Powder paint sprayer: how does the gun work and what types are there?

Powder painting is a productive and effective method of applying weather-resistant protective coatings to various metal surfaces. For this purpose, semi-professional and professional spray systems are used. An indispensable part of each of them is a powder coating gun.

Types of powder coating guns

Powder coating can be done in two ways: by immersion and by spraying the dye.
The first option is a very complex technological process, therefore it is used only in production conditions for painting large objects (corrugated sheets, metal structures and frames). The spraying method is carried out using a gun; this method is available for painting at home. The operating principles of pistols allow them to be divided into several types.

Electrostatic

An electrostatic spray gun allows you to process surfaces regardless of their shape. Promotes the appearance of ultra-thin coatings, usually their thickness reaches only 30-250 microns. This is an economical option that will not be labor-intensive when dealing with maintenance. That’s why this pistol is the leader on the modern market. If necessary, it won’t even take much time to replace the paint.

Tribostatic

The tribostatic gun is distinguished by the absence of a particle generator in the usual sense of the word. The charge is formed due to the fact that the particles of the paint and varnish material rub against each other. The difficulty of obtaining a sufficient charge with paint is the main difficulty faced by owners of tribostatic devices when painting. A precise adjustment of the primary paint is required.

Fluidized

This type of sprayer is designed to apply paint layer by layer. Therefore, it is easy to gain sufficient thickness. Usually it is at the level of 250 microns. Thanks to the use of technology, it is easier for the master to monitor what the thickness of the spray remains at each specific moment in time, using a sprayer.

Preparatory work, operation of the coating and sprayer in this case are really cheap and do not require additional expenses. But this option also has disadvantages, including:

• the requirement for the surface to be treated to have a simple shape on which the powder spraying process is organized;
• the need in any case to pre-heat the part with your own hands and then dry it;
• increased paint consumption during surface treatment;
• This technology also requires the use of a metal that is resistant to high temperatures.

On video: the best sprayer for powder painting at home.

This is interesting: What and how can you make a paint brush?

How to make a powder spray gun

On sale, as described earlier, there are several types of ready-made spray guns that can apply powder paint. But their cost is rather high; for this reason, for a one-time coating of a surface with a composition, the expense is often impractical.

Moreover, it is possible to make a pistol yourself; it won’t take much time to get rare parts. You can do it in ten minutes. The device is convenient, inexpensive and easy to use.

So, according to the drawing, you should perform the following steps:

1. You will need a regular 1.5 liter plastic bottle, you need to wash it and dry it well.
2. One third of the bottle is filled with coloring powder; the bottle must be closed with a metal stopper.
3. Small holes are made in the metal plug; they try to make the maximum number of holes so that the composition is sprayed better.
4. Excess particles that appeared after creating holes on the surface are removed from the cork.
5. A positive wire taken from a high-voltage source is connected to the made cover.

Accordingly, a converter will be required to be able to withstand a voltage of 25,000 volts with a constant flow. Similar options are found in electric shockers, lighters for gas stoves, boilers and speakers. Their operation can be provided by batteries or accumulators, converting 3-6 volts into the required 25 kV.

Using high voltage devices is dangerous and requires caution. It is advisable that the assembly of this device be carried out by a specialist.

It is possible to make a gun yourself, it won’t take much time and you won’t need to get rare parts.

Spray guns

Powder dye is a solid mass that consists of many small particles. It does not need to be kneaded and therefore, as mentioned above, this dye has become very popular.

At first, this paint was made for the oil industry as a coating like varnish. It was needed to make enterprises safer and free of fire hazards.

But gradually it flowed into everyday life and is now used for painting cars and other things.

Video:

There are two ways to paint objects with dry paint - spraying or dipping.

The first method is accessible to almost everyone, the second is more problematic, since it is needed for very large objects and products - up to several meters in length and width.

After painting, the item should be dried in the oven so that the paint adheres better. This method requires large dimensions of the room for painting; doing it yourself is problematic.

But to paint anything at home, you need to use a paint gun, which can be easily purchased at a hardware store.

There are two types of such guns - tribostatic and electrostatic. The first type is simpler - the paint simply comes out of its container to be sprayed onto the surface.

However, this device can only spray epoxy paint. If you use other types of dry dyes, then you need to mix them with various solvents and mixtures.

The second type of pistols is electrostatic. This device has a more complex design than the first one.

The principle of its operation is the creation of an electrostatic field in which a low-frequency signal penetrates the electrode and forms a field, after which paint particles are sprayed. The electrostatic gun is suitable for almost all types of dry paint.

Depending on the above characteristics, you need to make your choice, but you must remember that such equipment is not cheap.

If you don’t plan to do any grandiose coatings with dry paint yourself, then you can purchase a tribostatic gun.

It contains paint in a 0.5 liter container; you can change it if necessary. Although its design is quite simple, it can serve you for a long time and paints small and medium-sized objects well.

Video:

True, one of its disadvantages is that the parts that make it up quickly become unusable, but they can be replaced.

If you need to paint large volumes, then electrostatic guns are suitable - they paint even better than the first ones, the layer is more even, but they paint medium and small products with a complex design worse.

Application chambers and recovery systems

The designs of application chambers and recovery systems are so diverse that it is very difficult to give recommendations on their selection, except for the most general ones, without specific reference to the planned production.

Application chambers made of dielectric materials with a special electrically conductive coating provide a more complete and uniform deposition of powder paint onto the product, however, if the design is incorrect and does not take into account all the factors of working with explosive dust-air mixtures, they can represent a source of increased danger due to the accumulation of significant charges of static electricity and therefore their cannot be recommended for self-production.

Sheet metal chambers are the most widely used, both for small installations with hand guns and for high-performance conveyor lines.

The presence in the chamber of uneven surfaces, horizontal ledges, cracks, unrounded corners and other places that make cleaning difficult at the end of work and during transitions can affect the quality of the resulting coating in the form of inclusions and craters.

It is necessary to ensure a vacuum in the chamber relative to the room and the air speed in open openings (for supply and exit of products, for access to the product of paint spray guns) should be in the range from 0.25 m/s for working on modern fine-dispersed PCs to 0 .6-0.8 m/s for materials with an average particle size of more than 45-50 microns. The rate of air suction into the chamber should prevent powder paint from entering the room in which it is located. It is always better to have a reserve of fan performance and pressure and reduce the speed of air suction by the damper, although this increases energy consumption.

The recovery system must capture the maximum possible amount of PC for return to the process (feeder) or for other disposal and ensure the necessary environmental characteristics of the installation.

Summarizing the existing experience in operating PC application installations, we can recommend a two-stage PC collection system using a centrifugal-type dust separator (for example, a cyclone) in the first stage, and a filter in the second. In this case, it is possible to return the PC from the first stage of collection to the application process, and from the second stage of collection, where the PC may be contaminated with filter fibers or other powder paint (due to the difficulty of cleaning when moving from one material to another), direct the unloaded material to disposal or disposal. This allows you to use up to 97-98% of the original PC loaded into the feeder. Such a capture system makes it possible to reduce the PC concentration in the exhaust air below the maximum permissible concentration for the workplace, which is usually 5-8 mg/m3.

However, it cannot be recommended to discharge exhaust, purified air into the room where the installation is located, as many companies that manufacture application equipment do, since this in some cases leads to general contamination of the room, the accumulation of flammable explosive dust on the surfaces of the equipment, staircases, platforms, air ducts, pipelines, etc., which ultimately, in the absence of regular wet cleaning of the premises, can lead not only to defective coatings (dirt, specks of a different color) when this dust is sucked into the application chamber, but also to an accident due to accidental not related to the application process, sunbathing, for example due to a violation of TB.

As practice has shown, many filter partitions (in particular, non-woven materials based on lavsan), while coping well with cleaning the air from PC dust, as they age, they themselves begin to release fibers into the air emitted into the room. Then, with the air taken by the application chamber, they enter the recovery system and feeder, disrupt the operation of the feeder and sprayer, and settle together with the PC on the product, leading to the appearance of defects and defects.

Keeping the premises and equipment clean, weekly wet cleaning using industrial vacuum cleaners allows you to avoid defects on the coating in the form of mechanical and other foreign inclusions that get into the PC or onto the product both at the application stage and throughout the entire process of obtaining the coating. Therefore, if defects occur in the form of one or another type of contamination, it is necessary to review the entire chain of operations that the product goes through before blaming the supplier for contamination of the PC.

Types of dry paints

Dry paints contain various pigments, resins, fillers and other additives.

Powdered dyes are now used in many areas, and their number is growing as the industry rapidly develops. Powder paints can be divided into two groups - thermosetting and thermoplastic.

The former includes a thermosetting film former. During painting, a uniform layer is formed during chemical reactions and melting of its particles.

This group includes epoxy paint, polyurethane and polyester, which contains resin.

Polyester dyes are good for painting items in the yard of a house, for example, for a playground, since weather conditions do not affect it in any way, the paint holds well.

Epoxy enamels are also very resistant, do not dissolve, but can turn yellow if the painted product is overheated.

Due to excess ultraviolet radiation, the topmost layer of such paint is destroyed. But polyester-epoxy paint does not turn yellow from excess heat and light, although they have a similar composition and can withstand higher degrees.

Acrylate dry paint is needed for objects that are actively used. It can withstand alkalis and high temperatures, and is also durable and retains its brightness for a long time.

Video:

Polyurethane powder dye has a shine. It is best used on items that are subject to wear and tear and are constantly subject to friction to protect and preserve them.

And the dye also has an attractive feature - it can be used to create the effect of compressed silk, which looks good in the interior.

This paint is waterproof and does not react to solvents, liquid fuels and various mineral oils.

Thermoplastic dyes are more natural, but less durable. Most often they are used for installation inside and outside the house, as well as for painting various products and objects to protect them from damage and corrosion.

This paint is sometimes used to paint interior items and even parts of washing machines and dishwashers to prevent the action of detergent.

Powder coating principles

Powder painting is fundamentally different from traditional liquid painting. Here, the process of applying the dye does not occur in the form of a viscous substance (which is ejected from the spray gun nozzle under the influence of mechanical energy), but in the form of tiny particles of dry dye.

The adhesion of particles to the surface being painted occurs due to their electrification, as a result of which they acquire a charge different from that possessed by the surface. Then everything happens in accordance with the well-known Coulomb law on the attraction of unlike electric charges. The strength of electrification determines the strength of adhesion.

The acquisition of a positive or negative charge by initially electrically neutral particles can occur in two ways:

Electrostatic, when a powder particle is charged from an external source. Therefore, powder guns that implement this principle are called electrostatic;

From the kinetic energy of friction between adjacent particles that fly out of the nozzle of a paint gun at high speed. Since in this case the tribostatic effect is used, the pistols received the same name.

Regardless of the energy source that charges the powder, the uniformity of the charge level leads to the fact that the sedimentation of dye particles occurs much more evenly, and is not associated with compressor pressure drops, the force of pressing the trigger and other factors.

In addition, dry powder paint is more environmentally friendly because it does not contain toxic organic solvents. However, it is recommended to use a respirator when painting.

There are also limitations in the use of powder paints. For example, in order to increase the surface activity of the surface being painted, it is recommended to heat it to 150...200°C. Otherwise, the adhesion force of unlike charges decreases, which will affect the durability.

Powder tribostatic guns

The general principle of operation is to impart an electrical charge to the paint particles. The easiest way to do this is by friction.

The operation of a tribostatic powder coating gun is as follows. The tank is filled with powder dye (the source material must have a certain humidity, which prevents adjacent particles of dry paint from sticking together, which will lead to excessive energy consumption). The reservoir is attached to the body of the gun, while a hose is attached to the end to transport air flow from the air intake.

The length of the hose is determined by the power of the compressor, and for household versions of guns it usually does not exceed 3 meters. The gun body is pre-grounded. When turned on, air particles are mixed with powdered dye. A powerful turbulent flow of the mixture is created, in which intense friction of adjacent powder particles occurs. This flow is channeled through the outlet of the nozzle and discharged onto the surface to be painted.

The inner surface of the grounded body is deliberately provided with macro-roughness, so the polymer particles of the dye experience significant frictional forces, as a result of which their charge further increases.

Tribostatic guns are structurally simple and have a lower price, but their performance is associated with some external limitations:

1. When operating at low temperatures, the effectiveness of the tribostatic method decreases. The reasons are increased air humidity and clumping of powder particles.
2. Not all powdered paint mixtures can be effectively electrified by friction. For example, polar solvents have to be added to all compositions, except epoxy compositions, and they increase the density of the powder and increase the required compressor power.
3. The performance of the tool is determined by the size of the tank (standard equipment includes a tank with a capacity of 0.5 l). Therefore, the method is suitable for painting relatively small surfaces.
4. The intensity of the charge depends on the degree of filling of the tank. With a small amount of powder, friction weakens, which can lead either to a decrease in the thickness of the paint layer or to a deterioration in its adhesion to the surface being painted.

The essence of the technique

Powder paint is sprayed onto a clean metal surface. During spraying, the particles receive an electrical charge from an external source or are electrified by friction. Thanks to the electric field, the particles are directed towards the metal, which has the opposite charge. Particles that do not settle are collected in the spray booth and can be used for repainting. The painted part is then sent to a polymerization chamber.

Scheme for applying a conversion sublayer of powder painting

By forming a surface layer of powder paint, a monolithic, high-quality structure is created that protects the base material. The coating is formed by heating the painted layer to a melting state. Further surface finishing involves hardening (for thermosetting materials) or cooling (for thermally plastic materials). The result of the treatment is the formation of a hard surface film.

Read more about how to do powder coating yourself.

Car powder painting technology

Before application, the metal surface of the part is thoroughly cleaned and degreased. When passing through channels in a powder painting sprayer, paint particles are electrified from an external source or receive a charge through friction. Then, due to the formation of an electric field, they fall and are fixed on the metal, which has the opposite charge. Those particles of powder material that are not fixed on the surface are taken into the spray painting chamber and can be reused for painting parts. Next, the processed body part is moved using special stands into a chamber for polymerization and drying. The result is a reliable layer of paintwork, which in terms of characteristics is significantly superior to simple enamels.

The polymerization process itself occurs by placing a stand with a fixed part in a special chamber, where the material is heated to the melting stage. After this, in the case of using thermosetting materials, a slow hardening process occurs, but if thermally plastic compositions are used, then the cooling process of the part is ensured.

Ultimately, a dense film is created on the treated surface, which not only decorates the part externally, but also protects it well from corrosion and is quite resistant to mechanical damage.

How the tool works

The essence of the operation of this equipment can be divided into three main steps:

1. Paint is poured into the spray bottle and equipment is connected to electrify the material particles. They receive a charge when passing through the channels of the atomizer.
2. The workpiece is grounded.
3. Charged paint particles are applied to a metal surface.

In addition to the spray gun itself for powder painting, the processing line includes a certain set of components, the list of which is below.

• container for powder paint.
• stands for fastening products, with fastening clamps and hooks.
• automatic lines for moving stands into the chamber for subsequent processing.
• spray chamber.
• cyclone to charge the paint particles.
• filters.
• unloading chamber.
• chamber for heating and polymerization of powder material.
• ventilation.
• lighting.
• compressor.

If we talk about the diagram of the powder paint gun itself, it is as follows:

1. Air supply channel.
2. Paint supply line.
3. Charging surfaces.
4. Grounding.
5. Powder mixture.
6. A head for spraying the finished composition onto a metal surface.

Types of paint sprayers

Depending on the technology that underlies such a tool, several main types of equipment can be distinguished.

1. Electrostatic gun for powder painting. Using this device, you can apply a very thin layer of material 30-250 microns. It handles well not only smooth surfaces, but also relief shapes of the part. Characterized by economical paint consumption and ease of maintenance. But the main disadvantage is the high price. When processing, the surface does not need to be preheated. Electric generators are used to charge the material particles.
2. Tribostatic pistol. Also often used when working with powder paint. In this technology, the process of electrification of paint particles occurs due to their friction against each other. There are no special generators connected here for charging. Disadvantages include problems with obtaining the required amount of particle charge and dependence on humidity in the workroom itself. Such factors can affect poor deposition of paint particles on a metal part, which will lead to increased material consumption and a decrease in the quality of the coating itself.
3. Fluidized. This technology is that the part is preheated, after which the powder is applied with a spray gun, then it melts, a film is formed and the drying process begins. This way you can apply several layers of paint. This approach is rarely used, and I restore mostly flat surfaces.

Important point! When working with powder paints, use personal protective equipment such as gloves, goggles, a respirator, and long sleeves. This is due to the fact that this material contains harmful substances, including: lead, cadmium, triglycylisocyanurate hardener, allergens, epoxy resins.

Powder gun design

A spray gun for powder coating, of course, differs from its industrial counterpart in power, small dimensions, paint hopper and other parameters. At the same time, it makes it possible to perform a very diverse range of paint applications on many materials.

A standard powder gun consists of the following elements:

• converter,
• powder paint bin,
• buttons to turn on,
• adjustment knobs,
• union,
• indicator,
• power unit,
• wires for grounding,
• lever

There are two main methods of applying powder paint using a powder gun - electrostatic and tribostatic.

The first method is considered the most effective and is suitable for epoxy, polyurethane and polyester powder materials.

The second method is less productive and allows you to use only epoxy paint; other powder materials can only be used after mixing with special additives.

This is interesting: How does the use of a pressure gauge affect the operation of the spray gun?

Feeders

As noted above, in installations with electro- or tribostatic spray guns, a mixture of PC and air (aerial suspension) is used. In typical industrial application systems, an air suspension is obtained in feeders, where powder paint is either poured onto a porous partition through which pressurized air is supplied, transferring the entire PC into a suspended (so-called “fluidized bed”) state, or compressed air is supplied to the powder paint by a special device , creating a local “fluidized bed” area from which the PC air suspension is sucked in by an air pump - ejector, diluted to a lower concentration with additional air and transported to spray guns (in a number of high-capacity installations, especially as part of painting conveyor lines, several feeders operate from one pistols).

Due to the general trend of reducing the specific consumption of PC for painting and, accordingly, reducing the thickness of the final coating, leading companies have switched to the production of PC with a reduced average particle size, but the transfer of such powders into a suspended state is complicated. Therefore, many companies supply feeders with vibrators that facilitate the creation of a “fluidized bed”.

Guns for laboratory or small PC applications have a built-in feeder along with a small container for powder paint. On them, as a rule, it is more difficult to obtain a homogeneous air suspension and, accordingly, a uniform torch, especially when turning it on and off: a release of aggregates is often observed. Therefore, it is undesirable for the barrel of such a pistol to be directed at the product when turning it on and off. You should also remember the limited capacity of the funnel, which usually holds no more than 200 g of powder paint. At the same time, cleaning such a gun is much easier than cleaning a spray gun with a separate feeder.

Electrostatic spraying

Powder coating technology by electrostatic spraying.

Rice. 1 – Corona charging technology

Its popularity is due to the following factors: high charging efficiency of almost all powder paints, high productivity when powder coating large surfaces, relatively low sensitivity to ambient humidity, suitable for applying various powder coatings with special effects (metallics, shagreen, mauara, etc. ).

Along with its advantages, electrostatic spraying has a number of disadvantages, which are caused by the strong electric field between the spray gun and the part, which can make it difficult to apply powder coating in corners and in deep recesses. In addition, incorrect selection of electrostatic parameters of the sprayer and the distance from the sprayer to the part can cause back ionization and degrade the quality of the polymer powder coating.

Equipment for powder coating - an electrostatic spray gun is included in the standard Alfa Color powder coating complex.

Rice. 2 – Faraday cage effect

The Faraday cage effect is the result of electrostatic and aerodynamic forces.

The figure shows that when powder coating areas affected by the Faraday cage effect, the electric field generated by the spray gun is at its highest intensity at the edges of the recess. The power lines always go to the closest grounded point and are more likely to concentrate along the edges of the recess and protruding areas, rather than penetrating further inside.

The Faraday cage effect is observed in cases where powder paint is applied to metal products of complex configuration, where an external electric field does not penetrate, so applying an even coating to the parts is difficult and in some cases even impossible.

Rice. 3 – Reverse ionization

Back ionization is caused by excessive free ion current from the charging electrodes of the atomizer. When free ions hit the powder-coated surface of a part, they add their charge to the charge accumulated in the powder layer. But too much charge accumulates on the surface of the part. At some points, the amount of charge is exceeded so much that micro sparks jump through the powder, forming craters on the surface, which leads to a deterioration in the quality of the coating and a violation of its functional properties. Reverse ionization also contributes to the formation of orange peel, reducing the efficiency of sprayers and limiting the thickness of the resulting coatings.

To reduce the Faraday cage effect and reverse ionization, special equipment has been developed that reduces the number of ions in ionized air when charged powder particles are attracted to the surface. Free negative ions are diverted away due to the grounding of the atomizer itself, which significantly reduces the occurrence of the above-mentioned negative effects. By increasing the distance between the spray gun and the surface of the part, you can reduce the spray gun current and slow down the reverse ionization process.

Spray guns

Two methods of charging PC particles are used: with a corona electrode under high voltage, and using the “triboeffect”, i.e. the effect of acquiring opposite charges by contacting bodies made of different materials.

The first method uses a high (20-100 thousand V) constant voltage supply to the discharge electrode from a special high-voltage generator located inside or outside the gun, depending on the design. In the case of manual pistols, preference should be given to generators built into the pistol, since this ensures higher worker safety (safe voltage supply to the pistol from 9 to 30 V, depending on the model) and eliminates the need to connect a high-voltage cable to the pistol, which is more rigid and heavy compared to low voltage, which causes increased fatigue of the worker.

In the second method of loading particles, the barrel and other parts of the gun that the powder paint comes into contact with are made of a special material (usually fluoroplastic - for epoxy-containing PCs).

The most significant difference in the effectiveness of these methods of PC charging and the choice between them when painting certain parts is the presence of a strong electric field in the first charging method, forcing PC particles to move along its field lines, or the almost complete absence of such a field during tribocharging. Therefore, forced charging of the PC from the corona electrode of the spray gun causes a significant difference in the amount of PC deposited on the surface of the product in places of protrusions and flat surfaces. The location of the products relative to the pistols, the distance and direction of the barrel of the latter, and the barrel attachments used also play a role. When parts are hung closely, for example on a conveyor, they can mutually shield each other.

In general, parts of complex shapes when painted with sprayers with a corona electrode create more problems than with tribocharging, especially when using automatic manipulators. There are frequent cases of unpainted recesses, internal corners, grooves that require additional manual touch-up, the use of directed torches with high speed air jets that “blow” PC aerosol into such places, reducing the voltage on the corona electrode, which also reduces productivity and increases the number of PCs that pass by products.

On conveyor lines, with a low frequency of movement of the sprayers on the traverse compared to the speed of movement of the product on the conveyor, in combination with a narrow or uneven torch, it is possible to obtain a coating of different thicknesses in the form of alternating stripes (waves) - traces of the relative movement of the torch and the product. The same defect can occur when applying PC manually due to insufficient qualifications of the worker or haste.

When painting parts with complex shapes, it is easier to use a PC sprayer with tribo-charging. However, it should be taken into account that not all powder paints can be charged by friction, and special ones are more expensive. Additives are also commercially available to enable the application of conventional PCs using tribo-sprays. As a rule, the productivity of the application process with spray guns with a tribocharge is reduced, and the percentage of PC deposition on the product is lower than when using spray guns with a corona electrode. It is also inevitable that the effect of tribocharging will gradually decrease with a decrease in the total charging voltage of the PC, and an increase in the proportion of uncharged powder and, accordingly, not deposited on the part, as the parts of the spray gun wear out, which requires their periodic replacement with new ones. Therefore, the low initial price of installations with tribocharging does not guarantee a reduction in the cost of painting a unit surface of a product with powder paint compared to the use of more expensive installations with high-voltage generators.

Tribostatic spray gun

A tribostatic powder gun or spray gun works on the principle of multiple collisions and friction of powder paint particles, as a result of which they are charged. This process occurs in a special unit of the gun, where the particles actively interact with each other.

Since the use of current is eliminated during charging, there is no electric field, which means there is no reverse ionization effect.

This gives the following advantage: powder paint freely penetrates into all hard-to-reach places of the relief and porous surface and is evenly distributed, which guarantees the quality of spraying. It also becomes possible to paint the surface multiple times, achieving a layer of the desired thickness.

Among the disadvantages of the tribostatic painting method, one should note a limited selection of paints, mandatory sandblasting of metals before painting, and low productivity. And the tribostatic powder gun itself has proven itself to be a very capricious device in operation.

Equipment

According to the operating principles, equipment is usually divided into several types:

1. Electrostatic. Allows you to obtain ultra-thin coatings - in the range of 30-250 microns. Also, using electrostatic devices, you can process parts of any shape. The equipment is not labor-intensive and economical to maintain. If desired, changing the paint will not take much time. It is also worth noting that there is no need to preheat the products. The main disadvantage of electrostatic devices is their high cost.
2. Tribostatic. Systems of this type operate without a particle generator. During the spraying process, a charge is formed due to the friction of particles of paint and varnish material against each other. A significant disadvantage of tribostatic devices is the difficulty in providing sufficient charge, which is why adjustment of the primary paint is often necessary. It should also be noted that the quality of charging depends on the level of humidity, the rapid decrease in charge during operation and the not very active deposition of powder.
3. Fluidized. Equipment of this type is designed for layer-by-layer application of paint. This approach ensures sufficient layer thickness (approximately 250 microns). Moreover, the technology allows you to largely control the thickness of the spraying. In addition, preparatory work and further operation of the coating are inexpensive. The disadvantages of fluidized equipment include: increased paint consumption, the requirement for preheating and drying of the part, and the requirement for a simple shape of the surface to be treated. In addition, the metal must be resistant to high temperatures.

Advice! Powder paints, although not classified as substances that require increased safety measures, still contain some dangerous substances. These include lead, cadmium, triglycylisocyanurate hardener, allergens, epoxy resins. Therefore, before working with powder formulations, you should protect your respiratory system.

Operating principle and required equipment

The powder gun is used according to the following scheme, regardless of its dimensions:

1. Charged particles of coloring material are placed inside the spray bottle.
2. An accumulation of charged particles of colored powder is created near the surface being treated.
3. The product being painted is grounded and dye particles are attracted to it.

The complete scheme for implementing a working cycle using a spray gun also includes the following components:

• Chambers where parts are loaded. Those who use tribostatic equipment are also familiar with this part.
• Rotating devices that are needed when hanging products.
• The chamber where the deposition process will take place.
• A cyclone within which particles of paint material are formed and charged.
• The layer responsible for filtering.
• Unloading chamber.
• Feed lines for parts. They usually move at low speed.
• The chamber where the paint and varnish powder coating is polymerized.
• Fan.
• Control system operating in automatic mode. It is needed to control all processes. The data is recorded in detail to make analysis easier later.
• Lighting equipment that opens the view from the outside.
• Compartment for preparing compressed air, after which the release of powder paint is provoked.
• And of course the powder coating gun itself.

On video: automated powder coating process.

Several components form the spray gun itself for the powder mixture:

1. An air channel, without which powder painting is impossible.
2. Mixture supply channel.
3. Grounded line.
4. Surfaces that provide charge to particles of a powder composition.
5. powder-air mixture.
6. A nozzle that delivers dye outward.

Powder coating machine Larius CH 200

We present to your attention an autonomous powder painting installation AD CH 200-TRIBO from LARIUS.

The main advantage of this powder spraying machine is that it can be used as an electrostatic generator for powder guns from the CH 200 series, as well as an electrostatic charge control device for automatic and manual LARIUS TRIBO guns, a switch is provided to change modes.

This powder spraying installation allows you to use:

• spray gun for corona (charge powder with high voltage electrodes)
• and a triboelectric type spray gun, where the powder is charged by friction

The installation also allows you to frequently change the color of the paint, while the powder is taken directly from the factory packaging. To change the color you just need to replace the powder box and clean the suction pipe.

Powder painting equipment: selection and self-production

Many of the necessary tools and devices can be made with your own hands. This will save a lot of money, but will require a lot of effort and time. To obtain optimal results, it is recommended to purchase some equipment.

Spray

The sprayer is one of the most important tools; the quality of the spraying determines how the coating will turn out. Therefore, it is better to refuse to create a device yourself and give preference to ready-made options. The principle of painting is that paint particles, passing through the gun, acquire a certain charge.

The device comes in two main types:

1. Electrostatic. The particles in it are charged from external influences. It can be used to paint with any type of powder composition.
2. Tribostatic. This option is simpler; the particles acquire a charge due to rapid departure from the nozzle and friction with each other. This spraying method requires compliance with certain conditions; the quality of the coating is affected by humidity. It is also necessary to correctly calculate the length of the connected hose, which depends on the power of the compressor.

The tribostatic processing method is currently considered the most progressive.
The most popular are the following models of spray devices:

• An interesting option is the Start pistol, especially with serial number 50. This variety is universal and combines both paint application technologies. For this purpose, the device is equipped with an additional tube for tribostatic spraying.
• Leader is more accessible. It allows you to do work at home. It features low paint consumption.
• For professional processes and large-scale production, Tesla equipment would be an excellent solution. The cost of such an installation is significantly higher than previous options, but provides a comfortable level of work.

The uniformity of the covering layer of powder largely depends on the quality of the gun.
Naturally, simpler types of hand sprayers are suitable for independent use.

Important! Regardless of the option chosen, all varieties must be provided with a grounding source.

Crafts enthusiasts can make their own spray gun. The whole process is perfectly demonstrated in this video:

Painting chamber

You can make a spray booth yourself; this does not require complex materials. But many masters believe that this area can be abandoned. Indeed, if the event is held once, then it is enough to prepare a comfortable and clean place, which is covered with thick plastic film. But for constant work, such a device will be useful.

For small volumes, a small paint cabinet is quite enough

Camera creation algorithm:

1. The frame of the required size is welded, a metal profile is used for this. If painting will be carried out in a special room, then if there is free space, the camera is made stationary. The box created should be quite spacious.
2. The profile is sheathed on the outside with iron sheets, and thermal insulation is placed on the inside. It is necessary to achieve extreme tightness, which will save most of the unused powder.
3. For better paint collection, it is recommended to make the floor lattice.
4. Separately, forced ventilation is provided.

You can simplify the task by placing the painting area along one of the walls of the room. Adjacent surfaces are sheathed with sheets of iron, the hanging point is located at some distance from the wall, and a container is placed under it for partial collection of the composition. The space is covered with a thick curtain.

Bake

The oven is one of the most important elements when performing powder painting. It is necessary to melt the composition particles applied to the surface of the part. An important condition is the choice of the optimal temperature. The essence of the polymerization process is that it is not the surface that needs to be heated, but the entire product that is being processed.

Making a furnace

Making such a device is not the easiest procedure. The detailed process algorithm includes several stages.

Preparing the necessary material

To create a furnace you will need:

• welding machine;
• Bulgarian;
• drill with attachments for metal;
• scissors.

Minimum set of tools for creating an oven
And also:

• 100 mm thick basalt wool slabs;
• metal profile measuring 5*2 cm;
• galvanized steel sheets;
• tangential fan;
• heating elements (for a chamber with a width and depth of 100 cm and a height of 200 cm, 12 pieces will be required);
• temperature sensors and control unit.

You can’t skimp on the quality of oven components.

On a note! The manufacture of a drying chamber must be approached with all responsibility. It is better to do the work efficiently from the beginning than to correct problems that have arisen.

Frame creation and connection

The structure is welded according to a certain pattern:

1. Individual calculations are performed. When creating a drawing, much attention is paid to the doorway: to prevent heat loss, the door must fit very tightly.

   
   The section of the profile pipe is selected according to the thickness of the basalt slabs

2. Initially, the external contour is arranged. Its size must fit the internal contour, located at a distance equal to the thickness of the insulation used. Literally, you need to get a “frame within a frame.”
3. Jumpers are installed along the internal contour to secure the thermal insulation.
4. Basalt wool is laid around the entire perimeter.

   
   The internal cladding is carried out according to the same scheme as the external one.

5. Sheet metal is cut, which is used for complete cladding. It is necessary to achieve a tight fit of all joints; for this, the sheets of the internal section are folded at the edges. To save money, the external cladding can be made using gypsum fiber sheets.
6. A place is provided for hanging parts.
7. The tangential fan is being modified separately. Boxes are added to it, which will provide entry and exit. Moreover, the entrance should be noticeably larger.
8. Heating elements are installed on one of the walls. The arrangement order is determined individually and depends on the size of the oven. Temperature sensors are fixed at the top and bottom.

   
   The power cable is selected in accordance with the power of the heating elements

9. Separately, a connection to a 380 volt network is provided. All connections are routed to the electrical panel, where the circuit breakers and control unit are installed.
10. The door is hung. The system is being tested.
11. The heating elements are closed with a steel box with slots at the top and bottom for free air circulation. A hole is cut above the heaters into which the narrow part of the fan box is inserted. The mechanism itself is located outside, which will prevent its damage.

    
    After assembly, the paint curing cabinet should be heated idle

The camera is tested on a powder-treated part and the optimal settings are determined. Since the oven and paint gun are of the greatest importance, they are the ones that are made or purchased first.

On a note! To paint small individual elements, you can use a regular household oven for baking.

A few examples of paints

As an example, we can cite two Turkish-made spraying installations from Promaks - CM-10 and 2CM-10.

The PROMAKS CM10 manual spraying installation allows you to use a wide range of paints and varnishes, including metallic and antique. It is also possible to paint glass and ceramic objects. The CM-10 provides a continuous and stable supply of paint, resulting in a very uniform coating. The equipment is easy to use.

Among the technical characteristics of the installation are:

• adjusting electrical parameters of equipment manually;
• grounding the powder supply hose;
• pressure level release button;
• fine filter;
• ability to control material consumption and volume of supplied air;
• minimum output current - 130 μA;
• operation from a standard network is possible at 220 V/50 Hz;
• the device provides a voltage charge of 10 kW, thanks to which all types of powder paint can be charged;
• Due to the special design of the nozzles, the installation is capable of painting even the most remote areas of the surface;
• if necessary, paint replacement is carried out in a short time;
• the approximate consumption of powder paint is 150 grams per square meter;

For large areas, the Promaks CM10 installation is considered one of the best representatives of this class of equipment.

Promaks also produces the Promaks 2CM-10 installation. It is almost 2 times more expensive than Promaks CM10: its price reaches 160 thousand rubles. However, the higher cost is justified by the reduced consumption of powder paint (120 grams per square meter), as well as the presence of an additional control module. In addition, the kit includes a second gun with hoses and wires for it.

If you need to paint a small surface with your own hands for household purposes, then there is probably no need to purchase specialized equipment. If you need to regularly paint dozens or hundreds of parts, you cannot do without a professional painting installation.

Modern paint and varnish materials make it possible to create a high-quality and durable coating on any surface, regardless of shape and texture. One of the popular new products is powder paint. This raw material is a solid, finely dispersed mass that does not require additional mixing. This type of paint has become a real breakthrough in the field of finishing coating. Initially, powder paint was developed for the oil refining industry as a paint coating (LPC) with an increased protection level. At the moment, powder paint is actively and widely used in everyday life and in the automotive industry.

What you need for work

The powder painting method involves the use of suitable equipment and devices, as well as dividing the process into sections.

Approximate diagram of the line for powder coating

For quality work you will need:

• Cleaning area. All parts undergo mandatory training. At this stage, the old layer is removed and degreasing is carried out. The process can use manual or specialized tools. If you plan to carry out constant cleaning, then sandblasting equipment is the best solution.

  
  The spraying chamber is a cabinet with built-in ventilation

• Sputtering chamber. A separate closed place for applying paint with good ventilation is the key to avoiding further problems. The camera also allows you to save some of the lost paint. In industrial products, a recuperator filter is used to collect unused powder; at home, it can be replaced with a cyclone vacuum cleaner.
• Gun (spray gun) for painting. To work, you need a special sprayer, which you can purchase or try to make yourself.

  
  Standard spray gun design

• Oven for polymerization. It is in such a chamber that the painted part is baked. This equipment should allow you to control the temperature, because the process of coating formation depends on it.
• Final drying area. A separate place will be required to cool the processed product. If the process is not continuous, then a furnace can be used for these purposes after it has been gradually cooled.

  
  A mini-oven for coating polymerization is considered the main unit in the line

• DC source.

A convenient location of all areas should be provided; much attention is paid to the suspension system. Using a hanging trolley can make the task easier. Placing equipment even in a minimal amount will require a fairly spacious room, although some areas can be combined if desired.

Electrostatic spray gun

An electrostatic powder gun functions as follows: powder paint is supplied through one channel, and compressed air, which must be dry and clean, is supplied through the other.

Inside the gun, the particles of the dye are charged at a power of 60-70 kW, which gives them the opportunity to be attached to the surface. This is how coloring occurs. Almost all powder paints are effectively charged, ensuring high-quality coating.

The electrostatic method has its drawbacks, among which it is worth noting the emergence of an electric field between the spray gun and the surface being treated. This reduces the quality of powder paint spraying on surfaces with complex terrain. At the same time, the thickness of the coating decreases.

This effect is called the reverse ionization effect. To avoid creating one when painting, you should extremely accurately calculate the distance from the nozzle of the spray gun to the surface, be sure to take into account the electrostatic characteristics of the powder paint, properly ground the device and regulate the current.

Features of the operation of PC application installations

When applying powder paints using electrostatics - with generators or tribochargers - you need to pay special attention to the reliability of grounding the spray gun and the product being painted. Grounding the sprayer is necessary not only to guarantee the safety of the operator, but also to ensure the outflow of charge, which ensures the continuity of the electrical circuit. Poor grounding of the part and/or sprayer leads to the fact that the PC is not retained on the product, but crumbles and is carried into the recovery system: the powder paint “does not charge.” Regular cleaning of product hangers is the key to successful operation of the installation. The permissible suspension resistances of parts up to 100 kOhm indicated in the literature are often too high for low voltages of the corona electrode or for tribocharging a PC. Avoid extending the ground and power wires beyond the standard ones, especially for hand guns with internal charging.

Powder paint may poorly adhere to and remain on the surface of the product with a film of oil remaining, which is a good insulator, due to poor degreasing, and with uneven degreasing, a decrease in the thickness of the coating on oil stains can be observed with an increase in thickness along the boundaries of the stain.

The successful operation of the entire installation largely depends on the operation of the feeder, so it is necessary to pay special attention to the selection of modes, and for old installations - the selection of special additives that facilitate the transfer of modern finely dispersed PCs into a suspended state.

The following typical coating defect is associated with poor operation of the feeder: the presence of local thickenings on it, which are formed in cases where the destruction of powder paint aggregates in the feeder and ejector is not ensured or the paint is transported to the gun in an excessively high concentration. As a rule, by reducing the PC concentration in the torch (by reducing the air supply to the powder and/or increasing the air supply to the ejector), it is possible to eliminate the presence of paint aggregates in the gun torch.

The same goal is achieved by installing a nozzle on a gun with a special nozzle that prevents a direct jet of powder air suspension from hitting the product. It is also advisable to increase the distance from the gun nozzle to the product.

It should be noted that the same defects can be caused by other reasons, in particular when the gun is turned on, aimed at the product, when the PC settled in the hose is thrown into the torch or when there are places in the hose (detachments of the inner layer of multi-layer hoses, ledges in places connections with fittings, etc.), where the PC settles on the walls and when the gun moves or the air supply starts, it can break off, falling into the torch in the form of caked lumps and aggregates. If the quality of the air used is poor, containing drops of liquid (moisture, oil), non-destructible PC aggregates can also form, which ultimately settle on the product. Hard-to-destroy aggregates also form during long-term storage of powder paint, especially at elevated temperatures and high humidity indoors in combination with unsealed containers. Particular attention should be paid to the possibility of moistening and aggregation of the PC in an unsealed container or when opening the latter too early in the case of moving packages of powder paint from a cold to a warm room, which occurs due to condensation of moisture from the atmosphere of the room on the cold PC. In rare cases, the cause of aggregation is the low glass transition temperature of powder paint, and for domestic manufacturers using soft containers; — improper storage or transportation in high stacks.

In any case, you need to keep in mind that operating modes with lower concentrations of the spray gun torch provide more uniform and economical painting of products, but require longer painting time. For powder paints that are prone to aggregation or contain aggregates for one reason or another, such operating modes should be considered preferable.

Moving the spray jet along the surface of the product at a distance of, as a rule, 200 - 400 mm (depending on the sprayer model) at a certain speed should ensure that a PC layer of sufficient thickness is obtained on it to form a continuous film of a given thickness from it. To increase the productivity of the process on conveyor lines for applying PC, several sprayers are installed in the chamber on special traverses, both stationary and reciprocating in the vertical direction. Recently, high-performance disk atomizers have also been used instead, creating a cylindrical cloud of charged PC through which the product suspended on a conveyor moves in a circle.

For purely decorative coatings, modern materials with good hiding power provide the possibility of painting with a layer thickness of 35-45 microns; for protective and decorative coatings, the optimal coating thickness is 60-100 microns; for purely protective coatings, the coating thickness should be in the range of 60-120 microns, but it can be increased in special cases to 400 microns.

The thickness of the resulting coating depends on the concentration of PC in the spray torch, the size of the torch (which determines the performance of the feeder for powder paint), the speed of movement of the torch (or the time of passage of the product through the spray torch) and, to a lesser extent, on the voltage on the corona electrode (the degree of PC charge) , which affects the percentage of material deposition on the product.

The variety of models of PC spray guns and feeders does not allow us to give other recommendations on their selection and use, however, the following general dependencies should be kept in mind:

• an increase in air pressure to supply powder paint increases the concentration of PC in the air suspension, increases the rate of increase in the thickness of the PC layer on the product being painted, requires a reduction in application time to obtain a given thickness, increases productivity, but can cause uneven thickness of the resulting coating on the product as with manual painting, and with automatic (if the frequency of movement of the traverse with a sprayer is insufficient compared to the speed of movement of the part on the conveyor); the probability of the appearance of aggregates of PC particles in the torch and associated surface defects of the painted part increases;
• increasing the air pressure on the ejector (in different instructions it is called: “dilution”, “spraying”, “additional”, etc.) increases the speed of transport of the air suspension through the hose to the gun, reduces the concentration of PC in the spray, the likelihood of aggregates appearing in the spray spray and, accordingly , reduces the possibility of resulting coating defects; practically does not affect productivity, increases the uniformity of coating thickness, when installing directional nozzles it makes it easier to paint grooves, recesses, etc., however, it requires caution when choosing the distance from the nozzle to the product being painted due to the possibility of “blowing off” the already applied layer; a slight decrease in the proportion of material deposited on the product is possible; with an excessive increase in air pressure (above the “supply” pressure), it can cause interruptions in the supply of air suspension to the sprayer, especially if the hose from the feeder to the sprayer is long or its cross-section is small;
• an increase in the voltage on the corona electrode increases the proportion of PC deposited on the product, allowing for an increase in painting productivity, but can cause unevenness in the resulting thickness of the PC layer and, accordingly, the thickness of the coating (especially on parts of complex shape), the appearance of coating defects due to “rebound” of the layer PC in places where it exceeds a certain thickness limit.

Adjusting the operating modes of sprayers and feeders requires skill, and both the recommendations of their manufacturer and the recommendations of the PC supplier must be taken into account.

Design Feature

The design varies depending on the type of equipment used, since tribostatic guns generally have fewer components. This is a working handle, a tank or funnel, a nut, the inner rod of the tribostatic barrel and the body of this barrel. The gun itself is connected to the compressor. Electrostatic guns are somewhat more complex in their design, since there is a housing with a control panel, a paint tank, a converter with a power supply, a spark gap, an electrode with a nozzle, and cables.

Important. For electrostatic guns, it does not matter what type of powder paint is used.

It can be polyurethane or polyester powder. The painting efficiency will be the same.

Electrostatic powder coating guns

The design of such devices is more complex. The electrostatic powder coating gun consists of the following parts:

1. A housing with a handle on which the control panel is located.
2. A tank filled with coloring powder.
3. Arrester with an electromagnetic trap.
4. Converter (sometimes supplied with a power supply).
5. Electrode with nozzle.
6. Power and grounding cables.

Since the electrostatic field is created here forcibly, any polymer paint, for example, polyester or polyurethane, is suitable for electrification, which gives the electrostatic gun a certain advantage over the tribostatic one.

Provided that dry and clean air is supplied to the mixing chamber (which occupies most of the internal volume of the housing), the charge acquired by the powder particles turns out to be significant. This allows the electrostatic gun to be used to paint large surfaces.

The sequence of operation of the device is as follows. The electrostatic field excited by the discharger creates a potential difference inside the chamber, since the outer part of the housing is grounded. Forces are created that actively mix the mixture and direct it to the exit from the chamber where the hollow electrode is installed. Its electromagnetic trap further accelerates the flow of charged particles and throws it out at high speed.

Since the surrounding air has its own humidity, the force of electrostatic attraction practically does not depend on the distance between the grounded surface of the product being painted and the gun. As a result, charged powder particles are uniformly deposited on the metal of the workpiece being painted.

A different principle of creating an electrostatic field is implemented in pistols from the German company Ransburg. It uses centrifugal spraying from a disk rotating at high speed. To charge the particles, a sliding contact is used, which is located on the disk itself.

The powder flow, under the influence of centrifugal forces, is broken into microjets and drawn out by an electromagnetic trap, after which it is directed to the surface requiring painting. The trajectory of particle motion is located along the magnetic lines of force of the electrostatic field, so the flow is always dense and uniform.

Safety precautions when working with a powder gun:

When working with a spray gun, certain rules must be followed:

– the room where painting work will be carried out must be well ventilated;

– the powder gun must be in good working order and properly grounded, especially for electrostatic guns;

– painting manipulations should be carried out in protective glasses and gloves, in shoes with rubber soles, which will prevent electric shock;

– periodically check the gun insulation;

– do not spray powder paint near an open flame, or at high temperatures, as this may cause it to ignite instantly.

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Equipment and use of tribostatic sprayer

Powder paint appeared on the market not so long ago, but has successfully gained fans due to the success of its application. It allows you to create a high-quality and durable coating with a special mass (powder). This powder is easy to work with; you do not need to mix it or perform any complex actions with it. Initially, this paint was intended for oil refining production, but then it gained popularity in other areas, in particular small-scale production.

• it is convenient for working with objects of various configurations (both small and large);
• it is easy to use and operate;
• has high impact resistance;
• It is possible to regulate the application of a certain layer of paint in thickness.

You can buy a tribostatic gun in the following configuration: pneumatic gun, material tank, sprayer. The simplicity of the design determines the high properties of powder painting and high performance. The tribo sprayer is easy to adjust the spraying speed and has no electrical elements.

The tribostatic gun is offered to buy with various parameters depending on the customer’s needs. The average nominal productivity is 2.5 square meters per minute, air flow is no more than 3 cubic meters per hour, weight is no more than 1 kg.