HOW DO I MAKE A FUNCTIONING HEATSEAL JAW?
Heatseal jaw design is relatively simple. It is made even easier by the use of Jørgen Bork Electronic ApS components that are available to facilitate the construction. Good sealing depends upon equal and even contact between the jaws, for the full length of the jaws. This means that the jaw bars must be straight and evenly loaded to avoid bowing of the jaws during the sealing process. When building long jaws it may be necessary to utilize a supplementary bar as a stiffening back- up. Sealing is accomplished when the seal area cools, therefore, the ability of the jaw bar to absorb heat is important . Aluminum is usually used in heatseal bars because it has a high thermal conductivity, it is light, and it is easy to machine.
The force required to effect a good seal or cut is a function of the material composition, the band shape, the hardness of the back-up material, the hardness and thickness of the pad on the opposite jaw, and the desired result. We know of no means by which the required force can be calculated. Optimum results can only be attained by testing. As a starting point, one should set-up using a total force equal to 1kg/cm2.in. of heatseal band surface. More force may be needed to get a clean cut on hard materials or non-woven fabrics, as example, and less might be desirable on delicate materials.
HEATSEAL BAND TENSION
Heatseal bands expand when they are heated. Therefore, a means must be provided to take up the slack or the heatseal band will buckle and break prematurely. The heatseal band is also an electrical conductor so the band must be electrically insulated from the bar. The bar must, therefore, be fitted with end connector blocks that can provide tension on the band and remain electrically insulated. Jørgen Bork Electronic ApS can provide Jaw End Kits that can be conveniently mounted on the ends of the jaw bars to serve this function. Jørgen Bork Electronic ApS Jaw End Kits are designed to fit on to the ends of 10x60 mm., or larger bars. This is usually a convenient size and it provides a reasonable amount of heat sink capacity for most applications.
The face of the jaw bar must also be electrically insulated. This can be done with a variety of materials. The most convenient of these materials are adhesive backed to facilitate attachment. Teflon tape, Durit, and Siglaha are all available from Jørgen Bork Electronic ApS with self adhesive backing. The proper selection is a function of the sealing mode.
The opposite jaw bar of a set of heatseal jaw bars can be either heated or not, usually not. Either way the opposite jaw is usually faced with a silicone rubber strip that is covered with Teflon tape. It is important to have a resilient component on one of the two jaw bar faces in order to absorb the shock of fast moving jaws and to provide some forgiveness and compensate for minor misalignment or distortion of the bars.