Elements of the gating system. Gating system: purpose, elements, types. Vertical slot gating system

Purpose Gating system- ensuring optimal conditions and duration of mold pouring in order to obtain a casting with clear edges and contours, preventing the entry of non-metallic inclusions (when pouring from a rotary ladle), and during solidification of the alloy - feeding the casting to prevent shrinkage cavities. Elements Gating system in accordance with their purpose, they are divided into supply and supply (in some special cases such a division does not exist).

Purpose of the gating system

Gating system- this is a system of channels and reservoirs for supplying molten metal to the cavity of the casting mold, filling it and feeding the casting during solidification. The gating system must ensure filling of the casting mold at the required speed, retention of slag and other non-metallic inclusions, release of vapors and gases from the mold cavity, and continuous supply of metal to the hardening casting. After casting is completed, the excess metal filling the gating system solidifies, maintaining the shape of its channels and forming waste that must be separated from the casting itself.

Rice. 33L. Gating system

1 – sprue bowl; 2 – riser; 3 – slag catcher; 4 – feeder; 5 – thrust; 6 – profit.

The main elements of the gating system (Fig. 33L) are: 1 – sprue bowl (funnel), which is designed to receive a stream of melt flowing from the pouring ladle and partially retain the slag that falls along with the melt; 2 – riser– a vertical or inclined channel that transfers the melt from the gating bowl into the gating system; 3 – slag catcher– a horizontal channel, located, as a rule, in the upper half of the mold and serves to retain slag and transfer the melt from the riser to the feeders; 4 – feeder– a channel that supplies the melt directly into the mold cavity (there can be one or several feeders, and they are usually located in the lower half of the mold); 5 – whipping– a vertical channel for removing gases from the mold cavity, signaling the end of pouring, and feeding the casting with melt during solidification; 6 – profit– a reservoir with molten metal, ensuring its continuous supply to the massive part of the casting, which solidifies last (if there are several massive parts, there may also be several profits).

Question 31. Production of castings using lost wax models. The essence of the method. Model compositions. Molding materials. Sequence of operations of the investment casting process. Advantages and disadvantages of the method.

Production of castings using lost wax casting This is a method of producing castings made using disposable casting molds that do not have a parting plane, the working cavity of which is obtained using low-melting models - for the production of low-melting models, it is necessary to use a steel one-piece mold, the internal cavity in which is made taking into account the allowance for fur. Processing and linear shrinkage of alloys.

Recently, new model compositions of paraffin-polyethylene, ceresin-polyethylene and paraffin-ceresin-polyethylene have been proposed.

Low-melting model compositions (paraffin, stearin, ceresin, etc.) are prepared in water, glycerin or oil baths with electric or gas heating; Thermostat baths are also used.

Paste-like model compositions are prepared manually on a small scale of production, on a larger scale - on special installations

Model compositions with a high melting point (rosin, polystyrene, etc.) are produced in special rotary electric furnaces equipped with thermostats.

The methods for making models are varied. Model composition introduced into the mold cavity using the following methods: free pouring, pressing in a paste state; filling under pressure; pressing under high pressure of powder or granules heated to a softening state of model compositions such as plastics

As a molding compound The fireproof components used are sand as a binder, a hydrolyzed solution of ethyl silicate, wax with the addition of brown coal.

To produce a shell of a ceramic gating mold, a block consisting of models and a gating system is immersed in a suspension (sand + hydrolyzed ethyl silicate solution) followed by sprinkling of each intermediate layer (5-7 times)

The low-melting side is removed from the mold by immersing the structure in hot water. The resulting mold is placed in a flask (frame) located on a pallet, strengthened with sand and kept in an oven at a high temperature of 950 degrees for a long time, after which the hot casting mold is filled with a melt, the casting is removed from the mold by destroying it mechanically or chemically. The volume of fur processing is reduced by 2.

Disadvantages - 1) the longest and most expensive 2) limitation of the range and weight of the products produced 3) the use of difficult mass production is advisable to use in the manufacture of high-alloy steels.

Question 32. Production of castings in shell molds. The essence of the method. Foundry equipment. Molding mixtures. The sequence of making castings by casting into shell molds. Advantages and disadvantages of the method.

The method of casting into shell molds is based on obtaining one-time half-molds and cores in the form of shells with a thickness of 6-10 mm. They are made by curing a layer of a mixture on a metal tooling, in which the binder, when heated, first melts and then hardens (irreversibly), giving the shell high strength.

Essence of the process consists in the use of thin-walled detachable one-time molds made from molding sand. Molding sands are made from fine-grained quartz sand mixed with thermosetting resin. The model plate is heated to a temperature of 200-250 degrees. A release agent is applied to its surface. The molding mixture is applied to the model plate and held for 10-30 seconds; from the heat of the model slab, the thermosetting resin turns into a liquid state, gluing sand grains to form a sand-resin shell form (5-10 mm thick) depending on the exposure time. At the same time, the resin hardens. The finished shell forms are removed from the metal model and, if they are detachable, they are glued together. Metal is poured into the assembled shell molds. Ribbed cylinders, crankshafts, etc. are produced by casting into shell molds. The method is used for steel and aluminum castings of simple configuration without internal cavities in mass production. The molding mixture consists of fine-grained sand (grain size 0.25...0.06 mm) and thermosetting resin - pulverbakelite. The method ensures surface roughness Rz = 80...40 μm, and accuracy - 12...14 quality. The method can be easily mechanized and automated.

Foundry technological equipment (model-flask set).

A model kit is a set of technological equipment adapted and instrumentally necessary for the manufacture of cast molds and cores. The model kit includes model castings and model plates, core boxes, and flasks.

Model casting is a device with the help of which a cavity with a shape and size corresponding to the shape and dimensions of the future casting is obtained in a casting mold. The surface of the model must be smooth and clean so that when it is removed from the mold, it can easily separate from the mold material. All dimensions of the model must be increased by the amount of shrinkage of the vertical surfaces of the model. They provide a slope to make it easier to remove the model from the mold.

Model plate – a plate on which the model and system element are fixed during the manufacture of a casting mold.

A core box is a device in which cores are made. They are either solid or split. To lighten the finished core, the vertical surfaces of core boxes are made of wood and metals.

A flask is a wooden or metal frame (box without a bottom) in which the molding sand is compacted when making a casting mold from a sandy clay mixture.

Molding sand contains filler - fine-grained quartz sand - 100%: binder - pulverbakelite (phenol-formaldehyde resin with urotropine additives) - 6 - 7%; humidifier (kerosene, glycerin) - 0.2 - 0.5%; solvent (acetone, ethyl alcohol) - up to 1.5%.

The sequence of manufacturing half-molds is shown in Fig. 39. The metal model with elements of the gating system is fixed on the model plate, heated to a temperature of 200 - 250 o C and a sand-resin mixture is poured. The resin melts, glues the grains of sand and after 15 - 25 s on the model (Fig. 39, A) a semi-solid shell 6–12 mm thick is formed. When turning the model plate 180 o (Fig. 39, b) the remaining mixture falls off. Then the model plate with the shell is placed in an oven, where the final hardening of the shell occurs at a temperature of 280 - 320 ° C for 2 - 3 minutes. After removal from the oven, the shell (half-mold) is removed from the model using pushers (Fig. 39, V). Sand-resin rods for hollow castings are made in a similar way.

When assembling the mold, a rod is installed and the half-forms are aligned along the protrusions and depressions on them. The half-forms are fastened with metal staples, clamps or gluing (Fig. 39, G). The assembled mold is placed in a flask and covered with dry sand or metal shot from the outside (Fig. 39, d) and pour the melt. After the casting has hardened (Fig. 39, e) shell form is easily destroyed.

Crankshafts, camshafts, connecting rods, cylinders with stiffeners and other parts are produced by casting into shell molds.

Advantages of the shell mold casting method: the ability to obtain thin-walled castings of complex shapes; smooth and clean surface of castings; low mixture consumption; high-quality metal structure due to increased gas permeability of the molds; wide possibility of automation; small tolerances for cutting processing. Disadvantages: limited size of castings (up to 1500 mm); high cost of mixtures; release of harmful vapors and gases from mixtures during the manufacture of molds.

Question 33. Production of castings by chill casting. The essence of the method. Types of molds and materials for their manufacture. Sequence of making castings by chill casting. Advantages and disadvantages of the method.

Chill casting is a method of producing castings using metal reusable molds. For the manufacture of molds, the following structural materials are used (gray cast iron, high-strength, malleable, carbon, alloy steels, aluminum casting alloys

The method of manufacturing a chill mold is casting into sand and clay molds with subsequent further processing of the working cavity of the chill mold.

The essence of the method is the use of a reusable casting mold, which forms the configuration and properties of the casting. With this casting method, the use is either completely eliminated, or a small amount of sand mixtures is used only for the production of one-time cores. In this regard, there is no need for land preparation departments.

According to the design, the mold can be one-piece, shaken out, or detachable.

Filling of the melt mold is carried out by free pouring under the influence of gravity or gravitational forces.

The internal cavities of the casting are obtained using non-metal or shell rods

The technology for producing castings is more complex because the thermal conductivity of the chill mold is high; in order to obtain high-quality castings of the required shape, it is necessary to maintain the fluidity of the melt; before pouring, the melt is overheated to a higher temperature and the chill mold is heated with the flame of gas burners and the working surface of the chill mold is coated with refractory compounds in order to obtain a good quality casting .

The die is not malleable, so the metal rod and casting are removed from the die earlier, that is, before the casting cools down to the ambient temperature.

Temperature at which the casting is removed from the mold 0.6 t melting

For extraction from the mold, the mold is equipped with ejectors

Advantages: multi-level use, the volume of machining is doubled on the surface of the casting, there are castings free from obtaining a denser fine-grained pressure structure and, as a result, higher mechanical properties

Disadvantages 1) limited product range 2) mass production is rare. 3) it is advisable to use a die made of color alloys 4) the duration of the die manufacturing process

Question 34. Production of castings by injection molding. The essence of the process and process diagram (with cold and hot pressing chambers). Sequence of production of injection molded castings. Advantages and disadvantages of the method.

Injection molding is a method of producing shaped castings in metal molds, in which the mold is forcibly filled with metal under pressure. This method is used in mass production for thin-walled castings from non-ferrous metal alloys (Recently, this casting method has also begun to be used for ferrous metals). This method ensures greater dimensional accuracy of castings; in the vast majority of cases, the latter do not require further mechanical processing.

The essence of injection molding

Performed by machine into metal forms called molds. Filling of the mold with metal is carried out after it is closed through the gating channels, which connect the working cavity of the mold with the compression chamber of the injection molding machine. The outer contours of the casting are formed by the working surface of a closed mold, and the internal holes and cavities are obtained using metal rods, which are removed from the solidified casting at the moment the mold is opened. The rods are mechanically driven in the form of racks, gears, toothed sectors, wedges, eccentrics, kinematically connected to the mold opening mechanism.

Figure 4.1 – Scheme of the technological process of injection molding on a machine with a cold pressing chamber: a – supply of the melt to the pressing chamber; b – pressing; c – opening of the mold; d – pushing out the casting; 1 – mold; 2 – press piston; 3 – pressing chamber; 4 – rod; 5 – pusher

The metal is poured into the pressing chamber and pressed inside the working cavity of the mold. After crystallization of the casting, the mold opens to remove the casting, while a separate part remains motionless, and the remaining parts are removed by a hydraulic drive. The casting is held in the movable part and moves with it until it contacts the ejectors, which push the casting out of the movable part of the mold. The casting can be removed from the opened mold using a manipulator or robot. To prevent welding of the working surface of the mold with the casting and to facilitate removal of the casting, the mold cavity is coated with compounds in the form of pastes or spray liquids containing metal powders, graphite, and molybdenum sulfide.

On machines with a cold pressing chamber, after preparing the mold 1 (Figure 4.1, a) for the next cycle, assembling it and locking it using the locking mechanism of the casting machine, a dose of melt is supplied to the pressing chamber 3. Then, under the action of the press piston 2, moving in this chamber through the pressing mechanism, the melt fills the working cavity of the mold through the channels of the gating system (Figure 4.1, b). After the casting has solidified and cooled to a certain temperature, the rods 4 are removed and the mold is opened (Figure 4.1, c), and then the casting is removed from the mold using the ejection mechanism and pushers 5 (Figure 4.1, d). The machine's mechanisms return to their original state. The sprues and fills are separated from the casting, usually using a trimming press located near the casting machine, or by mold mechanisms. This completes the working cycle.

The main advantages of injection molding include:

· versatility in terms of types of processed plastics,

· high performance,

· high quality of the resulting products,

· the ability to manufacture parts of very complex configurations or thin-walled products,

· no additional processing of the final product (except for the operation of removing the gates),

· full automation of the process.

Disadvantages of the method:

· injection molding machines are complex and expensive devices, rich in modern technical solutions;

· the use of injection molding machines for the implementation of a specific technological process requires a qualified feasibility study.

Types of gating systems

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Foundry

Types of gating systems

A gating system is a set of channels and reservoirs through which liquid metal from a ladle enters the cavity of the casting mold. The gating system has a significant impact on the quality of castings; If it is incorrectly designed or calculated incorrectly, it can cause defective castings.

The main elements of the gating system are the following.

A sprue funnel or bowl is a reservoir designed to receive liquid metal from a ladle, partially retain the slag (in the bowl) and transfer the metal to the riser.

A riser is a vertical (sometimes inclined) channel of a round, oval or other cross-section, designed to transfer metal from a bowl (funnel) to other elements of the gating system (slag catcher, feeders).

Rice. 1. Gating system elements

The gate passage, called a “slag catcher” for iron castings and a manifold for non-ferrous castings, is a horizontal channel designed to retain the slag and transfer the riser metal to the feeders.

Feeders (runners) are channels designed to transfer metal directly into the mold cavity.

Rice. 2. Types of gating systems: 1 - bowl (funnel); 2 - riser; 3 - gate stroke; 4 - feeder; 5 - thrust; 6 - casting

Gating systems are divided into five main types:
1. Upper gating system (Fig. 2, a). Feeders are supplied either to the upper part of the casting, or to the profit or below the profit.
2. Lower or siphon gating system (Fig. 2, b). Feeders are brought into the lower part of the casting.
3. Side gating system (Fig. 2, c). Feeders are supplied through the mold connector.
4. Tiered (story) gating system (Fig. 2, d). Feeders are connected to the casting at several levels. A variation of the tiered gating system is the vertical slot system (Fig. 2, e).
5. Rain gating system.

The casting system is selected depending on the type of metal, the design of the casting, its position during pouring, etc.

We always strive to ensure that, while ensuring the required quality of the casting, the metal consumption for the gating system is minimal. If this condition is met, the yield of suitable casting increases (the ratio of metal consumption for casting to the total metal consumption, taking into account the gating system and profits).

The upper gating system is the simplest in design, easy to implement, and requires little metal consumption. It creates the most favorable conditions for feeding the casting, i.e. creates the temperature distribution necessary for directional crystallization - an increase in temperature from the bottom of the casting to the top.

However, the upper gating system has a significant drawback, namely, when a metal jet falls from a great height, the shape is washed out and blockages form; the metal oxidizes, spatters, and the number of non-metallic inclusions in it increases. In addition, the upper gating system does not provide slag retention. Therefore, it is used for low castings of small mass, simple configuration, with small and medium wall thickness.

The lower (siphon) gating system ensures smooth filling of the mold, eliminating the risk of washing out the walls and causing blockages. However, the lower supply of metal creates an unfavorable temperature distribution throughout the volume of the casting metal (since the hot metal comes from below) and contributes to the development of local heating and internal stresses.

The siphon gating system is difficult to manufacture and requires increased metal consumption; it is usually used for medium and heavy castings of considerable height and large wall thickness.

Supplying metal through a joint is one of the most common methods of filling molds for various castings, especially castings whose symmetry plane coincides with the plane of the mold parting.

The side gating system, while reducing (compared to the top) the height of metal fall and the possibility of mold destruction, at the same time worsens the crystallization conditions and increases metal consumption. It is used for castings of small height, medium weight, large sizes; widely used in machine mold making.

The tiered gating system is used for large, heavy castings. It provides better feed to the casting than a siphon gating system. The tiers of the system must feed metal into the mold cavity sequentially, from bottom to top. The tiered gating system is the most difficult to implement and requires the greatest metal consumption. The vertical-slot gating system, which ensures smooth filling of the mold while maintaining the direction of solidification, is used for casting non-ferrous alloys.

The rain gating system is mainly used for cylindrical castings. The metal from the riser enters the ring collector, from which, through feeders located around the circumference at an equal distance from each other, it evenly fills the mold cavity located below in thin streams. The metal should not splash, since drops of metal quickly harden, oxidize and do not weld with the base metal, forming defects in castings called queens,

In addition to choosing the type of gating system, the choice of the location for supplying the feeders to the casting is of great importance. Depending on the properties of the alloy, the design of the casting (overall dimensions, wall thickness), when supplying metal, they strive to ensure either directional solidification or simultaneous uniform cooling of various parts of the casting.

For castings with thick walls, massive units, prone to the formation of shrinkage cavities, it is necessary to create conditions for directed crystallization. This is achieved not only by the appropriate location of the casting in the mold, when the more massive parts are located above the thin ones, but also by the appropriate supply of metal to the most massive parts of the casting. This supply of metal enhances the effect of directional solidification. Therefore, steel, which has high shrinkage and reduced fluidity, is brought into the thick section under the profit in order to heat the mold near the profit and improve the nutrition of the solidifying casting. Also used in the manufacture of castings from special bronzes, brass, and some aluminum alloys. Sometimes steel is poured directly through the profits.

However, if, due to an excessively large difference in the cooling rates of individual parts of the casting, there is a danger of stresses and cracks, then to reduce the difference in cooling rates, the metal is brought into less massive parts of the casting.

Simultaneous and uniform solidification and cooling of the casting is achieved by supplying metal to the thin parts of the casting and the appropriate arrangement of feeders, ensuring symmetrical and uniform filling of the mold. This reduces the risk of internal stresses, warping and cracks. A similar supply of metal is used in the manufacture of long castings with walls of varying thickness.

Tapered gating systems better capture slag, reduce air injection, and increase the linear speed of metal passage through the channels of the gating system. They are used in the casting of alloys that are not prone to oxidation and form weak oxide films.

Expanding gating systems reduce the speed of metal movement and ensure smooth filling of the mold cavity without metal oxidation. They are used in the casting of alloys prone to oxidation, forming strong oxide films.

Gating system

a set of channels (elements) through which the melt from a ladle or other casting device is supplied to the working cavity of the casting mold (See Casting mold). Purpose of L. s. - ensuring optimal conditions and duration of mold pouring in order to obtain a casting with clear edges and contours, preventing the entry of non-metallic inclusions (when pouring from a rotary ladle), and during solidification of the alloy - feeding the casting to prevent shrinkage cavities. Elements of HP in accordance with their purpose, they are divided into supply and supply (in some special cases such a division does not exist).

To the supply elements of HP. include: bowl, riser, choke, slag catcher (manifold, gating passage) and feeder ( rice. , A). The melt receiver bowl must contain a sufficient volume of metal for ease of pouring, retention of slag and prevention of air intake. A riser is a vertical (rarely inclined) channel connected to a bowl. Throttle - a narrow channel (or several channels), usually located at the base of the riser, which is a local hydraulic resistance, regulates the filling speed and eliminates vacuum (vacuum) in the riser. A slag trap is a channel, usually of an elongated trapezoidal cross-section, located behind the throttle, used to supply the alloy to the feeders and retain non-metallic inclusions. For more complete retention of slag in HP. arrange local expansions in the slag catcher, use centrifugal slag catchers, filter meshes (for castings made of cast iron - from refractory rod or fireclay mixture, for castings from non-ferrous alloys - from thin sheet steel, for all alloys with a pouring temperature of up to 1350 ° C - from silica fabric ). Slag traps are not needed when pouring molds from a stop ladle (the slag remains in the ladle) and when the density of non-metallic inclusions is close to the density of the alloy (for some non-ferrous alloys). In these cases, a channel called a manifold or runner only distributes the alloy. Feeder is a channel connected to the slag catcher, usually of rectangular cross-section, through which the alloy enters the working cavity of the mold directly or through the profit.

The dimensions of the supply elements are determined mainly by hydrodynamic factors (the design of the HP, pressure, flow rate, and melt velocity).

To the power supply elements of HP. include lateral profit and neck ( rice. , A). Side profit is a compact tide on the side surface of the casting, designed to feed it during cooling and solidification of the alloy. The neck is the narrowed part of the profit that connects it with the casting. The feed elements must harden more slowly than the casting. Their dimensions are determined mainly by thermal factors (thermophysical properties of the alloy and mold), casting properties of the alloy, mass, wall thickness, casting configuration and requirements for it (mechanical properties, tightness, etc.).

When producing thin-walled castings from eutectic alloys (for example, gray cast iron), a short cooling time of the feeders is usually sufficient to feed the castings. In these cases, special power supply elements are not needed and HP. consists only of supply channels ( rice. , b, c, d, e). If a small volume of alloy is required for supply, then the system, along with supply elements, has supply and supply elements, for example, a slag catcher can simultaneously serve as a profit, and a feeder as a neck ( rice. , e).

Depending on the method and place of supply of HP. divided into side, top and rain, siphon, tiered (storey) and slotted. According to the method of molding, horizontal blades are distinguished. with the feeder located in the horizontal plane of the connector and vertical, in which the feeder is located in the vertical plane of the connector or outside the main plane of the mold connector.

Lit.: Dubitsky G.M., Gating systems, M. - Sverdlovsk, 1962; Rabinovich B.V., Introduction to foundry hydraulics, M., 1966; Basic principles of gating, L. - , 1967; Leremplissage des ernpreintes de moules en sable, P., 1966; Hoizmüller A., ​​Kucharcik L., Atlas zur Anschnitt- und Speisertechnik für Guβeisen, Düsseldorf, 1969.

B.V. Rabinovich.

Gating systems: a, b - side; c - rain; g - siphon; d - tiered (storey); e - slotted; 1 - bowl (funnel); 2 - riser; 3 - throttle; 4 - slag catcher; 5 - feeder; 6 - side profit; 7 - neck.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what a “Gating system” is in other dictionaries:

Gating system, Gating feed system is a system of channels and cavities in a mold through which liquid molten material melt (metal or plastic) is fed into the cavity of an injection mold or injection mold. Elements ... Wikipedia

GUTTER SYSTEM- a system of channels and elements of a casting mold for supplying molten metal to the mold cavity, ensuring its filling and feeding the casting during solidification. Depending on the location in the mold and the method of supplying metal, gatings are distinguished... ... Metallurgical dictionary

Gating system- a system of channels and elements of a casting mold for supplying molten metal into the mold cavity, ensuring its filling and feeding the casting during solidification. Depending on the location in the mold and the method of supplying metal, a gating system is distinguished... ...

gating system- A system of channels and devices for supplying liquid metal (alloy) in a certain mode to the mold cavity, separating non-metallic inclusions and providing power to the casting during solidification. Note According to the design of gating systems... ... Technical Translator's Guide

GUTTER SYSTEM- a set of reservoirs, vertical and horizontal channels that serve to receive and fill the working cavity of the foundry (see) with molten metal, feed (see) during its solidification, as well as to catch the first portions of metal, filter ... Big Polytechnic Encyclopedia

gating system- a system of channels and devices for supplying liquid metal to the cavity of the casting mold, separating non-metallic inclusions and feeding the casting during solidification. The gating system consists of a sprue bowl or pouring funnel,... ... Encyclopedic Dictionary of Metallurgy

A set of channels and cavities (elements) that serve to fill the working cavity of the melt mold. metal, feeding the casting during solidification, trapping the first portions of metal, slag and contaminants. Basic elements of HP (bowl, riser,... ... Big Encyclopedic Polytechnic Dictionary

GREENING SYSTEM BY CONNECTOR- gating system with metal supply along the parting plane. GOST 18169 86 ... Metallurgical dictionary

HORIZONTAL GUTTER SYSTEM- gating system with feeders located in the horizontal plane of the mold connector (Fig. D 14). GOST 18169 86. gating system of simple design WIDTH=391 HEIGHT=281 BORDER=0> gating system with inlet and supply systems... ... Metallurgical dictionary

Vertical gating system- gating system with feeders located in the vertical plane of the mold partition at several levels or vertically. The vertical gating system is divided into upper, rain, siphon, tiered... Encyclopedic Dictionary of Metallurgy

Depending on the size, configuration and material of the product being cast, the gating system in the mold can be horizontal, top, rain, siphon and tiered. Let's consider several types of gating systems used in the casting of artistic and architectural products.

Horizontal gating system (Fig. 3.47, A) with feeders located in a horizontal plane, ensures the supply of metal into the mold cavity through its connector. This gating system has all the main elements and is used in molds that are poured in a raw form with a cavity depth in the lower flask of up to 200 mm. Thin-walled openwork castings (vases, dishes, plates, brackets) with insignificant wall thickness have a complex surface. It is not possible to qualitatively fill the casting molds of such products through a gating system with a horizontally located feeder on one side of the mold cavity, since the melt in the thin section of the mold cavity quickly cools and does not fill it completely. In such cases, a horizontal gating system with a large number of feeders located along the cavity connector is used for filling (Fig. 3.47, b). To do this, a slag catcher with a triangular cross-section is cut around it in the upper half-mold, and below it, in the lower half-mold around the mold cavity, the required number of feeders is cut out. Metal poured into a mold with such a gating system enters it simultaneously in several places. At the same time, it does not have time to cool and fills well the smallest recesses and protrusions of the complex surface of the cavity.

Siphon gating system (Fig. 3.47, V) - horizontal or vertical - ensures the supply of molten metal into the mold cavity from below. Such a system eliminates the possibility of destruction of the lower surfaces of the mold cavity and splashing of metal when its jet falls to the bottom of the mold. Individual drops of metal do not fuse well with the total mass and form inclusions (kinglets) in the casting. Casting molds for figurines that have a significant height with small transverse dimensions are usually poured in a vertical position. The metal enters the cavity of such molds from below (along the riser to the bottom of the mold), and then passes through a horizontal feeder into the mold cavity and, under pressure in the riser, gradually fills it to the top.

Rice. 3.47.

Upper gating system (Fig. 3.47, G) ensures the supply of metal into the mold cavity from above. In small openwork casting molds, the riser of the upper gating system is made in the form of a slot into the mold cavity from above, which is why it is often called a slot gating system. This gating system is convenient in that it can be placed in the center of the mold cavity, from where the metal spreads evenly to all its parts. In addition, the use of a vertical gating system in thin-walled casting molds is convenient because the cross-section of the slotted riser does not exceed the thickness of the casting, so the riser easily breaks off without destroying the walls of the casting or leaving a large mark on its surface.

Tiered gating system - a vertical gating system - provides metal supply into the mold cavity at several levels of its height. The siphon gating system ensures quiet, consistent filling of the mold, but at the same time it has a significant drawback when casting thin-walled artistic castings. Metal in this form, rising from the bottom up, meeting the cold walls of the mold, cools quickly, poorly fills the upper part of the mold cavity and does not give a sharp relief to the surface of the casting. This drawback can be eliminated if you slightly change the design of the siphon gating system, providing it with additional feeders along the height of the mold. With a tiered gating system, the first portion of metal that enters the mold at the beginning of pouring, having had time to cool somewhat, is heated by a portion of hot metal that arrives at the level of the first additional feeder.

The same thing will happen when the mold is filled to the second feeder. Thus, the upper cold layer of metal in the mold is heated by portions of hot metal coming from tiered feeders. In this case, some equalization of the temperature of the metal in the mold cavity occurs, ensuring the same sharpness of the surface relief of the casting in all its parts.

In casting molds of figurines and busts with a siphon and tiered gating system, it is not possible to install a slag catcher. In such molds, the slag during pouring is held in a sprue bowl, which must have sufficient dimensions and appropriate design to ensure the floating of slag particles during pouring.

When using small sprue bowls (funnels), this is facilitated by a specially made from the core mixture and a dried filter mesh inserted into the bottom of the funnel. If the funnel has a filter mesh, the metal is inhibited in it and fills the funnel. Slag and dirt float to the surface of the metal and remain there until the pouring is completed.

The position of shell forms before pouring can be horizontal or vertical. Vertically poured molds have a number of advantages over horizontal ones, since the sprue bowls in them can be easily made integral with the mold, the riser can be obtained with a normal cone, power can be easily supplied to the lower point of the casting, and pouring vertical molds requires less pouring area. At the same time, the vertical method of filling shell molds also has disadvantages, namely that the shell mold with this filling method experiences high metallostatic pressure, causing burns on the castings due to the penetration of metal into the walls of the mold and deformation, distorting the dimensions of the castings.

Currently, the horizontal method of filling shell molds is most widely used.

Considering that the castings obtained by casting into shell molds have small allowances for machining, great attention should be paid to trapping slags and
other non-metallic inclusions. This is achieved by using slag separating devices in the pouring ladle (ladles with a siphon tube, ladles with locking devices), gating systems with slag catchers and hydraulic locks, or special throttle systems (Fig. 135). For the same purposes, a siphon gating system is used, which is usually used when pouring stack molds (Fig. 136).

Rice. 135. Block of castings of protractor parts, cast into a shell mold using a throttle gating system

Rice. 136. Block of castings of chain links cast into stack molds using a siphon gating system

The relationships between the elements of gating systems for shell casting remain almost the same as for conventional casting and for braking gating systems, and are expressed by the following equations:
for cast iron and non-ferrous castings

The given ratios apply to gating systems in which risers are used with a gating funnel. When using risers with a reverse cone, these relationships remain in force only between feeders and slag traps and do not apply to the riser, the dimensions of which are set locally.

The most effective for use in shell casting are closed profits. When pouring molds horizontally, metal is usually poured not into the sprue bowl, but directly into the central sprue (riser), which is made with a reverse cone.

When producing shells on semi-automatic and automatic machines, a separate method for producing central risers and sprue bowls is used (Fig. 137). Gating