熱封時間主要由制袋(dai)機的速度決定。
速度快(kuai)，熱(re)(re)封(feng)(feng)(feng)時(shi)(shi)間就短(duan)；速度慢，熱(re)(re)封(feng)(feng)(feng)時(shi)(shi)間就長(chang)。熱(re)(re)封(feng)(feng)(feng)時(shi)(shi)間也是影(ying)響焊縫(feng)封(feng)(feng)(feng)合(he)強度和(he)(he)外觀(guan)的一(yi)個關鍵因素。相同(tong)的熱(re)(re)封(feng)(feng)(feng)溫(wen)度和(he)(he)壓(ya)力下，熱(re)(re)封(feng)(feng)(feng)時(shi)(shi)間長(chang)，則熱(re)(re)封(feng)(feng)(feng)層(ceng)熔合(he)更充分，結合(he)更牢固；但(dan)(dan)熱(re)(re)封(feng)(feng)(feng)時(shi)(shi)間太(tai)長(chang)，容易造成焊縫(feng)起(qi)皺變形(xing)，影(ying)響平整度和(he)(he)外觀(guan)。熱(re)(re)封(feng)(feng)(feng)后(hou)的焊縫(feng)若冷(leng)(leng)卻不(bu)(bu)好(hao)，不(bu)(bu)但(dan)(dan)會影(ying)響焊疑的外觀(guan)平整度，而且對(dui)(dui)熱(re)(re)封(feng)(feng)(feng)強度有(you)一(yi)定(ding)的影(ying)響，冷(leng)(leng)卻過(guo)程就是通過(guo)在一(yi)定(ding)的壓(ya)力下，用較(jiao)低的溫(wen)度對(dui)(dui)剛熔融熱(re)(re)封(feng)(feng)(feng)后(hou)的焊縫(feng)進行(xing)定(ding)形(xing)。因此，壓(ya)力不(bu)(bu)夠，冷(leng)(leng)卻和(he)(he)循環不(bu)(bu)暢，循環量不(bu)(bu)夠，水溫(wen)太(tai)高或冷(leng)(leng)卻不(bu)(bu)及時(shi)(shi)，都(dou)會致使冷(leng)(leng)卻不(bu)(bu)良，熱(re)(re)封(feng)(feng)(feng)強度降低。