很多零(ling)件待加(jia)(jia)(jia)(jia)工(gong)(gong)部位(wei)，不利于機床正常加(jia)(jia)(jia)(jia)工(gong)(gong)，如果不采用措施，會給加(jia)(jia)(jia)(jia)工(gong)(gong)帶來困難，增加(jia)(jia)(jia)(jia)輔助(zhu)加(jia)(jia)(jia)(jia)工(gong)(gong)時(shi)間，尺寸精度不易保證，加(jia)(jia)(jia)(jia)工(gong)(gong)質量受到影(ying)響。本文介紹加(jia)(jia)(jia)(jia)工(gong)(gong)某(mou)設備上的偏心套零(ling)件，通(tong)過夾具(ju)改變零(ling)件相對機床的位(wei)置(zhi)，利于機床加(jia)(jia)(jia)(jia)工(gong)(gong)，縮短輔助(zhu)時(shi)間，并保證零(ling)件質量。
該偏心套零件如圖1所示。零件材質45鋼，大批量生產。外圓直徑100mm，公差0～0.1mm，偏心孔直徑50mm，公差0～0.016mm，偏心距15mm，各部表面粗糙度值均為Ra＝1.6μm，厚度30mm。按照(zhao)常規方(fang)法(fa)加工是先車(che)外圓，然(ran)后找(zhao)正車(che)偏(pian)心(xin)(xin)孔。由于偏(pian)心(xin)(xin)孔的(de)中心(xin)(xin)找(zhao)正較困難，輔(fu)助時(shi)間較長，加工效(xiao)率低。另外
圖1 偏(pian)心(xin)套零(ling)件加工質量(liang)(liang)也存在問題，導(dao)致孔(kong)距超(chao)差(cha)，偏(pian)心(xin)孔(kong)尺(chi)寸精度超(chao)差(cha)，影響零(ling)件總體質量(liang)(liang)。為(wei)提高(gao)加工效(xiao)率和零(ling)件質量(liang)(liang)，決定設(she)計夾具，依靠夾具限制零(ling)件相對機床的(de)加工位置(zhi)，保證加工順利進行。
普(pu)通(tong)臥式(shi)(shi)車床三爪自定心(xin)(xin)(xin)卡盤正(zheng)常裝(zhuang)(zhuang)夾(jia)零件外圓，使零件上(shang)偏心(xin)(xin)(xin)孔的中心(xin)(xin)(xin)與(yu)普(pu)通(tong)臥式(shi)(shi)車床回轉(zhuan)中心(xin)(xin)(xin)偏離15mm，設計夾(jia)具(ju)，通(tong)過夾(jia)具(ju)限(xian)制，使零件安裝(zhuang)(zhuang)到夾(jia)具(ju)里，其偏心(xin)(xin)(xin)孔中心(xin)(xin)(xin)與(yu)普(pu)通(tong)臥式(shi)(shi)車床回轉(zhuan)中心(xin)(xin)(xin)重合，這樣(yang)就可以(yi)順利(li)加工偏心(xin)(xin)(xin)孔了。
夾具組裝如圖2所示。夾具體（見圖3）外圓為圓形，并加工成階梯形，供普通臥式車床三爪自定心卡盤卡爪裝夾用，夾具體其上加工階梯形偏心孔，偏心孔直徑100mm，公差0～0.035mm，與零件外圓φ1000-0.1mm相配合(he)，偏(pian)(pian)心(xin)(xin)(xin)孔(kong)中(zhong)心(xin)(xin)(xin)與夾(jia)(jia)具體中(zhong)心(xin)(xin)(xin)偏(pian)(pian)心(xin)(xin)(xin)15mm，偏(pian)(pian)心(xin)(xin)(xin)孔(kong)底(di)部留(liu)(liu)直徑85mm止口(kou)，用(yong)于限制零(ling)(ling)件(jian)位置。偏(pian)(pian)心(xin)(xin)(xin)孔(kong)深度(du)28mm，低于零(ling)(ling)件(jian)厚度(du)30mm，保證夾(jia)(jia)緊(jin)螺(luo)母擰緊(jin)后直接接觸零(ling)(ling)件(jian)表面(mian)(mian)(mian)。偏(pian)(pian)心(xin)(xin)(xin)孔(kong)最大直徑是M110×2mm細牙螺(luo)紋孔(kong)，與夾(jia)(jia)緊(jin)空心(xin)(xin)(xin)螺(luo)母配合(he)，用(yong)于夾(jia)(jia)緊(jin)零(ling)(ling)件(jian)。夾(jia)(jia)緊(jin)空心(xin)(xin)(xin)螺(luo)母厚度(du)方向(xiang)外表面(mian)(mian)(mian)為階梯形，六方形絲扣(kou)組成。中(zhong)間為空心(xin)(xin)(xin)孔(kong)，將零(ling)(ling)件(jian)待加工部位留(liu)(liu)出。夾(jia)(jia)具體采用(yong)45鋼，調質熱處(chu)理(li)，表面(mian)(mian)(mian)淬火熱處(chu)理(li)，增加耐磨性(xing)。表面(mian)(mian)(mian)加工要(yao)光滑，利用(yong)找正調整。
圖2 車加工偏心套夾(jia)具(ju)
1.零件 2.三爪自定(ding)心卡盤 3.夾(jia)具(ju)體4.夾(jia)緊空心螺(luo)母
圖3 夾具體零件
首先將夾具(ju)(ju)體(ti)安裝(zhuang)在普通(tong)臥(wo)式車床三爪自定(ding)(ding)(ding)心卡盤上，找正(zheng)調整，保證夾具(ju)(ju)體(ti)中(zhong)心與普通(tong)臥(wo)式車床回(hui)轉(zhuan)(zhuan)中(zhong)心重合，夾具(ju)(ju)體(ti)平面與普通(tong)臥(wo)式車床回(hui)轉(zhuan)(zhuan)中(zhong)心軸線垂直；將加工完成(cheng)(cheng)(cheng)外圓(yuan)和(he)厚度尺寸的零件(jian)(jian)(jian)安裝(zhuang)在夾具(ju)(ju)體(ti)偏(pian)心孔(kong)(kong)(kong)里(li)，夾緊空心螺(luo)母安裝(zhuang)在夾具(ju)(ju)體(ti)螺(luo)紋孔(kong)(kong)(kong)里(li)，擰緊鎖緊零件(jian)(jian)(jian)。零件(jian)(jian)(jian)外圓(yuan)表(biao)面與夾具(ju)(ju)體(ti)偏(pian)心孔(kong)(kong)(kong)表(biao)面構(gou)成(cheng)(cheng)(cheng)軸孔(kong)(kong)(kong)定(ding)(ding)(ding)位(wei)(wei)，可以(yi)認為組成(cheng)(cheng)(cheng)4點(dian)(dian)定(ding)(ding)(ding)位(wei)(wei)，零件(jian)(jian)(jian)端(duan)面與夾具(ju)(ju)體(ti)偏(pian)心孔(kong)(kong)(kong)底(di)部止口構(gou)成(cheng)(cheng)(cheng)小(xiao)平面定(ding)(ding)(ding)位(wei)(wei)，組成(cheng)(cheng)(cheng)2點(dian)(dian)定(ding)(ding)(ding)位(wei)(wei)，總體(ti)構(gou)成(cheng)(cheng)(cheng)6點(dian)(dian)定(ding)(ding)(ding)位(wei)(wei)。空心螺(luo)母與夾具(ju)(ju)體(ti)絲扣構(gou)成(cheng)(cheng)(cheng)螺(luo)紋夾緊。
零(ling)(ling)(ling)件(jian)固定后(hou)進(jin)(jin)行加工。零(ling)(ling)(ling)件(jian)偏心孔(kong)(kong)加工完成后(hou)，卸下(xia)(xia)螺(luo)母(mu)，勾(gou)住零(ling)(ling)(ling)件(jian)偏心孔(kong)(kong)，卸下(xia)(xia)零(ling)(ling)(ling)件(jian)。夾具(ju)體固定不(bu)動，安裝下(xia)(xia)1個零(ling)(ling)(ling)件(jian)，再一次擰緊空心螺(luo)母(mu)即可進(jin)(jin)行下(xia)(xia)1次加工。往(wang)復循環，直(zhi)至全部加工完成。
使用該(gai)夾(jia)具加(jia)工偏心(xin)套零件(jian)，僅需(xu)1次找正(zheng)，后續加(jia)工無需(xu)再找正(zheng)，大(da)大(da)縮短輔助找正(zheng)時間。夾(jia)具安裝(zhuang)到(dao)機床上(shang)后，僅需(xu)利(li)用空心(xin)螺母(mu)夾(jia)緊零件(jian)，后續加(jia)工無需(xu)用三爪自定心(xin)卡盤裝(zhuang)夾(jia)，夾(jia)緊方式簡(jian)單(dan)易行。利(li)用該(gai)夾(jia)具加(jia)工，操作方便、可靠。通過大(da)批(pi)量加(jia)工，零件(jian)尺寸精度和表面粗糙度完全(quan)合格，質量得到(dao)保證。