831008工艺设计

常熟理工学院课程设计说明书

目 录

前

言·································································································································································2 1 零件的分析········································································································································2

1．1 零件的作用····································································································································2 1．2 零件的工艺分析····························································································································2

2 工艺规程的设计·······························································································································3

2．1 毛坯的制造形式····························································································································3 2．2 基准面的选择································································································································3 2．2．1 粗基准的选择··························································································································3 2．2．2 精基准的选择··························································································································3 2．3 制定工艺路线································································································································4 2．4毛坯尺寸的确定·····························································································································4 2．5 确定切削用量及基本工时············································································································5

3 绘制零件图和编制工艺卡············································································································6 4 夹具设计············································································································································7

4．1 问题的提出·································································································································7 4．2 夹具体设计·································································································································7 4．2．1 定位基准的选择·················································································································7 4．2．2 切削力及夹紧力的计算·····································································································8 4. 2. 3切削扭矩的计算和验证…………………………………………………………8 4．2．4定位误差分析·····················································································································8 4．2．5 夹具设计及操作的简要说明·····························································································8

5 结论·····················································································································································9 6 参考文献············································································································································10

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常熟理工学院课程设计说明书

前言

本课程设计设计的是CA6140车床上的拨叉831008，设计旨在提高CA6140车床拨叉的加工效率。拨叉的加工质量将直接影响机器的性能和使用寿命，由此我们首先对拨叉的结构特征和工艺进行了仔细的分析，然后确定了一套合理的加工方案，加工方案要求简单，操作方便，并能保证零件的加工质量。

此外，为了提高劳动生产率，降低劳动强度，保证加工质量，需设计专用夹具，以满足加工过程的需要。

1.零件工艺分析

1.1 零件的作用

题所给的是CA6140车床上的拨叉，它位于车床变速机构中，主要起换挡作用，使主轴回转运动按照工作者的要求工作，获得所需的速度和扭矩。零件上方的Φ20mm的孔与操作机构相连，下方的Ф50mm的半孔则是用于与所控制齿轮所在的轴接触，通过上方的力拨动下方的齿轮变速，两零件铸造为一体，加工时分开。 1.2 零件的工艺分析

CA6140车床共有两处加工表面，其间有一定位置要求。分述如下： 1. 以φ20为中心的加工表面

这一组加工表面包括：φ20 的孔，以及其上下端面，上端面与孔有位置要求，孔壁上有一个装配时钻铰的锥孔，一个M6的螺纹孔。

2. 以φ50为中心的加工表面

这一组加工表面包括：φ50 的孔，以及其上下两个端面。

这两组表面有一定的位置度要求,即φ50 的孔上下两个端面与φ20 的孔有垂直度要求。

由上面分析可知，加工时应先加工一组表面，再以这组加工后表面为基准加工另外一组。

2. 工艺规程设计

2.1 毛坯制造形式

零件材料为HT200，考虑零件在机床运行过程中所受冲击不大，零件结构又比较简单，故选择铸件毛坯。

2.2 基准的选择

2.2.1 粗基准的选择 对零件而言，尽可能选择不加工表面为粗基准，而对若干个

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常熟理工学院课程设计说明书

不加工表面的工件，则应以与加工表面要求相对位置精度较高的不加工表面作粗基准，根据这个基准原则，现取Ф20mm的孔的不加工外轮廓表面作为粗基准，利用一组共两个短V形块支承两个Ф20mm孔的外轮廓作主要定位面，以消除3个自由度，再用一个支承板支撑在Ф72mm的上表面，以消除3个自由度。

2.2.2 精基准的选择 主要应考虑基准重合问题。当设计基准不重合时，应该进行尺寸换算，这在以后还要专门计算，此处不再重复。

2.3 工艺路线的制定

制定工艺路线的出发点，应当是使零件的几何形状、尺寸精度及位置精度等技术要求能得到合理的保证。在生产纲领已确定为中批生产的条件下，可以考虑采用万能性机床配以专用夹具，并尽量使工序集中来提高生产率。除此以外，还应当考虑经济效果，以便使生产成本尽量下降。 1、 工艺路线方案一： 工序1 铸造毛坯

工序2 时效处理，（消除铸件造应力，便于机加工） 工序3 粗精铣底平面，粗铣φ32的上端面 工序4 钻、扩、铰φ20孔

工序5 精铣φ32的上端面，粗铣φ50上端面 工序6 精车φ50端面 工序7 粗、精镗φ50孔 工序8 钻锥孔φ8及M6底孔 工序9 攻螺纹M6

工序10 粗铣φ32 圆柱的侧面 工序10 切断

工序11 去毛刺 清洗 工序12 终检

2、工艺路线方案二: 工序1 铸造毛坯 工序2 半精铣底面 工序3 钻扩两孔φ20

工序4 粗镗 半精镗孔φ50 工序5 粗铣 半精铣φ50端面 工序6 粗铣 半精铣φ32端面 工序8 钻锥孔φ8及M6底孔 工序9 攻螺纹M6

工序10 半精绞 精绞两孔φ20 工序11 切断

工序12 去毛刺 清洗 工序13 终检

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常熟理工学院课程设计说明书

3、工艺方案的确定:

上述两方案:方案一 是先加工平面和内孔φ20, 再以φ20孔为精基准加工φ50端面及φ50内孔,而方案二是先加工底面,以底面为基准加工φ20内孔和φ50孔.由方案一可见φ20孔为精基准加工各平面，易于保证各面与φ20孔的垂直度要求,同时以φ20为精基准加工φ50孔端面及内孔，既可保证其端面的垂直度要求 ,又使的设计基准与定位基准重合，可便于定位加工，且使定位误差大大减小，符合中批生产要求,方案 一较为合理。

因此，最后的加工路线确定如下： 工序1 铸造毛坯 工序2 时效处理

工序3 粗精铣底面/以φ32端面为基准，粗铣φ32的上端面/以底面为 基准

选用X52K立式和专用夹具

工序4 钻、扩、铰两孔φ20/以φ50内孔为基准，φ32外圆定位

选用Z3025摇臂钻床和专用夹具

工序5 精铣φ32上端面，粗铣φ50孔端面/以底面及φ32外围为基准

选用X62卧式铣床和专用夹具

工序6 精车φ50端面，粗精镗φ50孔/以底面和φ20内孔为基准

选用CA6140车床和专用夹具

工序7 钻锥孔φ8及M6底孔攻螺纹M6/以φ20内孔和φ20端面为基准

选用Z3025摇臂钻床及专用夹具

工序8 粗铣φ32圆柱侧面

选用X52K立式和专用夹具

工序9 切断/以φ20内孔及底面为基准

选用x62卧式铣床床和专用夹具

工序10 去毛刺清洗 工序11 终检

2.4 确定毛坯尺寸

拨叉零件材料为HT200 HB170—240，毛坯重量约1.0Kg生产中批采用机械砂型铸造毛坯。又由<<机械制造工艺设计简明手册>>表2.2-4查得加工余量等级为G级，选取尺寸公差等级为CT10。

根据以上资料及路线，分别确定各加工表面的机械加工余量、工序尺寸及毛坯如下：(1)、由于工件较小，为方便加工节省材料将两件铸在一起，同时加工。 (2)、铸件的圆角半径 按<<机械制造工艺简明设计手册>>表2.2.1 选则机械砂型R=3-5mm，拔模斜度外表面α圆柱铸成实心的。

4

=030

O

’

。毛坯热处理方式为自然失效处理以消除铸造应力。

(3)、两内孔φ20,考虑其孔径较小铸造困难，为简化铸造毛坯外型，现直接将φ32

常熟理工学院课程设计说明书

（4）在垂直方向上，查<<机械制造工艺设计简明手册>>表2.2~4得：取Ф20mm、Ф50mm两端面长度余量为2.5mm。

铣削加工余量为：1)粗铣：1.5mm 2)精铣：1mm 毛坯尺寸及公差为：（35土0.3）mm （ 17土0.25）mm

（5）内孔（Ф50mm已铸成孔）查《机械制造工艺设计简明手册》表2.2~2.5，取Ф50mm已铸成长度余量为3mm，即已铸成孔Ф44mm。 镗削加工余量为：1)粗镗：2mm 2)半精镗：1mm

0.50毛坯尺寸及公差为：（48土0.3）mm （50??0.25）mm

（6）其他尺寸直接铸造得到。 2.5 确定切削用量及基本工时 工序七： 钻Ф8的底孔，攻螺纹M6 （1）工艺装备

工艺要求；孔径do=7.8mm ,孔深6mm，钻孔径5.2mm，孔深6，攻螺纹M6 刀具： 高速钢麻花钻Ф7.8，Ф5.2；螺纹刀Ф6 机床：Z525立式钻床 夹具：专用夹具

量具：游标卡尺 （2）计算切削用量f 1) 决定进给量f 按加工要求决定进给量

根据《机械制造工艺简明手册》表2.7，当铸铁的强度 бb?200HBS do=7.8mm时，

f=（0.1~0.2）do=0.078~0.156mm/r 当铸铁的强度

бb??200HBS do=5.2mm时，f=0.053~0.104mm/r

按钻头强度决定进给量 根据表2.8，当бb=190MPa,do<=4.3mm,钻头强度允许的进给量f=0.5mm/r c)按机床进给机构强度决定进给量 根据表2.9，当бb??210MPa,do??10.2mm,机床进给机构允许的轴向力为8330N（Z525钻床允许的轴向力为8830N（见《机械制造工艺设计手册》表4.2-14）时，进给量为1.63mm/r。 从以上三个进给量比较可以看出，受限制的进给量是工艺要求，其值为f=(0.078~.156) mm/r，根据Z525钻床说明书，选f=0.1mm/r（见《机械》表5-113），又由《机械》表2.19可以查出钻孔时的轴向力，当f<=0.17mm/r do<=12mm时，轴向力Ff=1230N

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