Cold Runner Injection Molding Of Pet Preform Mould

Thin wall. A common best practice for cold runner Pet Preform Mould injection molding is to avoid thin walls. This is because when the heated substrate encounters the cooler wall of the cavity, it immediately begins to harden. If the wall is too close, it will cool and create a plug that blocks the rest of the substrate from passing. This problem also creates an abnormal cooling time when the cooled substrate is reheated and re-cooled by hot liquefied plastic or rubber.
Flow rate problem. When the substrate passes through the runner and fills the cavity, cold forming may encounter flow rate problems, which has begun the cooling process. In these cases, the cooling time becomes more unpredictable, resulting in unreliable flow rates, which can result in rejected or failed finished parts due to incomplete mold fill or sinking.
Let us now look at some of the advantages that hot runner injection molding can offer, and cold forming systems may still be the most cost-effective and profitable option.
No runners mean less waste. In a hot runner system, any residual substrate that flows through the runner chamber but does not enter the mold cavity remains heated and liquefied, thus flowing directly through the mold and back into the “pool” of the readily available molding material for the next cycle Used in. In cold molding, this runner is either discarded (meaning material waste) or regrind and recycled into the material pool in a more time consuming process.
Faster cycle times. As mentioned above, the runner recycling process takes time, and if you do not invest this time, you may lose resources. By eliminating the concerns of all runners, the hot runner system eliminates these finishing processes and potentially speeds up cycle times. Keep in mind that it takes extra time to heat and cool the mold during the hot runner process – this time is usually offset by the savings from eliminating the hot runner, but it is worth discussing your choice with the injection service provider.
A “cleaner” finished product. The mechanical removal process is required to remove the flow path from the cold molded part, whether by robot or manual removal. If a clean break or shear is not achieved, it may affect the acceptability of the finished product, depending on your cosmetic and operational requirements. Thermal molding also helps to eliminate many problems, such as burn marks or other surface irregularities, which can occur where the temperature of the mold and substrate is not strictly controlled or monitored.
Despite these advantages, it is important to remember that cold runner injection molding is still a viable and widely used process. Your injection molding machine should be proficient in the pros and cons of each process and should be willing to discuss with you to determine your best choice. Here are some ways that cold forming is still useful.
Reduce tool costs. Choosing cold forming or thermoforming involves weighing costs in the long-term production process. The upfront cost of cold molding tools will be lower, and the more complex demand for hot molds will result in corresponding price increases (this can be offset by the faster cycle times described above). However, for shorter production runs, the cold runner system may still be most beneficial to you.
A wider range of materials. The inherent chemical composition of most injection molded substrates makes them highly sensitive to temperature fluctuations, especially extreme temperatures. The nature of the hot runner system means that less material is suitable and beneficial for use in the process.
It is easier to choose a colorant. Although hot runner injection molding can easily incorporate colorants into the process, it is more difficult to change these colors throughout the production process. Cold runner injection molding makes it easier to apply different color options to the forming substrate or finished product.
As you can see, there is no clear “best choice” for the injection molding process. If you want to get the best choice, then look for a good, reliable pet preform manufacturers, professional design and discussion, you will get the best mold injection molding.


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