So, itโs worth starting with the fact that assembling a muffle furnace with your own hands is only necessary for those people who are involved in firing, hardening or smelting of any materials. This equipment is not intended for space heating. It is also worth noting that a home-made model will, of course, take a lot of time, several days to dry, but it will be much cheaper than buying a ready-made device, since its price is very high.
Description of the furnace
Smelting in a furnace can not only metal, but also ceramics, glass, wax. A wide variety of work that can be done with this equipment is due to the fact that the range of operating temperatures inside the furnace is from +20 to +1000 degrees Celsius. The process of assembling a muffle furnace with your own hands can be carried out quickly enough, provided that you have all the necessary components at hand. However, it will take several days for the material to dry, as it is often made of fireclay bricks.
Unit Operation
Naturally, for the home-made manufacture of the device, it is necessary to clearly understand the principle of the device, otherwise the work will initially be doomed to failure. Itโs worth starting with the fact that four sources can be used as fuel for the stove: electricity, gas, coal, firewood. Since the muffle furnace will be made with its own hands, it is recommended to take on the implementation of the electrical version of the power source. It consists of two main components: a heating chamber and thermal insulation that retains heat inside. As a heat accumulator, it is necessary to use a brick of refractory type. Heat treatment takes place inside the working chamber - the muffle. Hence the name of the unit. To assemble a muffle furnace with your own hands, it is best to use a porcelain mold, for example, from ceramic plates.
Naturally, it is necessary to take into account the fact that the melting temperature of the selected material for the mold must be higher than the melting temperature of the processed material. Most often, a home-made do-it-yourself muffle furnace made of such materials is used to melt a small amount of metal at a time, and also to harden tools.
Types of Ovens
Before proceeding to the assembly, you need to decide which equipment you need to assemble. When viewed from a structural point of view, that is, tubular or cylindrical, horizontal or vertical views.
They also differ in the type of heat-treating composition. A do-it-yourself muffle furnace for melting metal can be air, vacuum type or use an inert gas. However, it is worth noting that only one option can be implemented at home - air. Therefore, this option will be described. It can also be divided into two classes of furnace according to the features of their thermoelectric heater. It can be of gas or electric type. Of course, using the gas option is more profitable in terms of fuel costs, however, firstly, it is technically very difficult to create it, and secondly, it is prohibited by law to make muffle furnaces for melting with your own hands with a gas heater.
Build start
It will be about creating a unit for firing ceramics at home. For this, a vertical type of furnace will be assembled. As the main tools you will need: a grinder and two circles, electric arc welding and electrodes, metalwork tools, nichrome wire 2 mm thick. As materials you need to have at hand: a used oven case or 2.5 mm thick steel sheet, corners, fittings, basalt wool, refractory mortar and fireclay bricks, silicone sealant.
Production of basic elements
DIY assembly of a metal muffle furnace includes the production of three main elements: a body, a heating element, and a thermal insulation layer.
An ideal option is to use a cabinet from an old electric oven. All means of protection and thermal insulation are already provided here. You only need to remove all unnecessary plastic parts. If this is not possible, then the body is welded from a metal sheet, which before this is cut into blanks of the desired size. After welding, it is necessary to clean the seams with a grinder or a wire brush and cover them with a primer.
Further, for the manufacture of a do-it-yourself muffle furnace for vertical type ceramics, you will need a heating element - this is a key part of the entire furnace. The heating rate and maximum temperature will depend on it. It is worth adding here that for such furnaces, the necessary element is a thermostat, which you can assemble yourself or buy. In this example, a nichrome wire will be used as the heating part. It is important to know that its diameter depends on the maximum heating temperature. The higher the temperature, the thicker the element should be. Today, the minimum and most common is the diameter of 1.5-2 mm.
It can also be noted that nichrome can withstand temperatures of up to 1100 degrees, but it burns out if air enters a heated element. If there is no way to cover the wire, then it is better to use fechral. The maximum temperature for this substance is 1300 degrees, and there will be no problems with air.
Another important part is the thermal insulation, which is responsible for the effectiveness of the design. The installation of this layer is carried out inside the muffle furnace. For this, fire-resistant glue and fireclay bricks are used.
How to make a muffle furnace with your own hands?
The housing is made as follows. A rectangle of the required dimensions is cut out of sheet metal. After that, it bends into a cylinder, and the seam is welded. The next step is to cut a circle from the same metal and weld it to one of the sides of the cylinder. Thus, you get a kind of barrel. The bottom will need to be strengthened with the help of corners and reinforcement. You can use the rectangular shape of the furnace, and not the cylindrical one, this is not important.
Insulation arrangement
Basalt wool is laid out around the perimeter of the rectangle or cylinder. It is necessary to use this material for the following reasons:
- Does not burn. The material can withstand temperatures up to 1114 degrees. When this threshold is reached, the cotton wool will melt; it will not start burning.
- Ecological cleanliness. This resource has no harmful impurities, as it is made of natural materials. Therefore, when heated, there will also be no harmful fumes.
In order to fix the cotton on the furnace body, special buttons are used.
The second step in arranging insulation is laying out fireclay bricks. Only this material can be used, since 75% of the composition is refractory clay. This ensures normal operation, and even at high temperatures the raw materials will not burst.
Finishing work
The working chamber for the furnace is made of brick or ceramic. After that, it is placed in a steel case prepared in advance, which already has thermal insulation. It is very important to note here that there should be a minimum distance of 4 cm between the walls of the chamber and the walls of the housing. Insulation is placed in this gap. The cover for the muffle furnace should be made of two layers of metal, between which there is a layer of thermal insulation. Naturally, you must not forget about the arrangement of the handle for opening the furnace.
After that, several holes must be made in the housing through which the wires of the heating element and the thermal sensor can be brought out. Connection is made to a separate cable, which will be mounted on a 20A machine to increase safety. A ceramic cartridge can be used as a connection between the output and the cable. As legs for the case steel pipes are used. They can be welded or screwed. If a bolted connection is used, the bottom of the chamber must be raised so that the bolts are outside.