Common Problems and Solutions in Cable Production
1.Unqualified crosslinking degree(thermal extension)
If the crosslinking degree is not up to the standard,the thermal-mechanical properties of the cable are not up to standard and can not meet the requirement of working temperature of 90℃.
Reasons for unqualified crosslinking degree are as follows:first,unqualified formulation and inappropriate type and proportion of formulations should be adjusted to solve the problem;second,improper vulcanization process,such as low air pressure,fast line speed,high cooling water level,etc.The solution is to first find out what is the cause,which may be one or several reasons.At the same time,it exists and is excluded according to the reasons.
2.Unqualified structure and appearance
(1)The thinnest point of insulating layer thickness is lower than the minimum value specified in the standard,or the average thickness is lower than the nominal value.The unqualified insulation thickness is due to the fast wire speed,small rubber output of extruder and improper die selection.
The solution is to reduce the linear speed or increase the speed of the extruder and adjust the size of the die.
The cause of eccentricity is that the suspension control has changed after the die has not been adjusted or raised.The solution is to control the suspension as stable as possible during the driving process.
The bamboo shape outside the cable is caused by the instability of the traction speed caused by the electrical and mechanical system.The second reason is that the core is too small or the outer diameter of the conductor is not uniform.
The elimination method is to inspect the mechanical and electrical systems and remove the faults.Properly adjust the size of the core,control the outer diameter of suburban counties as evenly as possible,and the strand can be used when it exceeds the technological requirements.
(1)The cable meets the upper and lower walls or foreign bodies in the vulcanized pipe.Therefore,it is necessary to adjust the suspension,make the core move in the middle of the cross-linking pipe as far as possible,find foreign bodies,and clean up in time.
(2)There is scorch on the outer edge of the die sleeve.The solution is to adjust the temperature of the die sleeve to prevent overheating when starting the car.Once burning is found,it should be stopped immediately to remove it,or it will not improve by itself.
Impurities in insulating and semi-insulating materials are mostly brought in during mixing and feeding process of extruder.During operation,strict attention should be paid to the cleaning of materials to prevent foreign impurities from mixing in.Another impurity is burning lump,which affects the performance and service life of the cable.Therefore,temperature should be strictly controlled during mixing and extrusion to prevent burning.
There are two possible reasons for the bubbles generated in insulation.One is caused by extrusion.The solution is to select the appropriate die.There are bubbles in the shielding layer.The main reason is that there is water in the material.It should be dry before extrusion.The second reason is that the cooling is insufficient.At this time,a circle of bubbles appears on the circumference equidistant from the core.The elimination methods are strengthening cooling,raising water level and lowering the temperature of cooling water.
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