A modern variation on this method is called "ceramic shell"; instead of the cow-dung and clay, a silicaceous slurry is used to cover the model by dipping and/or pouring. Special dry aggregate is then applied to the wet pattern, either by hand or by using a "fluidized bed", which blows the dry particles around in a confined space, covering the wet areas until no more will adhere. The coated pattern is then left to dry a while and another layer of wet and dry material is applied. This is repeated, using coarser aggregate on the outermost layers, until a sufficient thickness has built up so the mold will hold together through the burn-out and pouring. lost wax casting, alloy steel casting
The other method commonly used is called "investment" casting. The pattern is set up in much the same way as for ceramic shell, except that more venting is necessary due to the decreased porosity of the mold material, which is made using gypsum plaster (plaster of Paris) as a binder for sand, silica flour, or another refractory aggregate. There are many proprietary investment mixtures available, or one may choose to mix one's own. The dry ingredients are mixed with water and poured into a container or "flask" surrounding the gated model, which is either waxed down to a board or attached to a commercially available rubber device which holds the pattern and flask. Jewelry flasks are generally placed in a vacuum chamber while this mixure is still fluid, where they are boiled at room temperature to remove air-bubbles clinging to the models. It is helpful to de-air the investment mixture before pouring it over the wax models, in order to reduce boiling-over when vacuuming.
Once the plaster mixture has set hard, the flasks are placed in a kiln, slowly heated to between 1000 and 1250 degrees F, and held at that temperature until all wax residues have disappeared. The place where the wax was is now a void- hence the "lost wax" designation for this process. The metal is then melted and the molds are filled with liquid bronze or whatever metal is being used. The flask is then allowed to cool, then the plaster mold is broken away, revealing the metal part, which faithfully reproduces every detail of the original wax, plus the gates and vents, which must be cut off. Silver, gold, aluminum, brass, or bronze may be used interchangably with this method. Special investment materials and melting equipment are necessary to deal with the higher temperatures of platinum, iron or stainless steel, but the process is much the same. Lower-melting metals such as tin, lead, and zinc may also be cast by this method, but there are other easier methods of casting them, so it is not often done. A variation on the lost-wax method is also used for casting objects in glass. lost wax casting, alloy steel casting
2007年10月31日星期三
2007年10月26日星期五
Aluminum Die Casting Technical introduction
Die-casting is similar to Permanent mold castings except that the metal is injected into the mold under high pressure of 10-210Mpa (1,450-30,500) psi . This results in a more uniform part, generally good surface finish and good dimensional accuracy, as good as 0.2 % of casting dimension. For many parts, post-machining can be totally eliminated, or very light machining may be required to bring dimensions to size. die casting, aluminum die casting
Die-casting can be done using a cold chamber or hot chamber process.
1.In a cold chamber process, the molten metal is ladled into the cold chamber for each shot. There is less time exposure of the melt to the plunger walls or the plunger. This is particularly useful for metals such as Aluminum, and Copper (and its alloys) that alloy easily with Iron at the higher temperatures.
2.In a hot chamber process the pressure chamber is connected to the die cavity is immersed permanently in the molten metal. The inlet port of the pressurizing cylinder is uncovered as the plunger moves to the open (unpressurized) position. This allows a new charge of molten metal to fill the cavity and thus can fill the cavity faster than the cold chamber process. The hot chamber process is used for metals of low melting point and high fluidity such as tin, zinc, and lead that tend not to alloy easily with steel at their melt temperatures. die casting, aluminum die casting, aluminum casting, ADC-12 die casting, automoblile part, motorcycles spare part, aluminum pressure die casting
3.Die casting molds (called dies in the industry) tend to be expensive as they are made from hardened steel-also the cycle time for building these tend to be long. Also the stronger and harder metals such as iron and steel cannot be die-cast
Common Alloys in Die Casting
Aluminum, Zinc and Copper alloys are the materials predominantly used in die-casting. On the other hand, pure Aluminum is rarely cast due to high shrinkage, and susceptibility to hot cracking. It is alloyed with Silicon, which increases melt fluidity, reduces machinability. Copper is another alloying element, which increases hardness, reduces ductility, and reduces corrosion resistance.
Aluminum is cast at a temperature of 650 ºC (1200 ºF). It is alloyed with Silicon 9% and Copper about 3.5% to form the Aluminum Association 380 alloy (UNS A03800). Silicon increases the melt fluidity, reduces machinability, Copper increases hardness and reduces the ductility. By greatly reducing the amount of Copper (less than 0.6%) the chemical resistance is improved; thus, AA 360 (UNS A03600) is formulated for use in marine environments. A high silicon alloy is used in automotive engines for cylinder castings, AA 390 (UNS A03900) with 17% Silicon for high wear resistance.
Die-casting can be done using a cold chamber or hot chamber process.
1.In a cold chamber process, the molten metal is ladled into the cold chamber for each shot. There is less time exposure of the melt to the plunger walls or the plunger. This is particularly useful for metals such as Aluminum, and Copper (and its alloys) that alloy easily with Iron at the higher temperatures.
2.In a hot chamber process the pressure chamber is connected to the die cavity is immersed permanently in the molten metal. The inlet port of the pressurizing cylinder is uncovered as the plunger moves to the open (unpressurized) position. This allows a new charge of molten metal to fill the cavity and thus can fill the cavity faster than the cold chamber process. The hot chamber process is used for metals of low melting point and high fluidity such as tin, zinc, and lead that tend not to alloy easily with steel at their melt temperatures. die casting, aluminum die casting, aluminum casting, ADC-12 die casting, automoblile part, motorcycles spare part, aluminum pressure die casting
3.Die casting molds (called dies in the industry) tend to be expensive as they are made from hardened steel-also the cycle time for building these tend to be long. Also the stronger and harder metals such as iron and steel cannot be die-cast
Common Alloys in Die Casting
Aluminum, Zinc and Copper alloys are the materials predominantly used in die-casting. On the other hand, pure Aluminum is rarely cast due to high shrinkage, and susceptibility to hot cracking. It is alloyed with Silicon, which increases melt fluidity, reduces machinability. Copper is another alloying element, which increases hardness, reduces ductility, and reduces corrosion resistance.
Aluminum is cast at a temperature of 650 ºC (1200 ºF). It is alloyed with Silicon 9% and Copper about 3.5% to form the Aluminum Association 380 alloy (UNS A03800). Silicon increases the melt fluidity, reduces machinability, Copper increases hardness and reduces the ductility. By greatly reducing the amount of Copper (less than 0.6%) the chemical resistance is improved; thus, AA 360 (UNS A03600) is formulated for use in marine environments. A high silicon alloy is used in automotive engines for cylinder castings, AA 390 (UNS A03900) with 17% Silicon for high wear resistance.
2007年10月25日星期四
What is Investment Casting?
Investment casting / precision casting or the "lost wax" process has been in use since the construction of the first pyramid. The Egyptians and Chinese used the process in their early history to make jewellery and statues. The investment casting method was largely ignored as an industrial process for the fabrication of parts until the demand for rapidly finished parts during World War II created the need for "near net-shape" components that could readily be put into their final form. At this time new inorganic high temperature ceramic mold binders were developed to industrialize the process applications to include high strength and corrosion resistant materials such as low to high carbon alloy steel, tool steel, stainless steel, and nickel and cobalt base alloys. Aluminum and brass alloys are available also.
It is a process capable of producing intricate shapes weighing from a small fraction of an grams up to 20 Kgs. or more. Some examples would be: aircraft structural parts, components for the automotive industry, military weaponry, jet engines, machinery components, dental appliances, jewelry and many others.
In general, an injection molded wax pattern is used for each part produced which is then encased in multiple layers of ceramic material. The wax pattern is then removed from the ceramic shell mold. The mold is fired in an oven and then molten metal is poured into the cavities left by the evacuated wax pattern. Upon cooling, the resulting precision casting are cleaned and subjected to further processing such as heat treatment. At this point, many parts are in their final form and are ready for use while others may require a small amount of further processing such as machining before reaching their final form.
It is a process capable of producing intricate shapes weighing from a small fraction of an grams up to 20 Kgs. or more. Some examples would be: aircraft structural parts, components for the automotive industry, military weaponry, jet engines, machinery components, dental appliances, jewelry and many others.
In general, an injection molded wax pattern is used for each part produced which is then encased in multiple layers of ceramic material. The wax pattern is then removed from the ceramic shell mold. The mold is fired in an oven and then molten metal is poured into the cavities left by the evacuated wax pattern. Upon cooling, the resulting precision casting are cleaned and subjected to further processing such as heat treatment. At this point, many parts are in their final form and are ready for use while others may require a small amount of further processing such as machining before reaching their final form.
2007年10月22日星期一
Mg Plus Overmolding Equals a Superior Housing
Leading OEM engineering publications have featured the breakthrough design marriage of a CWM mag die cast case with an overmolded polyurethane elastomer.
The new housing, for an advanced Tektronix fiber optic cable tester, offers greater strength and performance over plastic, with part consolidations of the hot-chamber Mg and elastomer unit resulting in a 20% saving compared to similar plastic cases, according to Tektronix engineers. This combination of the two processes is believed to be the first such example incorporating a complex, finely featured magnesium die cast housing.
The application was a cover feature in Design News magazine and was featured in a two-page story in Advanced Materials and Processes magazine. The magnesiusm and elastomer application was a three-page feature in Modern Metals, and was also featured in Product Design and Development.
The new housing, for an advanced Tektronix fiber optic cable tester, offers greater strength and performance over plastic, with part consolidations of the hot-chamber Mg and elastomer unit resulting in a 20% saving compared to similar plastic cases, according to Tektronix engineers. This combination of the two processes is believed to be the first such example incorporating a complex, finely featured magnesium die cast housing.
The application was a cover feature in Design News magazine and was featured in a two-page story in Advanced Materials and Processes magazine. The magnesiusm and elastomer application was a three-page feature in Modern Metals, and was also featured in Product Design and Development.
2007年10月17日星期三
Aluminium Investment Casting
Aluminium Investment Casting also called lost-wax casting, is one of the oldest known metal forming techniques. From 5,000 years ago, when bees wax formed the pattern, to today’s high-technology waxes, refractory materials and specialist alloys, the castings allow the production of components with accuracy, repeatability, versatility and integrity.
The process offers repeatable production of net shape components from a variety of metals and high-performance alloys. It is generally used for small castings, but has produced complete aircraft door frames, with steel castings of up to 300 kg and aluminium castings of up to 30 kg. It is generally more expensive than die casting or sand casting, but can produce complicated shapes that require little rework.
Investment casting dates back thousands of years. Its earliest use was for idols, ornaments and jewellery, using natural beeswax for patterns, clay for the moulds and manually operated bellows for stoking furnaces. Examples have been found in Egypt's tombs of Tutankhamun (1333 – 1324 BC), in Mesopotamia, Mexico, and the Benin civilization in Africa where the process produced detailed artwork of copper, bronze and gold.
The earliest known text that describes the investment casting process (Schedula Diversarum Artium) was written around 1100 A.D. by Theophilus Presbyter, a monk who described various manufacturing processes, including the recipe for parchment and the lost-wax process. This book was used by sculptor and goldsmith Benvenuto Cellini (1500 - 1571), who detailed in his autobiography the investment casting process he used for the Perseus and the Head of Medusa sculpture that stands in the Loggia dei Lanzi in Florence, Italy.
The investment casting process came into use as a modern industrial process in late 19th century, when dentists began using it to make crowns and inlays, as described by Dr. D. Philbrook of Council Bluffs, Iowa in 1897. Its use was accelerated by Dr. William H. Taggart of Chicago, whose 1907 paper described his development of a technique. He also formulated a wax pattern compound of excellent properties, developed an investment material, and invented an air-pressure casting machine.
In the 1940s, World War II increased the demand for precision net shape manufacturing and specialized alloys that could not be shaped by traditional methods, or that required too much machining. Industry turned to investment casting. After the war, its use spread to many commercial and industrial applications that used complex metal parts.
Modern investment casting techniques stem from the development in the United Kingdom of a shell process using wax patterns known as the Investment X Process. This method resolved the problem of wax removal by enveloping a completed and dried shell in a vapor degreaser. The vapor permeated the shell to dissolve and melt the wax. This process has been evolved over years into the current process of melting out the virgin wax in an autoclave.
The process offers repeatable production of net shape components from a variety of metals and high-performance alloys. It is generally used for small castings, but has produced complete aircraft door frames, with steel castings of up to 300 kg and aluminium castings of up to 30 kg. It is generally more expensive than die casting or sand casting, but can produce complicated shapes that require little rework.
Investment casting dates back thousands of years. Its earliest use was for idols, ornaments and jewellery, using natural beeswax for patterns, clay for the moulds and manually operated bellows for stoking furnaces. Examples have been found in Egypt's tombs of Tutankhamun (1333 – 1324 BC), in Mesopotamia, Mexico, and the Benin civilization in Africa where the process produced detailed artwork of copper, bronze and gold.
The earliest known text that describes the investment casting process (Schedula Diversarum Artium) was written around 1100 A.D. by Theophilus Presbyter, a monk who described various manufacturing processes, including the recipe for parchment and the lost-wax process. This book was used by sculptor and goldsmith Benvenuto Cellini (1500 - 1571), who detailed in his autobiography the investment casting process he used for the Perseus and the Head of Medusa sculpture that stands in the Loggia dei Lanzi in Florence, Italy.
The investment casting process came into use as a modern industrial process in late 19th century, when dentists began using it to make crowns and inlays, as described by Dr. D. Philbrook of Council Bluffs, Iowa in 1897. Its use was accelerated by Dr. William H. Taggart of Chicago, whose 1907 paper described his development of a technique. He also formulated a wax pattern compound of excellent properties, developed an investment material, and invented an air-pressure casting machine.
In the 1940s, World War II increased the demand for precision net shape manufacturing and specialized alloys that could not be shaped by traditional methods, or that required too much machining. Industry turned to investment casting. After the war, its use spread to many commercial and industrial applications that used complex metal parts.
Modern investment casting techniques stem from the development in the United Kingdom of a shell process using wax patterns known as the Investment X Process. This method resolved the problem of wax removal by enveloping a completed and dried shell in a vapor degreaser. The vapor permeated the shell to dissolve and melt the wax. This process has been evolved over years into the current process of melting out the virgin wax in an autoclave.
2007年10月15日星期一
Die-cast toy
The term die-cast toy here refers to any toy or collectible model produced by using the die casting method. The toys are made of metal and plastic, the metal used commonly is ZAMAK (or Mazak), an alloy of zinc and aluminium. Zamak is also referred to as white metal or pot metal. The most common die-cast toys are scale models of automobiles, aircraft, construction equipment and trains, although almost anything can be produced by this method.
Contents
A Die Cast Boeing 747 model in 1:400 scale.
A Die Cast Boeing 747 model in 1:400 scale.
Diecast (or die cast, or die-cast) toys were first produced early in the 20th century by manufacturers such as Meccano (Dinky Toys) in the United Kingdom and Dowst Brothers (Tootsietoys) in the United States. The first models on the market were basic, consisting of a small car or van body with no interior. In the early days it was common for impurities in the Zamak alloy to result in metal fatigue; the casting would crack or decompose for no apparent reason. As a result, diecast toys made before World War II are difficult to find in good condition.
Lesney began making diecast toys in 1947. Their popular Matchbox 1-75 series was so named because there were always 75 different vehicles in the line, each packaged in a small box designed to look like those used for matches. These toys became so popular that "Matchbox" was widely used as a generic term for any diecast toy car, regardless of who the actual manufacturer was.
The popularity of diecast toys as collectibles developed in the 1950s, as their detail and quality increased. Consequently, more companies entered the field, including the Corgi brand, produced by Mettoy, which appeared in 1956 and pioneered the use of interiors and clear plastic windows in their models.
In 1968, Hot Wheels were introduced in the United States by Mattel, to address the complaint that they had no line of toys for boys to balance their line of Barbie dolls for girls. Due to the fact that they looked fast and were fast (they were equipped with a low-friction wheel/axle assembly), Hot Wheels quickly gained an important niche in the diecast toy market, becoming one of the world's top sellers and challenging the Matchbox 1-75 series in popularity.
During the 1960s various companies began to use diecast vehicles as promotional items for advertising. The idea that children can play a large part in a family's decision as to what products to buy came into wide circulation. In addition, by the 1980s it was apparent that many diecast vehicles were being purchased by adults as collectibles, not as toys for children. Companies such as McDonald's, Sears Roebuck, Kodak, and Texaco commissioned toymakers to produce promotional models featuring their names and logos, or licensed their use. One early example was an American Airlines London bus produced by Matchbox, an idea other some airlines quickly copied.
Beginning in the mid '70s trucks and other commercial vehicles took a lion's share of the diecast market. Matchbox started the trend when they re-launched their Models of Yesteryear range. They made a score of different versions of their Y-12 Ford Model T van, along with other trucks in colorful liveries such as Coca-Cola, Colman's Mustard, and Cerebos Salt. They also made promotional versions for Smith's Crisps (potato chips) and Harrod's department store. Some models were made exclusively for certain markets and immediately became quite expensive elsewhere: Arnott's Biscuits (Australia) and Sunlight Seife (soap, Germany) are examples.
Corgi copied this idea when they expanded the Corgi Classics line in the mid-'80s, producing more than 50 versions of a 1920s era Thornycroft van. Some collectors disparaged this development as "collecting paint," as the castings were identical; only the decorations were different. Other collectors created what they called the "10-Foot Rule" when the collecting of minor variations of the same vehicle got out of hand. The idea was that, if you couldn't differentiate between two versions of a model from 10 feet away, it wasn't worthwhile to collect both of them.
Despite their popularity, many diecast manufacturers went belly-up in the 1980s. Meccano (Dinky), Matchbox, and Corgi all went bankrupt within a three-year span, which essentially reflected the economic climate in the UK at that time. It had become virtually impossible to manufacture in England and compete on the world market. (Mattel had also long since shifted most of their production from the USA to the far east.) Matchbox was purchased by a Hong Kong conglomerate named Universal Holdings, which moved production from England to Macau. Later (1997), Mattel bought Matchbox, essentially making Hot Wheels and the Matchbox 1-75 line sister brands. The two brands continue to sell under their own separate names.
Meanwhile, Corgi had been acquired by Mattel, which moved the office from Swansea, Wales to Leicester, England, and moved manufacturing to China. Matchbox also bought the Dinky Toys name, long after the Liverpool factory was closed. Manufacturing resumed in China. In a series of subsequent shifts, a group of Corgi executives bought back the Corgi Classics line from Mattel, and portions of the Matchbox line were sold to an Australian company named Tyco (no relation to the Tyco line of HO scale trains, originally made by Mantua Metalworking in New Jersey, USA).
Effectively from the ashes of Matchbox's bankruptcy arose Lledo, a company created by former Matchbox partner Jack Odell. Odell believed that British collectibles for British collectors could still be profitably produced in England. Lledo took over part of the Matchbox factory in Enfield, and introduced their "Models of Days Gone" line of diecast vehicles in 1983. The first series of Days Gone models included re-makes of some of the most popular and respected first and second-generation Matchbox Models of Yesteryear. Lledo models were very popular collectibles in the '80s, leading to a period of diversification (incl. the Vanguards line of classic post-war British vehicles), but by the '90s they were eclipsed by other brands, and by 2002 Lledo went broke. Parts of their line were purchased by Corgi, which moved production to China.
In addition to trucks, Corgi produced hundreds of versions of their 1/64 scale Routemaster bus in the '80s and '90s. Like other collecting and promotional model trends, it started as a trickle and soon became a flood. Many versions were made to be sold exclusively in the stores whose advertising appeared on the buses. Harrods, Selfridges, Gamley's, Hamley's, Army & Navy, Underwood's, and Beatties were among the British stores employing this idea. A South African chain called Dion was one of the few overseas firms to follow suit.
A die cast Yamaha motorcycle model in 1:18 scale.
A die cast Yamaha motorcycle model in 1:18 scale.
Then 1/76 scale buses became very popular in Britain in the late '80s and early '90s, with competing lines from Corgi (the Original Omnibus Company) and Gilbow Holdings (Exclusive First Editions, or EFE) fighting for the market. The 1/76 scale fits in with British 'OO' scale model trains.
By the 1990s NASCAR enjoyed increasing popularity and a large number of racing-related Nascar diecast cars and trucks, painted in the colors of the different racing teams, appeared from various manufacturers. Racing Champions was a leading brand of such models, but there were many others.
In addition to cars, trucks, buses, agricultual implements, and construction equipment, diecast aircraft and military models were popular. While Dinky had made such models decades earlier, new companies entered the field in the '80s and '90s. One producer was Dyna Flites, which went bankrupt in the 1990s, but their market share was quickly taken up by their competitors, including Schabak, Gemini Jets, Herpa, and Dragon Wings.
Contents
A Die Cast Boeing 747 model in 1:400 scale.
A Die Cast Boeing 747 model in 1:400 scale.
Diecast (or die cast, or die-cast) toys were first produced early in the 20th century by manufacturers such as Meccano (Dinky Toys) in the United Kingdom and Dowst Brothers (Tootsietoys) in the United States. The first models on the market were basic, consisting of a small car or van body with no interior. In the early days it was common for impurities in the Zamak alloy to result in metal fatigue; the casting would crack or decompose for no apparent reason. As a result, diecast toys made before World War II are difficult to find in good condition.
Lesney began making diecast toys in 1947. Their popular Matchbox 1-75 series was so named because there were always 75 different vehicles in the line, each packaged in a small box designed to look like those used for matches. These toys became so popular that "Matchbox" was widely used as a generic term for any diecast toy car, regardless of who the actual manufacturer was.
The popularity of diecast toys as collectibles developed in the 1950s, as their detail and quality increased. Consequently, more companies entered the field, including the Corgi brand, produced by Mettoy, which appeared in 1956 and pioneered the use of interiors and clear plastic windows in their models.
In 1968, Hot Wheels were introduced in the United States by Mattel, to address the complaint that they had no line of toys for boys to balance their line of Barbie dolls for girls. Due to the fact that they looked fast and were fast (they were equipped with a low-friction wheel/axle assembly), Hot Wheels quickly gained an important niche in the diecast toy market, becoming one of the world's top sellers and challenging the Matchbox 1-75 series in popularity.
During the 1960s various companies began to use diecast vehicles as promotional items for advertising. The idea that children can play a large part in a family's decision as to what products to buy came into wide circulation. In addition, by the 1980s it was apparent that many diecast vehicles were being purchased by adults as collectibles, not as toys for children. Companies such as McDonald's, Sears Roebuck, Kodak, and Texaco commissioned toymakers to produce promotional models featuring their names and logos, or licensed their use. One early example was an American Airlines London bus produced by Matchbox, an idea other some airlines quickly copied.
Beginning in the mid '70s trucks and other commercial vehicles took a lion's share of the diecast market. Matchbox started the trend when they re-launched their Models of Yesteryear range. They made a score of different versions of their Y-12 Ford Model T van, along with other trucks in colorful liveries such as Coca-Cola, Colman's Mustard, and Cerebos Salt. They also made promotional versions for Smith's Crisps (potato chips) and Harrod's department store. Some models were made exclusively for certain markets and immediately became quite expensive elsewhere: Arnott's Biscuits (Australia) and Sunlight Seife (soap, Germany) are examples.
Corgi copied this idea when they expanded the Corgi Classics line in the mid-'80s, producing more than 50 versions of a 1920s era Thornycroft van. Some collectors disparaged this development as "collecting paint," as the castings were identical; only the decorations were different. Other collectors created what they called the "10-Foot Rule" when the collecting of minor variations of the same vehicle got out of hand. The idea was that, if you couldn't differentiate between two versions of a model from 10 feet away, it wasn't worthwhile to collect both of them.
Despite their popularity, many diecast manufacturers went belly-up in the 1980s. Meccano (Dinky), Matchbox, and Corgi all went bankrupt within a three-year span, which essentially reflected the economic climate in the UK at that time. It had become virtually impossible to manufacture in England and compete on the world market. (Mattel had also long since shifted most of their production from the USA to the far east.) Matchbox was purchased by a Hong Kong conglomerate named Universal Holdings, which moved production from England to Macau. Later (1997), Mattel bought Matchbox, essentially making Hot Wheels and the Matchbox 1-75 line sister brands. The two brands continue to sell under their own separate names.
Meanwhile, Corgi had been acquired by Mattel, which moved the office from Swansea, Wales to Leicester, England, and moved manufacturing to China. Matchbox also bought the Dinky Toys name, long after the Liverpool factory was closed. Manufacturing resumed in China. In a series of subsequent shifts, a group of Corgi executives bought back the Corgi Classics line from Mattel, and portions of the Matchbox line were sold to an Australian company named Tyco (no relation to the Tyco line of HO scale trains, originally made by Mantua Metalworking in New Jersey, USA).
Effectively from the ashes of Matchbox's bankruptcy arose Lledo, a company created by former Matchbox partner Jack Odell. Odell believed that British collectibles for British collectors could still be profitably produced in England. Lledo took over part of the Matchbox factory in Enfield, and introduced their "Models of Days Gone" line of diecast vehicles in 1983. The first series of Days Gone models included re-makes of some of the most popular and respected first and second-generation Matchbox Models of Yesteryear. Lledo models were very popular collectibles in the '80s, leading to a period of diversification (incl. the Vanguards line of classic post-war British vehicles), but by the '90s they were eclipsed by other brands, and by 2002 Lledo went broke. Parts of their line were purchased by Corgi, which moved production to China.
In addition to trucks, Corgi produced hundreds of versions of their 1/64 scale Routemaster bus in the '80s and '90s. Like other collecting and promotional model trends, it started as a trickle and soon became a flood. Many versions were made to be sold exclusively in the stores whose advertising appeared on the buses. Harrods, Selfridges, Gamley's, Hamley's, Army & Navy, Underwood's, and Beatties were among the British stores employing this idea. A South African chain called Dion was one of the few overseas firms to follow suit.
A die cast Yamaha motorcycle model in 1:18 scale.
A die cast Yamaha motorcycle model in 1:18 scale.
Then 1/76 scale buses became very popular in Britain in the late '80s and early '90s, with competing lines from Corgi (the Original Omnibus Company) and Gilbow Holdings (Exclusive First Editions, or EFE) fighting for the market. The 1/76 scale fits in with British 'OO' scale model trains.
By the 1990s NASCAR enjoyed increasing popularity and a large number of racing-related Nascar diecast cars and trucks, painted in the colors of the different racing teams, appeared from various manufacturers. Racing Champions was a leading brand of such models, but there were many others.
In addition to cars, trucks, buses, agricultual implements, and construction equipment, diecast aircraft and military models were popular. While Dinky had made such models decades earlier, new companies entered the field in the '80s and '90s. One producer was Dyna Flites, which went bankrupt in the 1990s, but their market share was quickly taken up by their competitors, including Schabak, Gemini Jets, Herpa, and Dragon Wings.
2007年10月11日星期四
Lost-wax casting
1. Sculpting. An artist creates an original artwork from wax, clay, or another material. Wax and oil-based clay are often preferred because these materials retain their softness.
2. Moldmaking. A mold is made of the original sculpture. Most molds are at least two pieces, and a shim with keys is placed between the two halves during construction so that the mold can be put back together accurately. Most molds of small sculptures are made from plaster, but can also be made of fiberglass or other materials. To preserve the fine details on the original artwork's surface, there is usually an inner mold made of latex, vinyl, or silicone which is supported by the plaster part of the mold. Usually, the original artwork is destroyed during the making and initial deconstruction of the plaster mold. This is because the originals are solid, and do not easily bend as the plaster mold is removed. Often long, thin pieces are cut off of the original and molded separately. Sometimes, especially in the case of large original (such as life-size) sculptures, many molds are needed to recreate the original sculpture.
3. Wax. Once the plaster and latex mold is finished, molten wax is poured into it and swished around until an even coating, usually about 1/8 inches thick, covers the entire inner surface of the mold. This must be done in several layers until desired thickness is reached.
4. Removal of wax. This new, hollow wax copy of the original artwork is removed from the mold. The artist may reuse the mold to make more wax copies, but wear and tear on the mold limit their number. For small bronze artworks, a common number of copies today is around 25.
5. Chasing. Each hollow wax copy is then "chased": a heated metal tool is used to rub out all the marks which show the "parting line" or "flashing" where the pieces of the mold came together. The wax is then "dressed" to hide any imperfections. The way the wax looks at this stage, is what it will look like when it is cast. Wax pieces that were molded separately can be heated and attached; foundries often use "registration marks" to indicate exactly where they go.
6. Spruing. Once the wax copy looks just like the original artwork, it is "sprued" with a treelike structure of wax that will eventually provide paths for molten bronze to flow, while allowing air to escape. The carefully-planned spruing usually begins at the top with a wax "cup," which is attached by wax cylinders to various points on the wax copy.
7. Slurry. A "sprued" wax copy is dipped into a slurry of liquid silica, then into a sand-like "stucco", or dry crystalline silica of a controlled grain size. The slurry and grit combination is called "ceramic shell" mold material, although it is not literally made of ceramic. This shell is allowed to dry, and the process is repeated until a half-inch thick or thicker dries coating covers the entire piece. The bigger the piece, the thicker the shell needs to be. Only the inside of the cup is not coated, and the cup's flat top serves as the base upon which the piece stands during this process.
8. Burnout. The ceramic shell-coated piece is placed cup-down in a kiln, whose heat hardens the silica coatings into a shell, and the wax melts and runs out. The melted wax can be recovered and reused, although often it is simply combusted by the burnout process. Now all that remains of the original artwork is the negative space, formerly occupied by the wax, inside the hardened ceramic shell. The feeder and vent tubes and cup are now hollow, also.
9. Testing. The ceramic shell is allowed to cool, then is tested to see if water will flow through the feeder and vent tubes as necessary. Cracks or leaks can be patched with thick refractory paste. To test the thickness, holes can be drilled into the shell, then patched.
10. Pouring. The shell is reheated in the kiln to harden the patches, then placed cup-upwards into a tub filled with sand. Bronze is melted in a crucible in a furnace, then poured carefully into the shell. If the shell were not hot, the temperature difference would shatter it. The bronze-filled shells are allowed to cool.
11. Release.The shell is hammered or sand-blasted away, releasing the rough bronze. The spruing, which are also faithfully recreated in metal, are cut off, to be reused in another casting.
12. Metal-chasing. Just as the wax copies were "chased," the bronze copies are worked until the telltale signs of casting are removed, and the sculptures again look like the original artwork. Pits left by air bubbles in the molten bronze are filled, and the stubs of spruing filed down and polished.
13. Patinating. The bronze is colored to the artist's preference, using chemicals applied to heated or cooled metal. Using heat is probably the most predictable method, and allows the artist to have the most control over the process. This coloring is called patina, and is often green, black, white or brownish to simulate the surfaces of ancient bronze sculptures. (Ancient bronzes gained their patinas from oxidisation and other effects of being on Earth for many years.) However, with current artistic trends in the United States, many artists prefer that their bronzes have brighter, more stylized patinas. Patinas can be applied to replicate marble or stone. Depending on how the metal is prepared, either sandblasted or polished, the finish can be either opaque or transparent. After the patina is applied, a coating of wax, which is the most traditional type of sealer, is usually applied to protect the surface. Many artists prefer to use lacquer as a sealer on some of the more unstable patinas. This protects the piece more from ultraviolet rays. Some patinas change color over time because of oxidiation, and the wax layer slows this down somewhat.
On the left is an example of a lost-wax process mold, and on the right is the resulting bronze sculpture.
On the left is an example of a lost-wax process mold, and on the right is the resulting bronze sculpture.
The lost-wax process can also be used with any material that can burn, melt, or evaporate to leave a mold cavity. Some automobile manufacturers use a lost-foam technique to make engine blocks. The model in this case is made of polystyrene foam, which is then placed into a casting flask, consisting of a cope and drag, which is then filled with casting sand. The foam supports the sand, allowing shapes to be made which would not be possible if the process had to rely on the sand alone to hold its shape. The metal is then poured in, and the heat of the metal vaporizes the foam as the metal enters the mold.
2. Moldmaking. A mold is made of the original sculpture. Most molds are at least two pieces, and a shim with keys is placed between the two halves during construction so that the mold can be put back together accurately. Most molds of small sculptures are made from plaster, but can also be made of fiberglass or other materials. To preserve the fine details on the original artwork's surface, there is usually an inner mold made of latex, vinyl, or silicone which is supported by the plaster part of the mold. Usually, the original artwork is destroyed during the making and initial deconstruction of the plaster mold. This is because the originals are solid, and do not easily bend as the plaster mold is removed. Often long, thin pieces are cut off of the original and molded separately. Sometimes, especially in the case of large original (such as life-size) sculptures, many molds are needed to recreate the original sculpture.
3. Wax. Once the plaster and latex mold is finished, molten wax is poured into it and swished around until an even coating, usually about 1/8 inches thick, covers the entire inner surface of the mold. This must be done in several layers until desired thickness is reached.
4. Removal of wax. This new, hollow wax copy of the original artwork is removed from the mold. The artist may reuse the mold to make more wax copies, but wear and tear on the mold limit their number. For small bronze artworks, a common number of copies today is around 25.
5. Chasing. Each hollow wax copy is then "chased": a heated metal tool is used to rub out all the marks which show the "parting line" or "flashing" where the pieces of the mold came together. The wax is then "dressed" to hide any imperfections. The way the wax looks at this stage, is what it will look like when it is cast. Wax pieces that were molded separately can be heated and attached; foundries often use "registration marks" to indicate exactly where they go.
6. Spruing. Once the wax copy looks just like the original artwork, it is "sprued" with a treelike structure of wax that will eventually provide paths for molten bronze to flow, while allowing air to escape. The carefully-planned spruing usually begins at the top with a wax "cup," which is attached by wax cylinders to various points on the wax copy.
7. Slurry. A "sprued" wax copy is dipped into a slurry of liquid silica, then into a sand-like "stucco", or dry crystalline silica of a controlled grain size. The slurry and grit combination is called "ceramic shell" mold material, although it is not literally made of ceramic. This shell is allowed to dry, and the process is repeated until a half-inch thick or thicker dries coating covers the entire piece. The bigger the piece, the thicker the shell needs to be. Only the inside of the cup is not coated, and the cup's flat top serves as the base upon which the piece stands during this process.
8. Burnout. The ceramic shell-coated piece is placed cup-down in a kiln, whose heat hardens the silica coatings into a shell, and the wax melts and runs out. The melted wax can be recovered and reused, although often it is simply combusted by the burnout process. Now all that remains of the original artwork is the negative space, formerly occupied by the wax, inside the hardened ceramic shell. The feeder and vent tubes and cup are now hollow, also.
9. Testing. The ceramic shell is allowed to cool, then is tested to see if water will flow through the feeder and vent tubes as necessary. Cracks or leaks can be patched with thick refractory paste. To test the thickness, holes can be drilled into the shell, then patched.
10. Pouring. The shell is reheated in the kiln to harden the patches, then placed cup-upwards into a tub filled with sand. Bronze is melted in a crucible in a furnace, then poured carefully into the shell. If the shell were not hot, the temperature difference would shatter it. The bronze-filled shells are allowed to cool.
11. Release.The shell is hammered or sand-blasted away, releasing the rough bronze. The spruing, which are also faithfully recreated in metal, are cut off, to be reused in another casting.
12. Metal-chasing. Just as the wax copies were "chased," the bronze copies are worked until the telltale signs of casting are removed, and the sculptures again look like the original artwork. Pits left by air bubbles in the molten bronze are filled, and the stubs of spruing filed down and polished.
13. Patinating. The bronze is colored to the artist's preference, using chemicals applied to heated or cooled metal. Using heat is probably the most predictable method, and allows the artist to have the most control over the process. This coloring is called patina, and is often green, black, white or brownish to simulate the surfaces of ancient bronze sculptures. (Ancient bronzes gained their patinas from oxidisation and other effects of being on Earth for many years.) However, with current artistic trends in the United States, many artists prefer that their bronzes have brighter, more stylized patinas. Patinas can be applied to replicate marble or stone. Depending on how the metal is prepared, either sandblasted or polished, the finish can be either opaque or transparent. After the patina is applied, a coating of wax, which is the most traditional type of sealer, is usually applied to protect the surface. Many artists prefer to use lacquer as a sealer on some of the more unstable patinas. This protects the piece more from ultraviolet rays. Some patinas change color over time because of oxidiation, and the wax layer slows this down somewhat.
On the left is an example of a lost-wax process mold, and on the right is the resulting bronze sculpture.
On the left is an example of a lost-wax process mold, and on the right is the resulting bronze sculpture.
The lost-wax process can also be used with any material that can burn, melt, or evaporate to leave a mold cavity. Some automobile manufacturers use a lost-foam technique to make engine blocks. The model in this case is made of polystyrene foam, which is then placed into a casting flask, consisting of a cope and drag, which is then filled with casting sand. The foam supports the sand, allowing shapes to be made which would not be possible if the process had to rely on the sand alone to hold its shape. The metal is then poured in, and the heat of the metal vaporizes the foam as the metal enters the mold.
2007年10月9日星期二
Celebrations of 60th Anniversary of Roller Bearings Manufacture in Brno
On the occasion of 60th anniversary of roller bearings manufacture start in Brno there has been held the meeting of ZKL Group management with representatives of Czech political life and with important business partners on September 21, 2007.
As a part of gala program the new Commercial and Technical Centre of ZKL has been officially opened. Cutting of the tape was performed by ZKL General Manager Mr. Jiri Prasil, Eng. CSc. (on first photograph, right) jointly with Brno city Lord Mayor Mr. Roman Onderka. It was followed by press conference, inspection of new premises and of ZKL Brno a.s. plant production site.
The afternoon and evening program was prepared for invited guests at Mikulov castle with accompanying program showing the guests the life in 15th century castle life.
As a part of gala program the new Commercial and Technical Centre of ZKL has been officially opened. Cutting of the tape was performed by ZKL General Manager Mr. Jiri Prasil, Eng. CSc. (on first photograph, right) jointly with Brno city Lord Mayor Mr. Roman Onderka. It was followed by press conference, inspection of new premises and of ZKL Brno a.s. plant production site.
The afternoon and evening program was prepared for invited guests at Mikulov castle with accompanying program showing the guests the life in 15th century castle life.
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