GB2179959A

GB2179959A - Electrolytic treatment of profiled workpieces

Info

Publication number: GB2179959A
Application number: GB08618535A
Authority: GB
Inventors: Jeno Pojbics
Original assignee: LATSZERESZETI ESZKOEZOEK GYARA; Latszereszeti Eszkozok Gyara
Current assignee: LATSZERESZETI ESZKOEZOEK GYARA; Latszereszeti Eszkozok Gyara
Priority date: 1985-08-02
Filing date: 1986-07-30
Publication date: 1987-03-18
Also published as: HU194513B; DE3624695A1; HUT41075A; GB8618535D0; FR2585733A1

Abstract

For the electrolytic treatment of profiled workpieces (3) the electrolytic treatment is carried out by means of an electrode (4) which was previously used as a spark-machining electrode for the manufacture of the workpiece or the tool thereof. Since the workpiece and the electrode conform in shape, a uniform spacing is attained which results in a uniform electric field strength in the bath (2) and the electrolytic treatment is therefore uniform over the whole surface of the workpiece. <IMAGE>

Description

SPECIFICATION Arrangement for electrolytic treatment of profiled workpieces The invention relates to an arrangement for the electrolytic treatment of profiled workpieces.

In the present specification under the term "electrolytic treatment" the deposition of galvanic layers, the electrolytic polishing, the passivation and in some cases the electrolytic dissolution of the applied layers should be understood.

The technique of electrolytic treatment has already been known for several decades and conventional electrolyzing arrangements comprise generally the following main parts: and electrolyzing tank or vessel of suitable size, the electrolyte comprised therein, the workpiece immersed in the electrolyte, a D.C.

source with a pole connected either directly or through a support to the workpiece, and an electrode being in connection with the other pole of the D.C. supply. In addition to these main parts temperature regulators are often used to keep the bath temperature at a convenient value, current and/or voltage stabilizers and regulators are used to adjust and/or stabilize the electrolytic current or voltage, and aspirators are also used to conduct away various vapor substances produced during the electrolysis.

Under the term "profiled workpieces" such objects are understood which have hollow or zigzag surface profile due to which the electrical field strength established during the electrolysis between the workpiece and the electrode varies considerably along the surface regarding its value and/or direction. Such profiled workpieces are typically different parts of metal spectacles' frames e.g. the nose-support, the arm-fixation strap and the spectacle frame itself. In electrolytic treatment of profiled pieces the difficulties often arise due to the fact that at partially covered or hardly accessible surface areas owing to the electrical shielding effect of closely located borders of the hollows the field strength will be at minimum, thus low deposition rates are obtained.

Thus the required deposition thickness can only be achieved if on the other/not shielded/ areas the layer is much thicker than required.

This results in an increase in time, power and material consumption.

This phenomenon appears as a problem not only in case of electrolytic deposition but also of electrolytic polishing. In the production of metal spectacle frames the surface brightness of the tools used for the manufacture should exceed a predetermined high value, and this brightness can be obtained conveniently by means of electrolytic polishing the tools, The mechanical polishing of surface areas defined in cavities, internal edges and corners imposes high technical problems. Similarly, the electrolytic polishing of such areas can not be solved satisfactorily due to the limited deepscattering properties of conventional electrolytic arrangements, or alternatively such polishing processes require very long times of treatment.

The object of the invention is to provide an electrolytic arrangement which can provide for a uniform electrolytic treatment for profiled workpieces without requiring any excess care and which does not impose any special difficulty during its use.

The invention is based on the recognition that profiled workpieces, especially tools are often manufactured by means of spark machining technique. During this technique a spark machining electrode is used which has a surface conforming to the negative of the required surface profile of the workpiece and the size of the electrode is smaller than that of the workpiece by the amount of the spark gap used in the spark machining process. The electrode is made generally of copper or a copper alloy, and following the spark machining process the electrode is not used anymore or if several workpieces are made, the electrode is disposed off after having reached a predetermined erosion.If, according to the invention the otherwise unusable spark machining electrode is used as an electrode during the electrolytic treatment of a workpiece made previously thereby which is immersed in the electrolytic bath, then a uniform spacing can be obtained between conforming surfaces of the electrode and of the workpiece, and the electrical field strength between the workpiece and the electrode will be uniform which results in an evenly distributed electrolysis on the whole surface of the profiled workpiece.

It is preferable if the spacing between the profiled workpieces and the conforming electrode is smaller than 1 mm and this spacing should preferably be in the range of 0.1 mm.

It is also preferable if the electrolyte present in this spacing is intensively re-circulated by means of a pump and if it is filtered. The circulation of the electrolyte improves the movements of the ions, it prevents any unwanted deposition, provides a sufficient cooling for the electrolyte and assists in obtaining a uniform electrolysis.

According to the invention the otherwise useless and generally discarded used spark machining electrode will play again an important role in the manufacturing process and this novel use substantially improves both the quality and the efficiency of the electrolytic treatment.

The arrangement according to the invention will now be described in connection with a preferable embodiment thereof, in which reference will be made to the accompanying drawings. In the drawing Figure 1 shows the schematical layout of the arrangement according to the invention.

The arrangement shown in the drawing comprises tank 1, electrolytic bath 2 in it, workpiece 3, electrode 4 placed above the workpiece 3, D.C. supply 5 connected to the workpiece 3 and the electrode 4, pump 6 for circulating the electrolyte forming the bath and positioning unit 7 for adjusting the accurate position of the electrode.

On the upper surface of the workpiece 3, there is provided a first hollow 8 of greater size and a blind hole 9 terminating in it. The task of the manufacturing process is to provide a uniform electrolytic treatment of the workpiece 3. The workpiece 3 /or the tool used for the manufacture of the workpiece 3/ has been manufactured previously by spark machining technique. The electrode used during the spark machining process is the same as the electrode 4 used for the electrolysis.

The positioning unit 7 provides for a uniform spacing between the surface of the workpiece 3 and the electrode 4. In the electrolytic treatment a current is established by means of the DC source 5 between the workpiece 3 and the electrode with a current density required for the electrolytic treatment and the electrolyte is intensively circulated during the treatment.The effect of the electrolytic treatment will be uniform on the whole surface of the workpiece 3, and in the surface areas that were electrolytically hardly treatable by means of conventional technique, e.g. on the surface of the blind hole 9 a layer of sufficient quality is formed or in case of electrolytic polishing the surface brightness will reach the required value, and during this process the material consumption to the process will be at optimum and the time required for the treatment will be substantially shorter than in case of conventional techniques. These favorable properties are obtained owing to the fact that in the arrangement used according to the invention the deep-scattering feature of the electrolytic treatment is substantially improved.

The arrangement according to the invention can well be used for polishing tools. If the workpiece 3 represents a tool of a tool steel made by spark machining by means of the electrode 4, then the polishing of this tool can be carried out by means of the arrangement shown in the drawing. Such an electrolytic polishing method is described e.g. in the Hungarian patent No: 178.066 which method can well be used in the present case. The electrode positioning unit 7 will be used for adjusting a spacing of about 0.1 mm or still smaller between the electrode 4 and the workpiece 3, and the pump 6 is used for circulating the electrolyte at least so intensively that the electrolyte in the spacing is completely changed ten times in every minute.

A filter means is used for removing particles detached from the workpiece during the electrolytic treatment, thus in spite of the small spacing the establishment of a short-circuit between the workpiece 3 and the electrode is safely prevented. The current density is typically between 2;5 and 10 A/dm2. As a result of the electrolytic polishing a uniform surface brightness is obtained on the whole surface of the workpiece 3, therefore a subsequent mechanical polishing is not required.

The use of the arrangement according to the invention cannot be limited to any actual type of electrolytic treatment, and this use can be preferable in all kinds of electrolytic treatment of profiled workpieces.

Claims

1. An arrangement for the electrolytic treatment of profiled workpieces, comprising a tank, an electrolytic bath in the tank, a workpiece immersed in the bath, an electrode also immersed in the bath, and a direct current source coupled to the workpiece and to the electrode, characterized in that said electrode /4/ is the one used as a spark machining electrode during the manufacture of the workpiece or the tool thereof by means of spark machining technique having a shape conforming negatively to that of the workpiece /3/ and a substantially uniform spacing is defined between conforming surfaces of the electrode /4/ and the workpiece /3/.

2. The arrangement as claimed in claim 1, characterized in that the electrode /4/ is coupled to a positioning unit /7/ for adjusting said spacing, and said spacing being smaller than 1 mm.

3. The arrangement as claimed in claim 1, characterized by comprising a pump /6/ for circulating the electrolyte in a closed loop and a filter arranged in said loop.

4. An arrangement for the electrolytic treatment of profiled workpieces, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.