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Inspection knowledge of enameled wire
- Mar 05, 2018 -

After the product is manufactured, its appearance, size and performance are in conformity with the technical standards of the product and the requirements of the technical agreement of the user, which must be judged by inspection.

After measurement and test, compared with the technical standard of the product or the technical agreement of the user, it is qualified to meet the requirements; otherwise, it is not qualified.

Through the inspection, the stability of the product quality and the rationality of the material process can be reflected, so the quality inspection has the function of checking, preventing and identifying.

The contents of enameled wire inspection include: appearance, size inspection and performance test.

The performance includes mechanical properties, chemical properties, thermal properties and electrical properties.

Now we mainly explain the appearance and size.


The surface of the


(look) should be smooth, colour and lustre is uniform, no particles, no oxidation, hair, face, black spots, Yin and Yang to take off the lacquer, affect the performance of the defects such as wiring should level off tightly around online tray, not on, and freely.

There are many factors affecting the surface, which are related to raw materials, equipment, technology and environment.


Dimension 2.1 the size of the enamelled round line includes: dimension (outer diameter)D, conductor diameter D, conductor deviation, D, conductor's inroundness f, paint film thickness t.


2.1.1 external diameter is the diameter measured after coating a layer of insulating paint.


2.1.2 the diameter of the conductor is the diameter of the wire after the insulation layer is removed.


2.1.3 conductor deviation is the difference between the measured value of the guide diameter and the nominal value.


2.1.4 the inroundness (f) is the maximum difference between the maximum and minimum readings measured in each section of the guide.


2.2 measurement method


2.2.1 measuring tools: micrometer micrometer, accuracy O.002mm.


When the enameled round line d<0.100mm, the measuring force is 0.1 ~ 1.0N, and d is greater than 0.100mm, the measuring force is 1 ~ 8N.

Paint flat wire measuring force 4-8n.


2.2.2 diameter


2.2.2.1(round line) when the conductor nominal diameter d is less than or equal to 0.200mm, three measurements are taken at each of the three meters of each other, and three measured values are recorded, and the average value is taken as the outer diameter.


2.2.2.2 when the conductor nominal diameter is d>0.200mm, the two positions of 1m are measured, and the average circumference of each position is measured 3 times, and 6 measured values are recorded, and the average value is taken as the outer diameter.


2.2.2.3(flat line) each measuring width and narrow edge size of 100mm3 is one time, and the average value of three measurements is taken as the contour size of wide and narrow edges.


2.2.3 conductor size.


2.2.3.1 (circle line) when the conductor nominal diameter d 0.200 mm or less, in the 1 m away from the three location in not damage any methods to remove the insulation of the conductor measure one conductor diameter: take the average value as the conductor diameter.


2.2.3.2 conductor when nominal diameter d > o. 200 mm, with no damage to the conductor any methods to remove insulation, measured along the conductor circle divide three position, take the average value of three measurements as the conductor diameter.


2.2.2.3 (flat wire) away from the 10 omm3 position, with no damage to any method to remove the insulation conductors, measured and narrow and wide size 1, take the average value of three measurements as wide and narrow while conductor size.


2.3 calculation


2.3.1 deviation =d measured -d nominal.


2.3.2 f = maximum difference of any diameter reading measured on each section of the conductor.


2.3.3 t = D - D measurement


For example 1: there is a set of enamel-insulated wire of qz-2/130 0.71Omm, which is measured as follows.


Outer diameter :0.780, 0.778, 0.781, 0.776, 0.779 and 0.779;

Conductor diameter: 0.706, 0.709, 0.712.

The diameter of the conductor, the diameter of the conductor, the deviation, the f value, the thickness of the paint film, and the determination of whether it is qualified.


Solution: D = (0.780 + 0.778 + 0.781 + 0.778 + 0.780 + 0.779) / 6 = 0.779 mm, D = (0.706 + 0.706 + 0.712) / 3 = 0.709 mm, the measured deviation = D - D nominal = 0.709-0.709 = 0.710 mm, f = 0.712 0.706 = 0.006, t = D - D = 0.779-0.709 = 0.709 mm measured


After measurement, the specification of enameled wire meets the standard requirements.


2.3.4 flat wire: add thick paint film 0.11<& less than 0.16mm, ordinary paint film 0.06 is less than or equal to 0.11mm.


When the outside diameter of AB does not exceed Amax and Bmax, the paint film thickness is allowed to exceed & Max, nominal size a(b) deviation a(b) is less than or equal to 3.155 or + 0.030, 3.155<><>.


For example 2: existing flat line QZYB-2/180 2.36 x 6.30mm, measured size A: 2.478, 2.471, 2.469;

A: 2.341, 2.340, 2.340;

B: 6.450, 6.448, 6.448;

B: 6.260, 6.258, 6.259.

The film thickness, outer diameter, conductor, and determine whether qualified.


Solution: A = (2.478 + 2.478 + 2.469) / 3 = 2.473;

B = (6.450 + 6.450 + 6.448) / 3 = 6.449;


A = (2.341 + 2.341 + 2.340) / 3 = 2.340;

B = (6.260 + 6.258 + 6.259) / 3 = 6.259


Paint film thickness: a side is 2.473-2.340=0.133mm;

B side is 6.499-6.259=0.190mm.


Conductor size unqualified causes except the semi-finished products uneven conductors have hidden defects or specifications, pay-off tension mainly paint process, each part felt firmness improper adjustment, or pay-off and roller rotation is not flexible, the line is fine.


The main insulation size of the film is not suitable for the wool felt elastic adjustment, or improper fitting and die.

In addition, the process speed, paint viscosity, solid content and other changes will also affect the film thickness.


Performance 3.1 mechanical properties: including elongation, springback Angle, softness and adhesion, paint, tensile strength, etc.


3.1.1 the elongation reflects the plastic degeneration of the material, which is used to assess the ductility of enameled wire.


3.1.2 rebound Angle, softness reflects the elastic deformation of the material, and it is used to assess the softness of enameled wire.


The strength of elongation, springback Angle and softness reflect the degree of annealing of copper and enameled wire.

The main factors affecting the elongation and springback Angle of enameled wire are (1) wire quality;

(2) influence of external forces;

(3) degree of annealing.


3.1.3 the toughness of the paint film includes winding and stretching, which is the allowable tensile deformation of the film with the tensile deformation of the conductor without breaking.


3.1.4 the adhesion of the paint film includes quick pull and peeling, and the adhesion ability of the paint film to the conductor is mainly examined.


3.1.5 scratch test of paint film, reflecting the strength of the paint film against mechanical scratches.


3.2 heat resistance: including thermal shock and softening breakdown test.


3.2.1 the thermal shock of enameled wire is the bearing capacity of the coating film under mechanical stress.


Factors influencing thermal shock: paint, copper wire, coating process.


3.2.3 the softening breakdown performance of the enameled wire is the ability to measure the thermal deformation under the action of mechanical force, i.e. the ability of the paint film under pressure to plasticize and become soft under high temperature.

The resistance of the enamelled film to the heat resistance of the film is determined by the size of the molecular structure of the paint film and its intermolecular chain.


3.3 electrical performance includes breakdown voltage, film continuity and dc resistance test.


3.3.1 breakdown voltage refers to the capacity of the voltage load borne by the paint film.

Main factors influencing breakdown voltage :(1) film thickness;

(2) lacquer film roundness;

(3) degree of cure;

(4) external impurities in the paint film.


3.3.2 continuous test of paint film is also known as pinhole test, and its main influencing factors are :(1) raw materials;

(2) operation process;

(3) equipment.


3.3.3 dc resistance refers to the resistance measured in unit length.

Its main influencing factors :(1) degree of annealing;

(2) coating equipment.


3.4 chemical resistance including solvent resistance and direct weldability.


3.4.1 solvent resistance. Generally, the enameled wire should be impregnated after winding the coil, and the solvent in the impregnating varnish has different degrees of swelling effect on the paint film, which is even worse at higher temperatures.

The chemical resistance of enamelled film is mainly determined by the properties of the film itself. Under certain conditions, the coating process has certain influence on the solvent resistance of enameled wire.


3.4.2 direct welding performance of enameled wire, reflecting the ability of enameled wire to solder solder in the process of not removing paint film.

The main factors that affect the direct weldability are: (1) : the influence of the process, (2) the influence of the paint.