When the 4-core parallel bundled wire is extruded, the four conductors are co-extruded. The pressure distribution of the plastic in the mold is uneven, the outer insulation is thicker, and the inner insulation is thinner, and it cannot be adjusted. The traditional extrusion die adopts vertical, vertical, left, and right deflection bolts to adjust the amount of extrusion eccentricity. The internal flow path and pressure of the die are not balanced. The extrusion eccentricity is not easy to adjust, so the thickness of the extrusion is uneven and not easy control. The fine-tuning die Plastic mould manufacturers https://www.nbtianke.com designed by us is a semi-extruded tube type. The die is composed of a core, a middle die, and a mold sleeve plate (see Figure 5). This design is to better adjust the eccentricity. After the mold core and the middle mold part are inserted into the machine head, a press plate of the machine head is fixed in the machine head and cannot be moved. The mold sleeve plate can be adjusted by 4 pieces of the machine head The bolts are finely adjusted for eccentricity.
1.1 Mold size
When the conductor cross section is 10 ~ 70mm2, the inner diameter of the core d = conductor outer diameter + 0.5mm; when the conductor cross section is greater than 70mm2, the inner hole size d = the outer diameter of the conductor +1mm, the core wall thickness is 0.5mm. Because the mold is designed as a semi-extruded tube, the size of the mold sleeve is designed to be the outer diameter of the core hole + 2 times the nominal thickness of the insulation.
1.2 Assembly of the mold
The initial design of the four holes of the mold sleeve has the same horizontal and vertical spacing as the mold core (see Figure 6). After debugging, the insulation produced is thicker on the outside and thinner on the inside. The reason for the analysis is that the plastic has a lower pressure in the outer flow channel section of the mold, and a longer inner flow channel and a higher pressure. Therefore, the outer thickness is thinner. We analyzed and fine-tuned the mold sleeve. As shown in FIG. 7, the positions of the four inner holes of the mold sleeve are finely adjusted, and the horizontal spacing and the vertical spacing of the mold sleeve are simultaneously reduced by t (the value of t is related to the insulation thickness, and the thicker the thickness, the greater the value of t). We take a 4×35 mold sleeve adjustment distance of 0.2mm as an example for trial production. After the adjustment, the thickness of the inner part of the mold assembly will be correspondingly widened, which is beneficial to adjust the pressure on the inside of the mold and increase the amount of glue out on the inside, so as to achieve the same effect as the thickness of the outer extrusion. After many adjustments and experiments, the insulation eccentricity of the parallel bunched wire has basically achieved the desired effect.
2 Process requirements
2.1 Process requirements for mold assembly
During the production of 4-core parallel bundle conductors, due to the uneven extrusion pressure, the eccentricity is unqualified, so the horizontal spacing and vertical spacing of the four inner holes on the die sleeve plate are appropriately reduced. The larger the wire diameter is, the larger the reduced spacing is. The specific value of the spacing to be reduced can be obtained after many tests. Therefore, it is necessary to prepare several mold sleeve plates with different pitches during production, so as to facilitate replacement and adjustment at any time. After the mold is adjusted for the first time, tighten the four bolts of the mold sleeve plate to fix the mold sleeve plate, and it can be used directly as a mold-free mold for next production.