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1、An automated welding operation planning systemfor block assembly in shipbuildingKyu-Kab Cho*, Jung-Guy Sun, Jung-Soo OhAbstractThe block assembly process is one of the most important manufacturing processes for shipbuilding. Since block is composed of several steel plates and steel sections with pre

2、determined shapes according to ship design, the welding operation planning to construct a block is a critical activity for shipbuilding, but this activity has traditionally been experience based. Thus, it is required to develop an automated welding operation planning system to assemble blocks. This

3、paper describes the development of an automated welding operation planning system for block assembly in shipbuilding. Based on the information about parts, topological relationship between parts and assembly sequences for block, the developed system performs the determination of welding postures, we

4、lding methods, welding equipment and welding materials. The developed system implemented successfully for real blocks constructed in shipyard.Keywords: Block assembly; Expert system; Operation planning; Welding process1. IntroductionShipbuilding is traditionally a labor-intensive assembly industry t

5、hat employs the welding process as a basic production technology. In shipbuilding, there are several types of manufacturing process planning for cutting and bending, assembly, out- fitting, and erection. Among these process planning activities, the assembly process planning is by far the most import

6、ant, since the construction process for a hull block comprises approximately 4850% of the total shipbuilding process 1,2. The main operation for block assembly is the welding operation. The welding operation planning problems in block assembly are very difficult to solve because all blocks are diffe

7、rent in size, type, and constituting sub-assemblies that depend on the types of ships. Also, since this activity has traditionally been experienced-based, welding operation planning in shipbuilding has been performed manually. Thus, it is very important to develop an automated weldingoperation plann

8、ing system for shipbuilding. There is relatively very little literature available on automated welding operation planning systems for shipbuilding 3,4. This paper deals with the development of an automated welding operation planning system for block assembly in shipbuilding. The rule-based expert sy

9、stem for welding operations has been developed using Smart Elements as an expert system tool. The developed system is demonstrated and verified by using actual blocks in the shipyard.2. Development of an automated welding operation planning system2.1. System frameworkThe automated welding operation

10、planning system developed in this paper consists of four modules: welding postures module, welding methods module, welding equipment module, and welding materials module. The framework of this system is shown in Fig. 1.2.2. Determination of welding posturesThis module determines the posture of the w

11、elding operator. Welding posture is reasoned by considering connection types and positional direction between two connected parts, direction information of assembly base part, existence of turnover, and assembly level.Connection types are classified into butt type (B) and fillet type (T), as shown i

12、n Fig. 2. The four types of welding postures, down posture (D), overhead posture (O), horizontal posture (H), and vertical posture (V), are considered in this paper, as shown in Fig. 2 5,6. The most stable and easiest welding posture is the down welding posture, and the most difficult one is the ove

13、rhead welding posture. The welding operator determines an efficient welding posture according to the working conditions.For relationship of connection between two parts that are welded, one part is considered as the base and the other is connected to the base. The part that is considered as a base i

14、s represented as PartFrom and the other that is connected to the base is represented as PartTo. The levels of block assembly to assemble steel plates and sections into the final block are classified into subassembly (SA) level, unit block assembly (UBA) level, and final block assembly (FBA) level.Su

15、bassembly levels may be divided into small subassembly (SSA) levels and intermediate subassembly (ISA) levels according to the size and weight of the subassembly as shown in Fig. 3.For determining welding postures, the block assembly levels are classified into two groups. The first group is the smal

16、l subassembly level; the second group consists of the intermediate subassembly, the unit block assembly, and the final block assembly levels. The reason for this grouping is that there is no turnover process in the small subassemblylevel, but the assembly levels belonging to the second group may hav

17、e turnover processes. Turnover processes cause the change of welding postures that are determined before the turnover process.2.2.1. Determining welding postures in the first group levelThe following are examples of rules to determine the welding posture for a small subassembly level. The connection

18、 types of welding joints between two parts used in this rule are: Butt type (0) and T type (1).(1) IF (Part Level=Small Assembly)(Connection Type=1)(Direction of Assembly Base=Connection Direction)(PartFrom=not Assembly Base Part)(PartTo=not Assembly Base Part)THEN (Welding Posture=H)(2) IF (Part Le

19、vel=Small Assembly)(Connection Type=1)(Direction of Assembly Base Part=not Connection Direction)(PartFrom=not Assembly Base Part)(PartTo=not Assembly Base Part)THEN (Welding Posture=V)An example of a small subassembly is shown in Fig. 4. In this case, there are ve parts, and the assembly base parts

20、are A and B. The relationships between the parts are listed in Table 1 and the results of the determination of welding postures for this example are shown in Table 2.2.2.2. Determining welding postures in the second group levelsIn the second group levels, information for determining welding postures

21、 is the same as for the small subassembly level. Welding postures are determined between the assembly base part and other parts that are connected to the assembly base part in a similar way to the small subassembly. Other welding postures are determined between parts that are not an assembly base pa

22、rt. If turnover processes exist, the direction of the assembly base part is changed at an angle of 180 and the welding posture is also changed. An example of the rules for the second group levels are as follows:(1) IF (Part Levelnot Small Assembly)(Connection Type is 0)(Direction of Assembly Base Pa

23、rtConnection Direction)(PartFromnot Assembly Base Part)(PartTonot Assembly Base Part)THEN (Welding PostureH)(2) IF (Part Levelnot Small Assembly)(Connection Type0)(Direction of Assembly Base Partnot Connection Direction)(PartFromnot Assembly Base Part)(PartTonot Assembly Base Part)THEN (Welding Post

24、ureV)2.3. Determination of welding methodsThis module determines the welding methods based on welding postures by rule-based reasoning. Welding methods used in this paper are summarized in Table 3, according to the connection types of welding joints and welding processes 7.In general, there are seve

25、ral welding techniques such as braze welding, forge welding, gas welding, resistance welding, induction welding, arc welding, and special welding. Considering the features of shipbuilding, the welding process used in the shipyard is the arc welding process. Arc welding is a process in which coalesce

26、nce is obtained by heat produced from an electric arc between the work and an electrode 8.Arc welding is classified into several types, according to the welding mechanisms such as shield metal arc welding (SMAW), flux cored arc welding (FCAW), submerged arc welding (SAW), and electrogas arc welding

27、(EGW). SMAW is one of the oldest, simplest, and most versatile joining processes. Currently, about 50% of most industrial and maintenance welding is performed by this process, but this process is used approximately less than 5% at most large shipyards. In FCAW, an electrode that is tubular in shape

28、is used, and if necessary, the welding area is shielded by carbon dioxide. In SAW, the weld arc is shielded by granular flux, consisting of lime, silica, manganese oxide, calcium fluoride, and other materials. The flux is fed into the weld zone by gravity flow through a nozzle. EGW is used primarily

29、 for welding the edges of sections vertically in one pass, with the pieces placed edge to edge (butt type) 9. To build the knowledge base for the determination of welding methods, knowledge is aquired from welding handbooks and experts. Input information of this module is geometrical information tha

30、t is provided from CAD system and the welding posture determined by welding posture determination module. The knowledge is represented by rules. The examples of the rule for the determination of welding methods are as follows:(1) IF (Connection Type=0)(Groove=none)(Welding Posture=O)(6Thickness50)TH

31、EN (Welding Method=SMAW-MANUAL BUTT)(2) IF (Connection Type=1)(Leg Length4.5mm)(Welding Posture=O, H, V)THEN (Welding Method=FCAW-FILLET)2.4. Determination of welding equipmentThis module selects the appropriate welding equipment by rule-based reasoning based on information about welding postures an

32、d welding methods. Table 4 shows the relationship between welding methods and welding equipment. After determining welding methods, welding equipment is automatically selected by using the information contained in Table 4.2.5. Determination of welding materialsThis module determines the most proper

33、welding materials by rule-based reasoning, based on information about welding postures, methods, and equipment. In general, steels used for block assembly are mild steels and high tensile steels. Mild steel is a rolled plate, the tensile strength of which is less than 50 kg f/mm2. High tensile steel

34、 is a low-carbon alloy steel, the tensile strength of which is more than 50 kg f/mm2 with a yield strength of more than 30 kg f/mm2. Mild steel has four grades: A, B, D, and E. High tensile steel has three grades: AH, DH, and EH 9. The following are examples of rules to determine welding materials.(

35、1) IF (Welding Posture=D)(Welding Methods=FCAW FILLET)(Welding Equipment=LN-7 or LN-9)(Steel Grade=(Mild Steel A,B,D,E) Highten-sile Steel AH,DH)THEN (Welding Material=MX-200H)(2) (Welding Posture=D)(Welding Methods=SAW Bothside BUTT)(Welding Equipment=SW-41)(Steel Grade=Mild Steel A,B,D,E)THEN (Wel

36、ding Material=L-8xs-707EF H-14XS705EF L-8XNSH52)3. System implementation and discussionsIn order to demonstrate and to verify the automated welding operation planning system for block assembly, a block located at the upper deck part of crude oil carrier is examined. Fig. 5 shows the structure of an

37、example block and Fig. 6 represents its hierarchical structure. An example final block shown in Fig. 5 has two unit blocks, one intermediate subassembly, 15 small subassemblies, and 169 component parts. The final welding operation planning for the unit block assembly level is shown in Fig. 7. The re

38、sults are verified by an expert process planner and implemented by using actual blocks in an assembly shop.4. ConclusionAn automatic welding operation planning system consisting of four modules (welding postures, welding methods, welding equipment, and welding materials) is developed by using Smart

39、Elements as an expert system tool. The developed system is verified by using actual block and implemented in a block assembly shop.AcknowledgementsThis work is supported by the research grant from Hyundai Heavy Industries Co., Ltd.References1 H. Nakayama, Expert process planning system of CIM for sh

40、ipbuilding, Proceedings of International Conference on Computer Applications in Shipbuilding, 1994, pp. 12.5512.66.2 Ship and Ocean Foundation, Research Report on Shipbuilding CIMS Pilot Model Development, Japan, 1991.3 H.B. Cary, Summary of computer programs for welding engineering, Welding Journal

41、 70 (1) (1991) 4046.4 D.M. Barborak, D.W. Dickinson, R.B. Madigan, PC-based expert system and their applications to welding, Welding Journal 70 (1) (1991) 2938.5 J. Weber et al., Welding expert focus on the future, Welding Journal 69(7) (1990) 3746.6 K.K. Cho et al., An automatic process planning sy

42、stem for block assembly in shipbuilding, Annals of the CIRP 45 (1) (1996) 4144.7 J. Gustafsson, M. Heinakari, Experiences with CIM in shipbuilding, Welding Journal 70 (3) (1991) 2735.8 B.H. Amstead et al., Manufacturing Processes, 8th ed., Wiley, New York, 1987, pp. 156157.9 S. Kalpakjian, Manufactu

43、ring Engineering and Technology, 3rd, Addison-Wesley, Reading, MA, 1995, pp.862870.自动焊接操作系统Kyu-Kab Cho*, Jung-Guy Sun, Jung-Soo Oh摘要：船舶建造的分组装配作业加工是其最重要的制造法。因为块由若干钢板块和型钢同预定形状按照船舶设计组成的，所以对船舶建造来说焊接操作计划构造块是一项关键任务，但是这个是以传统经验为基础的，因此，有必要研制一种自动焊接操作计划系统来组装块。这篇论文描述了船舶建造分组装配作业的自动焊接操作计划系统的发展。根据零件和装配次序的拓扑关系介绍部分，

44、系统完成确定焊接位置，焊接方法，焊接设备和焊接材料。系统成功地实现了船舶建造块的构造。关键词：分组装配作业；专家系统；操作计划；焊接过程 简介船舶建造是传统的劳动强度大的组装工业，焊接是其基本生产技术。在船舶建造中,存在几种类型切割,装配制造法。在这些工艺设计活动之中,装配工艺计划是最重要的,因为船体结构加工大约包含了船舶建造加工总数的40%-50%。焊接操作是分组装配作业的主要操作。焊接操作规划问题在装配过程中是很难解决的，因为部件的大小, 类型,以及组成的取决于船的类型的亚部件是不同。同样地，因为这些活动是以传统经验为基础的，所以，焊接操作在船舶建造中是人工执行的。因此，在船舶建造中，研制

45、自动焊接操作计划系统是非常重要的。对船舶建造，几乎没有自动焊接操作计划系统的文献可以利用。这篇论文涉及船舶建造分组装配作业的自动焊接操作计划系统的研制。这种基于规则的将灵敏元件当做专家系统工具的焊接操作专家系统已经被研制出来了。这个系统通过造船厂的实际的部件已经被证明和复核。 自动焊接操作系统的发展2.1. 系统框架在此论文里自动焊接操作计划系统由焊接位置模数、焊接方法模数、焊接设备模数，并且焊接材料模数组成四模数。这个系统的框架将在图1中展示。2.2. 焊接位置的确定模数决定焊工的焊接位置。考虑到两连接零件连接类型和位置，方向部件的方向信息，翻转的存在以及装配等级等因素，焊接位置是受影响的。

46、连接类型被分为对接和角接类型，如图所示。这篇论文考虑了四种焊接位置:向下焊接，水平焊接，垂直焊接和仰焊接，如图所示。最稳定的和轻松的焊接位置是下向焊位置，最困难的是仰焊位置。根据工作条件焊工决定采用一种有效的焊接位置。两焊接部的连接的关系，一个部分被认为是基体，而另一个被认为是连接在这个基体上。被认为是基体的部分被当做partfrom而连接到基体的部分被当做PartTo。装配钢板和型钢变成最后的部件的分组装配作业水平被分为组件水平（SA），单元块组装水平（UBA）和最后的分组装配作业水平（FBA）。根据组件的尺寸和重量组件水平可以被分成小组件水平（SSA）和中间的组件水平（ISA）如图所示。因

47、为决定焊接位置,分组装配作业水平被分为组。第一个组是小部件水平；第二组由中间部件组成，为单元块组装和最后的分组装配作业水平。这样分组的理由是看是否有翻转的加工小部件，但是装配水平属于第二组的也许也有翻转加工。翻转加工之前的决定产生致使焊接位置发生变化。2.2.1. 决定焊接位置的第一组水平以下用来决定焊接位置的规则适合于小部件水平。用于此规则焊接接头的连接类型是：对接式（0）和T类型（1）。(1) IF (Part Level=Small Assembly)(Connection Type=1)(Direction of Assembly Base=Connection Direction)(

48、PartFrom=not Assembly Base Part)(PartTo=not Assembly Base Part)THEN (Welding Posture=H)(2) IF (Part Level=SmallAssembly)(Connection Type=1)(Direction of Assembly Base Part=not Connection Direction)(PartFrom=not Assembly Base Part)(PartTo=not Assembly Base Part)THEN (Welding Posture=V)小部件的例子在图中列出。这里有五部分，部件基体部分是A和B。这些部分之间的关系在表格1中列出，这些例子确定焊接位置的结果将在表格中列出。2.2.2. 决定焊接位置的第二组类水平在第二组类水平, 决定焊接位置的情况同小部件水平是一样的。其他的焊接位置取决于非部件基体间的部件。如果存在翻转加工，部件基体的方向是以180的角度变化，焊接位置也同样地变化。适合于第二组类水平的例子规则的如下：