According to the design features of the devices are divided into:
Only an air muffle oven can be made at home, so that is what this article will be about.
On the features of the thermoelectric heater:
Of course, the gas furnace will cost 3-4 times cheaper in operation than the electric one, due to the fuel savings, but such an oven, firstly, is forbidden by law to make and use, and secondly, to make a muffle furnace with your own hands on gas technically extremely difficult.
Due to the simple materials, the furnace can be made in any convenient form, including one that will perfectly match the interior of the room.
Picture 2 Schematic diagram of an industrial muffle furnace
Materials and elements for work
Muffle furnace for melting aluminum with their own hands or hardening of steel parts. for the manufacture we prepare a complete set of materials. We will need:
- fireclay bricks;
- heat insulation;
- Sheet metal or any improvised material. If there is an old safe with an inner layer of sand, then you are in luck. Such a furnace will last a long time and will save on the outer layer of insulation;
- Refractory clay, sand or premade brickwork mix. You can buy a fireproofing sealant or use mortar to seal cracks and voids;
- Electrical cable, ceramic insulators, a circuit breaker for connection in the switchboard.
How to make a muffle kiln with your own hands
For almost all of us, the muffle oven is an unnecessary device. And such furnaces are needed only by those professions associated with the melting or firing of ceramics or the production of jewelry. In addition, with the help of muffle furnaces it is possible to create monocrystals, and in medicine. to use them for sterilization at high temperature. The cheapest “store” version of the device costs about 30 thousand, which is certainly not affordable to everyone. But if you remember something from the physics course at school (it’s mostly about thermodynamics), then you can make a muffle furnace with your own hands.
Types of muffle furnaces
Muffle furnaces are classified according to several characteristics. They are divided according to the way they are heated:
Electric muffle furnace
Gas muffle furnace According to the type of protective atmosphere:
- Air (the muffle restricts the mixing of air between the working space and the heaters).
- Vacuum (a vacuum is created inside the muffle).
- Kilns with a special atmosphere. the space inside the muffle is filled with a special gas (inert, nitriding, reducing, etc.).).
The operating temperature inside the furnace can vary from 400ºC to 2500ºC. According to this feature muffle furnaces are classified by types:
- For moderate heat. up to 500ºC.
- For medium temperature up to 900ºC.
- For high temperatures. up to 1400ºC.
- For ultra high temperatures. up to 2000-2500ºC.
Note: Heating temperature determines the price of the furnace. The hotter the furnace, the higher the price. Furthermore, the of muffles depend on the size and functions (availability of thermocouples, heating elements, automation).
How to make a kiln for firing ceramics with your own hands
Special firing furnaces are industrially produced. Among them there are professional equipment, which is quite expensive (from 35 ths. rubles). But you don’t have to buy such devices. They can also be made by our own hands. There are several classifications of firing furnaces. One of the most important criteria is the operating temperature.
The highest category. is the equipment, where the heating is carried out up to 1400-2000 ° C.
The next group. these are furnaces that operate at temperatures of 900-1400 ° C. At moderate rates units of the third category (400-900 ° C) work. And the last group is characterized by low-temperature regime (up to 500 ° C). The most profitable are furnaces with the ability to regulate the temperature.
Depending on the energy source used, such firing devices are divided into electric, gas and solid fuel. Industrial models are of the first and second type only. As for wood-fired equipment, it can only be self-made stoves. The use of solid fuel is not able to provide heating to high temperatures.
Another important indicator of the operation of the furnace is its power. For small units with a chamber volume of up to 50 liters, the following rule should be followed: 100 watts for every liter. If the device has a large chamber volume (100-500 liters), the ratio is different: 50-70 watts per 1 liter.
In terms of configuration, kilns are divided into three types:
The tube furnaces offer the following advantages: The heat is evenly distributed inside the furnace. The other two types are more suitable for large batch production and firing. For inexperienced craftsmen, furnaces equipped with a viewing window that allows you to monitor the firing process will be suitable.
Modern units are equipped with refractory elements made of quality materials, which have a small mass and low thermal conductivity. Heavy designs using chamotte are a thing of the past.
Classification of ceramic ovens
Furnaces for firing clay and ceramics, first of all, are subdivided according to temperature regime. The most powerful of them work in the range from 1400 to 2000 degrees. The second category includes models, the working temperature of which is 900-1400 degrees. Medium temperature equipment provides heat from 400 to 900 degrees. Low-temperature models can be heated no higher than 500 degrees. The most functional, of course, will be the furnace with the ability to regulate the temperature.
Depending on the fuel used, pottery hearths can be wood, gas and electric. Modern industry produces appliances that run on gas and from the mains, variants on wood can be found rarely and only of homemade production. Wood burning temperature does not allow for powerful high-temperature equipment.
The power of the furnace equipment is one of the main selection criteria. For a small fireplace with the volume of up to 50 liters, 100 watts for each liter are needed. If the chamber has a size of 100 to 500 liters, the power of 50-70 watts per liter is enough.
Firing kilns can be in the form of bell furnaces, tube furnaces with vertical loading or horizontally loaded chamber furnaces. Circular furnaces distribute the heat evenly, and bell and chamber furnaces are more convenient for batch firing and work with large products. Beginners should choose models with an inspection window to visually inspect the process.
New generation refractory raw materials with light weight and low thermal conductivity are used as the material for the production of pottery equipment. Heavy and massive equipment of chamotte is practically not produced.
The body is made of steel sheets. Rectangles are cut out to the required size. Then the billet is bent along the radius, and the seams are welded with a welding machine. The resulting construction in the form of a cylinder is coated with refractory paint. When the surface dries, start welding the bottom, a circle for which is cut from the same billet. It is recommended that the bottom and the walls are strapped with reinforcement. The calculation of the volume of the cylinder is made taking into account the thermal insulation layer.
- The inside of the casing is lined with high-temperature material. basalt wool, which is fastened with ceramic buttons.
- The thermal insulation layer is made of fireclay bricks. Place 7 pcs. Insulating layer is made of fireclay bricks, so that a pipe is formed, which will serve as a chamber. Markings are drawn on the bricks for cutting and giving the necessary shape for the joints. To simplify the procedure, it is recommended to number the bricks. When the building material has been given the desired shape, it is assembled into a pipe and tied with a wire. Symmetry must be maintained, otherwise it will be necessary to make adjustments.
- Nichrome wire is twisted into a spiral, 6 mm in diameter. Winding should be done on the base using electrodes and pencils. After the brickwork is removed from the enclosure and laid out in a row.
- The spiral is applied to the brick and the notches are marked. Clear lines are measured with a construction level. The result should be a spiral cable arrangement from the bottom to the top of the pipe. The coils must not cross each other, otherwise it will lead to a short circuit.
- To lay the spiral cables, three strips cut from ceramic tiles are inserted between the bricks. Polypropylene is inserted into the channels. Then the connection to the automatic unit with built-in stabilizer is made.
- The finished structure is placed in a steel case. A brick is placed on the bottom and covered with fireproof adhesive mortar. Drill a hole in the housing in the right place for the coil ends.
- The lid is made of sheet steel, for this purpose, a circle shape is cut out. For better fixation, a single fireclay brick is mounted on the lid. After the handles, the canopy and the iron latch are welded. The parts that will be in contact with the walls of the muffle furnace should be coated with flame retardant silicone. It is not applied in a thin layer on the surface, previously treated with degreasing agents.
- The first start-up. The construction must necessarily dry in a ventilated room. When drying, it is forbidden to use any heating appliances, because this method leads to cracks in the masonry joints. Only when the coils are completely dry can they be connected to a stabilizer. Next, the power and temperature are set for operation.
Recommended: How to make masonry various brickwork stoves
Muffle kiln with your own hands
Muffle furnaces are a design whose heating elements allow to achieve the temperature required for firing ceramics, melting of metals, hardening of steel in a personal workshop. Jewelers and other craftsmen whose workshop is at home, understand the value of such a design. And given the high cost of factory-made muffle furnaces, such a furnace, made by yourself, becomes particularly important.
Design of an electric muffle furnace
Independently make a muffle furnace with their own hands, if you have the appropriate materials is not too difficult. It requires skill in working with metal, bricks and electrical circuits. From the tools you need the following minimum set:
- A drill with a set of metal drills.
- Angle grinder with multiple abrasive and grinding discs.
- Inverter welder and some electrodes for it.
- Hand saws on metal with spare blades.
- Pliers and wire cutters.
Some materials are also needed. Their exact number depends on the project on which the oven will be built, and is calculated in each case separately. Must purchase:
- Metal angle bar 5×5 cm and 2-3 mm thick
- Sheet steel 2-3 mm thick
- Hardware for fasteners and making of locking elements (bolts and sockets)
- Fireclay bricks
- Basalt or perlite wool in the form of prefabricated mats
- Silicone sealant for stove works
- Torch tubes with a 4-5 mm inside diameter
- Electric wire in heat-resistant insulation
- Electronic parts for the temperature control unit (thyristors with heat sinks, high-capacity resistors for the ballast, ready-made electronic thermocouple thermometer, tumblers and automatic 15-20 amp fuses)
- Nichrome or Fechral wire with diameter of 2-3 mm and a length of 10-15 meters (in the coil)
All of these are useful for building both electric and gas muffle furnaces. In the latter case, electronic components are not needed. You will only need a solid state thermometer. The specific diagram or drawing can be found on the Internet or you can use one of the following. The size of the muffle furnace can be changed if necessary. The main thing is to correctly recalculate the size of the heating spiral.
Пресс для керамики. или ZEROS?
Advice! It is recommended to use a gas furnace body from a discarded gas furnace or a washing machine as the base for a muffle kiln. This should not be done, as the apparent simplicity of the equipment will turn out to be short-lived construction and its poor performance. It is more reasonable to initially make a solid structure of metal angle and sheet metal.
The gas muffle furnace is made from a burner and a ceramic muffle (made from a ceramic vessel similar in properties). Burner flame heats the outer surface of the ceramic and does not contact with the contents of the muffle. Such a device always has a small working volume and is used in the manufacture and processing of small metal or ceramic items (for example, hardening or tempering knife blades, firing of miniature sculptures). Large muffle ovens are difficult to make in the home workshop and would be unsafe to use.
If you need a furnace with a working volume of 10 liters and more, the right choice is a muffle electric furnace. it is more practical and much safer. The essence of its independent manufacture boils down to welding the basic framework of metal angle and sheet metal. Two layers of thermal insulation. basalt wool (outer layer) and fireclay brick (inner layer). are installed on the inside of the oven. In the brick are made saw, angle grinder and chisel grooves or grooves for heating spirals. Most often two independent circuits are made (can work simultaneously).
Important. The gaps between the bricks are smeared with a special heat-resistant clay for masonry ovens (it can withstand up to 1700 degrees). This is a safe and reliable tool, the main thing. carefully grout joints and do not make them thicker than 3 mm.
The door is sealed with several layers of silicone sealant. It will wear out over time, but it’s easy to upgrade. In the final assembly, the furnace is connected to a thermostat block. it will allow you to control the internal temperature and change it smoothly. Often electronic programmable units are additionally installed. they not only perform the measuring functions, but also allow carrying out heat treatment according to a complex program without any human control.
Tip! When making the body of the muffle furnace do not forget to make a few technical holes in its lid for the evaporation of moisture.