There are no absolutely uniform values for PID parameters in hot runner temperature control systems, but initial reference ranges can be provided based on experience: Proportional gain Kp is typically set to 1.0~3.0 (or proportional band P=30%~60%), integral time Ti=60~300 seconds, and derivative time Td=15~60 seconds. Specific adjustments need to be made based on the hot runner structure, material properties, and heating power. For initial commissioning, it is recommended to start with Kp=2.0, Ti=180s, and Td=30s, and then fine-tune according to the response curve.
I.Empirical Reference Values for Common Systems
Different hot runner systems have different parameter ranges due to differences in heat capacity, heating method, and control accuracy. The following are recommended initial settings based on various practical applications:
System Type Kp (Proportional Gain) P (Proportional Band, %) Ti (Integral Time, s) Td (Derivative Time, s) Applicable Scenarios
Small Hot Runner (≤8 chambers) 2.0 ~ 3.0 30% ~ 50% 60 ~ 180 15 ~ 45 Fast response, low inertia, suitable for rapid tuning
Medium Hot Runner (8~16 chambers) 1.5 ~ 2.5 40% ~ 60% 120 ~ 300 30 ~ 60 Multi-zone temperature control, requires consideration of stability and response
Large Hot Runner (>16 chambers) 1.0 ~ 2.0 50% ~ 80% 180 ~ 600 45 ~ 90 High thermal inertia, prone to oscillation, conservative settings recommended
Needle Valve Hot Nozzle 1.8 ~ 2.8 35% ~ 55% 100 ~ 250 20 ~ 50 Frequent operation, requires suppression of periodic disturbances.
Internal heating hot runner: 2.5 ~ 4.0 25% ~ 40% 60 ~ 150 10 ~ 30 Concentrated heating, fast response, Kp can be higher.
Note:Relationship between Kp and P: P (proportional band) = 100 / Kp, for example, Kp = 2.0 corresponds to P = 50%.
Units of Ti and Td: The integral time Ti is in seconds (s). Some controllers use minutes (min). Pay attention to unit conversion (e.g., 5min = 300s).
Use the derivative term with caution: Excessive Td can amplify noise. It is recommended to first disable the D term to stabilize the PI, and then gradually add it.
II. Adjustment Recommendations Based on Materials and Processes
Different plastics have different processing temperatures and thermal stability, which will affect the selection of PID parameters:
|
Material Type |
Recommended Kp |
Recommended Ti(s) |
Characteristics |
|
ABS, PS |
2.0 ~ 2.8 |
120 ~ 240 |
Temperature sensitive, requires stable control |
|
PC, PMMA |
1.8 ~ 2.5 |
150 ~ 300 |
High-temperature processing, high thermal inertia |
|
PA6, PA66 |
2.2 ~ 3.0 |
90 ~ 180 |
High hygroscopicity, large melt temperature fluctuations |
|
PBT, PET |
1.6 ~ 2.4 |
100 ~ 200 |
Easily degradable, requires avoiding localized overheating |
III. Typical Brand Temperature Controller Default Values Reference
The factory default parameters of some intelligent temperature controllers can be used as a starting point for debugging:
XMT Series Temperature Controller: P=1.6 (Kp≈62.5), Ti=240s, Td=60s
Siemens S7-1200 PID_Temp: Supports self-tuning, typical Ti=0.1~1800s, Td=0.5~3min
Omron E5CC: Default P=50%, Ti=120s, Td=30s
Note: These default values are applicable to general scenarios and must be fine-tuned according to the actual system. They cannot be directly used for high-precision control.
IV. Usage Recommendations and Safety Boundaries
Initial Power-On Commissioning Procedure:
First, set to pure proportional control (Ti=∞, Td=0).
Start with Kp at 2.0 and observe the response.
If there is no oscillation, gradually increase to 2.5~3.0; if oscillation occurs, decrease Kp.
After stabilization, add integral control, adjusting Ti from 180s.
Finally, try adding derivative control, adjusting Td from 30s.
Avoid Common Pitfalls:
Kp too large → System oscillation
Ti too small → Integral saturation, severe overshoot
Td too large → Output jitter, amplified noise
Recommended Tools:
Use the temperature controller's built-in trend graph function to observe the curve.
Use SCADA or a data acquisition system to perform FFT spectrum analysis to identify sources of periodic fluctuations.
