>
>
2023-05-05
Recently, data/signal/instrumentation cables have been widely used in various industries. 2 Key indicators of cable transmission features are Impendence (Z0）and Return Loss (RL). As we known, the uniformity of whole cable length and full band is the “touchstone” for evaluating the performances of cable transmission. Impedance directly decides the changes of Return Loss, when impendence is uniform, the reflected energy of signal will be less, the dB value of Return Loss will be high, therefore, the cable transmission quality will be better.
During the cable manufacturing procedure, the key point is how to keep the impendence uniformity. Copper conductor quality is essential to guarantee the uniformity of cable construction, though it is not easy to control during production. We need to keep center distance between two conductors of each pair unchanged, and keep single wire outer diameter stable. However, every factor changes periodically when production, we have to strictly control main factors in technology, in order to get all indicators passed.
The copper conductor requires uniform diameter and high surface finish. The extruding mould will guarantee the concentricity of insulation diameter, which needs to be more than 96%. The position of the incoming line of the equipment, the nose and the traction should be kept at the same level and in the same straight line. Besides, an extra device should be set up just before the copper conductor entering, in order to reduce the fluctuation of the wire. All above measures having been taken, the capacity and Impendence will be stable, the circuit impendence will be relatively uniform.
inline inspection and precise electrical transmission are the necessary means for keeping impendence uniformity, enhancing return loss and reducing crosstalk mechanism.in the producing process, the diameter quality of the final single insulated wire, especially the variation of its outer diameter size and the deformation of its geometric shape, will affect the capacitance in water. In the same time, the quality of the core wire will affect the main parameters, impendence, return loss and the quality of the near and far end index of the wire.
The adhesion between the copper conductor and the insulation layer is mainly reflected in the bonding between the insulation layer and the copper wire. The key of bonding between insulation layer and copper conductor is the preheating temperature of copper conductor. Insufficient preheating, adhesion decline, or overheating will directly influence the stability of the outlook of the insulation layer. Before the next process，due to the single wire bending during twisting, insulation layer and conductor wire will separate caused by adhesion. The center distance of the two wires will change periodically, which will lead to irregular periodic changes of the twin-core stranded structure, affect the parameters of the high frequency band, and worsen the return loss of the structure. The preheating temperature is generally controlled in the range of 120 degrees to 130 degrees.
the Variation of conductor quantity, characteristic, will directly affect the conductivity and elongation. Especially, the elongation is closely related to the stability of the conductor diameter. Conductor diameter and shape will affect the Impendence and return loss, meanwhile, conductivity will be related to conductor resistance. 99.99% oxygen free copper rod is recommendable.
As we know insulation uniformity will directly affect quality of Impendence and return loss, then How to control the quality of insulation layer?
the amount of the impurity will severely influence the attenuation of cable signal transmission. Therefore, any pigment added to insulation is impurity, the pigment quantity is just enough to identify.
6. Concentricity control of the insulation layer
The concentricity control will strongly affect the Impendence and return loss, which requires the allowance of conductor diameter within ±0.002 mm. Meanwhile, Insulation outside diameter deviation is controlled within ± 0.003mm, concentricity is controlled above 96%. And the surface should be smooth and round, otherwise, the single wire Impendence value will exceed the requirement after twisting. When the concentricity is more than 98%, no back torsion is necessary, and we can get a small fluctuated Impendence.
7. Production line speed control
In the production process of data, signal, instrument cable, line speed is quite important, when line speed is too high, precision is difficult to control. Generally controlled at 800m~850m/min. If the wire speed is too high, the core wire is not sufficiently cooled, and the yield stress in the insulation layer cannot be eliminated naturally, it will affect the change of the distance between the two cores. At the same time, because the core wire is not sufficiently cooled, the concentricity is difficult to ensure. If the wire speed is too high, the quality of the insulated wire will be damaged
8. Twisted pair and cable
In the process of production, it is not easy for twisted pair and cable core to achieve structural stability, among which the key is precise skein pitch and stable cable core diameter.
8.1 High precision pitch is required. The accuracy and stability of stranded pitch will directly affect the crosstalk index of cable. Evaluation method of stranded pitch: within 50 times of the equipment pitch, the equipment pitch and the actual pitch of stranded wire after the calculation error should be strictly controlled within the range of 0.5%~1.5%.
8.2 To ensure the high-precision hinge pitch, the pair should make the two pay-off tension to maintain the same, uniform, two cores stranded length is the same, absolutely do not allow a single wire stranded on another single wire.
8.3 During the twisting process, the bending of single wire and twisted pair wire should be minimized, and all guide wheels should not be less than 100 mm in diameter. If the bending is too large, the insulation layer and the copper core will peel off, resulting in irregular periodic changes in the distance between the wires, which affects the stability of the structure. At the same time in the process of stranding can not be stopped, because the stop and boot will affect the stability of pitch.
8.4 The winding tension of the stranding machine should be kept uniform and constant. The variation of winding tension will lead to the instability of pitch. The control of tension and bending radius is very important, which affects the stability of cable core structure, and has a serious impact on high frequency, mainly due to the uniformity of impedance and deterioration of return loss。
9. Sheath
Sheath is the outer skin of the cable to protect it from damage in use. Sheath can fix the cable, prevent wires from moving, which leads to cable structure destroy and parameters changing. Sheath tightness has great influence on the whole cable structure, if too tight, capacitance will increase which will make impendence unstable, if too loose, which will make structure unstable, worsen the return loss. The cable core will flip in the sheath, which will change the pitch and greatly affect the transmission parameters.
Dingzun cable has rich experience in producing data, signal, instrument cable, we share our summary to cable buyer and cable factory, to improve the quality during the manufacturing process.
Contact Us at Any Time
