DE3131367C2 - Process and electrode for the electroforming production of form-forming metal tools - Google Patents

Abstract

The process for the electroforming production of form-forming metal tools consists of the following: The electrolyte flow is conveyed into the space (H) between the model (6) and the electrode (1) and then the model (6) and the electrode (1) are placed on the power source , whereby a deposition of the metal takes place on the model (6). The deposition takes place in a strongly turbulent electrolyte flow with Reynolds numbers of approx. 1.0 10 ↑ 4 to approx. 6 10 ↑ 4, with a current density on the model (6) of approx. 50 to approx. 350 A / dm ↑ 2 and a value of the distance (H) between the model (6) and the electrode (1) of approx. 10 to approx. 100 mm.

Description

worth at flat sections of the model cathode.

The maximum permissible current density is limited by the particular electrolysis procedure, and its increase leads to disturbances of the precipitate structure, ie to rejects. The current density is therefore set in such a way that it does not exceed the maximum permissible value in the protruding sections, but this reduces the current density on the other surfaces of the model cathode. Here, the current density in the depressions of the model cathode decreases even more, which increases the necessary duration of the electrolytic deposition of a metal layer of the required thickness several times.For example, the galvanic production of a copper electrode for an electrical discharge machine takes 400 to 500 hours, depending on the complexity of the work surface of the model. If the model is complicated, the value of the cathode ^{current density is limited to 2-3 A / dm 2.} An increase in the current density above 10 A / dm ² results in the metal on the cathode being preferably in the form of dendrites on the protruding portions of the model and deposited in the form of a foam powder mass consisting of small, weakly interconnected particles

From US-PS 37 04 220 a method for electroforming Production of sieves and corrugated envelopes is known to achieve uniformity Thickness of the electrolytic deposit attach the model to the negative pole of the power source and one as a bundle of wires (Brush) executed anode is connected to the positive pole) of the power source. The deposition of the Metal on the model in the electrolyte is done by adjusting the anodically polarized brush the modelL

This procedure is a variant of the electrolytic rub, so it is not effective for Manufacture of tool electrodes for electrical discharge machines are used, as in the known Process where electrolytic deposition takes place in a small volume without renewing the electrolyte, which makes it difficult to manage the process at high current densities

Japanese Patent 38-12823 discloses a method for the galvanoplastic production of metal mold-forming tools, for example copper electrodes for electrical discharge machines, in which an electrolyte flow through a narrow gap (less than 1 mm) between the profiled and anodically polarized counter-electrode and the cathodic polarized model is pumped through. The metal is deposited on the model at a current density of 400 to 1000 A / dm ^2. The distance between the counter-electrode and the model is kept constant by adjusting the counter-electrode to a control signal that depends on the size of the distance.

This known method allows the achievement of a uniform thickness of the deposited on the model Metal at high performance Electrode spacing corrected profile anode required, which means an increased workload.

The invention is based on such a known method for the electroforming production of molds Metal tools with a stream of electrolyte being fed into the gap between the model and the counter electrode, and it has the task of lowering the manufacturing costs of the tools as well

an improvement in the physical-mechanical properties and the evenness of the metal deposit to achieve on the surface of the model.

The object is achieved in that with a strongly 'swirled electrolyte flow with Reynolds numbers from 1.0 · ΙΟ ⁴ to 6 · 10 *. at cathodic current densities of 50 to 350 A / dm ² and a distance between model and counter electrode of 10 to 100 mm.

The method according to the invention enables a significant increase in the efficiency of the process in the manufacture of mold-forming tools with spherical surfaces. The strongly swirled electrolyte flow with Reynolds numbers from 1.0 · 10 ⁴ to 6 · 10 ⁴ allows the high current densities of 50 to 350 A / dm ² on the model. Numbers below 1.0 · 10 ⁴ and high current densities from approx. 50 A / dm the produced metal layer does not have the necessary quality, in particular no pore-free, finely crystalline and uniform structure, and that with Reynolds numbers above 6-10 ⁴ if the specified size range is adhered to a non-uniform metal layer is obtained for the distance H between the model and the counter electrode because of the various hydrodynamic phenomena occurring in the large gap.

With anodic polarity of the model, it is useful to measure the distance between the model and the counter electrode Reduce 3 to 10 times. This leads to a Comparison of the thickness of the metal layer deposited on the model and eliminates the dendrite growth. A reduction in the distance by less than 3 times results in only a weak equalization the thickness of the deposited metal layer and does not eliminate dendrite growth. One Reduction of the distance by more than ten times leads to the occurrence of short circuits and malfunctions.

If the distance between the model and the counter electrode is reduced, it is advisable to stop the electrolyte pumping interrupt because this increases the thickness of the diffusion layer of the electrolyte on the model surface, which in turn leads to an increase in the selective solvency of the Dendrites on the surface of the model and the The effect of equalizing the thickness of the metal layer deposited on the model is reinforced

It is advantageous to use an electrode in the form of tubes. And a minimal distance between the walls of the pipes according to the inequality

Herein mean:

a - minimum distance between the walls of the tubes,
D - Outside diameter of the tubes.

The tubes are lowered and fixed until they touch the machining surface of the model, and the fixed tubes are then raised by the value of the distance between the model and the counter electrode, which is determined according to the inequality H> 2a, where H is the distance between the model and the electrode and a is the minimum distance

5 6

between the walls of the hollow tubes is then a layer is carried out in a strongly swirled electrolyte

the electrolyte flow through the tubes into the gap intermediate flow with Reynolds numbers Ae = 25,000 and one

see the model and the counter electrode supplied current density on the model 6 of 100 A / dm ² . Included

and across the gaps between the walls of the tubes, a copper deposition rate of

and the gap on the circumference of the processing surface of the 5 0.4 mm / h is achieved, which is 6 to 10 times more than with the elec-

The model is drained trolytic deposition in an electroplating bath.

A counter electrode consisting of tubes acts to equalize the thickness of the copper layer 7 and

decreased because of the smoothing effect of the electrolyte as one to eliminate the dendrite growth

massive electrode, so that a uniform thickness, as shown in the diagrams according to FIG. 2,

of the electric field on the model surface and to periodically and briefly the distance H between

as a result, the uniformity of the model 6 and the counter electrode 1 is increased to one fifth

deposited metal layer results with simultaneous polarity reversal of model 6 and opposite

The supply of the electrolyte through the tubular electrode 1 and interruption of the electrolyte feed

and its derivation via the gaps between the currents. The course of the current / over time τ gives

that of the tubes avoids the formation of congestion zones from FIG. 2, the distance // in the gap from F i g. 2a and

nen at the corners of the model and causes an equal- the electrolyte throughput from FIG. 2 B. Where T is the

moderate swirling of the electrolyte on the working duration of a full cycle (period), η the duration of a

area of the model. Outward current pulse, Ti is the duration of a return current pulse

In order to ses as large a number of tubes as possible, H _mvt the maximum distance between model 6 and

of the given floor plan are 20 counter-electrode 1 (10 mm), Hm " the minimum distance

this is expediently arranged in such a way that the between model 6 and counter electrode 1 (2 mm).

Axes three adjacent tubes in each case during the duration T \ of the outward current pulse

the projection onto the perpendicular to these axes at the distance H _{1711x shows} the deposition of the metal

Form flat points of an equilateral triangle. The model 6 takes place in the electrolyte stream; during the

This arrangement of the hollow tubes also favors a duration η of the return current pulse at the distance

more uniform strength of the electric field on the H _W i " a selective dissolution of the dendrites on the

Model surface and the prevention of congestion model in place

zones, which means gaining a more uniform thickness The interruption of the electrolyte delivery during

The deposited metal layer enables the reverse current pulse contributes to the selective dissolution

The invention is illustrated below by the description of the dendrites, particularly on models with fine

Exercise of exemplary embodiments on the basis of the drawing, because here the thickness of the diffusion layer in

gen further explained It shows the indentations being enlarged. The evenness

F i g. 1 schematically part of a machine for the separation or the dissolution of the metal in the case of the

vanoplastic production of shape-forming metal electrolysis is directly dependent on the

Tools for electrical discharge machining in the 35 value of the distance H between the model 6 and the

rich in model and counter-electrode, counter-electrode 1, thereby increasing the selective resolution

F i g. 2 explain the course of the current (I) over time (r), the dendrites during the return current pulse

F i g. 2a shows the distance (H) between the model and, in addition to eliminating dendrite growth, finds the counter electrode over time (r), compensating for the thickness of the deposited copper

FIG. 2b shows the electrolyte supply to the space between 40 layers

the model and the counter electrode over time (r), the duration Τ \ of the forward pulse was 60 seconds

F i g. 3 schematically a part of a machine for galling and the duration n of the return current pulse 10 seconds

vanoplastic production of shape-forming metal ends.

tools for electrical discharge machining in the case of a

Another embodiment of the counter electrode, 45 formation of the copper layer 7 in a strongly swirled

F i g. 4 shows the cross section along line IV-IV in FIG. 3. Electrolyte current with Reynolds number Ke = 50,000

F i g. 1 shows the glavanoplastic production of a current density on the model of 200 A / dm ² . The copper tool electrode for the electrical discharge machining copper deposition rate was 0.6 mm / h, using a press tool for glass vases. The deposition of the copper during T \ took place on a model! 6 to deposit a copper layer 7, so a distance H _max = 10 mm between the model and this opposite is a counter electrode 1 made of non-rusting steel and the dendrite removal is arranged over a stream Tz at a distance H _mm = 2 mm and in the case of sub-line 2 to the positive pole of a power source, the electrolyte feed is interrupted,
The power supply line 2 is in a housing F i g. 3 shows the electroforming production of a 3 housed before the action of the electrolyte. 55 Copper tool electrode for electroerosive machining in the zone where oxidation processes take place. A plastic cover 4 presses the counterelectrode. Here the counterelectrode is a multitude of copper tubes 9 enclosed in a trode 1 to the power supply line 2. Titanium hollow body 8.

The counter electrode 1 is of a covex shell shape, with a minimum distance between the walls of the tubes 9

in their surface openings for the supply of a sulphate 60. ,. ", _TI,. , "" ^ D """, -. _u "," _u - _n

electrodes are executed. The model 6 of the ^{Preß- Wlrd} S ^{emaß der Un} g ' ^elchun g «* T« ^{ewahlt wobel D}

The tool for a glass vase is connected to the negative pole, which is the outside diameter of the tube

Power source connected. The gap between the ge The hollow body 8 is at the positive pole of the power source

gene electrode 1 and the model has a height connected and serves as a power supply for the Röh-

H = 15 mm. 65 ren 9. The model tO is connected to the negative pole of the power source

The electrolyte flows in the direction of the arrows through the Ie connected and on the plastic table 11 of the

Openings fixed in space H between the model 6 and electrochemical machine

of the counter electrode 1. The deposition of the copper The tubes are kept up to the point of contact with the machining

7 8

Processing surface of the model lowered and fixed in the hollow body 8 in any known manner. Then the fixed tubes 9 are raised above the model 10 by the distance H. The distance H is selected according to the inequality //> 2a, ie it must not be smaller than the outer diameter of the tube.

Electrolyte is conveyed into the hollow body 8, which passes through the tubes 9 into the gap // and is discharged via the spaces between the outer surfaces of the tubes and the circumference of the machining surface of the model 10. The deposition of the copper on the model 10 is done in a highly turbulent flow of electrolyte at Reynolds numbers from I ₁ O-IO ⁴ to 6 x 10 ^4, at current densities in the model of 50 to 350 A / dm ² and a distance // between the model and the counter electrode from 10 to 100 mm.

The counter electrode, which consists of a large number of tubes, acts like a solid electrode with partially profiled work surface, which ensures a uniform strength of the electric field on the surface of the Model 10, the elimination of dendrites and increasing the uniformity of the thickness of the deposited Layer guaranteed. The supply of the electrolyte through the tubes 9 and its discharge via the Spaces between these allow the elimination of congestion zones at the corners of the model and one uniform swirling of the electrolyte on the surface of the model 10. The number of tubes 9 selects one maximally in the given plan of the model; this is arranged in such a way that the axes of three adjacent tubes in the projection onto the plane perpendicular to these axes, tips of one Form equilateral triangle.

In the case mentioned of the production of a tool electrode for the electrical discharge machining of a press tool for an electric razor housing, a counter electrode made of copper tubes 6x1 mm arranged at a distance of 3 mm from one another was used. The working area of the model is 1 dm ² , the area of its projection on the plane perpendicular to the model axis is 0.3 dm ² , the form difficulty factor, expressed by the relationship between depth and width, is 1 to 1.5, the minimum radius of curvature of the surface is 3 mm. The deposition time of a copper layer of 1 to 3 mm is 16 hours, namely with a current density on the model of 50 A / dm ² , with Reynolds numbers of the electrolyte current Äe = 5 · 10 ⁴ and with a distance H between the model and the counter electrode of 10 mm. '

For this purpose 3 sheets of drawings

55

eo

Claims (5)

1 2 for electronic devices. Claims: Electroplating makes it possible to use waste-free manufacturing technology economically and with high precision. 1. Process for electroforming production, probably small parts as well as difficult-to-shape large parts, often Form-forming metal tools under feed 5 with unique physical-mechanical properties Electrolyte flow into the gap between models. However, electroforming has too and counter electrode, thereby identified defects, their field of application and their effectiveness draws that with a strongly swirled elec- restrict. Trolyte current with Reynolds numbers of 1.0 · 10 ⁴ The most important deficiencies in electroplating are to 6 ■ 10 ⁴ , cathodic current densities from 50 to 10 the unevenness of the deposited layer and 350 A / dm ² and a distance (H) between models, the long duration of the metal deposition process. There- (6) and counter-electrode (1) from 10 to 100 mm, these deficiencies in electroplating are closely related. is being worked on. the linked The extent of these phenomena depends 2. The method according to claim 1, characterized by the shape of the model. shows that with anodic polarity of the model (6) 15 the fader is used to calculate the precipitation thickness Distance between model (6) and Gegenelektro- Raday's law, according to which the thickness of the coating is dide (1) is decreased 3 to 10 times. directly proportional to the current density, the electrochemical 3. The method according to claim 2, characterized in that the equivalent, the current yield and the duration are characterized in that the electrolyte delivery in the case of decreasing electrolysis and inversely proportional to the specification of the distance (H) between the model (6) and the mass of the metal to be deposited is The Be counter electrode (1) is interrupted. however, billing only gives an idea of 4. The method according to claims 1 to 3, characterized in that the mean thickness of the precipitate, and even characterized in that an electrode in the form of flat cathodes, which is at the same distance to the ano-tubes (9) used a minimum distance (a) the arranged are, the current density and that between the walls of the tubes can be distributed unevenly according to the non-layer thickness. At the corners equation and the edge, the current density is much greater than the mean value (so-called edge effect), which is caused by the _> _D ^ Concentration of the lines of force of the electric field ~ 2 'is caused by sharp edges 30 To an even greater extent is an uneven one where a is to observe the minimum distance between the Wan current distribution during electrolysis on profile model cades of the tubes and D to observe the outer tube diameters because of the lower mean, then adjust the tubes to different resistance between the anode and the contact with the working surface of the Mo various sections of the lowered as the cathode geschaltedells (6) and fixed, the fixed 35 th profile model and hence the different flow-made tubes (9) sealed by the amount of the distance at these portions explained such a distribution (H ) between the model (6) and the counterelectrulation of the precipitate is defined as the primary distribution (1), which is determined according to the inequality H> 2a and is only in the absence of cathode polarization, where // is the distance between model and geation possible. Genelectrode means raised, the electrolyte 40 The electrolytic deposition of the metal is supplied by electricity via the tubes (9) and is accompanied by the changes in the cathode potential during the pre-splitting between the tubes (9) and via the gap, depending on the current density (H) at the periphery of the working surface of the model (6) a distribution is referred to as a secondary distribution; is derived. it is always more even than the primary distribution. 5. Electrode for Performing Procedure 45 The degree of redistribution of the current and Menach Claims 1 to 4, characterized in that tails on the cathode surface in the sense of a larger one that the tubes (9) are arranged such that the uniformity depends on the scattering power of the Axes of every three closest tubes (9) in the electrolyte. It is quantitatively referred to as a "deviation" Projection onto the level (in percent) of the metal distribution from the primary, perpendicular to these axes Form ne points of an equilateral triangle. 50 power distribution estimated On the uniformity of the distribution of precipitation the electrolyte temperature also has an influence. An increased Temperature reduces cathode polarization, and at high current densities to a lesser extent than The present invention relates to a control 55 at low. This is explained by the fact that the current drives for electroforming production of metal yield decreases with increasing current density and Form-forming tools and the hydrogen released on an electrode intensely see the electrolyte earth to carry out this procedure. The mixed up after the layer next to the cathode, which is their PoIa invention Form-forming profile fabrication to be produced is reduced. The influence of mixing is tools are, for example, die inserts and pressing tools 60 approximately the same as with increased tempera tools for rubber, iCoplastics, casting molds for light doors, d. that is, it degrades the evenness of the me- '; Melting alloys or tool electrodes tall distribution on the surface of the model cathode. ', for electrical discharge machining and electrochemical machines. The shape of the model cathode also affects that ^! : ■ / According to the invention in mechanical engineering, in the duration of the electrolytic deposition of a metal 'M the electrotechnical, electronic and other 65 layer of certain thickness. As I said, the current density in industries thin-walled parts with complicated te on profile model cathodes is not constant. To outstanding > ■ 'Shape, for example nozzles of various configuration, standing sections, they can be several times larger and 'K cladding, reflectors or shielding chambers in depressions can be several times smaller than the central