Custom jewelry casting. Custom metal casting

21.02.2021

The investment casting method is widely used in jewelry production. This method makes it possible to serially manufacture products of complex configuration, while ensuring the required accuracy, as well as to obtain thin-walled castings with a deviation from a given size of no more than 0.5% and a surface purity of 5-6 class. This makes it possible to use them as finished jewelry items without additional mechanical processing.

Most often, investment casting is carried out on centrifugal installations, from which the casting method itself received the name - centrifugal casting. Casting can also be carried out on vacuum installations using the vacuum suction method. In this case, the schemes of both technological processes of investment casting (Fig. 28) are identical, only the processes of filling (pouring) the casting mold and the equipment on which this operation is performed are different.

The investment casting method has become widely used even in small jewelry workshops. The equipment used is simple in design, small in size and can be mounted in a production room with an area of \u200b\u200b20-25 m 2. At the same time, even workshops that do not include highly qualified jewelers-fashion designers, by borrowing experience and using ready-made rubber molds, can produce highly artistic products and thus meet the demand of the population.

Manufacturing stages.The main stages in the manufacture of jewelry items using investment models are the manufacture of a reference sample, manufacture of a mold, manufacture of a wax model, preparation of a casting mold, casting jewelry items, cleaning castings.

Starting to develop the design of the product, it is necessary to determine the possibility of its manufacture by the method of centrifugal casting in order to further ensure the execution of mounting and finishing operations.

Sample-referencemust be made of refractory metal 1 (see Fig. 28). It is advisable to make it from the same metal from which products will be serially cast in the future. Models are developed and reference samples are made, as a rule, by highly qualified jewelers. At specialized jewelry enterprises, models are developed by fashion designers.

Figure: 28. Diagram of the technological process of investment casting

A sample-standard of a product or its individual element must be made with high quality, taking into account artistic requirements, and the surface finish must correspond to 8-9 class. When making a reference sample, it is necessary to take into account that the metal will shrink during the subsequent investment casting. Therefore, it is necessary to provide for allowances that are determined empirically, but not more than 5-6% of a given dimensional value.

Getting started making a rubber mold, it is necessary to determine its manufacturability, that is, the convenience of removing the wax model from it. The rubber mold must follow the contour and all the artistic lines of the future jewelry. A rubber mold is made by vulcanizing raw rubber, into which a sample-standard product is placed. The manufacturing technology of a rubber mold depends on the complexity of the product design.

The process of manufacturing a rubber mold for the subsequent casting of wax models of products of complex shapes is as follows. Place a special flask with guide pins on a smooth table surface or base plate with the base down. Then the flask is filled with plasticine, into which the sample-standard product 2 is pressed to half (see Fig. 28). A second one is installed on this flask and it is poured with a liquid gypsum solution. After the gypsum has hardened, the flasks are turned over and the plasticine is removed, while the reference sample remains in the plaster form. Several indentations are made in the plaster, which will be the guides of the rubber mold. The raw rubber is cut into small pieces, which are filled in the upper half of the mold 3.

The flasks are installed on a vulcanizing press 4 and rubber pieces are vulcanized for 45-60 minutes at a temperature of 150-160 ° C. After that, the gypsum is broken, removed and thoroughly cleaned the sample-standard of the product and the rubber half-mold. Then the flask, in which the half-form is located, is laid with the base down and after sprinkling with talcum, the standard sample is placed in the half-form 5. The second upper half of the flask is filled with pieces of crude rubber 6. Next, the second half of the mold is vulcanized and both parts of a rubber mold are obtained. Then, a sample-standard of the product is removed from the rubber mold and the sprue channel 7 is cut in it.

When manufacturing a mold for casting wax models of products of simple shapes, it is enough to place a reference sample between two plates of raw rubber of the corresponding thickness so that when pressed, the sample is completely sunk into the rubber, and vulcanize them under the press. The vulcanization mode is the same as in the first embodiment of the mold production. As a result of vulcanization, the plates are welded together. After the rubber mold has cooled (in water), it is cut along the most favorable parting lines and a reference sample is taken out. During the cutting process, it is necessary to consider how the mold will be released.

For making wax modelsuse injector installation 8 (see Fig. 28). In this case, both a standardized installation of the AML type with a power of 0.5 kW can be used, as well as a non-standardized one, in which the wax is heated to 70-85 ° C and is constantly maintained at this temperature.

Before filling with wax, the mold must be cleaned and lubricated with a solution of glycerin (a mixture of water and glycerin in equal parts) for easier wax separation from the rubber. The mold is filled with wax under a pressure of 1.96-104 ... 7.85X10 4 Pa \u200b\u200b(0.2-0.8 kgf / cm 2), which is created in the tank of the injection unit with compressed air. The liquid wax enters the gating channel of the mold through the fitting and fills it. In this case, the mold must be tightly closed. For this purpose, it is recommended during the filling period to press the mold from both sides along the planes with heat-resistant metal plates (aluminum, brass) in size corresponding to the size of the mold, so that they do not interfere with the access of the mold sprue to the fitting.

After filling with wax, the mold must be cooled either naturally at room temperature or in refrigeration chambers. The cooled mold is opened and the wax model of the product is manually removed from it. In cases where the model sticks to the mold, a thin spatula with a polished blunt blade can be used.

Wax models should be carefully inspected. Models with underfilling are discarded, and those with minor overflows in the form of flash are cleaned, after which all models suitable for further use are placed in a special container to avoid breakage.

Mold preparationis carried out as follows. Finished wax models, in accordance with the capacity of the glass (flask), are set in the shape of a herringbone, by soldering the sprues of the models to a single rod, also made of wax by casting and installed in a rubber shoe (base). Soldering is carried out using a household electric soldering iron. When assembling the herringbone, the models should not be placed close to each other, since during vacuuming they can join, then the castings will be defective.

The collected wax tree is defatted by dipping in alcohol or carbon tetrachloride, and dried naturally. After drying, a glass (flask) is put on the wax tree so that it enters the cylindrical groove of the rubber base, and a previously prepared, evacuated molding mixture is poured into the flask.

To prepare the molding mixture, a molding mass is used, which is a cristobalite-gypsum mixture. Currently, the jewelry industry mainly uses imported molding materials K-90, Supercast and Satinkast. Prepare the molding mixture by adding distilled water to the molding mass and stirring it thoroughly. The estimated amount of the molding compound and distilled water is 0.32-0.42 liters of water per 1 kg of the mixture.

Then the filled flask 9 (see Fig. 28) is evacuated and compacted on a vibration vacuum installation to a residual pressure of 0.98 * 10 4 ... 1.96 * 10 4 Pa \u200b\u200b(0.1-0.2 kgf / cm 2) c within 2-3 minutes, after which the molding mixture hardens. At the end of the evacuation, the flasks are put on the sludge (about 1 hour), and then the rubber bases are removed from them and the molding mixture is cut at the lower end of the flask.

The next step in preparing the mold is wax smelting. This operation is carried out in a muffle furnace while maintaining a temperature of 120-140 ° C for 1 hour, after which the temperature is increased to 200 ° C and the flasks are kept at this temperature for 1 hour, and then the temperature is gradually increased to 700-750 ° C and the casting mold is calcined for 3 hours. After that, it can be considered that the casting mold 10 is prepared for pouring.

Jewelry Castingit is produced in centrifugal plants or vacuum suction plants. Depending on the type of centrifugal installation (the simplest tabletop centrifuge or centrifugal melting and pouring machine), the method of preparing the alloy for pouring into the casting mold, which must be heated to a certain temperature, is selected.

If there is a centrifugal melting and casting machine, then a heated casting mold is installed with the help of special tongs, and the metal alloy is placed in a special melting glass, and when the melting temperature is reached, the centrifuge is started. Under the action of centrifugal force, the alloy fills the gating mold 11. The rotation cycle of the centrifuge is set. After the end of the cycle, the centrifuge stops and the filled mold is removed using the same special tongs and cooled in vivo.

To pour a casting mold on a tabletop centrifuge, a metal alloy in the form of a hemispherical ingot, previously cast into a special mold, is heated in a muffle furnace to the required temperature (gold alloy up to 700 ° C, silver alloy up to 600 ° C). Then the heated casting mold with the help of special tongs is installed in the plate with the sprue upwards, and the heated alloy is applied to the upper part of the flask. An appropriate counterweight is placed on the other plate. During this time, the temperature of the alloy decreases by an average of 200 ° C. The alloy is brought to its melting point and flow state with an open burner flame, which should be strong and noisy. When the fluid state is reached, the centrifuge is started. The alloy fills the mold under the action of centrifugal force. Then, after stopping the centrifuge, the filled mold is removed from the plate using the same special tongs and cooled in natural conditions or immersed in water. After cooling the mold, the castings are knocked out.

Cleaning of castingsfrom the molding mass occurs in a 20-40% solution of hydrofluoric acid after knocking out the block of castings from the investment ring 12. Then the casting is washed in running water and bleached in a composition corresponding to the metal alloy (for gold alloys - in a 10% aqueous solution of nitric acid , for silver alloys - in a 10% aqueous solution of sulfuric acid). The temperature of the solution should be at least 60-70 ° С. Whitening time lasts no more than 5 minutes.

After bleaching, the castings are dried in a drying oven at a temperature of 100-120 ° C or under natural conditions, and separate products are bitten off from the core. Then the products are sorted out. Defective products and sprues are set aside for recycling in accordance with the technology established at the enterprise.

The main types of casting defects and the reasons for their occurrence

Types of marriage	Reason for marriage
Wax model
Resizing the model	Incorrect calculation of the dimensions of the product standard, incorrectly assembled mold, poor-quality rubber mold
Blockage in the model	Use of contaminated model materials and model returns, contaminated mold, storage of the model in a dusty environment
Deformation of the model	Premature removal of the model from the mold, excessive exposure of the model before assembly, increased room temperature
Local shrinkage	Elevated model composition temperature, mold that has not cooled down
Bubbles and bulging	Excess air in the model composition, excessive pressure during pressing, poor mixing of the model composition, lack of ventilation ducts in the mold
Underpressing	Low temperature of the model composition, insufficient pressure during pressing, dirty mold cavity
Burrs, burrs	Poorly executed mold, improper assembly and dirty connector cavity
Poor surface	Careless cleaning and storage of the model, excess talcum powder
Cracks in the model	Intensive cooling of the mold, excessive exposure of the model before removing from the mold
Casting shape
Rounded shells on the surface of the sprue	Poor mold forming during the evacuation process, high viscosity of the molding suspension
Cracked shape	The time and temperature conditions were not maintained when removing the model composition
Rise of wax models	Careless soldering of models on the riser, high amplitude of table vibration, careless fastening of the riser
Dark color of the sand after annealing	Incomplete burning out of the model composition
Casting
Deviation in the chemical composition of the metal	Incorrect alloy blending, deviations in smelting technology
Blockage	Contaminated metal or crucible, poor mold strength
Slag	Slag getting into a mold with metal
Shrinkage cavities, looseness, porosity	Insufficient power supply of the casting, low-tech casting, pouring with overheated metal, overheating of any casting unit
Gas sinks	Insufficient time for annealing the molds, close installation of molds to each other and the furnace doors, non-compliance with the melting technology, use of a wet charge and wet melting tool, insufficient metal deoxidation, incomplete removal of the mold composition
Hot cracks in castings	The presence of tense places in castings (sharp transitions, sharp corners); metal overheating
Prigard	Elevated metal or mold temperature; incomplete burning of the model composition
Not filling, soldering	Insufficient mold temperature, low metal temperature during pouring, interruption of the metal jet, destruction of the mold, insufficient metal
"Korolki" on the surface of castings	Interruption of the metal stream during pouring, poor-quality casting of the mold
Cold cracks in the details	Low-tech part, sharp cooling of the filled blocks, breakage during knocking out and cleaning
Violation of the geometry of castings	Careless handling of castings, violation of the technology of knocking out castings from the mold
Residues of molding sand on castings	During the final cleaning, the concentration of hydrofluoric acid or the holding time in the solution was not maintained

To reduce or eliminate a marriage, you must first eliminate the cause of its occurrence. With the existing technological process of casting according to the performed models, the rejection should not exceed 10-12%.

High-quality cast products undergo electrochemical polishing in a special bath, the composition of the solution of which should be different for different alloys. The processed products or their elements are subjected to mounting and finishing by jewelers-fitters in accordance with the provided technological processes.

Equipment... To carry out the technological process of casting jewelry using investment models, the following equipment is required: a vulcanizing press, an injection unit, a vibration vacuum unit, a muffle furnace, a casting unit (a melting and casting unit or a simple tabletop centrifuge, a vacuum-metal unit), a drying cabinet, installation for electrochemical polishing, technical scales 1 class, equipment for melting, tanks for knocking out castings and washing out flasks, flasks made of heat-resistant steel, an electric soldering iron, as well as various tools and containers specified in Ch. 3.

Vulcanizing press(Fig. 29) is designed to produce rubber molds according to a sample-standard product by vulcanizing rubber. The presses can be different in design, but they all have heating in the upper and lower plate.

Figure: 29. Vulcanizing press: 1 - stepless power regulator, 2 - temperature sensors, 3 - disc springs, 4 - heating elements

The press is a portable design. A bottom plate is installed on a rigid (cast) bed, into which an electric heater is mounted. The top plate moves along special guides, standing upright and rigidly attached to the bed by means of a worm gear, in which an electric heater is also mounted. The green rubber flask installed between the slabs is heated to a certain temperature. Under the influence of pressure and temperature, the plates of raw rubber are welded together. To regulate and maintain the temperature, the press has an automatic or manual control system.

Injection installations(Fig. 30) are designed to obtain melted models by melting wax and filling it with rubber molds. The installation consists of a wax tank, an electric heater and a temperature control device. Structurally, it can be made in various versions.

Figure: 30. Injection installations: a - type 1: 1 - power regulator handle, 2 - injection nozzle, 3 - reducer, 4 - pressure gauge, 5 - safety valve (or valve for air release), 6 - rocker switch, 7 - nozzle heating control handle, 8 - dial of the air heating temperature control machine; b - type 2: 1 - injection nozzle, 2 - manometer fastening screw, 3 - pressure gauge, 4 - safety valve, 5 - connection for compressed air, 6 - internal reservoir, 7 - external reservoir, 8 - temperature control device, 9 - oil between tanks, 10 - electric heater

The most successful design of the injection unit is a vertically arranged cylindrical casing. A wax reservoir is mounted inside the casing, from which wax under the pressure of compressed air supplied from the compressor through the gearbox enters the injection nozzle. The compressed air pressure is controlled by a pressure gauge, which is installed on the top cover of the casing of the injection system. Excessive pressure in front of the reducer should be no higher than 19.62 * 104 ... 29.43 * 10 4 Pa \u200b\u200b(2-3 kgf / cm 2), and during injection - 1.96 * 10 4 ... 7.85 * 10 4 Pa \u200b\u200b(0.2-0.8 kgf / cm 2). The injector nozzle is equipped with an individual heating system. A chute is installed under the nozzle to direct the flowing wax into a special tray. Control knobs are mounted on the front of the casing of the injection system. The heating rate of the wax is regulated by the power regulator knob (knob with a scale of 0-10). The heating temperature is monitored with a remote contact thermometer. The filling of the rubber mold with wax takes place through an injection nozzle, the temperature of the individual heating of which can be changed from 0 to 50 ° C using a specially provided heating regulator.

For the preparation of wax models, in particular under the condition of vacuum casting, an injection unit of a different design can also be used, in which the model wax is heated indirectly - by means of transformer oil. The installation consists of an inner and an outer tank placed one inside the other. The space between the tanks is filled with oil, which is heated by an electric heater. The wax heating temperature is controlled by a thermoregulatory device, and the control - by a thermometer. The filling of the rubber mold with wax takes place through the injection nozzle under the action of compressed air. The compressed air pressure is controlled by a pressure gauge located on the upper cover of the unit, on which a studer for supplying compressed air (or nitrogen, argon) and a safety valve are also fixed.

Installation for vibration vacuum(fig. 31) is designed to compact the refractory molding compound and remove air bubbles during molding.

Figure: 31. Installation for vibration vacuuming: 1 - stand, 2 - disk table of the chamber with a vibrator, 3 - glass dome, 4 - evacuated flasks, 5 - pressure gauge, 6 - work table, 7 - vacuum pump

The installation consists of a vacuum pump, vibrator and vacuum chamber. The vacuum chamber is a glass dome with a diameter of 300 mm and a height of 350 mm, connected to a vibrator and mounted on a special disk. There is a groove along the entire perimeter of the metal disc, corresponding with small allowances to the diameter of the cap, into which the rubber ring is tightly fitted. On this ring, protruding in height above the plane of the disk, a cap is installed, which, when evacuated, is attracted to the rubber. To remove air from the molding mass, i.e. to evacuate it, the disk has a special hole in the form of a fitting through which air is sucked out.

A flask is installed on the disk and covered with a cap, in which the "herringbones" with wax models are filled with molding mass. When the vacuum pump and vibrator are switched on, the molding mass is evacuated and compacted simultaneously. The number of flasks simultaneously installed in the vacuum chamber is determined depending on the dimensions of the flasks so that during the vibration period there are no impacts on the bell walls and the performance of the vacuum pump and vibrator.

When preparing a set of wax models ("herringbone") for creating a casting mold in a flask with subsequent casting by the method of vacuum suction, it is necessary to increase the volume of the vacuum chamber on a vibro-vacuum installation by using either a according to the diameter of the hood. In addition to increasing the volume of the vacuum chamber in the installation, it is also desirable to replace the electromagnetic vibrator with a mechanical device that provides shaking of the molding mass.

Muffle furnace... Different types of ovens are used depending on the production volume. For small-scale production, the greatest use is the SNOL-2.5-2.5-2.5 / 2M electric laboratory oven and the SNOL-1.6 * 2.5 * 1/9-M2U4 * 2 resistance electric furnace; SNOL-1.6 * 2.5 * 1 / 11- M1U4 * 2. These furnaces provide for automatic regulation of the preset heating mode of the inner furnace shaft. The heater is made of high ohmic resistance wire. Temperature control and regulation is carried out with a millivoltmeter. The heater is switched on with a magnetic starter.

The space between the chamber and the cabinet body is filled with thermal insulation material.

Melting and casting installationdesigned for melting metal and pouring it in a centrifugal way. The installation consists of a melting furnace, resistance, furnace tipping mechanism with counterweight and a centrifugal device that drives the furnace into rotation. A current transformer, a drive unit, and a switchgear are located in the lower part of the unit housing. On the body panel there is a step switch for regulating the furnace current, an ammeter, a signal lamp, as well as two buttons for switching the melting device on and off (on - green, off - red). On the cover of the body there is a mechanism for overturning the melting device at a corresponding frequency of its rotation. It consists of a release device and hydraulic brakes that prevent the crucible from overturning abruptly and the possible leakage of liquid metal.

For small shops and workshops that perform casting in small batches, the most acceptable equipment for casting is the simplest benchtop centrifuge (Fig. 32). At the end of a vertically positioned rack, the axis of which is located in special movable supports, a rocker arm is attached, at the ends of which special suspensions (plates) are suspended. The shoulders of the rocker arm should be equal. The mold is installed on one plate, and the corresponding counterweight is placed on the other. The centrifuge is enclosed by a special cylindrical casing to ensure safety in the event of a drop of the mold or counterweight, as well as spills of metal during the period of starting and rotation. The centrifuge can be started immediately after the metal has been melted and poured into the mold using a stretched cord or electric wire.

Figure: 32. Benchtop centrifuge: 1 - stand, 2 - rocker arm, 3 - suspension, 4 - support, 5 - axis, 6 - cord for starting the centrifuge

Installation "vacuum-metal"for casting by the method of vacuum "suction" (Fig. 33) pumps air out of the mold during the casting of the investment ring. It consists of a working chamber, a pre-vacuum chamber, a backing pump and a control panel on which a pressure gauge, a signal lamp and a pump switch are located. a vacuum seal with a handle is provided in the working chamber with a preliminary vacuum chamber, and in the upper part of the working chamber there is a flange with an annular sealing nozzle.

Figure: 33. Installation "vacuum-metal": 1 - flask, 2 - working chamber, 3 - preliminary vacuum chamber, 4 - vacuum shutter handle, 5 - manometer. 6 - vacuum seal, 7 - foreline pump

The principle of operation of the installation is as follows. A vacuum is created in the pre-vacuum chamber by means of a pump. The calcined flask is installed on the crucible flange, and the casting mold is filled with liquid metal. Next, by turning the handle of the vacuum shutter, the working chamber is connected to the preliminary vacuum chamber. At the same time, the pressure on the walls of the gas-permeable flask decreases (it becomes much lower than the atmospheric pressure), and the atmospheric pressure, acting on the surface of the liquid metal, forces it to fill the casting meanness of the mold.

Installation for electrochemical polishingis designed for polishing cast blanks. The bath for the electrochemical process must be sealed to prevent leakage of electrolytes containing precious metal particles. Titanium sheets of grades VT-1, VT-1-1 with a thickness of 0.8-1.2 mm are used as cathodes. The cathodes are fastened with titanium wire and placed in chlorinated cloth covers. Special suspensions are used as anodes, on which the products are suspended. The pendants are made of the same titanium alloy wire as the cathode. It is recommended to use suspensions that have rigid contact with the product (workpiece). To prevent the dissolution of the sediment formed on the cathode, after the end of the work, the cathodes must be removed from the bath, thoroughly rinsed and dried, and the cathode sediment must be collected for subsequent regeneration of precious metals.

Looking at the windows of expensive jewelry stores, we are delighted with the beauty of the products and the skill of the jewelers. The art of turning precious metal into a luxury item in the imagination of many people is a kind of mystery, a special skill that not everyone can master. How are rings that allure with their beauty are born? What is the path of precious metal from a sketch to its embodiment in an expensive piece of jewelry? What is a flask in jewelry and what is it used for?

Features of the profession of a jeweler

The profession of a jeweler requires more than just creativity. The jeweler must be careful and patient. There are many nuances in this matter, the observance of which requires utmost precision. The jeweler works with high temperatures and hot metal, the danger of this profession requires endurance and physical strength. A jeweler is not only a designer who creates sketches and works with a file under the bright light of a lamp. He is also a foundry worker, handling incandescent furnaces and molten metal, lifting heavy plaster molds and ensuring that technology is followed. The jeweler's arsenal is full of unusual gadgets that a common man in the street has never even heard of. For example, a flask. What is a flask and what is this device used for? Our article will tell about this.

Opoka in jewelry

Despite all the innovations and the high level of jewelry making technology, many of the jeweler's methods of work have remained unchanged since ancient times. The ring casting process, for example, has changed little. To answer the question of what a flask is, you should find out how the process of casting jewelry takes place.

To make a ring of precious metal, a jeweler uses a special refractory cylinder, into which hot metal is poured, molding mass and wax blanks are placed. This is the flask.

This device serves to hold the sand while it is compacted during the production of the mold into which the precious metal is poured. You can make a flask yourself, the main thing is that it is made of refractory material. Some craftsmen make a flask from a pipe trim or roll it from a sheet of iron. The photo shows a modern metal box.

This flask is already filled with a molding compound, inside which there are wax blanks. The next step is calcining the investment ring in a red-hot furnace, this procedure takes place in the foundry.

The use of a flask in a foundry

As sophisticated as the decoration may be in the end, it goes a very harsh path through the red-hot furnaces of the foundry. This is how the casting process looks like:

Products enter the foundry in the form of wax blanks, which undergo a molding process.
The wax blank is placed in a special refractory metal cylinder - a casting flask.
Then the investment ring is placed in a red-hot furnace for calcination. The temperature in such a furnace can reach 1000 degrees. The wax from the investment ring is smelted, and in this form there is a place for the precious metal.
After calcining the investment ring and forming the mold, metal is poured into it. The process of casting jewelry takes place in a vacuum, preventing the formation of voids and the ingress of foreign debris into the mold.
At the final stage, the caster removes the jewelry from the investment box for casting jewelry and proceeds to its final processing and grinding.

Plaster boxes for making jewelry

What is a gypsum flask? In shape, it does not differ from the more common metal. Its only difference is the material and the need for step heating. Gypsum flasks are most often used for small jewelry casting, and not for industrial. In order for the casting process using a gypsum flask to be successful, the temperature regime must be observed, otherwise the mold will crack and become unusable. It is most convenient to do this in a special electric annealing furnace, since the temperature can be controlled there. Annealing of a gypsum flask is performed in several stages:

Heating at a temperature less than 100 ° C. It is necessary to maintain the flask in such a temperature for at least an hour.
Then the mold should be in the oven at a temperature of 250 ° C for two to two and a half hours.
After this time, the temperature should be raised to 450 ° C and the flask should be annealed for another hour and a half.
Only then can the temperature be raised to a maximum of 750 ° C and the mold can be annealed for about three hours.

The annealing time depends on the size of the opokichi: the larger it is, the longer it needs to be annealed.

Disposable flasks

Having learned what a flask is and how it is used, it is easier to delve into the intricacies of the process. It no longer seems so complicated, but rather interesting and simple. Modern technologies allow you to try to make your own jewelry almost at home. The Chinese market offers a wide range of pre-shaped disposable flasks. All that is needed to work with such a form is the required amount of precious metal and the ability to melt it. They are used by both jewelers who do not have their own foundry, and free craftsmen who make jewelry to order.

Casting courses for art products at the Russian Academy of Crafts are interesting not only for jewelers. The studied technologies will complement the professional arsenal of any craftsman working with metal - a manufacturer of souvenirs, jewelry, original accessories for the interior, clothes or haberdashery. Jewelers, on the other hand, will pay special attention to casting with stones, because this technology is rarely taught in courses.

Practical lessons are held in an equipped workshop, students have time to make several educational works. Some of the studied technologies can be used at home, without special equipment, and used at leisure, for example, in the manufacture of knightly equipment or models of equipment. At the end of their studies, students complete their thesis and, based on the results of its defense, receive a qualification document.

What is included in the training program

The program of casting courses for jewelers provides knowledge about the properties of metals and alloys, introduces the tools and technologies used in the casting of art products. Students study centrifugal and vacuum casting, sand casting, graphite, ceramic and metal molds, rubber molds, low temperature home casting. Much attention is paid to safety issues during casting.

In practical classes, students step by step go through the entire process of casting an art product in several modes.

What will you be able to do after the courses

Choose the right casting methods for various materials and for solving specific artistic problems.
Make molds from rubber and silicone.
Create wax (wax models) and collect "wax trees" for and investment casting.
Work with a vacuum injection molding machine.
Making molds for casting low-temperature alloys.
Perform low temperature casting at home.
Cleaning castings and evaluating their quality.

Conditions of education

Training period: 72 academic hours.
In the group until 7 people.
Training materials are included in the course price.
Issued document: Certificate of the profession "Foundry of art products" with the assignment of 2-3 categories.
To register, you must have your passport and a 3x4 photo with you. When registering for a course, you need to pay 50% of the cost of training. The remaining amount - during the first two weeks of study.
Classes are held on the street. Kasatkina (m. VDNKh)

The 3D Avtozavod company offers services in jewelry casting from gold and silver to order. When working with silver, we can use our own certified materials or raw materials of the client. For gold products, only give-and-take raw materials are used. All our products are of impeccable quality, as we are constantly improving technology. The stability of the alloy composition is achieved with the help of the latest equipment and the use of ligatures from well-known world manufacturers.

Features of casting in silver and gold

Gold and silver have excellent technical characteristics. Exclusive jewelry, original souvenirs and interior items can be cast from these precious metals. When casting precious metals, there are norms of production losses:

for purity - 1.8%;
for scrap - 3.5% (if the weight of gold is less than 30 grams, then losses during casting can be up to 5%).

In order to comply with the requirements of the current legislation on the casting of precious metals, it is necessary to register a special account with the State Inspection Institute. You can get all the necessary information about this from the specialists of our company.

3D Avtozavod company fulfills orders as soon as possible, since the entire production cycle takes place at the facilities of our enterprise. Casting from gold and silver is sharpened as much as possible for the needs of jewelers, jewelry workshops and designers. We can offer a whole range of specialized services:

3D design and 3D printing before casting;
removal of molds, electroplating and turnkey processing after casting.

3D Avtozavod accepts orders for casting from gold and silver of any volume. To apply, use the form on the website, write to us by e-mail or call the contact phone number in Moscow.

Jewelry casting (LYUI) is one of the varieties of investment casting (LPVM). However, it has specific features and therefore is a special direction in the casting of art products. The accuracy of the castings is ensured by the use of elastic molds, the use of finely dispersed molding materials based on gypsum and forced metal pouring - on vacuum or centrifugal installations. The LUI technological process consists of the following technological transitions: production of models, assembly of a model set, molding, melting of models, annealing, rate and forced casting of molds, separation of castings from the gating system, heat treatment, control, finishing and assembly of jewelry castings.

Let's consider each technological operation in more detail. First, a master model of the future casting is obtained. If a piece of jewelry needs to be obtained in a single copy, then the artist makes it mechanically, i.e. cuts from thermoplastic materials with a low solidification temperature (68 to 98 ° C). These materials are paraffin wax, shellac wax, ethylene vinyl acetate copolymer, ceresin.

For mass production of jewelry (YI), hot-curing elastic molds are used. They contain raw rubber, which is vulcanized during the mold making process.

Mastsr-modsl is made of metal by machining followed by chrome plating and together with a feeder. The vulcanization operation is carried out on a vulcanization press at a pressure of 5 kN and a temperature of 150-160 ° C for 30-45 minutes. They use crude rubber SKI-3 and SKN-40M. The crumb-like material is placed in a vulcanizing device with a master model inside. From above, the device is covered with a punch and placed in a vulcanizer. The resulting elastic mold is filled with a low-melting mass using an injector. Domestic masses are used, consisting of shellac wax with paraffin (in ratios 20: 80, 40: 60, 60: 40, 80: 20) or a copolymer-ethylene with paraffin in ratios 5: 95, 10: 90, 20: 80, 30 : 70). The optimum ratio is a mixture of 65% paraffin wax, 20% shellac wax and 15% ethylene copolymer. The manufacture of models and model blocks is carried out similarly to LPVM using an injector and a wire soldering iron. The cleaned and finished model is attached to the middle of the riser model by connecting the melted feeder to the gating system using the heated end of a soldering iron. Then, with the same soldering iron, they level out all the nodules and irregularities of the resulting joint.

When casting jewelry, molds are made from uniform refractory mixtures containing electrodynas or cristobalite (the latter in imported mixtures), non-stick additives and gypsum. The shell, as in the LPVM, is absent. Domestic refractory mass "Jewelry - 2" consists of 80-88% dinas powder, 12-20% gypsum and up to 5 ml of orthophosphoric acid, which is added to increase the setting time of the molding mass and its fluidity. The water-mass ratio is 0.32-0.42 / 1, i.e. for 0.32-0.42 liters of water, 1 kg of dry mixture is given. When using imported mixtures, the mixtures of Sati Hiccup, Supercast, K-90 and Inverstright are used. In these mixtures, dinas is replaced by cristobalite and non-stick additives are added. All ingredients are of high purity and constant chemical composition. Imported mixtures consist of 70-75% /? - cristobalite, /? - quartz, 20-25% a-gypsum CaS0 4 and 5% H 2 0. Particle size

The manufacture of a casting mold begins with the preparation of a refractory slurry. For this, powder of a refractory mass (1 kg) is poured into 0.3 - 0.4 l of water and mixed with a mixer. Then the resulting mass is placed in the window of the vibro-vacuum unit and stirring is continued for 3 to 4 minutes. At this time, air bubbles are removed from the mixture. Next, this SMS is poured into a flask with a model block, which is installed in a vibration vacuum installation on a special rubber stand, and vibration vacuumization is continued for 8-9 minutes at a residual pressure in the installation of 1400 Pa.

The curing time of the molding compound depends on the size of the investment ring: in a mold with a diameter of 75 mm to a height of 140 mm, the molding compound hardens within 40 - 60 minutes. In large flasks, the curing time is increased to 3 hours. After 3 - 4 hours the model composition is melted in a steam bath or ovens in air at a temperature of 150 ° C. Upon further calcination, the model alloy remaining in the form burns out. This operation is carried out in calcining furnaces according to the mode indicated in table. 7.

Thus, the total calcining time should be approximately 10.5 hours.

If the mold is poured with copper-based alloys (brass, bronze, nickel silver, cupronickel), then its cooling after calcination and pouring with metal is carried out at a temperature of 600 ° C.

Table 7

Duration of calcination of the model composition

Pouring of YI is carried out forcibly on centrifugal installations or vacuum suction machines. Domestic installations P51, D161 or imported ones are used - Modular 80vac, Plastikat 600/150, S10 / GA1000, etc.

On these machines, filling is carried out at a residual pressure of (0.4-0.6) -10 Pa. Removal of the cast block from the mold is carried out by dissolving the model mass in water, followed by hydrotreating of the YuI block in the P24 hydrotreater. This makes the cleaning process easier.

All other operations in the manufacture of JI, from the separation of castings from the gating system to finishing and control of products, are carried out in accordance with LPVM.