Cast & Forged

investment casting ledger end scaffolding accessories for scaffolding.
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Specifications:
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Technical?Parameter?for prop nut | Process | Precision?cast?steel |
Size | Based?on?customer?drawings |
Weight | 3KG |
Material | Cast?steel |
Surface?treatment | Cold galvanizing |
Tolerance | 0.2mm |
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Description:
Investment casting is an industrial process based on and also called lost-wax casting, one of the oldest
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known metal-forming techniques.From 5,000 years ago, when beeswax formed the pattern, to today’s high-
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technology waxes, refractory materials and specialist alloys, the castings allow the production of
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components with accuracy, repeatability, versatility and integrity in a variety of metals and high-
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performance alloys. Lost-foam casting is a modern form of investment casting that eliminates certain steps in the process.
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There are a variety of materials that can be used for the investment casting process, including stainless
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steel alloys, brass, aluminum, and carbon steel. The material is poured into a ceramic cavity designed to
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create an exact duplicate of the desired part. Investment casting can reduce the need for secondary
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machining by providing castings to shape.
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Casts can be made of the wax model itself, the direct method; or of a wax copy of a model that need not be
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of wax, the indirect method. The following steps are for the indirect process which can take two days to one
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week to complete.
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Produce a master pattern: An artist or mould-maker creates an original pattern from wax, clay, wood,
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plastic, steel, or another material.
Mouldmaking: A mould, known as the master die, is made of the master pattern. The master pattern may
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be made from a low-melting-point metal, steel, or wood. If a steel pattern was created then a low-melting-
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point metal may be cast directly from the master pattern. Rubber moulds can also be cast directly from the
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master pattern. The first step may also be skipped if the master die is machined directly into steel.
Produce the wax patterns: Although called a wax pattern, pattern materials also include plastic and frozen
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mercury. Wax patterns may be produced in one of two ways. In one process the wax is poured into the
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mold and swished around until an even coating, usually about 3 mm (0.12 in) thick, covers the inner surface
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of the mould. This is repeated until the desired thickness is reached. Another method is filling the entire
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mould with molten wax, and let it cool, until a desired thickness has set on the surface of the mould. After
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this the rest of the wax is poured out again, the mould is turned upside down and the wax layer is left to
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cool and harden. With this method it is more difficult to control the overall thickness of the wax layer.
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If a core is required, there are two options: soluble wax or ceramic. Soluble wax cores are designed to melt
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out of the investment coating with the rest of the wax pattern, whereas ceramic cores remain part of the
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wax pattern and are removed after the workpiece is cast.
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Assemble the wax patterns: The wax pattern is then removed from the mould. Depending on the
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application multiple wax patterns may be created so that they can all be cast at once. In other applications,
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multiple different wax patterns may be created and then assembled into one complex pattern. In the first
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case the multiple patterns are attached to a wax sprue, with the result known as a pattern cluster, or tree;
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as many as several hundred patterns may be assembled into a tree. Foundries often use registration marks
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to indicate exactly where they go.The wax patterns are attached to the sprue or each other by means of a
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heated metal tool.The wax pattern may also be chased, which means the parting line or flashing are rubbed
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out using the heated metal tool. Finally it is dressed, which means any other imperfections are addressed
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so that the wax now looks like the finished piece.
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Investment: The ceramic mould, known as the investment, is produced by three repeating steps: coating,
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stuccoing, and hardening. The first step involves dipping the cluster into a slurry of fine refractory material
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and then letting any excess drain off, so a uniform surface is produced. This fine material is used first to
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give a smooth surface finish and reproduce fine details. In the second step, the cluster is stuccoed with a
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coarse ceramic particle, by dipping it into a fluidised bed, placing it in a rainfall-sander, or by applying by
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hand. Finally, the coating is allowed to harden. These steps are repeated until the investment is the
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required thickness, which is usually 5 to 15 mm (0.2 to 0.6 in). Note that the first coatings are known as
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prime coats. An alternative to multiple dips is to place the cluster upside-down in a flask and then liquid
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investment material is poured into the flask. The flask is then vibrated to allow entrapped air to escape and
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help the investment material fill in all of the details.Common refractory materials used to create the
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investments are: silica, zircon, various aluminium silicates, and alumina. Silica is usually used in the fused
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silica form, but sometimes quartz is used because it is less expensive. Aluminium silicates are a mixture of
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alumina and silica, where commonly used mixtures have an alumina content from 42 to 72%; at 72%
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alumina the compound is known as mullite. During the primary coat, zircon-based refractories are
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commonly used, because zirconium is less likely to react with the molten metal.Chamotte is another
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refractory material that has been used. Prior to silica, a mixture of plaster and ground up old molds was
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used.The binders used to hold the refractory material in place include: ethyl silicate (alcohol-based and
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chemically set), colloidal silica (water-based, also known as silica sol, set by drying), sodium silicate, and a
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hybrid of these controlled for pH and viscosity.
Dewax: The investment is then allowed to completely dry, which can take 16 to 48 hours. Drying can be
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enhanced by applying a vacuum or minimizing the environmental humidity. It is then turned upside-down
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and placed in a furnace or autoclave to melt out and/or vaporize the wax. Most shell failures occur at this
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point because the waxes used have a thermal expansion coefficient that is much greater than the
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investment material surrounding it, so as the wax is heated it expands and induces great stresses. In order
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to minimize these stresses the wax is heated as rapidly as possible so that the surface of the wax can melt
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into the surface of the investment or run out of the mold, which makes room for the rest of the wax to
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expand. In certain situations holes may be drilled into the mold beforehand to help reduce these stresses.
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Any wax that runs out of the mold is usually recovered and reused.
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Burnout & preheating: The mold is then subjected to a burnout, which heats the mold between 870 °C
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and 1095 °C to remove any moisture and residual wax, and to sinter the mold. Sometimes this heating is
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also used as the preheat, but other times the mold is allowed to cool so that it can be tested. If any cracks
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are found they can be repaired with ceramic slurry or special cements. The mold is preheated to allow the
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metal to stay liquid longer to fill any details and to increase dimensional accuracy, because the mold and
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casting cool together.
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Pouring: The investment mold is then placed cup-upwards into a tub filled with sand. The metal may be
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gravity poured, but if there are thin sections in the mold it may be filled by applying positive air pressure,
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vacuum cast, tilt cast, pressure assisted pouring, or centrifugal cast.
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Divesting: The shell is hammered, media blasted, vibrated, waterjeted, or chemically dissolved (sometimes
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with liquid nitrogen) to release the casting. The sprue is cut off and recycled. The casting may then be
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cleaned up to remove signs of the casting process, usually by grinding.

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In order to develop and maintain our reputation as a world class supplier to OEM manufacturers globally,

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we have invested heavily in quality, service, technology and people. We are an ISO 9001:2000 certified

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company and as such have documented


procedures and practices to ensure the highest levels of service to our customers. As a result of our rapid

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and continued growth,


we have expanded our management and technical teams and ensure that they are trained in the latest

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technologies and foundry practices.Our management and engineering teams receive continuous upgrading

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at schools such as the Beijing Qinghua University and various foundry colleges in the region. We are also

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dedicated to providing our workers with regular classes taught by qualified instructors on the many varied

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foundry practices and procedures we use at GSC.

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Every new casting that GSC produces is studied extensively for form, function and finish before we ever cut

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any wood or pour plastic for the pattern. We feel that a commitment to detailed planning, involvement of our

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customer in the planning procedures and choosing the appropriate foundry methoding, not only greatly

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reduces lead times for accurateand high quality prototypes, but also results in high quality production

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castings. It has also proven to reduce the time from concept (drawing) to production castings.

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OEM Service

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We provide OEM service for all of our clients,we will manufacture strictly based on your drawings.

Please send us your drawings or inquiry