The Importance of Precise Hot Runner Temperature Control

Thu, 07/09/2020 - 13:51

Hot runners are known to offer many processing advantages. However, to maximize your productivity and production quality, maintaining precision temperature control is a critical component for these systems to work as designed. Maintaining precise temperature control is known to affect part quality and processing as temperature directly impacts processing variables associated with the Resin Characteristics and Hot Runner System.


All thermoplastics degrade under elevated temperatures. A well designed hot runner system eliminates hot spots from its design and precise temperature control will help to ensure temperature uniformity of the system during processing. Temperature uniformity is important because it allows you to bring the overall system temperature closer to the lower processing temperature limit. The greater the heat history of the polymer, the more the properties of the polymer will have been weakened.

Additionally, as the plastic melt is forced along the hot runner channel under pressure, it is subject to shear which also generates additional heat. Precise temperature control becomes especially challenging when processing shear sensitive or highly viscous polymers and additives. Otherwise polymer properties will deteriorate and part quality will be affected.


In a multi-cavity system, natural flow balance means the same flow length, same channel diameter and the same number of turns from the machine nozzle to each mold cavity. In conjunction with temperature uniformity across the entire system, this leads to uniform filling and back pressure conditions in each cavity, uniform part quality and the widest processing window. Where changes in material or injection parameters exist (like temperature) these changes will cause quality problems such as poor weight consistency.

The hot runner and mold cut-out are dimensioned so that all hot runner components are perfectly aligned at the specified operating temperature. To allow for heat expansion, sliding or rotational pressure seals are used between hot runner components. If excessive temperature variations exist in the system, it can cause leakage or even component fatigue and/or failure. The nozzle center axis must remain in an absolutely fixed position, in exact alignment with the gate at processing temperature.

Fast Response is Crucial

Injection molding is a cyclical process. The hot runner must maintain accurate and uniform temperature conditions through both the heating (injection) and cooling (hold) phases of the molding cycle. Since the gate is the most critical areas of the hot runner, it is essential for the TC to accurately measure gate temperature. For quick and accurate response to temperature over or under swinging, closed-loop temperature control is required for each and every nozzle. The quality of the molded part is directly related to temperature control response efficiency.

Unlock your Operations Full Potential

Mold-Masters offers precision temperature control through our comprehensive line of advanced TempMaster Hot Runner Temperature Controllers. They have the ability to optimize the performance of any hot runner system.

All TempMaster hot runner temperature controllers feature APS Technology which maintains set point for precision temperature control of 1 to over 500 zones. APS is a proprietary Auto-Tuning algorithm that continuously monitors, learns, predicts and automatically adapts to process variables every 20mS.

Benefits include:

  • Precise 1°F Control Accuracy
  • Superior System Reliability
  • Enhanced Part Quality & Gate Vestige
  • Improved Part Consistency
  • Reduced Scrap
  • Lower Power Consumption
  • Maximized Profit Margins

APS is standard on ALL TempMaster controllers. Visit our website to learn more.