Heat Seal Band / Wire Burn-in:

Introduction: The heatsealing band is a key component in the control loop, since it is both a heating element and a sensor. The geometry of the heatsealing band is too complex to be discussed at length here. We shall therefore only refer to a few of the most important physical and electrical properties: The measuring principle applied for this system necessitates a heatsealing band alloy with a suitable temperature coefficient TCR, i.e. one whose resistance increases as the temperature rises. Too low a TCR leads to oscillation or uncontrolled heating. When heatsealing bands with a higher TCR are used, the controller must be calibrated for this. The first time the heatsealing band is heated to approximately 200…250°C, the standard alloy (Alloy-20) undergoes a once-only resistance change (burn-in effect). The cold resistance of the heatsealing band is reduced by approximately 2…3%. However, this at first glance slight resistance change results in a zero point error of 20…30°C. The zero point must therefore be corrected after a few heating cycles (Reference the following heat seal band burn-in steps. One very important design feature is the copper or silver-plating of the heatsealing band ends. Cold ends allow the temperature to be controlled accurately and increase the life of the PTFE coating and the heatsealing band.

Burn-in Steps:

If a new heatsealing band has been used, the zero point is first of all calibrated while the band is still cold by activating the "AUTOCAL" function on the controller. When the "AUTOCAL" function has finished, the controller outputs the preselected calibration temperature (default value: 20°C). Adjust the set point to approximately 250°C and press the "HAND" key (display in home position) to heat for approximately 1 second. After re-cooling, the controller usually indicates a value less than 20°C. Repeat the "AUTOCAL" function. The heatsealing band has now been burned in and the change in the alloy properties stabilized.

• Step #1
  Install new or replacement heat seal band.




• Step #2
  Activate the RES controller AUTOCAL function.




• Step #3
  To burn-in the heat seal band, set the RES controller heat sealing temperature to approximately 250°C, or 50°C higher than your maximum required heat sealing temperature.




• Step #4
  For RES panel mount controllers, (with the display in home position, displaying Set and Act temperatures) Press the "HAND" key to energize the heat seal band for approximately 1 second.




• Step #5
  Wait for the heat seal band to cool, the displayed measured ACTUAL temperature will usually display a value less than 20°C.




• Step #6
  Repeat the AUTOCAL function to complete the burn-in procedure.

Note: The burn-in effect described above does not occur if the heat sealing band has already been burned in, or thermally pretreated by the manufacturer.