注塑機變頻器改造常見問題

1、解決生產周期可能延長的辦法

在(zai)(zai)對(dui)注(zhu)塑機(ji)進(jin)行變(bian)頻(pin)改造時(shi)，可能經常會(hui)發現，生產(chan)周(zhou)期(qi)在(zai)(zai)變(bian)頻(pin)工(gong)作時(shi)會(hui)慢(man)0.3s~1.2s。且變(bian)頻(pin)器功率越(yue)(yue)大，產(chan)品(pin)工(gong)況越(yue)(yue)復雜，周(zhou)期(qi)就會(hui)相應地增加(jia)。這主要(yao)是由(you)于在(zai)(zai)不(bu)同(tong)工(gong)序段(duan)切換時(shi)，變(bian)頻(pin)器需(xu)要(yao)根據各(ge)工(gong)序所需(xu)要(yao)的不(bu)同(tong)壓力、量而不(bu)斷改變(bian)輸出頻(pin)率，而使(shi)電機(ji)經常處于加(jia)減(jian)速過程中。

盡管變頻器的加(jia)(jia)減速時(shi)(shi)(shi)間可(ke)(ke)調(diao)得很(hen)短，但相比工(gong)頻(pin)(pin)運行時(shi)(shi)(shi)電磁閥(fa)通斷(duan)速度有(you)一定的滯后，這(zhe)就(jiu)導致了(le)相同工(gong)藝(yi)參數下(xia)變頻(pin)(pin)控(kong)制時(shi)(shi)(shi)單位(wei)加(jia)(jia)工(gong)周期有(you)所延長，生產效率受(shou)到一定影(ying)響。對于(yu)這(zhe)個(ge)問(wen)題(ti)，一方面，要求選用的變頻(pin)(pin)器有(you)很(hen)好的動態響應(ying)性能(neng)(neng)，以盡量(liang)縮短響應(ying)時(shi)(shi)(shi)間；另(ling)一方面，可(ke)(ke)以根據(ju)實(shi)際情況，調(diao)整(zheng)注塑機(ji)的部分工(gong)藝(yi)參數，如加(jia)(jia)大壓(ya)力設定值等。當然，也(ye)可(ke)(ke)以對液(ye)壓(ya)系(xi)統和(he)控(kong)制系(xi)統進(jin)行改(gai)進(jin)來(lai)解決問(wen)題(ti)。例如，工(gong)頻(pin)(pin)時(shi)(shi)(shi)注塑機(ji)在液(ye)壓(ya)系(xi)統設計要考慮到液(ye)壓(ya)沖擊帶(dai)來(lai)的危(wei)害(hai)，在液(ye)壓(ya)回路上(shang)采用很(hen)多緩沖回路。如果(guo)能(neng)(neng)提高液(ye)壓(ya)回路反(fan)應(ying)時(shi)(shi)(shi)間就(jiu)可(ke)(ke)以彌補(bu)變頻(pin)(pin)加(jia)(jia)速過程帶(dai)來(lai)的滯后。而對于(yu)變頻(pin)(pin)器控(kong)制系(xi)統，如果(guo)能(neng)(neng)采用流(liu)量(liang)和(he)壓(ya)力兩路信號控(kong)制，也(ye)能(neng)(neng)夠較好地(di)解決這(zhe)個(ge)問(wen)題(ti)。

2、壓力不夠的原因及相應措施

個別情況下，由于機器(qi)采用的元件(jian)質(zhi)量不(bu)過(guo)關，或保(bao)養不(bu)好，液(ye)(ye)壓(ya)(ya)回(hui)路中個別液(ye)(ye)壓(ya)(ya)元件(jian)磨損，導致自(zi)身的壓(ya)(ya)力一(yi)流量特性有(you)所下降，造成控(kong)制(zhi)壓(ya)(ya)力隨流量的變(bian)化較(jiao)大(da)。這(zhe)時(shi)(shi)表現出(chu)有(you)時(shi)(shi)夠力而(er)有(you)時(shi)(shi)不(bu)夠力的現象(xiang)。工頻生產時(shi)(shi)由于流量恒定(ding)，因(yin)此(ci)問(wen)題(ti)沒有(you)被暴露出(chu)來。采用變(bian)頻控(kong)制(zhi)時(shi)(shi)就會表現出(chu)壓(ya)(ya)力不(bu)夠。

為了解決這(zhe)一(yi)(yi)問題，采(cai)用兩種方法：一(yi)(yi)種是通(tong)過調(diao)整注(zhu)塑機的工(gong)(gong)藝參數，將變頻(pin)工(gong)(gong)作時注(zhu)塑機的壓力(li)(li)流量設(she)定得比工(gong)(gong)頻(pin)時高一(yi)(yi)些(xie)；另(ling)一(yi)(yi)種是從控制方法上想辦(ban)法，例如采(cai)用基(ji)于(yu)速度環節的壓力(li)(li)閉環控制，保證壓力(li)(li)滿(man)足要求。

該圖片由注冊用戶"小含"提供，版權聲明反饋

3、應對變頻器對注塑機干擾的措施

由于變頻器在(zai)工作時輸入、輸出電流中都會(hui)有一定量高次諧(xie)波，會(hui)對(dui)注塑(su)機的控制系統(tong)產生干擾，嚴重時可能影響(xiang)到注塑(su)機的正常(chang)動作。對(dui)此，可采取(qu)以下措施：

(1)在輸(shu)(shu)入側(ce)和輸(shu)(shu)出側(ce)加(jia)裝變頻器(qi)(qi)專用濾波器(qi)(qi)、電抗器(qi)(qi)等以減(jian)小高次(ci)諧(xie)波電流(liu)；

(2)控制信號線使用屏蔽(bi)電纜，并把屏蔽(bi)層一端(duan)接(jie)到變頻器的公共輸入端(duan)子(zi)上；

(3)變頻器(qi)的輸入、輸出電纜(lan)與控制信號線分開走線，它們之間應該至少保(bao)證20cm以上(shang)的距離且盡可(ke)能遠；

(4)減(jian)少變頻(pin)器的載(zai)波(bo)頻(pin)率；

(5)同一電(dian)源下(xia)的其他設備(bei)最(zui)好能做到(dao)隔離供電(dian)。

4、實際應用中發現的問題

節能變頻器的使用(yong)效(xiao)果，與(yu)注射工藝參數設定(ding)密切相關(guan)。其中涉及(ji)塑料制品的重量與(yu)注塑機的鎖模力問題。

(1)制品的(de)重量(liang)大，應由相應較大的(de)鎖模(mo)(mo)力(li)和(he)較大注射(she)量(liang)的(de)注塑(su)機進行加工(gong)（一(yi)般(ban)是(shi)(shi)在300噸(dun)級以上）。這類制品的(de)加工(gong)成型周期較長(chang)，特(te)別是(shi)(shi)冷卻階(jie)段尤為突出，注射(she)動(dong)作(zuo)時要有可(ke)靠的(de)鎖模(mo)(mo)力(li)和(he)瞬時增壓力(li)。通(tong)過一(yi)些實(shi)際使用(yong)，進行變頻(pin)調速(su)的(de)定量(liang)泵均能滿足這種工(gong)況，并使變頻(pin)調速(su)的(de)節(jie)能作(zuo)用(yong)得到充分發揮(hui)。

(2)對于(yu)加工(gong)全是小(xiao)型制品(pin)的(de)注(zhu)塑廠(chang)，最大的(de)注(zhu)塑機鎖模(mo)力不(bu)超過180t，工(gong)藝(yi)參(can)數(shu)設(she)定幾乎沒有冷卻過程，節能效果不(bu)顯著(zhu)。

注塑機改造中使用變頻器的好處

1、調速節能

根據(ju)注塑(su)機(ji)的(de)(de)(de)(de)工(gong)(gong)藝(yi)要求，把(ba)總壓閥、低(di)(di)壓閥、一(yi)壓閥、二壓閥的(de)(de)(de)(de)開關信號(hao)經(jing)轉換后加在變(bian)(bian)(bian)頻(pin)(pin)器(qi)的(de)(de)(de)(de)輸入端作為變(bian)(bian)(bian)頻(pin)(pin)器(qi)的(de)(de)(de)(de)頻(pin)(pin)率給(gei)定信號(hao)，變(bian)(bian)(bian)頻(pin)(pin)器(qi)通(tong)過對其進行實(shi)時采樣并通(tong)過CPU處理，使(shi)輸出(chu)頻(pin)(pin)率隨比例(li)閥的(de)(de)(de)(de)模擬信號(hao)成線形變(bian)(bian)(bian)化，在需要壓力和流量較小(xiao)的(de)(de)(de)(de)工(gong)(gong)藝(yi)過程中使(shi)電(dian)機(ji)轉速降(jiang)低(di)(di)，從而降(jiang)低(di)(di)電(dian)機(ji)的(de)(de)(de)(de)輸出(chu)功率，在冷卻和半成品(pin)置入過程中可以讓電(dian)機(ji)停(ting)轉，使(shi)電(dian)機(ji)在整(zheng)個(ge)負載范(fan)圍內的(de)(de)(de)(de)能量損耗達到最(zui)小(xiao)程度。

2、提高功率因數節能

無(wu)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)不但增加線損和設備的發熱，更主要的是因為功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)因數的降低(di)導(dao)致電網有功(gong)(gong)(gong)(gong)(gong)(gong)(gong)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)的降低(di)。由(you)公式S2=P2+Q2，Q=S*SINφ，P=S*COSφ，其中：S-視在功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)。Q-無(wu)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)，P-有功(gong)(gong)(gong)(gong)(gong)(gong)(gong)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)，COSφ-功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)因數。可(ke)知，當COSφ越大(da)，有功(gong)(gong)(gong)(gong)(gong)(gong)(gong)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)P越大(da)。普通定量泵注塑機COSφ值在0.6-0.8之間，而(er)使用(yong)變頻(pin)調(diao)速裝置后(hou)，由(you)于(yu)變頻(pin)器(qi)內(nei)濾波電容的補償(chang)作(zuo)用(yong)，使得COSφ≈1，從而(er)減小(xiao)了無(wu)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)損耗，增大(da)了電網的有功(gong)(gong)(gong)(gong)(gong)(gong)(gong)功(gong)(gong)(gong)(gong)(gong)(gong)(gong)率(lv)(lv)。

3、軟啟動節

由于原電(dian)(dian)機為直(zhi)接(jie)啟動(dong)(dong)(dong)或Y/△啟動(dong)(dong)(dong)，啟動(dong)(dong)(dong)電(dian)(dian)流(liu)(liu)等于(3-7)倍額定(ding)電(dian)(dian)流(liu)(liu)，這(zhe)樣會對機電(dian)(dian)設備和供電(dian)(dian)電(dian)(dian)網造成嚴重的(de)(de)沖(chong)擊(ji)，而且還(huan)會增加(jia)電(dian)(dian)網容量要(yao)求(qiu)，啟動(dong)(dong)(dong)時產生(sheng)的(de)(de)大(da)電(dian)(dian)流(liu)(liu)和震動(dong)(dong)(dong)對設備的(de)(de)使(shi)用壽命極為不(bu)利。而使(shi)用變頻(pin)節(jie)能裝置(zhi)后(hou)，利用變頻(pin)器(qi)的(de)(de)軟啟動(dong)(dong)(dong)功能將(jiang)使(shi)啟動(dong)(dong)(dong)電(dian)(dian)流(liu)(liu)從(cong)零開(kai)始(shi)，最(zui)大(da)值被限制在變頻(pin)器(qi)設置(zhi)的(de)(de)加(jia)速中電(dian)(dian)流(liu)(liu)限幅水平以(yi)內，一般(ban)不(bu)超過(guo)1.7倍額定(ding)電(dian)(dian)流(liu)(liu)，減輕了對電(dian)(dian)網的(de)(de)沖(chong)擊(ji)和對電(dian)(dian)網容量的(de)(de)要(yao)求(qiu)，延(yan)長了設備和模具的(de)(de)使(shi)用壽命。