1 工艺规程现状

1 status quo of process regulations

工艺规程中每个加工工序都有对应的工序图表，传统模式的工序图表比较简单，工序图表中主要包含零件加工示意图，工作内容，使用的夹模具、刃具、量具号码，完成加工后应满足的尺寸和技术要求及需要注意的事项等。以车削加工工序为例，图1 是零件车削加工工序图表，其左侧草图是加工示意图，通常用二维视图表示，用粗实线表示需要加工的表面，细实线表示非加工表面，用大写字母A、B、C 等表示零件的定位基准、支撑表面、夹紧或压紧表面。示意图中用尺寸线标注被加工表面完成加工后应保证的尺寸和形位公差，每个尺寸和形位公差都标注有顺序号。右侧工作内容栏通常有3 部分内容，一是关于加工前的找正要求，通常要求找正夹具定位表面、零件径向表面和轴向表面的跳动，并规定允许的最大跳动值；二是本工序车削加工的内容，通常用尺寸顺序号表示，与加工示意图中的顺序号对应；三是车削加工后关于形位公差的要求，其序号与加工示意图中的顺序号对应。

Each processing procedure in the process regulations has the corresponding diagram of the process, the traditional mode of the process chart is relatively simple, the process chart mainly contains the part processing diagram, the work content, the used clip mould, the cutting tool and the measuring tool number, complete the size and the technical requirements and the matters needing attention after the processing. Taking the turning process as an example, figure 1 is a diagram of a part turning process. The left sketch is a drawing diagram, usually expressed in a two-dimensional view, a rough line to represent the required surface, a thin solid line to represent a non machined surface, and an upper case letter A, B, C, etc. to represent the positioning datum of the parts, support the surface, clamp, or press. Tighten the surface. In the schematic drawing, the dimension and shape tolerance should be ensured after the finished surface is marked by the dimension line, and the sequence number is marked in each dimension and form tolerance. The right work content bar usually has 3 parts. One is to find the positive requirements before processing. Usually, it is required to find the positioning surface of the positive fixture, the runout of the radial surface and the axial surface of the parts, and to specify the maximum allowable runout value. Two is the content of the turning process in this process, which is usually expressed in the size sequence number and in the processing schematic diagram. The three is the requirement of geometric tolerance after turning, and the serial number corresponds to the sequence number in the schematic diagram.

2 工艺规程现状分析

Analysis on the status of 2 process regulations

2.1 加工前的准备分析

2.1 preparation analysis before processing

加工前工人通常阅读工序图表，若是数控加工工序，还要阅读数控工步卡。工人按照工序图表准备工艺装备，对于工序中使用的通用工艺装备，由于多数工艺文件中没有规定，工人则根据自己的经验和生产车间现有的工艺装备条件进行准备。在选择通用刀具时，由于工人可能对零件、刀具材料的切削性能不清楚，也可能受生产车间刀具储备的限制，工人选择刀具的随意性很大，选择的刀具材料和几何尺寸会出现偏差，使用的切削参数可能不合理，导致零件加工表面质量和尺寸精度不稳定，零件加工成本和周期不稳定，刀具消耗统计不准确，生产准备和生产计划实施困难。同样，工人在选择通用测具时，选择的测量方法可能不准确，选择的测具精度可能不符合被测量尺寸的精度，会导致测量结果不准确。

Before processing, workers usually read the process chart. If NC machining process, we should read the NC step card. The workers prepare the process equipment according to the working procedure chart. For the general process equipment used in the process, the workers are prepared according to their own experience and the existing process and equipment conditions of the production workshop because most of the process documents are not specified. In the choice of general tool, the workers may not be clear about the cutting performance of the parts and tool materials, and may be limited by the tool reserve of the production workshop. The workers choose the cutters with a lot of randomness. The selected tool materials and geometric sizes will be deviant. The number of cutting parameters used may not be reasonable, which leads to the processing table of the parts. Surface quality and dimensional accuracy are unstable, parts processing cost and cycle are not stable, tool consumption statistics are inaccurate, production preparation and production plan implementation is difficult. Similarly, when a worker selects a universal device, the selected measurement method may be inaccurate, and the precision of the selected measuring tool may not conform to the accuracy of the measured size, which will lead to the inaccuracy of the measurement results.

2.2 夹具和零件的安装分析

Analysis of the installation of 2.2 jig and parts

例如在进行夹具和零件的安装操作时，零件的轴心线应尽可能与机床工作台的旋转中心一致，零件的横截面尽可能与机床工作台的旋转中心垂直，以保证零件加工后各表面之间的相互位置要求。对于设计精度要求较高、大尺寸或容易产生加工变形的零件，夹具和零件的安装、找正、压紧或夹紧过程的操作步骤非常关键，对零件的加工精度影响很大。由于工艺规程中没有画出夹具和零件的安装视图及操作步骤，工人只能按照工序图表中草图以及工作内容栏简单的找正要求安装夹具和零件。工艺规程中要求加工前找正零件内孔跳动不大于0.05mm，由于没有明确是对点找正还是连续找正，工人在操作过程中可能会采取对点找正，也可能会采取连续找正。对点找正需要的时间短，容易实现，但找正的结果不精确；连续找正需要的时间长，难度大，但找正的结果比较精确，两种找正方法会导致零件的加工结果有差别。对于零件的压紧，工艺规程中只规定用压板压紧零件表面C，而没有规定实施步骤、压紧力大小和注意事项，工人则根据自己的经验和习惯进行操作，结果是压紧力可能过大或不均匀，零件可能被压伤或产生变形。例如，如果图1 中零件表面B 平面度值较大，压紧前表面B凹陷部位与夹具定位面没有接触，若不将它们之间的间隙消除，压紧后零件产生弹性变形，表面B 凹陷部位与夹具定位面接触，这时被加工表面平面度值很小，但去除压紧力后，零件弹性变形恢复，加工表面平面度随之发生变化；另一种可能出现的情况是，表面B 凹陷部位与夹具定位面之间仍有间隙，切削时在轴向切削力的作用下零件局部产生弹性变形，同时容易产生振动。

For example, when the fixture and parts are installed, the axis line of the part should be as much as possible with the rotating center of the machine tool table, and the cross section of the part is perpendicular to the rotating center of the machine tool table so as to ensure the mutual position between the surfaces after the parts are processed. For parts with high design precision, large size or easy to produce machining deformation, the installation of fixture and parts, the procedure of finding positive, pressing or clamping process are very important, and it has a great influence on the machining precision of the parts. Because the installation view and operation procedure of the fixture and parts are not drawn in the process regulations, the workers can only install the fixture and the parts according to the sketch in the process chart and the simple finding of the work content bar. In the process of process, it is required that the beating of the inner hole of the positive part before processing is not more than 0.05mm. Because there is no clear or continuous search for the correct point, the workers may take the right point in the operation process, and may also take continuous search. The time to find the point is short and easy to be realized, but the result of finding the positive is not accurate; it is difficult to find the correct time, but the finding of the positive results is more accurate. The two kinds of finding methods will result in the difference in the processing results of the parts. For the pressing of the parts, the process regulations only stipulate that the press plate is pressed to press the C of the surface of the parts, but the steps, the size of the pressing force and the matters of attention are not stipulated. The workers operate according to their own experience and habits. The result is that the pressure may be too large or uneven, and the parts may be crushed or deformed. For example, if the B flatness of the surface of the part on the part of Figure 1 is larger, the B concave part of the front surface has no contact with the fixture location. If the gap between them is not eliminated, the part produces elastic deformation after pressing, the surface of the surface is in contact with the fixture location, and the surface flatness of the machined surface is very small, but the pressure is removed. After the force, the elastic deformation of the parts is restored, and the surface flatness of the machined surface will change. Another possible case is that there is still a gap between the B concave part of the surface and the positioning surface of the fixture, and the part produces elastic deformation in the part of the part under the action of the axial cutting force, and the vibration can be easily produced at the same time.

2.3 加工过程分析

2.3 process analysis

在对零件进行切削加工时，工人按照工作内容栏的尺寸序号及草图中对应的尺寸进行加工。对于普通切削加工工序，工人根据自己的加工经验和习惯安排零件表面的加工顺序、切削走刀路径和切削参数; 对于数控加工工序，数控编程员则根据自己的工艺经验和习惯来安排上述内容。由于工人和数控编程员对机械加工技术掌握的局限性以及思维的习惯性，在安排零件表面的加工顺序、切削走刀路径、切削参数时，通常更多考虑是否方便加工，而较少考虑零件结构的差异，较少考虑对刀具寿命的影响，更少考虑切削力、切削应力对零件加工变形的影响。如果零件在一个工序中需要加工的表面数量较多，当加工表面

When machining parts, workers are processed according to the size of work contents column and the corresponding dimensions in the sketch. For the ordinary cutting process, the workers arrange the processing order, cutting path and cutting parameters of the surface of the parts according to their own processing experience and custom. For the NC machining procedure, the NC programmer arranges the above content according to his own process experience and habit. Due to the limitations of workers and CNC programmers on machining technology and the habit of thinking, it is usually more considered to be convenient for machining sequence, cutting tool path and cutting parameters, while less consideration of the difference of part structure, less influence on tool life and less influence on tool life. The influence of cutting force and cutting stress on machining deformation of parts is considered. If the number of surfaces that a part needs to be machined in a process is larger, the machined surface should be machined.