How to make a knife for cutting foam. Homemade device for cutting foam plastic - buy or make it yourself? Elementary carver

Foam sheets require cutting and adjustment to size and shape. Every master wants to do this quickly and without unnecessary debris, obtaining a smooth edge that eliminates gaps and cold bridges. By and large, foam cutting is carried out in two ways - automatic and manual. Of course, at home, for example, to insulate a roof, you won’t need the entire arsenal, but getting to know each other will never hurt. And maybe it will inspire new approach for repairs.

Tools for cutting foam sheets differ from each other both in functionality and in the complexity of working with them.

Types and classification of hand tools

Review of the best devices for home use

Professional innovative thermal knife

Such products, as in the top photo, were declared by the Patent Department quite recently - only in April 2010, but, despite their “youth,” they very quickly gained popularity in the market. The main obvious advantage of such a cutting tool is that after cutting PSB of any density, there is practically no debris left in the form of granules.

This device is ready for use immediately after removal from the original packaging, and it takes literally 1-2 seconds to heat up. The handle here is made of lingofol (something like wood, but with higher mechanical strength), and the cutter is made of of stainless steel and ceramics. This combination provides a fairly long service life if the breakdown is not done intentionally.

In the top image, there is another option for cutting foam plastic so as not to crumble - this is a homemade unit made from a charger and a string from a piece of nichrome. You can, of course, use unregulated current sources, for example, a battery or a charger for a cordless drill (screwdriver), but here, of course, the design will lose quality.

In addition to the power source and nichrome, you will need some kind of frame - you can even use a small one coffee table. Lovers figure cutting will appreciate such a device.

You can use a hacksaw for metal

It is not always possible to cut polystyrene foam at home with a paint knife or other devices described above due to their absence; for this you can use a hacksaw or a separate blade. Only in this case should you be prepared for the appearance of debris in the form of granules, since PSB consists of them. The teeth, even small ones, will destroy the structure, but if the cutting is done for insulation, then this does not matter from a technological point of view.

Professional laser cutting of PSB

CNC Laser Cutting Machine

Of course, you can use not only a string or a knife to cut foam, but also more modern devices with numerical program control. If you do this on an industrial scale, then CNC machines, which are controlled by a computer, are precisely suitable for such purposes. The advantage of such equipment is that an entire workshop of such units can be controlled by just one person from the operator’s cabin.

It is almost impossible to make such a car by hand.

There are different machines, more precisely, software they are given in different ways and in different volumes. That is, older models (they are still being produced, but not in the same quantity) have integrated software, and you cannot change it in the usual way, and in later developments you can independently add certain programs for making three-dimensional figures with the most bizarre and complex shapes.

Various unique shapes made using this method can be used:

in the metallurgical industry for casting certain alloys;
for tuning in the automotive industry;
in industrial construction for the manufacture of formwork, sleeves for insulating pipelines, as well as for pouring any architectural forms;
theater stage decoration;
advertising logos, inscriptions and so on.

Sleeves for insulation of external and underground pipelines

This tool for cutting foam is the most accurate of all of the above, since computer programs, unlike the human eye, do not produce errors. Therefore you get minimal amount waste thanks to the ideal calculation of the area and volume of the figure in relation to the workpiece. There are special programs that, with a little help from the operator, can develop any configurations and transfer them to the machine.

How to make a foam cutter with your own hands

So, you want to find something to use to cut polystyrene foam, but everything in stores is expensive, and a painting knife is not suitable, since it crumbles the polystyrene foam. Make the cutting device yourself, following the instructions.

Preparation of tools and materials

To make your own cutter, you will need:

ampere-volt-ohmmeter (tester);
curly screwdriver;
round nose pliers;
knife or side cutters;
soldering iron with solder;
electrical tape or heat shrink;
polypropylene tube 15-20cm long and 20-25mm in diameter (it is used for water supply);
a piece of insulated wire made of copper, steel or solid aluminum 20-25cm long and 3mm in diameter;
bolt with nut and washers with a diameter of 3-4mm and a length of 15-20mm;
25mm self-tapping screw (preferably with a press washer);
charger 5V;
USB cord for connecting charging to the cutter;
nichrome length 17cm;
a piece of insulated flexible copper wire 50-60cm.

Theoretical preparation and calculations

Now you need to determine the resistance - the net length will be only 15 cm of nichrome, but you always need to take it 1.5-2 cm more so that you have something to twist. When measuring 15cm, you will get 16.8 Ohms, and the charger is 5V, which means I=V/R=5/16.8=0.29A=290mA, that is, the current that will flow through the cutting wire. Charging at 5V has a rated current of about 550mA, that is, almost twice as much - there is more than enough reserve.

Preparation of polypropylene tube and wire

The PPR tube will serve as a handle - this is convenient, since polypropylene conducts heat very poorly, therefore, it will not heat up when the cutter is turned on.

At the end of this tube, with an indentation of 4-5 mm, make a hole for a self-tapping screw, and 60-100 mm from it another hole in order to populate the connection wiring. Bend a thick insulated wire in the shape of the letter P so that the jumper is 15 cm, and at the ends of the verticals make loops (rings) with pliers to fix the nichrome.

Assembling a homemade device

Now you can start assembling the device:

First of all, use a self-tapping screw with a washer to screw the U-shaped holder to the handle, having previously screwed the nichrome and copper wire onto the screw.
Then insert the bolt into the opposite loop, only so that the washers are on both sides - under the head and under the nut, but do not tighten the nut completely - leave some play for connection.
WITH inside screw nichrome between the nut and the washer, and a copper flexible wire from the outside, under the head, and tighten this homemade terminal.
After these steps, the main part of the cutter is ready, but there is still a connection to the power source and laying out the wiring - do not tighten the nichrome too much, but keep in mind that it will lengthen a little when heated.
Wind the far wire onto the contour of the holder, lowering it in this way to the handle, and then insert both (both the far and the bottom) into the second hole in the polypropylene and pull it through the opposite end of the tube. Now all you have to do is connect the device.

Tin the wires and solder the USB to the ends coming out of the tube - the polarity here does not matter at all, just make sure the soldering is strong, since you will hide it in the tube.
Wrap the connections with electrical tape (if there is heat shrink, this is even better) and push this section inside the PPR.
To fix the wire on the handle, you can simply melt the polypropylene with a soldering iron, plugging this end - after 3-5 minutes everything will cool down.

Foam cutter testing

That's it - now connect the USB to the charger, which, in turn, plug into a 220V outlet - heating occurs in 1-2 seconds. Try cutting off a piece of polystyrene foam - you won’t get the usual crumbs that remain when cutting with a knife or hacksaw.

Second option for making a cutter

For the second model, identical tools will be needed, only the materials for making the frame will change - the handle will be made of wood, and the holder will be made of copper without insulation.

Cut the handle with a jigsaw so that it is comfortable for you, that is, “fits your hand,” and at one of its ends, drill a hole to the diameter of the wire and make a hollow for laying.
Then wrap the copper tip with thread (along the length of the groove), insert it into the hole and groove and fill it with some superglue.
Now you can bend the holder in the way that is convenient for you, that is, in height, which will determine the possibility of cutting depth and length, but with the calculation of the power of the charger (carry out the calculation using the formula given for the first option).
Making a loop on the opposite side of the holder can be tricky, especially if you use steel, so just make the cut with a file. Screw a spring with rings at the ends to the handle using a self-tapping screw (one for fixing and the other for nichrome).

Solder the USB - one end to the spring, and the other directly to the holder, after cleaning its surface. Screw the nichrome first to the far end, and then to the spring - this is better for tensioning.
Connect the USB to the charger and try how to cut foam with such a device.

Now you know how to cut foam plastic and can easily do it with a knife or cutter to prepare slabs for roof insulation. But work for complex instruments, if you don’t have the skills, it’s better to entrust it to professionals.

Foam - light, durable, good thermal insulation material, which is very easy to work with. But it has one unpleasant feature: it is usually made in the form of slabs quite large sizes, which in the process of work have to be cut into smaller pieces. No matter how sharp the knife and saw are, they will not be able to accurately cut the slab, since mechanical action destroys the structure of the foam, causing it to crumble rather than cut. Therefore, you need to use a special foam cutter for cutting.

Foam plastic, like any material, requires cutting, which is why you need a cutter.

The simplest homemade foam cutter

This type of cutter is not difficult to make with your own hands. To do this, just take the thinnest guitar string and 4-5 large batteries for an electric flashlight. Having connected all the batteries in series into a single element, you need to connect a guitar string to its ends and secure it with electrical tape, closing electric arc. Due to the electric current passing through the string, the string will heat up.

Image 1. Diagram of a cutter that allows you to cut flat sheets from a block of foam plastic.

At the point of contact with a string heated to the required temperature, the foam sheet will instantly melt, dividing into two halves, the cut of which will be fused and even. But for normal cutting, the string must be heated to a temperature of at least 120-150º. When working, it will not be difficult to determine whether the string has warmed up enough, since when cutting foam plastic, small stuck pieces will remain on the string. The longer such pieces remain, the lower the temperature of the string. But if they don’t remain on the string at all, then this means that this kind of thermal knife is heated more than necessary.

Such a primitive foam cutter can easily cut 2-3 large layers of material. But with large volumes of work, the batteries run out quickly, so in such cases a cutter powered by electricity is used.

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Options for homemade electric foam cutters

Conventionally, such devices can be divided into groups:

cutter for linear cutting of foam plastic;
cutter for shaped cutting of foam plastic;
cutter with working metal plate.

But despite this division, all cutters have one thing in common.

To make them, you cannot do without a step-down transformer.

Such a transformer must be designed for a power of at least 100 W. Its secondary winding must be designed for a voltage of 15 V and have a winding wire cross-section of at least 1.5 mm.

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Foam Linear Cutting Cutter

Image 2. Diagram of a vertical cutter: 1 – cutting nichrome wire, 2 – weight, 3 – frame, 4 – working surface.

Such devices are mounted from work surface(you can use the surface of a table) with two vertical risers attached to it, two insulators attached to the risers, connected to two contacts connected to a step-down transformer and a nichrome thread stretched between the insulators, as well as a freely hanging load passed through one of the risers (image 1).

This foam cutter works very simply. Passing through a nichrome thread, electricity heats it up, and the suspended weight keeps the thread taut, preventing it from sagging, since when heated it stretches quite strongly. Sometimes, instead of a suspended weight, a spring attached to one of the risers is used to tension the thread.

The heated thread easily cuts the body of the moving foam, turning it into flat sheets, the thickness of which depends only on the distance from the table surface to the tensioned wire. All you need to do is maintain a uniform flow rate of foam across the table surface.

For vertical cutting of layers, a different cutter design is used, in which the cutting wire is stretched vertically (image 2). A frame, preferably welded from metal profile, but one made from wooden blocks (3) is also quite suitable.

The design of the frame provides for the presence of a holder-foot, to which a nichrome wire (1) is suspended using an insulator with a suspended load at the other end (2), passed through a hole drilled in the working surface. Since the nichrome thread will heat up, it is better to make the hole larger and insulate the wooden parts by inserting a metal hollow tube of hollow diameter into it, through the cavity of which the end of the wire with the load is brought out.

This foam cutter will not only easily cut large pieces of foam into blocks required sizes, but will also allow, if necessary, to cut squares, triangles, semicircles and other shaped holes in the material. To do this, just first draw a cutting line along the surface of the foam with a marker.

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Cutter for shaped cutting of foam plastic

If you need to cut sheets of large size or thickness, which due to their size cannot be placed on the desktop, then in such cases use a manual electric cutter, converted from hand jigsaw or a hacksaw, in which the cutting blade is replaced with nichrome wire.

Image 3. Diagram of a manual thermal cutter: 1 – nichrome cutting wire, 2 – screw with nut and washer, 3 – textolite handle 4-5 mm thick, 4 – electrical cord.

Such an electric cutter is not difficult to make with your own hands. At the same time, for the convenience of figured cutting, you can make several working tools of different shapes (image 3). The cutting blade of a jigsaw or hacksaw is removed and brought to the handle (3). electrical wire(4). Despite the fact that the voltage will not be too high, it is still better to insulate the handle, like other metal elements, at least using ordinary electrical tape. Instead of a cutting blade, a nichrome wire bent as required is attached to the supplied electrical cable using screws, nuts and washers (4).

As an option, you can also use a wood burning device or a pulse soldering iron to design such a cutter. Such a cutter will be even more convenient, since the electrical wire is initially provided for in the design of these devices. To turn these devices into an electric cutter for foam plastic, it is enough to replace the heating working tools in them with a piece of thick nichrome wire, giving it the desired shape.

Such hand-held cutters are convenient because with their help you can not only cut sheets of foam plastic, but also cut out all sorts of recesses and cavities in them, remove chamfers, in a word, not just cut foam plastic into pieces, but sculpt real works of art from it.

Polystyrene foam is an excellent insulation material. It is used in household and in industry. If you are going to insulate your apartment with polystyrene foam, then you need to know how to cut it. You can use improvised means or a foam cutting machine.

The structure of a machine for cutting foam plastic with your own hands: 1 - frame, 2 - wire, 3 - guides, 4 - foam plastic, 5 - insulating base, 6 - movable guide, 7 - clamping device, 8 - nichrome thread, 9 - clamp, 10 - power cord, 11 - fasteners.

To cut polystyrene foam, you can use a regular serrated knife. To speed up the cutting process and reduce noise, you need to lubricate the knife blade with machine oil. Cutting foam with a knife requires some effort. This cutting method is the slowest and most unproductive. Cutting speed 1 m in 2 minutes. If the thickness of the material is less than 50 mm, then cutting with a knife is more convenient. To prevent the foam from crumbling, you need to remove the chips with a vacuum cleaner when cutting.

Cutting can be done using a hot string. To do this, you can make your own simple foam cutting machine. You need to hammer two nails into the block, fasten a piece of nichrome wire to them, and then connect a small transformer. Cutting with a hot wire has a high speed: in 10 seconds you can cut 1 m of material. However, this method is harmful to health.

Cold wire slicing involves using the string as a saw with two handles. Gradually the string will heat up from friction, and the cutting speed will increase to 1 m in 50 seconds. You can cut with a hacksaw for metal. This method is more accurate and accurate. The cutting speed is 1 m per 40 seconds.

Cutting using a professional machine is the best, most accurate and fastest. The device for cutting foam plastic includes shaped nozzles. When the amount of work is small, you can use a knife.

But if there is a lot of material, then a hot string or a factory-made device for cutting foam is more suitable.

Hand tool for cutting foam plastic RIRP-1

You can cut out facade decoration elements, toys, models of ships or airplanes from foam plastic.

It is most popular among professional builders. This tool performs thermal cutting of material. With this device you can perform various products, especially if the amount of work is significant. Using RIRP-1, you can cut out façade finishing elements, cut foam plastic for room insulation, and you can also cut various crafts made of foam plastic, toys, models of ships, airplanes. It has high accuracy, speed of work, high strength and reliability.

The time to bring the device into operation mode is 1 minute. It performs thermal cutting using nichrome thread. The diameter of the thread is 0.3 mm - 1 mm. There is an easy-to-use handle in which a nichrome thread is secured using threaded clamps. The nichrome thread used is very durable, will last a very long time and therefore cannot be replaced. RIRP-1 has a filament control unit, which is metal box, in which a single-phase isolation transformer, power regulator, switches, and socket are located. The transformer power is 250 W.

The kit includes:

RIRP-1;
device control unit;
holder on which the nichrome thread is fixed;
instructions for use;
passport.

Specifications:

operating rated voltage 220 V;
nominal frequency 50 Hz;
primary circuit current 2 A;
secondary circuit current 16 A;
rated voltage 600 V;
short circuit strength criterion 4.5 kA;
wire length 2 m;
length cutting tool 1500 mm;
external dimensions 155x220x130 mm;
weight 6 kg;
warranty period 1 year;
price 8000 rub.

Manual device for cutting foam plastic RIRP-2

RIRP-2 is a device for thermal cutting of foam plastic and foam rubber. The RIRP-2 device differs from the RIRP-1 device in that it has a rigid cutting element, which is a blade P - figurative form. The device is made in the form of a knife. With its help, you can adjust various elements when it is necessary to assemble a product that consists of certain segments. The material is cut thermally using a blade that heats up. Soft foam is cut very quickly. The blade dimensions are 170x18x1 mm. The electrodes of a special holder firmly secure the blade. The set includes 2 blades, working and spare. The service life of the blade is 1 year.
Included.

Polystyrene foam is durable, lightweight and very good thermal insulation material. It is very easy to work with it. But there are some nuances in working with this material.

Since it is made in the form of large slabs, it is very often necessary to resort to cutting them. This can be done using and regular knife, but no matter how carefully they try to do it, they will not succeed.

And all because mechanical impact will disrupt the structure of the foam. That is why experts recommend using only a cutter or, as it is also called, a foam cutter for such actions.

You can, of course, buy such a multifunctional tool, but if you make it yourself, you can adapt it to your needs and, of course, save money.

If you plan to work with the cutter in industrial purposes, then it is still better to buy an electrical device that will be designed for large and frequent loads.

How to do it yourself

The need for a cutter can arise at any time if you do some household chores quite often. Perhaps someone has encountered the need to make a part using a special mold for casting epoxy resin.

And to do this, you will need a piece of foam. For example, you can use foam from TV packaging. It is necessary to draw on it using a ruler, compass and ballpoint pen places where holes will need to be made in the future.

This is where the need for an electric cutter comes into play. After all, fulfill given action without ruining the foam sheet, it will be difficult without such a tool. Let's consider one of the options for how to make a device of this type at home.

A homemade cutting device can be various designs. It is on it and the type of cutting that will depend on how exactly the cutter copes with its goals.

Kinds

Before you start making a cutter, you should decide for what purpose you need it, because depending on the purposes, they are divided into several groups:

with metal work plate;
for linear cutting;
for shape cutting.

Stages of creation

Since linear cutting is the most common, let's look at this option in more detail:

Cutting part. To do this you will need nichrome wire, approximately a spiral with a diameter of 0.6 mm. It can be taken from old electric stoves or other heating electrical appliances. The length of such a wire should be 14 cm (its resistance will be 2 ohms).
Transformer application. For everything to be correct, the first step is to calculate the voltage and current for heating the cutting part. This can be done using the formula - Ohm's law I=U/R. Thus, you can determine the power of the power transformer.
Making a cutter. The base can be made of any metal, but its length must be at least 11 cm. Next, an insulator - a PCB plate - must be attached to the end. Now fasten the contact groups along the edges of the plate; they can be removed from the electrical outlet. It is into these contacts that it will be possible to attach spirals of different shapes.
How does the cutter work? After the cutter is plugged in, the wire will heat up and become slightly reddish in color. This is exactly what matters, since a heated cutter will make it possible to easily and quickly cut the foam, which will not peel off.

It is important to know: Having received such a device, in just three minutes it will be possible to cut the required shape from a sheet of foam plastic.

Be sure to follow all safety rules so as not to injure yourself and others. After all, the power of the cutter is enough to damage any part of the body during operation. And connecting to electricity further increases the risk of injury.

Step-by-step production of a thermal cutter

You can make a thermal cutter using a burner or soldering iron and an old jigsaw. Let's consider the manufacture of such a device step by step:

1. Sleeve. Initially, you need to make the main and most difficult thing - the bushing. So, to do this, the plate must be bent and turned. Next, you need to make a hole in the sleeve; the thread will be inserted there in the future.
2. Burner. You need to cut off the wire that leads to the hole, take suitable connectors, and then solder them to the break point.

Note: Such areas must be isolated.

1. After everything is done, you can connect the thermal cutter. Cut an old jigsaw in half. A pre-prepared claw plate must be attached to the upper part with screws. But we attach the bottom to the base using self-tapping screws.
2. Insert the sleeve into the foot. Now with special attention From the hole you need to use a plumb line or a square to mark a point under the hole of the sleeve. Next, drill a hole in the base. The diameter of the hole in the base should be about 5 mm.
3. Thermal cutting machine So, when everything is ready, you need to straighten the nichrome wire. To do this, you should turn on the burner at full power and touch the nichrome with the wires from it. Everything must be done in such a way that there is a distance between the wires equal to the height of the device. If the thread does not heat up, but the burner begins to hum, find a thinner wire. This is necessary because the one you selected does not have enough resistance.

Take note: nichrome should be hot, but should not get red hot. If the string turns red, you need to reduce its heating using the regulator. In the event that the nichrome is red even at a minimum, then a compensator should be left 5-10-15 cm above the spring of nichrome wire. And only after that you can make contact.

Operation of the device. With a pre-installed guide, you need to cut foam dies to a given thickness, or you can make the shape curly.

Application

If you are making repairs or doing wood cutting, or you need to cut a piece of plywood, then an electric cutter will be very useful for you, which can also be used even for cutting thick fabric.

If you think that for all of the above actions you will only need to use a thermal knife, or a hacksaw will suffice, then you are mistaken.

After all, a hacksaw will not make the edges smooth and not torn, as is the case with a cutter.

Somehow I needed to make a mold for casting required part epoxy resin. I found a piece of foam from the TV packaging and cut off the part I needed with a knife flat surface. Using a compass, a ruler and a ballpoint pen, I drew the future places for cutting and then a problem arose: how and with what exactly and on required depth cut it all out? The Internet gave me some ideas. And one of them is to make a special electric cutter. The most important thing in its manufacture is to understand what the supply voltage, current strength, and resistance of the cutting part should be.

Cutting part of a foam cutter

To begin with I found nichrome wire. It was a piece of spiral with a diameter of 0.6 mm from electric heater(also suitable for electric stoves, irons and other heating electrical appliances with a spiral). Then I bent it, giving it the shape of the cutting part I needed. The length of the wire turned out to be about 14 cm. When I measured its resistance, it was about 2 Ohms.

Choosing a transformer for your torch

To select a step-down transformer, it is necessary to calculate what the voltage and current should be to heat the cutting part of the cutter. Ohm's law, familiar to everyone from school, will help here: I=U/R. In this case, it is desirable that the current is not very large. This will help determine the power of the power transformer.

In my stash I found a TPP 268-220-50K transformer.

Transformer for cutter

If you connect in parallel its two secondary windings with terminals 11-12 and 13-14, then the output voltage will be 5 volts with a maximum current of 3.2 amperes. And from our calculation it follows that the cutting part will consume approximately 2.5 amperes. I = U / R = 5 V / 2 Ohm = 2.5 A.

In general terms, it turns out that the shorter the length of the heating element, the lower the voltage on the secondary winding of the transformer should be. Then the current consumption and, accordingly, the power and dimensions of the transformer will be less. Thus, you can select or make the transformer you need for the cutter yourself.

Making a cutter

I made a cutter from scrap materials.

The cutter handle is made from a piece of metal about 11cm long. At one end I attached an insulator (textolite plate). Along the edges of the plate I attached contact groups from the old electrical outlet. It is convenient to attach cutting spirals to these contacts various shapes. Solder fits well on the contacts (they turned out to be copper-plated). I soldered an electric wire (from household appliances) to them and to the secondary winding of the transformer.

Here's what happened in the end:

How does the cutter work?

When plugged in, the cutting spiral heats up to a barely noticeable redness (as if before the reddening begins). I doubted and thought that the thin spiral would bend and change shape when cutting foam. But it turned out that it cuts the foam so easily that it doesn’t move at all.