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黑龍江工程學(xué)院本科生畢業(yè)設(shè)計
附 錄A
液壓鏜床夾具的工作原理
鏜床夾具是為了粗鏜側(cè)面的上下孔,因為尺寸要求和位置要求比較多所以需要限制除的5個 自由度。由于箱體零件典型的一面兩銷定位方式可以同時滿足以上兩種定位要求,所以對于鏜床夾具都選擇一面兩銷完全定位的方式。
定位元件的設(shè)計包括定位元件的結(jié)構(gòu),形狀,尺寸及布置方式等。工件的定位設(shè)計主要決定與工件的加工要求和工件定位基準(zhǔn)的形狀尺寸精度等因素,所以在設(shè)計時應(yīng)分析定位基準(zhǔn)的形態(tài)。
支承板帶斜槽的支承板,用于水平方向布置的定位中,其凹槽可防止細(xì)小切屑停留在定位面上。支承板的主要規(guī)格厚度H取10mm。支承板用碳素工具鋼T8,經(jīng)熱處理到55-60HRC。6塊支承板同時使用,需要設(shè)法使厚度H相等。支承板用螺釘緊固在夾具體上??上拗?個自由度[5]。
兩銷定位即工件以圓柱孔定位。工件以精基準(zhǔn)孔定位,定位銷選擇固定式定位銷,它是組合定位中常用的定位元件之一。圖2.1所示為A型定位銷,可限制工件的兩個自由度。
固定式定位銷(GB/T2203-91)主要規(guī)格D取12mm。定位銷材料用碳素工具鋼T8,經(jīng)熱處理至55-60HRC
工作原理: 夾具采用的定位方式是一面兩銷,面即是加工零件以精基準(zhǔn)平面定位。工件的基準(zhǔn)平面經(jīng)切削加工后,可以直接放在平面上定位。經(jīng)過刮削,磨削的平面具有較小的表面粗糙度和平面度誤差,故可獲得較精確的定位。常用的定位元件有支承板和平面支承釘?shù)?。這類是呈面接觸的定位元件。本設(shè)計中夾具選擇支承板作為定位元件。
本夾具采用單件同向聯(lián)動夾緊機(jī)構(gòu),通過壓桿連接銷軸聯(lián)動拉桿壓爪實現(xiàn)夾緊和放松,壓桿外接活塞結(jié)構(gòu)實現(xiàn)夾具的運動。
工件以多個定位基準(zhǔn)組合定位是很常見的。它們可以是平面,外圓柱面,內(nèi)圓柱面,圓錐面等各種組合。工件組合定位時應(yīng)該合理的選擇定位元件;按基準(zhǔn)重合原則選擇定位基準(zhǔn);組合定位中,一些定位元件單獨使用時限制沿坐標(biāo)軸方向的自由度,而組合定位時則轉(zhuǎn)化為限制繞坐標(biāo)軸方向的自由度。
計中加工減速器箱體零件,采用兩孔一面定位,以使基準(zhǔn)統(tǒng)一。這種定位方式所采用的定位元件為支承板,定位銷和菱形銷。下面將重點介紹菱形銷的設(shè)計和布置,以防止過定位。
菱形銷作為防轉(zhuǎn)支承,其布置應(yīng)使長軸方向與兩銷的中心連線垂直,并應(yīng)正確選擇菱形銷直徑的基本尺寸和經(jīng)削邊后圓柱部分的寬度。
工件在夾具中加工時加工誤差由以下四方面組成:
⑴ ——夾具位置誤差,即定位元件相對機(jī)床的切削成形運動的位置誤差。
⑵ ——定位誤差,即由定位引起的工序基準(zhǔn)的位置誤差。
⑶ ——刀具相對夾具的位置誤差,即對刀導(dǎo)向誤差。
⑷ ——與加工過程中一些因素有關(guān)的加工誤差。
——圓柱定位銷的直徑公差(mm);
——菱形定位銷的直徑公差(mm);
——圓柱定位銷與孔間的最小間隙(mm);
L——中心距(mm)。
在機(jī)械加工過程中,為保持工件定位時所確定的正確的加工位置,為防止工件在切削力,慣性力,離心力及重力等作用下發(fā)生位移和震動,一般機(jī)床夾具都應(yīng)有個夾緊裝置,以將工件夾緊。
夾緊裝置分為手動夾緊和機(jī)動夾緊。根據(jù)結(jié)構(gòu)和功用,典型夾緊裝置由力源裝置;中間傳力機(jī)構(gòu);夾緊元件。
本設(shè)計的兩套夾緊裝置采用機(jī)動夾緊。其中銑床夾具采用液壓夾緊機(jī)構(gòu),鏜床夾具采用聯(lián)動夾緊機(jī)構(gòu)。
確定夾緊力的方向,作用點和大小時,應(yīng)該根據(jù)工件的結(jié)構(gòu)特點,加工表面要求并結(jié)合工件加工中的受力狀況及定位元件的結(jié)構(gòu)和布置方式等綜合考慮。
本設(shè)計的夾緊力基本上符合下面的要求。夾緊力的方向應(yīng)有助于定位穩(wěn)定,且主夾緊力應(yīng)朝向主要定位基面;夾緊力的方向應(yīng)該有利于減小夾緊力;夾緊力的方向應(yīng)是工件鋼度較高的方向。夾緊力的作用點應(yīng)落在定位元件的支承范圍內(nèi);夾緊力的作用點應(yīng)選在工件鋼度較高的部位;夾緊力的作用點應(yīng)盡量靠近加工表面。
因為工件是大量生產(chǎn),夾緊力又比較大,所以采用液壓夾緊,液壓缸選用通用系列查文獻(xiàn)表得本次設(shè)計選用5016和5019型兩種液壓缸。
鏜床夾具都選擇一面兩銷完全定位的方式。這樣夾具裝卸比較容易有利于提高加工速度和生產(chǎn)效率,液壓系統(tǒng)傳動力大工作平穩(wěn)可靠,噪音小,勞動條件和經(jīng)濟(jì)性都比較實惠。
譯文
Boring fixture is to rough up the side facing hole, because dimensional requirements and location requires more so need to limit the five degrees of freedom in. Because of the typical case accessories side two pins localization way can also meet the above two kinds of positioning requirement, so for the boring fixture choose a two way of positioning pin completely.
Positioning of components of the design of components, including positioning structure, its size and layout mode, etc. Also the positioning of the main decision and the design requirements of the processing and the part of the shape of the locating datum size precision, so factors such as in the design should be analyzed the locating datum form.
Plate figure shows is the type B slides with the plate for horizontal direction, decorate in the groove of the positioning, can prevent tiny chip stay in positioning surface. The main specifications plate thickness H take 10 mm. Plate with carbon tool, the heat treatment to 55 T8 HRC-60. 6 piece of plate used at the same time, need to try to make thickness H equal. Plate with bolt in the clip in the concrete tighten. It can limit 3 dof .
Two pin location that is with cylindrical holes position. The In essence the benchmark hole positioning, pins choose fixed location pins, it is the combination of the components used in positioning positioning of one. Figure 2.1 shows is the type A location pins, can limit the two degrees of freedom.
Fixed location pins (GB/T2203-91) main specifications D take 12 mm. Positioning pin material to use carbon tool, the heat treatment to 55 T8 HRC-6
Working principle: by way of positioning fixture is a two pins, surface, as is processing components to fine benchmark plane positioning. The benchmark by cutting plane, can be directly on the plane positioning. After scraping, grinding plane with smaller surface roughness and plane degree error, we can get a precise positioning of. Some of the commonly used location components have plate surface nail etc. Supporting peace This class is a surface with the positioning of the components. This design jigs choose plate as positioning components.
This fixture using single homonymous linkage clamping institutions, through the compressive bar linkage connected pin shaft lever pressure clamping claw realize and relax, press the piston rod external fixture structure realize sports.
The DuoGe positioning in the benchmark portfolio fixed position is very common. They can is flat, and YuanZhuMian outside, inside the YuanZhuMian, cone face all kinds of combination. The combination should be the choice of reasonable positioning positioning component; According to the principle of superposition benchmark selecting position datum; Combination of some positioning components, orientation, when used alone, limit freedom, direction along the coordinate transformation and combination is converted to limit when positioning coordinate direction around the degrees of freedom.
This design processing speed reducer, the case accessories two holes, in order to make the benchmark side position is unified. The localization way the positioning components as the plate, pins and diamond pin. Below will focus on the introduction of the diamond pin design and decorate, to prevent a location.
The diamond pin as waterproof supporting turn, the arrangement should make long axis and the center of the two pins, and should be vertical attachment to choose the right diamond pin the diameter of the basic size and the cutting edge after the width of the cylindrical part as shown in figure 2.4.
The diamond pin design procedure is as follows:
1. Sure two pins the center distance of two pins center distance should be equal to the size of the basic orientation of two pitch, the size of the average tolerance is commonly
2. Select pins on table take pins of standard code for A 12 h7x14GB/T2203
3. Choose diamond pin width b according to table take b = 4 mm
4. Sure the diamond pin diameter
(1) for compensation amount. A
(2) the positioning of the smallest diamond. Calculation clearance
(3) the diameter of the diamond pin. Calculation
Take tolerance zone, namely the diamond pin for h6 the standard code for B12h6x14 .
Add the fixture workpiece machining errors by the working hours of four aspects:
(1) the fixture position errors, namely, the cutting machine element positioning relative position error of the movement of the forming.
(2)-positioning error caused by positioning, namely the working procedure of the position of the benchmark error.
(3) the position of the tool relative fixture that knife orientation error error.
(4)and process of some factors processing error.
Because the two sets of fixture use the locating datum and scheme, in which do exactly the same position error analysis are as follows:
(1) the perpendicular tolerance 0.08
(2) the known:Figure 2.5 diamond pin perpendicularity errors were
(3) the parallel degree of tolerance 0.04 mm. As shown in figure 2.4 shows, when the workpiece will influence the parallel degree tolerance skewed by the figure 2.5 can get the corner error formula.
Type of work pieces positioning the diameter of holes-tolerance (mm);
-the diameter of the cylinder pins tolerance (mm);
-the diameter of the diamond pins tolerance (mm);
-cylindrical pins and the minimum clearance between hole (mm);
L-centre distance (mm).
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