PVC wire and cable
DATE：2022/11/29 8:27:00 / READ： / SOURCE：This station
(1) Equipment conditions
The equipment used to wrap the cable material on the conductor after plasticizing and melting is mainly the extruder, molding die, cooling water tank, tester and winding device.① Extruder Extruder for wire and cable molding is mainly a single screw extruder with small specifications and models. The screw structure is of equal distance and unequal depth gradual type, the length diameter ratio L/D is (18~25): 1, and the compression ratio is 3:1.
② Molding die The structure of the mold for PVC wire and cable extrusion molding is the same as that for PE wire and cable extrusion molding (Figure 10-1) See Table 10-13 for the parameters of the auxiliary machine for wire and cable extrusion molding
(2) Forming process
① PVC resin shall be screened with 40 mesh screen, and slurry such as stabilizer and colorant shall be grinded with a grinder.② Kneaders or high-speed mixers can be used for mixing main raw materials and auxiliary materials. When mixing with kneader, apply 0.3MPa right force to the jacket and mix for about 50min; If a high-speed mixer is used to mix raw materials, the steam heating pressure is about 0.2MPa, and the mixture is stirred for 10min. The material temperature after mixing is about 110 ℃. Pay attention to the feeding sequence. Mix the resin and plasticizer first, and then add other auxiliary materials.
③ If it is found that the cable material for production has high moisture content, it shall be dried first (in an 80 ℃ oven for 2h).
④ The supply of core wire shall be continuous (another pay off machine shall be prepared if necessary). The core wire before entering the mold shall be straightened, and at the same time, it shall have a certain temperature (preheating treatment) to ensure that the plastic and metal wire can adhere well.
⑤ The plasticizing temperature of the cable material in the extruder is the same as that of the plasticized PVC hose material in the extruder, which is generally controlled within the range of 130~160 ℃. The temperature of the forming die is within the range of 160~180 ℃.
(3) Quality requirements The quality requirements of flexible PVC plastics for wires and cables shall comply with the provisions of GB/T8815-2002.
① See Table 10-14 for the model of PVC cable material, the maximum allowable working temperature of conductor core and its use.Table 10-14 Model of Cable Material, Maximum Allowable Working Temperature of Conductor Core and Application
Model Maximum allowable working temperature of conductor core Main purpose/℃
J-70 70 Insulation layer of instrument communication cable, 0.6/1kV and below cable
JR-70 70 Insulation layer of 450/750V and below flexible wires and cables
Sheath of 70, 450/750 V and below wires and cables
H-70 80 Sheath of 26/35kV and below power cables
Protective layer of HR-70 450/750V and below flexible wires and cables
JGD-70 70 Insulation layer of 3.6/6kV and below power cables
HI-90 90 35kV and below power cable and other similar cable sheath
H Ⅱ - 90 90 450/750V and below wire and cable sheath
J-90 90 450/750V and below heat-resistant wire and cable insulation layer
② Appearance quality. The overall dimension of the cable material is 4mmx4mmx3mm square granular or cylindrical with the same size; It shall have good plasticization, consistent color and luster, and shall be free of obvious impurities.
③ The color of insulation grade cable material is red, black, blue, yellow, green, brown, etc. The color of cable material at the protection layer is black, white, gray, etc.
④ See Table 10-15 and Table 10-16 for mechanical, physical and electrical properties of cable materials
(4) Quality analysis
① Rough surfacea. The raw materials are plasticized unevenly.
b. The barrel temperature is low.
c. The moisture content of raw materials is high.
d. The filter screen is broken and there are many impurities in the material.
② There are bubbles in the plastic layer
a. The raw materials are wet and should be dried.
b. The plasticizing temperature of the melted material is on the high side.
c. The temperature drops too fast after the products are extruded from the mold, and the cooling water temperature is low.
③ Manual for Extrusion Molding Technicians with Impurities or Granular Plastics on the Surface
a. Poor resin quality, too many fish eyes.
b. The filter screen is broken and there are many impurities in the molten material.
c. Poor plasticizing quality of raw materials and low barrel temperature.
④ The plastic layer is not firmly bonded to the core wire
a. There is grease or other dirt on the surface of the core wire.
b. Core wire preheating temperature is low.
c. The plastic layer cools too fast.
d. The temperature of molten material is low.
⑤ Longitudinal thickness fluctuation of plastic coating
a. The rotation speed of the screw fluctuates, and the amount of molten material extruded is uneven.
b. The traction speed is not stable, and it is sometimes fast or slow.
c. The barrel heating temperature fluctuates greatly.
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