Roll Forming (Manufacturing Technique)
Rolll forming is a continuous bending process in which opposing rolls are used to produce long sections of formed shapes from coil or strip stock. Several pairs of rolls are usually required to progressively accomplish the bending of stock into the desired shape. Products made by roll forming include channels, gutters, metal siding sections (for homes), pipes and tubing with seams, and various structural sections. Although roll forming has the general appearance of rolling operation (and the tooling certainly looks similar), the difference is that roll forming involves bending rather than compressing the work.
(M. P. Groover, Fundamentals of Modern Manufacturing, p. 470)
Roll Forming
Roll forming is a high production process of forming metal parts from coiled, strip, or sheet stock. This is done by feeding the materials longitudinally through successive pairs of rolls, each pair progressively doing its particular forming assignment until the desired cross section is produced. On its way through the rolls, the metal may be hole punched, mitered, notched, embossed, swedged. and/or edge rolled. Much press or brake work can be done at a substantial sav-ings by roll forming. Roll forming has the additional advantage of being able to feed two different materials, one on top of the other, to form a single product. In this way, desirable properties such as ductility, corrosion protection, tensile strength, and superior finish can be obtained.
( Brown J.A. Modern manufacturing processes, Industrial Press Inc. Page :144)
Honestly said that both definition about terms is same. Because roll forming is a common and known manufacturing technique all books.
Oxyfuel Gas Cutting (Manufacturing Technique)
Oxyfuel gas cutting (OFC) is defined as a group of cutting processes used to sever metals by means of the chemical reaction of oxygen with the base metal at elevated temperatures. The necessary temperature is maintained by means of flames obtained from the combustion of specified fuel gas mixed with pure oxygen — Fig. 1. Oxyfuel gas cutting is based on the rapid formation of iron oxide from the introduction of a high pressure pure oxygen stream into the cutting envelope. Since iron oxide melts at a lower temperature than mild steel, the material is removed from the base metal. (J. Donaghy,
Welding Journal-New York, December 1995, page 55)
Oxyfuel Gas Cutting (best)
Oxyfucl gas cutting is used to cut iron base alloys. Low carbon steels (up to 0.3% carbon) are easy to cut Any metal that requires preheating for welding, such as high alloy and high alloy carbon steels should also be pre-heated before cutting. High nickel steeLs, cast iron, and stainless steel are difficult to cut. Most nonferrous met-als—such as brass, copper, and aluminum—cannot be cut by oxyluel cutung. A few reactive nonferrous metals, such as titanium and magnesium, can be cut. These metals sel-dom are cut with the OFC process because of the exten-sive postcut cleanup required.
Whether the casting is pure metal or alloy solidification takes time. The total solidification time is the time required for the casting to solidify after pouring. This time is dependent on the size and shape of the casting by an empirical relationship known as Chroranor's rule, which stales:
where Tts= total solidification time, min: V =volume of the casting, cm^2;,A = surface area of the casting, cm^2; n is an exponent usually taken to have a value = 2: and Cm is the mold constant. Given that n = 2, the units of Cm are min/mis , and its value depends on the particular conditions of the casting operation, including mold material (e.g., specific heat, thermal conductivity). thermal properties of the east metal (e.g., heat of fusion. specific heat, thermal conductivity). and pouring temperature relative to the melting point of the metal. The value of Cm for a given casting operation can be based on experimental data from previous operations carried out using the same mold material, metal, and pouring temperature, even though the shape of the part may be quite different.
Chvorinov's rule indicates that a casting with a higher voltume-to-surface area ratio will cool and solidify more slowly than one with a lower ratio.This principle is put to good use thel designing a mold. To perform its function of feeding molten metal to the maintain. Since the amid conditions for both riser and casting are the sante, their mold constants will be equal.By designing the riser to have a larger volumeito-area ratio, we can he fairly sure that the main casting solidifies first und that the effects of shrinkage are minimized. Before considering how the riser might be designed using Chvormov's rule, let as consider the topic of shrinkage, which is the reason why doers are needed.
( Groover P.M. Fundumentals of Modern Manufacturing: Materials, Process and Systems. 4th Ed. Page:216)
My definiton is the best one because explain totally what is the rule. And clarify how and where is usefull this rule.Also, With this rule consider the mistake during the casting.
PERMANENT MOLD (Manufacturing Technique )
Permanent mold casting refersto all casting technologies in which the mold cavity is reused many times and is made of a metallic material or graphite. This is in contraast to other casting technologies, such as sand casting, investment casting, and others in which the mols is made of nonmetallic materials. Metal mold casting is the predominant way to manufacture shape castings. Specifically, about 90% of all aluminum castings produced are in metal molds, including gravity fed, low-pressure, and high-pressure die castings.
Permanent mold casting technologies are classified as gravity, pressure, squeeze and specialized processes.
(Metal Shaping Process: Casting And Molding, Particulate Processing, Vukuta Boljanovic, page38)
PERMANENT MOLD
Permanent-mold casting uses a metal mold constructed of two sections that are designed for easy, precise opening and closing. These molds are commonly made of steel or cast iron. the cavity, with gating system included, is machined into the two halves to provide accurate dimensions and good surface finish. Metals commonly cast in permanent molds include aluminum, magnesium, copper-base alloys, and cast iron. However, cast iron requires a high pouring temperature, 1250°C to 1500°C (2300"F-2700°F), which takes a heavy toll on mold life. The very high pouring temperatures of steel make permanent molds unsuitable for this metal, unless the mold is made of refractory material.
( Groover P.M. Fundumentals of Modern Manufacturing: Materials, Process and Systems. 3th Ed. Page:226)
Honestly said that both of them is the same. there is small difference betwen them. My definiton is little finger is good than old one. Because It was given some example and detail which is not include old one.
Mold Erosion ( Failure Type )
In die casting the process should be continous and uniform, and the process speed should allow the solidification to start right after the molding is finished. Casting speed is the materials' speed of pouring into the die, and if the casting speed is too much, the flow becomes turbulent. Turbulence has two important dangers:
(Manufacturing Methods, Casting Technology Lecture Notes, A.Aran, p. 14)
Mold Erosion :
One of the key elements to making a metal casting of high quality is the design of a good gating system. This is even more important if a casting is produced by a gravitational process. The process of pouring the molten metal has to be performed carefully: if not, there will be various casting defects directly traceable to pouring the molten metal incorrectly in the stage of mold filling. For example. too rigorous a stream could cause mold erosion: highly turbulent flows could result in air and inclusion entrapments: and finally, relatively slow filling might generate cold shuts. Thus, the design of the gating and venting overflow systems has to take into consideration the proper control ol the liquid metal as it fills the mold.
( Boljanovic V. Metal Shaping Processes.Industrial Press Inc. NY 2009.Page:6)
Old one is the best. Saying this is a duty for honest man. My definition is the best one which I chose this some books.
Honestly said that both definition about terms is same. Because roll forming is a common and known manufacturing technique all books.
Oxyfuel Gas Cutting (Manufacturing Technique)
Oxyfuel gas cutting (OFC) is defined as a group of cutting processes used to sever metals by means of the chemical reaction of oxygen with the base metal at elevated temperatures. The necessary temperature is maintained by means of flames obtained from the combustion of specified fuel gas mixed with pure oxygen — Fig. 1. Oxyfuel gas cutting is based on the rapid formation of iron oxide from the introduction of a high pressure pure oxygen stream into the cutting envelope. Since iron oxide melts at a lower temperature than mild steel, the material is removed from the base metal. (J. Donaghy,
Welding Journal-New York, December 1995, page 55)
Oxyfuel Gas Cutting (best)
Oxyfucl gas cutting is used to cut iron base alloys. Low carbon steels (up to 0.3% carbon) are easy to cut Any metal that requires preheating for welding, such as high alloy and high alloy carbon steels should also be pre-heated before cutting. High nickel steeLs, cast iron, and stainless steel are difficult to cut. Most nonferrous met-als—such as brass, copper, and aluminum—cannot be cut by oxyluel cutung. A few reactive nonferrous metals, such as titanium and magnesium, can be cut. These metals sel-dom are cut with the OFC process because of the exten-sive postcut cleanup required.
( Jeffus L.S. Welding: principles and applications 5th Edition. Thomas Delmar Learning. page:151 )
My definition is the best one. Explain too much detail about technique. Also my definition incluede some specific example.
Chvorinov's Rule:(Casting Property)
The size of feeders and risers are shaped according to the volume and shape of the area. In a proper molding process feeders and risers are supposed to be the last solidifying parts. The time required for solidifying is calculated using the "Chvorinov's Rule" .
ts=Cd*(V/A)^n
ts is solidification time , Cd is die coefficient, V is volume and A is total area of the part.(Manufacturing Methods, Casting Technology Lecture Notes, A.Aran, p. 29)
The size of feeders and risers are shaped according to the volume and shape of the area. In a proper molding process feeders and risers are supposed to be the last solidifying parts. The time required for solidifying is calculated using the "Chvorinov's Rule" .
ts=Cd*(V/A)^n
ts is solidification time , Cd is die coefficient, V is volume and A is total area of the part.(Manufacturing Methods, Casting Technology Lecture Notes, A.Aran, p. 29)
Chvorinov's Rule:
Whether the casting is pure metal or alloy solidification takes time. The total solidification time is the time required for the casting to solidify after pouring. This time is dependent on the size and shape of the casting by an empirical relationship known as Chroranor's rule, which stales:
where Tts= total solidification time, min: V =volume of the casting, cm^2;,A = surface area of the casting, cm^2; n is an exponent usually taken to have a value = 2: and Cm is the mold constant. Given that n = 2, the units of Cm are min/mis , and its value depends on the particular conditions of the casting operation, including mold material (e.g., specific heat, thermal conductivity). thermal properties of the east metal (e.g., heat of fusion. specific heat, thermal conductivity). and pouring temperature relative to the melting point of the metal. The value of Cm for a given casting operation can be based on experimental data from previous operations carried out using the same mold material, metal, and pouring temperature, even though the shape of the part may be quite different.
Chvorinov's rule indicates that a casting with a higher voltume-to-surface area ratio will cool and solidify more slowly than one with a lower ratio.This principle is put to good use thel designing a mold. To perform its function of feeding molten metal to the maintain. Since the amid conditions for both riser and casting are the sante, their mold constants will be equal.By designing the riser to have a larger volumeito-area ratio, we can he fairly sure that the main casting solidifies first und that the effects of shrinkage are minimized. Before considering how the riser might be designed using Chvormov's rule, let as consider the topic of shrinkage, which is the reason why doers are needed.
( Groover P.M. Fundumentals of Modern Manufacturing: Materials, Process and Systems. 4th Ed. Page:216)
My definiton is the best one because explain totally what is the rule. And clarify how and where is usefull this rule.Also, With this rule consider the mistake during the casting.
PERMANENT MOLD (Manufacturing Technique )
Permanent mold casting refersto all casting technologies in which the mold cavity is reused many times and is made of a metallic material or graphite. This is in contraast to other casting technologies, such as sand casting, investment casting, and others in which the mols is made of nonmetallic materials. Metal mold casting is the predominant way to manufacture shape castings. Specifically, about 90% of all aluminum castings produced are in metal molds, including gravity fed, low-pressure, and high-pressure die castings.
Permanent mold casting technologies are classified as gravity, pressure, squeeze and specialized processes.
(Metal Shaping Process: Casting And Molding, Particulate Processing, Vukuta Boljanovic, page38)
PERMANENT MOLD
Permanent-mold casting uses a metal mold constructed of two sections that are designed for easy, precise opening and closing. These molds are commonly made of steel or cast iron. the cavity, with gating system included, is machined into the two halves to provide accurate dimensions and good surface finish. Metals commonly cast in permanent molds include aluminum, magnesium, copper-base alloys, and cast iron. However, cast iron requires a high pouring temperature, 1250°C to 1500°C (2300"F-2700°F), which takes a heavy toll on mold life. The very high pouring temperatures of steel make permanent molds unsuitable for this metal, unless the mold is made of refractory material.
( Groover P.M. Fundumentals of Modern Manufacturing: Materials, Process and Systems. 3th Ed. Page:226)
Honestly said that both of them is the same. there is small difference betwen them. My definiton is little finger is good than old one. Because It was given some example and detail which is not include old one.
Mold Erosion ( Failure Type )
In die casting the process should be continous and uniform, and the process speed should allow the solidification to start right after the molding is finished. Casting speed is the materials' speed of pouring into the die, and if the casting speed is too much, the flow becomes turbulent. Turbulence has two important dangers:
- Material is exposed to air much more than laminar flow
- Mold Erosion is occured
(Manufacturing Methods, Casting Technology Lecture Notes, A.Aran, p. 14)
Mold Erosion :
One of the key elements to making a metal casting of high quality is the design of a good gating system. This is even more important if a casting is produced by a gravitational process. The process of pouring the molten metal has to be performed carefully: if not, there will be various casting defects directly traceable to pouring the molten metal incorrectly in the stage of mold filling. For example. too rigorous a stream could cause mold erosion: highly turbulent flows could result in air and inclusion entrapments: and finally, relatively slow filling might generate cold shuts. Thus, the design of the gating and venting overflow systems has to take into consideration the proper control ol the liquid metal as it fills the mold.
( Boljanovic V. Metal Shaping Processes.Industrial Press Inc. NY 2009.Page:6)
Old one is the best. Saying this is a duty for honest man. My definition is the best one which I chose this some books.
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