Mapping Units and Representation of Assembly Drawings(部件测绘与装配图的画法)

In practice,the procedure that is composed of measuring the machine or equipment,producing schematic drawings and then producing the assembly drawings is called a mapping process. It is a basic skill for engineering personnel to be able to map the units. In this section, we take a flat nose clamp (Fig. 9-23) as an example and briefly introduce the method and steps to produce an assembly drawing. 

在生产实践中,对机器或设备进行测量,绘出草图,然后整理绘制出装配图的过程称为部件测绘。部件测绘是工程技术人员应该必备的一项技能。下面以平口钳(图9-23)为例,简述通过部件测绘画装配图的方法和步骤。

 Understanding the subassembly (了解部件)


Produce an assembly sketch map based on the understanding of the purpose, working principle,relationship between assembly, transmission routes of the assembly, and the basic structures of major parts of the assembly. 

弄清装配体的用途、工作原理、装配关系、传动路线及主要零件的基本结构。

(1)Understandingof the purpose  Flat nose clamp is used to fix workpiece for machining.

(2) Understanding of the working principle and transmission route  Turn the screw with the handle to drive thenut and to make the movable body of the clamp to perform rectilinear movements along the fixed body of the pliers. This will make the mouth of the clamp open or close to clamp or unload the part.

(3) Understanding of there lationship between assembly, basic structures of the major parts  Fig. 9-23 is an axonometric exploded drawing showing the fitting relationship of the flat nose clamp. It consists of eleven kinds of parts including a fixed clamp body, a screw, a nut and others. The nut and the movable clamp body are connected as a unit. The dummy club under the nut contactsthe fixed body of the clamp. When the screw rotates, the nut moves rectilinearly,but not rotationally. The boards are fastened to both bodies of the clamp with screws. The left side of the screw rod has a ring connected to the screw rod with a pin. 

(1)了解用途  平口钳是装在机床工作台上用来夹紧工件。

(2)了解工作原理与传动路线 用手柄转动螺杆,使螺杆带动螺母,进而带动活动钳身沿着固定钳身作直线运动,从而使钳口张开或闭合,即可夹紧或卸下零件。

(3)了解装配关系及主要零件基本结构  图9-23为平口钳零部件装配关系轴测分解图。它是由固定钳身、螺杆、螺母等11种零件组成。螺母与活动钳身用螺钉连成一体,螺母下方凸出的台阶与固定钳身接触。当螺杆转动时,螺母只作直线运动,不作旋转运动。钳口板是用螺钉分别固定在活动钳身和固定钳身上。螺杆左端有一个环用销钉与螺杆固定。

Drafting the assembly schematic drawings(画装配示意图)


While understanding a new assembly or while disassembling an old machine, one should draw an assembly schematic drawing in order to facilitate reassembly and as a reference. In other words, draw the contour of each part with specified symbols and lines that indicate the fitting relationship, their relative position, transmission conditions and working principles, as shown in Fig. 9-24.

在了解或拆卸装配体的过程中,应画出装配示意图,即用规定符号和简单图线画出装配体各零件的大致轮廓,用以说明各零件之间的装配关系和相对位置,以及传递情况和工作原理等,如图9-24所示。装配示意图的作用是为了方便将拆散的装配体复原,也可以作为画装配图时的参考。

The following items should be noticed when producing an assembly schematic drawings:

1) A schematic drawing is produced as if the assembly is transparent, so both internal and external structures can be reflected. 

2) Each part is represented with approximate contours or a single line.

3) See specified symbols of commonly used parts in the standard Technical Drawing and Mechanical Drawing GB/T 4460—1984.

4) Only one or two views are generally needed when producing schematic drawings. There should be a gap between contact surfaces in order to identify related parts.

5) Parts in schematic drawings should be numbered. The list shows the name, quantity and material. The part name and number of the simple assembly can be written on the assembly schematic drawings, as shown in Fig. 9-24.

画装配示意图应注意以下几点:

1) 示意图是将装配体假想设为透明体而画出的,因而外形轮廓和内部构造均可反映出来。

2)每个零件只画大致轮廓,或用单线表示。

3)常用零件的基本符号参见国家标准《机械制图 机构运动简图符号》GB/T4460—1984。 

4)示意图一般只画一、两个视图。两个零件接触表面应留出空隙,以便区分零件。

5)示意图一般应编出零件序号,列表写出零件的名称、数量、材料等项目。简单装配体的装配示意图也可直接把零件名称、序号注写在示意图上,如图9-24所示。

Mapping the assembly (测绘装配体)

Please note the following when mapping an assembly:

 1) Disassembly. Disassembly should be performed in accordance with appropriate methods and steps to ensure the safety and integrity of the parts. One should think about the sequence of disassembly before processing and all parts should be numbered in accordance with the disassembly sequence. Small parts should be carefully stored so as to avoid losing or mixing them with other parts. Reassemble after the mapping is finished.

2) Measurement. While performing mapping, make sure to protect the machining surface and fitting surface of the part. When measuring, select the right measuring tools according to the required part accuracy. Unimportant dimensions should be changed into integers, but do not change decimal fractions of dimensions that require higher accuracy. For fitting dimensions, one only needs to measure its basic dimension, and then select the appropriate class according to its specific condition.

3) Material of the part. One can determine the material from its appearance whether it is steel, cast iron, cast steel, or non-ferrous metal. According to the purpose and working conditions, compare products of the same type when choosing the material brand. 

测绘装配体应注意以下几点:

 1)装配体拆装问题。  为了保证安全和不损坏机件,拆装要按照一定的方法、步骤进行。因此应先研究好拆装顺序,再动手拆装。零件拆下后可按拆卸顺序把零件编上号码。小零件要妥善保管,以防丢失或发生混乱现象。测绘完成后,应将装配体复原。

2)测量问题。  在测绘中,要注意保护零件的加工面和配合面。测量尺寸时,要根据零件的精度要求选用相应的量具。对非主要尺寸,应将测得的尺寸化为整数。对精度要求较高的主要尺寸和数值比较小的尺寸,不能任意改变尺寸的小数值,而应经过认真推敲,采用合理的数值。对配合尺寸,一般只测量出基本尺寸,再根据具体条件选用合理的配合类别的等级。

3)零件材料的确定。  一般可先从外观判断是钢、铸铁、铸钢、有色金属等大类别,再根据零件的作用和工作条件,对比同类型产品,选定材料的牌号。

Determining the representation(确定表达方案)


Choose the projection of the front view and determine its drawing size and scale. Apply various representations to improve understanding.

选择主视图方向,确定图幅及绘图比例,合理运用各种表达方法。

Choose the front view for the flat nose clamp according to the above-mentioned principles, and then determine the following representations through analysis: the front view is a full sectional view cut along the front and back symmetry plane; the left side view is a half sectional view or a partially sectioned view cut along the two holes of the fixed clamp body; and the top view is a partially sectioned view cut at the screw connecting to the board of the clamp mouth; use a partial direction view B to represent the reticule shape of the board of the clamp mouth; use a drawing of partial enlargement to represent the form of thread on the screw rod; use a cut to represent the structure of the cut plane of the right end of the screw rod, as shown in Fig. 9-25.According to scale 1:1, one needs to use an A2 drawing sheet. 



根据前面所讲的主视图选择原则,选好平口钳主视图,并经分析比较,确定以下表达方案:主视图沿前后对称面全剖;左视图沿固定钳身两孔处半剖或局部剖;俯视图在螺钉连接钳口板处局部剖;采用B向局部视图表达钳口板表面网纹形状;再用局部放大图表达螺杆的螺纹牙形;还采用断面图表达螺杆右端部切有方头处的断面结构,如图9-25所示。按照1:1的比例,需要采用A2号图纸。

 Preliminary drafting(画出底稿)


First, draw the border, title block and item block. Second,position the views and draw the datum lines. Then, draw the major parts on the front view. Draw other parts according to their fitting relationships. When drafting,first map the major parts and draw the schematic drawings. next produce the assembly drawing according to the schematic drawings.

先画图框、标题栏及明细栏;再布置视图,画出基准线;然后从主视图入手,画主要零件;最后根据装配关系依次画出其余零件。在画底稿时,应先将主要零件测绘后画出草图,再根据零件草图和装配示意图画装配图.

General steps for preliminary drafting (Using 2H or H pencil and compass):

1) Draw the border and title block.

2) Specify the drawing's position in the borders according to 3:4:3(Fig. 9-26), then draw the datum lines, lines of symmetry and axis shaft lines.

3)According to the three-alignment rules of different views, first draw the major parts, and then draw the neighboring parts.

4)Draw the detailed structure of each part and complete the drawing. Pay attention to the fitting relationship between contact surfaces and non-contact surfaces.

5) Draw the dimension boundaries, dimension lines, number leaders, and complete the entire drawing. 

画底稿的一般步骤(用2H或H的硬芯铅笔及圆规) :

1)画图幅边框、图框及标题栏。

2)按3:4:3布局法确定图形在图框中的位置(图9-26),再画各图形的基准线、对称线、轴线等。

3)按三等规律先画其主要零件,然后根据各零件的连接关系,从相邻零件开始,依次画出其他零件。

4)画各零件的细小结构,完成全部图形。注意分清零件接触面和非接触面的装配关系。

5)画尺寸界线、尺寸线、序号指引线等。

Completing the entire drawing(完成全图)


Draw the section lines,mark the dimensions, set the numbering, fill in the title block, item lists, signatures and technical requirements, and finally complete the drawing with appropriate line styles following related standards and requirements(Fig. 9-27).

画剖面线、标注尺寸、编排零件序号、填写标题栏、明细栏及注写技术要求,按标准加深图线,如图9-27所示。  

Final check(全面校核)

Check the entire content of the drawing. Correct any errors, then sign in the title block and complete the entire drawing.

对图中所有内容进行仔细、全面的校核,将错、漏处改正后,在标题栏内签名,完成全图。