本科毕业设计（论文）
（外文翻译）
题 目 75拖拉机变速箱壳体机械加工工艺规程设计 学生姓名 XXXXXX 专业班级 机械设计制造及其自动化（本科二班） 学 号 200933080 院 （系） 机械工程学院 指导教师(职称) XXXXXX
二○一三年五月十八日
Gearbox shell machining process design
《Manufacturing Engineering and Technology—Machining 》
Mechanical Industry Press In March 2004, version 1 p560—564
（Serope kalpakjian） （Steven R.Schmid）
Abstract
Gearbox shell is a more complex structure of spare parts box, its high precision, complex process, and the processing quality will affect the overall performance engine, so it has become the engine manufacturer's focus parts one.Machining process planning must guarantee the machining quality of parts, to meet the technical requirements stipulated in drawings, at the same time should also have high productivity and efficiency. Therefore, machining process planning design is an important work, requires designers must have a rich experience in production practice and wide range of mechanical manufacturing technology basic theory knowledge. In the specified procedure, should according to the production of parts and the existing equipment conditions, taking the processing quality into account, productivity and economy requirements, after repeated analysis and comparison, to determine the optimal or the best solution.
1.Technical Characteristics of the gearbox shell
The gearbox shell process features are: the structure of complex shape; processing plane, more than holes; uneven wall thickness and stiffness is low; processing of high precision typical of box-type processing part. The main processing of the surface of cylinder block top surface, the main bearing side, cylinder bore, the main and
camshaft bearing bore holes and so on, they will directly affect the machining accuracy of the engine assembly precision and performance, mainly rely on precision equipment, industrial fixtures reliability and processing technology to ensure the reasonableness.
2.The gearbox shell process design principles and the basis Design Technology program should be to ensure product quality at the same time, give full consideration to the production cycle, cost and environmental protection; based on the enterprises ability to actively adopt advanced process technology and equipment, and constantly enhance their level of technology. Gearbox shell machining process design should follow the following basic principles:
2.1 The selection of processing equipment
The principle of selection adopted the principle of selection adopted the principle of combining rigid-flexible, processing each horizontal machining center is located mainly small operations with vertical machining center, the key process a crank hole, cylinder hole, balancer shaft hole High-speed processing of high-precision horizontal machining center, an upper and lower non-critical processes before and after the four-dimensional high-efficiency rough milling and have a certain adjustment range of special machine processing;
2.2 Concentration process principle
Focus on a key process in principle process the body cylinder bore, crankshaft hole, Balance Shaft hole surface finishing and the combination of precision milling cylinder head, using a process focused on a setup program to complete all processing elements in order to ensure product accuracy The key quality processes to meet the cylinder capacity and the relevant technical requirements;
3.The gearbox shell machining process design the main content
Gearbox shell complex structure, high precision, arge size, is thin-walled parts, there are a number of high precision plane and holes. Engine block machining process
characteristics; mainly flat and the hole processing, processing of flat generally use planing, milling methods such as processing, processing of hole used mainly boring, processing and multi-purpose drilling holes. As the cylinder complex structure. so how to ensure that the mutual position of the surface processing precision is an important issue.
3.1 The selection of blank
Gearbox shell on the materials used are generally gray cast iron HT150,HT200,HT250,there is also cast aluminum or steel plate, this engine block using high-strength alloy cast iron. Cylinder in the processing prior to aging treatment in order to eliminate stress and improve the rough casting mechanical properties.
Improve the rough accuracy, reduction of machining allowance, is to improve the automated production line system productivity and processing quality of the important measures. As the foreign box-type parts of rough quality and high precision, and its production-line system has been implemented directly on the blank line, not only eliminating the need for blank check device also saves the rough quality problems due to waste of machining time, increase overall efficiency. Therefore, the refinement of rough is to improve the productivity of the most promising way out. For the engine block production line, can be rough in parts on-line pre-milling six face, removing most of the margin, to facilitate direct on-line parts.
3.2 Machining process selection and processing of the benchmark
Choose the right processing technology base is directly related to the processing quality can ensure the parts. Generally speaking, process benchmarking can be divided into coarse and fine reference base.
3.2.1 Coarse reference base
The baseline for the on-line thick rough ,which is particularly important the choice of benchmark crude, if crude benchmark choice unreasonable, will the uneven distribution of machining allowance, processing and surface offsets, resulting in waste.
In the cylinder production line, we have adopted for the coarse side of the base;
3.2.2 Fine reference base
Refined the base of this box for the engine block parts, the general use of "side two sales "for a full range of uniform benchmarks, For the longer automated production positioning. In the gearbox shell of the process, we have adopted to the side, bottom and the spindle hole positioning, in the processing center on the process.
3.3 Machining Processing Stages and processes of the arrangements
Often a part of many apparent need for processing, of course, the surface machining accuracy are different. Processing of high precision surface, often after repeated processing; As for the processing of the surface of low precision, only need to go through one or two on the list. Thus, when the development process in order to seize the "processing high precision surface, "this conflict, the reasonable arrangement processes and rational division stage of processing. Arrange the order of the principle of process is: after the first coarse refined, the first surface after the hole, the first benchmark other. In the engine block machining, the same should follow this principle.
3.3.1 roughing stage engine block machining process
The arrangements for roughing process, to fully carry out rough rough, trim most of the margin in order to ensure production efficiency;
3.3.2 semi-finishing phase of the engine block machining
In order to ensure the accuracy of the middle of some important surface processing, and arrange some semi-finishing operations, will be required accuracy and surface roughness of the surface of the middle of some processing to complete, while demanding the surface of semi-finished, to prepare for future finishing;
3.3.3 The finishing stage
The finishing stage of requiring high accuracy and surface roughness of the surface processing;
3.3.4 secondary processing
Secondary processing such as small surface screw holes, you can finish of the major surface after the one hand, when the workpiece deformation process little impact at the same time also reduced the rejection rate;In addition,if the main surface of a waste,these small the surface will not have to be processed,thus avoiding a waste of man-hours.However,if the processing is very easy for a small surface bumps the main surface,it should be placed on a small surface finish prior to the main surface finishing;
3.3.5 make proper arrangements for secondary processes
Make proper arrangements for secondary processes such as product inspection process,in part roughing stage,the key process before and after processing,spare parts all the processing has been completed,should be appropriate arrangements.
Stage of processing division,has the following advantages:First,it can take measures to eliminate the rough workpiece after the stress,to ensure accuracy; second,finishing on the back,and will not damage during transport the surface of the workpiece has been processed;again,first roughing the surface defects can be detected early and promptly deal with rough,do not waste working hours.But most small parts,do not sub very thin.
3.4 The gearbox shell surface of the main processing and secondary processes
3.4.1 Plane processing
Plane processing at present, the milling of engine blocks is the primary means of planar processing,domestic milling feed rate is generally 300-400mm/min,and foreign 2000-4000mm/min milling feed rate compared to far cry,to be on increasing,therefore,improve the milling feed rate,reduce overhead time is to improve the productivity of the major means of finishing a number of plane engine block when the milling feed rate to reach 2399mm/min,greatly improved efficiency;
Top surface of the cylinder milling is a key process in the process,the flatness
requirements for 0.02/145mm,the surface roughness of Ra1.6um.Processing in the cylinder,the use of side and spindle bearing bore positioning,top,bottom and middle vagay only aperture while processing used in the processing line outside of the knife device can better meet the engine block machining accuracy;
3.4.2 General holes Machining
General holes Machining holes in general are still using the traditional processing of drilling,expansion,boring,reaming,tapping and other craft approach. Issues in the design process of specific programs,use of coated cutting tools,cutting tools and other advanced tools within the cooling,and using a large flow of cooling systems,greatly improving the cutting speed,improved productivity;
3.4.3 Deep hole processing
Deep hole processing of the traditional processing method is used to grade twist drill feed,low efficiency of their production,processing and quality is poor.The deep hole in the engine block processing,the use of gun drilling process;
3.4.4 Cleaning
Cleaning is divided into wet cleaning and dry cleaning.Machining cylinder automatic production line using a large flow of wet cleaning;
3.4.5 Detection
Detect points outside the line detection and line detection of two kinds. Quality inspection in the engine block,according to the actual situation with lines outside the detection,the main use of coordinate measuring machine integrated measurements of the cylinder,each 200 samples 1-5 pieces,each class random one.
变速箱壳体机械加工工艺设计
摘自： 《机械工程与技术（机加工）》（英文版）
机械工业出版社 2004年3月第1版 p560—564
美 s. 卡卡尔帕基安 s.r 施密德
摘要
变速箱壳体是变速器机零件中结构较为复杂的箱体零件，其精度要求高，加工工艺复杂，并且加工加工质量的好坏直接影响发动机整个机构的性能，因此，它成为各个发动机生产厂家所关注的重点零件之一。机械加工工艺规程必须保证零件的加工质量，达到设计图纸规定的各项技术要求，同时还应该具有较高的生产率和经济性。因此，机械加工工艺规程设计是一项重要的工作，要求设计者必须具有丰富的生产实践经验和广博的机械制造工艺基础理论知识。
1. 变速箱壳体的工艺特点
变速箱壳体的工艺特点是：结构、形状复杂；加工的平面和孔比较多；壁厚不均，刚度低；加工精度要求高，属于典型的箱体类加工零件。变速箱的主要加工表面有顶面、孔系、主轴承孔及螺纹孔等，它们的加工精度将直接影响发动机的装配精度和工作性能，主要依靠设备进度、工夹具的可靠性和加工工艺的合理性来保证。
2. 变速箱壳体工艺方案设计原则和依据
设计工艺方案应在保证产品质量的同时，充分考虑生产周期、成本和环境保护；根据本企业能力，积极采用国内外先进的工艺技术和装备，不断提高企业工艺水平。变速箱壳体机械加工工艺设计应遵循以下基本原则：
2.1加工设备选型原则
加工设备选型采用刚柔结合的原则，加工设备以卧式加工中心为主，少量采用立式加工中心，关键工序—曲轴孔、缸孔、平衡轴孔加工采用高精度高速卧式加工中心，非关键工序—上下前后四个平面的粗铣采用高效并有一定调整范围的专用机床加工；
2.2 集中工序原则
关键工序—曲轴孔、缸孔、平衡轴孔的精加工缸盖结合面的精铣，采用在集中在一道工序一次装夹完成全部加工内容方案，以确保产品精度满足缸体关键品质的工艺性能和有关技术要求。
3. 发动机缸体机械加工工艺设计的主要内容
发动机缸体结构复杂，精度要求高，尺寸较大，是薄壁零件，有若干精度要求较高的平面和孔。发动机缸体机械加工的工艺特点是：主要是平面和孔的加工，加工平面一般采用刨、铣削等方法加工，加工孔主要采用镗削，加工小孔多用钻削。由于缸体结构复杂，因此如何保证各表面的相互位置精度是加工中的一个重要问题。
3.1 毛坯的选择
变速箱壳体采用的材料一般是灰铸铁HT150、HT200、HT250，也有采用铸铝或者钢板的，此发动机缸体采用高强度合金铸铁。缸体在加工前进行时效处理，以消除铸件内应力和改善毛坯的力学性能。
提高毛坯精度，减少加工余量，是提高自动生产线系统生产率及加工质量的重要措施。由于国外箱体类零件毛坯质量和精度较高，其生产线系统已实现了毛坯直接上线，既省去了毛坯检查装置，也节省了由于毛坯质量问题而浪费的加工工时，提高了综合效益。因此，精化毛坯是提高生产率最有潜力的出路。对于发动机缸体生产线，可在零件上线前粗铣六个面，去除大部分余量，便于零件直接上线。
3.2机械加工工艺基准的选择和加工
选择合理的加工工艺基准，直接关系到能否保证零件的加工质量。一般来说，工艺基准可分为粗基准和精基准。
3.2.1 粗基准
粗基准对于上线的毛坯，其粗基准的选择尤为重要，如果粗基准选择不合理，会使加工余量分布不均匀，加工面偏移，造成废品。在缸体生产线中，我们采用侧面作为粗基准；
3.2.2 精基准
粗基准对于发动机缸体这种箱体零件来说，一般采用“一面两销”为全线的统一基准。对于较长的自动自动生产线系统，由于定位销孔在使用过程中的磨损造成定位不准确。在变数箱体的加工中，我们采用了以侧面、底面和主轴孔定位，在加工中心上加工。
3.3 机械加工加工阶段的划分和工序的安排
一个零件往往有许多表面需要加工，当然表面的加工精度是不同的。加工精度较高的表面，往往要经过多次加工；而对于加工精度低的表面，只要经过一两次就行了。因此，拟定工艺顺序时，要抓住“加工精度高的表面”这个矛盾，合理安排工序和合理划分加工阶段。安排工艺顺序的原则是：先粗后精，先面后孔，先基准后其他。在发动机缸体的机械加工中同样应遵循这一原则。
3.3.1 粗加工阶段
在发动机缸体的机械加工过程中，安排粗加工工序，对毛坯全面进行粗加工，切去大部分余量，以保证生产效率；
3.3.2 半精加工阶段
在发动机缸体的机械加工过程中，为了保证一些重要表面的加工精度，安排一些半精加工工序，将精度和表面粗造度要求中等的一些表面加工完成，而对要求高的表面进行半精加工，为以后的精加工做准备；
3.3.3 精加工阶段
对精度和表面粗造度要求高的表面进行加工；
3.3.4 次要小表面的加工
如螺纹孔，可以在精加工主要表面后进行，一方面加工时对工件变形影响不大，同时废品率也降低；另外，如果主要表面出废品后，这些小表面就不必再加
工了，从而避免浪费工时。但是，如果小表面的加工很容易碰伤主要表面时，就应该把小表面加工放在主要表面的精加工之前；
3.3.5 辅助工序也要妥善安排
如检验工序，在零件粗加工阶段之后，关键工序加工前后，零件全部加工完毕后，都要适当安排。
对加工阶段进行划分，具有以下好处：首先，可以在粗加工后采取措施消除工作内应力，保证精度；其次，精加工放在最后面，不至于在运输过程中损坏工件已加工表面；再次，先粗加工各面，可以及早发现毛坯缺陷并及时处理，不会浪费工时。不过对于一般小工件就不要分的很细。
3.4 箱体的主要加工表面和辅助工序
3.4.1 平面加工
目前，铣削是发动机缸体平面加工的主要手段，国内铣削进给量一般为300-400mm/min，与国外铣削进给量2000-4000 mm/min相比，相差甚远，有待于提高，因此，提高铣削进给量，缩短辅助时间，是提高生产效率的主要途径，发动机缸体精加工一些平面时的铣削进给量达到2399mm/min，大大提高了效率；
顶面的铣削是缸体加工中的一个关键工序，其平面度要求为0.02/145mm，表面粗造度为Ra1.6um 。在缸体的加工中，采用侧面和主轴轴承孔定位，顶面、底面和中间瓦盖面同时加工，在加工中采用线外对刀装置，能较好地满足发动机缸体加工精度要求；
3.4.2 一般孔系的加工
一般孔系的加工仍采用传统的钻、扩、镗、铰、攻丝等工艺方法。课题在设计具体的工艺方案时，采用涂层刀具、内冷却刀具等先进刀具，采用大流量冷却系统，大大提高了切削速度，提高了生产率；
3.4.3 深油孔加工
传统的加工方法是采用麻花钻进行分级进给，其生产效率低，加工质量差。在发动机缸体深油孔的加工中，采用枪钻工艺；
3.4.4 清洗
清洗分为湿式清洗和干式清洗。缸体机械加工自动生产线采用大流量湿式清洗；
3.4.5 检测
检测分为在线检测和线外检测两种。在发动机缸体的质量检测中，根据实际情况采用线外检测，主要采用三坐标测量机对缸体进行综合测量，每200件抽查1-5件，每班抽查一件。
本科毕业设计（论文）
（外文翻译）
题 目 75拖拉机变速箱壳体机械加工工艺规程设计 学生姓名 XXXXXX 专业班级 机械设计制造及其自动化（本科二班） 学 号 200933080 院 （系） 机械工程学院 指导教师(职称) XXXXXX
二○一三年五月十八日
Gearbox shell machining process design
《Manufacturing Engineering and Technology—Machining 》
Mechanical Industry Press In March 2004, version 1 p560—564
（Serope kalpakjian） （Steven R.Schmid）
Abstract
Gearbox shell is a more complex structure of spare parts box, its high precision, complex process, and the processing quality will affect the overall performance engine, so it has become the engine manufacturer's focus parts one.Machining process planning must guarantee the machining quality of parts, to meet the technical requirements stipulated in drawings, at the same time should also have high productivity and efficiency. Therefore, machining process planning design is an important work, requires designers must have a rich experience in production practice and wide range of mechanical manufacturing technology basic theory knowledge. In the specified procedure, should according to the production of parts and the existing equipment conditions, taking the processing quality into account, productivity and economy requirements, after repeated analysis and comparison, to determine the optimal or the best solution.
1.Technical Characteristics of the gearbox shell
The gearbox shell process features are: the structure of complex shape; processing plane, more than holes; uneven wall thickness and stiffness is low; processing of high precision typical of box-type processing part. The main processing of the surface of cylinder block top surface, the main bearing side, cylinder bore, the main and
camshaft bearing bore holes and so on, they will directly affect the machining accuracy of the engine assembly precision and performance, mainly rely on precision equipment, industrial fixtures reliability and processing technology to ensure the reasonableness.
2.The gearbox shell process design principles and the basis Design Technology program should be to ensure product quality at the same time, give full consideration to the production cycle, cost and environmental protection; based on the enterprises ability to actively adopt advanced process technology and equipment, and constantly enhance their level of technology. Gearbox shell machining process design should follow the following basic principles:
2.1 The selection of processing equipment
The principle of selection adopted the principle of selection adopted the principle of combining rigid-flexible, processing each horizontal machining center is located mainly small operations with vertical machining center, the key process a crank hole, cylinder hole, balancer shaft hole High-speed processing of high-precision horizontal machining center, an upper and lower non-critical processes before and after the four-dimensional high-efficiency rough milling and have a certain adjustment range of special machine processing;
2.2 Concentration process principle
Focus on a key process in principle process the body cylinder bore, crankshaft hole, Balance Shaft hole surface finishing and the combination of precision milling cylinder head, using a process focused on a setup program to complete all processing elements in order to ensure product accuracy The key quality processes to meet the cylinder capacity and the relevant technical requirements;
3.The gearbox shell machining process design the main content
Gearbox shell complex structure, high precision, arge size, is thin-walled parts, there are a number of high precision plane and holes. Engine block machining process
characteristics; mainly flat and the hole processing, processing of flat generally use planing, milling methods such as processing, processing of hole used mainly boring, processing and multi-purpose drilling holes. As the cylinder complex structure. so how to ensure that the mutual position of the surface processing precision is an important issue.
3.1 The selection of blank
Gearbox shell on the materials used are generally gray cast iron HT150,HT200,HT250,there is also cast aluminum or steel plate, this engine block using high-strength alloy cast iron. Cylinder in the processing prior to aging treatment in order to eliminate stress and improve the rough casting mechanical properties.
Improve the rough accuracy, reduction of machining allowance, is to improve the automated production line system productivity and processing quality of the important measures. As the foreign box-type parts of rough quality and high precision, and its production-line system has been implemented directly on the blank line, not only eliminating the need for blank check device also saves the rough quality problems due to waste of machining time, increase overall efficiency. Therefore, the refinement of rough is to improve the productivity of the most promising way out. For the engine block production line, can be rough in parts on-line pre-milling six face, removing most of the margin, to facilitate direct on-line parts.
3.2 Machining process selection and processing of the benchmark
Choose the right processing technology base is directly related to the processing quality can ensure the parts. Generally speaking, process benchmarking can be divided into coarse and fine reference base.
3.2.1 Coarse reference base
The baseline for the on-line thick rough ,which is particularly important the choice of benchmark crude, if crude benchmark choice unreasonable, will the uneven distribution of machining allowance, processing and surface offsets, resulting in waste.
In the cylinder production line, we have adopted for the coarse side of the base;
3.2.2 Fine reference base
Refined the base of this box for the engine block parts, the general use of "side two sales "for a full range of uniform benchmarks, For the longer automated production positioning. In the gearbox shell of the process, we have adopted to the side, bottom and the spindle hole positioning, in the processing center on the process.
3.3 Machining Processing Stages and processes of the arrangements
Often a part of many apparent need for processing, of course, the surface machining accuracy are different. Processing of high precision surface, often after repeated processing; As for the processing of the surface of low precision, only need to go through one or two on the list. Thus, when the development process in order to seize the "processing high precision surface, "this conflict, the reasonable arrangement processes and rational division stage of processing. Arrange the order of the principle of process is: after the first coarse refined, the first surface after the hole, the first benchmark other. In the engine block machining, the same should follow this principle.
3.3.1 roughing stage engine block machining process
The arrangements for roughing process, to fully carry out rough rough, trim most of the margin in order to ensure production efficiency;
3.3.2 semi-finishing phase of the engine block machining
In order to ensure the accuracy of the middle of some important surface processing, and arrange some semi-finishing operations, will be required accuracy and surface roughness of the surface of the middle of some processing to complete, while demanding the surface of semi-finished, to prepare for future finishing;
3.3.3 The finishing stage
The finishing stage of requiring high accuracy and surface roughness of the surface processing;
3.3.4 secondary processing
Secondary processing such as small surface screw holes, you can finish of the major surface after the one hand, when the workpiece deformation process little impact at the same time also reduced the rejection rate;In addition,if the main surface of a waste,these small the surface will not have to be processed,thus avoiding a waste of man-hours.However,if the processing is very easy for a small surface bumps the main surface,it should be placed on a small surface finish prior to the main surface finishing;
3.3.5 make proper arrangements for secondary processes
Make proper arrangements for secondary processes such as product inspection process,in part roughing stage,the key process before and after processing,spare parts all the processing has been completed,should be appropriate arrangements.
Stage of processing division,has the following advantages:First,it can take measures to eliminate the rough workpiece after the stress,to ensure accuracy; second,finishing on the back,and will not damage during transport the surface of the workpiece has been processed;again,first roughing the surface defects can be detected early and promptly deal with rough,do not waste working hours.But most small parts,do not sub very thin.
3.4 The gearbox shell surface of the main processing and secondary processes
3.4.1 Plane processing
Plane processing at present, the milling of engine blocks is the primary means of planar processing,domestic milling feed rate is generally 300-400mm/min,and foreign 2000-4000mm/min milling feed rate compared to far cry,to be on increasing,therefore,improve the milling feed rate,reduce overhead time is to improve the productivity of the major means of finishing a number of plane engine block when the milling feed rate to reach 2399mm/min,greatly improved efficiency;
Top surface of the cylinder milling is a key process in the process,the flatness
requirements for 0.02/145mm,the surface roughness of Ra1.6um.Processing in the cylinder,the use of side and spindle bearing bore positioning,top,bottom and middle vagay only aperture while processing used in the processing line outside of the knife device can better meet the engine block machining accuracy;
3.4.2 General holes Machining
General holes Machining holes in general are still using the traditional processing of drilling,expansion,boring,reaming,tapping and other craft approach. Issues in the design process of specific programs,use of coated cutting tools,cutting tools and other advanced tools within the cooling,and using a large flow of cooling systems,greatly improving the cutting speed,improved productivity;
3.4.3 Deep hole processing
Deep hole processing of the traditional processing method is used to grade twist drill feed,low efficiency of their production,processing and quality is poor.The deep hole in the engine block processing,the use of gun drilling process;
3.4.4 Cleaning
Cleaning is divided into wet cleaning and dry cleaning.Machining cylinder automatic production line using a large flow of wet cleaning;
3.4.5 Detection
Detect points outside the line detection and line detection of two kinds. Quality inspection in the engine block,according to the actual situation with lines outside the detection,the main use of coordinate measuring machine integrated measurements of the cylinder,each 200 samples 1-5 pieces,each class random one.
变速箱壳体机械加工工艺设计
摘自： 《机械工程与技术（机加工）》（英文版）
机械工业出版社 2004年3月第1版 p560—564
美 s. 卡卡尔帕基安 s.r 施密德
摘要
变速箱壳体是变速器机零件中结构较为复杂的箱体零件，其精度要求高，加工工艺复杂，并且加工加工质量的好坏直接影响发动机整个机构的性能，因此，它成为各个发动机生产厂家所关注的重点零件之一。机械加工工艺规程必须保证零件的加工质量，达到设计图纸规定的各项技术要求，同时还应该具有较高的生产率和经济性。因此，机械加工工艺规程设计是一项重要的工作，要求设计者必须具有丰富的生产实践经验和广博的机械制造工艺基础理论知识。
1. 变速箱壳体的工艺特点
变速箱壳体的工艺特点是：结构、形状复杂；加工的平面和孔比较多；壁厚不均，刚度低；加工精度要求高，属于典型的箱体类加工零件。变速箱的主要加工表面有顶面、孔系、主轴承孔及螺纹孔等，它们的加工精度将直接影响发动机的装配精度和工作性能，主要依靠设备进度、工夹具的可靠性和加工工艺的合理性来保证。
2. 变速箱壳体工艺方案设计原则和依据
设计工艺方案应在保证产品质量的同时，充分考虑生产周期、成本和环境保护；根据本企业能力，积极采用国内外先进的工艺技术和装备，不断提高企业工艺水平。变速箱壳体机械加工工艺设计应遵循以下基本原则：
2.1加工设备选型原则
加工设备选型采用刚柔结合的原则，加工设备以卧式加工中心为主，少量采用立式加工中心，关键工序—曲轴孔、缸孔、平衡轴孔加工采用高精度高速卧式加工中心，非关键工序—上下前后四个平面的粗铣采用高效并有一定调整范围的专用机床加工；
2.2 集中工序原则
关键工序—曲轴孔、缸孔、平衡轴孔的精加工缸盖结合面的精铣，采用在集中在一道工序一次装夹完成全部加工内容方案，以确保产品精度满足缸体关键品质的工艺性能和有关技术要求。
3. 发动机缸体机械加工工艺设计的主要内容
发动机缸体结构复杂，精度要求高，尺寸较大，是薄壁零件，有若干精度要求较高的平面和孔。发动机缸体机械加工的工艺特点是：主要是平面和孔的加工，加工平面一般采用刨、铣削等方法加工，加工孔主要采用镗削，加工小孔多用钻削。由于缸体结构复杂，因此如何保证各表面的相互位置精度是加工中的一个重要问题。
3.1 毛坯的选择
变速箱壳体采用的材料一般是灰铸铁HT150、HT200、HT250，也有采用铸铝或者钢板的，此发动机缸体采用高强度合金铸铁。缸体在加工前进行时效处理，以消除铸件内应力和改善毛坯的力学性能。
提高毛坯精度，减少加工余量，是提高自动生产线系统生产率及加工质量的重要措施。由于国外箱体类零件毛坯质量和精度较高，其生产线系统已实现了毛坯直接上线，既省去了毛坯检查装置，也节省了由于毛坯质量问题而浪费的加工工时，提高了综合效益。因此，精化毛坯是提高生产率最有潜力的出路。对于发动机缸体生产线，可在零件上线前粗铣六个面，去除大部分余量，便于零件直接上线。
3.2机械加工工艺基准的选择和加工
选择合理的加工工艺基准，直接关系到能否保证零件的加工质量。一般来说，工艺基准可分为粗基准和精基准。
3.2.1 粗基准
粗基准对于上线的毛坯，其粗基准的选择尤为重要，如果粗基准选择不合理，会使加工余量分布不均匀，加工面偏移，造成废品。在缸体生产线中，我们采用侧面作为粗基准；
3.2.2 精基准
粗基准对于发动机缸体这种箱体零件来说，一般采用“一面两销”为全线的统一基准。对于较长的自动自动生产线系统，由于定位销孔在使用过程中的磨损造成定位不准确。在变数箱体的加工中，我们采用了以侧面、底面和主轴孔定位，在加工中心上加工。
3.3 机械加工加工阶段的划分和工序的安排
一个零件往往有许多表面需要加工，当然表面的加工精度是不同的。加工精度较高的表面，往往要经过多次加工；而对于加工精度低的表面，只要经过一两次就行了。因此，拟定工艺顺序时，要抓住“加工精度高的表面”这个矛盾，合理安排工序和合理划分加工阶段。安排工艺顺序的原则是：先粗后精，先面后孔，先基准后其他。在发动机缸体的机械加工中同样应遵循这一原则。
3.3.1 粗加工阶段
在发动机缸体的机械加工过程中，安排粗加工工序，对毛坯全面进行粗加工，切去大部分余量，以保证生产效率；
3.3.2 半精加工阶段
在发动机缸体的机械加工过程中，为了保证一些重要表面的加工精度，安排一些半精加工工序，将精度和表面粗造度要求中等的一些表面加工完成，而对要求高的表面进行半精加工，为以后的精加工做准备；
3.3.3 精加工阶段
对精度和表面粗造度要求高的表面进行加工；
3.3.4 次要小表面的加工
如螺纹孔，可以在精加工主要表面后进行，一方面加工时对工件变形影响不大，同时废品率也降低；另外，如果主要表面出废品后，这些小表面就不必再加
工了，从而避免浪费工时。但是，如果小表面的加工很容易碰伤主要表面时，就应该把小表面加工放在主要表面的精加工之前；
3.3.5 辅助工序也要妥善安排
如检验工序，在零件粗加工阶段之后，关键工序加工前后，零件全部加工完毕后，都要适当安排。
对加工阶段进行划分，具有以下好处：首先，可以在粗加工后采取措施消除工作内应力，保证精度；其次，精加工放在最后面，不至于在运输过程中损坏工件已加工表面；再次，先粗加工各面，可以及早发现毛坯缺陷并及时处理，不会浪费工时。不过对于一般小工件就不要分的很细。
3.4 箱体的主要加工表面和辅助工序
3.4.1 平面加工
目前，铣削是发动机缸体平面加工的主要手段，国内铣削进给量一般为300-400mm/min，与国外铣削进给量2000-4000 mm/min相比，相差甚远，有待于提高，因此，提高铣削进给量，缩短辅助时间，是提高生产效率的主要途径，发动机缸体精加工一些平面时的铣削进给量达到2399mm/min，大大提高了效率；
顶面的铣削是缸体加工中的一个关键工序，其平面度要求为0.02/145mm，表面粗造度为Ra1.6um 。在缸体的加工中，采用侧面和主轴轴承孔定位，顶面、底面和中间瓦盖面同时加工，在加工中采用线外对刀装置，能较好地满足发动机缸体加工精度要求；
3.4.2 一般孔系的加工
一般孔系的加工仍采用传统的钻、扩、镗、铰、攻丝等工艺方法。课题在设计具体的工艺方案时，采用涂层刀具、内冷却刀具等先进刀具，采用大流量冷却系统，大大提高了切削速度，提高了生产率；
3.4.3 深油孔加工
传统的加工方法是采用麻花钻进行分级进给，其生产效率低，加工质量差。在发动机缸体深油孔的加工中，采用枪钻工艺；
3.4.4 清洗
清洗分为湿式清洗和干式清洗。缸体机械加工自动生产线采用大流量湿式清洗；
3.4.5 检测
检测分为在线检测和线外检测两种。在发动机缸体的质量检测中，根据实际情况采用线外检测，主要采用三坐标测量机对缸体进行综合测量，每200件抽查1-5件，每班抽查一件。