CPQ-1叉車驅(qū)動(dòng)橋殼體加工工藝及夾具設(shè)計(jì)含6張CAD圖
CPQ-1叉車驅(qū)動(dòng)橋殼體加工工藝及夾具設(shè)計(jì)含6張CAD圖,cpq,叉車,驅(qū)動(dòng),殼體,加工,工藝,夾具,設(shè)計(jì),cad
外文文獻(xiàn)資料
Introduction of Machining
Have?a?shape?as?a?processing?method,?all?machining?process?for?the?production?of?the?most?commonly?used?and?most?important?method.?Machining?process?is?a?process?generated?shape,?in?this?process,?Drivers?device?on?the?workpiece?material?to?be?in?the?form?of?chip?removal.? Although?in?some?occasions,?the?workpiece?under?no?circumstances,?the?use?of?mobile?equipment?to?the?processing,?However,?the?majority?of?the?machining?is?not?only?supporting?the? workpiece?also?supporting?tools?and?equipment?to?complete.?
Machining?know?the?process?has?two?aspects.?Small?group?of?low-cost?production.?For? casting,?forging?and?machining?pressure,?every?production?of?a?specific?shape?of?the?workpie-ce,?even?a?spare?parts,?almost?have?to?spend?the?high?cost?of?processing.?Welding?to?rely?on ?the?shape?of?the?structure,?to?a?large?extent,?depend?on?effective?in?the?form?of?raw?materials.?In?general,?through?the?use?of?expensive?equipment?and?without?special?processing?conditions,?can?be?almost?any?type?of?raw?materials,?mechanical?processing?to?convert?the?raw?materials? processed?into?the?arbitrary?shape?of?the?structure,?as?long?as?the?external?dimensions?large? enough,?it?is?possible.?Because?of?a?production?of?spare?parts,?even?when?the?parts?and?structu-re?of?the?production?batch?sizes?are?suitable?for?the?original?casting,?Forging?or?pressure?proc-essing?to?produce,?but?usually?prefer?machining.?
Strict?precision?and?good?surface?finish,?Machining?the?second?purpose?is?the?establishment?of?the?high?precision?and?surface?finish?possible?on?the?basis?of.?Many?parts,?if?any?other ?means?of?production?belonging?to?the?large-scale?production,?Well?Machining?is?a?low-tolera-nce?and?can?meet?the?requirements?of?small?batch?production.?Besides,?many?parts?on?the ?production?and?processing?of?coarse?process?to?improve?its?general?shape?of?the?surface.?It?is ?only?necessary?precision?and?choose?only?the?surface?machining.?For?instance,?thread,?in? addition?to?mechanical?processing,?almost?no?other?processing?method?for?processing.Another?example?is?the?blacksmith?pieces?keyhole?processing,?as?well?as?training?to?be?conducted? immediately?after?the?mechanical?completion?of?the?processing.?
Primary?Cutting?Parameters?
Cutting?the?work?piece?and?tool?based?on?the?basic?relationship?between?the?following?four?elements?to?fully?describe:?the?tool?geometry,?cutting?speed,?feed?rate,?depth?and?penetration? of?a?cutting?tool.?
Cutting?Tools?must?be?of?a?suitable?material?to?manufacture,?it?must?be?strong,?tough,?hard?and?wear-resistant.?Tool?geometry?--?to?the?tip?plane?and?cutter?angle?characteristics?--?for? each?cutting?process?must?be?correct.?
Cutting?speed?is?the?cutting?edge?of?work?piece?surface?rate,?it?is?inches?per?minute?to?show.?In?order?to?effectively?processing,?and?cutting?speed?must?adapt?to?the?level?of?specific?parts?-?with?knives.?Generally,?the?more?hard?work?piece?material,?the?lower?the?rate.
?Progressive?Tool?to?speed?iscut?into?the?work?piece?speed.?If?the?work?piece?or?tool?for? rotating?movement,?feed?rate?per?round?over?the?number?of?inches?to?the?measurement.?When?the?work?piece?or?tool?for?reciprocating?movement?and?feed?rate?on?each?trip?through?the?measurement?of?inches.?Generally,?in?other?conditions,?feed?rate?and?cutting?speed?is?inversely ?proportional?to.?
Depth?of?penetration?of?a?cutting?tool?--?to?inches?dollars?--?is?the?tool?to?the?work?piece? distance.?Rotary?cutting?it?to?the?chip?or?equal?to?the?width?of?the?linear?cutting?chip?thickness.?Rough?than?finishing,?deeper?penetration?of?a?cutting?tool?depth.?
Wears?of?Cutting?Tool
We?already?have?been?processed?and?the?rattle?of?the?countless?cracks?edge?tool,?we?learn that?tool?wear?are?basically?three?forms?:?flank?wear,?the?former?flank?wear?and?V-Notch?wear.Flank?wear?occurred?in?both?the?main?blade?occurred?vice?blade.?On?the?main?blade,?shoulder?removed?because?most?metal?chip?mandate,?which?resulted?in?an?increase?cutting?force?and?cutting?temperature?increase,?If?not?allowed?to?check,?That?could?lead?to?the?work?piece?and?the? tool?vibration?and?provide?for?efficient?cutting?conditions?may?no?longer?exist.?Vice-bladed?on,?it?is?determined?work?piece?dimensions?and?surface?finish.?Flank?wear?size?of?7the?possible? failure?of?the?product?and?surface?finish?are?also?inferior.?In?most?actual?cutting?conditions,?as?the?principal?in?the?former?first?deputy?flank?before?flank?wear,?wear?arrival?enough,?Tool?will?be?effective,?the?results?are?made?unqualified?parts.?
As?Tool?stress?on?the?surface?uneven,?chip?and?flank?before?sliding?contact?zone?between stress,?in?sliding?contact?the?start?of?the?largest,?and?in?contact?with?the?tail?of?zero,?so?abrasive?wear?in?the?region?occurred.?This?is?because?the?card?cutting?edge?than?the?nearby?settlements?near?the?more?serious?wear,?and?bladed?chip?due?to?the?vicinity?of?the?former?flank?and?lost ?contact?wear?lighter.?This?results?from?a?certain?distance?from?the?cutting?edge?of?the?surface?formed?before?the?knife?point?Ma?pit,?which?is?usually?considered?before?wear.?Under?normal?circumstances,?this?is?wear?cross-sectional?shape?of?an?arc.?In?many?instances?and?for?the ?actual?cutting?conditions,?the?former?flank?wear?compared?to?flank?wear?light,?Therefore?flank?wear?more?generally?as?a?tool?failure?of?scale?signs.?But?because?many?authors?have?said?in ?the?cutting?speed?of?the?increase,?Maeto?surface?temperature?than?the?knife?surface?temperatures?have?risen?faster.?but?because?any?form?of?wear?rate?is?essentially?temperature?changes?by ?the?significant?impact.?Therefore,?the?former?usually?wear?in?high-speed?cutting?happen.
The?main?tool?flank?wear?the?tail?is?not?processed?with?the?work?piece?surface?in?contact, ?Therefore?flank?wear?than?wear?along?with?the?ends?more?visible,?which?is?the?most?common.?This?is?because?the?local?effect,?which?is?as?rough?on?the?surface?has?hardened?layer,?This ?effect?is?by?cutting?in?front?of?the?hardening?of?the?work?piece.?Not?just?cutting,?and?as ?oxidation?skin,?the?blade?local?high?temperature?will?also?cause?this?effect.?This?partial?wear ?normally?referred?to?as?pit?sexual?wear,?but?occasionally?it?is?very?serious.?Despite?the ?emergence?of?the?pits?on?the?Cutting?Tool?nature?is?not?meaningful?impact,?but?often?pits ?gradually?become?darker?If?cutting?continued?the?case,?then?there?cutter?fracture?crisis.?
If?any?form?of?sexual?allowed?to?wear,?eventually?wear?rate?increase?obviously?will?be?a?tool?to?destroy?failure?destruction,?that?will?no?longer?tool?for?cutting,?cause?the?work?piece?scrapped,?it?is?good,?can?cause?serious?damage?machine.?For?various?carbide?cutting?tools?and?for ?the?various?types?of?wear,?in?the?event?of?a?serious?lapse,?on?the?tool?that?has?reached?the?end?of?the?life?cycle.?But?for?various?high-speed?steel?cutting?tools?and?wear?belonging?to?the?non-uniformity?of?wear,?has?been?found?:?When?the?wear?and?even?to?allow?for?a?serious?lapse,the?most?meaningful?is?that?the?tool?can?re-mill?use,?of?course,?In?practice,?cutting?the?time?to?use ?than?the?short?time?lapse.?Several?phenomena?are?one?tool?serious?lapse?began?features?:?the?most?common?is?the?sudden?increase?cutting?force,?appeared?on?the?work?piece?burning?ring ?patterns?and?an?increase?in?noise.?
The?Effect?of?Changes?in?Cutting?Parameters?on?Cutting?Temperatures?
In?metal?cutting?operations?heat?is?generated?in?the?primary?and?secondary?deformation ?zones?and?this?results?in?a?complex?temperature?distribution?throughout?the?tool,?workpiece ?and?chip.?A?typical?set?of?isotherms?is?shown?in?figure?where?it?can?be?seen?that,?as?could?be ?expected,?there?is?a?very?large?temperature?gradient?throughout?the?width?of?the?chip?as?the ?workpiece?material?is?sheared?in?primary?deformation?and?there?is?a?further?large?temperature?in?the?chip?adjacent?to?the?face?as?the?chip?is?sheared?in?secondary?deformation.?This?leads?to ?a?maximum?cutting?temperature?a?short?distance?up?the?face?from?the?cutting?edge?and?a?small?distance?into?the?chip.?
Since?virtually?all?the?work?done?in?metal?cutting?is?converted?into?heat,?it?could?be?expected?that?factors?which?increase?the?power?consumed?per?unit?volume?of?metal?removed?will ?increase?the?cutting?temperature.?Thus?an?increase?in?the?rake?angle,?all?other?parameters ?remaining?constant,?will?reduce?the?power?per?unit?volume?of?metal?removed?and?cutting ?temperatures?will?reduce.?When?considering?increase?in?undeformed?chip?thickness?and ?cutting?speed?the?situation?is?more?comples.?An?increase?in?undeformed?chip?thickness?and ?cutting?speed?the?situation?is?more?complex.?An?increase?in?undeformed?chip?thickness?tends ?to?be?a?scale?effect?where?the?amounts?of?heat?which?pass?to?the?workpiece,?the?tool?and?chip?remain?in?fixed?proportions?and?the?changes?in?cutting?temperature?tend?to?be?small.?Increase in?cutting?speed,?however,?reduce?the?amount?of?heat?which?passes?into?the?workpiece?and ?this?increase?the?temperature?rise?of?the?chip?in?primary?deformation.?Further,?the?secondary ?deformation?zone?tends?to?be?smaller?and?this?has?the?effect?of?increasing?the?temperatures?in ?this?zone.?Other?changes?in?cutting?parameters?have?virtually?no?effect?on?the?power?consum-ed?per?unit?volume?of?metal?removed?and?consequently?have?virtually?no?effect?on?the?power ?consumed?per?unit?volume?of?metal?removed?and?consequently?have?virtually?no?effect?on?the?cutting?temperatures.?Since?it?has?been?shown?that?even?small?changes?in?cuttingtemperature?have?a?significant?effect?on?tool?wear?rate,?it?is?appropriate?to?indicate?how?cutting?temperatur-es?can?be?assessed?from?cutting?data.??
The?most?direct?and?accurate?method?for?measuring?temperatures?in?high-speed-steel cutting?tools?is?that?of?Wright&Trent?which?also?yields?detailed?information?on?temperature distributions?in?high-speed-steel?tools?which?relates?microstructural?changes?to?thermal?history.Trent?has?described?measurements?of?cutting?temperatures?and?temperature?distributions?for ?high-speed-steel?tools?when?machining?a?wide?range?of?workpiece?materials.?This?technique? has?been?further?developed?by?using?scanning?electron?microscopy?to?study?fine-scale?microstructural?changes?srising?from?over?tempering?of?the?tempered?martensitic?matrix?of?various? high-speed-steels.?This?technique?has?also?been?used?to?study?temperature?distributions?in ?both?high-speed-steel?single?point?turning?tools?and?twist?drills.?
Automatic?Fixture?Design?
Assembly?equipment?used?in?the?traditional?synchronous?fixture?put?parts?of?the?fixture ?mobile?center,?to?ensure?that?components?from?transmission?from?the?plane?or?equipment?plate?placed?after?removal?has?been?scheduled?for?position.?However,?in?certain?applications,?mobile?mandatory?parts?of?the?center?line,?it?may?cause?parts?or?equipment?damage.?When?parts? vulnerability?and?may?lead?to?a?small?vibration?abandoned,?or?when?their?location?is?by ?machine?spindle?or?specific?to?die,?Tolerance?again?or?when?the?request?is?a?sophisticated,?it? would?rather?let?the?fixture?to?adapt?to?the?location?of?parts,?and?not?the?contrary.?For?these ?tasks,?Elyria,?Ohio,?the?company?has?developed?Zaytran?a?general?non-functional?data ?synchronization?West?category?fixture.?Fixture?because?of?the?interaction?and?synchronization?devices?is?independent,?The?synchronous?device?can?use?sophisticated?equip-ment?to?replace?the?slip?without?affecting?the?fixture?force.?Fixture?specification?range?from ?0.2?inches?itinerary,?5?pounds?clamping?force?of?the?six-inch?trip,?400-inch?clamping?force.?
The?characteristics?of?modern?production?is?becoming?smaller?and?smaller?quantities?and ?product?specifications?biggest?changes.?Therefore,?in?the?final?stages?of?production,?assembly?of?production,?quantity?and?product?design?changes?appear?to?be?particularly?vulnerable.?This?situation?is?forcing?many?companies?to?make?greater?efforts?to?rationalize?the?extensive reform?and?the?previously?mentioned?case?of?assembly?automation.?Despite?flexible?fixture?behind?the?rapid?development?of?flexible?transport?and?handling?devices,?such?as?backward?in ?the?development?of?industrial?robots,?it?is?still?expected?to?increase?the?flexibility?fixture.?In ?fact?the?important?fixture?devices?--?the?production?of?the?devices?to?strengthen?investment?on?the?fixture?so?that?more?flexibility?in?economic?support?holders.??
According?to?their?flexibility?and?fixture?can?be?divided?into?:?special?fixture,?the?fixture ?combinations,?the?standard?fixture,?high?flexible?fixture.?Flexible?fixture?on?different?parts?of ?their?high?adaptability?and?the?few?low-cost?replacement?for?the?characteristic.??
Forms?can?transform?the?structure?of?the?flexible?fixture?can?be?installed?with?the?change?of?structure?components?(such?as?needle?cheek?plate,?Multi-chip?components?and?flake?cheek ?plate),?a?non-standard?work?piece?gripper?or?clamping?elements?(for?example:?commencementstandard?with?a?clamping?fixture?and?mobile?components?fixture?supporting?documents),?or ?with?ceramic?or?hardening?of?the?intermediary?substances?(such?as:?Mobile?particle?bed?fixture?and?heat?fixture?tight?fixture).?To?production,?the?parts?were?secured?fixture,?the?need?to ?generate?clamping?function,?its?fixture?with?a?few?unrelated?to?the?sexual?submissive?steps?:?
According?to?the?processing?was?part?of?that?foundation?and?working?characteristics?to?determine?the?work?piece?fixture?in?the?required?position,?then?need?to?select?some?stability?flat ?combination,?These?constitute?a?stable?plane?was?fixed?in?the?work?piece?fixture?set?position ?on?the?clamp-profile?structure,?all?balanced?and?torque,?it?has?also?ensured?that?the?work ?features?close?to?the?work?piece.?Finally,?it?must?be?calculated?and?adjusted,?assembly?or ?disassembly?be?standard?fixture?components?required?for?the?position,?so?that?the?work?piece ?firmly?by?clamping?fixture?in?China.?In?accordance?with?this?procedure,?the?outline?fixture ?structure?and?equipped?with?the?planning?and?recording?process?can?be?automated?control.?
Structural?modeling?task?is?to?produce?some?stable?flat?combination,?Thus,?these?plane?of the?work?pieces?clamping?force?and?will?fixture?stability.?According?to?usual?practice,?this?task?can?be?human-machine?dialogue?that?is?almost?completely?automated?way?to?completion.?
中文翻譯
機(jī)械加工介紹
作為產(chǎn)生形狀的一種加工方法,機(jī)械加工是所有制造過程中最普遍使用的而且是最重要的方法。機(jī)械加工過程是一個(gè)產(chǎn)生形狀的過程,在這過程中,驅(qū)動(dòng)裝置使工件上的一些材料以切屑的形式被去除。盡管在某些場(chǎng)合,工件無承受的情況下,使用移動(dòng)式裝備來實(shí)現(xiàn)加工,但大多數(shù)的機(jī)械加工是通過既支承工件又支承刀具的裝備來完成。
加工知識(shí)的過程有兩個(gè)方面。小批生產(chǎn)低費(fèi)用。對(duì)于鑄造、鍛造和壓力加工,每一個(gè)要生產(chǎn)的具體工件形狀,即使是一個(gè)零件,幾乎都要花費(fèi)高額的加工費(fèi)用??亢附觼懋a(chǎn)生的結(jié)構(gòu)形狀,在很大程度上取決于有效的原材料的形式。一般來說,通過利用貴重設(shè)備而又無需特種加工條件下,幾乎可以以任何種類原材料開始,借助機(jī)械加工把原材料加工成任意所需要的結(jié)構(gòu)形狀,只要外部尺寸足夠大,那都是可能的。因此對(duì)于生產(chǎn)一個(gè)零件,甚至當(dāng)零件結(jié)構(gòu)及要生產(chǎn)的批量大小上按原來都適于用鑄造、鍛造或者壓力加工來生產(chǎn)的,但通常寧可選擇機(jī)械加工。
嚴(yán)密的精度和良好的表面光潔度,機(jī)械加工的第二方面用途是建立在高精度和可能的表面光潔度基礎(chǔ)上。許多零件,如果用別的其他方法來生產(chǎn)屬于大批量生產(chǎn)的話,那么在機(jī)械加工中則是屬于低公差且又能滿足要求的小批量生產(chǎn)了。另方面,許多零件靠較粗的生產(chǎn)加工工藝提高其一般表面形狀,而僅僅是在需要高精度的且選擇過的表面才進(jìn)行機(jī)械加工。例如內(nèi)螺紋,除了機(jī)械加工之外,幾乎沒有別的加工方法能進(jìn)行加工。又如已鍛工件上的小孔加工,也是被鍛后緊接著進(jìn)行機(jī)械加工才完成的。?
1?基本的機(jī)械加工參數(shù)
切削中工件與刀具的基本關(guān)系是以以下四個(gè)要素來充分描述的:刀具的幾何形狀,切削速度,進(jìn)給速度,和背吃刀量。?切削刀具必須用一種合適的材料來制造,它必須是強(qiáng)固、韌性好、堅(jiān)硬而且耐磨的。刀具的幾何形狀——以刀尖平面和刀具角為特征——對(duì)于每一種切削工藝都必須是正確的。?切削速度是切削刃通過工件表面的速率,它是以每分鐘英寸來表示。為了有效地加工,切削速度高低必須適應(yīng)特定的工件——刀具配合。一般來說,工件材料越硬,速度越低。?進(jìn)給速度是刀具切進(jìn)工件的速度。若工件或刀具作旋轉(zhuǎn)運(yùn)動(dòng),進(jìn)給量是以每轉(zhuǎn)轉(zhuǎn)過的英寸數(shù)目來度量的。當(dāng)?shù)毒呋蚬ぜ魍鶑?fù)運(yùn)動(dòng)時(shí),進(jìn)給量是以每一行程走過的英寸數(shù)度量的。一般來說,在其他條件相同時(shí),進(jìn)給量與切削速度成反比。?背吃刀量——以英寸計(jì)——是刀具進(jìn)入工件的距離。它等于旋削中的切屑寬度或者等于線性切削中的切屑的厚度。粗加工比起精加工來,吃刀深度較深。?
2?刀具磨損??
從已經(jīng)被處理過的無數(shù)脆裂和刃口裂紋的刀具中可知,刀具磨損基本上有三種形式:后刀面磨損,前刀面磨損和V型凹口磨損。后刀面磨損既發(fā)生在主刀刃上也發(fā)生副刀刃上。關(guān)于主刀刃,因其擔(dān)負(fù)切除大部金屬切屑任務(wù),這就導(dǎo)致增加切削力和提高切削溫度,如果聽任而不加以檢查處理,那可能導(dǎo)致刀具和工件發(fā)生振動(dòng)且使有效切削的條件可能不再存在。關(guān)于副刀刃,那是決定著工件的尺寸和表面光潔度的,后刀面磨損可能造成尺寸不合格的產(chǎn)品而且表面光潔度也差。在大多數(shù)實(shí)際切削條件下,由于主前刀面先于副前刀面磨損,磨損到達(dá)足夠大時(shí),刀具將實(shí)效,結(jié)果是制成不合格零件。?由于刀具表面上的應(yīng)力分布不均勻,切屑和前刀面之間滑動(dòng)接觸區(qū)應(yīng)力,在滑動(dòng)接觸區(qū)的起始處最大,而在接觸區(qū)的尾部為零,這樣磨蝕性磨損在這個(gè)區(qū)域發(fā)生了。這是因?yàn)樵谇邢骺ㄗ^(qū)附近比刀刃附近發(fā)生更嚴(yán)重的磨損,而刀刃附近因切屑與前刀面失去接觸而磨損較輕。這結(jié)果離切削刃一定距離處的前刀面上形成麻點(diǎn)凹坑,這些通常被認(rèn)為是前刀面的磨損。通常情況下,這磨損橫斷面是圓弧形的。在許多情況中和對(duì)于實(shí)際的切削狀況而言,前刀面磨損比起后刀面磨損要輕,因此后刀面磨損更普遍地作為刀具失效的尺度標(biāo)志。然而因許多作者已經(jīng)表示過的那樣在增加切削速度情況下,前刀面上的溫度比后刀面上的溫度升得更快,而且又因任何形式的磨損率實(shí)質(zhì)上是受到溫度變化的重大影響。因此前刀面的磨損通常在高速切削時(shí)發(fā)生的。?刀具的主后刀面磨損帶的尾部是跟未加工過的工件表面相接觸,因此后刀面磨損比沿著磨損帶末端處更為明顯,那是最普通的。這是因?yàn)榫植啃?yīng),這像未加工表面上的已硬化層,這效應(yīng)是由前面的切削引起的工件硬化造成的。不只是切削,還有像氧化皮,刀刃產(chǎn)生的局部高溫也都會(huì)引起這種效應(yīng)。這種局部磨損通常稱作為凹坑性磨損,而且偶爾是非常嚴(yán)重的。盡管凹坑的出現(xiàn)對(duì)刀具的切削性質(zhì)無實(shí)質(zhì)意義的影響,但凹坑常常逐漸變深,如果切削在繼續(xù)進(jìn)行的話,那么刀具就存在斷裂的危機(jī)。?如果任何進(jìn)行性形式?的磨損任由繼續(xù)發(fā)展,最終磨損速率明顯地增加而刀具將會(huì)有摧毀性失效破壞,即刀具將不能再用作切削,造成工件報(bào)廢,那算是好的,嚴(yán)重的可造成機(jī)床破壞。對(duì)于各種硬質(zhì)合金刀具和對(duì)于各種類型的磨損,在發(fā)生嚴(yán)重失效前,就認(rèn)為已達(dá)到刀具的使用壽命周期的終點(diǎn)。然而對(duì)于各種高速鋼刀具,其磨損是屬于非均勻性磨損,已經(jīng)發(fā)現(xiàn):當(dāng)其磨損允許連續(xù)甚至到嚴(yán)重失效開始,最有意義的是該刀具可以獲得重磨使用,當(dāng)然,在實(shí)際上,切削時(shí)間遠(yuǎn)比使用到失效的時(shí)間短。以下幾種現(xiàn)象之一均是刀具嚴(yán)重失效開始的特征:最普遍的是切削力突然增加,在工件上出現(xiàn)燒損環(huán)紋和噪音嚴(yán)重增加等。?
3?切削參數(shù)的改變對(duì)切削溫度的影響
金屬切削操作中,熱是在主變形區(qū)和副變形區(qū)發(fā)生的。這結(jié)果導(dǎo)致復(fù)雜的溫度分布遍及刀具、工件和切屑。圖中顯示了一組典型等溫曲線,從中可以看出:像所能預(yù)料的那樣,當(dāng)工件材料在主變形區(qū)被切削時(shí),沿著整個(gè)切屑的寬度上有著很大的溫度梯度,而當(dāng)在副變形區(qū),切屑被切落時(shí),切屑附近的前刀面上就有更高的溫度。這導(dǎo)致了前刀面和切屑離切削刃很近的地方切削溫度較高。
實(shí)質(zhì)上由于在金屬切削中所做的全部功能都被轉(zhuǎn)化為熱,那就可以預(yù)料:被切離金屬的單位體積功率消耗曾家的這些因素就將使切削溫度升高。這樣刀具前角的增加而所有其他參數(shù)不變時(shí),將使切離金屬的單位體積所耗功率減小,因而切削溫度也將降低。當(dāng)考慮到未變形切屑厚度增加和切削速度,這情形就更是復(fù)雜。未變形切屑厚度的增加趨勢(shì)必導(dǎo)致通過工件的熱的總數(shù)上產(chǎn)生比例效應(yīng),刀具和切屑仍保持著固定的比例,而切削溫度變化傾向于降低。然而切削速度的增加,傳導(dǎo)到工件上的熱的數(shù)量減少而這又增加主變形區(qū)中的切屑溫升。進(jìn)而副變形區(qū)勢(shì)必更小,這將在該區(qū)內(nèi)產(chǎn)生升溫效應(yīng)。其他切削參數(shù)的變化,實(shí)質(zhì)上對(duì)于被切離的單位體積消耗上并沒有什么影響,因此實(shí)際上對(duì)切削溫度沒有什么作用。因?yàn)槭聦?shí)已經(jīng)表明:切削溫度即使有小小的變化對(duì)刀具磨損率都將有實(shí)質(zhì)意義的影響作用。這表明如何人從切削參數(shù)來確定切削溫度那是很合適的。
測(cè)定高速鋼刀具溫度的最直接和最精確的方法是萊特&特倫特法,這方法也就是可提供高速鋼刀具溫度分布的詳細(xì)信息的方法。該項(xiàng)技術(shù)是建立在高速鋼刀具截面金相顯微測(cè)試基礎(chǔ)上,目的是要建立顯微結(jié)構(gòu)變化與熱變化規(guī)律圖線關(guān)系式。當(dāng)要加工廣泛的工件材料時(shí),萊特已經(jīng)論述過測(cè)定高速鋼刀具的切削溫度及溫度分布的方法。這項(xiàng)技術(shù)由于利用電子顯微掃描技術(shù)已經(jīng)進(jìn)一步發(fā)展,目的是要研究將已回過火和各種馬氏體結(jié)構(gòu)的高速鋼再回火引起的微觀顯微結(jié)構(gòu)變化情況。這項(xiàng)技術(shù)亦用于研究高速鋼單點(diǎn)車刀和麻花鉆的溫度分布。?
4?自動(dòng)夾具設(shè)計(jì)
用做裝配設(shè)備的傳統(tǒng)同步夾具把零件移動(dòng)到夾具中心上,以確保零件從傳送機(jī)上或從設(shè)備盤上取出后置于已定位置上。然而在某些應(yīng)用場(chǎng)合、強(qiáng)制零件移動(dòng)到中心線上時(shí),可能引起零件或設(shè)備破壞。當(dāng)零件易損而且小小振動(dòng)可能導(dǎo)致報(bào)廢時(shí),或當(dāng)其位置是由機(jī)床主軸或模具來具體時(shí),再或者當(dāng)公差要求很精密時(shí),那寧可讓夾具去適應(yīng)零件位置,而不是相反。為著這些工作任務(wù),美國俄亥俄州Elyria的Zaytran公司已經(jīng)開發(fā)了一般性功能數(shù)據(jù)的非同步西類柔順性夾具。因?yàn)閵A具作用力和同步化裝置是各自獨(dú)立的,該同步裝置可以用精密的滑移裝置來替換而不影響夾具作用力。夾具規(guī)格范圍是從0.2英寸行程,5英鎊夾緊力到6英寸行程、400英寸夾緊力。?
現(xiàn)代生產(chǎn)的特征是批量變得越來越小而產(chǎn)品的各種規(guī)格變化最大。因此,生產(chǎn)的最后階段,裝配因生產(chǎn)計(jì)劃、批量和產(chǎn)品設(shè)計(jì)的變更而顯得特別脆弱。這種情形正迫使許多公司更多地致力于廣泛的合理化改革和前面提到過情況那樣裝配自動(dòng)化。盡管柔性夾具的發(fā)展很快落后與柔性運(yùn)輸處理裝置的發(fā)展,如落后于工業(yè)機(jī)器人的發(fā)展,但仍然試圖指望增加夾具的柔順性。事實(shí)上夾具的重要的裝置——生產(chǎn)裝置的專向投資就加強(qiáng)了使夾具更加柔性化在經(jīng)濟(jì)上的支持。?根據(jù)它們?nèi)犴樞?,夾具可以分為:專用夾具、組合夾具、標(biāo)準(zhǔn)夾具、高柔性夾具。柔性夾具是以它們對(duì)不同工件的高適應(yīng)性和以少更換低費(fèi)用為特征的。
結(jié)構(gòu)形式可變換的柔性夾具裝有可變更結(jié)構(gòu)排列的零件(例如針形頰板,多片式零件和片狀頰板),標(biāo)準(zhǔn)工件的非專用夾持或夾緊元件(例如:?jiǎn)?dòng)標(biāo)準(zhǔn)夾持夾具和帶有可移動(dòng)元件的夾具配套件),或者裝有陶瓷或硬化了的中介物質(zhì)(如:流動(dòng)粒子床夾具和熱夾具緊夾具)。為了生產(chǎn),零件要在夾具中被緊固,需要產(chǎn)生夾緊作用,其有幾個(gè)與夾具柔順性無關(guān)的步驟:?根據(jù)被加工的即基礎(chǔ)的部分和工作特點(diǎn),確定工件在夾具中的所需的位置,接著必須選擇若干穩(wěn)定平面的組合,這些穩(wěn)定平面就構(gòu)成工件被固定在夾具中確定位置上的夾持狀輪廓結(jié)構(gòu),均衡所有各力和力矩,而且保證接近工件工作特點(diǎn)。最后,必須計(jì)算、調(diào)整、組裝可拆裝的或標(biāo)準(zhǔn)夾具元件的所需位置,以便使工件牢牢地被夾緊在夾具中。依據(jù)這樣的程序,夾具的輪廓結(jié)構(gòu)和裝合的規(guī)劃和記錄過程可以進(jìn)行自動(dòng)化控制。?結(jié)構(gòu)造型任務(wù)就是要產(chǎn)生若干穩(wěn)定平面的組合,這樣在這些平面上的各夾緊力將使工件和夾具穩(wěn)定。按慣例,這個(gè)任務(wù)可用人—機(jī)對(duì)話即幾乎完全自動(dòng)化的方式來完成。
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