Sandblasting nozzle for karcher: sandblasting from a high pressure washer

Tips for builders | 06/23/2017

The famous brand Alfred Kärcher GmbH & Co. KG, which specializes in the production of high-pressure cleaning equipment, has been promoting sandblasting attachments for its equipment in the specialized market segment for a long time. They are intended for cleaning rust from metal surfaces using a jet of water, which is applied to the product mixed with sand. So what possibilities does the sandblasting nozzle for karcher give us?

Manufacturing method from a spray gun

Sandblasting can also be done using a spray gun. For assembly you need to prepare:

a gun that functions as a mixing valve;
handle with air supply device;
a plastic bottle that acts as a tank for abrasive;
tee;
ball valve for regulating sand supply.

Using an airbrush instead of a spray gun will allow you to apply abrasive at higher pressure due to the smaller thickness of the outlet channel.

Assembly is performed in the following sequence:

The gun is bored to increase the diameter of the output nozzle.
The mixing tee is attached to the gun.
The supply and circulation hoses are installed and attached.

Alternative manufacturing methods

The many options for homemade sandblasting are determined by the needs of the owners and the different materials available. You can make your own effective installation using products intended for other work. For example, a high-pressure washer unit will help you assemble a dust-free sandblasting machine with your own hands. Below are several working and effective options for homemade installations.

From a pressure washer

You can assemble a sandblaster from Karcher. This car wash creates high water pressure with low water flow. To obtain an efficiently operating dust-free installation, you just need to assemble a special nozzle for the outlet tube. Required:

a self-made or store-bought ceramic nozzle;
reinforced hose;
mixing block, a tee with a suitable fit diameter is suitable;
feed adjustment unit, cylindrical type dispenser;
a tube for collecting abrasive, equipped with an air supply path into a closed container with sand or other material.

Water sandblasting from Karcher operates on an ejector circuit. High-pressure water passing through the mixing unit at high speed creates a vacuum in the abrasive supply path. Sand flows in and out with high pressure fluid.

The water sandblaster of this design has some features.

The flow intensity is high with low water flow. This allows the installation to be used for glass, frosting or other processing.
For stable feeding, an abrasive of uniform dispersion and small fraction must be used. For domestic use, fine, sifted river sand is suitable.

From a blow gun

Small and efficient - this is how sandblasting from a blow gun can be described. This device will allow you to carry out, for example, body work with fairly high efficiency. However, the performance depends entirely on the compressor used. To assemble the device you will need:

ready-made pneumatic blow gun;
plumbing tee;
ball valve for adjusting the abrasive supply;
outlet nozzle with clamping nut.

The design is not complicated. How to assemble it can be seen in the next photo.

Either a lightweight powder fire extinguisher bottle or a plastic bottle can be used as a container for abrasive.

Using a spray gun

You can create a homemade sandblast using a spray gun. For this you will need:

mixing valve from a conventional spray gun;
handle with air supply mechanism for the spray gun;
bottle for abrasive mixture:
tee;
ball valve regulator.

The operation diagram of the finished device is as follows:

To assemble the structure you will need:

sharpen the spray gun to use a nozzle of the required dimensions;
attach the mixing tee to the gun;
install and secure the supply and circulation hoses.

Important! The supply of sand or other abrasive from the container is started by simply pressing the trigger. The volume of the bottle is enough to treat small parts or surfaces for 20-30 minutes.

Sandblasting from Karcher: nozzle for Karcher high pressure washer

A DIY sandblasting attachment used for installation on a standard Karcher machine will allow you to turn such equipment into a full-fledged sandblasting unit, useful in many situations.

Most Karcher washing machines operate under high pressure, so their technical capabilities are quite sufficient to supply sand through such a nozzle.

The difference between such a homemade device and a classic sandblaster will be that sand will be supplied through its nozzle along with water, but this is not critical for many situations.

Kärcher wet sandblasting kit

How does a sandblasting nozzle work?

The operating principle of any sandblasting installation is that abrasive material from a special hopper enters the nozzle under the influence of an air flow supplied under high pressure.

In serial installations, a separate compressor is used to create such pressure, due to which a significant amount of kinetic energy is imparted to the sand stream emerging from the nozzle. In the case of a Karcher washing machine, the pneumatic equipment built into it will be used for these purposes.

As a nozzle for such equipment, you can use a serial gun, specially designed for equipping pneumatic treatment plants, but in order not to spend money on such a device, you can easily make it yourself.

In order for your homemade sandblasting nozzle, which you will use for installation on a Karcher device, to be effective and not malfunction, you must use high-quality materials for its manufacture.

Of course, the equipment assembled in this way can, at a stretch, be considered as a full-fledged sandblaster, but it is quite suitable for cleaning various surfaces with a stream of water mixed with sand.

When using such a sandblasting device, it is very important to adhere to two recommendations:

It is better to use distilled water as the working fluid, which will avoid corrosion of the metal elements of the nozzle;
the sand that will be used as an abrasive must be of a very fine fraction and carefully sifted.

Diagram of a sandblasting nozzle (click to enlarge)

A self-assembled sandblasting machine, the basic elements of which are a Karcher mini-washer and a homemade nozzle, will work according to the following scheme.

When you press the start button on the nozzle gun, water under high pressure created by the compressor flows past the opening of the intake hose, the other end of which is placed in a hopper with sand. This creates a vacuum in the intake hose.
Under the influence of vacuum, sand is sucked from the hopper into the main hose, where it is mixed with the water flow.

In order to minimize sand consumption and bring this parameter to a value of 30 kg of abrasive for processing a surface area with a diameter of 70–80 cm, the design of this equipment must be supplemented with taps and dispensers.

Homemade mixer from water taps and tees

What can you use a homemade sandblasting machine for?

The effectiveness of using a sandblasting unit with a homemade nozzle, assembled on the basis of a Karcher apparatus, is ensured by the fact that sand mixed with water is supplied from a nozzle under high pressure, which is created by the built-in compressor of the device. Possessing significant kinetic energy, such an abrasive jet is capable of effectively cleaning various surfaces.

It takes no more than 5 minutes to clean a propane tank from rust and paint.

A homemade sandblaster, assembled on the basis of a Karcher sink, can be successfully used to solve the following problems:

cleaning surfaces from various types of contaminants;
removing old coatings from surfaces: paint, glue, building mixtures, etc.;
removing areas susceptible to corrosion from metal surfaces;
cleaning metal surfaces before further processing.

Despite the simplicity of its design, a homemade nozzle for Karcher devices, designed for sandblasting, is highly effective in cleaning various surfaces.

The fact that such a nozzle is a convenient and effective device is well demonstrated by the video of its use. Such a video, as well as videos on the manufacture and assembly of such a device, can be found on the Internet without any problems.

Recommendations for safe use of the nozzle

When using a homemade nozzle on a Karcher machine for sandblasting, you should adhere to safety requirements when working with such equipment. When using a Karcher washing machine, only water is supplied from its nozzle, which is not capable of harming the health of the operator. When using a sandblasting nozzle, in addition to high-pressure water, sand is also supplied from the tip of such a device, which can seriously injure the person operating such equipment. That is why when using such an attachment it is important to strictly adhere to the following safety rules:

Processing should only be carried out in special closed-type clothing;
shoes used for treatment using such a device must also be closed;
All sandblasting work is best done outdoors.

Protective equipment when working with a sandblasting machine

Considering the fact that when using a Karcher apparatus and a homemade sandblasting nozzle, processing is carried out using a mixture of sand and water, it is not at all necessary to use face and respiratory protection in such cases.

When starting to make a sandblasting nozzle with your own hands, you should keep in mind that it will work effectively only if the compressor of your Karcher mini washer is capable of producing a stream of water under a sufficiently high pressure.

More on the topic: > Do-it-yourself sandblasting: drawings, videos, manufacturing instructions > Homemade sandblasting gun > Do-it-yourself sandblasting chamber: drawings, components, assembly

Peculiarities

Hydrosandblasting, also known as water sandblasting, also known as hydrosandblasting machine, is one of the types of devices for supplying an abrasive jet when cleaning various surfaces. The specificity of such equipment is that here the jet is formed due to the supply of water.

Therefore, we can say that sanitary and epidemiological standards prohibiting working with quartz sand without eliminating dust are fully observed. In addition, surfaces treated in this way warp less and are better cleaned.

For cleaning, a combination of quartz sand and water is mainly used. Other abrasive materials are in much less demand. An important condition for normal operation of the system is the unhindered pushing of the mixture with water under pressure through the nozzle.

Another advantage of pre-mixing the abrasive with water in the chamber is the ease of handling large parts and hard-to-reach areas. Sometimes it is possible to reduce abrasive consumption by 30-40% when compared with traditional dry processing methods.

In addition, cleaning surfaces with a water jet is a fairly gentle procedure on the material of the parts. Heating of the treated areas is guaranteed to be excluded, so they are not deformed and their appearance does not change.

Also worth noting:

almost zero risk to the operator’s health (due to the absence of dust);
obtaining a slightly rough coating (surface adhesion improves, which is good, for example, for subsequent painting);
effective work with brick and natural stone;
adjustment of work intensity;
the ability to wash caustic soda and other detergents;
guaranteed removal of dirt, rust, scale.

Small particles of sand knock out the dirt. The surface takes on a matte appearance. It is much better to apply primer, varnish or paint to such a base. Additional polishing is greatly simplified. It is hydrosandblasting that makes it possible to obtain samples for studying the macrostructure of alloys. In the industrial sector, many parts cleaned in this way can be ground without lengthy pre-etching.

However, there are also disadvantages:

it is impossible to work with hygroscopic materials;
water will splash;
puddles will appear on the floor.

There are also the following disadvantages:

the adhesion of wet grains of sand makes it difficult to assess the degree of cleaning;
the appearance of rust (can be prevented by introducing orthophosphoric acid and some other additives, but this requires additional costs);
the penetration of water into microscopic cracks allows it to remain under the paint layer and activate oxidation;
low productivity (dry sandblasting allows you to do much more work per unit of time).

Rules of application

When hydrosandblasting operates, the pump draws liquid from the reservoir. Connecting it to the water supply is prohibited. This inevitably results in a hydraulic shock that destroys the entire water supply system. You also need to ensure that there is a stable flow of pressure-compensating air. In box-type chambers, although small parts are processed, they are processed in fairly large batches.

In this case, operators monitor the progress of work through a control glass. When working using the open method, you can turn on hydrosandblasting only when using special suits, special shoes and safety glasses.

Waterjet treatment is carried out using:

glass beads;
regular and quartz sand;
aluminum oxide;
soft blasting.

It is strictly forbidden to direct the water jet at yourself and other workers, as well as at foreign objects other than the workpiece being processed. The composition of the working fluid is selected according to the problem being solved. To reduce the corrosiveness of water, sulfonic compounds are used. The optimal amount of abrasive suspension in the liquid is selected experimentally, but in most cases it ranges from 20 to 30%.

It is necessary to carefully select the processing mode. By varying the proportions of the components in the suspension, it is possible to carry out rough cleaning, fine grinding, and preparation for painting.

Before starting work, you must carefully check the serviceability of all equipment, the tightness of the hoses and the accuracy of their connections. The first thing to do is start up at idle speed to make sure the equipment is working properly. Only the next step can be the full processing of the parts or surfaces themselves.

Assembling a sandblaster from a gas cylinder

The simplest design for self-assembly is a homemade pressure-type sandblaster from a gas cylinder. The following elements will be required:

ball valves – 2 pcs.;
gas cylinder;
a piece of pipe from which a funnel is made for filling the chamber with sand;
tees – 2 pcs.;
hoses with a passage of 14 and 10 mm, respectively, used to transfer air from the compressor and remove the mixture;
clamps for attaching sleeves;
fum tape intended for sealing threaded connections of apparatus parts.

In order to assemble the sandblaster, you must perform the steps in the following order:

Preparing the tank. Remove all contents from the container, clean the inside surface using non-abrasive detergents and wait until it dries.
Making holes in the cylinder. The top one will be used to fill in sand - its size should correspond to the diameter of the selected pipe. The bottom hole is for connecting a tap.
Crane installation. The regulator can be tightly welded or screwed through an adapter pipe.
A tee and a mixing block are installed behind the tap. Fum tape is used to seal the threaded connection.
A tap is mounted on the cylinder valve, behind which a tee is installed.

At the final stage, you should take care of the mobility of the device - weld wheels or handles for moving. To increase resistance to do-it-yourself sandblasting, supports from corners, pieces of reinforcement, and tubes are welded.

Then the elements are connected to create channels for supplying and discharging the mixture:

fittings are placed on the tee located below and the balloon valve;
a sleeve with a 14 mm passage for air flow is placed between the mixing block and the tee;
an injection unit is connected to the unoccupied branch of the tee with a fitting;
a hose for the finished mixture is connected to the remaining outlet of the lower tee.

To ensure tightness, a screw cap should be installed on the pipe for filling the cylinder with sand.

What can sandblasting be made from?

To understand how easy it is to make sandblasting with your own hands, it is enough to dwell on the operating features of each structural unit. In this case, the selection of available parts or finished products becomes obvious.

Mixing unit. Sand for sandblasting and compressed air from the compressor come here from two hoses. The output is a ready-made air-abrasive mixture. In this case, no requirements, for example, the volume of the mixing chamber, are imposed on the unit. On this basis, you can use a regular plumbing tee to make it.
Control devices. A normal manual sandblaster should be able to adjust the air flow and the intensity of the abrasive material. In this case, no requirements are imposed on the control device. At home, this role is well performed by water ball valves made of steel.
Connection points. To connect the hoses, conventional fittings are installed on the portable sandblasting machine. They can be equipped with clamps for secure fastening. All these components are easy to buy in stores.
Receiver. This part of the design is needed to facilitate the operation of the compressor and stabilize the pressure. You will definitely need a receiver if you want to get a powerful sandblast with your own hands. This device can be made from a powder type fire extinguisher with a large housing capacity. Another option is to make a receiver from a gas cylinder.
Abrasive chamber. The components for its manufacture may differ depending on the type of installation being created. For example, an ejector-type mini sandblasting machine is assembled with a plastic bottle for abrasive. A pressure installation will require a durable container made from a fire extinguisher or a freon cylinder.

Important! The connection diagram for moisture separation and oil collection devices depends on the specific product purchased for this purpose. However, most of the models on the market will only require the manufacture of an outlet from a plumbing tee onto which the hose fittings are mounted.

Nozzle manufacturing process

A homemade nozzle for Karcher can turn a washing unit into a functional sandblasting unit for home use. You will need the following set of consumables:

a hose that can withstand high water pressure;
trigger hook;
dispenser to save abrasive consumption;
a nozzle into which a mixture of water and sand will come out.

Do not experiment with making a homemade nozzle if you are not a professional in this matter. It is necessary to accurately drill a hole with the required diameter. The market is saturated with ready-made parts and consumables of decent quality at reasonable prices, so it’s better to purchase them. In addition, the finished parts already have a trigger mechanism in the kit - a hook.

The hose you will use must be at least two meters long, durable and reinforced. A stream of water with high pressure will pass through it, which will be created by the compressor. Strength is also important because the unit will work with abrasives, so a product of dubious quality will not last long.

Algorithm of actions

Using a thread, the tip is fixed to the nozzle.
A dispenser is also attached to the nozzle, which regulates the supply of sand-water mixture.
The container with sand is connected via a hose; for this, a suitable clamp and fitting are used.

To save the most sand, you should prepare a special container with a grate. Above it, you need to carry out the necessary cleaning of the surface using a sandblasting nozzle. The water-sand mixture will accumulate in this container. This mixture can be used again if a reinforced intake hose is lowered into it. The grate covering the container is needed to keep waste from being cleaned so that it does not contaminate the sand and water mixture.

How does a sandblasting nozzle work?

Karcher with a sandblasting nozzle consists of the following components:

AWD Preus mini-compressor, which is included when the consumer purchases basic cleaning equipment from the Kärcher brand.
A serial gun that controls the flow.
Adapter attachment designed for use with water-sand mixture.
A hose whose manufacturing technology takes into account the significant abrasive effect of the flow on the walls.
Containers with sand.
Receiving nozzle for sand selection.

When all of the above elements are connected to each other, the receiving nozzle is immersed almost to the bottom of the container with abrasive, after which the high-pressure water supply is turned on. By adjusting the flow rate using an adapter, you can control the diameter of the water-sand mixture and the intensity of its impact on the surface being cleaned. The duration of sandblasting is determined by the amount of sand in the container.

The characteristics of the sandblasting nozzle for kärcher declared by the manufacturer are:

The maximum developed pressure is up to 140 at;
The recommended distance from the adapter to the surface to be treated is no more than 300 mm;
Hose length – 3 m;
The nominal consumption of abrasive for processing flat surfaces is 50...60 kg/m2;

It should be noted that, for the compactness of the installation, it does not include dispensers and control valves, and sand is sucked in exclusively due to the vacuum created in the main water line. Judging by user reviews, this is a significant design flaw in the device.

However, the features of the practical use of the hydrosandblasting nozzle for Karcher are not only this.

Sand for hydrosandblasting

It’s worth starting with the choice of consumables, since the principle of sandblasting itself is trivial. Unless the flow of sand is supplied directly from the compressor unit, but is captured from the tank by a flow of water, which has a sufficiently high kinetic energy for these purposes. This is precisely the subtlety of using sandblasting nozzles for Karcher

The instructions for use recommend that the user only use sand supplied by the nozzle manufacturer. And this is no coincidence. Those who did not pay attention to this detail then pay with a sharp decrease in the speed of the cleaning mixture, and, accordingly, a decrease in the efficiency of sandblasting. There are plenty of reviews on the problem that has arisen.

Sand used in sandblasting nozzles has a number of features:

Extremely uniform in fraction - 0.3...0.5 mm, no more and no less (a finer fraction will only produce grinding; the disadvantages of larger fractions will be discussed later).
The particles have a rounded shape in plan, without sharp protrusions and corners.
The sand must be strong enough so that it does not crush and disintegrate into smaller fractions after the first use.
The supplied material must be completely dry before mixing with water.

Sandblasting with a high-pressure washer can be used to clean relatively small surfaces of a simple, flat shape (the sand consumption coefficient when working with more complex configurations will be several times higher). The sand itself cannot be recycled or recycled after processing. This is explained not only by the difficulty of collection, but also by the need for particularly thorough cleaning, since waste sand contains particles of materials torn off from the cleaned surface.

The technology for preparing “branded” sand from kärcher is characterized by a high degree of purification of the starting material – river or quarry sand. After grinding in high-precision ball mills, the semi-finished product is additionally calcined. This increases mechanical strength and makes it possible to use the abrasive for sandblasting not only relatively soft non-ferrous metals and alloys, but also steels. During the preparation of sand, larger fractions with a diameter of more than 0.6 mm enter the container: the grains of sand become noticeably heavier, and the kinetic energy of the water flow is insufficient to capture them and deliver them at the required speed (at least 350 km/h) onto the surface to be cleaned.

Main components of sandblasting machine

Homemade sandblasting is assembled on the basis of standard schemes, differing in the method of supplying sand to the contaminated part. Despite the existing design differences, the components for both options are the same:

compressor - a device for pumping air mass;
a receiver necessary to create the necessary air supply;
abrasive tank;
gun - the main device designed to supply an abrasive mixture to the surface to be cleaned;
hoses.

Sandblasting machine device

The device, regardless of the assembly scheme, forms a combined output flow of air and abrasive. When assembled according to a pressure circuit, sand under the influence of pressure enters the outlet pipe, in which it is mixed with the air supplied from the compressor. To form a vacuum in the abrasive supply channel in ejector devices, the Bernoulli effect is used. Sand is fed into the mixing zone under the influence of only atmospheric pressure.

The existence of many options for sandblasting manufacturing schemes is explained by the possibility of creating it from materials at hand, which often seem unnecessary. To understand the essence of the process, it is enough to consider the general principles of assembly.

Nissan Patrol QD32 › Logbook › Sandblasting from Karcher and eliminating bugs

The patrol is a good car. But it is highly susceptible to corrosion. I wanted to treat the hidden cavities with a liquid rast-stop, and from the bottom outside with a thick one. Rust-stop is a good thing, but if it somehow stays in cracks and hidden cavities, then in open, level places it is quickly washed away, especially by reagents and petroleum products that somehow get on the asphalt (everyone has noticed that on the highway, “windshield wipers” smear on an oily film on the glass?). Therefore, I couldn’t smear it, I had to eliminate the bugs at least in open areas and paint it. This is what the frame and side members looked like before work began:

These are the worst places. At the same time, I feel the frame and side members inside with my finger through the technological holes - everything is smooth there, i.e. The paint is still in place. It’s strange, on Padzherik it was the other way around.

I was puzzled as to how to clean off the rust. It’s not realistic to use your hands; you can’t get anywhere with a drill or an angle grinder with a carriage brush. The ideal option is sandblasting. But I need a powerful compressor, which I don’t have. And then on the internet I came across a sandblasting attachment for a Karcher. This is what she looks like:

I immediately ordered it on ozone and the next day I held it in my hands. Of course, the money they ask for it (4200 rubles) is probably not worth it as a product (like all Karcher products have an inflated price tag). But looking ahead, I will say that I have never regretted the purchase, because... it saved me a lot of time and effort. All that remained was to find sand. There are no instructions for the attachment, only pictures on the box. The picture shows a bucket of abrasive and its number according to the original catalog. Having punched the number, I found out that the original abrasive comes with a fraction of 0.2-0.8mm. I started looking for fractional sand.

In our village this is a hopeless occupation. But a friend helped me by fitting an open bag from his work. This bag was enough... um... well, just to start. The 15-20 kg that remained in it ended instantly. The consumption of sand turned out to be simply enormous. I started scouring the internet for ordering fractional sand. I found some website (for some reason it can’t be Googled now), placed an order for the minimum quantity (500 kg), but the manager never contacted me. I went to Leroy Merlin and bought regular construction sand “Bolars” in 25 kg bags. I took 6 bags. The website says that the fraction is 1-2mm. In fact, it was different in each bag, from small to large. So 1-2mm is probably the maximum size of sand grains. Unlike the fractional one, it contains dust, which clogs the nozzle. But you can work if you get used to it.

Started to get sandy. I removed the pegs for better access. At first I worked as a Karcher K5 (borrowed from my brother). Then I finished it with K3. The latter takes a little longer to clean, but the difference is small. The advantage of water sandblasting is that there is no dust. The downside is that the cleaned metal surface is quickly covered with a thin layer of rye. In progress:

Where the rust is ingrained and has grooves, it is better to use fine sand, because... large ones take a long time to get it out of the cracks. It is better to clean off scale with coarse sand. All this action requires good equipment. The glasses that come with the attachment are UG. Uncomfortable and do not fit well, sand flies into the cracks. In general, after the sandblasting procedure, the underbody washing I experienced earlier seemed like a children's party.

It's time for painting. After drying, a coating of rye appeared on the metal.

It can be easily removed by any rust converter. But here is a pipe and a jug. After the reaction, the converter must either be cleaned or washed off with water. It’s not possible to clean it off everywhere, but when you wash it off with water, you get back a coating of rye. I tried to wash it off with gasoline, but it didn’t wash off. Therefore, after washing it is necessary to quickly dry, degrease, prime and paint.

After painting, I covered the sills with anti-gravel BODY 950 and put a couple more layers of paint on top (since the body is porous, it is better to paint it on top). Later I’ll go through everything with a rust-stop. In the next part I’ll tell you about the rear arches