模具(ju)尺寸的確定方(fang)法

模(mo)具型腔(qiang)和(he)型芯的(de)(de)(de)加工尺(chi)(chi)(chi)(chi)寸(cun)除了(le)通過D=M(1+S)公(gong)式(shi)計算基本尺(chi)(chi)(chi)(chi)寸(cun)之外，還有(you)一(yi)個加工公(gong)差(cha)的(de)(de)(de)問題。按照慣例，模(mo)具的(de)(de)(de)加工公(gong)差(cha)為塑(su)(su)件(jian)公(gong)差(cha)的(de)(de)(de)1/3。但由于塑(su)(su)料(liao)收縮(suo)率范(fan)圍(wei)和(he)穩定(ding)(ding)性各(ge)有(you)差(cha)異，首(shou)先(xian)必須合(he)理化確定(ding)(ding)不同塑(su)(su)料(liao)所成形塑(su)(su)件(jian)的(de)(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)差(cha)。即由收縮(suo)率范(fan)圍(wei)較(jiao)(jiao)大或收縮(suo)率穩定(ding)(ding)較(jiao)(jiao)差(cha)塑(su)(su)料(liao)成形塑(su)(su)件(jian)的(de)(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)差(cha)應取得大一(yi)些。否則(ze)就可能出現(xian)大量尺(chi)(chi)(chi)(chi)寸(cun)超差(cha)的(de)(de)(de)廢品。 為此，各(ge)國(guo)(guo)對塑(su)(su)料(liao)件(jian)的(de)(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)差(cha)專門制(zhi)訂了(le)國(guo)(guo)家(jia)標(biao)準或行業(ye)標(biao)準。中國(guo)(guo)也曾制(zhi)訂了(le)部級專業(ye)標(biao)準。但大都無相應的(de)(de)(de)模(mo)具型腔(qiang)的(de)(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)差(cha)。德(de)國(guo)(guo)國(guo)(guo)家(jia)標(biao)準中專門制(zhi)訂了(le)塑(su)(su)件(jian)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)差(cha)的(de)(de)(de)DIN16901標(biao)準及相應的(de)(de)(de)模(mo)具型腔(qiang)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)差(cha)的(de)(de)(de)DIN16749標(biao)準。此標(biao)準在世界上具有(you)較(jiao)(jiao)大的(de)(de)(de)影響(xiang)，因而可供塑(su)(su)料(liao)模(mo)具行業(ye)參考。

關于塑件的尺寸公差和允許偏差

為了(le)合(he)理地(di)確定(ding)不同收(shou)縮(suo)特性(xing)材(cai)料所成形塑(su)件的(de)尺(chi)寸公(gong)差，讓(rang)標準引(yin)入了(le)成形收(shou)縮(suo)差△VS這一概(gai)念。 △VS＝VSR_VST(4)

式中： VS－成形收(shou)(shou)縮(suo)差　VSR－熔料(liao)流動方向的(de)成形收(shou)(shou)縮(suo)率　VST－與熔料(liao)流動垂直方向的(de)成形收(shou)(shou)縮(suo)率。

根據塑(su)料(liao)△VS值(zhi)，將各種塑(su)料(liao)的(de)(de)(de)收(shou)縮(suo)特(te)性(xing)分為(wei)4個組(zu)(zu)(zu)(zu)(zu)。△VS值(zhi)最(zui)(zui)(zui)小(xiao)的(de)(de)(de)組(zu)(zu)(zu)(zu)(zu)是(shi)(shi)高精(jing)度(du)組(zu)(zu)(zu)(zu)(zu)，以(yi)(yi)此(ci)(ci)類推，△VS值(zhi)最(zui)(zui)(zui)大的(de)(de)(de)組(zu)(zu)(zu)(zu)(zu)為(wei)低(di)精(jing)度(du)組(zu)(zu)(zu)(zu)(zu)。 并(bing)按(an)照基本尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)編制了精(jing)密(mi)技術、110、120、130、140、150和(he)(he)(he)160公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)組(zu)(zu)(zu)(zu)(zu)。并(bing)規定(ding)，用(yong)(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)特(te)性(xing)最(zui)(zui)(zui)穩定(ding)的(de)(de)(de)塑(su)料(liao)成(cheng)(cheng)(cheng)形(xing)(xing)塑(su)件(jian)(jian)(jian)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)可選(xuan)用(yong)(yong)(yong)(yong)(yong)(yong)110、120和(he)(he)(he)130組(zu)(zu)(zu)(zu)(zu)。用(yong)(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)特(te)性(xing)中(zhong)等穩定(ding)的(de)(de)(de)塑(su)料(liao)成(cheng)(cheng)(cheng)形(xing)(xing)塑(su)件(jian)(jian)(jian)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)選(xuan)用(yong)(yong)(yong)(yong)(yong)(yong)120、130和(he)(he)(he)140。如果(guo)用(yong)(yong)(yong)(yong)(yong)(yong)這類塑(su)料(liao)成(cheng)(cheng)(cheng)形(xing)(xing)塑(su)件(jian)(jian)(jian)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)選(xuan)用(yong)(yong)(yong)(yong)(yong)(yong)110組(zu)(zu)(zu)(zu)(zu)時，即可能出大量尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)超差(cha)(cha)(cha)(cha)(cha)(cha)(cha)塑(su)件(jian)(jian)(jian)。用(yong)(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)特(te)性(xing)較(jiao)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)的(de)(de)(de)塑(su)料(liao)成(cheng)(cheng)(cheng)形(xing)(xing)塑(su)件(jian)(jian)(jian)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)選(xuan)用(yong)(yong)(yong)(yong)(yong)(yong)130、140和(he)(he)(he)150組(zu)(zu)(zu)(zu)(zu)。用(yong)(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)特(te)性(xing)最(zui)(zui)(zui)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)的(de)(de)(de)塑(su)料(liao)成(cheng)(cheng)(cheng)形(xing)(xing)塑(su)件(jian)(jian)(jian)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)選(xuan)用(yong)(yong)(yong)(yong)(yong)(yong)140、150和(he)(he)(he)160組(zu)(zu)(zu)(zu)(zu)。 在使(shi)用(yong)(yong)(yong)(yong)(yong)(yong)此(ci)(ci)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)表(biao)時，還需注意以(yi)(yi)下各點。 表(biao)中(zhong)的(de)(de)(de)一般公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)用(yong)(yong)(yong)(yong)(yong)(yong)于不注明公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)。直接標注偏(pian)(pian)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)的(de)(de)(de)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)是(shi)(shi)用(yong)(yong)(yong)(yong)(yong)(yong)于對(dui)塑(su)件(jian)(jian)(jian)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)標注公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)的(de)(de)(de)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)帶(dai)。其上、下偏(pian)(pian)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)可設(she)計人員自行(xing)確定(ding)。例如公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)帶(dai)為(wei)0.8mm，則可以(yi)(yi)選(xuan)用(yong)(yong)(yong)(yong)(yong)(yong)以(yi)(yi)下各種上、下偏(pian)(pian)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)構成(cheng)(cheng)(cheng)。0.0;-0.8;±0.4;-0.2;-0.5等。 每一公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)組(zu)(zu)(zu)(zu)(zu)中(zhong)均有A、B兩組(zu)(zu)(zu)(zu)(zu)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)值(zhi)。其中(zhong)A是(shi)(shi)由模(mo)具(ju)(ju)零(ling)件(jian)(jian)(jian)組(zu)(zu)(zu)(zu)(zu)合形(xing)(xing)成(cheng)(cheng)(cheng)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)，增(zeng)加了模(mo)具(ju)(ju)零(ling)件(jian)(jian)(jian)對(dui)合處不密(mi)合所形(xing)(xing)成(cheng)(cheng)(cheng)的(de)(de)(de)錯(cuo)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)。此(ci)(ci)增(zeng)加值(zhi)為(wei)0.2mm。其中(zhong)B是(shi)(shi)直接由模(mo)具(ju)(ju)零(ling)件(jian)(jian)(jian)所決定(ding)的(de)(de)(de)尺(chi)(chi)(chi)寸(cun)(cun)(cun)(cun)。 精(jing)密(mi)技術是(shi)(shi)專門設(she)立的(de)(de)(de)一組(zu)(zu)(zu)(zu)(zu)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)值(zhi)，供具(ju)(ju)有高精(jing)度(du)要求(qiu)塑(su)件(jian)(jian)(jian)使(shi)用(yong)(yong)(yong)(yong)(yong)(yong)。 在此(ci)(ci)用(yong)(yong)(yong)(yong)(yong)(yong)塑(su)件(jian)(jian)(jian)公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)之前(qian)，首先必須知道所使(shi)用(yong)(yong)(yong)(yong)(yong)(yong)的(de)(de)(de)塑(su)料(liao)適用(yong)(yong)(yong)(yong)(yong)(yong)哪幾個公(gong)(gong)(gong)(gong)差(cha)(cha)(cha)(cha)(cha)(cha)(cha)組(zu)(zu)(zu)(zu)(zu)。

模具的制造公差

德國國家(jia)標準針對塑(su)(su)件(jian)公(gong)(gong)差(cha)制(zhi)(zhi)訂了(le)相應(ying)模(mo)具制(zhi)(zhi)造(zao)公(gong)(gong)差(cha)的標準DIN16749。該(gai)表中共設4種公(gong)(gong)差(cha)。不(bu)(bu)論(lun)(lun)何種材(cai)料(liao)的塑(su)(su)件(jian)，其中不(bu)(bu)注(zhu)明(ming)尺(chi)寸公(gong)(gong)差(cha)尺(chi)寸的模(mo)具制(zhi)(zhi)造(zao)公(gong)(gong)差(cha)均使用序(xu)號(hao)1的公(gong)(gong)差(cha)。具體(ti)公(gong)(gong)差(cha)值由基(ji)本(ben)尺(chi)寸范圍確(que)定。 不(bu)(bu)論(lun)(lun)何種材(cai)料(liao)塑(su)(su)件(jian)中等精度尺(chi)寸的模(mo)具制(zhi)(zhi)造(zao)公(gong)(gong)差(cha)為序(xu)號(hao)2的公(gong)(gong)差(cha)。不(bu)(bu)論(lun)(lun)何種材(cai)料(liao)塑(su)(su)件(jian)較高(gao)精度尺(chi)寸的模(mo)具制(zhi)(zhi)造(zao)公(gong)(gong)差(cha)為序(xu)號(hao)3的公(gong)(gong)差(cha)。精密技術相應(ying)的模(mo)具制(zhi)(zhi)造(zao)公(gong)(gong)差(cha)為序(xu)號(hao)4的公(gong)(gong)差(cha)。

可(ke)以(yi)合理(li)地(di)確定各(ge)種材料塑件的合理(li)公差和相應的模(mo)具(ju)制(zhi)造公差，這不(bu)僅給模(mo)具(ju)制(zhi)造帶來方便，還可(ke)以(yi)減少廢品，提高經濟效期益。