Knife for polystyrene. Cutting foam at home - a knife or a homemade machine? We use automated systems

The issue of home insulation is very relevant today. Sheathing the facades of houses with foam plastic is one of the most popular types of insulation. And this is very reasonable, because. the process of such insulation is simple and understandable, and all the necessary materials are always on sale.

But everyone knows that gluing foam is very convenient on a flat wall. With any method of gluing the foam to the wall: dry mix glue, foam or glue-foam, it is always very important that the foam sheet fits snugly against the wall and does not create air gaps.

If the wall is even, then no questions arise. But, unfortunately, the walls of old houses do not differ in ideal evenness. Yes, and different design features of the structure sometimes create drops on the plane of the wall.

Partially, this drawback can be leveled by laying the foam on a thicker layer of glue. But the maximum allowable thickness of the adhesive layer often cannot cover the magnitude of the differences in the plane of the walls. In addition, too large differences lead to unjustified overspending of glue.

The next way out of the situation remains - cutting the foam in thickness. But doing this with a hacksaw is very inconvenient and time consuming, especially if you need to cut a large amount of foam. In addition, during cutting, a large amount of debris in the form of foam balls is formed. Yes, and the surface is uneven and the accuracy of such cutting is very conditional.

In order to quickly and evenly cut the foam of the desired thickness, you can use a foam cutting machine. This device can be made independently, absolutely with your own hands.

The principle of operation and the device of the machine for cutting foam

The principle of operation of the machine is based on the fact that the foam is easily melted under the influence of temperature. Thus, if you draw a thin heated wire over it, it is easily cut, while forming a perfectly flat, smooth surface.

For the manufacture of the machine, the following components are needed:

• LATR (laboratory autotransformer) or car battery;
• nichrome thread;
• racks for attaching nichrome thread;
• spring (1-2 pcs.);
• tabletop board;
• copper wire.

A nichrome thread (spiral) is used as a cutting object. You can either buy it in a store or extract it from old household appliances in which they were used as filaments (a hair dryer, for example). The thickness of the spiral can be 0.5-1 mm. The most optimal thickness is 0.7 mm. The length depends on the width of the foam to be cut.

An important element of the device for cutting foam is LATR. But if it is not there, then it can be done using an old transformer and a device for charging car batteries.

You can also use a computer power supply that uses wires that give 12 watts (yellow and black) to connect to the spiral.

To operate such a machine, it is enough to have an output voltage of 6-12 watts.

It is necessary to correctly adjust the length and thickness of the filament and to match the voltage. If the thread is too hot, it may break. Well, if the thread is slightly heated, then cutting will be slow.

A car battery can also be used as a power source. They can be used in conditions where there is no electricity on the site.

For different tasks, you can make different designs of the foam cutting device.

Basically, these devices will differ in the length of the spiral. To cut foam into bars, a short spiral length is needed.

You can install two spirals and cut the sheet into several bars in one pass.

Two spirals cut the sheet into three parts in one pass. The stand is stuffed with guides for smooth feeding of the foam.

But, in extreme cases, foam plastic can be cut into bars with a hacksaw. It is much more difficult to cut the foam in thickness, and even with a given size. Therefore, we will consider how to make a machine for cutting foam in width.

Step-by-step instructions for self-manufacturing the machine and cutting foam

Step 1. Preparation of the countertop. As a tabletop for a do-it-yourself foam cutting machine, you can take any piece of chipboard of the right size. The surface on which the foam will move must be smooth. Holes for racks are drilled in the table top. It is convenient to use metal pins with a thread with a diameter of 10-12 mm as racks. The height of the racks should correspond to the thickness of the foam sheets plus a margin in height. The pin is fixed with nuts.

To give the structure stability, bars are attached to the tabletop from below, which will also serve for the safe passage of an electric wire.

Step 2. Connecting the current supply wires. From below, under the tabletop, the wires are connected to metal rod-racks: the wire is wound around the lower end of the pin and pressed with a bolt.

The other end of the wires must be connected to a power source, depending on the method chosen. The best connection will be through a plug, which will be connected to the LATER socket. It is possible to connect via self-clamping terminals, as well as by twisting and soldering. It depends on the selected power supply.

In any case, the connection must be made in accordance with the rules for working with electrical installations and devices, be convenient for work and safe during operation.

Step 3. Fixing the Nichrome Spiral. Nichrome spiral is fixed between two racks. A spring is attached to one end of the spiral (there may be two of them).

The spring is needed in order to pull the nichrome thread during operation. The fact is that when heated, the nichrome thread lengthens and sags. The thread in this state will not give a quality cut. Therefore, the thread is fixed in an initially stressed state, so that the spring is slightly stretched.

To fasten the nichrome thread to the pin, washers with an inner diameter slightly larger than the diameter of the pin are used. A small hole is made in the washer for attaching the spiral itself. A small sharpening is also made on the side of the inner diameter so that the washer can be fixed on the thread of the pin.

A spring with a spiral attached to it is inserted into one washer and put on the first pin. The second washer is put on the second pin and a nichrome spiral is threaded into the drilled hole. Next, it is pulled so that the spring is stretched, and fixed.

Step 4: Cutting the Styrofoam To dissolve a sheet of foam into two sheets of a given size, the spiral is set to the desired height. The required distance is measured with a ruler.

The machine is then connected to a power source. The thread heats up and now you can cut the foam, smoothly moving it forward along the countertop.

The cutting speed depends on the temperature of the filament, which in turn depends on the voltage applied and the thickness of the filament itself. Do not try to apply more voltage to achieve high speed, because. this can cause the filament to burn out quickly. Here, a balance between tension, thickness and length of the thread must be selected empirically. The thread should not overheat during operation. When heated, it becomes red or scarlet. But it should not turn white - this indicates that the thread is overheating and that it is desirable to reduce the voltage, otherwise the thread will not last long in this mode. Of course, smooth adjustment is easily done if LATER is available. But if it is not there, then a laboratory power supply can also be made from a computer power supply, the video below has more information. After you have made this foam cutting machine with your own hands, you need to make sure that the machine is safe.

It must be remembered that all activities must comply with safety regulations for working with electrical appliances. The power supply must be grounded, all connections must be carefully insulated. All work on the assembly of the machine must be carried out with de-energized wires. The machine is connected to the mains only while working with foam. After work, it must be immediately turned off. While working with the machine, touching the metal parts and the nichrome thread itself should be avoided.

Step 4: Cut the Styrofoam at an Angle Sometimes it becomes necessary to cut the foam in such a way that one side is higher and the other lower.

To do this, the spiral is set at a slope with the desired parameters. In this way, foam sheets of various sections can be obtained.

Useful video

Styrofoam rightfully occupies a worthy place in construction and finishing works. Its heat-insulating and noise-absorbing characteristics allow it to be used in the decoration of facades, country houses, and industrial enterprises. The construction of the material consists of foam particles that fill the gas cavity during molding. The cost of the material is not high, it can be used in any field of activity, large letters on advertising, information boards, etc.

Basic Methods for Cutting Styrofoam

The best option for thermal insulation of the building is foam. Usually, a non-dense structure is chosen for these purposes, due to the low cost. This causes inconvenience when cutting, the structure of the cells crumbles, and with a little effort, you can break the structure with your hands. The foam cutting tool has various modifications, ready-made options are sold, you can also make a design with your own hands.

It is important to understand that the structure of the foam is categorically related to the impact of certain liquids. Acetone or gasoline destroys the structure of the foam, the product will have to be made again. Temperature operation modes are no more than 50 °.

Cutting foam at home is performed by many improvised tools. For example, when working with small workpieces, the easiest way is to use a clerical knife. The process is inaccurate, because the blade dulls quickly, for better processing the knife can be heated.

Each of the devices has advantages and disadvantages; before cutting with your own hands, it is important to note the characteristics of the foam, to choose a tool for cutting the foam to size.

1. In hardware stores you can buy a special tool - a knife with a heated blade. Work with this device is carried out on its own, in order to avoid slipping and injury. The main disadvantages of a cutting knife are that they can cut material of a certain thickness; for smooth work, you need to correctly mark the product and spend time on it.
2. A type of heated knife can be a soldering iron with a special nozzle. It has a higher heating temperature, you need to be careful when working, a molten drop does not deliver joyful sensations when it hits the skin.
3. A shoe knife for cutting foam is used with a long blade up to 40 cm. The tip of the knife remains blunt, and the wide blade must be perfectly sharpened. Adjustment and sharpening is carried out every 2 meters of the cut product. The process will be accompanied by a squeal, you can eliminate unpleasant sounds by using headphones.
4. Thicker pieces can be cut with a fine-toothed wood saw. The lower the level of the teeth, the better the quality of the output part, however, scuffs and bevels will still be present. The method does not require the application of special products, it is often used for long straight cuts of foam.
5. The most popular way is to cut the foam with a string. The performance of this method is equivalent to industrial equipment, it is enough to build a small structure. The string is used when working with foam plastic of various grain sizes and densities.

Some cases, in the absence of any of the above cutting tools, require the intervention of electrical engineering. The grinder is used with a disc of minimum thickness. The work implies the presence of increased noise, debris from foam particles throughout the territory.

The processes of work on the insulation of one dwelling can be performed with a manual type tool. The wire for influencing the foam is used on a special stand, previously prepared. The design consists of nichrome wire, easily made by hand. The connection diagram consists of two fasteners, a load for tension and power to the network. In cases where production volumes are increased, special foam processing machines are used.

You can buy them in specialized stores, as well as make your own.

Machine classification

The design features of the units do not differ from each other. In each of them, cutting occurs due to a heated wire fixed in a certain position. Some of the modifications have up to six adjustable strings, this allows for more massive work. Machines for cutting foam plastic can be with a turntable, a permanently fixed cutting element.

Devices are divided into several categories:

• software-controlled equipment that allows you to cut figures of increased complexity;
• portable cutting elements;
• transverse or horizontal types of cutting.

The most complex machines in design allow you to work on several planes of the product at once. The performance of foam cutting machines is designed for industrial purposes; in one go, some models can process over 10 meters.

Do-it-yourself foam cutting tools

Home insulation materials are always available for sale. It is best to glue the foam on a flat wall, but if protrusions are found, you will have to adjust the shape of the foam. Styrofoam cutting is carried out both by purchased equipment and by self-made.

To build a structure, it is important to select the parameters and drawings. The type of work also depends on the design and its dimensions. Cutting foam at home is carried out from improvised means, the main thing is to choose the right materials. It is important to comply with safety requirements, when cutting, slippage of the product, damage to the limbs is possible.

In the process of heating the foam, fumes are released, if inhaled, they can damage the mucous system of the worker.

Homemade thermal cutting knife

It is possible to correct the shape of insulation products, cut out small products and blanks with a thermal knife. To cut foam you will need:

• A krone-type battery with an output voltage of 9 volts, or a set of finger products.
• The nichrome fishing line is stretched between the plates, the length is not more than 10 cm.
• Several wires connect the ends of the wires to the battery.

The simplest cutter can be assembled from improvised means, it will help to chamfer corners, perform the necessary fitting of polypropylene parts. It is necessary to install a power button that will activate the device, this is done for convenient, safe operation.

DIY nichrome cutter

Do-it-yourself production implies the presence of certain means. In order to qualitatively assemble a tool for cutting foam, you will need:

• nichrome wire, it can be purchased at radio parts stores of the required size;
• a 12 volt step-down transformer, it is a computer power supply or a car battery charger;
• long needle;
• rheostat, which makes it possible to regulate the strength of the current;
• electrical wires suitable for connection are long.

The device can be mobile or fixed on a table. The frame is made of wood, the wire is set to a height of 10-15 cm, on the adjusting screws. The screws that secure the nichrome wire must be of the right length to adjust the height to the desired level. A weight is suspended from one side of the screw to tension the wire for a straight cut level.

The impact of current leads to splitting of the wire, the foam is easily exposed to temperature effects. The edges are sealed, this prevents the decay of the structure of the material. The cutting of the foam begins after the appearance of a red tint on the wire, it is not necessary to bring the incandescence to a high level, in these cases the width of the cut will be too large.

When performing the procedure, you should use personal protective equipment, a mask, gloves. The melting process releases toxic fumes.

Cutting is done indoors with good ventilation or outdoors.

Design features and principle of operation

The string expands when heated, adds up to 3% in length, cutting with a sagging cutter will not be of high quality, so a special mechanism is added to the design. With actions with a low frequency, it is possible to use a spring, it will gradually stretch the wire to the desired state. Mass use means fast stretching, so it's best to use a suspended weight to one side of the string.

The foam cutter is powered by power sources with an output voltage of 12 to 36 volts. The most successful option is a laboratory transformer. The device is able to withstand high loads, to smoothly adjust the output voltage.

Specialized machines and their prices

The manufactured machines are delivered for mass production. There are modifications with six cutting elements, which allows you to quickly cut a large amount of foam in one run. Laser machines perform work for architectural purposes, are able to cut various shapes, materials in thickness.

Machines have excellent characteristics, can have the functions of simultaneous processing of many elements, and have high productivity. The price of devices is high, you need to know exactly what the cutter is used for.

Frp 01

A simple design allows you to modify the device for various shapes and sizes of foam blanks. Various types of foam cutting tools allow you to carry out a number of actions. Implemented the ability to trim linear parts, curly elements, insulation boards and signboards.

The cutting is done by the machine by connecting to the CNC. The cutting program is supplied with various settings. The price of such a device starts from 110 thousand rubles, it is important to check the functionality and reliability of the design before buying.

SRP "Kontur"

There are modifications of machines for the production of elements of various shapes. The styrofoam cutting machine is manually operated, has a simple structure, rich functionality. The power consumption is not high, the components are collapsible, which allows you not to worry about transportation.

The cost of equipment starts from 40 thousand rubles. The main difference between market models and hand-made ones is the tests carried out for the safety and reliability of parts.

Self-made cutting machine

A complete machine can be made at home. For the manufacture of the machine, a tabletop and a frame of the desired width, as well as other details, are selected. A do-it-yourself foam cutting machine is made from improvised means, by analogy with the smallest nichrome modification. There are several modifications and structures of machines, implemented in accordance with the conditions of the details.

Manual cutting of styrofoam

Of all the above methods, manual cutting of foam is not so expensive, an abundance of methods allows you to influence foam products in accordance with the tasks.

1. The simplest and least expensive way is cutting with large sharpened knives. The tip of the knife is left blunt, oil must be distributed across the width of the knife for lubrication, the speed of this method is not high, cutting of small volumes is used.
2. A hot rune allows you to quickly perform work, but is harmful to health.
3. Cold wire cutting is similar to the action of a saw, it is only necessary to make a productive structure.
4. Cutting with a hacksaw blade.

Professional methods involve the use of a ready-made tool. High-quality and fast cutting is carried out by using suitable devices.

Homemade machine on the table

If there is a large table and workplace, this will significantly save time and effort, because when using manual methods, the material crumbles and deteriorates. A home-made machine and its foam cutting design is performed by using a nichrome string.

A suitable power source is used, which produces from 12 to 36 volts. It is possible to use the voltage of a regular network, but only there is a wire coated with nickel, this method causes an electric shock, which is significantly felt by a person.

The machine for figured cutting of polyfoam

Complex geometric shapes can be processed with a special machine. The device allows you to make figured cutting of foam plastic with your own hands. The design is carried out according to the same principles, only the nichrome wire is stretched vertically.

The fastening mechanism fits on one side, which makes it possible to move the product on the tabletop.

Polyfoam is a good heat insulator, characterized by durability and low weight. It is used to create a variety of shapes, blanks and models, as an excellent insulation. It is quite easy to work with him. But often such material is produced in the form of blocks with large geometric parameters. Cutting them with a saw or knife is very inconvenient. Products crumble, which violates their structure.

The problem with cutting heat-insulating material is solved by a foam cutter, often called a cutter. You can buy it at a hardware store or make it yourself. In the second case, the home master gets at his disposal a tool that suits him in all respects.

Elementary carver - half an hour and ready!

The simplest tool for cutting foam sheets (expanded polystyrene) is made without the slightest difficulty with the help of 4-5 batteries for a flashlight and an ordinary guitar string. The process of creating a cutter will be as follows:

• batteries are sequentially connected to each other in one block;
• a guitar string is fixed to the ends of the resulting module.

As a result of these actions, a tool with an electric closed arc is obtained. The current passing through it will heat up the string. At the site of its contact with the material being cut, the process of melting and cutting the expanded polystyrene sheet into two parts will be observed.

For the operation of the described home-made thermal knife, the string must be heated to 130-150 ° C. With the help of such a simple tool, you can cut 1-3 blocks of foam. It is not advisable to use it for cutting a large number of sheets due to the fact that the batteries will sit down very quickly.

Varieties of electric thermal knives and their features

If the master uses foam regularly and performs large amounts of work, it is advisable for him to make a tool with his own hands that functions from a household electrical network. Such homemade thermal knives that do not require separate chargers are used for:

• linear cutting;
• curly cut.

They use a nichrome thread or a metal plate as a working thermoelement. A mandatory block of such devices is a voltage-lowering transformer (Figure 1). Its windings must meet the following requirements:

• cable section - from 1.5 mm;
• voltage - from 100 V (primary winding), 15 V (secondary).

Experts recommend connecting a step-down device to an autotransformer (LATR), which allows you to smoothly adjust the output voltage. If there is no desire to purchase such an expensive device, you can do otherwise:

• put the switch on the taps of the secondary winding;
• equip the step-down transformer with a rheostat.

Linear cutting device - how to do it?

A homemade thermal knife for cutting flat sheets of expanded polystyrene foam is a simple design. Any craftsman will understand the principle of its creation.

The basis of the structure is a frame made of steel profile or wooden bars. In its lower part, a working surface is mounted from particle boards, plywood of great thickness. Some masters use textolite sheets for its construction.

The function of the work surface can also be performed by an ordinary table or workbench. Then the need for a frame is eliminated. And the construction process itself is as follows:

• On the table (another flat surface), two vertical supports are mounted, which are fixed with insulators.
• A transformer is connected to the latter through electrical contacts to lower the voltage.
• A nichrome wire is stretched between the insulators. A special weight is suspended from it. It is needed to tension the thread.

Such a foam cutter functions simply. Electric current passes through the thread, heats it up, which leads to stretching of the wire. The load does not allow the latter to sag.

A heated nichrome thread easily cuts a foam block horizontally, which is moved by hand. As a result, flat sheets of insulating material are obtained. Their thickness is determined by the distance separating the stretched wire from the working surface of the table.

When performing the described operation, it is important to ensure that the expanded polystyrene is supplied at the most uniform speed.

In cases where the material must be cut vertically, the design of the cutter is slightly modified. The frame needs to be additionally equipped with a paw-holder. Hang a nichrome thread and a weight from it, passing the latter through a hole previously drilled in the table. It is desirable to install a hollow metal pipe in it, which will protect the master from burns when the wire is heated.

Rules for the manufacture of tools for figured cutting

If cutting at home will be subjected to foam sheets of large thickness or geometric dimensions that do not fit on the work surface due to their parameters, it is recommended to make a thermal knife from a hacksaw or a manual jigsaw. The work is done like this:

• The cutting blade of the jigsaw (hacksaw) is removed.
• An electrical cable is connected to the tool handle.
• Nichrome wire is bent at a given angle.
• The figuratively bent thread is installed in the place where the canvas was previously placed, and fixed with nuts and screws.

All metal elements on a self-made structure are insulated. If desired, you can immediately bend several nichrome canvases at different angles. Then curly cutting will be more comfortable.

During construction and finishing work, the question arises of how to cut the foam so that it does not crumble. To do this, use special tools and techniques that are selected based on the size of the foam plate. These cutters can be purchased at the store or you can make your own. To make a tool with your own hands, you do not need special knowledge or skills.

DIY nichrome cutter

Styrofoam is cut with a string heated to +120 ... + 150 ° С and melting the material. Thanks to this, the cut is even, and the foam does not crumble. On such devices, a nichrome thread is installed through which electricity is passed. You can make a simple cutter with your own hands. It differs from the machine in portability and compactness, so the heating temperature of the nichrome wire cannot be adjusted on it.

Necessary tools and materials

To make a cutter with nichrome wire for cutting foam, you will need the following tools and materials:

• a small wooden block;
• screwdriver and drill;
• 2 pencils;
• 2 pieces of copper wire;
• round nose pliers;
• hot glue or PVA;
• insulating tape;
• battery connector;
• switch;
• 1 m wires;
• soldering iron;
• nichrome thread.

The latter is sold in a radio parts store. It can also be taken from old heating elements from a hair dryer, boiler, boiler, etc.

Homemade foam cutter

A homemade cutter is designed for minor work. It is not possible to cut the entire sheet of polystyrene foam with them. To carry out cutting foam at home, you must:

1. Make 2 holes in a wooden block 10-11 cm long. They should match the diameter of the pencils. You need to retreat 1-1.5 cm from the edge. The recess should be slightly deeper than half of the bar in order to fix the pencils. Due to this distance, it is possible to cut a sheet of foam plastic of almost any thickness.
2. Glue both pencils into the holes with hot glue or PVA.
3. In each of the pencils, make a small hole for the copper wire on top.
4. Bend the copper wire with round-nosed pliers so that small rings are formed at its ends. After that, install in the holes in the pencils.
5. Glue the battery connector perpendicular to the wooden block. Additionally, it will play the role of a handle.
6. Stick a switch on the bar so that you can de-energize the string.
7. Then connect 2 wires to the connector. After that, connect to the switch, and then bring each one to a separate pencil. So that the wire does not sag and does not interfere with work, it is fixed with electrical tape. To ensure a reliable connection quality, you need to solder the wires to the connector. The joints must be insulated with heat shrink tubing or electrical tape.
8. Clean the other end of each wire from the braid and screw it to the copper wire. Solder the connection.
9. Thread the nichrome thread into the rings of copper wire and fasten to them. The string should be taut between the pencils. When heated, it stretches and sags a little. The stronger the tension, the less sag.
10. Insert the batteries into the connector and start cutting the foam sheets.

Thus, you can make a simple do-it-yourself foam cutting device. And another version of the manufacture of the machine, see the video:

DIY foam cutting machine

Cutting machines are more convenient because the cutting thread is fixed in them and only the foam needs to be moved. This allows you to increase the accuracy of movements. In the manufacture, you will need the same tools and equipment as in the previous case.

First you need to make a table, which is a wooden base with small legs. The table must be flat and smooth to prevent deformation of the foam. The dimensions of the base are chosen arbitrarily. A bar is screwed perpendicular to the tabletop, and a wooden crossbar is attached to it at an angle of 90 °. Then it is necessary to strengthen the structure with a jumper.

An angular ruler marks the place where the filament will go. If the surface is fairly flat, this can be done with a plumb bob. To do this, a self-tapping screw with a wide head is screwed into the end, and a thread with a load is wound onto it. A hole with a diameter of 6 mm is drilled in the selected place. To prevent the string from burning the wood, a plate of textolite or metal is installed. The material should be placed flush with the surface.

A wire is threaded into the hole, the lower end of which is put on a self-tapping screw. The screw is screwed in next to the hole. The length of the spiral should be such that when heated, the latter becomes red. Since the wire lengthens at high temperatures, a compensating spring must be used to avoid sagging. A spring is mounted on the upper self-tapping screw, and a nichrome thread is attached to it.

An energy source is connected to the ends of the thread, which can be a battery with a voltage of 11.7-12.4 V. To regulate this indicator, a thyristor regulator circuit is used. The regulator can be taken from an electric grinder. You can also control the voltage using a spiral on a polystyrene foam cutting machine.

This spiral is mounted on a wooden block, to which the upper edge of the filament is attached. Connected to the wire in series. Its function is to lengthen the nichrome thread and, accordingly, reduce the voltage. This can be achieved by changing the place of connection to the nichrome spiral. The shorter the distance, the more the thread heats up and the more the foam melts.

If a transformer is connected to the machine, it must be galvanically isolated. In this case, a transformer with taps must be used.

For smooth and even cuts, you need to make a guide rail. It is made from a bar or any other even material.

With the help of such a simple machine, foam cutting is carried out with your own hands. Additionally, you can make different devices. You can make a miter box with your own hands or a tray during the repair, which will help you cut the material evenly at the right angles.

3D foam cutting technology

Expanded polystyrene products have become widely used for marketing and decorative purposes. Company logos are made from expanded polystyrene, names, various figures, decorative elements, etc. are cut out. Therefore, 3D cutting has gained wide popularity. The use of foam allows you to save money and at the same time get a high-quality and durable product.

Volumetric cutting is carried out on special machines. They cut the material using long strings or a laser and allow you to give the foam any shape.

Figured cutting of foam

Figured cutting of expanded polystyrene is carried out on special machines. Some of them are equipped with CNC. When working on the machine, the thickness of the foam sheets does not matter. However, for simple cutting, you can use a simple do-it-yourself cutter.

Heat and sound insulating building materials on the market are presented in a wide range, these are foamed polyethylene, mineral and basalt wool and many others. But the most common for insulation and soundproofing is extruded polystyrene foam and foam plastic, due to its high physical and chemical properties, ease of installation, low weight and low cost. Polyfoam has a low coefficient of thermal conductivity, a high coefficient of sound absorption, and is resistant to water, weak acids, and alkalis. The foam is resistant to the effects of ambient temperature, from the lowest possible to 90˚C. Even after decades, the foam does not change its physical and chemical properties. The foam also has sufficient mechanical strength.

Styrofoam also has very important properties, these are fire resistance (when exposed to fire, the foam does not smolder like wood), environmental friendliness (since the foam is made of styrene, even food products can be stored in containers from it). Fungi and foci of bacteria do not appear on the foam. An almost ideal material for insulation and soundproofing in the construction and renovation of houses, apartments, garages, and even packaging for food storage.

Styrofoam is sold in building materials stores in the form of plates of different thicknesses and sizes. When repairing, foam sheets of different thicknesses are often needed. With an electric foam cutter, you can always cut sheets of the desired thickness from a thick plate. The machine also allows you to turn the shaped foam packaging from household appliances into plates, as in the photo above, and successfully cut thick sheets of foam rubber for furniture repair.

How easily foam is cut on a homemade machine, the video clip clearly demonstrates.

If you want to make a cutter for foam plastic and foam rubber, many are stopped by the difficulty of organizing the supply of supply voltage to heat the nichrome string to the desired temperature. This obstacle can be overcome if you understand the physics of the issue.

Machine design

The basis of the device for cutting foam was a sheet of chipboard (chipboard). The size of the plate must be taken based on the width of the foam plates that are planned to be cut. I used a 40x60 cm furniture door. With this size of the base, it will be possible to cut foam plates up to 50 cm wide. The base can be made from a sheet of plywood, a wide board, and the cutting string can be fixed directly on the desktop or workbench.

Stretching a nichrome string between two nails is the limit of the laziness of a home craftsman, so I implemented the simplest design that provides secure fixation and smooth adjustment of the height of the string during cutting above the surface of the base of the machine.

The ends of the nichrome wire are attached to the springs, dressed on M4 screws. The screws themselves are screwed into metal racks pressed into the base of the machine. With a base thickness of 18 mm, I picked up a metal stand with a length of 28 mm, so that when fully screwed in, the screw does not extend beyond the bottom side of the base, and when the maximum unscrewed state provides a foam cutting thickness of 50 mm. If you need to cut sheets of foam or foam rubber of greater thickness, then it will be enough to replace the screws with longer ones.

To press the rack into the base, first a hole is drilled in it, with a diameter of 0.5 mm less than the outer diameter of the rack. In order for the racks to be easily hammered into the base, the sharp edges from the ends were removed on an emery column.

Before screwing the screw into the rack, a groove was machined at its head so that the nichrome wire could not move arbitrarily during adjustment, but occupied the required position.

To make a groove in a screw, first its thread must be protected from deformation by putting on a plastic tube or wrapping it with thick paper. Then clamp the drill in the chuck, turn on the drill and attach a narrow file. In a minute, the groove will be ready.

To prevent sagging of the nichrome wire due to elongation when heated, it is fixed to the screws through springs.

A suitable spring from a computer monitor, used to tension the ground wires on the kinescope, turned out to be suitable. The spring was longer than required, I had to make two of it, for each side of the wire attachment.

After preparing all the fasteners, you can fix the nichrome wire. Since the current consumed during operation is significant, about 10 A, for reliable contact of the current-carrying wire with nichrome wire, I used the method of fastening by twisting with compression. The thickness of the copper wire at a current of 10 A must be taken with a cross section of at least 1.45 mm 2. You can select the wire section for connecting nichrome wire from the table. I had a wire with a cross section of about 1 mm 2 at my disposal. Therefore, each of the wires had to be made of two with a cross section of 1 mm 2 connected in parallel.

If the electrical parameters of the nichrome wire are not known, then you must first try to connect a low-power electrical appliance, for example, a 200 W electric light bulb (a current of about 1 A will flow), then a 1 kW (4.5 A) heater, and so increase the power of the connected devices until the nichrome the torch wire does not reach the correct temperature. Electrical appliances can also be connected in parallel.

The disadvantages of the last connection scheme for a nichrome spiral include the need to determine the phase for proper connection and low efficiency (coefficient of performance), kilowatts of electricity will be wasted.