“Wood” plastic Wood from FiberForce. Lignocarbohydrate wood plastics Wood plastic molds

Hi all!

We have a lot of interesting plastics for sale for decorative 3D printing. Today we will tell you about a new product – Wood from FiberForce. The price of the reel is 0.5 kg. - 3500 rubles.

FiberForce was founded in 2013 in Italy. In addition to ABS and PLA, FiberForce produces several types of special plastics, in particular FiberForce Carbon , which we have been supplying to Russia for quite some time and which has proven itself to be excellent

The undeniable advantage of these plastics is that they do not cause problems during printing, and you immediately receive a finished product that imitates the color of metal or wood.

For example ESUN eAfill or eCopper.With these plastics, you need to be more careful about setting the printing parameters. Incorrect settings may cause the nozzle to become clogged. To “open” the filler, additional processing of the product after printing may sometimes be required.

Wood from FiberForce belongs to the second type of decorative plastics. The plastic is based on regular PLA filled with wood dust.

The rod is rough to the touch, with an interesting matte color of light wood.

The recommended nozzle temperature for printing is about 200 degrees, the table temperature is 50-60 degrees. Although plastic sticks well to printing platforms that are not heated. The main thing is not to forget to turn on the fan to blow the model =)

When printing, the plastic smells very pleasantly of fresh sawdust.

Unlike similar plastic LAYWOO-D3, Fiber Wood does not change its color when printing temperature changes, does not clog the nozzle and is very stable when printing.

LAYWOO-D3 – it was possible to print stably only using large-diameter nozzles (from 0.8).

After 40 minutes of printing we get this nice machine)

The surface of the products looks very beautiful. Due to the matte nature of the material, the layers are almost invisible.

Surprisingly, our jar still smells like wood inside =)

Products made from FiberWood are excellent in sanding and processing.

Results

The most important advantage of FiberWood from Fiber Force is that, unlike other similar materials we have printed with, the risk of nozzle clogging is minimized. And all thanks to the optimal (small) content of wood dust. This decorative plastic gave us no trouble and performed well during printing. Despite the fact that the basis of Fiber Wood is PLA plastic, it is excellent for sanding, cutting and processing. This turned out to be a pleasant plus.

It is great for creating decorative elements, artistic objects or everyday objects with a wood look.

Ecology of consumption. Science and technology: People have learned to transform waste from processing natural materials into products that have superior properties to these materials. From the article you will learn about a completely new material - wood-polymer composite or WPC.

The last 40 years of industrial development can easily be called the “era of combined materials.” Modern equipment and technologies make it possible to combine seemingly incompatible things: wood, concrete, plastic, paper, metal. All of them are mixed, diffused, fused with one goal - to obtain a new product that combines the best properties of several source materials. So, among other new products we saw “liquid wood”.

What is “liquid tree”

In technical terms, it is an extruded wood-polymer composite (WPC). This means that the wood component is preserved using plastic. In this combination, the material takes on the best properties:

1. From wood - compressive strength, impact resistance, elasticity. At the same time, the wood component is practically free - any waste ground into flour is used.
2. From plastic - corrosion resistance, flexibility, precision processing. The polymer envelops wood particles and eliminates the main disadvantage of wood - destructive reactions with water. The polymer in this technology is 90% recycled plastic, i.e. recycled waste.

The technological process is easy to understand, but quite complex to execute. The polymer (plastic) is mixed in a certain proportion with wood flour and heated so that it melts. Then it is molded in an extruder, on rollers or in molds and cooled. At different stages, about 10 different additives are mixed into the mass - plasticizers, catalysts, hardeners and others. All manufacturing details - type of wood and brand of plastic, mixture proportions, additives, temperature conditions, as a rule, constitute a production secret. It is known that all ingredients can be purchased on the open market, and for wood flour they mainly choose bamboo, larch and other durable species of the middle price category.

For the manufacture of WPC, special multi-stage production lines are created. They consist of many devices and controllers. Unfortunately, it will not be possible to assemble such a machine with your own hands in the garage. But you can purchase a ready-made production line.

WPC products

Currently, the product range is incomplete, since the material is relatively new and its properties have not been fully studied. However, several of the most popular positions can be mentioned now.

Terrace board or decking

It accounts for up to 70% of all demanded WPC products today. Most of the supplied production lines are focused on the production of just such boards, since this is the only alternative to wood at the moment. The board consists of a perimeter frame, internal stiffening ribs and has a tongue-and-groove fastening system. Various colors available.

Advantages over traditional materials: WPC boards are distinguished from wood by continuous painting and better physical characteristics (strength, flexibility, processing accuracy). Many types of WPC boards are produced double-sided - with solid wood reliefs and ribbed cutting.

WPC terrace board on video

Facade facing panels or planken

By and large, they can be compared with vinyl siding - the installation principle and panel structure are very similar. But the WPC panel is much thicker and stiffer, and accordingly has more weight and better physical properties.

Advantages over traditional material: a stronger and more durable facade, cavities in the panels and thick walls retain heat better and absorb noise.

Fences, railings, railings, balustrades

Forms of small architecture from “liquid wood” for decorative finishing of the exterior and landscape. They have good load-bearing capacity and are suitable for intensive use (in crowded places).

It was customary to make such products from wood (short-lived and requiring maintenance) or concrete (heavy, cold and not always reliable). Wood-composite forms are made prefabricated, and all parts are designed in advance. All that remains to do on site is to assemble them using a grinder and a screwdriver. Such a fence does not require a strong foundation or constant painting. If a section or structural element is damaged, it can be easily replaced by manufacturing an additional required number of parts.

The general advantage is absolute insensitivity to atmospheric wear (moisture, frost, overheating in the sun), insects, fungi and abrasion.

A common disadvantage is the relatively large fluctuations during heating and cooling. The expansion of WPC terrace boards can be up to 6 mm per 1 m (with gradual heating to +40 ° C).

Prices for facade panels made of “liquid wood”

How to choose a WPC decking board

Any type of “liquid wood” is made from wood flour, the composition of which is not so important. But the composition of the polymer that is added to it can be critical:

1. Polyethylene based polymer. Easier and cheaper to produce. Contains a larger amount of sawdust, due to which it is cheaper than analogues. Susceptible to UV radiation (without additives).
2. PVC based polymer. More resistant to temperature changes, ultraviolet radiation, greater fire safety. 2 times more durable compared to other compounds.

Based on the type of profile, terrace boards are divided into two types:

1. Full-bodied. Withstands significant shock loads. Well suited for places with high traffic - summer cafes and verandas, ship decks, embankments and piers.
2. Hollow. They are light in weight. Suitable for terraces of private houses.

Based on the type of connection, WPC boards are divided into:

1. Suture. They are mounted with a gap of 3–5 mm and provide good water drainage. Fastened with metal or plastic clamps.
2. Seamless. They create a continuous, durable surface due to mutual adhesion. Fastened with self-tapping screws, no clamps required. Suitable for summer areas of cafes - small things, heels, etc. do not get into the gaps.

By type of anti-slip coating or treatment:

1. Treated with brushes (“brushing” from the English brush - brush, brush). Surface created with a metal brush (artificial aging).
2. Polished. The surface is treated with emery cloth.
3. Embossed. As a rule, they are executed in a wood structure. It has a good decorative appearance, but in high-traffic areas the design wears away and this becomes noticeable.
4. Co-extrusion. The top layer is made of a high-strength composition and is structured during the extrusion of the board itself.
5. Co-extrusion with deep embossing (from the English embossing - embossing). Embossing on the top layer imitates valuable wood species.

What to pay attention to, regardless of the type of board you choose:

1. Height of ribs. The strength of the board depends on it.
2. Number of stiffeners. Affects bending strength - the more there are, the higher the strength.
3. Wall thickness. Thin walls (2–3 mm) do not withstand shock loads well.
4. Board width. The wider the board or panel, the faster and easier the installation and the less fastenings will be required.

Video - how to choose WPC decking board

It is absolutely fair to take these tips in relation to facade panels and other WPC products for cladding planes.

The industry provides the average person with the opportunity to make their choice - to use a new natural material that uses natural resources (wood, stone) or to use recycled products. Today people have learned to transform waste from processing natural materials into products that have superior properties to these materials. However, the choice remains with the person - either to dispose of waste by purchasing WPC, or to create more and more of it, giving preference to natural materials. published

Unfortunately, plastic, known to all of us and so widespread throughout the world, contains substances harmful to human health. Moreover, petroleum products are used in its production. However, until recently there was virtually no alternative to this cheap material. Certainly, new construction materials appear constantly. These are plywood, particle boards and fibreboards. There are also new products in the concrete industry, metallurgy, and glass industry. However, in terms of cost and, therefore, availability, they are still far from plastic.

At the beginning of the new millennium, scientists managed to create a fundamentally new structural material, which in the coming decades can almost completely replace the usual plastic. This thermoplastic wood-polymer composite(DPKT or DPK), and in common people - “liquid tree”. Its production uses primary (secondary) raw materials PP, PE or PVC plus wood additives (wood flour, other plant fibers) and auxiliary additives. The effect exceeded all expectations. The newest material is not only environmentally friendly (sulfur content has been reduced by 90%), but also, combining the best properties of wood and plastic, has maintained a relatively low cost.

According to experts, the annual growth of WPC sales in the world is about 20%. So what is this miracle that architects, designers and production workers have been waiting for so long? Let's try to figure it out.

Application and processing

Due to its properties, wood-polymer composite is excellently used in a wide variety of fields. The materials are distinguished by their uniformity and smoothness of surface, plasticity, resistance to atmospheric and biological influences, and their service life even in harsh outdoor conditions reaches 50 years.

All this allows the use of WPC in the production of various architectural and building materials: skirting boards, linings, window sills, profiles, decorative elements, as well as fillers.

Ready-to-use products are made from WPC: laminate, flooring, furniture sheets, furniture, cable boxes, multi-chamber window profiles and even decking - a profile for the manufacture of berths and piers.

The physical and mechanical properties of the wood-polymer composite provide ample opportunities for its processing. Material does not lose its shape and strength, taking in up to 4% moisture. Lightweight, hollow things can be made from it. It is mounted using nails and screws, as well as special latches.

In addition, WPC can be veneered with veneer, laminated with films and sheet plastics, painted with any paints and varnishes, and various decorative effects can be achieved by adding pigments to the composition, etc.

Products obtained from WPC are easy to machine. They are easy to saw, drill, cut, glue, weld to each other, bend (after preheating with a burner), and if flour from soft wood or cellulose-containing waste is added to the material, this also gives the product increased plasticity.

Finally, WPC, in addition to the aesthetics that its appearance gives it, is also pleasant to the sense of smell, having a light woody smell.

Production technology

A number of components are used to make a wood-polymer composite. First of all, this is, of course, crushed wood or cellulose-containing raw materials. That is, it can be not only wood, but also corn, rice, soybeans, straw, paper, sawdust, etc. The second main component of WPC is synthetic binders. These include: polyethylene, PVC propylene, etc. The remaining components are additional additives, the composition of which varies depending on the purpose of the future product. The most common include: dyes, pigments, antioxidants, shockproof modifiers, light and heat stabilizers, fire retardants and antiseptics for protection against fire and rotting, hydrophobic additives for resistance to dampness, foaming agents to reduce the density of WPC.

Wood particle volume in the material can range from 30 to 70%, and their size is from 0.7 to 1.5 mm. Fine fractions are used in the production of finished profiles that do not require additional surface treatment. Medium ones are suitable for painting or finishing with veneer. Rough - for technical purposes.

Volume of synthetic binders x also varies and can range from 2 to 55%. This again depends on the purpose of the future product. As for additional additives, their volume in the material does not exceed 15%.

By the way, not so long ago German developers managed to produce “liquid wood” of ideal quality. Specialists from the Fraunhofer Institute created it from lignin. This material is obtained from wood. DPK called Arboform is a completely non-toxic product. Moreover, if a regular wood-polymer composite can be processed 3-4 times, then this one can be recycled up to 10 times. Why are we doing this? The fact is that in China the WPC industry is growing like nowhere else in the world. And, if in Europe and the USA the created materials undergo a series of tests, then in the Middle Kingdom they do not bother themselves with this and supply the market, including the international one, with a product of not the best quality.

Now about equipment for the production of WPC. Its standard composition includes: a twin-screw extruder, a molding die, a calibration and cooling table, a pulling device, a length cutting device, a width division (if necessary) and a stacker. The entire line is compact, and its control is usually fully automated. Some models also include: a mill (raw material grinder), a raw material autoloader, and a mixer.

Manufacturers of such lines and modules are mainly Chinese companies. The leaders among them are WPC, Zhangjiagang City Boxin Machinery, etc. The quality of the equipment is of a decent level, especially since the main components for them are produced by European machine-building plants.

The task of the technology for manufacturing products from thermoplastic wood-polymer composite materials is fundamentally simple - to combine all the ingredients of the future composite into a homogeneous material and form it into a product of the desired shape. However, its implementation requires a certain set of rather complex technological equipment.

1. General principles of technology.

The starting raw material for the production of WPC is wood flour (or fiber), base resin in the form of a suspension or granules and up to 6-7 types of necessary additives.

There are two fundamentally different schemes for producing extrusion products from thermoplastic WPC:

• two-stage process (compounding + extrusion),
• one-step process (direct extrusion).

In a two-step process, a wood-polymer compound is first made from the original ingredients. Resin and flour are kept in two silos. Flour, dried in a special installation, and resin are sent to a weighing dispenser and enter the mixer, where they are thoroughly mixed while hot with the addition of the necessary additives. The resulting mixture is then formed into small granules (pellets), which are then cooled in a special device (cooler).

Rice. 1. Scheme for obtaining granulated wood-polymer compound

Then, this compound is used for extrusion of profile products, see diagram of the extrusion section, Fig. 2.

Rice. 2. Diagram of the extrusion section

The granulate is fed into the extruder, heated to a plastic state and pressed through a die. The extruded profile is calibrated, sawed across (and, if necessary, lengthwise) and placed on the receiving table.

Wood polymer compound is also used for casting or pressing products from thermoplastic WPC.

In the case of direct extrusion, the ingredients are sent directly to the extruder; see, for example, one of the diagrams for organizing the process of direct WPC extrusion in Fig. 3.

Rice. 3. Scheme of direct extrusion of wood-polymer composites.

In this case, wood flour is fed from the hopper to the drying unit, dried to a moisture content of less than 1% and enters the storage hopper. Then the flour and additives go into the dispenser, and from it into the mixer (mixer). The mixture (compound) prepared in the mixer is fed into the storage tank of the extruder using a transport system. Resin, pigment and lubricant are fed from appropriate containers into the extruder, where they are finally mixed, heated and extruded through a die. Next comes cooling (and, if necessary), calibration of the resulting profile, and then cutting to the required length. This scheme is called direct extrusion.

Currently, both schemes are widely used in industry, although many consider direct extrusion to be more progressive.

There are enterprises abroad that specialize only in the production of granules for WPC, i.e. for sale. For example, at WTL International the capacity of installations of this type is up to 4500-9000 kg/hour.

For an approximate location of the equipment of the extrusion section (line) for direct extrusion of profile parts, see the following diagram.

Depending on the purpose of the project, the production of extruded WPC can be implemented in the form of a compact site in one installation, or in the form of a workshop (a plant with a larger or smaller number of production lines.

Large enterprises may have dozens of extrusion plants.

The limiting temperatures of the extrusion process for different types of base resins are shown in the diagram in Fig. 6.

Fig.6. Limit temperatures of the working mixture (line 228 degrees - ignition temperature of wood)

Note. Most natural and synthetic polymers at temperatures above 100 degrees. C is prone to degradation. This is due to the fact that the energy of individual molecules becomes sufficient to destroy intermolecular bonds. The higher the temperature, the more such molecules become. As a result, the length of the polymer molecular chains is reduced, the polymer is oxidized, and the physical and mechanical properties of the polymer are significantly deteriorated. When extreme temperatures are reached, degradation of polymer molecules occurs on a massive scale. Therefore, during hot compounding and extrusion, it is necessary to carefully control the temperature of the mixture and strive to reduce it and reduce operating time. Degradation of polymers also occurs during the natural aging of the composite when exposed to ultraviolet radiation. Not only plastic is subject to degradation, but also the polymer molecules that make up the structure of the wood component of the composite.

The pressure of the molten mixture in the extruder barrel is usually between 50 and 300 bar. It depends on the composition of the mixture, the design of the extruder, the shape of the extruded profile and the melt flow rate. Modern powerful extruders are designed for operating pressures of up to 700 bar.

The WPC extrusion speed (i.e., the melt flow rate from the die) ranges from 1 to 5 meters per minute.

The main part of this technological process is the extruder. Therefore, below we will look at some types of extruders.

2. Types of extruders

In Russian literature, extruders are often referred to as worm presses. The operating principle of the extruder is the “meat grinder principle”, well known to everyone. A rotating auger (worm) grabs material from the receiving hole, compacts it in the working cylinder and pushes it under pressure into the die. In addition, the final mixing and compaction of the material occurs in the extruder.

The movement of material in the extruder when the screw rotates occurs due to the difference in the coefficients of friction of the material against the screw and the cylinder. As one foreign specialist figuratively put it: “the polymer sticks to the cylinder and slides along the screw.”

The main heat in the working cylinder is released due to compression of the working mixture and the work of significant frictional forces of its particles on the surface of the extruder and on each other. For processing thermoplastics, extruders are equipped with additional devices for heating the working mixture, measuring the temperature and maintaining it (heaters and coolers).

In the plastic industry, the most common, due to their relative simplicity and relatively low price, are single-cylinder (single-screw) extruders, see diagram and photo, fig. 7.

Rice. 7. Standard diagram and appearance of a single-cylinder extruder: 1- hopper; 2- auger; 3-cylinder; 4- cavity for water circulation; 5- heater; 6- grate; 7-forming head. Process phases (I - material supply, II - heating, III - compression)

The main characteristics of the extruder are:

• cylinder diameter, mm
• ratio of the length of the cylinder to its diameter, L/D
• screw rotation speed, rpm
• motor and heater power, kW
• productivity, kg/hour

Note. The nominal performance of an extruder is a relative value. The actual performance of an extruder may differ significantly from the nameplate in a particular technological process, depending on the material being processed, the design of the dies, post-extrusion equipment, etc. Indicators of the efficiency of a particular extrusion process are the ratio of productivity to power consumption, equipment cost, number of personnel, etc.

The following diagram shows the differences in performance of TEM series extruders from the English company NFM Iddon Ltd when producing granules and profiles using different WPC compositions.

The next type is conical screw extruder. Structurally, it is similar to a cylindrical extruder, but the screw and working cavity are made in the shape of a cone. This makes it possible to more energetically capture and push loose material into the working area, compact it and quickly raise the pressure in the die area to the required level.

Note. Cylindrical and conical single screw extruders can be used to produce thermoplastic WPC profiles in a two-stage process, i.e. when processing finished WPC compound.

Extruders with two cylindrical or conical screws are more productive, see fig. 8. In addition, they have significantly better mixing properties. Extruder screws can rotate in one direction or in opposite directions.

Rice. 8. Diagrams of screws of double-cylinder and double-cone extruders: feeding zone, compression zone, ventilation zone, dosing zone

The design of a twin-screw machine is much more complicated and more expensive.

The screws of modern extruders are a complex structure, see Fig. 6.9.a. and rice 6.9.b.

Fig.1.9. Window for real
monitoring the process in the extruder.

Various mechanical, hydraulic and chemical processes occur in the working cavity of the extruder, the observation and precise description of which is difficult. In Fig. Figure 9 shows a special armored glass window for direct observation of the extrusion process (FTI)

Due to their high productivity and good mixing properties, twin-screw machines are used to implement the direct extrusion of thermoplastic WPC. Those. they mix the components and feed the prepared working mixture into the die. In addition, twin screw extruders are often used in a two-stage process as compounders to produce WPC granules.

The screws of twin-screw machines do not necessarily have only helical surfaces. To improve their mixing properties, special mixing sections with other types of surfaces can be made on the screws, which provide a significant change in the direction and nature of the movement of the working mixture, thereby improving its mixing.

Recently, the Japanese company Creative Technology & Extruder Co. Ltd, for the processing of wood-polymer compositions, a combined extruder design was proposed, in which twin-screw and single-screw extruders are combined in one cylinder body.

The basic mechanisms of the phenomena occurring during extrusion of thermoplastic materials are well studied. In general terms, see for example the Appendix "Introduction to Extrusion"

Note. The installation for the production of wood-plastic sheets at Rostkhimmash uses a disk extruder. In some cases, in the production of DPCT, piston extrusion can be used instead of screw extrusion.

There are special methods for mathematical computer modeling of extrusion processes used for calculating and designing extruders and dies, see Fig. 10. and in computer control systems for extruders.

Rice. 10. Computer modeling system for extrusion processes.

Extruders used in the production of WPC must be equipped with an effective degassing device for removing vapors and gases and have wear-resistant working surfaces, for example, a cylinder with deep nitriding and a screw reinforced with molybdenum.

Traditionally, wood flour with a moisture content of less than 1% is used in WPC production technology. However, new modern extruders, designed specifically for the production of WPC, are capable of processing flour with a moisture content of up to 8%, as they are equipped with a powerful degassing system. Some believe that the water vapor generated in the extruder helps to facilitate the extrusion process to some extent, although this is controversial. For example, the Cincinnati Extrusion company indicates that the extruder produced by the company is mod. Fiberex A135 at a flour moisture content of 1-4% will have a productivity of 700-1250 kg/hour, and at 5-8% only 500-700 kg/hour. Thus, a standard extruder, even equipped with a degassing system, is still not a dryer, but is simply capable of more or less effectively removing a small amount of moisture from the working mixture. However, there are exceptions to this situation, for example, the Finnish Conex extruder described below, which can also work on wet materials.

In general, water must be completely removed from the material during extrusion to ensure a dense and durable composite structure. However, if the product is used indoors, it may be more porous and, accordingly, less dense.

One extruder designed specifically for the production of wood-polymer composites is shown in Fig. eleven.

Rice. 11. Extruder model DS 13.27 from Hans Weber Gmbh, Fiberex technology

Extruders used in a two-stage process for preliminary granulation of WPC, instead of a profile die, are equipped with a special granulating head. In the granulating head, the flow of the working mixture leaving the extruder is divided into several streams of small diameter (strands) and cut into short pieces with a knife.

After cooling they turn into granules. The granules are cooled in air or water. The wet granules are dried. Granular WPC is suitable for storage, transportation and further processing into parts at the next stage of the technological process or at another plant by extrusion, injection molding or compression molding.

Previously, extruders had one loading zone. New models of extruders developed for processing composite materials may have two or more loading zones - separately for resin, separately for fillers and additives. In order to better adapt to work on different compositions, extruders and compounders are often made of a collapsible sectional design, which allows you to change the L/D ratio

3. Dies (heads) of extruders

The die (the so-called “extruder head”) is a replaceable extruder tool that gives the melt leaving the working cavity of the extruder the required shape. Structurally, the die is a slot through which the melt is pressed (outflows).

Rice. 12. Die, profile, calibrator.

The final formation of the material structure occurs in the die. It largely determines the accuracy of the cross-section of the profile, the quality of its surface, mechanical properties, etc. The die is the most important component of the dynamic extruder-die system and actually determines the performance of the extruder. Those. with different dies, the same extruder is capable of producing different amounts of profile in kilograms or linear meters (even for the same profile). This depends on the degree of perfection of the rheological and thermotechnical calculation of the system (extrusion speed, extrudate swelling coefficient, viscoelastic deformation, balance of individual extrudate flows, etc.) In the photograph, Fig. 6.13. shows a die (on the left) from which a hot profile emerges (in the center) and is sent to the calibrator (on the right).

To produce products with complex profiles, dies are used that have a relatively high resistance to the movement of the melt. The main task that must be solved inside the die during the extrusion process, and especially for a complex profile part, is equalizing the volumetric velocity of various melt flows in the die over the entire cross-section of the profile. Therefore, the extrusion speed of complex profiles is lower than that of simple ones. This circumstance must be taken into account already at the stage of designing the profile itself, i.e. products (symmetry, thickness, location of ribs, transition radii, etc.).

Fig. 13. Prefabricated two-strand die for the production of window profiles.

The extrusion process allows one extruder to simultaneously produce two or more, usually identical, profiles, which makes it possible to make maximum use of the extruder's performance when producing small profiles. For this purpose, double-strand or multi-strand dies are used. The photograph shows the appearance of a two-strand die, see Fig. 13

The dies are made of strong and wear-resistant steel. The cost of one die can range from several thousand to several tens of thousands of dollars (depending on the size, complexity of the design and accuracy and materials used).

It seems that the technical complexity of powerful modern extruders and dies for them (in terms of accuracy, production technologies and materials used) is approaching the complexity of aircraft engines, and not every machine-building plant can handle this. However, it is quite possible to consider the possibility of organizing the production of domestic extrusion equipment - if you use ready-made components of imported production (working cylinders, screws, gearboxes, etc.). There are companies abroad that specialize in the manufacture of just such products.

4. Dispensers and mixers.

In the production of structural materials, issues of homogeneity (uniformity of structure) and constancy of composition are, as is known, of primary importance. The importance of this for wood-polymer composites does not even require special explanation. Therefore, in WPC technology, much attention is paid to means of dosing, mixing and supplying materials. In the production of WPC, various technological methods and schemes for solving these processes are implemented.

Dosing of materials is carried out in 5 ways:

• Simple volumetric dosing, when the material is poured into a container of a certain size (measuring bucket, barrel or mixer container)
• Simple weighing dosing, when the material is poured into a container located on the scales.
• Continuous volumetric dosing, for example using a dosing screw. Regulation is carried out by changing the feed speed of the device.
• Continuous gravimetric dosing using special electronic devices.
• Combined dosing, when some components are dosed in one way, and others in another.

Volumetric dosing means are cheaper, weight dosing means are more accurate. Continuous dosing means are easier to organize into an automated system.

Mixing the components can be done using cold or hot methods. The hot compound is sent directly to the extruder for profile formation or to the granulator and cooler to produce granules. A special extruder-granulator can act as a hot mixer.

Notes:

1. Granular materials usually have a stable bulk mass and can be dosed fairly accurately using volumetric methods. With powders, and especially with wood flour, the situation is the opposite.
2. Organic liquid and dusty materials are prone to fire and explosion. In our case, this applies especially to wood flour.

Mixing the components can be done in various ways. For this purpose, there are hundreds of different devices, both simple mixers and automatic mixing units, see, for example, paddle-type mixers for cold and hot mixing.

Rice. 14. Computerized mixing and dosing station from Colortonic

In Fig. 14. shows a gravimetric system for automatic dosing and mixing of components, developed specifically for the production of wood-polymer composites. The modular design allows you to create a system for mixing any components in any sequence.

5. Feeders

A feature of wood flour is its very low bulk density and not very good flowability.

Rice. 15. Feeder design diagram

No matter how quickly the extruder screw rotates, it is not always able to capture a sufficient amount (by weight) of the loose mixture. Therefore, forced feeding systems for extruders have been developed for light mixtures and flour. The feeder supplies flour to the extruder loading zone under some pressure and thereby ensures sufficient density of the material. The design diagram of such a feeder is shown in Fig. 15.

Typically, forced feeders are supplied by the manufacturer along with the extruder as a special order for a specific mixture, see for example the direct extrusion process diagram offered by Coperion, Fig. 16.

Rice. 16. Scheme of direct extrusion of WPC with forced feeding, Coperion.

The scheme involves loading individual components of the composite into different zones of the extruder. Appearance of a similar installation from Milacron, see Fig. 1.17.a.

Rice. 17.a. TimberEx TC92 twin-screw conical extruder with a forced-feed system with a capacity of 680 kg/hour.

6. Cooler.

In the simplest cases, the WPC extrusion process can be completed by cooling the profile. For this, a simple water cooler is used, for example, a trough with a shower head. The hot profile falls under jets of water, cools and takes on its final shape and size. The length of the trough is determined from the condition of sufficient cooling of the profile to the glass transition temperature of the resin. This technology is recommended, for example, by Strandex and TechWood. It is used where the requirements for surface quality and profile shape accuracy are not too high (building structures, some decking products, etc.) or where subsequent processing is expected, for example, grinding, veneering, etc.

For products with increased requirements for product dimensional accuracy (prefabricated structures, interior elements, windows, doors, furniture, etc.), it is recommended to use calibration devices (calibrators).

An intermediate position in terms of dimensional accuracy of the resulting products is occupied by the technology of natural air cooling of the profile on a roller table, used, for example, by the German company Pro-Poly-Tec (and it seems to be one of the Korean companies).

7. Calibrators.

The profile emerging from the die has a temperature of up to 200 degrees. When cooled, thermal shrinkage of the material occurs and the profile necessarily changes its size and shape. The calibrator's task is to ensure forced stabilization of the profile during the cooling process.

Calibrators are available in air and water cooling. There are combined water-air calibrators that provide better pressing of the extrudate to the forming surfaces of the calibrator. Vacuum calibrators are considered the most accurate, in which the moving surfaces of the profile being formed are sucked by vacuum to the surfaces of the forming tool.

The Austrian company Technoplast has recently developed a special system for water calibration and cooling of wood-polymer profiles, called Lignum, see fig. 18.

Rice. 18. Lignum calibration system from Technoplast, Austria

In this system, profile calibration occurs using a special attachment to the die, in which water vortex cooling of the profile surface occurs.

8. Pulling device and cutting saw.

When leaving the extruder, the hot composite has low strength and can be easily deformed. Therefore, to facilitate its movement through the calibrator, a pulling device, usually of the track type, is often used.

Rice. 19. Pulling device with cutting saw from Greiner

The profile is delicately captured by the caterpillar tracks and removed from the calibrator at a predetermined, stable speed. In some cases, roller machines can also be used.

To divide the profile into segments of the required length, movable pendulum circular saws are used, which, during the sawing process, move along with the profile and then return to their original position. The sawing device, if necessary, can be equipped with a ripping saw. The pulling device can be made in one machine with a cutting saw, see photo in Fig. 19.

9. Reception table

It can have a different design and degree of mechanization. The simplest gravitational ejector is most often used. For appearance, see, for example, Fig. 20.

Rice. 20. Automated unloading table.

All these devices mounted together, equipped with a common control system, form an extrusion line, see Fig. 21.

Rice. 21. Extrusion line for the production of WPC (receiving table, saw, pulling device, calibrator, extruder)

To move profiles around the enterprise, various carts, conveyors and loaders are used.

10. Finishing work.

In many cases, a profile made from WPC does not require additional processing. But there are many applications in which finishing work is necessary for aesthetic reasons.

11. Packaging

The finished profiles are collected in transport bags and tied with polypropylene or metal tape. Critical parts can be additionally covered, for example, with plastic film or cardboard pads to protect them from damage.

Small profiles may require rigid packaging (cardboard boxes, lathing) to protect them from breakage.

Domestic analogues.

During information research in the field of WPC extrusion, a search for domestic technologies was also carried out. The only line for the production of wood-plastic sheets is offered by the Rostkhimmash plant, website http://ggg13.narod.ru

Technical characteristics of the line:

Type of product - sheet 1000 x 800 mm, thickness 2 - 5 mm

Productivity 125 - 150 kg per hour

Line composition:

• twin screw extruder
• disk extruder
• head and gauge
• vacuum calibration bath
• pulling device
• cutting device, for trimming edges and cutting to length
• automatic storage device

Overall dimensions, mm, no more (dimensions are indicated without the thermal station and a set of control devices - to be specified when arranging the equipment at the customer’s place)

• length, 22500 mm
• width, 6000 mm
• height, 3040 mm

Weight - 30,620 kg

Installed power of electrical equipment is about 200 kW

This installation can be assessed as follows:

• has low productivity
• not suitable for the production of profile parts
• extremely low accuracy (+/- 10% in thickness)
• high specific material consumption and energy consumption

You can cut the parts and sharpen each of them manually, but this technique is very imperfect: it takes a lot of effort, and it is impossible to get two absolutely identical products. Therefore, in this material you will learn how to carry out plastic injection at home.

What we might need

To cast plastic with our own hands, we do not need any special tools or materials. We can make a template model, a kind of matrix, from almost anything - metal, cardboard or wood. But regardless of which option you choose, in any case it must be soaked with a special solution before starting work. This is especially true for wood and paper, because they actively absorb moisture and to prevent this process we need to fill the pores, preferably with liquid wax.

Silicone.

If we settled on this option, then we should buy it with the lowest viscosity - this will contribute to better streamlining of the part. Of course, the results will be more accurate. There are a great many varieties of it on the modern market, and it makes no sense to compare them with each other: we have neither the time nor the opportunity for this. We can only say with confidence that car sealant, preferably red, is ideal for coating. It will make pouring plastic at home much easier.

Deciding on the casting material

To be honest, there are even more molding materials than there are silicone varieties. Among them there is liquid plastic, and ordinary gypsum mixed with PVA glue, and even polyester resin. Substances for cold welding, low-melting metals, and so on are somewhat less popular. But in our case we will be based on some other characteristics of casting substances:

• The duration of their work.
• Viscosity.

Regarding the first point, it indicates the time during which we can manipulate the material that has not yet hardened. Of course, if the production of plastic products takes place in a factory, then two minutes will be more than enough. Well, we, who do this at home, need at least five minutes. And if it so happens that you could not get suitable materials, then they can be replaced with simple epoxy resin. Where to look for it? In car dealerships or in stores for fans of aircraft modeling. In addition, such resin is often found in ordinary hardware stores.

Making a cut shape

This one is ideal for pouring plastic with your own hands, because you can pour unusual types of resins into it. A little trick of this technique is that at the preliminary stage the entire surface of the model needs to be treated with silicone, and then, after the material has completely hardened, the matrix can be cut off. After this, we extract its “insides,” which will be useful to us for further casting. In order for the shape to suit us, we need to apply a three-millimeter layer of sealant, after which we simply wait for the material to harden - this usually takes two hours. It is advisable to apply it with a brush. When applying the first layer, we must try to fill any unevenness or voids with the material so that air bubbles do not form later.

How does the casting process work?

First step.

We take the casting mold and clean it thoroughly - it should be dry and clean. All remnants of material remaining after preliminary procedures must be removed.

Second step.

If the need arises, we can slightly change the color of our composition: to do this, you just need to add one drop of paint to it, but in no case water-based (liquid plastics have a personal dislike for them).

Third step.

There is no need to degas our casting mixture. This can be explained by the fact that plastic molding at home initially provides for a relatively short “life”. At the same time, in order to remove air bubbles from small-sized products, you just need to remove them with your own hands after pouring.

Fourth step.

Mix all the necessary ingredients thoroughly and pour it into the template mold slowly, in a thin stream. This should be done until the mixture fills the entire volume and some more of the casting channel. And soon, when the degassing procedure takes place, the volume of this material will decrease significantly and become what we need.

And the last piece of advice: in order for the quality of the model to be high, the template needs to be cooled gradually, slowly. So, follow all the instructions and everything will work out for you!