Guide How to choose the correct hot runner supplier

Editor: Rosemarie Stahl

When confronted with the increase in available hot runner systems on the market, making the correct choice for a hot runner supplier is critical. Three qualities are particularly important to consider in the decision-making process: analysis capabilities, design input and product range.

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When looking for a supplier, manufacturers often feel overwhelmed by the countless offers.
When looking for a supplier, manufacturers often feel overwhelmed by the countless offers.
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During the infant stages of a new mould build it is critical that a hot runner designer can provide input and feedback on the part design and layout of the mould. Analysis software programs can assist with the correct gate location and number of gates, warpage, shrinkage, pressure drop, weld lines, gas traps, shear stress, temperature rise and part fill time so that the performance of the hot runner and the mould are optimised.

Incorrect use of a hot runner can adversely affect the performance of a mould and the product it produces. An example of this is the degradation of material within a hot runner or mould cavity. Some factors affecting plastic material degradation are: Poor venting, increasing melt temperature or injection velocity, dead areas or shear points within the hot runner, and long residence times inside the hot runner.

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Proper hot runner analysis and manufacture can assist with:

  • Identifying likely areas for gas traps to determine vent placement
  • Optimising melt channel diameters to keep shear stresses at ideal values
  • Thermocouple placement for accurate and reliable heater control
  • Advice on profiling and polishing melt channels and the use of correct diameter reduction techniques
  • Optimising melt channel lengths to each cavity, particularly in family moulds

Thermal finite element analysis (FEA) can assist with determining the optimum thermal profile of the hot runner system. Through the use of proper analysis tools and techniques, the hot runner supplier can predict issues at an early design stage and make recommendations to the mould-maker for an improved result.

During the design process, mould-makers should look for a partner that can supply hot runner drawings and models that are easily integrated into their mould designs. Hot runner 3-D models used for approval drawings ensure they are simple for the mould designer to check and can easily provide gate insert or plate drawings for manufacturing. The hot runner supplier’s ability to be flexible with drawing file formats and CAD packages is key to a successful partnership.

Correct part design is crucial to a successful mould build and there are many areas where the hot runner supplier can offer advice based on experience in the injection moulding industry. Design features such as cooling circuits around the gate, dimples in the gate area and thin wall sections can be commented on and improvements made before a commitment to a particular design. When hot runner suppliers are invited to be involved in projects at an early stage they are able to provide input into part design, cavity design and mould layout that can be crucial to a successful mould.

Competition, the rising costs of materials, time restraints and new technologies are pressures that are not new, but exponentially increasing. Efficient use of time, mould and plastic materials is critical to the success of every new tooling program. Ensuring optimisation at the earliest stage of design when the cost of change is lowest will save time and money throughout the build process. Commissioning, production efficiency, part quality, cycle time and material content is also influenced by time invested with your hot runner supplier during the early design stage.

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