Using old household appliances to create new equipment is not just saving money, but also a great way to show engineering ingenuity. A compressor from an old refrigerator has unique characteristics that make it an ideal base for creating budget painting station. Unlike bulky industrial analogues, such a unit operates quietly and is capable of producing pressure sufficient for domestic needs.
Creating airbrush or a full-fledged spray gun with your own hands requires an understanding of the principles of pneumatics and the availability of a basic set of tools. The main task is to adapt the refrigeration unit to air injection tasks by adding filtration and adjustment elements. This process is fascinating and allows you to get a working tool almost free of charge.
In this article we will analyze in detail all the stages of transforming a refrigeration compressor into a functional device for painting. You will learn what parts are required, how to properly assemble the system and avoid typical mistakes that beginners in this business often make.
The operating principle and advantages of a homemade device
The main difference between a refrigeration compressor and standard piston models is its tightness and oil bath. Inside the metal case freon unit works in an oil environment, which provides excellent cooling of rubbing parts and minimal noise levels. This is critically important for a home workshop, where a loud hum can disturb others.
Such devices belong to the class lube-free in the context of air supply, since the oil remains inside the crankcase and does not enter the exhaust stream in large quantities if the system is assembled correctly. This allows them to be used for working with surfaces that are sensitive to contamination, although additional filtration is still necessary.
Another important advantage is compactness. The finished device can easily be placed on a mobile cart or even on a shelf, taking up minimal space. Low productivity compared to professional stations is compensated by pressure stability, which is ideal for applying varnish, paint or primer to small parts.
Required materials and tools for assembly
Before starting assembly, it is necessary to prepare all components. The basis already exists - it is itself, which can be extracted from the old technology. However, to turn it into a full-fledged pneumatic system, a number of additional elements will be required that will ensure safety and functionality. refrigeration compressor, which can be extracted from old technology. However, to turn it into a full-fledged pneumatic system, a number of additional elements will be required that will ensure safety and functionality.
The most important element is the receiver - a container for storing air. Old fire extinguishers, gas cylinders or special air suspension receivers are often used as it. You will also need hose fittings, clamps, a pressure gauge to control pressure and, of course, the sprayer itself.
- 🛠️ Compressor from a refrigerator (with a power of 1/8 hp and above).
- ⚙️ Receiver (metal cylinder with a capacity of 10-50 liters).
- 💧 Moisture-oil separator (can be bought ready-made or made from a filter).
- 🔌 Start relay and electrical cable with plug.
- 🔧 Fittings, high pressure hoses and clamps.
Don't forget about the tools: drill, set of drills, wrenches, screwdrivers and possibly a welding machine if you plan to seriously modify the receiver. All metal elements must be free of rust and coated with an anti-corrosion compound.
Preparing the compressor and dismantling the elements
The first stage of work is the removal and preparation of the main unit. The compressor is usually mounted at the bottom of the refrigerator on four shock-absorbing bushings. Carefully saw off the copper tubes, moving 5-10 cm away from the body to avoid chips getting inside the mechanism.
After removal, it is necessary to determine which of the tubes is the output (discharge) and which is the input (suction). To do this, it is enough to briefly supply power to the windings. The tube from which air will blow is supercharger. The suction tube, on the contrary, will draw in air.
⚠️ Attention: It is strictly forbidden to open the sealed compressor housing with a grinder or a hacksaw to “check” the insides. Inside there is compressed gas and oil vapor, and a violation of the tightness will lead to irreparable damage to the unit.
Often a trap filter is installed on the suction pipe, which is better to keep or replace with a new one with similar parameters. This will prevent dust from entering the cylinder. If the old filter is clogged, it should be carefully removed and washed in solvent or replaced.
How to determine the starting relay?
The relay is attached to the side of the compressor and has electrical contacts. If you are not sure of its serviceability, it is better to replace it with a new one that matches the model of your compressor, since starting the engine depends on this.
Manufacture and preparation of the receiver
The receiver acts as a buffer, smoothing out pressure pulsations and accumulating air volume for the operation of the spray gun. Without it, the compressor will turn on too often, which will quickly damage it. An ideal candidate for this role is OU-5 fire extinguisher or a similar cylinder.
Before use, the cylinder must be carefully checked for integrity and absence of corrosion. If there is rust inside, it is removed mechanically or with chemical reagents. Then holes are drilled in the upper and lower parts of the cylinder to install fittings.
A fitting for connecting to the compressor and a separate outlet for the pressure gauge are welded or screwed into the upper part. A drain valve (condensate drain) must be installed in the lower part, through which the moisture that accumulates during the air compression process will be removed.
| Receiver type | Volume (l) | Working pressure (atm) | Features |
|---|---|---|---|
| Fire extinguisher OU-5 | ~7-8 | up to 15 | Lightweight, compact, convenient sizes |
| Propane cylinder | 25-50 | up to 25 | Large supply of air, requires careful cleaning |
| Truck spring | 10-20 | up to 20 | Original shape, difficulty in mounting |
| Ready receiver | 20-100 | up to 16 | High reliability, but high cost |
After installing all the fittings, it is advisable to paint the receiver with heat-resistant paint. This will not only improve the appearance, but will also protect the metal from external corrosion, especially if the room has high humidity.
Assembling the pneumatic system and electrical system
Assembling the system begins with connecting the compressor to the receiver. Use copper tubing or high pressure hose connecting the compressor discharge pipe to the cylinder inlet. It is recommended to install a check valvebetween the compressor and the receiver, which will prevent air from escaping back into the compressor when it stops.
Next, the air preparation unit is mounted. It consists of a moisture-oil separator and a pressure reducer. The moisture separator removes condensate and oil vapor, and the reducer allows you to set the required pressure at the outlet to the spray gun, regardless of the pressure in the receiver.
☑️ Checking the system assembly
The electrical part requires special attention. The compressor is connected via a starting relay, which ensures that the engine starts correctly. It is advisable to supplement the circuit with a thermal relay or circuit breaker, which will turn off the power in case of current overload. All contacts must be reliably insulated.
⚠️ Attention: Do not ignore the grounding of the compressor and receiver housing. Static electricity generated by air movement can cause a spark, which is dangerous in an environment of solvent vapors.
The final stage is connecting the hose to the output of the gearbox and installing the spray gun itself. Check the entire system for leaks by applying a soap solution to all joints. The appearance of bubbles will indicate places that need to be tightened or re-sealed.
Setting the pressure and testing the system
After assembly, it is necessary to conduct a test run. Turn on the device and monitor the pressure gauge readings. The compressor must build up pressure to cut-off (if a pressure switch is installed) or operate until it reaches the maximum value it is capable of. For painting, it is usually enough 2-3 atmospheres.
Adjust the gearbox so that at the outlet to the spray gun there is a pressure recommended by the spray gun manufacturer (usually 1.5-2.5 atm). Too high a pressure will create fog and waste of paint, while too low will result in uneven coverage.
Check the operation of the moisture separator. If liquid begins to accumulate in the filter bowl, it means that the system is working correctly, separating condensate. Do not forget to periodically drain this liquid through the tap at the bottom of the receiver so that it does not get into the paint.
Carry out a test painting on an unnecessary sheet of metal or plywood. Evaluate the spray pattern: it should be smooth, without “spitting” or breaks. If problems are observed, check the cleanliness of the spray gun nozzle and the absence of water in the line.
Safety precautions and equipment care
Working with a homemade compressor requires compliance with safety rules. The device is under pressure, so do not allow the housing to heat above 90 degrees. During long-term operation, take breaks to allow the compressor to cool, especially if it is not equipped with forced cooling.
Change the oil in the compressor regularly (if the design allows for its replacement through a special hole) or monitor its level. Special synthetic oil is used for refrigeration units; regular motor oil can lead to coking of the valves.
- 🧼 Cleaning: Purge the system regularly and change filters.
- 🔩 Fixture: Once a month, check the tightness of all bolted connections.
- 💧 Moisture: Always drain the condensate after each operating session.
The device should be stored in a dry room. If the compressor has been idle for a long time, it is recommended to preserve it by pouring a little oil inside and turning the shaft several times by hand to create a protective film.
What to do if the compressor hums but does not pump?
Most often this means a breakdown of the valve group or piston. In a homemade workshop, it is easier to replace the entire assembly than to try to repair a sealed unit.
Frequently asked questions (FAQ)
Can such a spray gun be used to paint a car?
Yes, it is possible, but with limitations. The performance may not be enough to paint the entire body, and the compressor will work without interruption, which will lead to overheating. However, for local repairs, painting disks, thresholds or interior parts, the power refrigeration compressor will be quite sufficient, provided there is a receiver.
What kind of oil should be poured into the compressor from the refrigerator?
In most cases, in such compressors use synthetic oil type PAG or POE (polyester). Regular mineral oil may react with the refrigerant (if any remains) or may not provide the required viscosity. It is best not to change the oil if there is no urgent need, but simply monitor its cleanliness.
Why does the compressor get very hot during operation?
Heating to 70-80 degrees is normal for piston compressors. However, if the temperature exceeds 100 degrees, check the ventilation, oil level and valve tightness. Also, the reason may be too frequent switching on due to the small volume of the receiver or leaks in the system.
Is it necessary to install a check valve between the compressor and the receiver?
Yes, installing a check valve is highly desirable. It prevents air from flowing back from the receiver into the compressor after the engine is stopped. Without it, the compressed air will tend to push the piston back, creating a load on the mechanism the next time it starts and relieving pressure from the system.