模具尺(chi)寸的(de)確(que)定方法

模(mo)(mo)具型(xing)腔(qiang)和型(xing)芯的(de)加(jia)(jia)工尺(chi)(chi)寸(cun)(cun)(cun)除了(le)通過D=M(1+S)公式(shi)計算基本尺(chi)(chi)寸(cun)(cun)(cun)之外，還有(you)(you)一個加(jia)(jia)工公差(cha)的(de)問題。按照(zhao)慣例，模(mo)(mo)具的(de)加(jia)(jia)工公差(cha)為塑(su)件(jian)(jian)公差(cha)的(de)1/3。但由于塑(su)料(liao)收縮(suo)率(lv)(lv)(lv)范(fan)圍和穩(wen)(wen)定性各(ge)有(you)(you)差(cha)異(yi)，首(shou)先必須合理化(hua)確定不同塑(su)料(liao)所(suo)成(cheng)形塑(su)件(jian)(jian)的(de)尺(chi)(chi)寸(cun)(cun)(cun)公差(cha)。即由收縮(suo)率(lv)(lv)(lv)范(fan)圍較大(da)(da)或收縮(suo)率(lv)(lv)(lv)穩(wen)(wen)定較差(cha)塑(su)料(liao)成(cheng)形塑(su)件(jian)(jian)的(de)尺(chi)(chi)寸(cun)(cun)(cun)公差(cha)應(ying)取得大(da)(da)一些。否則就(jiu)可能(neng)出現(xian)大(da)(da)量尺(chi)(chi)寸(cun)(cun)(cun)超差(cha)的(de)廢品。 為此(ci)，各(ge)國(guo)對(dui)塑(su)料(liao)件(jian)(jian)的(de)尺(chi)(chi)寸(cun)(cun)(cun)公差(cha)專門制訂了(le)國(guo)家(jia)標(biao)準或行(xing)業(ye)標(biao)準。中國(guo)也曾(ceng)制訂了(le)部級專業(ye)標(biao)準。但大(da)(da)都無(wu)相(xiang)應(ying)的(de)模(mo)(mo)具型(xing)腔(qiang)的(de)尺(chi)(chi)寸(cun)(cun)(cun)公差(cha)。德國(guo)國(guo)家(jia)標(biao)準中專門制訂了(le)塑(su)件(jian)(jian)尺(chi)(chi)寸(cun)(cun)(cun)公差(cha)的(de)DIN16901標(biao)準及相(xiang)應(ying)的(de)模(mo)(mo)具型(xing)腔(qiang)尺(chi)(chi)寸(cun)(cun)(cun)公差(cha)的(de)DIN16749標(biao)準。此(ci)標(biao)準在世界上(shang)具有(you)(you)較大(da)(da)的(de)影響，因而可供塑(su)料(liao)模(mo)(mo)具行(xing)業(ye)參(can)考。

關于塑件的尺寸公差和允許偏差

為了合理地確定不(bu)同收(shou)縮特(te)性材料(liao)所(suo)成形(xing)塑件(jian)的尺寸公差(cha)，讓標準引入了成形(xing)收(shou)縮差(cha)△VS這一概念(nian)。 △VS＝VSR_VST(4)

式中： VS－成(cheng)形收縮(suo)差　VSR－熔料流動方向(xiang)的(de)(de)成(cheng)形收縮(suo)率　VST－與熔料流動垂直方向(xiang)的(de)(de)成(cheng)形收縮(suo)率。

根據(ju)塑(su)(su)(su)(su)料△VS值(zhi)，將各(ge)(ge)種(zhong)塑(su)(su)(su)(su)料的(de)(de)收(shou)縮(suo)(suo)特(te)(te)(te)性分為4個組(zu)(zu)(zu)。△VS值(zhi)最小(xiao)的(de)(de)組(zu)(zu)(zu)是(shi)高精度(du)(du)組(zu)(zu)(zu)，以(yi)此類(lei)推，△VS值(zhi)最大的(de)(de)組(zu)(zu)(zu)為低精度(du)(du)組(zu)(zu)(zu)。 并(bing)按(an)照基本尺(chi)(chi)(chi)(chi)寸(cun)編制了(le)精密技(ji)術、110、120、130、140、150和160公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)組(zu)(zu)(zu)。并(bing)規定(ding)，用(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)(suo)特(te)(te)(te)性最穩定(ding)的(de)(de)塑(su)(su)(su)(su)料成(cheng)形塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)可選用(yong)(yong)(yong)(yong)(yong)110、120和130組(zu)(zu)(zu)。用(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)(suo)特(te)(te)(te)性中(zhong)等穩定(ding)的(de)(de)塑(su)(su)(su)(su)料成(cheng)形塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)選用(yong)(yong)(yong)(yong)(yong)120、130和140。如果用(yong)(yong)(yong)(yong)(yong)這類(lei)塑(su)(su)(su)(su)料成(cheng)形塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)選用(yong)(yong)(yong)(yong)(yong)110組(zu)(zu)(zu)時(shi)，即可能(neng)出大量尺(chi)(chi)(chi)(chi)寸(cun)超差(cha)塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)。用(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)(suo)特(te)(te)(te)性較差(cha)的(de)(de)塑(su)(su)(su)(su)料成(cheng)形塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)選用(yong)(yong)(yong)(yong)(yong)130、140和150組(zu)(zu)(zu)。用(yong)(yong)(yong)(yong)(yong)收(shou)縮(suo)(suo)特(te)(te)(te)性最差(cha)的(de)(de)塑(su)(su)(su)(su)料成(cheng)形塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)選用(yong)(yong)(yong)(yong)(yong)140、150和160組(zu)(zu)(zu)。 在使(shi)用(yong)(yong)(yong)(yong)(yong)此公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)表時(shi)，還需注(zhu)意以(yi)下(xia)各(ge)(ge)點。 表中(zhong)的(de)(de)一(yi)般公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)用(yong)(yong)(yong)(yong)(yong)于(yu)不注(zhu)明公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)。直接標注(zhu)偏(pian)差(cha)的(de)(de)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)是(shi)用(yong)(yong)(yong)(yong)(yong)于(yu)對(dui)(dui)塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)尺(chi)(chi)(chi)(chi)寸(cun)標注(zhu)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)的(de)(de)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)帶。其上、下(xia)偏(pian)差(cha)可設(she)計人員(yuan)自(zi)行確定(ding)。例(li)如公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)帶為0.8mm，則可以(yi)選用(yong)(yong)(yong)(yong)(yong)以(yi)下(xia)各(ge)(ge)種(zhong)上、下(xia)偏(pian)差(cha)構成(cheng)。0.0;-0.8;±0.4;-0.2;-0.5等。 每(mei)一(yi)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)組(zu)(zu)(zu)中(zhong)均有(you)A、B兩組(zu)(zu)(zu)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)值(zhi)。其中(zhong)A是(shi)由模具(ju)(ju)零(ling)件(jian)(jian)(jian)(jian)(jian)組(zu)(zu)(zu)合形成(cheng)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)，增加了(le)模具(ju)(ju)零(ling)件(jian)(jian)(jian)(jian)(jian)對(dui)(dui)合處(chu)不密合所(suo)形成(cheng)的(de)(de)錯差(cha)。此增加值(zhi)為0.2mm。其中(zhong)B是(shi)直接由模具(ju)(ju)零(ling)件(jian)(jian)(jian)(jian)(jian)所(suo)決(jue)定(ding)的(de)(de)尺(chi)(chi)(chi)(chi)寸(cun)。 精密技(ji)術是(shi)專門設(she)立的(de)(de)一(yi)組(zu)(zu)(zu)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)值(zhi)，供(gong)具(ju)(ju)有(you)高精度(du)(du)要求塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)使(shi)用(yong)(yong)(yong)(yong)(yong)。 在此用(yong)(yong)(yong)(yong)(yong)塑(su)(su)(su)(su)件(jian)(jian)(jian)(jian)(jian)公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)之前，首先必須知道所(suo)使(shi)用(yong)(yong)(yong)(yong)(yong)的(de)(de)塑(su)(su)(su)(su)料適用(yong)(yong)(yong)(yong)(yong)哪(na)幾(ji)個公(gong)(gong)(gong)(gong)(gong)(gong)差(cha)組(zu)(zu)(zu)。

模具的制造公差

德國國家標準針對塑件(jian)公(gong)(gong)(gong)差(cha)制(zhi)(zhi)訂了相應(ying)模具制(zhi)(zhi)造(zao)公(gong)(gong)(gong)差(cha)的(de)標準DIN16749。該表中(zhong)共設4種公(gong)(gong)(gong)差(cha)。不(bu)(bu)(bu)論(lun)何種材(cai)料的(de)塑件(jian)，其(qi)中(zhong)不(bu)(bu)(bu)注明尺(chi)(chi)寸公(gong)(gong)(gong)差(cha)尺(chi)(chi)寸的(de)模具制(zhi)(zhi)造(zao)公(gong)(gong)(gong)差(cha)均使用(yong)序號(hao)(hao)1的(de)公(gong)(gong)(gong)差(cha)。具體公(gong)(gong)(gong)差(cha)值由基本尺(chi)(chi)寸范圍確(que)定(ding)。 不(bu)(bu)(bu)論(lun)何種材(cai)料塑件(jian)中(zhong)等(deng)精(jing)度尺(chi)(chi)寸的(de)模具制(zhi)(zhi)造(zao)公(gong)(gong)(gong)差(cha)為序號(hao)(hao)2的(de)公(gong)(gong)(gong)差(cha)。不(bu)(bu)(bu)論(lun)何種材(cai)料塑件(jian)較(jiao)高精(jing)度尺(chi)(chi)寸的(de)模具制(zhi)(zhi)造(zao)公(gong)(gong)(gong)差(cha)為序號(hao)(hao)3的(de)公(gong)(gong)(gong)差(cha)。精(jing)密技術相應(ying)的(de)模具制(zhi)(zhi)造(zao)公(gong)(gong)(gong)差(cha)為序號(hao)(hao)4的(de)公(gong)(gong)(gong)差(cha)。

可以(yi)(yi)合理地確定各種材料塑件的合理公(gong)差(cha)和相應的模具制造(zao)公(gong)差(cha)，這不僅(jin)給模具制造(zao)帶來方(fang)便(bian)，還可以(yi)(yi)減少廢品(pin)，提高(gao)經濟效期(qi)益(yi)。