previous description
Cutting fluids are compounds applied to tool points to facilitate metal-cutting operations. There are two general classes: straight-oil cutting fluids and emulsion cutting fluids or the so-called water-soluble oils. The straight oils are usually viscous,dark colored, chemically trated mineral oils, containing sulphur or chlorine or both, and proportions of animal or vegetable oils. Water- soluble or emulsifying oils also conssit of a mixture of mineral oil and animal or vegetable oil chemically treated with sulphur or chlorine. These chemically treated animal or vegetable oils are commonly sulphonated or chlorinated oils according to the process of chemical treatment which they have gone. Soluble oils also contain an emulsifying agent, that is a substance which has the property of causing the oil to form a mily solution or emulsion when stirred into water. Many compounds such as certain soaps and alkaline compounds are used as amulsifying agents. For use, soluble oils are mixed with water in varying percentages from 5 to 95 percent, according to recommendations to the manufacturer. (G.L. Martin, Popular Mechanics, p. 146)
new description
Cutting fluids are applied to the chip formation zone to improve the cutting performance by cooling and/or lubrication effects. In general, from a thermal point of view, the lubricating action is more important at low cutting speeds, whereas the cooling is rather the predominant effect at higher cutting speeds due to more intensive heat generation. Different types of cutting fluids available can be classified according to widely varying criteria, although a somewhat unified system of terminology is used in the different standards. For example, German DIN 51385 proposes cutting fluids to be primarily divided into non-water miscible and water miscible CFs, as shown in Fig. 10,1. Non-water miscible, also known as oil-based cutting fluids, straight of neat oils, are supplied as ready-to-use products. Water mixed cutting fluids are also supplied as ready-to-use, while water miscible products are supplied as a concentrate which must be diluted before application. Once mixed, the constituents can form either a solution or an emulsion.
(Advanced machining processes of metallic materials, Wit Grzesik, pp.141,142)
2 - Polymer Degradation ( material )
previous description
Polymeric materials also experience deterioration by means of environmental interactions.
However, an undesirable interaction is specified as degradation rather
than corrosion because the processes are basically dissimilar.Whereas most metallic
corrosion reactions are electrochemical, by contrast, polymeric degradation is physiochemical; that is, it involves physical as well as chemical phenomena. Furthermore,
a wide variety of reactions and adverse consequences are possible for polymer
degradation. Polymers may deteriorate by swelling and dissolution. Covalent bond
rupture, as a result of heat energy, chemical reactions, and radiation is also possible,
ordinarily with an attendant reduction in mechanical integrity. It should also be
mentioned that because of the chemical complexity of polymers, their degradation
mechanisms are not well understood.
(William D. Callister, Materials Science and Engineering An Introduction 7th ed., pg. 655)
new description
Polymer degradation has been known since the earliest times and there are several everyday examples such as the deterioration of cellulose in wood, rubber in car tyres and the cracking and yellowing of paint films, to name but a few. The types of degradation processes vary depending upon the environmental conditions in which the polymer is used to the manufacturing history and structure of the polymer; all of which play an integral role in controlling the overall rate determining step.
The degradation and oxidation of natural polymers although known for some time are complicated by naturally occurring species. Wool and cellulose are notorious in this regard where our understanding of the basic mechanisms of degradation are much more complex and little understood. With the advent of cellulosic esters other degradation problems became evident such as flammability and instability with regard to hydrolysis and release of acids. Indeed it is only in recent years that any basic understanding of the mechanistic processes of the latter problems have been achieved.
(Fundamentals of polymer degradation and stabilisation, Norman S. Allen, Michele Edge,p1)
3 - Ultrasonic Machining: ( manufacturing )
previous description
Polymeric materials also experience deterioration by means of environmental interactions.
However, an undesirable interaction is specified as degradation rather
than corrosion because the processes are basically dissimilar.Whereas most metallic
corrosion reactions are electrochemical, by contrast, polymeric degradation is physiochemical; that is, it involves physical as well as chemical phenomena. Furthermore,
a wide variety of reactions and adverse consequences are possible for polymer
degradation. Polymers may deteriorate by swelling and dissolution. Covalent bond
rupture, as a result of heat energy, chemical reactions, and radiation is also possible,
ordinarily with an attendant reduction in mechanical integrity. It should also be
mentioned that because of the chemical complexity of polymers, their degradation
mechanisms are not well understood.
(William D. Callister, Materials Science and Engineering An Introduction 7th ed., pg. 655)
new description
Polymer degradation has been known since the earliest times and there are several everyday examples such as the deterioration of cellulose in wood, rubber in car tyres and the cracking and yellowing of paint films, to name but a few. The types of degradation processes vary depending upon the environmental conditions in which the polymer is used to the manufacturing history and structure of the polymer; all of which play an integral role in controlling the overall rate determining step.
The degradation and oxidation of natural polymers although known for some time are complicated by naturally occurring species. Wool and cellulose are notorious in this regard where our understanding of the basic mechanisms of degradation are much more complex and little understood. With the advent of cellulosic esters other degradation problems became evident such as flammability and instability with regard to hydrolysis and release of acids. Indeed it is only in recent years that any basic understanding of the mechanistic processes of the latter problems have been achieved.
(Fundamentals of polymer degradation and stabilisation, Norman S. Allen, Michele Edge,p1)
3 - Ultrasonic Machining: ( manufacturing )
previous description
Ultrasonic machining (USM) actually involves two different processes: ultrasonic impact grinding and rotary ultrasonic machining. Ultrasonic impact grinding (USIG) involves rapid oscilation of a shaped tool immersed in a slurry of abrasive that is also in contact with the workpiece. This oscilation drives abrassive particles against the workpiece and cuts in it a cavity that has the same shape as the tool. The oscillating frequency of the tool is from 19,000 to 25,000 Hz, and its amplitude is only 0.013 to 0.063 mm. The gap between the tool and the workpiece is small and the abrassive slurry is pumped through this gap. The tool is normally of low-carbon or stainless steel and is fastened to an ultrasonic generator through a horn of Monel metal. The abrassive particles may be aluminum oxide, silicon carbide, or boron carbide. Rotary ultrasonic machining is similar to conventional drilling or milling of glass or other nonmetallics except that the rotating diamond-coated tool is also vibrated at an ultrasonic frequency (20 kHz). There is no abrassive slurry as in ultrasonic impact grinding, but there is a coolant(usually water) that flushes away the removed material. The ultrasonic vibration reduces the pressure on the cutting tool an the friction at the point of cutting. It provides better coolant flow andbetter flushing of removed material. These factors result in faster cutting action. (J.G. Bralla, Design for manufacturability handbook, p.142) Cutting Fluids:Cutting fluids are compounds applied to tool points to facilitate metal-cutting operations. There are two general classes: straight-oil cutting fluids and emulsion cutting fluids or the so-called water-soluble oils. The straight oils are usually viscous,dark colored, chemically trated mineral oils, containing sulphur or chlorine or both, and proportions of animal or vegetable oils. Water- soluble or emulsifying oils also conssit of a mixture of mineral oil and animal or vegetable oil chemically treated with sulphur or chlorine. These chemically treated animal or vegetable oils are commonly sulphonated or chlorinated oils according to the process of chemical treatment which they have gone. Soluble oils also contain an emulsifying agent, that is a substance which has the property of causing the oil to form a mily solution or emulsion when stirred into water. Many compounds such as certain soaps and alkaline compounds are used as amulsifying agents. For use, soluble oils are mixed with water in varying percentages from 5 to 95 percent, according to recommendations to the manufacturer. (G.L. Martin, Popular Mechanics, p. 146)
new description
Ultrasonic machining is used for precision machining of hard brittle materials. A grit-loaded slurry is circulated between the workpiece and the tool. The tool vibrates at ultrasonic frequency of 20 to 40 kHz and gradually fed into the workpiece. Material is removed by the abrasive action of the slurry and impact force due to vibration of the tool. The tool has the same shape as the groove to be machined. Analysis of the mechanism of material removal indicated that the process can be called ultrasonic grinding (USG)
(Fundamentals of Machining and Machine Tools,Singal R.K. Et.Al,R. K. Singal,Mridual Singal,p151)
4 - Engineer to Order (ETO) - ( scheduling )
previous description
To explain engineer to order first we should explain make to order (MTO). MTO involves having all the components available along with the engineering designs, but the product is not actually specified. The finished product from this system is partially one of a kind, but not entirely one of a kind because the final product is not usually designed from a basic specification. The engineer to order is an extension of the MTO system with the engineering design of the product being almost totally based on customer specification. The same characteristics apply here as to the case of MTO, but customer interaction is even greater. True one of a kind products are engineered to order. (Higgins, Le Roy, Tierney; Manufacturing planning and control: beyond MRP II; pg. 13,14)
new description
Notice that within engineer to order (ETO), engineering time is actually planned rahter than inventory. In essence, the engineering resource is the commodity being planned and "stocked" , ready for the manufacturing process must be planned or available within the lead time required by the customer. In the case of ETO product, in many markets there is not enough time to recruit, hire, train, and engage engineers after an order is received, although there are expections to that rule. Extra large capital goods, such as airplanes or submarines, can, in some cases, have longer customer-acceptable accumulative lead time that allows for ETO strategy to work.
(World class master scheduling,Donald H. Sheldon,pp.24,25)
5 - Snap-fit ( manufacturing, design )
previous description
In all types of joints, a protruding part of one component, such as a hook, stud, or bead, is briefly deflected during the joining operation, and it is made to catch in a depression (undercut) in the mating component. This method of assembly is uniquely suited to thermoplastic materials due to their flexibility, high elongation, and ability to be molded into complex shapes. However, snap-fit joints cannot carry a load in excess of the force necessary to make or break the snap-fit. Snap-fit assemblies are usually employedto attachlids or covers that are meant to be disassembled or that will be lightly loaded. The design should be such that, after assembly, the joint will return to a stress-free condition.
new description
Notice that within engineer to order (ETO), engineering time is actually planned rahter than inventory. In essence, the engineering resource is the commodity being planned and "stocked" , ready for the manufacturing process must be planned or available within the lead time required by the customer. In the case of ETO product, in many markets there is not enough time to recruit, hire, train, and engage engineers after an order is received, although there are expections to that rule. Extra large capital goods, such as airplanes or submarines, can, in some cases, have longer customer-acceptable accumulative lead time that allows for ETO strategy to work.
(World class master scheduling,Donald H. Sheldon,pp.24,25)
5 - Snap-fit ( manufacturing, design )
previous description
In all types of joints, a protruding part of one component, such as a hook, stud, or bead, is briefly deflected during the joining operation, and it is made to catch in a depression (undercut) in the mating component. This method of assembly is uniquely suited to thermoplastic materials due to their flexibility, high elongation, and ability to be molded into complex shapes. However, snap-fit joints cannot carry a load in excess of the force necessary to make or break the snap-fit. Snap-fit assemblies are usually employedto attachlids or covers that are meant to be disassembled or that will be lightly loaded. The design should be such that, after assembly, the joint will return to a stress-free condition.
(Harper C.A., Handbook of Plastics, Elastomers, and Composites, pg.547)
new description (better)
The snap fit is one of the most versatile and economic joining elements. They are composed of a hook, at the end of cantilever beam, and a groove. The beam deflects as the mating parts are pushed together until the hook fally into the groove, holding the parts in place. The basic snap fit assembly with the insertion, deflection and recovery action during assembly is schematically depicted in Fig. 5.55.
The snap fit geometry shown in the figure shows as assembly as well as disassembly angle.
(International plastics handbook, Tim A. Osswald, pp499,500)
The snap fit is one of the most versatile and economic joining elements. They are composed of a hook, at the end of cantilever beam, and a groove. The beam deflects as the mating parts are pushed together until the hook fally into the groove, holding the parts in place. The basic snap fit assembly with the insertion, deflection and recovery action during assembly is schematically depicted in Fig. 5.55.
The snap fit geometry shown in the figure shows as assembly as well as disassembly angle.
(International plastics handbook, Tim A. Osswald, pp499,500)
Deniz, you should write type of definition(material, production method etc.) and which one is better for your mind.
ReplyDeleteThanks for warning, fixed.
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