Thermal system (heater bands & temperature sensors)
Article Index
The thermal system plays a considerable role in the optimal function of shut-off nozzles. Heating systems contain a heating unit, temperature sensors and the associated controllers.
The heater band should be durable and have sufficient power reserves. The temperature sensors must exhibit a fast response mode and a long service life. The system is determined by ist weakest factor. If a wrong heating system is implemented, this could perform unreliably and impair or detract from the performance of the nozzle substantially.
Thermal system comparison
| High performance heater band Type DGM | Mica heater band Type DGS | Mica heater band | |
| Power density | 10 W/cm2 | 3.5 W/cm2 | 3.5 W/cm2 |
| Max. Temperatur | 600°C | 350°C | 280°C |
| Cable | 3m wire netting, thermal insulation | 1.5m wire netting, thermal insulation | 1m wire netting |
| Cable outlet | Terminal block with cable protection | Terminal block with cable protection | Direct without protection |
| Calibration / installation | Tangential latches for optimal tension / screws | Tangential latches for optimal tension / screws | Folded sheet metal / screws |
| Construction | Plastic impervious, magnesium oxide isolation | Plastic impervious, mica isolation | Plastic impervious, mica isolation |
| Advantage | • high quality insulation materials • high performance sealing • optimal heat transfer • minimal deadweight heating • excellent controllability • mechanically stable construction • plastic impervious • high efficiency • minimal energy consumption • rust free steel cover • long service life |
• good cost / performance ratio • good heat transfer • good controllability • mechanically stable construction • plastic impervious • rust free steel cover • long service life |
• economical |
| Disadvantage | • initial cost • moisture sensitive • starting circuit required or slow heating for dehumidifying |
• under performance for technical plastics | • bad heat transfer due to insufficient clamping and irregular contact to the body • insufficient response due to low power • sensitive cable outlets • usually not plastic impervious resulting in short circuiting |
Summary:
For the processing of technical plastics, a high quality heater band is absolutely recommended. The good thermal performance and compact, mechanically stable construction allow for easier handling and increase process security in application. Machine downtimes due to insufficient heat transfer and defective thermal systems are considerably reduced.