The main two groups can be conventionally distinguished among the examples of the practical application of the pulse magnetic fields energy.

The first one incorporates the electromagnetic forming of metals with a high electrical conductivity. In this case the field diffusion is small enough. The strong skin effect takes a place. The practical execution of these operations is being realized in accordance with the traditional scheme of the magnetic pulse metal working.

The second group of the technologies proposes a force action on the thin-walled metals under the essential penetration of the magnetic fields.

It is necessary to mark we have in mind the transparent workpieces forming by the forces of the magnetic pressure exceptionally. Though there are other methods well known in the traditional magnetic pulse metal working. For example, this is the use of the preliminary coating of the transparent workpieces by the well conducting metals. Also the copper drivers ("Sputniks") with the spacing dielectric inserts (the intermediate transmitting environments) are being applied. These inserts is being placed between the drivers and the workpieces. They execute the mechanical deformation of the workpieces.

Their practical applications are described in the science literature. Nevertheless they did not get the wide-spreading. Many reasons can be named. They have both economical and technical character.

Let us try to distinguish the main of them.

Firstly, the preliminary coating of the bad conducting workpieces is possible when they are massive enough. In the opposite case this operation has no sense. Secondly, the preliminary coating of the workpieces represents the essential addition to the main production operation. It increases to a marked degree the cost of the whole technology process.

The use of the drivers with the spacing inserts decrease abruptly the efficiency of the deformation process and reduces essentially the list of the field methods advantages proposing the mechanical action without an immediate contact.

Besides, the bringing of the additional elements into the method scheme increases the cost of the production operation in the whole.

In the chapters 1 and 3 the suggestions are formulated about increasing of the magnetic pressure forces in the inductor systems for the thin-walled metals working without the drivers or the preliminary coating.

The most attractive suggestion consisted in the use of the inductor systems with dielectric matrix. Such constructions is being distinguished by their simplicity. Into the systems like that the phenomenon of the flat electromagnetic waves penetration through thin-walled conductor screen (it is workpiece) into a free space is being modeled. The screening factor is great enough in such systems. The tangential component of the magnetic field intensity does not penetrate through the workpiece metal practically. The achievable pressure is a maximum. The effective uncontact action on the workpiece is being realized.

Besides of the diffusion processes the problem were analyzed of the thin-walled metals heating under the power magnetic fields action. The found results permited to formulate the basic principles of the inductor systems designing. Into constructions like that the role of the heating processes is a minimum.

At last, in the conclusive part of the chapter 3 the examples of the optimum inductor systems were given. These systems permit to execute the effective stamping of the thin-walled metal plates.

The constructions like that are not described in the science literature. Accordingly, the information about the production processes with the similiar inductor systems is absent.

We will not carry away by the quantity of the manufacture operations where the thin-walled metals working is possible. In the presesnt monograph we will stop in a detail on the only example of the progressive technology. This example is worthy of attention both now and in the future. We have in mind the production of the circuit printed boards for the electrotechnical schemes with the help of the magnetic pulse fields energy.

The object chosen for illustration of the magnetic pulse method possibilities is not accidential. Firstly, it corresponds to the modern level of the requirements to the production processes. Secondly, the demand for the printed circuit boards will grow up only, because they are main devices for the electrical scheme arrangement. Their mass production is conditioned by constant increasing of the different electrotechnical apparatuses manufacture.

However, speaking about the magnetic pulse methods in the progressive technologies we can not limit ourself by the only example. It would be incorrectly and unfairly if we did not menshion the succesfull realizations of the traditional magnetic pulse metal working. In the first turn the assembly and welding operations should be named. Here the joining of metal parts to ceramics, glass and other non-metalic materials are being distinguished effectively. The magnetic pulse pressing of the tubes on the metal tips turned out a very succesfull. This operation permits to obtain joints that can stand the test pressures up to 10⁷ N/m². It can not to mark the achievments in the forming operations according to the schemes of the "compression" and the "bulging".

Thus, we begin the elucidation of the magnetic pulse method application problem from the short enumeration of the known production operations being executed with the help of the traditional magnetic pulse metal working.

There is some agreed-upon classification of the technological operations in the magnetic pulse metal working. In accordance with this classification the operations are being divided into three main groups.

The first of them unites the production processes being executed according to scheme "compression". It is shown on Fig.5.1a. In this case the workpiece is being placed into the inner cavity of the inductor. The magnetic pressure forces are directed to the system axis. The deformation character permits to determine the field action as the operation of compression.

The second group incorporates the operations being executed by scheme "bulging"("expansion"). The graphical illustration of this scheme is given on Fig.5.1b. In this case the inductor is being gone into the inner space of the workpiece to be deformed. The magnetic pressure forces are directed from the system axis. In accordance with the deformation character this production operation can be determined as the "bulging".

The last third group of the operations realizes the production according to scheme "sheet metal forming".

This scheme is shown on Fig. 5.1c. The inductor and workpiece represent themself the parallel flat forms which are divided by the insulating insert. The magnetic pressure forces are directed from inductor to the workpiece. The character of the deformation under the pulse magnetic field action permits to determine the given operation as the operation of the "sheet flat forming". In the science literature the similiar operations are named sometimes the "stamping operations".

The given classification is general one. The each of the distinguished operations can be divided into sub-groups according to the more concrete attributes.

The assembly, separating, welding and combined operations can be carried out by scheme "compression". The forming operations being executed according to this scheme did not find the wide application. The reason consists in the complications of the technical character.

The assembly operations is being used under the pressing of the cable tips.

The wires are being gone into the inner cavity of the tip. Further, the last one is being compressed by the magnetic pressure forces. By the similiar way two wires is being joined by the connecting tube. So they make the tips a pressfit on the ropes, on the high-pressure hoses and other.

The quality of such joining is well enough. Its tensile strength is not inferior to the tensile strength of the cable or wire materials.

The quality of the electrical contact of the cable tip obtained by the magnetic pulse method is not inferior to the quality of the soldered connection. The advantage of the compressed joining in comparison with soldered one consists in that the field action can be executed at the immediate nearness to an insulation not having broken it. More than that in the time of the magnetic pulse compression it is possible to get the cold welding of the tip with wire. This effect is conditioned by the processes of the abrupt heating and cooling of the tip metal. The present processes lead to an appearance of the additional mechanical strengthes increasing the quality of pressing.

In industry the conventional hydravlic pressing is being applied. The main properties of the articles obtained by this way is essentially inferior to the characteristics of the products under the magnetic pulse pressing. So, the electrical contact resistance of the connection obtained by the hydravlic way is 1.5-2 times as much than the analogous parameter under the magnetic pulse pressing.

In the time of the compression the high indexes of the mechnical and tiredness strengthes is being achieved. With the help of the compression the tube tie tips is being pressed. It can be got the tight joints, the connections of the metal tips with the nylon wires.

According to scheme "compression" the joints of metals and glass, ceramics and another non-metalic materials are being relized. With help of the compression the metal rings is being pressed around the insulators. The assembly of the metal articles with the brittle materials is being usually executed with the help of the elastic inserts. The assembly without of any inserts is possible when the brittle articles have the shape of the rotation body or in the case of absence of the stratches and any unevenness.

Under joining of the metalic and non-metalic articles the magnetic pulse pressing affords a high tightness and reliability of the connections. In many cases it increases the operational characteristics of the according units.

The welding operations permit to join both the same and not same metals. The welding of copper-aluminium, copper-circonium was executed in practice.

For getting of welding joint it is necessary the velocities of the opposite motion to be maximum.

In this case under their collision a boundary layer appears. It occurs in consequence of the inertia effects of the metal transfer from one workpiece into another one and vice versa.

The thread on the inner surfaces of the tubes can be executed by the compression. The tube reduction, the hole punching in the side walles of the tubes can be fulfiled according to the compression too. The blanking is being executed with help of the matrices which have the holes with the cutting edges.

The cutting of tubes by the compression scheme is performed with help of cutting out of the ring wastes.

The technological operations according to the scheme "bulging" are fulfiled by the magnetic field pressure of the inductor placed into inner cavity of a cylindrical workpiece.

In the time of bulging they form the cones, flanges, ring and longitudinal groves, stamp any threads, expand the tube ends, perform to join and fulfil other technological operations.

The forming operations being executed by the scheme "bulging" have the list of advantages in comparison with the same actions under the compression. Ultimately, they define a simplicity of the technical realization of the forming operations in the time of bulging.

The separating operations include the hole punching, blanking, trimming, for example. They are performed in accordance with the requirements which are similiar to the conditions of the execution of the same operations under compression. Fulfiling of the assembly and welding operations by the scheme "bulging" does not distinguish as a matter of fact from the same operations being executed according to scheme "compression".

The magnetic pulse stamping of the articles from the sheet workpieces is being performed with a help of the flat spiral single-turn or multi-turn inductors. According to scheme "flat sheet forming" they fulfil stamping of the membranes and the shallow "dishes", the pictures and placards embossing, the hole punching and other.

The workpiece shape is defined by the matrix under the magnetic pulse stamping. The square of the surfaces to be worked can achieve till 0.2 m² in dependence on the capacitor bank energy. In the time of the stamping operations it is necessary to take into account that the magnetic pressure is practically absent at the central part of the inductor system. This fact determines the constructive execution of the matrixes and the practical possibilities of the scheme "the flat sheet forming".

Finishing the description of the main technological operations on deforming of the metals with a high electrical conductivity we shall elucidate briefly the working of some bad conductors by the magnetic pulse method in its traditional personification.

Before we said that the different methods had applied for the transparent metal workpieces deforming. The common thing for them was an introduction in a sheme of the magnetic pulse working the different kind additions.

We will not stop at the workpieces deforming after their preliminary preparation, which consists in coating of the workpiece by a metal with high value of the electrical conductivity. This method did not find a wide spreading and had very narrow area of application. The second suggestion consists in the drivers and transmitting environments application. It got enough wide spreading for the working of the bad conductive metals with a help of the magnetic pulse field energy in the different branches of industry. The practical realization of this method can be illustrated by an example of the press tool for getting of the tight joints of the steel tubes with the bunges having one or several grooves. The scheme of the press tool and the according production operation are shown on Fig.5.2.

After discharge of the capacitor bank in the flat spiral inductor (1) the pulse magnetic field is being excited in the system. The appearing pondermotor forces set in motion the driver ("sputnik") (2) made from a well conductive metal. The driver presses on transmitting elastic environment (3) which acts on a tube workpiece (4) in the radial direction. Under press from the transmitting environment the workpiece metal gets in the grooves of the bung (5).

The authors of the present suggestion recommended to use any restorting plastic insert as the intermediate transmitting environment. The driver should be made from magnesium. It has a high value of the electrical conductivity and of the mechanical strength under relatively small density of the substance.

As it follows from the science publications the got by this way joints could pass a test for tightness which was being conducted under the press equaled to 10^-6 mm

of the mercury column.

In conclusion we will formulate the basic statements of the conducted consideration:

- the magnetic pulse metal working in its traditional personification is the most effective one for the production processes with the well conducting metal workpieces (for example, copper, aluminium and other);

- for the bad conducting metal working they recommend to use the drivers in combination with intermediate transmitting environments;

- the brittle or hard metals working should be performed under the preliminary heating of the workpieces (the plasticity is growing up); this operation can be executed with a help of the so named induction heating being fulfiled by the common inductor (for heating and deforming);

- the absence of any mechanical contacts in the time of field action permits to work out the metal workpieces covered by insulating materials or to perform the stamping through the vacuum chamber walls if they are transparent for the acting magnetic field.
 

The technological processes for the printed circuit boards production is the urgent problem of modernity. This fact is being determined by the following circuimstances.

The first of them is the growing up need of the printed circuit boards. This need is conditioned by continuous increasing of the demand and, accordingly, of the schedule of the products, which are being put by the plants of the electrical engineering industry.

The second circumstance consists in the sharp conflict of the existing chemical way of the printed circuit boards production to the main requirements of modernity: ECOLOGY, RESOURCES SAVING AND ECONOMY OF ENERGY.

In a basis of the existing printed circuit boards production the processes of the chemical etching are laid. The essence of this way consists in some metal coating parts removal from the surface of the foil-clad electrical insulated materials under the action of the strong chemical reagents.

In spite of advantages the technology like that has the obvious demerits:

- the harmful and even dangerous influence on a man and surrounding environment, its continuous pollution and poisoning in consequence of the toxic production wastes accumulation;

- the non returnable loss of the expensive non-ferrous metal - copper dissolving in the time of the ordered printed circuit boards picture getting;

- the essential complicities in the production process automatization and, as consequence, its relatively low productivity;

- the necessarity of the power and expensively costing purificatory systems, which increase essentially the technology cost but can not guarantee the ecological purity of the production.

In the magnetic pulse technology there is not the absurd section. We mean the purficatory systems. Their absurdity consists in the following: purification is being realized, but a guaranteed effect is absent.

The humanity wants to use the absolutely (but not partially) ecological pure products

As fas as the energy economy is concerned the magnetic pulse printed circuit boards manufacture does not ensure it immediately. But an indirect economy of energy takes place. It consists in the expenditures lowering for the one unit production, because one operation permits stamping of 4 -15 printed circuit boards pictures (we have in mind one discharge of capacitor bank in the inductor winding).

Besides, as the comparative calculations show, a prime of one printed circuit board produced by the magnetic pulse method is almost 50 times less than in a case of the chemical technology application (the calculations of the magnetic pulse technology indexes will be done in the conclusive part of present chapter).

In spite of the big schedule of advantages we have to mark that the magnetic pulse field application can not completely oust the chemical technology from the modern printed circuit boards manufacture.

The limitations is being fixed, in the first turn, by the level of the modern pulse techniques and its cost. The acquired practical expierence shows that a manufacture of the printed circuit boards with great sizes is until possible with help of the traditional chemical etching of the metal coating from the surface of the foil covered dielectrics only.

Though theoretically, the magnetic pulse method application is possible in this case too. At the begining a large plate should be divided into some small specimens. The picture on each part can be stamped by the magnetic pressure. And the end operation will consist in these parts assembly in accordance with the odered picture of the demanded large printed circuit board.

Returning to the real possibilities of magnetic pulse method we can point out the great class of the electrical devices with printed circuit boards permitting non alternative application of the magnetic pulse method for their manufacture.

For example, the electrotechnical house hold appliances belong to the devices like these:

- the rectifying and charging devices for different purposes;

- the transforming devices of an electrical energy for the radio and audio-systems line-operating from the voltage of the industry frequency;

- the electrical watches;

- the electrical irons, kettles and other devices of the kitchen equipment;

- some washing mashines and other apparatuses with enough simple electrical schemes.

It should be marked the traditional magnetic pulse metal forming can not be applied. There are many reasons which are conditioned by the field penetration through thin-walled copper foil.

The ways of these problems solving were given in the capter 3 (we have in mind the problems of the magnetic fields influence on the transparent conductors in the whole).

They permited to define the constructive versions of the inductor systems for the practical realization of the suggested method of the printed circuit boards production.

As it was indicated the method essence consists in stamping of the ordered picture in the copper foil. Here are some different approaches to realization of the technology operation in the whole.

One of them proposes the printed circuit board picture getting in the separate sheet foil. After stamping the sheet with picture is being glued on a dielectric plate of the according size. The ordered printed circuit board is being cut out from the got foil-clad material.

The second approach proposes another series of operation by the printed circuit boards production. Immediately before stamping the copper foil sheet is being glued on a dielectric base. After this in accordance with the printed circuit board picture the ordered foil parts is being removed under the magnetic pressure forces action. And as it was before the demanded printed circuit board is being cut out from the got foil-clad material.

Naturally, several pictures should be stamped simultaneousely into the foil-workpiece in a mass production. It permits to get several units of the ready production at once.

The third approach to the magnetic pulse method realization in the progressive manufacture processes proposes to use in the capacity of workpieces the foil-clad electrical insulated materials which are being produced by industry. These foil-clad dielectrics are being applied as raw materials in the traditional chemical printed circuit boards manufacture.

As a matter of fact the first two approaches differ one from another by the sequence of the operation execution only. We have in mind the foil gluing on the dielectric base before stamping or after it. For the printed circuit board picture getting the same amplitudes, time and power characteristics of the acting fields are necessary. The present identity of the electrodynamics parameters is defined by the following circumstance: both in first and in second cases for the operation making the same cutting out of the foil separate parts should be produced.

The third approach where the ready foil-clad dielectric is being used as raw has no principle differences from the first two ways.

Nevertheless it has some peculiarity which consists in what the copper foil is firmly glued on the dielectric base. Therefore for the printed circuit boards production the pressure forces must at first tear off the coating parts and then remove (cut out) them in accordance with the ordered picture. It means for the practical realization of the suggested method the magnetic fields with higher amplitudes and energy are required.

How to realize the magnetic pulse stamping of the printed circuit board picture into the separate sheet workpiece practically may be explained with help of the scheme on Fig. 5.3.

The two main blocks are distinguished on the scheme: the high voltage and inductor systems. The first of them (this is the magnetic pulse installation) consists of the capacitor bank of energy (1) and the controling apparatus (2). The second one consists of the flat inductor (3), the copper foil sheet (4) (as a workpiece), the steel insert (5) and the dielectric matrix (6). Into the matrix body the effect of the plane-parallel field penetration through conducting screen into a free space is being modeled. It permits to achiev the power magnetic pressure forces on a metal with thickness which is essentially less than effective skin-depth (about 10 times) of the field.

A duty of the steel insert between the workpiece and matrix consists in a heat removal from copper foil and a creation of cutting edges along the outlines of punching of the parts to be removed.

In the whole, the scheme works by following way.

Preliminarily the capacitor bank (1) is charging till the ordered energy level. The controling device (2) closes the circuit where discharge of the capacitor bank occurs into the inductor winding (3). In the system the power magnetic field is being excited. It acts on the foil and removes its parts which are not fixed by the steel insert (5) and matrix (6).

As it was pointed out, after stamping the foil sheet should be glued on the dielectric base if it were not glued on previously. Then it is necessary to cut out some plate according to the ordered printed circuit board.

The scheme of the magnetic pulse stamping of the printed circuit board picture into the copper sheet workpiece.

(1) is the capacitor bank; (2) is the controling apparatus; (3) is the flat inductor; (4) is the copper sheet workpiece; (5) is the steel insert; (6) is the dielectric matrix.

The approach realization with use of the ready foil-clad dielectric can be produced with help of the same scheme what is given on Fig. 5.3.

Instead of the sheet copper (4) as a workpiece the foil-clad dielectric should be taken. It is being placed so that its metal coating faces to the steel insert (5) and matrix (6).

As before the current flowing in the inductor winding circuit excites the power magnetic field. Its action leads to peeling, cutting out and removal the foil parts which are not fixed by the steel insert (5) and the matrix (6).

A practical realization of the printed circuit boards magnetic pulse stamping demands the experimental investigations of the main processes fixing the method capacity for work:

 
1) the sheet metal heating: the dependence of the workpiece temperature regime on the amplitude-frequency characteristics of the acting fields;

2) the cutting-out of the sheet metal parts under magnetic pulse fields action: the physical character of the process. its basic indexes;

3) the peeling of the metal coating parts from a foil-clad dielectrics in the time of the magnetic pulse fields action: the physical character of the process, its parameters and connection with cutting-out of the parts into separate sheet workpiece.
 

The investigation objects were the copper plates of thickness  and the flat foil-clad electrical insulated materials with thickness  (the copper foil coating thickness was equal to ).

During the investigations the separate sheet workpieces were being placed on the dielectric matrix with several holes. The holes diameters were 

Under magnetic fields action into the copper plates the parts cutting-out occured in accordance with form and sizes of the matrix holes.

By the same way the magnetic pressure on the copper coating of the foil-clad dielectrics was being investigated. These specimens were being placed on the surface of the same dielectric matrix with the holes. In the time of the current pulse action the coating parts were being removed from the foil-clad dielectrics surface according to the matrix holes.

The main experimental results are being reduced to the following.

1. The frequency and relative damping decrement of currentís pulse found from the oscillograms were equal to  and .

2. The foil melting on the dielectric matrix takes place under the magnetic field intensity  This value can be increased to  if the heat abstruction steel plate with thickness  is being applied. It is being placed between the foil and the dielectric matrix.

3. For the separate sheet workpiece the dependence of the cut-out holes sizes on the magnetic field intensity values were fixed:

a)  under ;

b)  under 

c)  under 

The cutting-out process is being characterized by the early appearance of the conical shape deformations.

After this a break-off occures along the matrix holes outlines.

4. The dependence of the holes sizes on the magnetic field intensity values was got under the field action on the foil-clad dielectrics coats:

a)  under ;

b)  under .

Now we shall analyse the experimental results.

We shall start from the heat processes.

In chapter 3 the formula (3.109) has been got. It defines the magnetic field intensity amplitude what gives increasing of the specimen temperature by the value .

We shall rewrite this formula.

where  - are the electrical conductivity, the substance density, the material specific heat capacity, accordingly;  is the so named equivalent frequency of the magnetic field, ;  and  are the frequency and the relative damping decrement.

A numerical data substitution in the formula (5.1) permits to calculate the field intensity what conducts to the copper foil melting,  (the adopted melting temperature of copper equals to ). A comparison of the calculated and experimental results shows the enough high authenticity of the formula (5.1) for the real heat process description.

The existence of the intermediate steel layer permits to consider the copper foil-workpiece and steel insert as the bimetal what is being exposed to the pulse magnetic field action.

The heat regime of the bimetal environment what is transparent for the acting fields has been investigated in the chapters 2 and 3 (sections 2.3 and 3.7). It was shown that the second layer introduction (in this case it is the steel insert) conducts to increasing of the permissible heating to a temperature where  and  the electrical conductivities and thicknesses of bimetal layers accordingly.

Including this correction factor the specimen melting will take a place when the magnetic field intensity evaluates by a magnitude . It is equivalently to increasing of the permissible heating till the temperature  This is 2.25 times as much than inquiry temperature of the copper specimen melting.

Now let us pass to the mechanical processes analysis. We shall start from the holes cutting-off in the separate sheet workpieces.

The processes character in a zone of the cut-off foil part under the magnetic field action testifies about existence of two physical mechanisms conducting, ultimately, to the holes cutting-off the foil: expansion of the circles in the cutting-off zone (the conical shape of the deformations) and their shear by the holes outlines in the matrix.

One mechanism predominates over other in dependence on the holes size. With decrease of diameter the shear role increases in the cutting-off process under the magnetic pressure forces action.

This conclusion can be confirmed by the calculated estimates for the field intensities when the shear along outline of that or other hole ought to take place.

Let us get a formula for the estimate conducting.

Let the shear occurs along the hole perimeter with radius  in a plate of thickness  under the magnetic field action with the intensity magnitude .

From equality of the pressure forces upon the part what is being cut-off () and the forces making the shear ( where  is the ultimate tangent stress for shear)  we can find that

where  - is the vacuum magnetic permeability.

The reference value of the ultimate stress for shear is  where  is the ultimate tension stress for copper specimens it was defined experimentally, . Thus, .

Substituting necessary numerical data in formula (5.2) we will find the magnetic field intensity calculated magnitudes under which the shear of thin-walled copper plate along the boundaries of the according circle parts ought to occure.

So we have

a)  under ;

b)  under ;

c)  under .

A comparison of the calculation results with the experimental data shows:
 

- the mechanical shear contribution is no essential under the field interaction with the large foil parts;

- the intensity values which were calculated in a view of the shear deformations approach to the magnetic field real intensities which make available the copper foil parts cutting-off; this fact testifies about increasing of the shear role.

Generalizing the results of the conducted analysis it should be pointed out. The increasing of the cutting-off process under the magnetic pulse field action is possible if the leading role of the shear deformations is being afforded in comparison with the tension deformations.

It is obvious the previous tension of the foil parts which are being cut-off leads to the essential energy losses and to falling down of the cutting-off process efficiency in the whole.

One solution of this problem can be based if to proceed from the physical analogies.

Obviously a stroken mechanism of action gives to the specimen elements the same initial pulses (but not displacements). In an ideal it permits to exclude the tension and make sure the ordered outline shear only.

In practics the magnetic field frequency increasing permits approaching to the stroken mechanism of action.

Let us finish with cutting-off in the separate sheet workpiece and analyse the copper coat removal from the foil-clad dielectrics surface by the magnetic pressure forces.

From the physical considerations it is obvious the present operation can be conditionally divided in two partials: the first of them is a coat separation from dielectric base, but the second partial consists in the parts cutting-off on this coat along the ordered outlines.

Using the experimental results for the separate sheet workpiece and for the foil-clad specimens we will execute the estimate of correlation between the pressure force amplitudes which are necessary for practical realization of the operation distinguished partials by the metalic coat removal from the dielectric surface.

Proceeding from the measured values of the magnetic field intensities we can define the pressure amplitudes which are necessary for the holes cutting-off with diameters  and . They will be equal:  and .

By the same way we will find the pressure magnitudes which are necessary for the circle parts removal from the copper coat on the dielectric base. Taking account of the experimental intensity values we will get:  and .

The general pressure is the sum of the results for cutting-off and removal of the according parts.

Consequently we can find the pressure amplitudes which are necessary for the separation of copper from the base as a difference,  and 

Accordingly, the ratios of the force indexes of the conditionally distinguished partials of operations by the foil-clad dielectrics working out will be equal 

These figures speak that the main energy of the magnetic field is being spent for the foil separation from base under the printed circuit board picture stamping in the conducting coat of the foil-clad electrical insulated materials.
 

The possible approaches to the practical realization of the printed circuit board production by the magnetic pulse method were described in the part 5.2. One of them (the simplest approach for excution) proposes the printed circuit board stamping in a separate sheet foil. After this operation the sheet with the picture is being glued on a dielectric base. From the got foil-clad material the printed circuit board is being cut out. This plate is the end product of the manufacture.

The pointed out approach for execution of the demanded technological operation was put to an evaluation test. It gave the positve results.

As a specimen of the printed circuit board from the charging-rectifying device D2-10M for the microcalculators of kind "Electronics" was taken.

For the evaluation test execution the simplest variant of the inductor system with paired current-carrying conductors and the dielectric bandage was chosen. This construction was described in the chapter 3 in a detail. The inductor system scheme and its material execution are shown on Fig. 5.4 and Fig. 5.5 accordingly.

The flat inductor system with the paired current-carrying conductors for stamping of the printed circuit boards for rectifying and charging device D2-10M,

a) the scheme of the inductor system in assembly;

b) the inductor with the paired current-carrying conductors;

(1)- is the inductor; (2) is the insulating insert; (3) is the copper foil-workpiece; (4) is the steel insert; (5) is the dielectrical matrix;
(6) is the dielectrical base of inductor.

 

Fig. 5.5

The experimental inductor system: the flat inductor with the the paired current-carrying conductors on the dielectrical base (on the left) and the dielectrical matrix with steel insert (on the right).

In the technological operation what was being modeled the workpieces were the separate sheets of copper foil with thickness .

The experimental inductor system was being connected to an output of the magnetic pulse installation MIU-10 what was created at the Kharkov State Polytechnical University. The installation parameters: the bank capacity , the own inductance , the maximum energy kJ, the capacitor voltage varies over a range  kV.

For understanding of the occuring processes we will calculate the basic characteristics of the inductor system and the magnetic pulse action indexes on a copper sheet workpiece.

At beginning in accordance with adopted symbols (chapter 3, section 3.5) we will point out the concrete parameters of the inductor system: , , , .

The first basic characteristic is the system inductance. We would conduct its calculation by the same way as it was done in the part 3.8 proceeding from the approximate equality of the electromagnetic energy of the inductor current to the magnetic field energy into the space between the surfaces of current-carrying conductors and the sheet workpiece.

From the correlation what is analogical to the formula (3.111) we can get

where  is the volume of the space between the surfaces of the current-carrying conductors and the sheet workpiece;

is the magnetic field intensity into the space with volume , in accordance with the full current law 

According to the inductor system geometry on Fig. 5.4 we find after all substitutions, that

Substituting in the formula (5.4) the initial datum we get the inductor system inductance magnitude . With allowance for the own inductance of the magnetic pulse installation we can find the general inductance of the whole discharging circuit .

The expected frequency of the current is being defined by the correlation (3.121), . The wave resistance of the discharging circuit can be calculated by formula (3.122),  Ohms. The relationship between the current amplitude and the capacitor bank voltage is being found with help of (3.123) . Finally, the amplitude of the magnetic field intensity into a working zone of the inductor system we will get from the dependence (3.124), .

As it follows from the experimental results given in the part 5.3 a realization of the printed circuit boards picture stamping requires the magnetic field intensity with amplitude . Consequently the necessary capacitor bank voltage varies over the range kV. It accords to the energy range  kJ.

Further we will execute the estimates of the steel insert influence upon the magnetic pressure forces and the heat processes into copper foil-workpiece.

The pulse field penetration through thin bimetal layer into a free space was considered in section 2.3. The got results speak that presence of the steel insert in the experimental inductor system must lead to appearance of the non trivial magnetic field on the boundary copper-steel. This fact has to become a reason of the force action falling down on the sheet workpiece to be stamped.

Let us evaluate the magnetic pressure change. With help of the formulas (1.3) and (2.36) we will get that

Substituting the numerical values of the bimetal copper-steel parameters in the formula (5.5) we find that  Hence it follows that magnetic pressure amplitude decreases by 4%. It means the steel inserts influence on the force action efficiency is a very little practically.

At the same time as it was shown in the part 3.7 the steel presence conducts to growing up of the permissible temperature of the copper foil heating  times. It can be easy evaluated the steel insert usage permits to increase 1.56 times the permissible temperature of the copper foil heating. It accords to the possible growth up of the acting magnetic field intensity of 25%.

Now, we will calculate the cross distribution of the magnetic field intensity in a working zone of the experimental inductor system. These calculations are necessary to estimate the homogeneous degree of the magnetic pressure on the copper foil under the printed circuit board picture stamping.

Let the current density in the inductor changes by sine law in time, , where  is the amplitude,  is the angular frequency.

Having used the formula (3.78) we will find the tangent component of the magnetic field intensity what is being excited by the inductor current on the copper foil surface into working zone of the propsed inductor system. Substituting  in the got relationship we can write the intensity magnitude according to the first maximum of the current time function.

where

is the cross space coordinate in the relative units of measurement,

The installation work has been described in detail in the part 2.1. Its principle scheme is shown on Fig. 2.5.

In the time of the present investigations conducting the inductor system with paired current-carrying conductors was being hooked up to an electrical output of the signal oscilator. It simulated the capacitor bank discharge into the inductor winding in the real devices for the magnetic pulse metal working.

The field intensity was being measured in the central part of the inductor working zone with a help of the coil sonde, the integrating circuit and oscillograph.

The measurement results in the relative units are presented on Fig. 5.7 (we keep in mind the ratio of the signal real amplitude to its maximum value!).

For the according calculations the numerical datum should be substituted. They include the construction parameters, the sheet workpiece to be deformed and the field frequency in the inductor system. The process last characteristic was equal to kHz. It was defined from the magnetic intensity oscillograms.
 

The calculation results in the relative units  are presented on the graph of Fig. 5.7. The found dependence illustrates the cross distribution of the magnetic field intensity in the conditions of the conducted experiment. It should be marked the acting fields frequencies in the magnetic pulse real processes are higher essentially. They are over the range  kHz.

Thus, on Fig. 5.7 the results of the calculations (formula 5.6) and measurements are given. Their comparison shows some disagreements of the calculated and experimental data at the outer boundary of the working zone. But into the inner area the results of calculations and measurements are in a good agreement. This fact permits to use the formula (5.6) for evaluation of the magnetic field distribution on the sheet workpiece surface what is situated in zone where stamping of the printed circuit board picture occurs.

For the intensity calculations in the conditions of the real process it is necessary as before the inductor system parameters, the workpiece characteristics and the acting field frequency to substitute in the formula (5.6). We want to mark the time characteristics of the acting field have been defined from the oscillograms of the current pulse in the inductor winding (one of them is presented on Fig.3.14 in the part 3.7). The process frequency were 50 kHz (the calculated result was 57 kHz!).

The calculation data of the intensity cross distribution (in the relative units!) are given on Fig.5.7.

As it follows from the calculations, the frequency increase leads to appearance of an essential inhomogeneity of the magnetic pressure forces on the copper foil in the central part of working zone. It means practically the acting field amplitude has to be increased for execution of the stamping process the whole area of the printed circuit board picture. The least intensity on the foil surface must accord to the demanded pressure. It means the intensity amplitude increasing 1.5 times! It has to change the charge voltage range:  kV. An avarage value of the capacitor bank voltage will be equal -  kV.

As a result of the conducted experiments the specimens have been got. They illustrate the magnetic pulse stamping under the different values the capacitor bank energy. These specimens are presented on Fig.5.8.

So the specimen (1) accords to the voltage 13.8 kV. Obviously this energy level is sufficient for the party stamping of the printed circuit board picture into the foil. But under the voltage what is equal to 16.2 kV (the specimen (2) testifies!) the realization of the sharp picture takes a place.
 
 

is the relative intensity, ;

is the cross-coordinate, ;

· - is the experiment.

Thus under the capacitor bank voltage 16.2 kV(the calculated value is 17 kV!) the pulse magnetic field creates the pressure what is sufficient for the succesfull stamping of the printed circuit board picture in copper foil with thickness  and does not heat the workpiece till melting temperature.

In conclusion we will mark the conducted evaluation test of the magnetic pulse stamping of the printed circuit boards is the practical illustration of its possibilities for the progressive technologies creation only.

If to speak about the mass industrial manufacture then the suggested inductor systems demand some retrofitting. Obviously it is the productivity increase, the creation of the connecting devices (comfortable for exploitation!) to the magnetic pulse installation and the automatic gadgets for erecting and taking off the objects to be worked, the construction elements strengthening and other.

But the suggested construstions foundation what was built with a help of the conducted investigations results and provided the practical capacity for work is staying the same one as it was in the simulated inductor system.

All calculations of the technical and economical indices will be conducted in accordance with a cost of similiar works which was being executed at the Kharkov state polytechnical university and with the electroenergy prices in Ukraine.

These estimates can serve as a rough guide under the comparison of different manufacture ways for the same production.

- the high voltage magnetic pulse plant with stored energy  kJ, the maximum working voltage 20 kV, the guaranteed discharge cycles quantity , the maximum productivity  and with cost of making $15000;

- the overall dimensions and mass of the plant , about 800 kg;

- the inductor systems complete set what consists of 100 units (in accordance with guaranteed discharge cycles quantity of the high voltage magnetic pulse plant) by the total cost of making about $15000.

- as the raw materials for the printed circuit boards production the following things can be used: the copper foil with thickness  and the dielectrical plates with thickness  as well as the foil-clad electrical insulated materials which are being usually applied in the traditional chemical technologies for the same purpose;

- the possible dimensions of the printed circuit board what can be made: ;

- the least width of bars and distance between them: ;

- the least radiuses on the plate picture: ;

- the precision is the same to the chemical method, practically.