How RESISTRON Works
The Sealing Band as a Temperature Sensor
At the beginning of each sealing cycle, the sealing band is cold.
RESISTRON measures the electrical resistance of the band before heating starts.
Because the resistance of the band material increases in a predictable manner with temperature, the sealing band itself acts as an integrated temperature sensor.
This eliminates the need for external thermocouples or sensors mounted on the sealing tool.
Closed-Loop Temperature Control
During the heating impulse, RESISTRON continuously measures voltage and current to calculate the actual temperature of the sealing band in real time.
The controller compares the measured temperature with the predefined target value and dynamically regulates the power output via the impulse transformer.
This creates a true closed-loop control system, ensuring that the sealing temperature is reached quickly and maintained accurately throughout the sealing phase.
Fast Impulse Heating, Rapid Cooling
Energy is supplied only for a short, precisely controlled impulse.
After the impulse, power is switched off completely, allowing the sealing band to cool rapidly.
This results in:
- Short cycle times
- Reduced heat transfer to surrounding machine components
- Extended sealing band lifetime
- Improved overall energy efficiency
Automatic Compensation for Process Variations
RESISTRON automatically compensates for:
- Changes in film thickness or material
- Ambient temperature fluctuations
- Product contact with the sealing tool
- Aging or resistance changes of the sealing band
This ensures stable, repeatable seal quality without the need for constant manual adjustment.
Sealing Bars and Heat-Seal Tools
RESISTRON technology is used in combination with precision-engineered impulse sealing bars, designed to ensure uniform pressure distribution, optimal heat transfer, and long service life.
ROPEX sealing bars are available in a wide range of configurations, including:
- Standard impulse sealing bars for flat sealing bands
- Tapered and reflex sealing bar designs for demanding film structures and higher sealing forces
- Seal-and-cut bars, combining sealing and cutting in a single process
- Custom 2D and 3D shaped sealing bars, adapted to complex packaging geometries
The sealing bar acts as the mechanical carrier for the sealing band and ensures:
- Exact alignment of the active sealing length
- Uniform pressure across the entire seal area
- Reliable electrical contact and stable resistance values
Correct selection of the sealing bar geometry and active sealing length is essential.
The active length should be as close as possible to the actual seal length of the package to ensure efficient energy transfer, fast response times, and optimal temperature control.
All sealing bars can be individually configured to match:
- Film type and thickness
- Sealing length and tool geometry
- Machine cycle time and duty cycle
- Electrical and mechanical installation constraints
System Components
A complete RESISTRON sealing system typically consists of:
- RESISTRON temperature controller
- Impulse transformer, matched to band length and power demand
- Current transformer for precise measurement
- Heat-sealing band or cutting element
(flat, tapered, reflex, beaded, 2D or 3D shaped) - Precision sealing bar or sealing tool
- Line filter for EMC compliance and stable operation
Each system is individually configured to match the application, sealing length, duty cycle, and machine layout.
Integrated Monitoring and Safety
RESISTRON continuously monitors the sealing circuit and automatically detects:
- Broken or damaged sealing bands
- Short circuits and wiring faults
- Overtemperature conditions
In the event of a fault, the system switches off immediately, protecting both the sealing tool and the machine.
Key Benefits of RESISTRON Technology
- Extremely precise temperature control
- Excellent repeatability and seal quality
- Energy-efficient impulse heating
- Fast heat-up and cool-down times
- Extended sealing band lifetime
- High machine availability and operational safety
Ideal for Modern Packaging Machines
RESISTRON impulse sealing systems are used worldwide in applications where precise temperature control and accurate measurement are essential for product quality and process stability, including:
- Horizontal and vertical form-fill-seal machines, where exact and repeatable sealing temperatures are required despite changing film materials, thicknesses, and cycle times
- Tray sealers and pouch sealers, where controlled heat input ensures uniform seals without overheating sensitive films or damaging product edges
- Medical and food packaging equipment, where precise, documented temperature control and reliable measurement are critical for seal integrity, hygiene, and regulatory compliance
- Custom sealing and cutting applications, where complex tool geometries or combined seal-and-cut functions require accurate, real-time temperature measurement directly in the sealing element
