Impulse sealing process

Simple and very tough

A technique to seal bags with waterproof and highly resistant seals.

Pulse sealing is usually used to seal materials such as polyethylene, polypropylene and any type of heat sealable material of a thickness from 20 to 500µ.

Single resistance impulse sealing is recommended for sealing thicknesses of below 2 x 150µ.

This technique is not recommended for bags with bellows; heat sealing will provide better results.

For sealing pouches with a greater thickness (up to 2 x 500µ) it is preferable to use bi-active impulse sealing.

The bag is then clamped between 2 sealing jaws equipped with resistors.

The principle of impulse sealing consists in supplying a resistance with a low voltage electric current while observing the following parameters:

• The sealing temperature must be sufficient to fuse the 2 thicknesses of material to be sealed.
• The resistor must be isolated from the material to be sealed by a teflon-coated fabric product to prevent it from adhering and sticking to the resistor.
• The sealing time must be adjusted so that the fusion of the sealing thicknesses is correct, neither too high a level, because of the risk of burning the seal, nor too low a level, because the seal will yield and the bag cannot be closed.
• The cooling time after sealing is necessary, in order to maintain the pressure on the material to be sealed while lowering its temperature to obtain an optimal fusion.
  Cooling for a period after sealing is necessary, in order to maintain the pressure on the material to be sealed while lowering its temperature to obtain optimal fusion.
  The said cooling time is necessary and must be observed in order to ensure a good weld quality.
  This time period must be observed without fail to avoid premature burning of the teflon and to properly crush the material to obtain the full sealing width.
  The length of time can be programmed for magnetic and pneumatic versions by means of an electromagnet or cylinder.
• Sealing pressure must also be sufficient during sealing and cooling times. Pressure is ensured either manually by the operator or automatically on pneumatic versions.

The time of a complete sealing cycle (sealing + cooling) is generally between 2 and 6 seconds.

The welding jaw can be closed manually or with a mechanical, electrical or pneumatic pedal.

Pneumatic versions require a supply of compressed air at 6 bars and are the most efficient. The pneumatic cylinder both lowers the sealing arm and ensures correct pressure.

Dilation of resistors during heating is neutralized on all our sealers by a tensioning device that allows straight seals to be obtained and enhances resistor durability.

Sealing widths available on our equipment are 2 mm, 5 mm or 10 mm, depending on the model.

Width sealing is more attractive aesthetically than waterproofing.

A good sealing width of 2 mm will be more waterproof than a bad seal of 5 or 10 mm!