熱封(feng)時間主要由制袋(dai)機的速度決(jue)定。
速度快，熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)時(shi)間就短；速度慢，熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)時(shi)間就長(chang)(chang)。熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)時(shi)間也是影(ying)響(xiang)(xiang)(xiang)焊縫封(feng)(feng)(feng)(feng)(feng)(feng)(feng)合(he)強(qiang)度和(he)外(wai)觀的一(yi)個關(guan)鍵因(yin)素。相同的熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)溫(wen)度和(he)壓力下，熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)時(shi)間長(chang)(chang)，則熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)層熔(rong)合(he)更充(chong)分，結合(he)更牢固(gu)；但(dan)熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)時(shi)間太(tai)長(chang)(chang)，容易造(zao)成焊縫起皺變形，影(ying)響(xiang)(xiang)(xiang)平整(zheng)度和(he)外(wai)觀。熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)后的焊縫若冷(leng)卻不好，不但(dan)會影(ying)響(xiang)(xiang)(xiang)焊疑的外(wai)觀平整(zheng)度，而且對(dui)熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)強(qiang)度有一(yi)定的影(ying)響(xiang)(xiang)(xiang)，冷(leng)卻過程就是通過在(zai)一(yi)定的壓力下，用較低的溫(wen)度對(dui)剛熔(rong)融熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)后的焊縫進行定形。因(yin)此，壓力不夠，冷(leng)卻和(he)循(xun)環不暢(chang)，循(xun)環量不夠，水溫(wen)太(tai)高或冷(leng)卻不及時(shi)，都(dou)會致(zhi)使冷(leng)卻不良，熱(re)(re)封(feng)(feng)(feng)(feng)(feng)(feng)(feng)強(qiang)度降(jiang)低。