In the actual production process, due to the influence of heat sealing pressure, bag making machine speed and composite substrate thickness, the actual heat sealing temperature is often higher than the melting temperature of heat sealing materials. The smaller the pressure of heat seal, the higher the temperature of heat seal, the faster the machine speed, and the thicker the surface material of composite film, the higher the temperature of heat seal.

熱封溫度若低于熱封材料的軟化點，則無論怎樣加大壓力或延熱封時間，均不能使熱封層真正封合。但是，如果熱封溫度過高，又極易損傷焊邊處的熱封材料，熔融擠出產生“根切”現象，大大降低了封口的熱封強度和復合袋子的耐沖擊性能。在實際制袋熱封過程中，熱封刀具的壓力常采用可旋轉彈簧來調整，調整過程一般刀具由兩個彈簧組成，分左、右兩邊，如果壓力影響熱封強度。、

If the heat sealing temperature is lower than the softening point of the heat sealing material, no matter how to increase the pressure or extend the heat sealing time, the heat sealing layer can not be really sealed. However, if the heat sealing temperature is too high, it is easy to damage the heat sealing material at the welding edge, resulting in "undercutting" phenomenon during melt extrusion, which greatly reduces the heat sealing strength of the seal and the impact resistance of the composite bag. In the actual bag making and heat sealing process, the pressure of the heat sealing tool is often adjusted by a rotatable spring. In the adjustment process, the tool is generally composed of two springs, which are divided into left and right sides. If the pressure affects the heat sealing strength. 

檢測方法則是：取一只正加工的復合袋仔細觀察縫跡，如果壓力均勻是不會產生氣泡等現象；另一種方法是，用長500px、寬75px、厚5000px專用光滑竹塊進行試驗，由于壓力不夠，強度低，往往出現漏破現象，所以均勻的壓力與溫度是降低強度低、分層現象的基本之一。

The detection method is: take a composite bag that is being processed and carefully observe the seam. If the pressure is uniform, there will be no bubbles; another method is to use a special smooth bamboo block with a length of 500px, a width of 75px and a thickness of 5000px for test. Due to insufficient pressure and low strength, leakage often occurs. Therefore, uniform pressure and temperature are one of the basic factors to reduce the phenomenon of low strength and delamination .

對于輕薄包裝袋、熱封壓力至少要達到2kg/cm2，而且隨著復合膜總厚度的增加而相應提高；若熱封壓力不足，兩層薄膜之間難以達到真正的熔合，導致局部熱封不好或難以消除夾在焊縫中間的氣泡，造成虛焊。但熱封壓力并非越大越好，應以不損傷焊邊為宜，因為在較高的熱封溫度時，焊邊的熱封材料已處于半熔融狀態，太大的壓力易擠走部分熱封料，使焊縫邊緣形成半切斷狀態。焊縫發脆，熱封強度降低。所以壓力的調節非常關鍵。

For the light and thin packaging bags, the heat sealing pressure should be at least 2kg / cm2, and it should be increased with the increase of the total thickness of the composite film; if the heat sealing pressure is insufficient, it is difficult to achieve real fusion between the two films, resulting in local poor heat sealing or difficult to eliminate the gas bubbles in the middle of the weld, resulting in false welding. However, the higher the heat sealing pressure is, the better. It is better not to damage the weld edge, because at a higher heat sealing temperature, the heat sealing material at the weld edge is already in a semi molten state. Too much pressure is easy to squeeze out part of the heat sealing material and make the weld edge form a semi cut-off state. The weld is brittle and the heat seal strength is reduced. So the regulation of pressure is very important.