maudslay.