What is the typical frictional thermal error in hot runner systems?

In hot runner systems, the frictional thermal error usually falls between +10°C and 30°C. The precise value, which is especially important in high-speed injection molding or micro-part molding, depends on the material viscosity, shear rate, runner size, and sensor response speed.

 

1. Principal Factors Affecting Frictional Heat Error

A factor

Contribution of Errors

Justification

Shear Rate > 10^s⁻¹ + 10^25°C

Significant heat generation and severe melt friction during high-speed filling

Materials with high viscosity (such as PC, ABS, and PA) +5~15°C

Strong internal friction and long molecule chains cause a more noticeable increase in temperature.

Runner Diameter < 2mm (Miniature Parts) +8~20°C

Localized temperature spikes result from heat buildup that is difficult to dissipate.

Response Time of the Sensor > 1s

Error in lag superposition

Misjudgment is made worse by the inability to promptly reflect fleeting temperature changes.

Real-world Example: In a medical catheter mold in Wuhan, the hot runner's surface temperature indicated 300°C at an injection speed of 300 mm/s, but the actual melt temperature was only 278°C, a divergence of 22°C, indicating that frictional heat was the primary cause.

 

2. Common Error Ranges for Various Application Situations

Type of Application

Common Error

Control Suggestions

Packaging with thin walls (high speed) +10~18°C

For adjustment, lower the temperature by 5 to 8°C.

Small-channel microfluidic chips +15~30°C

Utilize a fast response sensor in conjunction with melt temperature measurement.

Medium Shear Automotive Connectors +8–15°C

Adjust sensor placement to prevent nozzle tip

ABS/PC General Parts +10~20°C

Adapt PID parameters dynamically in accordance with the process curve

Note: This problem, which is readily mistaken for an inaccurate temperature control, is actually a process-temperature coupling mismatch rather than a system fault.

 

3. How Can the Impact of Friction Heaters Be Diminished? Optimize the position of the sensor installation by choosing the center portion of the main flow channel and avoiding high-shear areas (such as flow dividers and nozzle outlets);

Choose fast-responding sensors, such as exposed K-type probes or thin-film thermocouples (reaction time < 0.5s);

Add melt temperature verification by calibrating the hot runner display value and installing a melt temperature meter at the outlet;

Dynamic correction of process parameters: To counteract incorrect temperature reductions, raise the high-speed section's set temperature by 5 to 10°C.

The triple method of "position avoidance + fast sensing + melt verification" can reduce the impact of frictional heat mistakes, according to the safety principle.