Plastic products have become an integral part of our lives, so today the topic of recycling plastic at home has acquired particular significance. Recycling of plastics, even if carried out in own home, contributes to the defense environment from huge piles of almost non-degradable plastic waste.

The basis of all plastics is polymers (compounds with high molecular weight and consisting of monomers). The ability to recycle plastics depends on the type of raw material from which the plastic product is made. These days there are many types of plastic, which, however, can be combined into two large groups:

1. Thermoplastic. Approximately 80% of plastic products are made from this material. Includes types: HDPE, LDPE, PET, PP, PS, PVC, etc.
2. Thermosetting plastic. Represented by polyurethane, epoxy, phenolic resins, etc.

It is impossible to recycle type 2 plastics at home, because... Thermoset plastic cannot be re-melted (in some cases, it is crushed in factories and used as a filler). Thermoplastics melt when heated without losing their initial properties and, upon cooling, regain their original shape. That is why “at home” it is possible to process only thermoplastic plastics using special, but “simple” equipment and obtain new useful products and materials from such plastic waste.

The most common recycled materials are PET bottles and other plastic containers.

Useful information! To understand what type of plastic a product is made of, you need to pay attention to the markings on its surface (often on the bottom). It has the shape of a triangle, inside of which there is a number corresponding to the type of polymer. Also under the triangle they put letter designation types of plastic.

What you need for recycling at home

Industrial machines that process plastic are expensive and require large areas. Of course, such units are not suitable for implementing the idea of ​​recycling plastic waste at home. To make new products from waste plastic in a makeshift way, you will need to independently design several special machines.

Following the Precious Plastic project

To recycle plastic “with your own hands,” you will need the following devices (or one of them, depending on your goal):

1. Shredder. Grinds plastic waste to obtain crumbs of a given size, which are then subjected to further processing. The device includes several main components: a grinding part, a feeding hopper, a frame and a power source. The most labor-intensive stage in the manufacture of the device is the production of the grinding element, consisting of a shaft with blades “strung” on it. The loading hopper is made from sheet metal(Waste materials, such as old car parts, can also be used here). The required size of the resulting plastic fraction is set using a mesh installed under the grinding part.
2. Compression device (press). The plastic crumbs loaded into the apparatus are subjected to high pressure and high temperature, the result of the process is the production of new compressed plastic products the most different forms. The main elements of the device: oven, bed, press and electronics.
3. Injector (“injector”). The principle of operation of this device is that, under the influence of high temperature, plastic crumbs are melted into a fluid mass, which is then injected into any form. After the plastic mass cools, new solid objects of small size are obtained.
4. Extruder. The heated plastic mass is forced through the channel of the device, as a result of the process the plastic comes out of the device in the form of threads. Using an extruder you can produce plastic granules.

The blueprints for assembling all of these devices can be downloaded for free from preciousplastic.com. There you can also watch video instructions, which clearly and clearly explain the technologies for creating devices, the necessary materials and the sequence of actions.

The Precious Plastic project is international. Its creator, Dave Hakkens, improved designs for polymer processing devices found on the Internet and, using his knowledge, designed effective devices that make it easy to produce new products from plastic waste. The project helps to the common man create machines that recycle plastic and use them to benefit not only yourself, but also the environment.

A simple mechanism for cutting plastic bottles

The essence of this cutter is that it cuts threads of a certain thickness from the edge of a plastic bottle (along its circumference). The result is achieved thanks to a fixed blade sliding along the plastic product. The process does not require electrical energy; the device consists only of a holder and a cutter itself. From plastic threads obtained by yourself, you can create various items interior, baskets and other objects for which a person has enough imagination.

A few words about safety precautions

Recycling plastic at home does not require advanced safety knowledge. When melting plastic, it is worth arming yourself with fire-resistant gloves (you can use welding gloves) to avoid burns. Also when working with plastic products it is important to know that they should not be burned, because... Some types of plastics, when burned, release toxic compounds into the environment. Of course, it is better if plastic waste is shredded, melted, etc. will take place in a specially designated place, for example in a garage.

Don’t forget about safety during the manufacture of devices for processing plastic raw materials. Here you also need to use individual means protection: special glasses, mask (welding), canvas or leather gloves, etc.

How to melt plastic waste at home

You can melt plastic waste at home using one of the previously described devices (press, injector, extruder). However, their creation requires certain skills and time. You can resort to melting plastic using more primitive methods. For example, to obtain a plastic screw cap, you can build a metal syringe and a solid mold.

Process Description

Polypropylene (marked “PP”) can be used as a raw material. The crushed material is placed into a manufactured syringe and compacted with a metal piston. A syringe filled with plastic is placed in regular oven for about 30 minutes at a temperature of 220-240°C. Then the molten plastic mass is squeezed out of the syringe into the prepared mold, and the material must be kept under pressure for some time. After cooling, the finished product can be removed from the mold.

Video of plastic recycling at home

Craftsmen produce a variety of products from waste plastic. To learn how plastic molding can be done at home to produce a screw wing, see this video:

Melt a few plastic caps You can remove bottles using a hair dryer. The process of molding useful small plastic products is presented in the following video:

Benefit

The main benefit of recycling plastic yourself is that unnecessary and cheap materials are used to create new products that have wide application in everyday life and other areas of our life. By building special equipment, you can organize small business, based on the production and sale of materials for subsequent processing (for example, flex) or ready-to-use items ( plastic dishes, wicker furniture, etc.).

Industrial recycling of plastic involves solving many problems. It is much easier to recycle plastic waste at home. It is only important to set yourself a goal and decide on the direction of processing. And it is possible to design plastic processing devices of any complexity with the help of the “omniscient” Internet.

Extruder is the general name for devices for melting and extruding plastic. Depending on the scope of application, it usually means:

• A hot nozzle on a 3D printer, which actually melts the supplied plastic filament and squeezes it through the nozzle to form the product;
• Device for self-made filament from plastic granules or from recycled old products.

It’s the second device that we’ll look at in more detail.

Reasons for the proliferation of extruders

The main reason for the appearance of this type devices was the excessively high price of the finished plastic thread. So, a couple of years ago, in America and Europe, the average price per 1 kg was about $40, while the retail price for granules of the corresponding types of plastic was $10, and with a wholesale purchase of at least 25 kg it dropped to $5 per 1 kg. Thus, a simple extruder costing $200 could fully pay for itself after producing 6 kg of filament.

The second reason can be called the imperfection of existing desktop 3D printers. The fact is that their work regularly resulted in unsuccessful, deformed products. Therefore, the possibility of recycling them into usable material turned out to be in great demand.

Advantages of filament extruders

The main advantages of making your own plastic thread include:

• Significant reduction in costs for consumables;
• Making thread from any available or intended type of plastic;
• Possibility of combination different types plastic and production of filament with special characteristics;
• The combination of multi-colored plastics allows you to create your own, unique shade of color;
• Recycling of failed and unnecessary products into new ones consumables prevents you from throwing them in the trash.

Disadvantages of plastic filament extruders

Oddly enough, but extruders also have disadvantages:

• The quality of the thread is usually lower than the factory one, here and possible problems respecting the thickness, moisture content of the material, and mixing materials with slightly or significantly different chemical composition and physical properties;
• Some types of plastic emit harmful substances when heated; recycling forces a person to inhale them not only when printing (when you can usually leave the room), but also when making filament ( this process also needs control);
• Recycling of dyed plastics is associated with a lack of information about the toxicity of the dye, as well as the possibility of obtaining a thread of an incomprehensible and unsightly color;
• When disposing of household plastic items (those that were not created on your 3D printer), particles of dirt and dust of unknown composition may be included in the composition.

In fact, all the disadvantages of using extruders come down to the quality of the filament, which will clearly affect the quality of subsequently manufactured products, and to the release of ultrafine particles when heating plastics, the effect of which on the human body has not yet been sufficiently studied, and it is very likely that they can negatively affect health .

I will have to make an extruder for plastic with my own hands for the following reasons. Firstly, I decided to make, and I will need a lot of rather expensive rod for a 3D printer, which is much cheaper to produce yourself using a plastic extruder than to buy a ready-made rod from ABS or PLA plastic for a 3D printer. Secondly, the plastic extruder is one of the components thermoplastic machine (TPA), which I have been dreaming of for a long time. So, again, I'm trying to kill two birds with one stone and save myself a lot of money.

Let's figure out what a plastic extruder consists of and how to make one with your own hands minimal costs. A plastic extruder consists of a tube ending in a removable brass nozzle from which the molten plastic will come out. A so-called auger (a large screw like in a meat grinder) will rotate inside the tube. This auger will push the plastic granules along the tube. Starting somewhere slightly to the middle, the tube will be heated by a special heating element, due to which the plastic inside the tube will melt and reach the nozzle in a fairly fluid state.

The auger is an ordinary large-sized wood drill, purchased at a tool store for 340 rubles. I messed around a little with the diameter and took 22mm, which I later regretted greatly, because it turned out to be quite difficult to find a pipe with the same internal diameter. Therefore, my advice to you is to first find a pipe, then look for a suitable drill (auger) for it.

As can be seen in the very first photo, the tube is divided into two parts, connected by flanges. This is necessary in order to separate the particularly hot part of the tube from the rest of the mechanism. Later, a heat-resistant insulating gasket will be sandwiched between the flanges. In general, heat will still be transferred through the screw, but a collapsible tube will make the extruder more maintainable and will leave space for experimentation (remove one tube and screw on another).

I made the flanges on my own homemade machine CNC machined from 5mm steel sheet. As you can see, my machine chews steel quite well, despite its still flimsy and unfinished Z axis. Two flanges, twisted with bolts, were clamped into the vice. We want all the holes to match!

To ensure the parallelism of the two pieces of pipe, I welded the flanges to the frame to sawing it. We twist two flanges together (in one of them I cut an M6 thread, in the other there are simply through holes), and it is necessary to twist through washers, the thickness of which would then allow a hacksaw blade to fit between these flanges. By the way, do not forget to mark how the flanges should be attached. To do this, I sawed the mark at the end with a file. The flanges are connected correctly if the marks on them match.

The next step was to make a slot in the short part of the pipe. Granulated plastic will flow into this slot through a special funnel and be pushed by a screw further along the pipe towards the nozzle. Note that the right side of the loading slot is approximately aligned with the start of the screw.

One of the most tedious stages of creating a do-it-yourself plastic extruder is making a heating element for the longest part of the extruder - the one in which the plastic will melt. Here I also decided to save money and make a heating element myself from crushed fire bricks, mixed with liquid glass, and nichrome wire, pre-calculated for a given power.

The difficulty is that I don't have carbon dioxide for fast hardening liquid glass. So far I haven’t found where in our city you can refill a carbon dioxide cylinder. It would have been possible, of course, to play around with a carbon dioxide fire extinguisher, but somehow I didn’t want to waste such a responsible device over trifles.

I read a good recipe on the Internet where a little cement (1/5 or even less) is added to the refractory. Then the liquid glass reacts with the cement and hardens in literally a matter of minutes. In the spring I did a good job with fresh cement, but by autumn the cement had already sat and deteriorated, so the liquid glass did not want to harden properly.

By the way, the cover from my auger in which it was sold was very useful as a mold for filling the pipe with refractory. And if I had not forgotten about special measures for curing liquid glass, then my heating element would have turned out to be just the perfect shape. In fact, I forgot to add cement there, so I had to remove this entire mold and manually coat the pipe with a fireproof mixture, and then wrap it all in regular paper to dry. By the way, calcining liquid glass at 150-160 degrees helps speed up the curing process.

Today I unwound this scroll and checked the result. Sticky paper can be easily removed by moistening it with a little water. Overall, it turned out well, but you will have to re-coat it here and there, filling up the holes. The fact is that in some places the refractory solution with liquid glass “floated”, lagging a little behind the extruder pipe. This was easy to detect by pushing my extruder heater along the entire surface with my finger. Where the refractory did not fit tightly to the pipe, it crumbled and fell off.

Of course, the technology for making heaters for extruders with your own hands from refractory bricks and liquid glass will require a little work. This baked ring is especially inspiring - it turned out just great! (It can be clearly seen in this photo right next to the mounting flange) But for now I’m not going to mass-produce heaters for extruders, so let’s put this question aside.

So, the result is a heater with a power of approximately 3 kW. Yes, you can melt aluminum in this, not like plastic. I wonder what kind of extruder performance can be achieved with such a heater?

Now all that remains is to fit the engine and make a normal driver with synchronization for it. Stay tuned…

Written By: .

In the practice of production activities of small enterprises involved in packaging various products, as well as when laying plastic pipes a tool is needed with which it would be possible to reliably connect together materials that have low temperature melting. The class of such materials is large - these are low-density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene, etc. A manual welding extruder can handle all this work.

Design and operating principle

A manual welding extruder is a thermomechanical device that sequentially carries out two processes - heating a low-melting plastic to a viscous state, and then squeezing the mass onto the surface in the joint area. There, HDPE, PVC and other low-melting plastics solidify, forming a strong weld.

For compactness and ease of use, the equipment in question is usually designed in the form of a pistol with a handle (in which the drive electric motor is mounted) and an upper nozzle for heating the working mixture. The welding extruder consists of the following components:

1. Electric motor.
2. Feeder.
3. Extrusion chamber.
4. Crushing screw device.
5. Chambers for melting plastic.
6. Thermal heater.
7. Welding nozzle.
8. Control systems.

To operate, the device is pre-filled with a filler rod made of the material that will be used for welding. The process goes as follows. On the top panel of the extruder there is a receiving sleeve with a hole through which the filler rod is passed. The filling must be such that the free end of the rod falls into the area where it is captured by the auger. When the electric motor is turned on, two processes occur: heating the filler rod with a concentrated stream of hot air, and - after some time, which is determined by the device sensor - feeding the rod into the grinding zone.

There, a rotating auger crushes the plastic rod, turning it into a granular mass. The latter melts when heated, and, moving further, enters the melting zone. In this zone, the granulate is already mechanically and homogeneous. Under the influence of pressure from the screw, it passes into the welding zone, enters the welding nozzle and, in the process of pressing against the surface of the products being welded, is squeezed out into a uniform strip, the width of which depends on the configuration of the nozzle. Since the external temperature is much lower than that created by the thermal heater, the material of the filler rod instantly solidifies, forming a welding seam.

In less compact but more productive extruder models, the filler rod is heated using an external thermal heater, and air is supplied there from a small compressor. There may also be design differences in the method of heating the filler material: sometimes heating is carried out by annular heating elements, coaxially placed in the thermal heater housing.

The manual welding extruder control system performs the following functions:

• Pre-setting the heating temperature, which is determined by the melting temperature of the plastic (as is known, HDPE melts at 120...130ºС, PVC - at 150...220ºС, and polypropylene - at 170...190ºС).
• Turning on the thermal heater;
• Starting the drive of the auger grinder;
• “Cold start” blocking, when the screw can move still heterogeneous filler material;
• Switching off the thermal heater while the auger is still rotating, which eliminates the adhesion of granulate residues in the welding chamber.

Operating rules and selection of a manual welding extruder model

Before use, it is necessary to fulfill a number of conditions usual for plastic: clean the surface of the products to be joined from external contaminants and avoid working with wet material.

The success of the work also depends on the difference in the melting temperatures of the materials being joined, if they have different chemical compositions. For example, HDPE with polypropylene can be welded using the method under consideration, since their melting temperature ranges completely or partially overlap. On the contrary, welding HDPE with PVC, and even more so with polypropylene, is problematic or completely impossible. In such cases, a welding extruder can only be used to join products made from the same materials.

The compactness of the manual welding extruder allows it efficient use even without stopping the operation of the connected devices. Particularly when welding polypropylene pipes It is not necessary to turn off the water supply through them.

A number of mandatory checks are carried out first (especially if the extruder has not been used before):

1. Checking the straightness of the feed of the filler rod in the extruder sleeve: with high roughness of the forming rod, the rod can move not in a straight line, but along a helical line, which will worsen the operating conditions of the screw crushing device and lead to the formation of granulates of non-uniform size.
2. Control check of the effectiveness of the heating temperature of the rod to the state of its viscosity: material from different manufacturers may have a different melting point range.
3. Checking the reliability of pressing the welding nozzle to the surfaces being joined, especially if they have a complex configuration. Many models of manual welding extruders For this purpose, they are equipped with replaceable nozzles.
4. Checking the possibility of melting the materials being joined with heat from a thermal heater, without supplying a filler rod. It is carried out in the absence of accurate information about the material of the products connected in this way.

Choice suitable model manual extruder is produced according to the following parameters:

• By productivity per unit of time;
• For the convenience of managing process parameters;
• According to the thickness of the welded products;
• By equipping the device with replacement devices
• According to the range of rod diameters.

It should be noted that most brands are designed to work with filler material from a specific manufacturer (often the same one that produces extruders).

Theoretically, it is possible to make a household welding extruder with your own hands. To do this, a screw drive is attached to a conventional industrial hair dryer (for example, for grinding feed), and both units are designed in a compact form. Instead of a screw, a more affordable plunger drive is sometimes installed, but this option is unreliable: it all depends on the homogeneity of the material of the original rod. The electric motor for the drive is selected as a commutator type, which better withstands constant changes in torque values.

Welding extruder manufacturers

The most popular devices in this market segment are:

1. From trademark Munsch (Germany). Consumer advantages - ease of fastening of all components (which increases maintainability), undemandingness in the size of the filler material, the presence of a separate heating function (useful when using the extruder outdoors in the cold season), a convenient set of replaceable nozzles, and a perfect control and monitoring system. Plus - traditionally high German quality of manufacturing and assembly.
2. From the Leister brand (Switzerland). The manufacturer produces a wide range of standard sizes of welding extruders: from small ones, with a productivity of up to 0.8...1.2 kg/h, to professional ones, designed for processing up to 6 kg/h. The devices are equipped modern system control and monitoring of the welding progress, ergonomic to use. The quality is also at a high level. There is a special line.

1. From the Dohle brand (Germany). The company is known as a manufacturer construction hair dryers, however in lately actively positions itself as a manufacturer of manual welding extruders. Unlike the above brands, it uses purchased electric motors for drive. It produces the smallest extruder with a productivity of only 0.5 kg/h, which is equipped with a hose and a built-in mini-compressor.
2. From the Stargun brand (Italy). With a small range of models, extruders from this company differ in drive power and are designed for use primarily in professional conditions. The highlight of the devices is the possibility of local illumination of the welding zone.
3. Domestic extruders of the RSE type. They are equipped with a filler material supply drive and include most of the same options that have already been listed above.

Prices for extruders depend on their functionality and performance. On average, the cost of domestic devices ranges from 30,000 to 55,000 rubles, imported ones - from 50,000 rubles. and more.

One of the main technologies for processing plastics and manufacturing various parts and profile products from them is extrusion. It consists of preparing a melt of polymers and then pressing it through molding nozzles - special attachments that give the material a given shape. The main element of a production line using a similar technique is a plastic extruder.

Extruder operating principle

An extruder is an electromechanical device directly intended for the process of molding plastic profile parts of their semi-finished products. General device extruder for plastic:

• Housing with a heating system to the required melting temperature of polymers. As a source of thermal energy And Conventional resistive systems or induction systems can be used, which create high temperatures due to high-frequency Foucault induction currents induced on their body.
• The loading node through which in various ways the raw material enters the housing cavity.
• A working body that creates the necessary pressure to move raw materials from the loading unit to the forming nozzles. Various physical principles are used, so the mechanism can be piston, disk or screw. Screw extruders are the most widely used.
• An extrusion head (otherwise known as a die), which sets the shape of the resulting products.
• A mechanical drive (motor and gear system) that creates and transmits the necessary force to the working element.
• Monitoring and control systems that support the required technological regime.

Loaded in the form of granules, powder or scrap, raw materials are moved into the work area housing, where, under the influence of pressure, friction and externally supplied temperature, it heats up and melts to the state required by the conditions of the technological process.

During movement in the cavity of the housing, the raw materials are thoroughly mixed to a homogeneous homogenized mass.

Under the influence high pressure the melt is forced through mesh filters and forming heads, where it is finally homogenized and given the desired profile.

Then, cooling by natural or forced means, it polymerizes, and as a result, products of the required configuration with specified physical and mechanical properties are obtained.

Video: "How does an extruder work?"

Types of extruders

Modern extrusion plants differ both in the design of the working body and in their intended purpose.

Single and twin screw extruders

Screw (worm) extruders are the most common , since they almost fully meet all the requirements of the technological process. The working body is the extruder screw (Archimedes screw, known to everyone at least from home meat grinders).

The extruder screw blade grabs the raw material in the loading area and moves it sequentially along the entire length of the housing cylinder, through the heating, homogenizing and molding zone. Depending on technological map and the type of source material, screws can be normal or high-speed, cylindrical or conical in shape, tapering towards the exit. One of the main parameters is the ratio of the working diameter of the screw to its length. Augers also differ in the pitch of the turns and their depth.

However, single screw extruders are not always applicable. For example, if a semi-finished powder product is used as a raw material, one screw will not be able to thoroughly mix it during melting and homogenization.

In such cases, twin-screw extruders are used, the screws of which can be in mutual engagement, perform parallel or counter rotational movement, have a straight or conical shape.

As a result, the processes of heating, mixing and homogenization are carried out more thoroughly, and a completely homogeneous and degassed mass arrives at the head.

It should be noted that in some technological processes Extruders are also used with a large number of screws - up to four, and in addition, there are planetary machines, when up to 12 satellites rotate around the central screw.

This may be necessary when working with certain types of plastics, which, when exposed to high temperatures, tend to undergo destruction - loss of physical properties. Thus, their heating in such extruders is carried out due to the friction force and the high pressure created.

Extruder for PVC profile

The production of plastic or composite profiles in most cases is carried out using the extrusion method. To do this, depending on the material and complexity of the product shape, single- or twin-screw machines with corresponding forming heads are used.

The range is very extensive - from thin threads or strips to sheets, large panels and profiles with complex geometries. The now familiar plastic window and door systems are assembled from PVC profiles made in exactly this way.

The addition of special components to the polymer makes it possible to produce complex composites, for example, wood-plastic structures, which are also often used in the manufacture of various building structures.

Extruder for pipe production

In the production of pipe products, very an important condition is the absence of gas bubbles in the homogenized mixture , therefore pipe extruders in mandatory equipped with a degassing system. Typically these are twin-screw installations, in which, among other things, so-called barrier screws are used, which reliably separate the still solid semi-finished product from the completely molten one. This ensures complete homogeneity of the composition, which is very important for the performance of the produced pipe.

Extruders for polyethylene

All polymer films are produced exclusively by extrusion. A blow extruder is used to produce films. The forming unit of the extruder for stretch film can be made in the form of a narrow slit -at the exit a single-layer film of the required thickness and width is obtained.

Some models use round slot dies large diameter- the film is obtained in the form of a sleeve.

Mini film extruders produce polyethylene with a sleeve width of up to 300 mm and a thickness of up to 600 microns. Small size The device allows you to install it even in an ordinary room.

Extrusion lines

In industrial conditions, an extruder is one of the main components of an entire extrusion line, which includes, in addition to it, a number of other installations and mechanisms:

• System for preparing and loading raw materials - sometimes the semi-finished product needs to be pre-dried and calibrated before being fed into the loading hopper.
• Cooling system - installed at the exit of the extruder to speed up the polymerization process of products. There may be various types- air or in the form of cooling baths.
• Mechanisms for drawing finished profiles.
• Marking and laminating systems different principle actions.
• Winding and cutting mechanisms for bringing products into the form required for storage and transportation.

Other mechanisms and technological devices can be used to automate the continuous production process.

Extrusion Line Manufacturers

Extrusion lines are in great demand, and their production is established in many countries in Europe and Asia. Austrian manufacturers are considered the traditional leaders in the production of such equipment, having been producing similar lines since the middle of the last century. European systems always distinguished highest quality, the use of the most modern innovative developments in the field of plastic processing technology.

Recently, products from Chinese manufacturers have been actively supplied to the extrusion line market. Contrary to popular belief, this does not mean its low quality at all - both the reliability and characteristics of the equipment produced generally meet modern requirements. In addition, prices for extruders from China can be significantly lower than in Europe.

Domestic industrialists are also trying to keep up with life. Thus, the extrusion lines of Polyprom Kuznetsk, produced in the Penza region, or the STR Group of Companies from Podolsk and Voskresensk near Moscow are in demand.

The price of plastic extruders varies depending on the country of origin and the individual characteristics of the device.