So, there was a task to make compressor for providing of compressed air to
above mentioned wax injector. Air consumption for injector is minimal; the main condition is continuously pressure control. Pressure should be controlled in scale of 0,5 up to 2 kg/cm2. But anyway the amount of air should be enough to connect the aerography device, as well as paint sprayer with nozzle up to 0,5 mm (with receiver, certainly).

But anyway – not to multiply the devices under my table (due to the space limits of my flat), this device should be strong enough to make vacuum needed for production of formed amount, as well as for vacuum production of two-components rubbers. (I`d like to inform that it will not properly operate with thick solutions like Vixint).

The most available parts for this purpose always were compressors from fridges.

Step 1: Inside

So, about compressor. In first I cut the head of compressor, in order to get an access to inner parts of compressor for further work.

There is shown on picture why you should not rotate compressor. Motor is hanged in middle of housing by meaning of three springs. These springs are fixed to the wedges, inserted in earings of housing. Motor should be removed by lifting it in direction upstairs. Than you should cut all not useful parts. Plus and minus lines should be connected by oil-resistant pipes, connected to rests of cooper pipes inserted in housing. Now you can do it not where they are available, but where it is convenient for you.


The previously cutted piece is not suitable because oil should flow on cover to inside of tank. I had to do the cover from brass foil, using soldering. There are reinforcement ribs inside, on outside I glued linoleum for noise damping. On cover`s top is breather valve located.

As has been found out, if you make proper sealing of minus and plus pipes, the pressure inside of chamber will not be changed (atmosphere). It means, cover is necessary for oil collection in order the dust will not get inside. Please notice – shaft has a hole, there is oil pouring out from all sides.

Than, I made removable level measuring device. Compressor (like all oil compressors) is driving oil fog, that `s why general oil level is continuously decreasing. Indicator made of plexiglass (made from old handle), with marks “min” and “max”, will be fixed on thread with sealant. Indicator is covered by cap against dust, but not airtight.

Step 2: Box

Please put all the parts in housing. Frame should be welded from steel L-profile with dimensions of 25x25mm. Walls can be made from every material. I found aluminium 3 mm. In order to check oil level without dismantling of half of device, I made on the right sidewall door with latch.

Door in housing. Is needed to check oil level without dismantling of housing.

Step 3: Pneumatic Scheme.

Let`s begin with pneumatic. Electric system is logical continue of pneumatic.

1- Minus input (blowing-in fitting)

2- Incoming filter. Cleaning of incoming air. Car precision filter of type FT-206.

3- Manometer to check vacuum level. At that time there wer no normal manometers available, that`s why I took one with scale 0 up to 2 kg/cm2 and aligned arrow on 1 kg/cm2. It will be an indicator. Anyway there is a normal one on vacuum chamber, therefore I use it.

4- Compressor, taken from fridge

5- Air filter of type FV-6. Consumption up to 6m3/h, or up to 100l/min. Is in serial production in Russia. You can buy it by Google. Filter has oil refluxing plug, it is specially made for collecting it.

6- Normal manometer 0-2 kg/cm2. Acc.to test results, compressor can make pressure until 6 kg/cm2, but this manometer is enough for my purposes.

7- Electro-pneumatic (discharging ) valve. Please find information about it below.

8- Back valve. Please find information about it below.

9- Output forcing fitting

10- Receiver. External device for compressor

11- Pneumo-regulating device. It`s fixed on receiver. It`s in use for automatic pressure control in receiver. This device has screw for control of pressure. When there is reduction of pressure in receiver, pneumo-regulating device is responsible for switch on the compressor.

Attention! Compressor should not be switched on in main pipe with pressure. Otherwise the start winding will burn. After start of compressor`s motor, increasing of current through working winding occurs. Coil of start relay will take the core element with contact surface in. Contacts are feeding the start winding. Motor is starting to spin fast. After motor`s spin up, the current will decrease through work winding. Under gravitation force, core element falls down and interrupts the coil winding.

That`s why the devices specified by digits 7 and 8 are needed.

I had no electric pneumatic valve of 220V, that`s why I had to put transformer. I hope you will not repeat my trial. (Nowadays on web-market there are devices available which can replace devices specified on my plan by digits 7 and 11. These devices are called pressure relay, or – pressure switcher. There is no pressure control in these relays, but you can add the reductor on output area).

There is normal-open couple of fittings on valve. After switch on of compressor, the valve is closed, air is going out through back valve to receiver. Then you should inflate the receiver. Compressor is going to be switched off, also the valve, the valve is bleeding (to atmosphere) the air from area “compressor – back valve”. If there is no back valve, air from receiver will go out.

But you don`t need it, do you?

Step 4: Electric

So, here everything should be clear.
Пр– it means fuse Power is provided by switcher, but usage of switcher is not necessary – anyway the power of compressor will be switched on by upper buttons. So, the most upper – is pneumatic-electric relay on receiver. Then you can see pedal with button. I use it for creation of vacuum.

ПО- start winding, РО- working winding. P1- starting relay.

Relay or pedal is connected by ШР`s sockets.

Pay attention! It is important not to be mistaken with the windings. Whatever the design of the compressor, the working and start winding have different resistance.

Left photo- control of pedal. Right- control of PE relay.

As a receiver I used old fire extinguisher. There is “switch on” button placed above SHR socket. This is needed to check compressor in operation when external control is not connected. In first specification, there was an option to switch on the oil level marking lamp.

It's important.

The compressor can give up to 6-8 kg / cm2. I just do not need. Therefore, when choosing receiver consider your pressure.

Meanwhile, few words about oil. The question is not so easy as it seems to be from first look. You can use the special compressor one of type VDL100, certainly, but we don`t prefer the easy way, do we? That`s why I used motor oils. The motor oil (which is OEM for Russian automotive plant LADA / Zhiguli) has obtained pure viscosity level, it didn`t reach the requested distance on hole inside shaft. It happened in non-heated garage condition. The best was KAMAZ motor oil. I even didn`t tried to test compressor oil.

So, it`s all. The device is under table. There are two pipes going outside only.

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