Analysis of extrusion defects of the hottest wires

  • Detail

Big analysis of wire and cable extrusion defects

I. scorch

1. Scorch phenomenon

(1) the temperature reflects ultra-high, or the instrument controlling the temperature fails, causing the plastic to scorch at ultra-high temperature

(2) the glue outlet of the machine head has large smoke, strong pungent smell, and crackling sound

(3) granular scorched substances appear on the plastic surface

(4) there are continuous pores at the glue joint

2. Causes of scorch

(1) plastic scorch caused by ultra-high temperature control

(2) the screw has been used for a long time without cleaning, and scorched materials are accumulated and extruded with plastic

(3) the heating time is too long, and the plastic deposit is heated for a long time, so that the plastic is aged, deteriorated and burnt

(4) the parking time is too long, and the machine head and screw are not cleaned, resulting in plastic decomposition and scorching

(5) change the mold or color for many times, causing the plastic to decompose and scorch

(6) the head gland is not compressed, and the plastic is aged and decomposed inside

(7) the instrument controlling the temperature failed, resulting in scorch after ultra-high temperature

3. Methods to eliminate scorching

(1) check whether the heating system is normal frequently

(2) clean the screw or head regularly and thoroughly

(3) heat up according to the process requirements. The heating time should not be too long. If there is a problem with the heating system, it should be solved by relevant personnel in time

(4) mold change or color change should be timely and clean to prevent mottled or burnt glue

(5) after adjusting the mold, press the mold sleeve gland tightly to prevent glue feeding by the end of 2014

(6) in case of burning, clean the machine head and screw immediately

the copper wire inside is processed by copper ingot at high temperature

II. Poor plasticization

1. Poor plasticization phenomenon

(1) toad skin phenomenon on the surface of the plastic layer

(2) the temperature control is low, the temperature reflected by the instrument pointer is low, and the actual measured temperature is also low

(3) the plastic surface is dark, with tiny cracks or small particles that are not well plasticized

(4) the glue of plastic is not sewn well, and there is an obvious trace

2. Causes of poor plasticization

(1) the temperature control is too low or inappropriate

(2) there are resin particles in plastic that are difficult to plasticize

(3) the operation method is improper, the screw and traction speed are too fast, and the plastic is not fully plasticized

(4) uneven mixing of plastics during granulation or quality problems of plastics themselves

3. Methods to eliminate poor plasticization

(1) control the temperature according to the process regulations. If the temperature is low, appropriately increase the temperature

(2) the speed of screw and traction should be appropriately reduced to increase the time of plastic heating and plasticization, so as to improve the effect of plastic plasticization

(3) use screw cooling water to strengthen the plasticization and tightness of plastics

(4) when selecting the mold, the mold sleeve should be smaller and the pressure at the rubber outlet should be strengthened

III. pimples

1. The phenomenon of pimples

(1) the pimples produced by the resin during the plasticization process have small crystal dots and particles on the surface of the plastic layer, which are distributed around the surface of the plastic layer

(2) there are burnt objects on the surface of the plastic layer, especially on the surface of the glue joint

(3) impurities pimple, there are impurities on the plastic surface, and there are impurities in the pimple of the slice

(4) plastic pimples caused by poor plasticization. After slicing, it was found that the pimples were filled with cooked glue

2. Causes of pimples

(1) due to low temperature control, the plastic was extruded from the machine head before it was plasticized

(2) the quality of plastic is poor, and there are resins that are difficult to plasticize, which are extruded without complete plasticization

(3) some impurities are added into the hopper during feeding, causing impurities pimple

(4) the temperature control is too high, causing scorch, resulting in scorch knots

(5) the molded cover was not pressed, and it was aged and deteriorated after glue feeding, resulting in burnt knots

3. Methods to eliminate pimples

(1) for pimples caused by plastic itself, the temperature should be appropriately increased

(2) strictly check whether there are sundries in the plastic during feeding. Do not add other sundries into the hopper during feeding. If any impurities are found, immediately clean the machine head and run away the glue stored in the screw

(3) if the temperature is found to be too high, the temperature should be reduced appropriately immediately. If the effect is not good, the machine head and screw should be cleaned immediately, and coke 3 should be removed to realize the tightening movement of the spring

(4) if there are resin pimples and pimples with poor plasticization, appropriately increase the temperature or reduce the speed of screw and traction

IV. positive and negative out of tolerance of plastic layer

1. Out of tolerance phenomenon

(1) the speed of screw and traction is unstable, and the ammeter or voltmeter swings left and right, which affects the outer diameter of cable and produces deviation of plastic layer

(2) there are problems in the quality of semi-finished products, such as loose wrapping of steel strip or plastic belt, uneven convex concave phenomenon or defects such as bags, edges and pits in the plastic layer

(3) the temperature control is too high, resulting in the reduction of extrusion volume, which makes the outer diameter of the cable suddenly thinner and the plastic layer thinner, forming a negative difference

2. Causes of out of tolerance

(1) the wire core or cable center is not round, and there is a snake, and the outer diameter changes too much

(2) there are quality problems in semi-finished products, such as poor steel belt joint, loose steel belt sleeve, steel belt crimping, loose plastic belt sleeve, too large joint, scattered flowers, etc

(3) during operation, the mold core selection is too large, resulting in glue pouring and plastic layer deviation

(4) when adjusting the mold, the mold adjusting screw was not tightened, resulting in reverse buckle, which made the plastic layer eccentric

(5) the screw or traction speed is unstable, resulting in out of tolerance

(6) the feeding port or filtering part is blocked, resulting in the decrease of glue output and negative difference

3. Methods to eliminate out of tolerance

(1) regularly measure the outer diameter of the cable and check the thickness of the plastic layer. If it is found that the outer diameter changes or the plastic layer is uneven, it should be adjusted immediately

(2) the matching mold should be appropriate. After adjusting the mold, tighten the mold adjusting screw and press the gland tightly

(3) pay attention to the current and voltmeter of the screw and traction. If it is found to be unstable, it is necessary to find an electrician and fitter in time for maintenance

(4) do not add strips or other sundries into the hopper. If this situation is found, it should be removed immediately

v. uneven thickness and bamboo shape of cable outer diameter

1. Uneven thickness and bamboo shape

(1) uneven thickness of cable outer diameter due to unstable screw or traction

(2) due to the sudden instability of traction, the plastic forming the cable is in the shape of bamboo knots

(3) the mold selection is small, and the outer diameter of semi-finished products changes greatly, resulting in uneven thickness of the plastic layer of the cable

2. Reasons for uneven thickness and slub shape

(1) uneven speed of pay in and pay out or traction

(2) the outer diameter of semi-finished products changes greatly, and the mold selection is inappropriate

(3) the screw speed is unstable, the speed of the main motor is uneven, and the belt is too loose or slipping

3. Methods to eliminate uneven thickness and slub shape

(1) regularly check whether the speed of screw, traction, and pay in and pay off is uniform

(2) mold selection should be appropriate to prevent glue pouring

(3) regularly check the operation of machinery and electrical appliances, and immediately find fitters and electricians to repair any problems

VI. bad glue joint

1. Bad glue joint phenomenon

(1) on the outside of the plastic layer surface, the plastic is not merged well, there is a black mark, and there are cracks in serious cases

(2) the glue joint of the plastic layer is not plasticized well, and there are pimples and small particles, which can be torn open by hand in serious cases

(3) the control temperature is low, especially the control temperature of the machine head

2. Reasons for poor glue joint

(1) low control temperature and poor plasticization

(2) the machine head has been used for a long time, causing serious wear

(3) the temperature control of the machine head fails, causing low temperature and poor plastic lamination

3. Methods to eliminate bad glue joint

(1) appropriately increase the control temperature, especially the control temperature of the machine head

(2) heat preservation device is used outside the machine head for heat preservation

(3) add two layers of filtration to increase the pressure and improve the plasticization degree of plastic

(4) appropriately reduce the speed of screw traction to prolong the plastic plasticizing time and achieve the purpose of plastic joint

(5) lengthen the wire diameter of the die and increase the extrusion pressure and temperature

VII. Other defects

1. Pores, bubbles or air holes

(I) causes

(1) local control temperature is too high

(2) the plastic is wet or has moisture

(3) the excess gas in the plastic was not eliminated after parking

(4) the natural environment is humid

(II) troubleshooting

(1) the temperature control should be appropriate. If the temperature is found to be too high, it should be adjusted immediately to prevent local temperature from being too high

(2) strictly check the quality of plastic during feeding, especially in rainy seasons. If there is moisture and water, stop using it immediately, and then run away the damp material

(3) add a preheating device at the feeding place to drive away the moisture and moisture in the plastic

(4) take samples frequently to check whether there are pores, air holes and bubbles in the plastic layer

2. Disconnection or glue breaking

(I) causes of occurrence

(1) there is water or oil in the conductive wire core

(2) the wire core is too heavy to locally contact with the mold core, resulting in temperature reduction, local cooling of the plastic, and disconnection or glue breaking due to plastic stretching

(3) the quality of semi-finished products is poor, such as loose sleeves of steel and plastic belts, and the joints are not firm or too large

(II) troubleshooting

(1) the mold selection should be larger, especially the mold with sheath should be enlarged by 6 to 8mm

(2) appropriately reduce the length and thickness of the core nozzle

(3) reduce the speed of screw and traction

(4) appropriately raise the control temperature of the machine head

3. Pits and eyes

(I) causes

(1) the conductor core is not tightly twisted and has gaps

(2) there is water, oil and dirt in the wire core

(3) semi finished products have defects, such as strand payout, pressing, crossing, bending, steel belt and plastic belt overlap, loose sleeves, oversized joints, etc

(4) low temperature control

(II) troubleshooting

(1) the tightening of stranded conductors shall comply with the process regulations

(2) if the semi-finished products do not meet the quality requirements, they should be processed before production

(3) the method of successive comparison is adopted to remove dirt, and the cable core or wire core should be preheated

4. Plastic layer wrapping, edges and corners, ears, wrinkles and bumps

(I) causes

(1) quality problems caused by plastic tape wrapping and steel tape wrapping

(2) the mold selection is too large, which is caused by vacuum pumping

(3) plastic glue pouring occurs after the mold core is damaged

(4) the core is too heavy and the plastic layer is not cooled well

(II) troubleshooting

(1) check the quality of semi-finished products, and unqualified products will not be produced

(2) check the mold before assembly, and handle the problems before use

(3) mold selection should be appropriate. Reduce the traction speed appropriately, so that the plastic layer is completely cooled

5. Traces appear on the plastic surface

(I) causes

(1) the surface of the die sleeve bearing wire diameter is not smooth or there is a gap

(2) if the temperature is too high, the barium stearate of the plastic itself decomposes and accumulates at the die socket, causing traces

(II) troubleshooting

(1) when selecting and matching the mold, check whether the surface of the die sleeve bearing wire diameter is smooth, and if there are defects, deal with them

(2) reduce the temperature of the heating area of the machine head appropriately, and remove barium stearate immediately after it is produced

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