The Internally Heated Difference

Below is a brief overview of just some of the advantages of Melt Design’s internally heated hot runner products versus their externally heated industry counterparts. For more information about Melt Design’s internally heated hot runner products give us a call at 630-443-4000.

Temperature Profile

With an external heater, the heating coil expands and air gaps are created between the heater and the nozzle body. Because the air gap is not uniform around the nozzle body, there is variation in the heat transfer rate from the coil to the nozzle resulting in uneven heating of the melt. Melt Design’s internal heater construction eliminates the potential for the formation of air gaps which results in a uniform temperature profile over the entire nozzle length and maximizes process control.

Thermocouple Location

Melt Design’s internally heated nozzles are equipped with a replaceable thermocouple near the tip of the nozzle providing accurate temperature readings where they matter most. The thermocouple on an externally heated nozzle is generally located further from the nozzle tip, away from the critical area where melt temperature is most important to a molder.

Heater Life

Melt Design’s internally heated nozzles have a long heater life. The highly dense insulator, and its proximity to the melt channel, optimizes heat transfer to the melt. Because of this, the heating element can run at, or very close to, the desired melt temperature. This configuration resists the formation of hot and cold zones in the nozzle. Conversely, the heating element in an externally heated nozzle is much farther away from the melt channel. Heat must be transferred from the heater band, through any air gaps between the heater and the nozzle body, and finally through the nozzle body itself. To achieve the desired melt temperature the external heater needs to run hotter, meaning more electrical current and “uptime” which shorten the heaters life.

Heater Protection

External heating elements are exposed to potential damage as well as contamination from leaking plastic. Plastic leaking over an external heater requires that the heater be cleaned or replaced. This process is both time consuming and costly due to mold downtime and/or heater replacement and rewiring. The location of Melt Design’s internal heating element protects it from damage or contamination from an accidental plastic leak. Plastic that forms around the exterior of the nozzle body can be easily removed without the expense of replacing a costly heating element.