Insulated runner moulds

An example of a hot-runner mould an insulated runner mould with heated probes (after Modern Plastics Encyclopedia). 

The runners and sprues are necessary in a mould but they are not part of the end-product. Unfortunately, it is not economically viable to discard them so they must be re-ground for subsequent reprocessing. Regrinding is expensive and can introduce contamination into the material so that any system which avoids the accumulation of runners and sprues is attractive. A system has been developed to do this and it is really a logical extension of three plate moulding. In this system, strategically placed heaters and insulation in the mould keep the... 

High heat bushings, valve seats, ball valve seats, contact seals, insulator bushings. .. Thermal isolators, high heat insulator bushings for hot runner plastic injection moulds... Guide rollers. .. 

As shown in Fig. 7.12, the connector was designed with an T beam cross-section, which provided the basic cavity for insertion of the contacts. Runner slots were designed into the connector to accept a contact-retaining insulator, which prevented the contacts snapping out of their pre-loaded position. Each contact slot has an integrally moulded shoulder, providing a support for the contact strip prior to insertion. 

As the plastic melt progresses through the runner, the melt touching the cold mould surface will rapidly decrease in temperature and solidify. The material which follows will pass through the eentre of this solidified material and, because of die low eonduetivity that thermoplastics possess, the solidified material acts as an insulation and maintains the temperature in the central melt flow. 

Insulate the hot runner manifold and nozzles from the machine platen or mould cavities by air or compressed temperature resistant sheeting... 

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