The muffle furnace is a special device for thermal processing of various materials. Her the main feature It is the presence of a special compartment called a muffle that protects the processed item from direct contact with fuel and combustion products. Such furnaces have wide spectrum Applications.

Purpose of muffle furnaces

Ceramics muffle furnaces are used at the final stage of production. They serve to quench the finished products, as well as to subject special paints into the surface of ceramic products. Technology processing is quite simple. The product prepared for processing is placed in a muffle made from special refractory materials. Then the air inside the muffle is heated to necessary temperature And supported at such a level until the firing is completed. Thermal energy Served on the muffle with the heating elements. Muffle furnaces for ceramics often work from the electrical network, since they do not need to heat up to high temperaturesnecessary for metal processing. After the roasting procedure, any ceramic product acquires additional hardness and durability, and the tempered color drawing will hold on to several years, not erasering and not tight.

Laboratory muffle furnaces are used in jewelry, as well as in food, chemical and medical laboratories. Main a distinctive feature this type The furnaces is a high technical equipment, the possibility of operational replacement of the muffle and practically the ideal accuracy of installing operating parameters. Laboratory equipment is mainly intended for experiments to identify ways to improve the quality of a particular product. Therefore, the maximum accuracy of all indicators is a prerequisite. Laboratory furnaces quickly warm up to the desired temperature, equipped with a timer and ensure uniform heating airspace inside the muffle. Muffle cameras are subject to frequent replacement, as it is necessary to work with a variety of raw materials that requires the use of muffles from different materials.

Equipment device and operation

The muffle furnaces for metal processing are often working on fossil combustible raw materials. Their operating temperature is much higher than in electric muffle furnaces. Metal treatment implies their hardening, burning, normalization or melting. The processing process is quite expensive, so it is exposed only to products intended for work in aggressive environments, parts for high-precision engineering, jewelry, spare parts for medical prostheses. Processed metal much better resist negative impact ambienthas improved specifications. And the most important thing is that in the process of processing it is not under the influence of gases allocated during fuel combustion.

The scheme of the muffle furnace looks quite simple. If desired, the simplified version of the device can be collected at home. The most important part of the design is the working chamber - the muffle. For its manufacture, it is necessary to take advantage of refractory clay or other heat-resistant material. First you need to collect the camera of the desired form from cardboard or plywood. Then Outer layer The resulting design is covered with clay, and the wall thickness should be at least one centimeter. After clay hardens, it must be burned at a temperature of 900 degrees Celsius. For this procedure, a standard home furnace dried by coal is suitable.

After completing the procedure and cooling the workpiece, it is necessary to wind the resulting chamber of the faheral or nichrome wirewhich will continue to serve as a heating element. From above, wire must be applied another layer of clay, without forgetting to leave the ends to connect to the electrical circuit. The roasting procedure is repeated again. The body of the future furnace is made of sheet steel with a thickness of 1.5-2 centimeters. In the finished package, a hole is done to output. Then the resulting muffles are placed inside the housing and connect contacts with the heating element. It is very gently and carefully carrying out work on the connection of the electrical circuit, since incorrect connection It may cause short circuit. If there is no experience in such affairs, it is better to seek help from specialists.

The empty space between the walls of the case and the inner chamber must be filled with asbestos crumb. The calculation of the muffle furnace should be done in advance so that in the process of manufacture do not encounter the problem of lack of materials. The device can also be equipped with additional devices, such as a timer or electronic thermometer for convenience during operation. That's all, the resulting device can be subject to test tests and incorporate. For metal operations, it is, of course, is not suitable, but the firing ceramics will pull without problems.

How to choose a suitable oven?

Manufacturers of muffle furnaces permanently improve their products, as high competition in the market stimulates to the permanent satisfaction of client requests. In order not to lose its buyers and conquer new sales markets, it is necessary to keep up with the times. At the same time, the pricing policy should be adequate, otherwise the level of sales will be low regardless of product quality. ECPS muffle furnaces are completed with multi-stage adjustment systems and setup operating modes.

With their manufacture, only modern ecologically clean materials. The furnaces have a two-stage cycle of work, when at the first stage heating occurs, and on the second - stabilization of the resulting temperature. The control unit allows you to memorize the settings when you turn off the electricity. Competitive model - MIMP muffle furnace also has all the most listed advantages. Between these two manufacturers is the main struggle for the domestic market. And no opponent cannot achieve a decisive advantage. According to user reviews, products of both companies are located on summit, so they are leading suppliers in the industry.

Very often, users acquire a thermocouple for a muffle furnace. This device serves to measure the exact temperature. It is mainly necessary when the furnace itself is deprived of the built-in thermometer and does not show the current temperature value. For safe work Personnel is useful for a hood for a muffle furnace. This is a special element of technical furniture, inside which the operating device is placed. It is necessary for a person to accidentally do not dial about a device that heats up while driving.

The inner temperature of the muffle furnace can range from 400 to 2500 degrees Celsius, so even touch external surface May be very unpleasant. From the rest of the additional equipment, the muffles from different materials use in great demand. They are applied depending on working conditions with one or another material.

The price of a muffle furnace depends on its size, operating parameters and functional equipment. Self simple models Can be purchased for 20-25 thousand rubles. A device with high-tech control units, a large working chamber and a variety of work modes, over 1 million rubles will cost. As for the purchase of the device in the secondary market, here you can choose good model With a good functional for 100-120 thousand rubles. But it is worth understanding that buying goods from the hands, no one will give him a guarantee and, in the event of a breakdown, the repair will have to be carried out at its own expense.

The muffle furnace, first of all, is used for thermal processing of various things. It produces melting, hardening and firing of metal, glass, wax and even ceramic materials. Due to the multifunctionality of such an aggregate, a fairly wide temperature Range up to 1000º C.

If necessary, to have such an aggregate in its arsenal it is quite possible to make it yourself, because in stores prices for muffle ovens High enough. Independent assembly such an aggregate is fast enough, especially if you prepare the necessary materials and tools.

Muffle oven - Major varieties

By the type of elements used, to heat their muffle furnaces classified by the following types:

• electricity operating;
• use gas for heating.

Immediately, I would like to note that the muffle furnace, working on gas, does not work with their own hands. First of all, because such home experiments are punishable by law. But the electrical analogue of the furnace is available for homemade production to each wishes. Wherein by its design Such devices are divided into the following types:

• horizontal muffle furnace as in the photo;
• vertical or pot firing device;
• the cap furnace, the example of which is shown in the photo;
• tubular system.

I would like to note that for the construction of your own hands, the design of the muffle furnace is suitable, in which thermal processing of materials occurs in the air. In turn, devices working in vacuum are made only in factory conditions.

Before building such a device, it is necessary to deal with the principle of its work. To begin with, you need to decide on what fuel the muffle furnace will function: coal, electricity, gas or firewood. At the same time, do it yourself easier to do electric deviceconsisting of a chamber for heating and high-quality thermal insulation.

Heat in such a furnace is accumulated due to refractory brick, and thermal treatment of materials occurs in the main chamber - the muffle. For the manufacture of a furnace at home as a muffle, any ready-made refractory form is suitable or made by hand from chamotte brick or heat-resistant clay.

It is very important to understand that the temperature at which the camera of the muffle furnace will start melting, should be higher than that of materials being processed in the unit. In this case, you can making a small oven For smelting and roasting of different materials in small quantities.

Constructive components of a muffle furnace

For the case of such a device, old gas stoveMore precisely, its oven or its electrical analogue. So that the old oven is suitable for further use, all parts made of plastic are removed from it. If a finished design It was not found for the hull house, it was welded from metal sheets of 3 mm thickness.

No less important has heat insulating part The muffle furnace, on the quality of which depends on the efficiency and heat loss of such a device. A red heat-resistant brick is used as an internal thermal insulating layer, which can withstand high temperatures up to several thousand degrees.

For additional thermal insulation of the cutting heat loss along the outer layer, pearlit or basalt cotton wool is paved. Asbestos apply is not recommended to be applied, since carcinogenic substances are released during their heating.

A spirals are used as heating elements inside such a device, for the manufacture of which they take a nichrome or a fekhravel wire with a thickness of 1 mm. In this case, the nichrome material, and, more precisely, the wire from nickel and chromium, is quite plastic and is not subject to corrosion.

Features and varieties of muffles

For the manufacture of the muffle, different materials can be used, and most often apply ceramics or ceramic fiber.

Material and tool for assembly

In order to assemble the oven for firing ceramics with their own hands. the presence of the following materials and equipment:

• electrical rod;
• chamoite red brick;
• electric welding;
• ready-made metal case or sheet steel;
• metal corners;
• thermal insulation do not combustible materials;
• previous heating spiral or nichrome wire.

First you need to decide on the device housing, from the size of which will depend on the size of the main chamber of the furnace. This is relevant for the old oven or bucket. If the case is welded from sheet metalThe sizes are adjusted after the faucet of the muffle.

Also the working chamber for firing is manufactured from chammed clay or ceramic pipe with an average diameter. Therefore, the process of assembling the muffle stove itself has certain nuances.

1. Smooth brick muffle as a photo connects to a circle. For this, the brick is cut with the help of a grinder before the formation of the necessary bevels. After that, the groove is cut in each brick to accommodate the spiral. At the same time, on all bricks, it is cut down horizontally, and on one with a slope, which ensures the displacement of the spiral level below.
2. If the housing is made of an oven, which is placed refractory brickThe laying is performed by a clay-based solution, chamoite powder and sand. At the same time, laying seams should not exceed 5 mm. After the laying is dry, there are grooves for laying spirals. I would like to note that the width of the groove should correspond to the thickness of the spiral, and the distance between adjacent elements is 20 mm.

Production of heating spiral and assembly

Nichrome wire with a thickness of 1 mm is wound on the rod of steel with a smooth base. In this case, the diameter of the helix should not exceed 6 mm. It is also important to monitor so that there is no contact of the adjacent turns during the winding. The finished spiral is placed in the grooves cut into chamotte brick.

I would like to note so that the spiral drops did not occur during heating, produce it with a thin layer of heat-resistant clay or attached in several places with wire. If a ceramic pipe is used as a muffle, then the spiral is wound along the outer side.

To complete the assembly of a muffle furnace for firing with their own hands, remains do a number of uncomplicated workswho are working for everyone.

1. The brick or ceramic working chamber is placed in the steel housing on the bottom, which is laid heat insulating material.
2. On the outside, the bottom of the furnace is strengthened by steel corners. This is due to the fact that the weight of the brick is large enough. Between the walls of the muffle and the main body must remain a gap of up to 40 mm, in which the thermal material is stacked.
3. The cover of the furnace is made of 2 layers of steel and heat insulating material Inside.

For convenience, it is advisable to fix the handle to open the main chamber of the muffle furnace.

How to dry the finished muffle furnace

Dry the finished muffle furnace with your own hands need to gradually In a well ventilated place.

• Drying time design from 5 days to several weeks.
• In the case of intense forced drying, the clay used in the manufacture of a furnace is cracking, and such a device will not be used.
• To test the quality of drying, a muffle furnace is included at a minimum and if there is no evaporation of moisture, the device is completely dried.

It is important to remember that it is necessary to comply with all safety regulations in the manufacture and use of such a high-temperature device.

Mini-muffle

For miniature works as a finished muffle furnace as in the photo use resistor low power up to 150 W. The diameter of resistance with a power of 150 W is approximately 3.8 cm. The size is approximate, since the dimmer of the electrofarforum tube is determined individually by each plant.

The resistance of the wire resistor in 150 W at a voltage of 220 volts is 350 ohms. At the same time, contact clamps made of brass, which require additional heat sink, are considered weak areas of resistance as a muffle, which requires 2 mm thickness copper strips.

After fastening the heat sink, which serves as legs, to the terminals of the wire resistor connect wiresSupplying, nutrition, and heat sinks areolate several layers, non-combustible, insulating material, which is further soaked with heat-resistant varnish.

On the last stage On the muffle put on a shell of the finest sheet steel. At the edges, the shelter bends inside at right angles, so as not to damage the isolation on the legs. At the same time, the complete flap is not needed inside, so in the shell will be able to hold the insulation material. This is a mini-muffle stove ready.

Many builders argue that the muffle furnace is possible to do even on firewood. What if it turns out to find firewood with the ability of the heat sink of 14,000 kcal / kg, then you can still. But not - it doesn't make sense to lach a small muffle, most of the heat goes into the emptiness, namely, an increase in entropy in the universe.

In principle, the concentration of heat released can be obtained for the necessary extracts can be obtained when using a stone or wood coalBut only in the mountain with a supervision system. In this case, there is no meaning of the fence of the whole furnace, only with the need to put the muffle inside the mountain,

Muffle furnace

Buy or do it yourself?

Make a furnace with your own hands with a muffle recommended a volume of up to 5-7 liters. In the event that you take due processing of such a furnace, then work will be turned out clearly not from the lungs. For this reason, it is necessary to see at the beginning which of the finished muffle furnaces will be accurate for home use And what will buy their purchase.

Ceramics for the muffle is required not simple, but with sufficient thermal conductivity. It is given only additives from rare metals. Therefore, to make the muffle on your own better not even try.

How to make a muffle oven forces:

Nowadays, pragmatic craftsmen live, who like to engage in the firing ceramics, homemade or conduct various physical experiments.

• Refractory. At the beginning, we are determined with the material of refractory. The best in cost will be chamotted brick. Can be used asbestos plates and fiber. The second layer of thermal insulation will deliver perlite or basalt fiber.
• Case. It is convenient to use the old refrigerator or stove. If it did not work out anything, you can cook or scream out of steel. The design is sufficiently heavy, the housing from the refrigerator should be strengthened, especially the bottom. For example, spend it welcome steel corner rectangular cross section. The housing is facing basalt cotton wool. This cotton can be used as the upper layer when the roofing is insulation, the material is rigid. It is even called mineral hard wool.

At the Stroynka, we purchase chamotte brick. It is needed for masonry stoves and fireplaces. As a binder material, it is better to purchase a special refractory mixture for masonry.

Fit and subsequent markup:

We decline on the floor side walls of the future chamber so that the rear stack is between the side. The thickness of the seams simulate with wire 3-5 mm in diameter. Customize your brick to each other. Each brick is immersed in the container with warm water For 30 seconds, so that water filled its pores. Lay out the bottom of the stove. After that, lay out the walls.

Seal:

Door closing density can be increased with silicone. After burning silicone, it should be replaced. It is important to lock the door tightly. working chamber. In handicraft and semi-walled conditions, it is possible to create a screw locking device.

We deploy the heating spiral in our future furnace:

The heating element is done by nichrome or from the faherase wire. Its diameter is 1 millimeter, spirals - 6 millimeters. You can take ready-made spirals, and you can also climb yourself.

Disadvantages of homemade muffles:

clay, even if chamotte, carries out heat enough good to uniform warming up of all the muffle. Also, the maximum billet is obtained, the temperature is not less, but much higher than the working.

Where then to take the muffle?

The best option is chemical and ceramic dishes, it can be purchased in stores with laboratory equipment. Form and size - to choose from, everything is usually supplied with lids.

Finally:

Currently, muffle furnaces, especially small-sized almost disseminated and find them permanently in the Master-IP Masters. And in vain, because these furnaces can give a lot.

The muffle furnace is a heating device, inside which is located a special casing - muffle. It separates the internal workspace from the furnace (heaters). In this way, inner camera Protects the working area from carbon monoxide, and heated parts - from interaction with these gases. How is the muffle and is the muffle made?

The muffle protects the heating zone from gases or products of evaporation of heating elements. This creates conditions for thermal processing of parts, to saturate their surface with certain elements (carbon, nitrogen, chromium). The muffle is also used for mirroring of gold, firing products from clay.

In addition to protective properties, the internal chamber provides a uniform temperature distribution throughout work zone. This creates same conditions For thermal processing of parts on the pallet.

From the shortcomings of the coupling it is worth noting low speed Heating to high temperatures, and therefore the complexity of high-speed thermal processing modes in such furnaces. In addition, warming up the muffle itself requires an additional energy consumption, which means muffle furnaces - more costly in operation than the furnaces without the muffle.

Muffle furnaces: scope of application

We list the scope of applying muffle furnaces:

1. Metallurgical production and research in metallurgical laboratories. In muffle furnaces different size Conduct thermal processing of parts from various alloys - hardening and annealing, vacation and formation. Also, the muffles are saturated with carbon, nitrogen, aluminum, silicon, and other elements (cementing, nitrogenation, cyanization, diffuse metallization - chromium, alitation).

2. The combination of gold and non-ferrous alloys, in which it is unacceptable to saturate alloiled impurities. In such a melt, it is necessary to limit the contact of the alloy with combustion products or with the oxidation of heating elements.

Metal blade in a muffle furnace

3. Ceramics firing - used in the production of ceramic products (dishes, sculptural decorations from clay). High temperature firing ensures the strength of the ceramic surface and its water resistance.

4. Drying electrically conductive materials and elements.

Drying materials in a muffle furnace

5. Sterilization of the tool (in medicine).

Sterilization of the instrument in medicine

6. Burning (cremation).

Features of the muffle furnace for melting metals

How the muffle furnaces are arranged: design

Main constructive element Furnaces - muffle. It is loaded in its chamber for heat treatment (or gold for mirroring, medical instrument for temperature processing, firing ceramics). The muffle is made of chemically inert material.

Camera The muffle is located inside the furnace. In this case, the space between the outer casing and the inner chamber is filled with heat insulator. High-quality thermal insulation determines the efficiency of the device, as well as its safety (limits the strong heating of the casing and does not allow the possibility of burning about it).

Heating elements are located outside the muffle or in its walls. They heat the inner chamber, which in turn transmit heat to the workspace. The operation of the heating elements is controlled by the regulator. It controls the temperature and heating time, the whole process of heat treatment. The level of automatic regulation affects the price of the heating device. The more regulating functions, the more expensive oven.

Muffel: Design and Materials

For the manufacture of the inner chamber, the following materials are used:

• ceramics;
• ceramic fiber;
• corundum;
• fireproof (chamoten) brick.

The choice of material for the manufacture of the muffle is determined by the working conditions and the destination of the furnace. For example, refractory fiber muffle is used for heating in a neutral environment. Corundum cameras - can be used in chemical environments. But the ceramic muffle is universal. Thanks to inertia, it is used for various tasks (melting, heat treatment, firing).

In the same case, you can load the muffles from different materials (for different heating and processing purposes). Thus, the inner chamber is a replaceable element that can have a view of a pot or cap, loaded from side or from above. Constructive muffles are divided into the following groups:

1. Caps (they are loaded from above in the form of a cap, after heating are separated from the submission).
2. The pots (also loaded on top, but have a type of capacity, from the submarine is not separated).
3. Simple (the cage is loaded with a side of the furnace).

Heating elements

Heating elements are installed for heating the walls of the inner chamber. It is used as a wire from heat-resistant metal or alloy. When the current passes on the wires, they are heated and highlight heat. To increase the recoil area, the wire is wound in the form of a spiral.

Also distinguish open and closed heaters. Open heaters have a higher heating rate, during breakage - are easily replaced with new ones. But at the same time - faster oxidized (due to heating) and more often fail.

Closed heaters are placed inside the walls of the muffle. They are protected from oxidation, so more durable. Disadvantages: longer heating and a large cost of repair (in case of breakdown, the entire muffle is needed).

Types of muffle furnaces

The muffle furnaces are classified by several signs. By the method of heating, they are divided:

• electrical;

• gas.

By type of protective atmosphere:

1. Air (the muffle limits the mixing of air between the workspace and heaters).
2. Vacuum (inside the muffle creates a sparse space - vacuum).
3. Furnaces with a special atmosphere - the space inside the muffle is filled with special gas (inert, nitriding, restoring, etc.).

The operating temperature inside the furnace may vary from + 400ºC to 2500ºC. On this basis, muffle furnaces are classified for types:

1. For moderate heating - up to 500ºC.
2. For average temperatures - up to 900ºC.
3. For high temperatures - up to 1400ºC.
4. For above high temperatures - up to 2000-2500ºC.

Note: The temperature of heating determines the price of the furnace. The stronger the oven heats, the higher its cost. In addition, prices of the coupling depend on the size and functional equipment (the presence of thermocouples, the type of heaters, automation).

At home, you can collect with your own hands simple design Furnaces. At the same time, the muffle furnace "do it yourself" will work on electricity. Main element - The muffle - can be made of clay or fold out.

For clay muffle make a blank of cardboard or plywood. The resulting box is covered with a layer of clay with a thickness of 1 cm, dried to solidification (3-5 days) and burned in a coal oven. The roasting temperature is 700-800ºC. This is enough to buckle the clay structure and obtaining a strong internal chamber.

Muffl furnace made with your own hands

The resulting ceramic muffle is wedged with wire (nichrome or a faheral, diameter of 1 mm) - it will work as a heating element. In order to secure the wire on the casing, it is covered with a second clay layer (which is also dried and burned in a coal oven). The ends of the wire for further connection to the power grid are retained open.

For folding chamotte muffle in each brick, grooves are done (for location heating spirals). After folding bricks in the grooves there are spiral wire. To secure in the grooves, the helix is \u200b\u200bdeceived by clay or strengthen wire.

The finished inner chamber is placed in a metal case. It is welded from the sheets with a thickness of 2 mm and more. The housing is left for connecting to the heating wire.

The inside of the casing is placed on the finished muffle, connect the contacts and make thermal insulation. As insulating material uses basalt wool or asbestos crumb (asbestos is a harmful option, with heating, carcinogens are highlighted).

Note: Such a muffle oven allows you to burn products from ceramics. For metallurgical annealing or melting of non-ferrous alloys, industrial production is necessary.

Independent manufacture of muffle furnace

Snol furnaces: prices and models

Snol electric furnace manufacturer (SNOL) offers various heating ovens and cameras. Snol muffle variants are laboratory electric furnaces for thermal processing of parts in the air. They are equipped with electrical spiral heaters and a rectangular inner chamber. Scope of applying snoll furnaces: thermal and chemical-thermal processing, heating of samples, calcination.

A model range of snaps provides furnaces with different operating temperatures and a different volume of the working space. Snol operating temperatures are 100-1300ºC. In models under the order, working temperatures may be higher - up to 1600ºC. The volume of working chambers is 3, 6 or 10 liters. Semi-closed and closed heaters are used. In modifications with the volume of the working chamber 3 and 6 l, heaters are located from three sides. In modifications with a camera 10 l - heaters from 4 sides of the inner chamber.

Snol muffle furnace

The muffle material is ceramics or fiber. There are models of snolls in which the internal chamber is made of of stainless steel, brick. The modular design of the furnace allows, if necessary, quickly and easily replace any element.

The quality and reliability of the work of the heating devices SNOL provide Japanese programmable thermostators, fekhral heaters.

Prices for Snol furnace are democratic.

The muffle furnace is the device required for the operation of the metallurgical laboratory. It is also in demand in jewelry and ceramic production, Used in medicine (tool processing). The design is characterized by simplicity. For annealing ceramic products, the muffle can be made with your own hands. For more responsible types of chemical thermal processing, it is better to purchase the furnace of factory manufacture. It will guarantee its quality and safety.

SNOL-7.2 / 1100 Furnace Description SNOL-7.2 / 1100

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Homemade muffle electric furnace (small)

Here I will describe the design of the budget electric muffle furnace of a small size. The power of the furnace is 500 W, theoretical temperature is up to 800 degrees, but I did not warm to there, because for this I have a lot of fisking. A feature of this design is the maximum simplicity and extremely low cost of components. This design can be made from the girlfriend in just a few days, from which the oversees will go to dry the muffle.
The top housing of the oven with an open door. In the center of the corps is the muffle itself. The thermal insulation of the door, as can be seen in the photo, with the help of asbestos cardboard on heels. The window is closed with two layers of mica with some gap between the layers.
Muffle furnace assembly. It consists of two bonded enclosures. In the upper case, the muffle itself is located, and in the lower control unit.

I immediately advise you to make a stove like me in different buildings. This will allow you not to bathe with the cooling of the control unit of various fans. The upper body will heat up and create cravings that, in combination with perforation in the lower case, will be enough to cool the temperature controller.

Production of the muffle.

The muffle can be made by many in different ways. You can take a ready-made ceramic pipe. It is best to MULLIKREMEFIED MKR, you can pipe from the old rheostat, from the fuse of a large fuse. If you prefer a rectangular chamber, then it is better to sculpt yourself. Since my site is sharpened to those practical structures, which I managed to do myself, then here is the recipe for my muffle.

Kaolin (Kaolin clay) - 1 part. You can find near the porcelain factory. Bridge cars for the production of porcelain, faience, electrical ceramics. If not, any clay will go elderly.
Sand-3 parts. Better sand, rather than river.
All this is thoroughly mixed, shut down with water to a state when the lumps do not spread yet, and keeps the shape and leave in a plastic bag for a couple of days. Then we get and mix again to a homogeneous state. Then already sculpt the muffle.
Retreat.
Now there is a lot of things that have not been recently. Now I use such a binding for such work. Meter of Ekaterinburg Ltd. Lacket and its characteristics. It should be borne in mind that this is a ready-made meter, that is, in it there is already a filler in order for drying, it did not lose volume when drying. Therefore, add a large fraction to it, such as sand in a smaller volume.

So, modeling the muffle. The rectangular muffle is lit in a rectangular plywood or craghes drawer. Muffle with smooth pod and arched arch It is painted in the same box. Box size is equal external size The muffles plus 3-6% shrinkage. It is always painted from the inside of the box, since the muftil is compressed when drying outside the crack is inevitable. To make the mixture did not stick to the walls of the box, the walls from the inside are paved with polyethylene. If the mixture is semi-dry, then you can put paper. So you can save the drying time.
After the muftil is flattened, leave to dry for several days. When the muffle walls are closer to the necessary strength, turn over and remove the box from the muffle. Further, if the muffle is not sufficiently durable to the winding of the spiral, it is dried on the battery or in the furnace for several days. Then slowly burn up to 900 degrees. If you have a stress with a firing, in the extreme case, you can leave a dry non-ostenty muffle. But the strength will not be that.
If the muffle is strong enough, then wrapped with a spiral, they are shaking and dried and burned in assembly. As a collection, it is preferable to make it preferable, since the coating will be better to stay on the chief of the muffle. Make sure to closely so that there are no emptiness inside the spiral, everything was filled with coating. Otherwise there will be local overheating of the nichrome.

The calculation of the heater.

About the calculation of the heater on the network a lot of materials. All of them have a different degree of scientific issue. For example, you can not only read various considerations, but also calculate the heater on the built-in calculator. The input data are the power of the furnace, the heater material, the temperature of the heater and the heated product, the design and placement of heaters. At the outlet, we obtain the diameter and the length of the heater wire. But upon closer examination, it turns out that the diameter is chosen for considerations of saving material of the wire and operating conditions are close to ideal. In life, it is usually the opposite. Usually in the bins lies the motok of the old nichrome and his owner is tortured, whether it is possible to use it for the benefit of a person. And with the power of the furnace, too, solid questions.
Therefore, I will give my methodology for calculating, although not such a scientific, but based on its experience making such devices.
So, the first with which you need to decide, this is the power of the furnace. Power directly depends on the magnitude of the muffle and the applied lining. The magnitude (volume) of the muffle is determined by themselves, depending on the magnitude of the heated products.
For modern furnaces With the use of fibrous thermal insulators (ICRV, SPV-350, etc.) approximate power per liter volume will be:
The volume of the chamber furnace (liters) Specific power (W / liter)
1-5 500-300
5-10 300-120
10-50 120-80
50-100 80-60
100-500 60-50
Suppose, for example, you have 3 liter chambers, so the furnace power will be 1200 W. I have a slightly more moufer, therefore the heater power takes 500 W.
Next, calculate the current through the heater :
I \u003d p / u \u003d 500/220 \u003d 2.27 a
And the magnitude of the resistance of the heater
R \u003d u / i \u003d 220 / 2.27 \u003d 97 ohms
Next, we climb into the crust and see the diameter of the existing nichrome. I turned out to be a nichrome with a diameter of 0.65 mm. Next, we pretend to take a table if our nichrome will withstand such a current.

Diameter (mm) 0.17 0.3 0.45 0.55 0.65 0.75 0.85
Admissible current (a) 1 2 3 4 5 6 7

As we see, with a diameter of 0.65, the permissible current is 5 A, so our 2.27 and it will withstand with a large margin. In general, in the manufacture of the heater, it is necessary to take a wire thoroughly, because the thickness of the wire, the more temperature and service life.
Maximum operating temperatures of heating elements. Here:
GS 40 nichrome
GS 23-5 Eurofechral
GS SY Superfechral
GS T Eurofechral

BUT! This is a stick about two ends. We cannot thicken the diameter of the wire strongly, because to get the estimated resistance of 97 ohms, it will have to increase the length of the wire very much, which may not be acceptable from the design considerations.
On the table, we determine the nominal resistance of the 1 row meter of the wire. Here:
GS 40 nichrome
GS 23-5 Eurofechral
GS SY Superfechral
GS T Eurofechral

So, from the table for a diameter of 0.65 mm take (and the subsequent measurement by the instrument confirm), the nominal resistance of 3.2 Ohm / meter. Therefore, the wire length will be:
L \u003d R / 3.2 \u003d 97 / 3.2 \u003d 30 meters
So the payroll for excessive wire diameter is superfluous. But this is not a misfortune, because you will not be able to wind as this wire, and there is a danger to not to keep track and allow the intercity closure on our muffle. This wire must be screwed into the rod. The tip of the wire together with the rod is clamped into the cartridge of the drilling machine, at worst, cartridge hand drill. Wire is served under a small tension.

When Navivka, the following recommendations must be followed. The diameter of the rod for pumping the wire with a diameter of up to 4.5 mm should be no less:
- for nichromes a four-stratic wire diameter;
- For fechors, a five-time wire diameter.
For all alloys with diameter, more than 4.5 mm, not less than six-time wire diameter.
There is another ambush when working with Feheral. Fehehral, \u200b\u200bunlike nichrome, after the calcination becomes fragile, so it's not worth it.
The finished spiral is evenly stretched to length, comfortable for winding the muffle. But no more, because it will be even more difficult to squeeze evenly. Watch the coupling on the grooves and apply the coating, as in Fig.4.
Further, our muftel is placed in a metal case.

The main lining is made by blocks made of chamotte lights bricks shl-0.4. Brick is easily processed by a tool previously described. Pay attention to the hole in the rear unit of the light weight for thermocouples and two holes for the findings of the nichrome.
When installing, the side wall of the muffle was damaged, but it is not scary, it will be restored by the same composition after installation.

I would like to warn you from some ambushes that can climb you in the manufacture of lining.
First of all, I want to warn as a seduction to apply asbestos. Yes, it melts at 1,500 degrees, but at 800 degrees it loses chemically bound water turns into powder. Therefore, such products from it, like a cardboard or cord can work until this temperature. In addition, the fechral should not be contacted with asbestos. I applied it, as this furnace is sharpened to this temperature and I have a nichrome.
Next, about the use as a binder liquid glass. It can be used for laying muffles working up to 1088 degrees, when this temperature exceeds this temperature, the muffle saves. In addition, the fechral also does not like contact with liquid glass.
Regarding the use of fibrous materials on a mineral (basalt) basis, I repeat what I wrote on one of the forums. This is almost the same. Make a blowing out of the melt. Well keep temperatures. But they have a binder that will not endure 250 degrees. But in the Inets, cunning sellers lead the fireproof the fiber itself. Formally they are right. But the fact that after the first fixing binder will unwind and they sneak a handful, they do not write. There are varieties with refractory binding, but there is very little information. Only indirect signs are assumes intended for baths and fireplaces. And again, the fireproof is the fiber itself. And is it worth repeating that the fechral does not like them either. So if you can fly, it is better to use already proven. And from the most MULLIKREMNESS FALLOCI, for example, MKRVH-250 (1300 g).
By the way, the production of ceramic blankets Cerablanket, CeraChem Blanket, Cerachrom Blanket has established in a dry log. I was the first of them dealt, withstands the straight flame burner. The last two are even more refractory. But I did not try them.
On the network, the descriptions of furnaces are walking, which everyone feels each other, in which the muffle appears as the material chammed clay. The usual clay has a large shrinkage and is used as a binder. Shamoth is nothing but a burned clay. Shamot does not matter, it is used as a filler and requires a binder, for example, a conventional non-cylinder clay. Therefore, what is implied under the expression chamotte clay, absolutely not clear.

Control block.

As I promised the description of the NAB most easy furnaceThe temperature regulator will be appropriate. A good inexpensive regulator W-4501, which can be bought at a price of 1 to 2 thousand rubles. The cheapest and angry regulator. Available with measuring and temperature control ranges from 0- 200 to 0-1600 degrees. As a measuring element, thermocouple HC, HA and PP.
Technical Description and Operating Instructions for the Millivoltmeter of Adjusting Type Sh4501 . Read on leisure.
Front control unit panel. This execution of the regulator on the range from0 to 800 degrees, thermocouple ha.
At the bottom right to the left of the control unit, the neon TOO lamp (orange) of the load voltage feed indication, the TLZ (green) lamp of the load turning off and the red thermocouple cliff indication lamp.

Splitting on the back of sh4501. For incomprehensible on the plastic lid, the opening scheme is again shown. Please pay attention to the compensation wire must go to the terminal bar with the compensation coil.
Such fittings for indicator lamps are no longer produced, so I recommend applying a modern type XB2-EV161. They are red, yellow, green, white and blue. Scheme Electrical Control Block. If you do not find a fairly powerful toggle switch in the control unit, then place it after contacts PE23 relay. The relay comes complete with the device sh4501. Power contacts 500 VA relay in AC circuit. The diagram does not shown, 3 groups of contacts in my parallel, so the switched power up to 1500 VA. In the Correct Lamp, the TLZ lamp approaches normal contacts, the TLO is normalized.

Implementation of the installation of the control unit in this box. The regulator is shred in front of skiing. Connected connector (right). The relay is attached on the back cover from the inside.

Furnace assembly. Back view. As you can see, the thermocouple wires and the findings of the heater are cooled simply in air, without excesses. The heater wires are connected through the terminal box, preferably with a ceramic base. I recommend using a ceramic nutrole from a socket or ceramic lamp cartridge.
The conclusions of the thermocouples are also through the terminal bar. The segment of the appropriate graduation of the compensation wire is connected to the same terminal contacts. If it is a regular wire, the device will lie on the temperature difference between this terminal box and the rear panel sh4501 with the measuring coil. Outside on the back cover, an overhead outlet for connecting the load is mounted, and on the back cover of the muffle terminal for connecting the thermocouple. This allows you to use this control unit not only with this muffle, but also for temperature control in other devices. It is enough to fasten the thermocouple of such a graduation to the terminal bar and tap the plug into the socket.

A little about the homemade thermocouple. For the final budget of our furnace, I applied a homemade thermocouple graduation ha. I prefer homemade thermocouples not because of greed, but simply because they have less inertia compared to factory. Although there is a risk of burning the input chains of the regulator. In detail on the manufacture of such a thermocouple, I will not stop, because this process is well lit in the literature (Basins. 300 practical Soviets) And on the Internet.

The material was the veins from the compensation wire of graduation ha. The ends are welded with a tungsten electrode in an atmosphere of argon. If you are so welced to you, whereas it is described in books in graphite with a brown with a powerful transformer. The thermocouple is shred to the ceramic dvuchkanal MKP tube. Here you, sorry, will have to fork.

Heating chamber assembly. The wall is flying, smeared slots. Then the mowl is applied around the mouth of the muffle with some excess. Then covered with polyethylene and the lid closes. The relief of the lid is imprinted on the dressing. Polyethylene is removed and all this farm will dry. The gaps between the lid and the camera are minimal.

Coupl assembly. After laying the spiral, it is cooked with the same composition, which consists of a muffle. Ends of the spirals fix the loop from the glass solutions with a mica. Do not forget to the spiral put a mortgage rod. When the muffle dries, the rod is removed and the hole remains the thermocouple.

The muffle without strapping. Pay attention to the grooves on the corners of the muffle. They so that the spiral does not shift during coating. Downstairs the groove for thermocouples. Thermocouple should be in close proximity to the spiral.