Injection hot runner plate outlet groove
In injection molding hot runner systems, the design of the hot runner plate’s wire troughs is a crucial component in ensuring proper system operation. Their primary function is to provide wiring pathways for electrical components such as heating elements and temperature sensors on the hot runner plate, protecting wires from high temperatures, high pressures, and mechanical wear. They also ensure neat and orderly wiring for easy installation, commissioning, and maintenance. The rationality of the wire trough design directly impacts the stability, safety, and service life of the hot runner system. For example, an undersized wire trough can lead to congested wires, impairing heat dissipation and even causing short circuits. An oversized wire trough, on the other hand, increases the volume and weight of the hot runner plate, wasting material.
The size design of the hot runner plate’s wire trough needs to be determined based on the number, diameter, and wiring method of the wires. Normally, the width and depth of the wire trough should be slightly larger than the diameter of the wire bundle to ensure that the wires can pass through smoothly, while leaving a certain gap for heat dissipation. For multiple groups of wires, partitions should be installed in the wire trough to separate wires with different functions to avoid mutual interference. The length of the wire trough should be determined based on the size of the hot runner plate and the installation position of the electrical components to ensure that the wires can be smoothly led out from the inside of the hot runner plate to the external junction box. When designing a large hot runner plate, a mold factory did not fully consider the number of wires, and the size of the wire trough was too small, resulting in the wires being unable to be fully accommodated. The wire trough had to be reprocessed, which not only delayed the production cycle but also increased the mold cost.
The location and direction of the wire trough also need to be carefully planned. Key areas such as the runner and heating holes on the hot runner plate should be avoided as much as possible to prevent affecting the structural strength and heating uniformity of the hot runner plate. At the same time, the direction of the wire trough should be simple and smooth, avoiding excessive bends and turns to reduce wear and resistance on the wires. At the corners of the hot runner plate, the wire trough should adopt an arc transition to avoid right-angle design to prevent the wires from being scratched. When a certain automotive mold company was producing hot runner plates, the direction of the wire trough was too complicated, resulting in the wires being scratched by the sharp edges at the corners many times during installation, causing short circuit failures. This problem was later solved by changing the right angle to an arc transition with a radius of 5mm, reducing the failure rate of the hot runner system by 40%.
The sealing and insulation design of the wire trough is crucial to the stable operation of the hot runner system. Since the working temperature of the hot runner plate is relatively high, usually between 150-300℃, the wires in the wire trough are exposed to high temperature for a long time and are prone to aging and damage. Therefore, effective insulation measures need to be taken, such as laying insulation materials or setting up insulation baffles in the wire trough to reduce the transfer of heat to the wires. At the same time, the wire trough needs to be sealed to prevent plastic melt, oil stains, etc. from entering the trough to contaminate the wires or cause short circuits. In the design of the hot runner plate wire trough, a plastic machinery factory used high-temperature resistant silicone sealing rings for sealing and laid glass fiber insulation cotton in the trough, which reduced the working environment temperature of the wires by 60℃ and greatly extended the service life of the wires.
The processing technology and precision control of cable troughs are also crucial. Wire troughs are typically milled, requiring guaranteed dimensional accuracy and surface roughness to avoid burrs, unevenness, and scratches on the wires. For deep or narrow cable troughs, appropriate tools and processing parameters should be selected to ensure quality. After processing, the troughs need to be cleaned and polished to remove residual chips and burrs. A precision mold manufacturer, while machining hot runner plate cable troughs, failed to promptly replace worn tools, resulting in numerous burrs within the troughs. This caused the insulation of several wires to be scratched during installation. By replacing high-precision tools and adding a polishing step, the surface roughness of the troughs was reduced from Ra1.6μm to Ra0.8μm, completely resolving the wire scratching issue. Furthermore, during assembly, careful attention should be paid to the order of wires to avoid cross-entanglement and ensure optimal use of space within the troughs.
