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    Thermal Cleaning

    Thermal Cleaning

    When using an injection mould tool with a Hot Runner System it is sometimes necessary to clean the system due to misuse.
     
    Typical examples of situations that result in the manifold requiring cleaning are as follows:
     
    Manifolds Left With Power On For Extended Periods
    Many older moulding machines will not power down the heaters when the machine is shut-off, so manifolds are left to overheat.
    This will result in two things:
    • The overheated plastic is significantly reduced in viscosity causing the resin (weepage) to migrate into tooling clearances.
    • The tooling overheats, causing the manifold to over-expand and hob sealing surfaces, reducing the ability to seal when the manifold temperature is brought back down into range.
     
    If the plastic resin that is being processed is sensitive to heat, an engineering grade or a filled material then serious overheating can result in the material crystallising inside the melt channels of the Hot Runner System and is unable to be re-melted.
     
    Process Habits
    Failing to reduce shot size when blocking cavities, not using back pressure when filling empty manifolds, running temps to high, reversing valve pin sequence and forgetting to turn on the cooling are just a few of several processing conditions that contribute to leaking systems.
     
    Lack of Preventative Maintenance
    Worn valve pins and bushings seem to be a major contributor, particularly where manifolds are long overdue for thorough maintenance. Also lethal are hobbed manifolds, spacers and other tooling where combined dimensions are under the recommended cold stack height. This also includes stressed/stretched bolts.
     
    Cleaning Processes
    There are many processes available to assist you with a thorough cleaning of a manifold. Depending on the complexity of your manifold it is often impossible to properly clean the channels inside a manifold simply by removing plugs and removing the plastic.
     
    Common Applications
    • Plastic Hot Runner System
     
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