Polystyrene foam is quite practical and lightweight thermal insulation material. It is often used to create various crafts. However, in the process of working with it you have to deal with one trouble - the material is difficult to cut. Polystyrene foam is produced in the form large slabs, and to divide the panel into fragments, you will need to cut it.
Using a saw or knife for this purpose will not work. This is due to the fact that with any mechanical impact the structure of the material is destroyed. To avoid this, you will need to design a foam cutter yourself.
The simplest device for cutting foam plastic
The simplest foam cutter is easy to make with your own hands. For this purpose you will need to use the thinnest guitar string. In addition, you should prepare 5 large batteries for a regular electric flashlight. They must be connected in series. A string is connected to the ends of the device, thereby closing electric arc. Current will flow through the string, heating it.
When using such a device, the foam sheet will split into two parts immediately after touching the string. In this case, the material will melt along the cut edges. With this processing, the cut is as smooth as possible. The string for cutting foam must be heated to a temperature of at least 120 degrees. However, it should not exceed 150 degrees.
Checking how hot the string is is quite simple. During cutting, stuck pieces remain on the edges of the material. If they are too long, the string is not heated enough. In the absence of such pieces, it can be judged that the string is overheated.
When using such a simple device, about 3 foam panels can be processed. However, it is not suitable for large volumes of work. The batteries run out pretty quickly. To extend the operating time of the cutter, you will need to build a device that runs on mains power. A few simple tips will help you understand how to make a foam cutter.
Homemade electric foam cutters
If we divide such devices into groups, they should be classified as follows:
- linear cutting device;
- thermal cutter, which is used to perform shaped cutting;
- device with a metal plate.
However, despite this classification, each device has one common element in its design. To create cutters for foam plastic, you will need to find a step-down transformer. It is necessary that this element can withstand 100 W.
Line cutting cutter
To create such devices, you should prepare a workspace. Usually a table is chosen for such purposes. Two vertical risers are attached to it. Each of them must have an insulator. It is necessary to stretch a nichrome thread between the insulators. A freely hanging load is suspended from it. The nichrome thread is connected to the contacts connected to the step-down transformer.
The operating principle is quite simple. The nichrome thread heats up when connected, which makes it easy to cut foam. Thanks to the suspended weight, the thread remains taut. A weight is necessary because when heated, the thread begins to sag.
The moving foam is cut with nichrome thread quickly and evenly. How thick the processed sheets will be depends on the height of the thread above the working surface of the table. The main thing is that the foam is fed at the same speed throughout the entire cutting period.
To cut sheets vertically, you will need to use a cutter of a different design. In it, the cutting wire is tensioned in a vertical position. In this case, the working surface is made of chipboard. You need to attach a frame to it. It is better if this element is made of a metal profile. However wooden blocks will fit well.
The frame is equipped with a paw-holder, on which the nichrome wire is suspended. A weight is attached to its end. The wire is passed through a hole made in work surface. To prevent it from touching the wood, the hole is protected from the inside with a metal hollow tube.
When using thermal cutters, foam plastic is not only easily cut into specific blocks. From large slabs you can cut various geometric figures, such as square, semicircle, triangle. Before work, just run a marker along the surface of the slab, marking the cut line.
Shape cutter
When working with foam sheets big size using a stationary cutter will be difficult. Such panels hardly fit on the desktop. In these cases it is used hand cutter for foam plastic. This tool is often made from a jigsaw. The cutting blade in these tools should be replaced with nichrome wire.
It’s quite easy to build such an electric cutter with your own hands. To make cutting shaped elements more convenient, you can make several devices that have various shapes. First, remove the cutting blade from the jigsaw and connect the wire to the handle. The voltage will be low, but the handle and other metal parts should be insulated. Nichrome wire is connected to the cable. Nuts are used for this. The wire is bent in a certain way.
You can use a soldering iron as a cutter for shaped cutting of foam plastic. It needs to be modified a little. The device already has in its design electrical wire. To create a foam cutter from a soldering iron, you will need to replace the element that heats up with nichrome wire.
This device is highly convenient to use. Thanks to this product, it is possible not only to cut slabs of material into smaller sheets, but also to make recesses in them.
Metal plate cutter
There is another way to convert a soldering iron into a foam cutter. To modify the tool, you simply need to replace the tip with a copper plate. Steel will also work, but it takes longer to heat up and is more difficult to sharpen. However, when correct sharpening A steel plate can be used to cut any synthetic material, including polystyrene foam.
One side of the plate must be carefully sharpened. Sharpening can be done on both sides. It is necessary that the sharpening angle is not too large. The cutting of the material is carried out not only by the blade, but also by the blade of the plate. Such a cutter has one drawback - you will have to empirically find optimal temperature heating the knife.
conclusions
Making a foam cutter with your own hands is quite simple. The methods listed above will help you understand the structure and operating principle of the foam cutter. Such devices are practical and easy to assemble. Each method has its own advantages, so home craftsmen can choose the most suitable one, depending on the available materials.
Those who are planning to insulate an apartment or a newly built house with their own hands should definitely familiarize themselves with the methods by which foam plastic is cut at home, because this is one of the most popular and available ways isolation.
Foam is a foam material and is mostly air, so it is very light and easy to work with. However, you should not think that no problems arise, because besides everything, foam is a rather fragile material. Therefore, if you use electric grinder, then you shouldn’t hope for smooth edges, and besides, the entire room and area will be strewn with crumbled foam.
No matter how sharp the knife is, the material will still crumble. Of course, this is a minor defect and the sheets will be suitable for use, but cleaning will turn into a troublesome task. There is a way out of this situation; you can use a thermal knife. In this case, the edges of the material are melted and it does not crumble. But bad luck, such a device costs a lot, but in principle you can heat an ordinary knife. However, in this case you need to be very careful so as not to get burned, and the work will be significantly delayed.
For this purpose, you can use various cutting tools, for example, a grinder, only then you should use the thinnest disk. Very often builders use simple sharp knife. Sometimes it is advised to use a hacksaw with very fine teeth, but the latter method is very questionable. In addition, stores sell special thermal knives designed for working with foam plastic.
The thermal knife heats up to 600 °C in just 10 seconds. However, this tool is quite expensive, so it doesn’t always make sense to buy it.
The way out in many cases will be a device for cutting foam sheets, made independently. It is probably somewhat cumbersome, but if you have the necessary components, it is absolutely free and always available. And if you have to do large-scale work, for example, you have in front, which you built for your big family, then the question of how to conveniently cut foam plastic, and even a lot and quickly, will not come up throughout the entire event, no matter how long it drags on.
In order to assemble a foam cutter, you will need a table top, a pair of springs, M4 screws and 28 mm long stands, as well as nichrome thread, which will act as cutting tool. First, we make two holes in the base, press the posts into them, and cut a small groove at the base of the screw head, thanks to which the thread will be securely fixed in the given position.
When everything is assembled, we attach the string to the screws, but since it can sag during heating, it should be connected through springs, then the thread will always be in a tense position. The power source is connected to such a device using ordinary twists. This way you can make a homemade and very effective foam cutter, while spending a minimum of effort, time and money.
Trying to cut the foam yourself
Now let's talk a little about various technologies, methods and, of course, we present detailed instructions what to do and how to do it.
How to cut polystyrene yourself - step-by-step diagram
Step 1: Preparatory work
It doesn’t matter what kind of tool you are going to use - a knife, nichrome thread or other cutting devices, you still need to start with markings. So we take a ruler, a square, a tape measure, a pencil and make marks on the surface of the sheet, then we connect them into lines. In general, we draw the contours of the future section.
There are other ways you can. For example, using nichrome thread. In this case, a small current is supplied to it, which is capable of heating the string to the desired temperature, and cutting is carefully carried out along a given contour. Of course, the quality of the cut in this case will be much better, but you will have to work a little to make the machine. Therefore, this method is not always justified if you need to process only a few sheets; there is simply no point in spending time constructing a device. As you can see, it is impossible to give a definite answer as to what is better for cutting foam, it all depends on the volume and skills.
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 sound insulation is extruded polystyrene foam and polystyrene foam, due to its high physical and chemical properties, ease of installation, low weight and low cost. Polystyrene foam has a low thermal conductivity coefficient, high coefficient sound absorption, resistant to water, weak acids, alkalis. The foam is resistant to ambient temperatures, from the lowest possible to 90˚C. Even after decades, foam plastic does not change its physical and chemical properties. Polyfoam also has sufficient mechanical strength.
Foam plastic still has very important properties, this is fire resistance (when exposed to fire, polystyrene foam does not smolder like wood), environmental friendliness (since polystyrene foam is made of styrene, even food products). Fungi and pockets of bacteria do not appear on the foam. Practically perfect material for insulation and sound insulation during the construction and renovation of houses, apartments, garages, and even packaging for food storage.
In shops building materials foam is sold in sheet form different thicknesses and sizes. When repairing, foam sheets of different thicknesses are often needed. In the presence of electric cutter polystyrene foam can always be cut into sheets from a thick plate required thickness. The machine also allows shaped foam packaging from household appliances into slabs like the photo above and successfully cut thick sheets of foam for furniture repair.
The video clip clearly demonstrates how easy it is to cut polystyrene foam on a homemade machine.
When wanting 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 plastic was chipboard sheet(chipboard). The size of the slab should be taken based on the width of the foam plates that are planned to be cut. I used a furniture door measuring 40x60 cm. 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, wide board, secure the cutting line directly to the work table or workbench.
Pull on nichrome string between two nails is the limit of laziness home handyman so I implemented the simplest design, providing reliable fixation and smooth adjustment height of the string during cutting above the surface of the machine base.
The ends of the nichrome wire are attached to springs mounted on M4 screws. The screws themselves are screwed into metal posts pressed into the base of the machine. With a base thickness of 18 mm, I selected metal stand 28 mm long, based on the calculation that when fully screwed in the screw does not go beyond bottom side base, and when twisted to the maximum, it provided 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 stand into the base, first a hole is drilled in it, with a diameter 0.5 mm smaller than the outer diameter of the stand. In order for the posts to be easily hammered into the base, the sharp edges from the ends were removed using 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 would occupy the required position.
To make a groove in a screw, you must first protect its threads from deformation by putting on a plastic tube or wrapping it in thick paper. Then hold it in the drill chuck, turn on the drill and attach a narrow file. In a minute the groove will be ready.
To prevent nichrome wire from sagging due to elongation when heated, it is secured to the screws through springs.
A spring from a computer monitor, used to tension the grounding conductors on the kinescope, turned out to be suitable. The spring was longer than required, so we had to make two of it, for each side of the wire fastening.
After preparing all the fasteners, you can fasten the nichrome wire. Since the current consumed during operation is significant, about 10 A, for reliable contact of the current-carrying wire with the nichrome wire, I used the fastening method by twisting and crimping. Thickness copper wire at a current of 10 A, it is necessary to take a cross-section of at least 1.45 mm 2. You can select the wire cross-section for connecting nichrome wire from the table. I had at my disposal a wire with a cross-section of about 1 mm 2. 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 should first try connecting a low-power electrical device, for example light bulb 200 W (a current of about 1 A will flow), then a heater of 1 kW (4.5 A), and so increase the power of the connected devices until the nichrome wire of the cutter heats up to the desired temperature. Electrical appliances can also be connected in parallel.
The disadvantages of the latest connection scheme for a nichrome spiral include the need to determine the phase for correct connection and low efficiency (coefficient useful action), kilowatts of electricity will be wasted.
Sometimes you need to process the foam, give it the required form, trim, cut... You can use a knife for this, but it is inconvenient, the cuts are not always even, it is difficult to cut the material, and even the sound is terribly annoying to most people. You can heat the knife, but this is inconvenient as it will constantly cool down. We will make a small and simple cutter for foam plastic and more.
The basis for the foam temperature cutter will be a small wooden block. You can choose any dielectric handle for yourself or carve it, for example, into lathe beautiful and comfortable. The one like the one in the photo suits me, it’s comfortable to work with, it has the shape rectangular parallelepiped, its length is 13 cm, and its width and height are 1.4 cm.
Our thermal cutter will not exactly cut the foam, but melt it. It is very convenient to give any shape to a piece of foam plastic with such a cutter and you can get the hang of it and make real masterpieces. Heating element serves as a small piece of metal wire having a large resistivity, the thickness (diameter) for me is about 0.6 mm. Examples of such metals and special alloys: tungsten, nichrome, constantine, fechral, chromal. You can buy wire made from such metals, and if you can’t find it on sale, then remove it from an old hair dryer, toaster, or some other simple appliance in which something is heated. A small piece of wire will act as a resistor, which is supplied with a current greater than it should be, as a result of which such power is dissipated on it that it heats up.
You will not be able to solder a wire to a high-resistance wire with a regular soldering iron, no matter how hard you try, you can, of course, first transfer some copper to the ends by electrolysis, but we will secure it to a bar with a pair of nails or screws.
You can use many things as a current source, for example, a low-power transformer, pulse block nutrition. AC voltage from the transformer winding you don’t even need to straighten it with a diode bridge. If there laboratory block power supply, adjust the volts or limit the amps to a value that will desired temperature for melting foam or other similar materials. I often use a 12 Volt power supply - 0.5 Ampere (with long service life heats up noticeably). The wire running from the burner to the energy source must be elastic and withstand constant bending, for example, it can be a specialized acoustic cable. The load will be connected through a small 5.5 x 2.1 mm power socket.
If you want to make a thick tip or, for example, in the shape of a knife, then it will have very little resistance. To warm up such “stings” you need to apply small value voltage, volts, two, three. Transformers with such a miniature output voltage are rare, so if you are rewinding an ordinary one, then remove the standard secondary winding and take several pre-connected in parallel copper wires to get a total diameter of about 5 mm, the maximum current depends on it. It is also worth remembering that if the current transformer is designed for low power, then you will not get a large current and voltage out of it. It will be very cheap to buy a power supply unit for fluorescent lamps (electronic transformer) and remake it; there are a lot of instructions on the Internet on how to turn such a thing into a normal UPS.
It turns out that the cutter reaches operating temperature instantly, and even after disconnecting from the power it cools down. Therefore, in order not to waste energy in vain and not once again overload what gives us voltage, we attach a miniature tact button to the gap. Look at the permissible current in this button so that it can withstand such a powerful load.
You can give your cutter any shape you like. I ended up with something like a heating saw knife. In this case, a thick wire almost does not heat up due to its low resistance, but a cutting wire, on the contrary, heats up well. If I connect a low-power power supply, the filament just heats up, and if I take a powerful transformer, the nichrome filament just gets red-hot, it looks cool (it shines very brightly in the dark, just like an incandescent lamp!), but this heat I just don't need it.
Polystyrene foam is universal material. It is used in construction (insulation), in the production (repair) of household electrical appliances, interior design, and advertising. One of the main characteristics of the material is density. The higher this indicator, the stronger material. However, this greatly affects the price.
When using material as a filler for wall insulation, the loosest structure is usually chosen (due to low cost). However, loose foam is difficult to process - when cut, it crumbles heavily, creating difficulties when removing debris.
The knife for cutting foam must be thin and sharp, but this does not prevent the edge from breaking. Even if you work outside, flying small balls clog environment.
That's why professional builders foam is cut using nichrome wire or a hot plate. The material is fusible, despite fire safety.
Important! When choosing insulation, pay attention to the characteristics. It should say “self-extinguishing.” Such foam is perfectly cut using temperature, but in the event of a fire it will not become a source of combustion.
An industrial foam cutting machine can process sheets of any size and cut the material both across and along the massif.
However, cutting foam plastic at home does not involve such volumes and sizes. At repair work In your home (or garage), a compact thermal knife is quite enough. It can easily cope with both linear cutting and shaped fitting of slabs when laying in areas with complex shape.
Any tool has a cost, and there is always an opportunity to save on your purchase.
DIY tools for cutting foam plastic
The guillotine is perfect for linear cutting. Only the impact will not be mechanical, otherwise a lot of debris will be formed. We use proven technology - cutting foam plastic with a heated tension string.
Required materials
- Nichrome (tungsten) thread
- Power supply, preferably regulated
- Any construction materials: timber, metallic profile, pipe, for making a tension frame
- Furniture drawer guides.
On a table, workbench, or other flat surface, install vertical racks for attaching the guillotine. Using furniture guides, we secure the cutter frame so that it moves without distortion. Both sides must move in sync. 
The most important part of the cutter is the wire mechanism. The first question is: where to get the material. Nichrome can be purchased in stores selling radio components. But since we are striving for a shareware design, we will look for an alternative.
- Old soldering iron. Models made in the USSR, designed for 36-40 volts, can be found in any home workshop. The heater winding is an excellent donor for a nichrome guillotine. True, the length of the wire is no more than a meter.
- Iron with a classic spiral heater. The wire is thicker, suitable for linear cutting. Shaped cutting acceptable, with low accuracy requirements.
- Spiral heaters from a hair dryer or fan heater. The principle is the same, they are not suitable for precise cutting.
note
Tip: When straightening the spiral, do not pull the wire along the spring. Loops may appear and the thread will break. It is better to unwind the turns as if from a spool of thread. You can put a spiral on a nail or pencil and pull the wire across the turns.
The principle of operation of the frame is shown in the diagram
The wire cutter must be electrically isolated from the frame. Therefore it can be made of metal. It is important to ensure constant tension on the wire. When heated, nichrome expands, adding up to 3% in length. This causes the string to sag.