Styrofoam boards are a thick and highly porous material, they consist of more than 95% air, and it is difficult to cut them if you are not used to them. How to cut foam depends on the type of cut, the availability of a tool and the amount of cutting work.
Ordinary polystyrene - terminology and material characteristics
In a broad sense, foam plastics are an extensive class of cellular (foamed) plastics based on polyurethane, polyvinyl chloride, urea, phenol, and even formaldehyde. All these materials are united by a minimum density and an internal structure in the form of often located and small gas cavities. However, in practice, one has to deal with the only type of foam - low-pressure polystyrene foam, abbreviated PSV.
Only it has an affordable cost, all other cellular plastics in production are much more expensive and are rarely used in the construction and repair business. The international name for low pressure expanded polystyrene (PSV) is the trade name styrofoam, patented by the developer BASF back in the 50s of the XX century. Documentation for imported foam often uses the abbreviation EPS. For practical purposes, it is important to know that all these terms - styrofoam, PSV andEPS - denote an ordinary and well-known from childhood polystyrene foam.
The structure in the form of small gas pores and the significant dimensions of the plates determine the main operational advantages of the foam:
- Excellent thermal insulation from any side of the house. It is possible to perform, it is possible to carry out this procedure from the outside, it is possible to combine external and internal thermal insulation, and the cost of such a “double” protection will still be lower than the estimate for a newfangled roll insulator;
- Excellent acoustic protection of the premises. In fact, sound comfort is already achieved during thermal insulation work - if frost cannot penetrate the foam layer, then loud sounds are even more unable to do so;
- Environmental Safety. The foam is absolutely non-toxic, including on exposed cut lines and with prolonged use. Some varieties are allowed to come into contact with food, which is regulated by European quality standards (!). Moreover, polystyrene is safe during repairs; there is not the slightest need to try “by the tooth” the walls pasted over with it;
- High resistance to mold, dampness, microorganisms, fungi, algae and other unwanted companions of human life. In order to enhance the durability of such consumer qualities, do-it-yourself foam cutting must be done accurately and competently;
- Ease of installation due to miniature weight. This quality greatly simplifies the transportation and laying of the foam, however, when working outdoors, you should pay attention to possible "wind difficulties" - even a slight breath of a breeze will easily carry away the foam blank.
Of course, before any use of the foam, it is necessary to take into account possible complications. Firstly, this material is destroyed by exposure to most technical fluids - from acetone and gasoline to white spirit and enamel solvents. This destruction is intense even with the vaporous action of technical fluids on the foam.
Secondly, it is necessary to pay special attention to the expected operating temperature of the surface pasted over with foam. Already at +50 ˚C - +60 ˚C, some types of foam boards begin to crumble, their internal bubbles combine into extensive gaps and cavities. Painting surfaces insulated with foam plastic must be thought out in advance, otherwise the thermal comfort of the entire room will suffer from toxic nitro paint.
To repair kitchens, saunas and brightly lit facades, foam plastic should be used with great care - high temperatures destroy it.
Areas of application for foam...
… are not limited to the construction and repair direction. Foam boards and sheets are widely used in the following areas of human activity:
- In medicine - cases for equipment, packaging for glass and sharp objects;
- In the organization of active leisure - inserts in life jackets, the contents of buoys, floats;
- In the repair of refrigeration and climate equipment;
- In shipbuilding, as an unsinkable compartment filler on small vessels (boats, boats);
- For design purposes, in construction and modeling.
So, not only for or thermal protection of walls, the question of how to cut polystyrene is relevant. You can make a boat model from it, build a protection for the refrigeration circuit in an air conditioner, or make a decorative figurine of a unique design. The light weight and affordability of the material should not be misleading about the simplicity of its machining - foam cutting has a number of its secrets and tricks.
How to cut foam at home - simple and effective ways
Cutting small pieces of foam (for modeling-construction) is done with a well-sharpened knife with a rubber tip on the tip. It is advisable to secure the workpiece in a vise or other auxiliary device. The fact is that it is easy for a steel blade to slip off a small part, and there is a chance of cutting yourself. All movements when cutting small foam blanks should be directed “away from you” and to the side.
For particularly precise cutting of foam elements, you can use a soldering iron with a special nozzle-knife. With light movements of the heated blade, the material is given the necessary shape of an arbitrary type. You should be careful about the danger of getting hot drops of plastic on your hands or other parts of the body. If it is necessary to cut sheet foam, with precise fitting of parts for continuous installation, the following techniques are used:
- For sheets up to 40 mm thick - an ordinary shoe knife with a wide blade and a blunt point. Before work, the blade is sharpened, and in general the sharpener must be kept at hand - every 1.5-2 meters the knife will have to be corrected again. The work will be accompanied by a characteristic "squeal" of the foam being cut, so it does not hurt to stock up earplugs or headphones. Knife cutting is good for fitting the sheet to a specific mounting dimension, for example when installing the final strips of thermal insulation;
- Hacksaw, but with fine teeth, suitable for sheets of thickness< 80 мм. Чем меньше величина зубцов, тем точнее и ровнее будет срез. При резке с помощью ножовки прикладывается гораздо меньшее усилие, чем при использовании самого острого ножа, да и вероятность травматизма куда меньше. Способ актуален при необходимости длинных, прямолинейных разрезов однотипного характера;
- Hot wire cutting is the best and most productive way to cut foam. Unfortunately, it assumes a stationary location of the cutting tool, but it has no equal in terms of speed and accuracy of cutting.
We need a long knitting needle, nichrome wire, a 12-24 volt step-down transformer, an adjustable rheostat and electrical wires of sufficient cross section. Electrical components are assembled in a serial circuit, the knitting needle is fixed on the layout, a nichrome thread is pulled between its ends. When a small current is applied, nichrome heats up and easily cuts the foam of arbitrary thickness.
An additional advantage of nichrome cutting is that with it the "bubbles" of the foam structure are re-soldered. Thus, the thermal insulation qualities of cut blanks are not inferior to factory sheets; when processed with a hacksaw or a knife, such a property is unattainable.
Styrofoam is a fairly popular building material. It is used for heat and sound insulation of rooms. In the process of construction work, this material requires processing, in particular, cutting to the required parameters. For cutting foam, there are many options that are applicable at home.
The procedure for cutting foam requires compliance with certain rules, since the material, if handled improperly, can break, crumble. To perform foam cutting, a variety of tools are used, for example, a good knife, a soldering iron, a file with fine teeth for wood, metal, nichrome wire, a grinder (only for thin foam).
Consider several ways to cut polystyrene foam materials.
In this article
You can make at home with your own hands a special device for processing (cutting) foam. To do this, you need to purchase a step-down transformer, string, springs, with which the string will be stretched, a pipe with a thickness of 2 cm or more for lining. The thickness of the expanded polystyrene plate itself, which will be cut, must be at least 2 cm.
To equip the countertop for this equipment, you need a table, a profiled sheet, a board. It will not be difficult to make such a device for cutting polystyrene foam at home.
Curly cutting
Recently, figured cutting of foam plastic, for which a thermal cutter is used, has been quite in demand. The cutting element in this case is a nichrome wire, fixed on an equipped handle made of insulating material. The thermal cutter makes it possible to make recesses of various shapes in polystyrene foam.
After such treatment, a melted crust is formed on the surface of the material, which gives greater strength to the material, but also overlaps the pores. Therefore, it is necessary to use a step-down transformer, which is manufactured independently. You just need to purchase specialized transformer iron.
To choose the right amount of current, it is necessary to make a rheostat, for which you can use a spiral of an electric stove, pre-stretched. To make a winding frame, you can use a ceramic or asbestos-cement pipe (pipe parameters: thickness 1.5-2 cm, length 8 cm). Nichrome wire must be wound on the pipe until the frame is completely filled.
Knife cutting
When insulating a floor or ceiling with foam boards, it is not at all necessary to use special equipment.
To cut polystyrene foam at home, you must have:
- Good knife.
- The ruler is over one meter long.
- Pencil.
The procedure for cutting polystyrene foam boards in this way is quite simple:
- Preliminarily, on the surface of the material, the points of the beginning and end of the cut line are marked with a pencil.
- Next, a ruler is applied to these marks, clamped, and an incision is carefully made along it with a paint knife (it is not necessary to completely cut off a piece of foam).
- The polystyrene foam plate is turned over to the other side, and an incision is made in the same way, parallel to the already made incision.
- After making the cuts, you just need to break the foam along the line.
This method of cutting material is the cheapest, quietest and fastest, and after the work is completed, there is practically no debris. Be sure to check the sharpness of the knife before starting cutting the foam.
Using a hand file
It will be very difficult and inefficient to cut a foam slab of greater thickness than 50 mm with a knife. If you use an electric jigsaw, there will be a lot of debris, and the cut line will not work out even. Therefore, the best option for cutting polystyrene foam up to 10 cm thick at home with a hand saw.
Foam Cutting Machine
Expanded polystyrene is a good insulation, an excellent raw material for various decorative elements that you can make yourself. For decorative cutting of foam, you need a specialized machine. There are many options for such equipment, it all depends on the intended design of the product.
The material can be cut using a tungsten filament. It should be noted that this thread is hot, but its temperature can be adjusted. Other materials can be cut with such a thread in addition to polystyrene. This is especially true in the manufacture of various components intended for stucco molding.
The necessary stencil is applied to the expanded polystyrene plate, and an object is created using a tungsten filament. This procedure is not difficult, does not take much time.
Also, for equipment, you can use a construction blade, a cutter. The device of the machines may differ, but the principle of operation remains the same - the use of a tungsten filament that is connected to the mains. With the help of such a device, you can independently produce decorative elements from polystyrene foam of any configuration.
- Tungsten filament.
- string.
- Thermal cutter.
If you assemble the cutting machine correctly, then there will be no difficulties in the process of work. The main thing is to use a quality tool, to show maximum diligence and care. And to perform such work, you will not need to contact experienced craftsmen.
Cutting polystyrene with a grinder
Cutting a polystyrene foam plate can be done with a grinder, using a metal disc for this work (you need to choose the thinnest disc).
Such a cutting option is not sufficiently efficient and comfortable, since the work is accompanied by a lot of noise, and after their completion a large amount of debris remains.
Cutting polystyrene foam with a soldering iron
Expanded polystyrene plates are excellent for processing using a soldering iron. This tool allows you to complete the work in the shortest possible time. To carry out such work with a soldering iron, its end must be flattened with a hammer. It is necessary to put on a specially prepared part, which is pre-made from a blade, a cap of a fountain pen, made of steel.
The blade is mounted on the end of the soldering iron. After heating the resulting tool, the material can be cut.
Expanded polystyrene lends itself perfectly to coloring, so the decorative elements obtained as a result of cutting can be painted. Each option for cutting foam has its own advantages, but it is recommended that you choose the one that will be less difficult for you.
Styrofoam is used by builders for a variety of purposes. This material exhibits high thermal insulation qualities, so they insulate the facades of buildings, floors and other objects. Also, various decorative elements are made from this material.
Styrofoam is easy to handle and easy to cut. But at the same time, the material can crumble a lot. The destruction of the array is a negative phenomenon. Therefore, it is necessary to properly handle this material, you need to know before starting work. At the same time, it will be possible to create not only plates for insulation, but also decorative products from an array of foam plastic. Their appearance will be neat, and the material will not collapse.
Styrofoam Features
Styrofoam is a lightweight material in all respects. The polymer is mixed with air and foam filling components. Its structure is similar to glued balls. It is this feature that explains why we cut the foam, and do not break it. Otherwise, the cutting will be uneven.
In some types of material, the balls of the structure hold tighter and do not crumble. But quite often the foam crumbles, and sometimes very much. Such destruction of the material is dangerous for the sheet. The fragility of the foam leads to a change in shape, a decrease in properties and functional qualities.
If you want to adjust the dimensions of the array, this operation is carried out using a special tool. In this case, the sheet will not collapse.
Types of tools
When studying the question of how to properly cut foam at home, you need to pay attention to the types of tools. They are divided into mechanical and thermal. For independent cutting of the array, with small amounts of work, the first group of tools is preferred.
For home processing of foam, novice craftsmen are advised to choose a mechanical tool. Professional installers and designers prefer thermal cutting. In this case, it will be possible to create high edge accuracy, create objects of any complexity.
The thermal cutter is quite expensive. Novice craftsmen who make repairs at home rarely purchase such equipment. But with large volumes of work, it is simply irreplaceable. Actions with the help of a thermal cutter are carried out quickly and efficiently.
Tool production method
Considering the question of how to properly cut the foam so that the sheet does not crumble, you should consider in more detail the method of manufacturing the tool. It can be factory or homemade.
Professional builders without fail acquire special certified equipment. Whether it is a mechanical or thermal tool, for such purposes it is necessary to carry out work with factory-made equipment. The fact is that when creating such devices, the developers maximally provided it with all the necessary qualities, safety and comfort. This is very important when doing a lot of work.
But, making repairs with your own hands, it is unprofitable to purchase special equipment. In this case, you can create it yourself. It will be a more primitive device, but it will be able to cope with the tasks assigned to it.
Mechanical cutting
First of all, you should consider the main mechanical devices with which you can cut the foam. How to cut the material depends on the abilities of the master and the amount of work. These tools include a knife, grinder, saw and jigsaw. For independent cutting of plates in the process of arranging a layer of insulation, it is better to use a knife. Its blade should be of medium hardness. Such a tool allows you to quite efficiently and quickly cut plates up to 8 cm thick.
A jigsaw, grinder or saw is used only for special work. Professional builders use such equipment. In this case, the tool differs in a number of parameters from conventional angle grinders, jigsaws or saws.
If a thick blade and high RPMs are used, the foam can be easily damaged. Therefore, at home, a knife with replaceable blades is used for cutting.
Thermal cutter
Thermal equipment allows to achieve high cutting accuracy. It is purchased by professional craftsmen and designers. When carrying out a large amount of work at home, this type of equipment should also be paid attention to. In this case, we cut the foam
The device is powered by the system or battery. Through the elements of this technique, electricity is supplied to the nichrome thread. At the same time, the metal heats up quickly and strongly. This allows you to qualitatively cut off excess foam, cut it in any direction.
The most accurate processing of the material is obtained when using a thermal cutter. It should be noted that the foam does not respond well to heat, but in this case the cut is made very quickly. Therefore, its quality is high.
homemade cutter
You can create a thermal cutter yourself. To do this, you need to collect a set of necessary parts. First of all, you need a small transformer. You can take this part, for example, from an old TV.
In this case, you will also need to cut the foam with a nichrome string. It is pulled between two long screws. They must be fixed on a wooden plank. Such a material, as you know, does not conduct current. Therefore, electricity from the transformer will only go to the screws and the string.
After connecting all the elements, the voltage should be corrected. It depends on the thickness. A string that is too hot will not allow you to cut the material with high quality.
Easy way to cut
The presented approaches make it easy to cut the foam. How to cut such material, folk craftsmen give advice. They came up with another way. It will be quite effective, especially when cutting large sheets of foam.
This will require a thin and strong string. Its ends are tied to wooden handles. If the sheet is large, you need to do the work with an assistant. In this case, 2 people become on both sides of the array. Everyone takes a wooden handle with a string attached. Further, along the markup drawn in advance, they move the thread. It heats up from friction.
The material cuts easily and quickly. If the sheet is small, this procedure can be performed independently.
You should take into account a few tips from professional installers that allow you to process foam. How to cut it, it will be easy to choose. Experts say that each of the presented methods is suitable for cutting. It all depends on the skills of the master and the amount of work he does.
Before cutting, the material must be marked with a simple pencil. With the mechanical and thermal method, the foam can heat up. In this case, it releases harmful substances into the environment. Therefore, the work is carried out in the open air.
In this case, special equipment is used. Otherwise, when heated, the material will stick to the blade. Bulgarian or jigsaw work at low speeds. So heat has time to be removed from the cutting zone.
Styrofoam or expanded polystyrene refers to a universal material that is used for insulation and sound insulation in building structures. The basis of its structure is formed by foamed plastic. This explains why the foam often crumbles when cutting.
When processing the material, it is necessary to decide how it needs to be cut so that the cut line is even and the crumbs are as small as possible.
Types of tools
Styrofoam cutting is carried out using mechanical and thermal types of tools. For beginners, especially with small cutting volumes, it is recommended to use a mechanical tool.
Mechanical cutting . The most common tools at hand include a knife, a jigsaw, a saw and a grinder.
Ordinary knife
. The main focus when choosing a knife is its blade. If it is sharp, then the cutting process is faster, and less waste is generated. The knife must be preheated before cutting.
The disadvantage of this method is that the use of a knife is possible with a foam thickness of 1-5 cm.
shoe knife . As a rule, this knife is initially quite sharp. Therefore, its blade is relatively easy to pass through the cellular structure of the foam.
Disadvantages in use:
- the ability to cut only thin sheets;
- the blade of the knife becomes dull quickly;
- the need to have a grindstone available.
stationery knife . The clerical version of the knife is best used for soft material. This knife has thin and flexible blades, so it is not practiced for processing thick plates.
Advantages:
- little garbage;
- availability of acquisition;
- low cost.
The stationery knife has a set of interchangeable blades. Blunt blades break off, which leads to their high consumption.
It is recommended to heat the blade before direct use. Then the plastic capsules will melt, and the crumbs will form much less.
Trimming with a jigsaw is used when cutting foam up to 10 cm in thickness. This method does not require much effort. 
Disadvantages:
- the cut is not perfectly even;
- a sufficient amount of crumb is formed;
- cannot be used in the absence of power supply
Hand saw for wood
. If the thickness of the foam reaches 40 mm, then it is better to cut it with a hacksaw for wood. The method is quite simple and fast, without the cost of special physical effort.
A saw with fine teeth is better. This tool is only used for making straight cuts.
"Bulgarian" . The advantages of the grinder are that it, as it were, cuts the foam itself, if you use the thinnest circles.
However, it is not recommended to cut thick material with a grinder. You will not get a qualitative result, but there will be an extremely large amount of garbage.
In addition, this option is not very good due to the screeching that occurs when the foam plastic interacts with the circle of the machine. Plus, the noise of the tool's engine is added to it. Therefore, in the case of cutting a large number of foam plates, you should wear headphones from the very beginning. Add to this list also the cost of electricity that you need to pay.
Nichrome wire cutter . The practice of working with foam shows that a high-quality cut is formed when using a tool with a heated wire. The edges are even, smooth, and there are practically no crumbs. The advantages of the method include high cutting speed and productivity in volumes similar to industrial ones.
The active use of the method is hampered by the difficulty of acquiring it due to the lack of it in stores. With an urgent need for a machine, there is only one way out - to make a cutter yourself. This is a separate question, which is devoted to many good articles on the Internet, containing step-by-step instructions and illustrations.
Easy way to cut
Cutting can be done with thin steel wire. It should be fixed on wooden handles. They are located at different ends of the surface intended for cutting. Sawing resembles the process of sawing firewood. You will need an assistant who will take one of the pens. Friction heats the string, so the cut line is even and smooth.
Follow the safety rules, considering that when heated, the formation and release of substances harmful to the body occurs. Work in a well ventilated area or outdoors.
Outcome
From the review, we can make a general conclusion that the process of cutting foam plastic proceeds quite simply and quickly. The processing method is selected depending on the selected tool, the amount of work, the shape (rectilinear, sinuous or volumetric) in which the result is to be obtained.
Thermal insulation structures are assembled from modern expanded polystyrene, decorative elements are cut out and a large number of other things are produced.
Its scope is very wide. And not least due to the fact that this material is easy to process, quickly fits and can be cut with your own hands.
However, you also need to be able to cut the foam with your own hands. After all, to get a really high-quality cut and the final detail, you need to try hard. Note that it is not dangerous.
1 Styrofoam cutting
So, expanded polystyrene, like any other material, needs to be processed before use. Initially, it is supplied in ordinary plates with a certain thickness. However, the shape of the plates is not always enough to use them wherever necessary.
Often the plate has to be cut into pieces, cut, cleaned. Sometimes it becomes necessary to cut off a decorative part on the edge of the slab or make a certain angle.
There are actually a lot of options. But the question remains one. How to cut styrofoam? It would seem, why else invent some additional units, buy a special foam cutter if it’s not something to cut, you can even break it with your own hands. And this is literally.
Here we must turn to the features of the polystyrene itself and. The foam itself consists of small polystyrene beads.
The initial raw material in it is a polymer that is mixed with foam aggregates and air. The result is a rather pliable and very light construction, which is easily cut or broken by hand.
That's just breaking the foam - this is not the best solution. The break line will never be accurate. Styrofoam balls will bend it, making the final design unsuitable for precise work.
However, we still note that it is very easy to break or cut the foam. That is, cutting foam at home is quite real. Another question is how to do this accurately and with minimal damage to the material. This is where a foam cutter or any home-made device will come in handy.
2 Cutting tools
The foam cutting tool can have a different design. It depends on the design and type of cutting how exactly the foam cutter will cope with its tasks.
Cutters are:
- Mechanical on ;
- Thermal.
A mechanical cutter is used in order to be able to carry out relatively small jobs in cramped conditions. It is possible to cut the body of polystyrene foam with a mechanical impact device. That's just the quality of the cut, which will turn out in the end, may not be as we would like.
Thermal foam cutter is already professional equipment. It is used by builders, designers and other similar professionals.
The thermal cutter quickly makes holes or cuts lines in any type of Styrofoam. Ranging from conventional to high density extruded foam.
The thermal apparatus basically uses a hot thread or wire.
According to the type of assembly, the device for cutting polystyrene foam can be divided into:
- Brand samples;
- Homemade samples.
In the first case, we are dealing with units that were created at the factory. They are specially designed and conceived in such a way as to give a person maximum productivity and convenience during work.
Branded models include both specialized foam knives and large thermal cutters or other professional equipment.
For example, the same laser cutting of foam is possible only through the use of low-power factory lasers that are controlled by a computer. They are expensive, bulky and rather complicated, but as a result of working with them you will get an almost perfect cut.
2.1 Mechanical cutting
Mechanical cutting is performed with tools that basically use the force of mechanical action or friction.
These include:
- Knives;
- Bulgarians;
- Jigsaws;
- Saws.
Most often, such equipment is used at home. When you do not have the opportunity to buy a thermal cutter, and there is no desire. Let's not forget that a quality thermal cutter can be quite expensive.
And it’s far from always worth buying, especially if you just need to cut a couple of polystyrene foam plates for thermal insulation with your own hands.
The easiest way to cut foam is to take a regular knife, especially if the foam is cut into. An office knife with a blade of medium hardness is ideal. With it, you can easily cut a slab up to 6-8 cm thick without any problems. Moreover, the slab will be cut with high quality, especially if you already have at least basic experience.
But grinders and jigsaws, if they can be used, then very carefully. Here it is already necessary to understand that a strong torque affects the weak structure of polystyrene foam too seriously. If you don’t guess with the torque and the choice of the disk, then you can ruin the stove with your own hands.
Recommendations here can only be general. It is advisable to buy special equipment for cutting foam. If you don’t have anything like that at hand, then try to at least find the thinnest disc for a grinder or a jigsaw blade. The thinner it is, the better.
With saws in general you need to be careful. It is better not to use a regular saw for foam plastic. Unless you don't need cutting accuracy at all. But in this case, it's easier to just break it.
If you buy a special saw, then there is already a different conversation. But in any case, one must be very careful, since the saw, due to uneven efforts, is more likely to thoroughly damage the material.
2.2 Thermal cutting
For thermal cutting, a thermal cutter is always used. A thermal cutter is a special unit for cutting polystyrene foam, it costs almost the same as.
It consists of only a few parts. The main part is a working transformer that supplies voltage. The transformer may have batteries, or it may be powered directly from the mains. It all depends on the specific model.
Two arcs or fasteners depart from the mini-transformer. These arcs are essentially the body of the work item. A special thread is tied to each end of the arc. Most often used nichrome. The thread is stretched between the ends of the arc so as to form a tightly stretched wire.
When the transformer is turned on, it supplies electricity to the arcs, and they, in turn, glow the thread itself.
The hot thread cuts through the foam in any position and any size without any problems. After all, the polymer is extremely unstable, and it interacts very poorly with high temperatures.
A big plus of a thermal cutter is that it gives you the opportunity to work with filigree precision. More precisely, cutting can only be done with lasers. And even then, if we exclude the human factor.
Nichrome heated to a serious temperature cuts the foam like a knife hot butter. Moreover, he does not even really touch the stove, that is, you do not have to apply any physical pressure. Why is it convenient? Yes, because applying physical effort is always fraught with the possibility of making a mistake.
If all the work is done by a heated wire, which melts the foam rather than cuts it, then the chance of making a mistake becomes minimal.
2.3 Homemade thermal cutter
Smart radio engineers have probably already thought that the design of the thermal cutter is very simple, which means that you can assemble it yourself. And indeed, you can assemble a thermal cutter without any problems.
Your main task will be to select a small transformer for cutting and similar products. Well, it's actually not that much of a problem. You can take a transformer from a TV or convert it from a working sample.
Next, you need to assemble an analog of the arcs. The simplest such mechanism is the fastening of two long screws on a wooden plank. The tree will not allow them to conduct electricity between themselves, so the nichrome stretched thread will remain the only conductor.
The thread is pulled between the heads of the screws. Then it remains only to connect the transformer to the screws, then turn on the electricity and adjust the voltage.
It is advisable not to overdo it with voltage and clearly understand that there is a certain correlation between the thickness of the nichrome filament and the operating voltage at the output.
Too high voltage will make the thread red-hot, and in this position it will simply burn out the polystyrene foam without even touching it. As a result, you will not be able to cut evenly.
2.4 An example of creating a homemade thermal cutter for polystyrene foam (video)