Such devices are usually expensive and when they broke every user tries to repair them himself (you may see the information of Prof.A.Kaidalov and Dr.U.Demchenko - The Exchange of Technologies, 2002 - There are known many examples of microplasma repair and restoration of press tools, press-forms, punces, rolls, cams,cut edges of tools and details of aero engines, last of them are given, for example, in - However, such repair is not simple because the main parts of turbine blades, stamps, pressforms, scissors, shears and precision instrument are made from high alloy or carbon steels. During their welding a user has a very big risk of distortion, weakening and crack formation of base material. Essential deformations may be as a result of overheating, and they can lead to defective goods.That is why users try to come up with such methods of welding that generate high energy concentration in heating and melting zones.Let us see what possibilities we have in order to repair for example moulds used in plastic machinery, based on Internet information-site, on our private information and on a few published works. We shall use part of the Table from the mentioned site, but, with addition the microlasma and medium current plasma which are used in Ukraine and Russia (the former USSR) successfully now.

X Pulsed ND:YAG Laser CO2 laser and YAG laser Microplasma and and medium current plasma TIG (argon welding)
Type of deposition wire powder usual wire and powder wire wire
Area of application (Volume) small/medium medium/large medium medium/large
Size (minimum) of welding (mm) 0.2 - 0.8 0,6 - 1,2 < 3 0,5 - 5
Heat input in mould low medium medium high
Preheating required for
high - hardness alloys
no yes no/yes yes
Degree of automation semiautomatic fully automated manual manual
Investment,  USD ($) 30,000 - 90,000 > 500,000 < 8,000 5.000 - 15,000

As we see, if to suggest the proposed set using, which price may be $4,500- 7,000, the microplasma method of molds repair and restoration can be in a real competition with laser and argon (TIG) welding.The matter is that, although laser gives a much more narrow zone of heating than microplasma, microplasma and the medium currents plasma, give this zone in 8 - 2 times more tight than argon arc. As compared with argon - TIG - welding, plasma processes may be operated with arc lenghts 1- 8 mm (instead of 1 - 3 mm), and non-qualified worker may take advantage of this operation because plasma processes are very stable and be not afraid of arc length changing or of filler wire position alteration.It is impossible, for instance, to touch this wire to the tungsten electrode (which takes place during argon welding rather often) because this electrode "hides" inside plasma forming nozzle.This diameter is nearly 2 mm which has limited the spot of melting or the width of the forming weld usually to the size of up to 4 mm. The focused spot size of the laser beam is typically between 0,3 and 0,6 mm in diameter, and it is not simple to find by it the wire and the seam for which fullfiment the parts of a mold have to be assembled very closely.Since lasers are high-energy light beams they are very critical to reflective properties of welded materials. Laser welding machine for molds repairing has appearance of a table with two windows for operator's hands, optical system for his eyes and working zone with limited sizes. So, sizes of a detail or part which has to be repaired also has to be limited. And, as we see, not every user may buy laser machine (because of high prices and the necessity of high qualification of working personnel). In addition it needs a very clean room and some complex accessories.

According to the "Technological Instruction for Microplasma Restoration and Repair of Stamps, Pressforms and other Goods (TI 156-88), developed in the E.O.Paton Electric Welding Institute, the users of this technology have to take into consideration the following main operations and precautions:

  1. prepare an item that has to be repaired, making it clean and open in the working zone, using pre-heating, if necessary
  2. welding, surfacing and cladding have to be done at the straight polarity ("+" on an electrode, "-" - on a good - detail)
  3. any conventional filler material may be used which, depending on the base material and exploitation conditions, includes, besides ferrum, such main elements: C (usually more than 0,2%), Mn (0,6-1,8%), Si (0,17-1,7%), Cr (0.2-23%), Ni (0,3-11%), S and P (usually less than 0,03-0,04%)
  4. the number of welded layers has to be no more than 3
  5. if the square of surfacing is large, the process has to be led uniformly with respect to the whole space of a treated detail
  6. in the case of a split, knock or face damages the surfacing is fullfiled in the direction from the center of a detail to its edge
  7. the welding arc switching off has to be done on the filler material, and in many cases, as a filler material, it is better to use the flux cored, in other words - powder wire (for example, PPAN-148)

We have to add that in the majority of cases as a shielding gas may be used argon, helium, their mixtures, sometimes Ar+ 1-2%H2 , Ar+15-25%CO2 or CO2. The defective place has to be enough opened and in order to fill it up better, especially at its edges, a supporting ceramics may be sometimes used. It is important to note that the proposed by us new set permits, if the good-detail is not very loaded, the use for its repair as a filler material some alloys on the copper base - brasses and brozes. In this case we really have welding-brazing processes. If in the future, as an option, microplama spraying or cladding is chosen ( please, see Kalina P.P., Yarovitsyn A.V., Yushchenko K.A. "Peculiarities of the Microplasma Powder Cladding Processes", Paton Welding Journal, N.4, 2005, p.p. 7-13), it can give many more possibilities for moulds, stamps and similar structures repair, as well as producing.

We have to take into consideration that the restoration and repair of the new set usage is much easier because its foot pedal permits to change immediately many more parameters when compared to the similar sets. At the same time the proposed set gives possibilities to use as a filler material not only usual wire and flux cored wire but also the pieces of non-standard materials (parts of broken needles and small suitable bolts, some brazing materials, etc.), which is usually impossible when laser machines are used.Moreover, as we wrote before, the new set allows for possibilities to use it for repair and restoration welding-brazing processes.

Besides moulds, stamps and pressforms our sets - cheap, safe and simple sets and blocked plasma set - may be successfully used for repair and restoration of different cutting instrument like scissors, shares, punches, rolls, cams, gears, various armature tools (you might find it helpful to look through the materials of the company Fluidyne Engineering India PVT Ltd).

Due to the exclusive narrow welds and local heating zones, laser repair is a great achievement of the welding technology (,,yet it has some specific features which may not be suitable for an ordinary user: "The laser beam-delivery optics are typically 5 to 6 inches away from the workpiece, and positioning is done via motorized work-stage and joystick control".

Throughout the world a lot of turbine blades are needed and part of them are manufactured using microplasma technologies. Only Israel has two big plants - in Naharia and Kyriat Gat - which produce various turbine blades for many countries.The corresponding equipment, especially with TV control (for example, "LAWS-1000 laser automated welding system"), is very expensive (nearly $200,000). We suggest that our sets may be used for turbine blades manufacturing - in manual mode - as well as for their repair.

Being cheap, easily operated, unpretentious for exploitation new welding - cheap, safe and simple - sets can find an essential niche in the welding equipment market.

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