The sandblasting machine is used for processing, cleaning from dirt and polishing products made of metal, wood, and concrete. The design of this device is not complicated, but it necessarily includes several main components.
A sandblasting nozzle is a hollow, threaded tube designed to deliver an abrasive mixture to a contaminated surface. If you wish, you can make a nozzle with your own hands, although the highest quality nozzles can only be purchased ready-made.
Design and characteristics
The purpose of the nozzle is to increase the speed of air flow with sand and form a treatment spot. The straight nozzle has the main elements:
- frame;
- thread for fastening to the nozzle holder;
- confuser;
- diffuser.
The housing protects a person from injury in the event of destruction of the internal nozzle. It is quickly erased by abrasive particles passing through it. At the same time, on the back of it there is a thread for a union nut or clamp, with which it is attached to the handle - the nozzle holder.
The confuser is a long conical hole in the insert that regulates the speed of the supplied mixture. Has standard holes with a diameter of 6–16 mm, with a pitch of 2 mm. The choice depends on the performance of the installation.
The diffuser is conical, short, expands at an angle of 7–15⁰. Thanks to it, turbulence is eliminated and the sand is evenly distributed over the working spot. The outlet of the nozzle can be round or oblong, depending on the size of the workpiece and its shape.
Between the confuser and the diffuser there is a section with a uniform cross-section. Having passed along the tapering cone of the nozzle, air and sand form a mixture of uniform composition.
Venturi nozzle
The complex design of the high-performance Venturi nozzle has an internal diameter with a stepped variable cross-section, consisting of a number of cylinders. The diameter of the inlet hole is almost 2 times larger than the outlet hole. This changes the nozzle parameters and increases the flow rate when operating in one mode. For example, an air-sand mixture comes out of a classic nozzle at approximately 320–350 km/h. When installing a Benturi nozzle, the speed of the outflow flow increases to 700 km/h.
The nozzle has a complex design. In addition to the standard elements, the tip is protected by a shockproof rubber shell. There is an aluminum bushing underneath for strength. Insert made of durable and abrasion-resistant tungsten carbide alloy.
It is impossible to make a Venturi design nozzle yourself. Inside it, the cross section changes stepwise. Each transition has a protrusion. Its integrity depends on a correctly selected radius, which is calculated depending on the difference in the diameters of the transition. Rounding is performed with an accuracy of 0.005 mm. Benturi type nozzles are manufactured using modern technologies on computer-controlled equipment.
Working with sandblasting with a Venturi nozzle
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What is a sandblasting nozzle?
The simplest design is a hollow tube, which has, on one side, a thread, which is necessary to connect the part to the nozzle holder. It is through this part that sand comes out, which is why it is subjected to increased mechanical stress.
Basic geometric characteristics of the element:
- Connecting thread section. The most common diameters are 2 and 1¼ inches. There are also connections where a union nut and a sealing washer are used. Homemade elements are usually connected using ordinary clamps.
- Length. It can vary from 7 to 23 mm.
- Minimum internal diameter. There are 6, 8, 10 and 12 mm.
- Entry diameter. It must match the size of the connecting hose.
The main parameter is the hole profile, that is, its shape. It determines the abrasive output speed and consumption. The profile is also responsible for hydraulic resistance, which affects service life.
Advantages and disadvantages
Sandblasting equipment allows you to quickly clean the surface of various contaminants and outdated finishes:
- dirt;
- oil;
- scale;
- fat;
- dye;
- primer;
- putty.
It takes several times less time to prepare a part for further processing and painting than using detergents and solvents.
Sand is easy to obtain. If used continuously, it can be used several times. It must be sifted and calcined.
The air flow with sand and other abrasives penetrates narrow cracks and small holes. The cleaning speed does not depend on the complexity of the design.
Sandblasting machines have a simple design. It is enough to connect the compressor and a container with sand with hoses.
Disadvantages include operating equipment under high pressure. If a hose ruptures or enters the work area, a person may be seriously injured.
The attachments wear out quickly. A metal nozzle made of abrasion-resistant steel is enough for 1 – 2 hours of operation.
How to choose for a pistol?
When choosing, you need to understand that the cheapest parts are the most short-lived. As a result, replacing such nozzles will cost more than buying a high-quality one right away. This is especially true in cases where large volumes need to be processed.
Channel type
The simplest design is a nozzle, which has a cylindrical hole with the same diameter along its entire length. To improve aerodynamic characteristics, these elements are often made of 2 conical sections:
- Input confuser. It increases the flow force of the incoming sand-air mixture.
- Output diffuser. Thanks to it, the surface area being processed increases. At the same time, the flow energy decreases.
The most efficient nozzles are those with a Venturi profile. The hole in them has 3 connected sections with different geometries. Each of them has its own functions:
- At the inlet there is a confuser expansion with an angle of up to 20 degrees (this is less than that of a conventional nozzle).
- Cylindrical part. The length is about 15%.
- Diffuser part with an angle of up to 15 degrees. The length depends on the size of the nozzle itself.
To reduce resistance, the transitions between individual parts are made with radius rounding.
There are also other types:
- Double Venturi. Adds atmospheric air to the flow. The inlet often has a larger cross-section than a standard Venturi. Double allows you to increase the area of the treated surface. This nozzle is used on large planes.
- Venturi channel with wide outlet. The jet imprint at maximum force is wider than that of a simple Venturi. But such nozzles are rarely used.
- Venturi with square section. Such nozzles are the most productive, but they are rarely used, as they are quite expensive due to the complexity of manufacturing.
Material of internal wear-resistant insert
For household purposes, nozzles made of ceramic or cast iron are suitable. But it should be understood that they wear out quickly, which increases the consumption of abrasive material. It is not recommended to use such elements for large jobs. Tungsten carbide and boron carbide nozzles have a very long service life. They can also be used with almost any abrasive. The exception is aluminum oxide and carborundum.
Containment design and build quality
The shell is required to secure the wear sleeve. It is this that protects the nozzle from impacts. Shells come in the following types:
- Polyurethane. Lightweight and resistant to abrasives, but due to insufficient rigidity it wears out quickly.
- Metal. Typically made of steel or aluminum. Reliably secures the bushing, but it has low resistance to abrasive materials.
- Combined. Polyurethane and aluminum are used. This is the most durable shell.
Build quality is also important. There are nozzles where the threaded part is pressed into the body. They often spoil quickly. If you create a pressure of 8 bar, then such a part may even cause injury or damage to the device. It is necessary that the nozzle be machined from a solid piece.
Peculiarities
A sandblasting machine is a long-time and successfully used device that is used to clean surfaces from dirt. Its main purpose is to create a powerful supply of abrasive mixture. The simplest nozzle holder can be made with your own hands at home, but modern designs not only form a torch (a directed jet of air and sand), but also prepare it, use it economically, and impart the characteristics necessary for a specific surface.
Such devices can be used in a variety of situations - from cleaning the walls of houses to removing rust from a metal surface, and even for engraving on a glass surface. Hence the variety of models, simple, but made in different sizes. The need to work with a certain material and create the proper pressure dictates the requirements for the dimensions of the apparatus and its components. One of them is a sandblasting nozzle.
The importance of this detail is difficult to overestimate, since it is it that increases the flow rate of the mixture from the unit and forms a torch . It is selected according to its intended purpose and performance characteristics, as well as the nozzle holder, which is sometimes considered by craftsmen to be part of the functional bell.
Despite the similarity of the design (consists of a body, threads for reliable fastening, confuser and diffuser), it is divided into different types according to:
- the material of the case (its strength and service life depend on this) and the method of fixation to the handle - a nut or clamp;
- the diameter of the holes in the confuser (selected according to the sandblasting performance indicator);
- diffuser expansion angle;
- the shape of the outlet (round or oval, determined by the shape and size of the object being cleaned).
Standing apart from the simple lineup is the Venturi nozzle . It cannot be done at home, since this will not allow for a stepwise change in the cross-section.
An important difference that deserves close attention when choosing is the material of manufacture. Knowing some features, you can choose a nozzle that is suitable for achieving your goal and will last a longer time.
Operating principles
The sandblasting nozzle is attached to a holder - the end of the hose, with a union nut or clamp. The air flow, passing through the container with sand, captures it and delivers it through the hose to the nozzle. Passing through the nozzle, the mixture is evened out in its composition and increases speed. Coming out of the diffuser, sand particles hit the surface of the part at high speed, knocking out particles of dirt and old finishes.
When installing Chinese nozzles, you need to pay attention to the diameter and method of attachment. They mostly have clamps on them. They are mainly suitable for equipment manufactured in the Middle Kingdom. On devices from other manufacturers, the nozzle is installed through an adapter.
The homemade device is short-lived. It can be used at pressures less than 6 atm. Ceramic inserts are made from candles by drilling out the electrode. Cast iron and steel are drilled. The surface of the hole is rough, sand slows down and at the same time wears out quickly.
In sandblasting equipment, in addition to sand, other abrasive elements are used: crushed glass, metal balls, ceramics.
A nozzle you make yourself will not last long. It will help out when repairing your own car or restoring furniture.
Manufacturers
Experts recommend nozzles from the following companies:
- Contracor - Russia;
- CLEMCO - Germany;
- VMZ - Velikoluksky Mechanical Plant.
German products are known for their reliable performance and long service life. Nozzles from CLEMCO are considered the best. The company produces mainly ceramic and tungsten carbide inserts.
Sandblasting nozzles from the Russian company Contracor are not inferior to them in quality. The main products are boron carbide, tungsten and ceramic inserts are available.
VSW produces conventional nozzles at a budget price. Hobbyists can purchase a variety of attachments - metal, ceramic and cast iron for one-time repairs.
The essence of sandblasting
Sandblasting involves exposing various surfaces to an abrasive material. Sand, shot, silicon carbide, small glass beads, etc. are used as the latter.
Sandblasting is a mechanical action on the surface of small solid particles
Before processing begins, the abrasive is placed in a sealed hopper. Air coming from a separate compressor is supplied through the main hose of the device under high pressure. Passing by the opening of the intake hose, the air flow creates a vacuum in it, which facilitates the suction of abrasive into the main hose. The air, already mixed with abrasive, is supplied to the gun, the main element of which is a sandblasting nozzle, through which the abrasive mixture is supplied to the surface being treated.
Layout of the sandblasting area
As mentioned above, various types of abrasives can be used to perform sandblasting. The choice here depends on the type of surface that needs to be cleaned. Thus, treatment using sand is effective in cases where it is necessary to remove a layer of old paint from a concrete surface, clean brick walls from cement residues, and prepare metal parts for further painting. Abrasives such as plastic or wheat starch are successfully used in the shipbuilding, automotive and aircraft manufacturing industries, with their help they effectively remove old coatings from composite materials.
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Overview of species
Types of functional devices can be divided into:
- pressure (designed for a large area that needs to be treated);
- injection (ideal for non-industrial work).
In turn, injection systems are divided into:
- suction;
- vacuum (the abrasive does not remain on the surface, but is sucked back by the vacuum);
- pneumatic – optimal for carrying out work over a large area.
The nozzle for a sandblasting machine can be:
- different diameters (both outlet and in the holes on the nozzle);
- round or oval cross-section;
- made of different materials - ceramic, steel and cast iron, boron carbide, fluorine (up to 1 thousand hours of operation) or tungsten.
In the description, you should definitely look at the performance of the compressor (this is one of the factors in the correct selection of the tip).
The Venturi nozzle stands separately, it has a complex design and is not cheap, but if the direct-flow nozzle gives an abrasive flow rate of no more than 340 km, it provides an indicator almost twice as high. When creating it, the principle of the Laval nozzle was taken into account, which in many cases determines the optimization of operation and regulation of the direction of the emitted jet.
How to do it yourself?
Craftsmen with imagination and skillful hands often make sandblasting attachments on their own, and this has an undoubted practical meaning. Buying a nozzle for a small rusty spot on a car or making it yourself from scrap materials - the only difference is wasting money or time. There are many videos on special websites in which home-grown craftsmen proudly demonstrate a homemade simple device made of steel or cast iron, a car spark plug. They use gas cylinders as a receiver and show improved models of a ready-made pistol, which is somehow unsatisfactory to use.
Let's look at how you can make sandblasting attachments yourself.
For production you will need:
- an ordinary plastic bottle, the volume of which is no more than 1 liter;
- a gun for blowing and another for inflating tires;
- the camera will need a valve.
The manufacturing process is shown in the video.
If you have a drawing, you can even assemble a sandblasting machine by purchasing its components separately in specialized stores. However, specialists in such work are confident that purchased products have higher functionality and performance . And if we are talking about a large volume of work, it is better to purchase a factory nozzle with good characteristics - shock resistance and long service life.
How to make a budget sandblasting nozzle with your own hands
If the sandblasting nozzle has become unusable, you can make a replacement yourself. True, the continuous service life of such a product will be short, but the cost of consumables will not hit the budget. The base for the nozzle can be a ceramic spark plug or an old ceramic resistor with an internal diameter of 2–4 mm.
The procedure for working with a resistor is as follows:
- Tear off the caps and legs with pliers or saw off with a grinder.
- take an M14 metal bolt, cut off the top, drill a through hole with a No. 5 drill.
- deepen the hole with a No. 8 drill approximately 1.4 cm.
- Weld a wide M5 washer onto the M14 clamping nut on top, and use a No. 8 drill to make a cone from the inside, pressing the future nozzle.
To create a nozzle from a spark plug, you need to proceed as follows:
- Using pliers, pull the contact rod out of the spark plug, after heating it with a gas burner.
- grind off the rolled edge of the spark plug body on a machine.
- knock out the ceramic insulator.
- Use a sharpener to cut the edges of the nut and remove it.
- Use a diamond wheel to cut off part of the ceramic insulator where the central electrode is located.
- attach an adapter with a clamping nut purchased or pre-machined from a bolt to the rod.
There are a variety of sandblasting nozzles on sale, and the service life and performance of the most modern products will be many times higher than that of homemade ones. If you regularly use sandblasting, it makes sense to purchase a high-quality ready-made part, but for a one-time job, if you have the necessary equipment and skills, you can make the nozzle yourself.
How to buy a sandblasting nozzle and nozzle holder
We work on an application system, so in order to buy a sandblasting nozzle or nozzle holder, send us an application by email. You can also call 8-800-555-95-28, the call within Russia is free, our managers will advise you on the selection of equipment, tell you which sandblasting nozzle is suitable for your installation or advise you on the selection of nozzle holders and sandblasting guns.
By choosing us, you will receive:
High quality sandblasting consumables
The best price-quality ratio among competitors
Professional consultation with specialists
