Currents high frequency(HDTV) have mass beneficial properties. The main one is the ability to pass along the surface of a conductor without affecting its core. Thanks to this feature, the surface of the conductor through which high-frequency currents pass heats up quickly and to high temperatures.

Moreover, the higher the frequency of the currents, the faster and more strongly the conductor heats up.

1 Application of HDTV in industry

High frequency currents are currents in which the number of oscillations per second reaches one million. The voltage in HDTV machines can be from one thousand to several hundred thousand volts.

HDTV devices are widely used in industry.

• using HDTV induction furnaces Any metal melts. The convenience of this method is that it can be used under conditions of complete vacuum. This avoids oxidation and contamination of metals;
• With the help of high-frequency currents, metal is hardened. The peculiarity of such hardening is that only the shell of the product is hardened, the inner part remains plastic. This protects the metal from becoming brittle;
• using HDTV devices, some parts are welded in the automotive industry;
• in medicine, high-frequency currents are used to treat skin diseases, by improving blood circulation in capillaries, joints, spine, and warming internal organs;

The latest invention based on high-frequency currents was a welding machine suspended ceilings from PVC. We will look at this device in more detail.

1.1 HDTV devices for installing PVC stretch ceilings

Stretch ceilings today rightfully occupy one of the first places in interior decoration Houses. They have high aesthetic qualities, are installed fairly quickly, and allow you to hide ceiling communications. In addition, patterns, drawings and even your own photographs can be applied to stretched fabrics.

With the help of coloring and shaping canvases, designers solve issues visual increase space, artificial spot lighting of rooms and much more.

The only problem is that the width of a roll of PVC sheets for suspended ceilings does not exceed 3 meters. And if fabric sheets are connected by weaving, then it is impossible to create a seam on PVC in a similar way.

The seam on stretch ceilings made of fabric or PVC should be:

• durable. The canvas on the ceiling has a fairly high tension coefficient. Therefore, the seam on fabric or PVC must be so strong that it does not tear or stretch either during installation or over time;
• unnoticeable. The beauty of stretch ceilings lies precisely in the fact that they look like a single canvas made of beautiful fabric. Any bends or will significantly reduce the aesthetics of the interior.

It is these two tasks that can be flawlessly solved with the help of a HDTV device for suspended ceilings.

1.2 Device

HDTV machines consist of the following mechanisms:

1. Electric arc suppression mechanism. If sparks or, as a result, an electric arc appears, the welded fabric may burn out. In addition, there is a possibility of failure of the welded electrode itself. Therefore, the machine is equipped with an automatic regulator that reduces the power of the generator in case of danger of sparks.
2. Mechanism for suppressing interference. Because high frequency currents create their own high magnetic field, but are also sensitive to others magnetic fields, the machine is equipped with a screen that creates a kind of protective dome over a separate HDTV device.
3. The safety device protects the machine from power surges.
4. Welding device. This mechanism connects PVC sheets through dielectric heating.
5. Drive mechanism. Most machines are equipped with two types of drives: foot and pneumatic. The pneumatic drive is more accurate and safer, since it allows you to protect the machine and the blade from pinching and other errors by operating personnel.
6. In addition, each machine includes an inverter, which, in fact, generates high-frequency currents.

All these mechanisms are installed on a frame, which is a table. Such the bed allows you to conveniently lay the sheet for welding and avoid bending or distortion.

1.3 Operating principle

The operating principle of HDTV machines for suspended ceilings is based on dielectric heating of two sheets in contact with each other. In the welding process, in some cases, filler materials can be used.

Such devices allow soldering:

• fast;
• evenly;
• reliable;
• warming up only specific points.

The soldering process is carried out using two electrodes, through which a dielectric current passes.

Soldering can be done in three ways:

• end-to-end;
• overlap;
• T-shaped seam.

HDTV machines made in China for PVC in industry used not only for soldering suspended ceilings. With their help they make:

• airbags for cars;
• children's inflatable balls and circles;
• beach slides and attractions such as “banana”;
• beach bags and mattresses, and other PVC products.

1.4 How does the HDTV machine work? (video)

2 DIY HDTV machine

To manufacture a full-fledged HDTV device for soldering suspended ceilings and other PVC sheets doing it yourself is quite problematic, if not impossible.

After all, to manufacture it you will need not only to decide how to obtain high-frequency currents, but also to manufacture or purchase mechanisms for arc suppression, noise suppression, install a press, a drive, and much more.

As for the simplest inverter operating on the basis of Foucault currents for melting and hardening metal rods, it can be made from ordinary welding inverter.

Welding is generally a fairly universal device. With its help, the production and processes of welding and cutting metal are carried out, pyrolysis processes are carried out and, as it turns out, high-frequency currents are obtained for the rapid melting of metals and more.

In the process of making the device with your own hands, in addition to the welding inverter itself, you will also need a water cooling mechanism and a coil, which is best made from copper tube cross section 10 mm. It is this coil that will perform the function of an inductor, or a circuit with induction (high-frequency) currents.

2.1 Manufacturing process

1. A cooling system must be installed inside the welding inverter. This can be water or freon cooling, powerful coolers or heat sinks.
2. From a copper tube with a cross section of 10 mm and a length of 1 meter we twist a spiral - an inductor (according to appearance it resembles a boiler). Both ends of the tube, 10-15 cm long, should be curved in one direction and be at the same level.
3. We clamp both ends of the inductor into the slots of the welding inverter for welding cables.

With this induction device, made with your own hands from a welding inverter, it is possible to melt metal rods with a diameter of up to 10 mm within 20-30 seconds. After this time, the metal will turn red and will be ready for both forging and hardening of the upper layers.

The more turns the inductor has, the higher the frequency of the induction currents.

2.2 How to use the machine?

Using a DIY HDTV machine is quite simple.

1. We turn on the inverter cooling system.
2. We turn on the inverter itself.
3. Let's place the metal rod we need inside the inductor so that it does not touch the walls of the coil itself.
4. We wait 20-30 seconds until the metal turns red and begin working with it.

2.3 Homemade HDTV devices in everyday life

Can be made quite simply and cheaply homemade system heating or water heater based on induction currents. To do this, just wrap the inductor around the pipe ( optimal quantity turns - 90) and turn it on.

In this case, it is important to ensure that the inverter is not turned on if there is no liquid in the system or it is not circulating. Such an oversight can lead to the melting of the pipeline system itself.

When it comes to solid wood furniture, we are talking about hot pressed carpentry. This type of press has proven itself and, depending on requirements, can be equipped in a variety of ways.

The system includes:
- high frequency current generator
- press
- hydroelectric station
- Remote Control.

System Features:
- Usage high frequency heating dielectric medium
- Automatic PLC control
- Loading and unloading tables
- Exposure time of one shield measuring 2440*1200 mm, 1-3 minutes
- Possibility of gluing a board 12 meters long through sequential heating

Press operating procedure:
1. The workpieces coated with glue are placed on the feeding table.
2. By pressing a button, the automatic feed pusher feeds the workpiece into the press.
3. Vertical pressure on the workpieces is created by vertically located hydraulic cylinders, which are turned on automatically, after which the workpieces are compressed by side pressure hydraulic cylinders and gluing them (the workpieces) into a solid panel.
4. The HDTV heating is turned on, the glue is heated (the heating time is set by the staff) during heating, the upper and lateral compression of the workpieces occurs using hydraulic cylinders.
5. After heating, the pressure of the hydraulic cylinders is automatically turned off, the press opens, and the finished shield comes out of the press.

Brief technical specifications

Technical characteristics of the press

Technical characteristics of high frequency current generator 30 kW

Power	AC 38 V, 50 Hz, 3 phases
Input power	40 kVA
Output power	30 kW
Frequency	6.78 MHz
Electric lamp	FU924FA
Filament voltage	AC 7.5
Switching mode	Variable capacitor
Cooling type	Air
Setting mode	Variable Capacity
Type of protection	Two-stage filament heating, overheat warning, electric fan protection, door switch protection
Output mode	One way exit

http://mwm.com.ua/catalog/pr_129

See also:

Press with HDTV heating for the production of laminated boards

6. 2 Manufacturing of furniture panels. 1 Materials for making furniture panels. Sequence of technological operations, equipment used

Specifications

• The bottom plate is 600 mm above the floor level, rigidly fixed to the press frame.
• Dimensions working area 2500x1200 mm
• Press opening 1500 mm
• Stroke of main hydraulic cylinders 1200 mm
• Two main upper hydraulic cylinders 2x 80 tons each
• Max. Pressure in the hydraulic system 250 bar
• Pressure readings Pressure gauge on the press control panel
• Closing speed of slabs 1000 mm in 30 seconds
• Low speed when squeezing 10 mm/sec
• Press opening speed 1000 mm in 30 seconds
• Two side hydraulic cylinders 40 tons each
• Closing and opening speed of side cylinders 1000 mm in 30 seconds

To install the device for lateral compression (pressure) in height (5 positions), there is a series of holes on the racks of the press frame, located at a distance of 100 mm from each other.
The lateral pressure devices are fixed using special fingers.
Stopping the top plate in the upper position using a limit microswitch. (position adjustable)
Switching from high press closing speed to low - limit microswitch (position adjustable).

The press control unit is installed on the press frame.
This control unit contains the following components:
2 buttons to turn high pressure on and off
When the top plate begins to move from low speed, the operator presses the "Start" button, and the pressing cycle ends automatically.
Timer that sets the time during which the press must be closed
Emergency stop block.

Obel- PHDTVGeneratorTypeOPA40 L

HF power - 40 kW
. Air cooling
. 13.56 MHz frequency for industrial use
. Output type - Symmetrical
. Noise protection All devices capable of emitting microwaves are placed in the upper part of the generator and shielded with special protection.

Generator control unit

PLC control - Siemens PLC
. Fully automatic control HF-Power
. Ability to have multiple heating modes for parts various shapes for complex parts.

Safety

In accordance with EU requirements. Ensuring safety - a fence around the press and generator at a distance of 1000 mm. On the loading side, the fence is lighter and opens to supply workpieces.

Some benefitsObel- PHF

Obel-P Generator and press are manufactured by the Obel-P group in Denmark

• Over 60 years of experience in the production of generators and presses
• No RF interference from generator or press (affecting radio waves)
• Fixed frequency 13.56 MHz
• Symmetrical output for efficient distribution of RF energy over the entire workpiece area.
• Fully automatic control of RF generator (Siemens PLC)
• Automatic HF-Poser compensates for changes in power consumption and maintains its maximum value throughout the entire drying process
• Computer control for RF generator
• Possibility of using several control programs for very heavy and difficult workpieces.
• Powerful press frame.
• High quality hydraulics, power supply and cylinders from Danish and German suppliers.
• Omron type microswitches