CN111455417B - An electroforming core mold and a method for manufacturing a metal capillary using the same - Google Patents

Abstract

The invention relates to the field of electrochemical machining, and provides an electroforming mandrel and a method for manufacturing a metal capillary tube by using the electroforming mandrel. The problem that the existing electroforming capillary is difficult to demold is solved by carrying out sectional treatment on the electroforming mandrel. The mandrel is divided into five parts of a front end section, a groove section, a clamping section, an electroforming section and a rear end section, and an electric insulating layer is covered except the electroforming section. When in use, the mandrel is still operated according to the traditional electroforming process, and only the electroformed metal layer is covered on the electroformed section due to the presence of the electrically insulating layer. After electroforming, the mandrel is sheared at the groove sections of the mandrel, and the mandrel is split into individual section group units. The traditional long core mould integral demoulding can be changed into the short core mould sectional demoulding through sectional treatment, and because the special clamping section for demoulding is arranged, the pulling force is easier to be applied to the core mould, and the breakage of the core mould is easier to control, so that the demoulding difficulty is reduced. The invention can simplify demoulding operation and improve yield while ensuring the quality of the electroformed capillary tube.

Description

Electroforming mandrel and method for manufacturing metal capillary tube by using electroforming mandrel

Technical Field

The invention belongs to the technical field of electrochemical machining, and particularly relates to an electroforming mandrel and a method for manufacturing a capillary tube by using the electroforming mandrel.

Background

Metal capillaries with an inner diameter of several hundred micrometers or less are of great importance in many industries and fields, such as use as chromatography tubes, automated meter signal tubes, probe tubes for electronic testing, fiber-optic connectors, injection needles, and the like. At present, the manufacturing of the metal capillary tube mostly adopts methods such as drawing, stamping forming, hydrostatic extrusion, electroforming and the like. Although the modes of drawing, stamping forming, hydrostatic extrusion and the like have various advantages, common problems are faced with (1) low thickness uniformity and low precision, (2) no capillary tube with very small inner diameter can be obtained, and (3) no capillary tube with small inner diameter and large wall thickness can be obtained under the limitation of forming principle. However, electroforming is particularly advantageous in these respects. Thus, the electroforming process is the main method for manufacturing high-performance and high-precision metal capillaries.

Electroforming is a process of preparing a product by utilizing a metal ion cathode electrodeposition principle to deposit metal, alloy or composite material with a certain thickness on a master mould and separating the metal, alloy or composite material from the master mould, and is a precise special processing technology. The electroforming has the characteristics of high replication precision, pure material, easy performance regulation and control and the like, and is particularly suitable for manufacturing metal capillaries with large wall thickness, high precision, high surface quality and superfine inner diameter. An electroforming method for manufacturing a metal capillary is proposed in patent number 200480042540.0, for example. After a long capillary tube blank is prepared based on one-time electroforming of a long linear core die, cutting and segmenting are carried out, so that the capillary tube with the final required length is obtained. This method is extremely difficult to demold despite the low cost of the mandrel. To some extent, the capillary tube blank is easy to prepare by electroforming, and the biggest difficulty is how to take the mandrel out of the metal blank tube after electroforming, namely demoulding. Demolding is the biggest technical challenge of electroforming metal capillaries. In this regard, some demolding solutions are proposed in patent nos. 201680019698.9 and 201210095159.7, but the effect is still not ideal. The main reasons are (1) the binding force between the metal capillary tube blank and the linear core mould is in linear increasing relation with the length of the metal capillary tube blank and the linear core mould, the linear core mould is fine and is very easy to stretch and break, so that the whole demoulding difficulty is high and the success rate is very low by directly stretching through mechanical force, and (2) the chemical dissolution method cannot be realized, because corrosive liquid cannot smoothly enter the inner diameter depth of the capillary tube to continuously dissolve and remove core mould metal by overcoming the surface tension. The feasibility is not great if the mold is released by a thermal expansion and cold contraction method by utilizing the difference of the thermal expansion coefficients between metals. The reason is that the gap between the electroformed metal and the core mold metal is difficult to be large due to expansion with heat and contraction with cold, so that the demolding can be smoothly performed, and particularly the demolding of the long metal capillary is performed. In addition, the flexible nonmetal or metal wire and transition metal layer combination is adopted as an electroforming mandrel, and the inner diameter precision of the capillary tube cannot be ensured although the electroforming mandrel is easy to stretch and demould. Therefore, the invention provides a new electroforming mandrel and a method for manufacturing a metal capillary tube by electroforming the mandrel, so as to achieve the purposes of easy demoulding and high product yield.

Disclosure of Invention

The invention provides a mandrel for electroforming metal capillary tubes, which aims at overcoming the defects of a mandrel and a demoulding process used for manufacturing capillary tubes by electroforming in the prior art, and realizes mass, high-efficiency and high-yield production of metal capillary tubes by adopting the mandrel.

In order to achieve the above purpose, the technical scheme of the invention is as follows.

An electroforming mandrel comprises a metal wire body and an electric insulating layer, wherein the wire body is provided with a clamping section, a groove section, an electroforming section, a front end section and a rear end section, the groove section, the clamping section and the electroforming section are arranged on the wire body in a section group to form a plurality of section group units, each section in the section group unit comprises 2 groove sections, 2 clamping sections and 1 electroforming section, the sections in the section group unit are arranged in sequence of the groove section, the clamping section, the electroforming section, the clamping section and the groove section, the front end section and the rear end section are respectively positioned at two ends of the wire body, the outer surfaces of the front end section, the rear end section, the groove section and the clamping section are all covered with the electric insulating layer, the outer surface of the middle part of the electroforming section is covered with the electric insulating layer, the length of the covering part is 4/5 of the length of the section, the cross section of the wire body is circular, the diameter Da of the groove section is 1.5-2 times the diameter Dz of the electroforming section, the diameter Dj of the clamping section is 2-3 times the diameter Dz of the electroforming section, and the diameters Dj of the clamping section are equal.

The silk body of mandrel is SUS304 stainless steel. The material has the characteristics of corrosion resistance, good toughness, weaker binding force of electroformed metal and the like, and is favorable for stretching and demoulding.

The length Lj of the clamping section of the core mold is 10-20 mm. The clamping section is arranged to reserve the necessary length for clamping the clamp.

The length La of the groove section of the core mold is 1-2 mm. The point is the division of the segment group unit.

The length Lq of the front end section of the core mold is equal to the length Lh of the rear end section of the core mold, and the length Lq is 20-30 mm. The arrangement of the front end section and the rear end section ensures that the core mold is clamped and fixed conveniently during electroforming.

The diameter Dz of the electroforming section of the mandrel is 50-1000 mu m.

The number of the segment group units of the mandrel is more than 2.

The material of the electric insulating layer of the mandrel is acid and alkali corrosion resistant, and the thickness of the electric insulating layer is 10 nm-5 mu m. The electrically insulating layer is provided to prevent electroforming of a metal layer on the outer surfaces (non-electroformed metal areas) of the front end section, the rear end section, the groove section, and the grip section so that a desired capillary shape can be obtained. The acid and alkali corrosion resistant material is used to prevent the electric insulating layer from reacting with the electroforming solution during the electroforming process, polluting the electroforming solution and causing electroforming failure.

A method for manufacturing a metal capillary tube is characterized by comprising the following steps:

(1) After the mandrel is pretreated according to the electroforming process specification, the mandrel is placed into an electroforming solution tank;

(2) Electroforming a metal layer to the mandrel by taking the mandrel as a cathode;

(3) Stopping electroforming when the outer diameter of the metal layer at the electroforming section meets the requirement, forming a capillary tube blank by the metal layer, taking out a mandrel with the capillary tube blank from the electroforming bath solution, cleaning and drying;

(4) Cutting off each groove section of the core mould, and dividing the core mould into a plurality of section group units;

(5) The clamping section is taken as a clamping section, and the section group unit is precisely stretched until the electroforming section in the section group unit is broken;

(6) Taking out the stretched electroformed segment from the capillary tube blank;

(7) Cutting off and finishing the two ends of the capillary tube blank to finally obtain a metal capillary tube;

(8) Repeating the steps (4) - (7), and processing other section group units until all section group units are processed.

Compared with the prior art, the invention has the main advantages of greatly simplifying demoulding operation and having high yield while ensuring the quality of the electroformed capillary tube. The novel concept based on 'sectional electroforming and sectional demolding' replaces the traditional method of 'first integral electroforming and then cutting and segmenting' in the field, so that demolding becomes very easy, and the yield is greatly improved.

Drawings

Fig. 1 is a schematic diagram of a mandrel segment set unit.

Fig. 2 is a schematic diagram of a mandrel (2 segment set unit).

Fig. 3 is a schematic diagram of electroforming of a mandrel.

Fig. 4 is a schematic diagram after electroforming of segment group units.

Fig. 5 is a drawing schematic drawing.

Fig. 6 is a schematic view of a capillary tube blank.

Fig. 7 is a schematic drawing of cutting the capillary tube blank.

Fig. 8 is a schematic diagram of a capillary tube.

The reference numbers and names in the figure are 1, a metal wire body, 2, an electric insulating layer, 3, a clamping section, 4, a groove section, 5, an electroforming section, 6, a section group unit, 7, a front end section, 8, a rear end section, 9, an electroforming layer, 10, a clamp, 11, a capillary tube blank, 12, a capillary, 13, a capillary tube blank end, b, an electric insulating layer thickness, lj, a clamping section length, la, a groove section length, lq, a front end section length, lh, a rear end section length, dz, an electroforming section diameter, dj, a clamping section diameter, da, a groove section diameter, dq, a front end section diameter, dh, a rear end section diameter, D and a capillary diameter.

Detailed Description

The patent of the invention is further described below with reference to the accompanying drawings.

The mandrel is shown in fig. 1 and 2, the filament body is provided with a clamping section 3, a groove section 4, an electroforming section 5, a front end section 7 and a rear end section 8, the groove section 4, the clamping section 3 and the electroforming section 5 are arranged on the filament body 1 in a section group to form a plurality of section group units 6, each section in the section group units comprises 2 groove sections 4, 2 clamping sections 3 and 1 electroforming section 5, the sections in the section group units are arranged in the sequence of the groove section 4, the clamping section 3, the electroforming section 5, the clamping section 3 and the groove section 4, the front end section 7 and the rear end section 8 are respectively positioned at two ends of the filament body 1, the outer surfaces of the front end section 7, the rear end section 8, the groove section 4 and the clamping section 3 are covered with an electric insulation layer 2, the material of the electric insulation layer 2 is selected from corrosion-resistant insulation paint, the outer surface of the middle part of the section 5 is covered with the electric insulation layer 2, the length of the covered part is 4/5 of the length of the electroforming section 5, the section 1 is circular, the cross section shape of the groove section 4 is the diameter Da of the diameter of the electroforming section 5 is equal to the diameter Dj of the clamping section 3.5, and the diameter of the clamping section 3.5 is equal to the diameter of the front end section 4 is equal to the diameter of the clamping section 3.7.

The main steps of electroforming the metal capillary tube based on the mandrel are as follows:

(1) Selecting a mandrel composed of 2 segment group units 6, wherein the length Lj of a clamping segment 3 is 15mm, the length La of a groove segment 4 is 2mm, the lengths Lq and Lh of a front end segment 7 and a rear end segment 8 are 25mm, the diameter Dz of an electroformed segment 5 is 150 mu m, the material of an electric insulating layer 2 is corrosion-resistant insulating paint, the thickness b is 5 mu m, the length of a covered part of the electric insulating layer 2 is 4/5 of the length of the electroformed segment 5, the diameter Da of the groove segment 4 is 1.5 times the diameter Dz of the electroformed segment 5, and the diameter Dj of the clamping segment 3 is 2.5 times the diameter Dz of the electroformed segment 5;

(2) Performing surface finishing, oil removal and rust removal treatment on the core mold;

(3) The treated core mould is weakly etched in 120mL/L sulfuric acid solution at room temperature for 4 minutes, then is passivated in 20g/L potassium dichromate solution at room temperature for 15 minutes, and then is taken out, washed out by flowing cold water and dried;

(4) Putting the dried mandrel into an electroforming device to serve as a cathode, wherein the anode material is electrolytic nickel;

(5) The prepared electroforming solution is added into an electroforming device, and the electroforming solution is a mixed solution of nickel sulfamate (300 g/L), nickel chloride (10 g/L) and boric acid (35 g/L). The electroforming was carried out using a current density of 1A/dm ², during which the solution temperature was maintained at 55℃and the pH was 4, and the solution was stirred by mechanical stirring for 6 hours. The thickness of the capillary tube blank 11 obtained thereafter was 55. Mu.m. After electroforming is completed, taking out the core mould with the capillary tube blank 11, washing the core mould with clear water, and drying the core mould;

(6) Cutting off each groove section 4 of the mandrel to obtain two section group units 6 with electroformed layers 9;

(7) Clamping the clamping section 3 by using a clamp 10 of a precision electronic tension machine, and stretching the section group unit 6 by a force increment of 1N until the electroformed section 5 is broken;

(8) Taking out the stretch broken core die to obtain a capillary tube blank 11 separated from the electroformed segment 5;

(9) Cutting off the two ends of the capillary tube blank 11, and polishing and finishing the cut-off parts to obtain a metal capillary tube 12;

(10) Repeating the steps (7) - (9), and processing the other section of units to obtain a second metal capillary 12.

Claims (8)

1. A method for manufacturing a metal capillary, characterized in that it comprises the following steps: (1) After pre-treating the core mold according to the electroforming process specifications, place the core mold in the electroforming solution tank; (2) electroforming a metal layer (9) onto the core mold using the core mold as a cathode; (3) When the outer diameter of the metal layer (9) at the electroforming section (5) reaches the required value, the electroforming is stopped. At this time, the metal layer (9) forms a capillary tube blank (11). The core mold with the capillary tube blank (11) is taken out from the electroforming tank liquid, cleaned and dried; (4) cutting off each groove segment (4) of the core mold to divide the core mold into a plurality of segment group units (6); (5) Using the clamping section (3) as the clamping section, the segment group unit (6) is precisely stretched until the electroformed segment in the segment group unit (6) is broken; (6) removing the broken electroformed section (5) from the capillary tube blank (11); (7) Cutting and polishing the two ends of the capillary tube blank (11) to finally obtain a metal capillary tube (12); (8) Repeat steps (4) to (7) to process other segment group units (6) until all segment group units (6) are processed; The core mold is an electroforming core mold; The electroforming core mold is characterized in that: it comprises a metal wire (1) and an electrical insulating layer (2); the wire is provided with a clamping section (3), a groove section (4), an electroforming section (5), a front end section (7) and a rear end section (8); the groove section (4), the clamping section (3) and the electroforming section (5) are arranged in groups on the wire (1) to form a plurality of section group units (6); the section group unit (6) comprises two groove sections (4), two clamping sections (3) and one electroforming section (5); the sections in the section group unit are arranged in the order of the groove section (4), the clamping section (3), the electroforming section (5), the clamping section (3) and the groove section (4); the front end section (7) and rear end section (8) are respectively located at the two ends of the filament (1); the outer surfaces of the front end section (7), the rear end section (8), the groove section (4), and the clamping section (3) are all covered with an electrical insulation layer (2); the middle outer surface of the electroformed section (5) is covered with an electrical insulation layer (2), and the length of the covered portion is 4/5 of the length of the electroformed section (5); the cross-sectional shape of the filament (1) is circular; the diameter d _concave of the groove section (4) is 1.5 to 2 times the diameter d _cast of the electroformed section (5); the diameter d _clamp of the clamping section (3) is 2 to 3 times the diameter d _cast of the electroformed section (5); the diameters of the clamping section (3), the front end section (7) and the rear end section (8) are equal. 2. A method for manufacturing a metal capillary according to claim 1, characterized in that: the material of the filament (1) is SUS304 stainless steel. 3. A method for manufacturing a metal capillary according to claim 1, characterized in that the _length L of the clamping section (3) is 10-20 mm. 4. A method for manufacturing a metal capillary according to claim 1, characterized in that the length L of the groove section (4) _is 1-2 mm. 5. A method for manufacturing a metal capillary according to claim 1, characterized in that the length _Lfront of the front end section (7) and the length _Lback of the rear end section (8) are equal, both of which are 20-30 mm. 6. A method for manufacturing a metal capillary according to claim 1, characterized in that the diameter _dcast of the electroformed segment is 50-1000 μm. 7. A method for manufacturing a metal capillary according to claim 1, characterized in that the number of the segment group units (6) is greater than 2. 8. A method for manufacturing a metal capillary according to claim 1, characterized in that: the material of the electrical insulation layer (2) is a material resistant to acid and alkali corrosion, and its thickness is 10nm~5μm.