Hot Runner Considerations, Part 1

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The requirements and topics of interest regarding hot runner systems and their suppliers vary to some degree from a mold manufacturer’s perspective versus those of the injection molder. Mold makers are often concerned about price, delivery, and quality…all of which are important considerations that benefit the mold and the mold maker’s reputation.

Both the injection molder and the mold maker need to be part of the decision process when considering a hot runner system and hot runner supplier. Molders are often relying on the expertise of their mold supplier to evaluate the system when it comes in and to ensure the integration of the hot runner system to the mold. Afterward however, the injection molder is the one who needs to use the hot runner system to mold parts. As such, the hot runner operation, performance and ease of maintenance are now the concern of the molders.

Below is an initial list of considerations for injection molders to help you get started when evaluating hot runner suppliers for various projects. Future Tech Tips will continue to discuss this topic and provide additional considerations.

    1. Previous Experiences – you will always hear both horror stories and stories of stellar performance about any given hot runner supplier. Often those previous experiences are the determining factor in whether or not future purchases will be made, or even considered, with that particular supplier. But those experiences, especially if they are based on experiences from a decade or so ago, may not be the best factor when selecting a hot runner supplier.


    1. Range of Products – what products does a given supplier offer for a given project? Evaluate nozzle capacity (micro vs. large capacity), pending the product you are molding; evaluate the type of gating options based on your product (thermal gate, side gating, close pitch, valve gate, etc…); if valve gates are a requirement, do they offer the required technology for a given product or market (pneumatic, hydraulic, electric, synchronous).


    1. Complete “Hot Half”– does the supplier offer components only or can they supply a fully assembled and tested hot runner system?


    1. Market Experience – despite the “sales pitch” every hot runner supplier’s product range tends to favor specific markets. Look for a product offering that is designed to match the needs of the markets you are supplying. The hot runner supplier should possess experience in molding applications and materials suited to those markets.


    1. Application Engineering – the supplier should be able to offer guidance in gate location for optimizing filling and packing, gate/nozzle configuration, channel sizes, gate cooling, etc. Find out if they offer flow analysis services. If so, do they verify the results? Ask about other design capabilities, such as those used to produce a mechanically and thermally balanced hot runner system. Ask what criteria are used to determine channel diameters and make sure they meet your needs as well. There should be consideration to the part, material and overall process in any decision being made, and be sure to ask for an explanation to back up those decisions.


    1. R&D – does the supplier have a fully equipped molding lab to assist in material and new technology testing? Does the company show evidence of a commitment to product testing, research, and development? To help gauge if a given supplier is leading or “chasing” technology, ask about what new innovations they developed recently and what they are working on currently.


    1. Service & Technical Support – inquire with them as to their response time and policies when there is a problem. Find out how many service technicians they have and if one is local to you. If you are new to hot runners or not, find out if they offer training and start-up assistance and if so is there a cost? When issues arise, and they will, minimizing downtime becomes priority number one. You want a supplier who will rise to the occasion to help ensure your success, because ultimately it helps ensure their success for future business with you.


  1. Maintenance – the fact that maintenance will be needed at some point is a given, but hopefully not a weekly occurrence. As such, look for features that allow for ease of maintenance to help minimize down time and expenses. Does the hot runner design allow the gates to be inspected and cleaned in the injection molding machine? Can wear items such as nozzle tips, thermocouples and nozzle heaters be serviced with the mold still inside the machine? And the same question applies regarding valve pins adjustments and service.