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旅行箱拖手塑料套及注射模具设计【12张CAD图纸+毕业答辩论文】【注塑模具】

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关键词：: 旅行箱拖手塑料注射模具设计全套 cad 图纸毕业答辩论文注塑模具

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摘要

本文为旅行箱拖手塑料套的产品设计到整个注塑模的设计过程，即对长140mm、宽30mm、高20mm拖手塑料套的注塑模具设计。塑料套的外形设计有防滑纹理，在侧边设有固定的螺丝孔以便固定在伸缩支架上。其螺钉孔根据设计要求采用侧向抽芯机构进行抽芯，然后通过顶杆将制件顶出。稳重介绍了拖手塑料套的外形、结构等设计要求，制件的结构分析，制件的工艺性分析，制件质量、体积计算，材料、生产批量的确定，成型方法的选取及成型设备的选择，注塑模的结构设计，在设计模具时的相关计算，模具机构设计，注射机的选择及其校核，成型零件的相关计算及其校核。在设计中进行大量的计算，如成型零件工作尺寸的计算，型芯、型腔径向和高度计算，推杆直径及其数目的计算等。由此在整个设计计算的过程中，确定了模具的结构及相关的零部件。在整个模具的设计过程中采用CAD/CAM设计系统进行一体化设计，用PROE软件进行塑件的三维造型及其分析，用AUTOCAD进行二维的工程图二维设计。

关键词：注塑模；塑料；抽芯；型腔；型芯

Abstract

About mold development trend, I think it depends mainly on two aspects, that is, on the one hand is development trend of the mold service for all walks of life, on the other hand, the whole society and the world trend of the development of science and technology, it is actually need and possible. Molds for the parts, that is, forming products and services, so the mold must to stamping forming products () for their own development trend, the development trend of die must meet their requirements. Development trend of the main parts is light and elegant, fast and efficient production, low cost and high quality, each announced a mold development trend.

The thesis gives a detailed introduction the process of an injection mold’s design, which is from product design to the whole plastic injection mold. This is a design for a plastic injection mold whose length is 140mm, 20mm in width, 20mm in height. The form design for a plastic sleeve has skidproof textures. Its broadside has screw eyes . The function of the hole is used to fix plastic sleeve on the telescoping shoring column. According to the design, its screw eyes are required to use a side core-pulling mechanism to do side core-pulling. After that, the knockout pin pushes out a fabricated part. This paper introduces the design standards of a drag hand plastic’s form, structure, etc, the process analysis of a fabricated part’s quality, volume calculation,materials, the confirm of production lot, the choice of molding methods and the choice of mold equipment, the injection’s structural design, the relative calculation in designing a mold, a mold’s mechanism design, the choice and check of an injection machine, relative calculation and check about molded parts. Meanwhile, it explains the working processes. Plenty of calculations during the design are the calculation of working dimensions for molded parts, the calculations of core, cavity diameter and the mold’s height, the calculation of a push rod’s diameter and the number of push rods, etc. So, the mold’s structure and some relative components are confirmed during the process of the calculation in the whole design. CAD/CAM design system is applied to in the design process of the whole mold. At the same time, PROE software is used to form 3D mold and its analysis, AUTOCAD is used to export 2Dengineering drawing.

Keywords: Injection mold; plastic; pumping core; cavity;core

引言1

1 塑件设计分析2

1.1 选题意义2

1.2 塑件模型建立2

1.3 塑件参数设计2

1.4 材料选择3

1.5 塑件的壁厚4

1.6 塑件的脱模斜度4

1.7 分型面设计5

1.8 确定型腔数量以及排列方式6

2 注塑设备和模架选择7

2.1 注塑设备选择7

2.2注塑机重要参数校核9

2.2.1型腔数量的确定和校核9

2.2.2 注塑容量校核9

2.2.3 锁模力校核10

2.2.4 注塑压力校核11

2.2.5 开模行程校核11

2.2.6 推出装置校核12

2.2.7 模具外形尺寸校核12

2.3 模架选择12

2.3.1模架类型选择的前提条件12

2.3.2模架系列的选择13

3 浇注系统设计14

3.1 主流道设计14

3.1.1 浇口套设计14

3.1.2 浇口套的固定形式15

3.2 分流道的设计16

3.2.1 分流道的形状及尺寸选择16

3.2.2 分流道的设计16

3.3 浇口设计17

3.3.1 侧浇口的尺寸18

3.4 冷料穴和钩料脱模装置18

3.5 排气系统的设计19

4 成型零件设计20

4.1 型腔模的设计20

4.2 型芯模的设计20

5 推出机构设计23

5.1 推杆推出机构23

5.2 推出机构的复位23

5.3 推出机构的布局24

6 侧向抽芯机构的设计25

6.1 抽芯距的计算25

6.2 抽芯力的计算25

6.3 斜导柱直径的确定26

6.4 斜导柱长度的计算26

6.5 楔紧块的设计27

7 冷却系统设计28

7.1 冷却管道的工艺计算29

7.1.1 冷却管道的直径计算29

7.2 冷却水道的结构设计29

8 导向机构的设计31

8.1 导向机构的设计要点31

8.2 导柱的设计与选择31

8.3 导套的设计与选择32

9 模具装配图32

9.1 模具装配图的绘制32

结论33

谢辞34

参考文献35

附录36

引言

关于模具发展趋势，我认为这主要取决于两个方面，即一方面是模具为之服务的各行各业的发展趋势，另一方面是整个社会和世界科学技术的发展趋势，这实际上就是需要和可能。模具是为制件，也就是成形产品服务的，因此模具必然要以制件(成形产品) 的发展趋势为自己的发展趋势，模具必须满足他们的要求。制件发展趋势主要是轻巧、精美、快速高效生产、低成本与高质量，每一项都预示了模具发展趋势。现简要分析下：要轻巧就会增加使用塑料及开发新材料，包括各种新型塑料、改性塑料、金属塑料、镁合金、复合材料等等，这就要求有新的成形工艺。要精美，就要求外形美观大方，内部无缺陷，这就要求有精细、精密和高质量模具与之相适应。目前我们在精细化方面差距很大，精细化往往被忽视，功亏一篑。快速高效生产，这一方面是要求模具企业要尽量缩短模具生产周期，尽快向模具用户交付模具，另一方面更重要的是要使用户能用你提供的模具来快速高效地生产制品。例如一模多腔多件生产、叠层模具、利用好热流道技术来缩短成形时间以及使用多层复合技术、模内装饰技术、高光无痕注塑技术、在线检测技术、多工序复合技术、多排多工位技术等等。同时制件成形过程智能化还要求有智能化的模具来适应。低成本，这既要通过模具生产的设计、加工、装配来实现模具的低成本制造和低成本供应，更重要的是要使模具用户能使用模具来实现低成本生产。这就对模具提出了更高的要求。模具生产企业必须做到先使模具用户赚钱，然后才能使自己赚钱。在要求低成本的过程中，无论是模具生产企业还是使用模具的企业，不断改善管理，逐步实现信息化管理都是企业的共同要求及进步和发展的方向。高质量，要做到制品的高质量，首先必须是模具的高质量，模具的稳定性一定要好，保证。制品的一致性也要好，而且还要保证寿命。高质量模具与技术休戚相关除上述各点外，许多新领域、新兴产业、新制件和个性化要求也都会对模具不断提出新要求。所以发展。趋势的本身也是在不断发展的从科技发展趋势来看模具发展趋势可以先从下列最基本的六个方面进行分析：

新材料→模具新材料及为成形产品新材料成形的新型模具

新工艺→新的成形工艺及模具加工的新工艺

新技术→技术进步带动模具生产逐步向超高速、超精和高度自动化方向发展

信息化→数字化生产、信息化管理、充分利用IT技术

网络化→溶入和利用好世界全球化网络

循环经济与绿色制造一用尽量少的资源来创造尽量多的价值，包括回收再利用与环保等，不但模具要能这样，而且更要使模具用户也能这样。

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内容简介：: 毕业设计（论文）中期检查表（指导教师）指导教师姓名：郭中玲填表日期： 2014年 4 月 20 日学生学号1000110109学生姓名容道乐题目名称旅行箱拖手塑料套及注射具设计已完成内容开题并做调研，进行翻译；确定其方案设计；完成结构设计；绘制结构草图；完成相关计算；完成英文翻译；绘制装配图；绘制零件图；撰写论文；完成毕业设计。检查日期：2014-4-20完成情况全部完成按进度完成滞后进度安排存在困难解决办法查阅相关资料，并且与指导老师和同学们一起讨论解决方案。预期成绩优秀良好中等及格不及格建议教师签名：教务处实践教学科制表说明：1、本表由检查毕业设计的指导教师如实填写；2、此表要放入毕业设计（论文）档案袋中；3、各院(系)分类汇总后报教务处实践教学科备案编号：毕业设计(论文)任务书题目：旅行箱拖手塑料套及注射模具设计学院：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师题目类型：理论研究实验研究工程设计工程技术研究软件开发 2013年12月9日一、毕业设计（论文）的内容1、塑件的分析；2、塑件材料的选用与性能分析（特性及成型工艺参数）；3、拟定模具的结构形式（型腔的数目及排布）；4、浇注系统的设计；5、分流道的设计； 6、浇口的设计；7、冷料穴和拉料杆的设计；8、成型零件的设计；9、导向机构的设计；10、脱模推出机构的设计；11、侧向分型与抽心机构设计；12、排气系统的设计；13、温度调节系统的设计；14、限位钉设计。二、毕业设计（论文）的要求与数据1、外型尺寸及配合精度必须标注；2、使用环境-1040；3、电气性能符合GB标准；4、外观要求美观坚固；5、根据实际情况确定脱模斜度；6、ABS主要技术指标及工艺参数；7、设计中的计算；8、安装尺寸的校核。三、毕业设计（论文）应完成的工作1、完成二万字左右的毕业设计说明书（论文）；在毕业设计说明书（论文）中必须包括详细的300-500个单词的英文摘要；2、独立完成与课题相关，不少于四万字符的指定英文资料翻译（附英文原文）；3、对于纯机械类课题，绘图工作量折合A0图纸3张以上，其中必须包含两张A3以上的计算机绘图图纸。四、应收集的资料及主要参考文献1 李学峰.塑料模设计及制造M.北京：机械工业出版社，2001.1-2832 翁其金.塑料模塑成型技术M.北京：机械工业出版社，2002.1-164.3 钱泉森.塑料成型工艺及模具设计M.济南：山东科学技术出版社，2004.1-3144 塑料模设计手册编著组.塑料设计手册.北京：机械工业出版社，20025 陈剑鹤.模具设计基础M.北京：机械工业出版社，2004.1-2876 王文广等.塑料注塑模具设计技巧与实例M.北京：化学工业出版社，2004.1-1647 章飞.型腔模具设计与制造M.北京：化学工业出版社，20038 谭雪松，林晓新，温利编.新编塑料模设计手册.北京：人民邮电出版社，2007.19 朱光.塑料注塑模中小型模架及其技术条件M.北京：清华大学出版社，2003.110 Herbertw.Yankeemanu facturing processes Prentice-Hall,Inc.2006五、试验、测试、试制加工所需主要仪器设备及条件计算机(autoCAD,及pro/E,protel软件),任务下达时间：2013年12月9日毕业设计开始与完成时间：2013年12月17日至 2014年05 月8日组织实施单位：教研室主任意见：签字： 2013年12月14日院领导小组意见：签字： 2013 年12月16日编号：毕业设计(论文)开题报告题目：旅行箱拖手塑料套及注射模具设计院（系）：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师题目类型：理论研究实验研究工程设计工程技术研究软件开发 2013年12月23日编号：毕业设计(论文)任务书题目：旅行箱拖手塑料套及注射模具设计院（系）：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师题目类型：理论研究实验研究工程设计工程技术研究软件开发 2014年12月9日编号：毕业设计(论文)说明书题目：旅行箱拖手塑料套及注射模具设计院（系）：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师题目类型：理论研究实验研究工程设计工程技术研究软件开发2014年5月4日编号：毕业设计(论文)外文翻译（原文）院（系）：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师 2014年1月14日编号：毕业设计(论文)外文翻译（译文）院（系）：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师 2014年1月14日编号：毕业设计(论文)开题报告题目：旅行箱拖手塑料套及注射模具设计院（系）：国防生学院专业：机械设计制造及其自动化学生姓名：容道乐学号： 1000110109 指导教师单位：机电工程学院姓名：郭中玲职称：高级工程师题目类型：理论研究实验研究工程设计工程技术研究软件开发 2013年12月23日开题报告填写要求1开题报告作为毕业设计（论文）答辩委员会对学生答辩资格审查的依据材料之一。此报告应在指导教师指导下，由学生在毕业设计（论文）工作前期内完成，经指导教师签署意见审查后生效。 2开题报告内容必须用黑墨水笔工整书写，或按教务处统一设计的电子文档标准格式打印，禁止打印在其它纸上后剪贴，完成后应及时交给指导教师签署意见。3学生查阅资料的参考文献应在5篇及以上（不包括辞典、手册），开题报告的字数要在1000字以上。4有关年月日等日期的填写，应当按照国标GB/T 740894数据元和交换格式、信息交换、日期和时间表示法规定的要求，一律用阿拉伯数字书写。如“2004年4月26日”或“2004-04-26”。1.本课题的研究内容、重点及难点本次毕业设计课题为旅行箱拖手塑料套及注射模设计。近年来，我国模具工业有了很大的发展，模具与生活越来越贴近，给我们的生活带来了很打的方便。在未来的模具市场中，塑料模具发展的速度将高于其它模具，在模具行业中的比例将逐步提高。拖手塑料套广泛运用于旅行箱中，随着人们出行率的增加，旅行箱的需求也随之增多，模具的使用就是降低拖手塑料套的生产成本并提高生产效率。此次设计中有许多地方需要仔细研究，其主要内容如下： 1、查阅资料。结合本次课题查阅相关资料； 2、撰写开题报告； 3、通过对产品的性能分析，完成相关的模具结构与零件设计； 4、设计的模具结构要求完整、合理； 5、合理选择尺寸、公差、表面粗糙度和制件材料，绘制的产品图样完整； 6、认真分析制件图，确定模具型腔、模具结构、分型面和进料口形式，计算含收缩率的相关尺寸和模具的强度和刚度； 7、翻译专业外语文献。 8、撰写毕业设计（论文）说明书； 9、绘制模具装配图和零件图。毕业设计的重点难点： 1、脱模推出机构和侧抽芯机构的设计；2、塑件的结构及工艺分析； 3、材料选择及相关参数的计算； 4、模具型腔数的确定，模具结构、分型面和进料口形式的选择； 5、绘制模具总装图、零件图及尺寸标注。 6、注射模具的设计以及加工工艺设计。2.准备情况（已查阅的参考文献或进行的调研）21世纪，塑料工业以前所谓有的速度高速发展，在各个领域乃至国名经济中已拥有举足轻重的地位。目前，我国塑料工业的高速发展对模具工业提出了越来越高的要求。在2010年，塑料模具在整个模具行业中所占的比例已上升到50%左右，未来几年中，所料模具还将保持高速度发展。模具是工业生产中使用极为广泛的重要装备，采用模具生产制品及零件，具有生产效率高，节约原材料，陈本低廉，保证质量等一系列优点，是现代工业生产中的重要手段和主要发展方向。注塑成型所用的模具即为注塑模（也称为注射模），注塑成型的原理（以螺杆式注射机为例）。首先将颗粒或粉状的塑料加入料斗，然后输送到侧装有电加热的料筒中塑化。螺杆在料筒前端原地转动，使被加热预塑的塑料在螺杆的转动作用下通过螺旋槽输送至料筒前端的喷嘴附近。螺杆的转动使塑料进一步化，料温在剪切摩擦热的作用下进一步提高并得以均匀化。当料筒前端堆积的体对螺杆产生一定的压力时（称为螺杆的背压），螺杆将转动后退，直至整好的行程开关接触，从而使螺母与螺杆锁紧。具有模具一次注射量的塑料预塑和储过程结束。这时，马达带动气缸前进，与液压缸活塞相连接的螺杆以一定的速度和压力将熔料通过料筒前端的喷嘴注入温度较低的闭合模具型腔中。熔体通过喷嘴注入闭合模具腔后，必须经过一定时间的保压，熔融塑料才能冷却固化，保持模具型腔所赋予形状和尺寸。当合模机构打开时，在推出机构的作用下，即可顶出注塑成型的塑料制品。参考查阅的文献资料 1 李学峰.塑料模设计及制造M.北京：机械工业出版社，2001.1-283 2 翁其金.塑料模塑成型技术M.北京：机械工业出版社，2002.1-164. 3 钱泉森.塑料成型工艺及模具设计M.济南：山东科学技术出版社，2004.1-314 4 塑料模设计手册编著组.塑料设计手册.北京：机械工业出版社，2002 5 陈剑鹤.模具设计基础M.北京：机械工业出版社，2004.1-287 6 王文广等.塑料注塑模具设计技巧与实例M.北京：化学工业出版社，2004.1-164 7 章飞.型腔模具设计与制造M.北京：化学工业出版社，2003 8 谭雪松，林晓新，温利编.新编塑料模设计手册.北京：人民邮电出版社，2007.1 9 朱光.塑料注塑模中小型模架及其技术条件M.北京：清华大学出版社，2003.1 10 Herbertw.Yankeemanu facturing processes Prentice-Hall,Inc.20063.实施方案、进度实施计划及预期提交的毕业设计资料1、2013年12月17日至2013年12月30日，理解消化毕设任务书要求并收集、分析、消化资料文献，根据毕设内容完成并交开题报告；2、2013年1月6日至2014年1月13日，开展调研，了解塑件结构，对原材料进行分析，考虑塑件的成型工艺性、模具的总体结构的形式，并完成部分英文摘要翻译。3、2014年3月4日至2013年3月31日，查阅资料，熟悉注射模的结构及有关计算，拟定模具的方案设计、总体设计及主要零件设计，拟定成型工艺过程，查阅有关手册确定适宜的工艺参数，注射机的选择及确定注射设备及型号规格；4、2014年4月1日至2014年4月21日，完成设计计算任务，总体结构的设计和完成总装配图及零件图的设计；5、2014年4月22日至2014年4月30日，完成设计，图纸绘制任务，工艺规程说明书的编写；6、2014年5月1日至2014年5月4日，完善设计并完成论文的撰写；7、 2014年5月4日至2014年5月7日，修改并打印毕业论文及整理相关资料，交指导老师评阅，准备论文答辩。指导教师意见指导教师：年月日开题小组意见开题小组成员签字：年月日院系审核意见院系主管领导签字：年月日2014年机电工程学院毕业设计(论文)进度计划表学生姓名：容道乐学号：1000110109序号起止日期计划完成内容实际完成内容检查日期检查人签名12013.12.912.15任务下达书已完成22013.12.1612.22查阅资料已完成32013.12.2312.29调研已完成42013.12.30-2014.1.5写开题报告已完成52014.1.6-2014.1.12写外文原文及翻译已完成62014.1.13-2014.1.19写外文原文及翻译已完成72014.2.24-2014.3.2写论文说明书已完成82014.3.3-2014.3.9完成框图设计已完成(本表同时作为指导教师对学生的16次考勤记录)2014年机电工程学院毕业设计进度计划表（续）学生姓名：学号：序号起止日期计划完成内容实际完成内容检查日期检查人签名92014.3.10-2014.3.16完成图纸设计已完成102014.3.17-2014.3.23完成说明书初稿已完成112014.3.24-2014.3.30交老师检查已完成122014.3.31-2014.4.6第一次回作者修改已完成132014.4.7-2014.4.13第二次交老师检查已完成142014.4.14-2014.4.20第二次回作者修改已完成152014.4.21-2014.4.27打印修改已完成162014.4.28-2014.5.4完成毕业设计，提交论文已完成任务下达时间：2013年12月9日(本表同时作为指导教师对学生的16次考勤记录)282 Design Results IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT, VOL. 36, NO. 4, NOVEMBER 1989 Work in Change: Social Conditions and of CAD Use in Mechanical Engineering FRED MANSKE AND HARALD WOLF Abstract-The findings presented on the employment of CAD in West Germanys mechanical engineering industry show that CAD is used in various ways by different firms and, thus, also has diverse results on working conditions. The various production structures used by the single- piece, half-standardized, and standardized series producers are consid- ered to be the most important factors for explaining this circumstance. In addition, however, the influence of various interest groups in the firms concerning the introduction process also has to be stressed. In view of their research findings, the authors argue against using the oversimplifications and rash generalizations regarding the reduction of personnel, Taylorism, and deskilling that dominated the discussion during the early days of CAD. They regard the changes taking place at the level of the “microstructures” of designing to be basically the general consequences of the employment of CAD. These changes have until the present had little influence on the division of labor and the development of skills. The latter depend, according to the findings presented in this paper, on the various concepts of CAD utilization. Among other things, the following trends were discovered in this respect: within the field of design, skilled jobs retain their skill level; some already deskilled jobs disappear; the traditional three-way task split into design, detail design, and draftsmen is developing towards a two-way split into design and draftsmen; in addition, new jobs are being created for CAD experts in the fields of CAD development and support; stress is becoming a more important issue for the technicians; traditional, internal career ladders are losing ground; computerized monitoring and control threaten to introduce new ways of binding the design personnel into the design process. I. INVESTIGATING CAD IMPLEMENTATION IN WEST GERMANYS MECHANICAL ENGINEERING INDUSTRY ECHANICAL engineering is one of the most important M branches of West German industry, with about one million employees and an export surplus of some DM 50 or 60 billion annually. It has been able to achieve its internationally recognized leading position above all because it does not manufacture standardized mass products but is rather con- cerned with the specific wishes of clients looking for tailor- made, problem-solving answers. As a consequence of this specialization, small and medium-size firms producing single products or small batches predominate in West Germanys Manuscript received September 9, 1988; revised March 14, 1989. The review of this paper was processed by A. Majchrzak and H. Salzman. This paper contains interim findings from the research project “Requirements of and the Approach to Humane Work Organization in Computer-Aided Design and Planning Processes,” financed by BMFT and supervised by “Projekttra- ger Fertigungstechnik” at the Nuclear Research Centre, Karlsruhe, West Germany. It is currently being carried out at SOFI, Gottingen, West Germany. The authors are with SOFI, 3400 Gottingen, West Germany. IEEE Log number 8929661. mechanical engineering industry. As can been seen in Table I, the significance of small firms in West Germanys mechanical engineering industry has increased. It is clear that design and planning activities are especially important in this form of production, which has to implement production innovations and variations at frequent intervals. This is demonstrated by the fact that some 10-30 percent of the employees work in the designing and operations planning departments in the mechanical engineering firms we have been investigating. The findings of two representative surveys on employment structures in West Germanys mechanical engineering indus- try are presented in Table I1 (the findings from the most recent survey, made in 1988, are unfortunately not available yet). The most significant finding is that the fields “product development and design” and quotation processing and project planning have also gained in importance quantita- tively: in 1976, 10.5 percent of those employed in mechanical engineering worked in these areas (I. 1 and 1.2 in Table 11), in 1984, the percentage increased to 12.3 percent. The percentages given here are averages. In our investiga- tion, the percentages referring to the employees in these job areas are spread out between 5 and 30 percent. In the case of the series producers, the percentage is lower (as low as 5 percent) and in the case of the single-piece producers, it is higher (as high as 30 percent). For more information on the types of producers, see Section 11. For several years now, a broad spectrum of techniques has been available in the shape of CAD, PPS, CAP, and NC programming systems that offer the mechanical engineering industry possibilities to rationalize design and planning activi- ties. It even seems as if it would be possible to technically integrate the various task functions in the field of design and, even further, to fuse it with work planning and NC program- ming, a fusion that in the end would include CNC machines and from which significant effects for and on rationalization and flexibility can be expected. However, it should be mentioned that the technical integra- tion in the majority of the firms is not very advanced: heterogeneous computer and system landscapes still dominate the picture. The employment of CAD itself in mechanical engineering is still not self-evident. This is in contrast to the case of the industries that can be considered advanced in this sense, such as automobile and airplane construction, where it has been, in the meantime, a proof of technical perfection if certain products are more or less completely developed using CAD (cf., e.g., l). According to a recent survey made in 1986 2, 0018-9391/89/1 100-0282$01 .OO 0 1989 IEEE Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. MANSKE AND WOLF: DESIGN WORK IN CHANGE 1972 1981 Number Em- Turn- Number Em Turn- Firms ees % of ploy- over of ploy- over Firms ees % % % Small Firms (20 to 199 Em- 3603 22.2 19.6 ployees ) 4026 25.3 21.2 283 1986 Number Em- Turn- Firms ees % % of ploy- over 4114 26.4 23.5 TABLE I FIRMS, EMPLOYEES, AND TURNOVER IN MECHANICAL ENGINEERING ACCORDING TO SIZE Large Firms Employees) (500 or More 470 56.4 59.3 448 54.5 59.6 433 53.5 58.5 _ _ _ _ I. Design and Planning 14.2 Activities (1+2+3) - Sum I 48111) 98.11) 98.9l) I 5193 100 100 1 5260 100 100 In 1972, firms with lo to 19 employees were surveyed. the figure in order to be able to compare the findings from 1972 with those of They were not included in 16.0 1986. The absolute number of employees was: 1972, 1,163 million; 1980, 1,099 million; 1986, 1,085 million. The turnover percentages refer to the month of September of each year. 3. Operations Planning 11. Other Activities 4. Material Control and (4t5t6t7) Management 5. Production and Assembly 6. Administration 7. Sales Department I. t 11. Source: VDMA, Statistisches Jahrbuch fur den Maschinenbau: 1975, 1983 and 1988. 3.7 3.7 71.4 74.9 4.7 4.8 54.8 52.2 9.3 8.6 8.6 9.3 91.6 90.9 TABLE II DEVELOPMENT OF THE EMPLOYEES IN MECHANICAL ENGINEERING ACCORDING TO JOB ACTIVITY (PERCENTAGE OF TOTAL EMPLOYEES) Total I I 1976 I 1984 100.0 100.0 I 1. Product Development and Design I 8.67 I 9 . 7 ) 2. Quotation Processing, Project Planning I 111. Vocational Training I I 8. Trainer 9. Trainee 0.5 0.5 I 7.9 I 8.6 Source: VDMA, Abteilung Betriebswirtschaft und Informatik; Statistisches Handbuch far den Maschinenbau 1981 and BWZ 50. Sept. 1985. Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. 284 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT, VOL. 36, NO. 4, NOVEMBER 1989 p. 91, over 80 percent of the mechanical engineering firms still did not employ CAD. The minority, comprising about 18 percent, that utilized CAD at the time used it at a completely different level. Many are still involved in an introductory phase. In most of the mechanical engineering firms, the dominating situation is, in all probability, that one would find a few CAD workplaces confronted by many “conventional” workplaces. Our research project has, in the face of this situation, to study, above all, the following questions: *What are the task structures in the design and planning departments of West Germanys mechanical engineering industry? *Which qualifications and skills are required of the employ- ees as a result of the task functions and their organizational bundling so that they form jobs? *Which forms of cooperation can be found in the technical offices? What chances and paths are there for advance- ment? And naturally, it was necessary to study what changes take place in these structures as a result of the implementation of new techniques. The introduction of these new techniques in mechanical engineering represents a process that generally takes several years. The character of the process corresponded to our research procedure: the surveys were conceptualized as longitudinal studies. The introductory processes were to be observed over a period of three to four years. The firms included in the survey were chosen on the basis of a preliminary test. The targets were on the one hand, to choose firms that produced different products; then again, they should be of different sizes (number of employees); finally, we also wanted to find firms that were a bit further advanced in the implementation process. When choosing the firms, we were able to draw on two previous studies we had done on the employment of produc- tion planning and control systems (PPS) that were carried out from 1981 to 1985 3, 4. Our knowledge of West Germanys mechanical engineering industry was in other words, already quite comprehensive. In the end, we chose ten firms: three machine-tool builders, as well as one manufac- turer each of printing machines, bookbinding machines, escalators, screen-printing machines, machines and systems for shaping steel, road construction machines, and supplies of the electrotechnical industry. The smallest firm included in the survey employed 60 people, the largest over 2000. Firms with more than 500 employees are clearly overrepresented. This is a result of the fact that the employment of the new technology is already more widely spread in these firms (cf. 2). The survey was carried out in the firms in three phases. The first phase involved preliminary investigations. This was followed, about four months later, by intensive surveys (approximately two weeks per firm). Finally, after approxi- mately one more year, there were intensive surveys (approxi- mately one week per firm). Expert talks were held with everyone from the heads of the firms to the heads of the de- partments (approximately two hours in length; a total of 129 talks) and intensive on-site job investigations that consisted of observations and talks (approximately four to eight hours in length; a total of 67 investigations). Included in the on-site job investigations were designers (36); technical draftmen, male and female (12); operation planners (7); and NC programmers (12). All in all, it is a qualitative study. The findings, therefore, do not allow any generalized conclusions. On the basis of our comprehensive knowledge, however, it is possible to make qualitative statements on trends. In this paper, we will concentrate on that part of the survey that dealt with CAD and design. This is possible from the viewpoint of the contents because, according to our investiga- tions, even in the case of ties between CAD and NC programming systems the tasks in design and work planning remain clearly separated. On the other hand, it is impossible to present both subjects thoroughly as a paper is too short to be able to handle both properly - CAD and design, CAD + NC programming and work planning. Furthermore, we abstract from the problems of product complexity to a large extent. The presentation focuses on those factors that, from our point of view, most significantly determine the various areas and forms of employing CAD and the consequences of the CAD employment for designers, detail designers, and techni- cal draftsmen. II. TRADITIONAL FORMS OF DESIGN IN MECHANICAL ENGINEERING A. Types of Production and Design The individual companies can deal with the situation within the branch as described above in various ways. This also has its effects on the importance and form for the design process. One can differentiate three types of production: a) single-piece production, b) half-standardized production with custom-made variations, and c) standardized production in fairly large series. As a rule, firms belonging to category a) manufacture products tailored to the specific demands of the customer. Consequently, each special order requires a high expenditure of design work to be completed within the narrow time limits dictated by the delivery date. In contrast, the producer of series c) manufactures “ready-made” items and has a larger number of his standard products in stock. In this connection, product design does not depend on the individual client. Accordingly, it is detached from the actual production process as far as its time requirements are concerned. Firms belonging to category b) combine characteristics of both the single-piece producer and the series producer. The differences, which are only briefly mentioned here, in the design process in the firms have until now played an important role in the development of the different concepts of CAD employment which will have to be discussed further on in this paper. Among the firms included in our study sample are series producers that manufacture between 1000 and 2000 machines per year. The total production covers various types of machines that are offered by the firms. One enterprise, for example, offers eight different types of machines: manual “universal” milling and drilling machines, small CNC milling and drilling machines, Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. MANSKE AND WOLF: DESIGN WORK IN CHANGE 285 large CNC milling and drilling machines, machining centers, high-production machining centers, flexible manufacturing systems, engraving and duplicating milling machines, tool-grinding machines. A series produced at any one time can amount to as many as approximately 100 machines. Usually, however, the total is lower. The single-piece a) and half-standardized b) producers manufacture a total of between 40 to 150 machines per year. The products are always single units. B. “Product Experience” and Team work in Traditional Design Offices The typology of work in design offices is relatively diverse and is divided among development and calculation engineers, draft designers, detail designers, and draftsmen. Very few graduate engineers have until the present been employed in these jobs in West Germany. The typical trend has been, instead, to choose people - even for the most demanding positions within the job hierarchy-on the basis of long experience and skills gained on the job. These employees were often skilled workers who worked their way up. In most firms, the technician or draftsman is expected to gain higher qualifications during the course of his time spent on the job. It would, therefore, be inappropriate to conclude on the basis of a brief glance at the relatively refined task structures that there are very permanent and solid lines demarcating the division of labor in design departments. The transitions are, on the contrary, “soft” and flowing and promote the necessary flexibility. In addition to product and component specialization and subdivision within the departments, this flexibility is often characterized by a “task force” organization during which various specialists (designers, detail designers, draftsmen) cooperate for a fixed period of time on a particular task required by a specific order. Such varying forms of coopera- tion, which frequently change and offer diverse ways of approaching a problem, present an opportunity to work with sundry aspects of the object and, thereby, offer the chance to accumulate knowledge closely related to different products and tasks. The great significance of this “knowledge gained through experience” in the company is a result of the fact that the design process in principle normally uses, although it may take on a number of variations, familiar solutions specific to the particular firm and the particular product. So far this has hardly required any advanced theoretical or academic skills which could be acquired outside the process itself. This is also the reason for the “permeability” of the work structures which makes it easier to make “careers” on the basis of advancement within the firm. Essentially there are two factors which, today, have made these working conditions (which had remained stable for a long time) an important, new area of rationalization in the engineering firms. One factor is connected with the necessity of adapting to the changed utilization conditions and of integrating new, in particular, microelectronic-based, technol- ogies in the products and production processes. Now ever more complex machines must be more rapidly developed, designed, and produced. As a result, there was an increase in the old requirements, and in addition, new requirements were added, particularly in those departments that plan and prepare the production, such as the design department. At first, it seems, the firms were only able to meet these conditions by hiring additional staff and employing better qualified employ- ees in these areas. This constellation results in the firms needing a whole new package of rationalization measures. The classical goals of rationalization, such as reducing personnel costs and speeding up the work process, receive an importance hardly known before in the sectors employing technical personnel. The second factor we spoke of relates to the means of rationalization themselves, which are available in improved and gradually adjusting quality and dropping in the price of hardware. They are, thus, more economically feasible. Last but not least, it should be mentioned that the government of the Federal Republic of Germany has made large amounts of money available to mechanical engineering firms in recent years in order to speed up the diffusion of CAD technology, particularly in small and medium-sized firms. From 1984 to 1987, these firms received as subsidies up to 40 percent of the costs involved in the introduction of CAD. III. CONCEPTS ON THE EMPLOYMENT OF CAD AND THEIR “LOGIC” FROM THE PERSPECTIVE OF THE FIRMS The first important result of the survey on the present types of employment of CAD that were discovered during the investigation is the fact that the firms develop and utilize various concepts of the usage and arrangements that have to be met respecting the organizational integration of CAD in existing structures. Three brief case descriptions should make this clear. We have not chosen the firms to be used as examples randomly, but rather have selected those that afford insight into typical introduction constellations and employment strategies. Firm A is a firm which designs and manufactures machine systems for steel mills. It has 2000 employees and can, according to our experience, be considered a typical represent- ative of the current mainstream found in the West German machine construction industry that can be used to illustrate the way CAD is introduced and used and the consequences for work arising from the new technologies. CAD was first introduced just four years ago, and the still relatively limited capacities are being only hesitatingly enlarged. CAD is mainly employed to make drawings for the workshop, and the majority of those working with CAD are draftsmen. The CAD workstations are used by several employees for whom the work with CAD makes up only part of their overall jobs, i.e., they continue to also carry out tasks “conventionally” on the drawing board. We will refer to this mixture of tasks and work from now on as hybrid work. The operating times are divided among the various users according to a schedule. The users utilize CAD to solve their “own” tasks, i.e., as a rule those Of the total DM 610 million granted by the Bundesminister fiir Forschung und Technologies “Programm Fertigungstechnik” in the years 1984 to 1987, DM 369 million alone were granted for the “indirect, specific” support of the development and introduction of CAD/CAM systems in the firms. Subsidies were given to 1285 projects in this area 151. Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. 286 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT, VOL. 36, NO. 4, NOVEMBER 1989 tasks which have been assigned to them in the design team to which they continue to belong. In Firm B, an affiliate of a general mechanical engineering enterprise with approximately 500 employees, the utilization of CAD is likewise not very developed. In this case, however, according to the managements plans, the goal from the very beginning was to integrate the computer into the total system of production and filling of orders. CAD is understood and conceived as a constituent of this system. The employment of CAD in this case does not begin in the area of routine technical drawing, but rather commences from “above” and is used to solve the more difficult problems of conception and design. Accordingly, the engineers are among the first users. In this case we also find a mixture of various tasks and types of work, and the few available workstations are used by different members of the staff. Firm C manufactures machines used to process synthetic materials. It has approximately 800 employees and has in just a few years furnished its design sector extensively with computers. There are no more drawing boards in the design department. The CAD display screens constitute the central work element for all of the designers and technical draftsmen. Traditional forms of the division of labor and cooperation (teamwork) still exist, but they exist on the basis of the new technology. The three case descriptions verify how different the strategies of use and the resulting forms of organization and work in engineering firms can be. Firm A represents, as stated above, the currently dominant constellation found in the firms we investigated. The essential characteristics of the way CAD is employed in this “mainstream” firm are that CAD is primarily employed as an aid in working out plans for production facilities; as a rule, draftsmen are engaged at the CAD workstations; there is a work schedule for the CAD workstations since these are to be used by several persons and should be used continually and for as long as possible. Thus the traditional organization structures in the design office are retained (first and foremost, teamwork). A variation of this concept that, admittedly, is only relatively seldom met with is the total organizational segregation of a group of CAD users who carry out tasks for other design sectors (“service team”). A doubtless decisive and important argument, from a firm policy standpoint, for the legitimization of this concept of use is the assumption on the part of the management - and above all in the eyes of the superiors in the design department - that an employment of CAD which in the beginning is limited to working out preconceived solutions would lead most likely to rationalization effects and allow continual utilization of the expensive system. In addition, we have to consider the circumstance that firm A - which is also in this sense typical of large areas of the West German engineering sector - is a single-piece producer and, accordingly, the designing takes place essentially simultaneously with the process. As it is, thus, in any case functional element of the fabrication of each single product, the total lead time of the single products depends to a large extent on the time necessary for its designing. Shortening the lead time, which is an important rationalization target, in order to beat the competition on the relevant terrain of readiness to deliver, ” seems likewise to be most easily attainable through a speeding up of the so-called routine functions. However, these varieties in concept do not coalesce into rigid forms of organization where future technological and organizational development must take place within set barri- ers. In fact, it is possible to observe “learning processes” in some of the firms. For example, the borderline marking a type of utilization of CAD is sometimes, so to speak, spontaneously crossed by some “courageous users in everyday practices. This is, first and foremost, made possible by the relatively free access to the computers by various operators solving various problems from various fields, i.e., hybrid work forms. There are also examples of an organizational development of the concept variant “service team” to that of “hybrid work forms.” The former (service team) is sometimes even used consciously as a transitional solution during the introductory phase of CAD. In the case of B and C, which both produce series, other technological and economic frameworks are significant for the design work. This particular design work can sooner be characterized as development work which is done for a specific production program. This work normally takes place before the product is produced and is principally finished before the program is mature. In this case rationalization in design departments is, to a much smaller extent than in the case of single-piece production, a contribution to the reduction in lead times. It appears as though this leads to a greater ”degree of freedom” during the establishment of fields of application and organizational forms of computer use in the preparation for production. This is expressed, above all, by the fact that the use of CAD, should it not have its starting point here, will be very quickly developed in the core areas of the “actual” design work- the design to scale of the product, even if this manner of proceeding at first seems to hold greater uncertainties than the pure “drawing solution.” Even in product development functions - so to speak “above” the design to scale -there is sporadic use of CAD in the cases of B and C (see Fig. 1). The continual use of CAD systems to capacity is also not placed in the foreground as strongly by department heads and organizers as in the other firms. Such organizational leeway in the structuring naturally depends a great deal on the general economic situation and capacity of the firm. Aside from the fact that such forms of CAD employment are usually found in series production, it is typical that in such firms the data-processing department has a strong position and decisively influences the introduction of CAD. The particular tenacity and dynamics of the introductory process are also partly explained by this. In addition, the plan from the very beginning to try to overlap and tie the departments together on the basis of data technology can ultimately be traced back to the powerful position of the data-processing departments within the firms. In Fig. 1 the CAD implementation concepts are summa- rized. Besides the areas in which CAD is directly employed in order to solve designing problems - the areas that the techno- Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. MANSKE AND WOLF: DESIGN WORK IN CHANGE CASE A CAD Island in the Drafting Area J r Starting CAD Implementation at the bottom” 287 CASE 0 CAD Islands in the Design and Drafting Areas or Starting CAD Implementation from above (too) Product Development Development Design Detail Design I Drafting Sporadlc Use of CAD t I I I I CASE C CAD penetrating the Design and )rafting Areas . “Technical itegration of Design and Drafting Sporadic Use ot CAD Explanation: ilnt 1 I now in r.kchanlc-ii n c j n e . r n q t : r i , ;ii ri 1 1 1 7 I ) , q, o r i s . ) n t h e Process ot Product Development. Fig. 1. CAD implementation concepts in mechanical engineering. logical and organizational structuring of the above-described usage concepts are based upon - additional, new tasks arise as a result of the introduction of CAD. CAD systems are, indeed, usually bought as standard systems, but getting them to “work” effectively is relatively complicated. It requires, first and foremost, the creation of data banks; an appropriate systematization of the design procedure; the choice, care, and constant adapting and updating of hardware and software for the firm specifically; and, last but not least, training employ- ees to use the systems. Some of the new functions that will have to be carried out for an “indefinite” period of time are delegated to people working in existing departments in the firm (above all, the data-processing department). However, there always remains a central core of tasks that demand new, specific knowledge, and the firms assign these tasks to a new group of employees who do not employ CAD themselves but rather must see to it that it is used efficiently: the CAD experts. These are mainly recruited from outside the firm and frequently as a direct consequence of the introduction of CAD. Usually they are young graduates from technical colleges and universities who have, as a rule, studied mechanical engineering. They also have additional qualifications in the area of computer science and knowledge of the CAD programs and other computer systems available on the market at the time. On the other hand, only rarely have they had any experience in designing departments. IV. INTERESTS AND OPTIONS OF THE EMPLOYEES We touched above briefly on another important determining factor that affects the technological and organizational struc- tures: the interests and options of the employees in the firms. On the management side, the question as to the direction and dynamics of CAD utilization seems to be the most important in determining whether the sectorial middle management (heads of the designing departments) or the data-processing special- ists get their own way or go together with the top management and are, thus, able to strongly influence the establishment of the utilization concepts. For many chief designers-and it is they who play the decisive role in the introductory process - rationalization of the “routine jobs” and the creation of working drawings are clearly the first things that influence their motives when introducing CAD. They frequently consider drafting and planning to be the central, “creative” work process for which at first it does not seem to be possible to efficiently and directly employ technology. Their career backgrounds - usually they are engineers who in the past worked themselves in the design department - causes them to demonstrate solidarity with the more highly qualified employees who have similar opinions. The new technical possibilities should help make the drawing of the mechanical drawings more efficient and faster; at the same time, the “routine jobs” should be more clearly separated from the tasks carried out by the design engineers so that they can better develop their innovative potential. Such behavior-determining viewpoints obviously support one or the other variations of the presented “mainstream” models when the organization is determined. This is at first hardly affected by the sometimes nearly contrary opinions of the CAD experts in the firms who gain their position during the introductory phase, as we have seen above. They do indeed often mention the opinion that the new technology is an exacting aid for the work of highly qualified users (designers1 Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. 288 IEEE TRANSACTIONS ON ENGINEEFUNG MANAGEMENT, VOL. 36, NO. 4, NOVEMBER 1989 engineers) that can only be used really efficiently by them, i.e., utilizing the full technical potential. But their precarious position in the firms as externally recruited experts, who are frequently recruited directly in connection with the introduc- tion of CAD, means that they have no great influence on the firms policy in the beginning unless they receive the necessary support. This forces them to take a pragmatic attitude and stick closely to the firms instructions. The situation is different, as already indicated, if one-as was indeed atypical in the case of the small and medium-sized mechanical engineering firms - meets with solidly established data-processing and organization departments that have a strong position in the firms. These departments, it is true, work together closely with the specific technical departments, but their work transcends the specific sectors; thus, they are in a position to plan the data-processing procedures themselves. The CAD expert teams in this case are employed in the data- processing departments; they are not, as in most cases, a small staff established within the production planning sectors. A constellation like this seems from the management standpoint to correlate, on the one hand, more with the early realization of network plans (e.g., CAD/NC integration) and, on the other, with a more determined utilization of leeway in structuring the organization. How do the technicians and their representatives in the firm react to the rationalization process and the concepts of the management? Here we are confronted by an ambivalent situation. On the one hand, at least certain groups are by no means merely “concerned,” but are rather motivating mo- ments in the change themselves. Their help is an important prerequisite in reaching the rationalization goals because the lengthy implementation and development phases of CAD make their participation necessary. Within the framework of these requirements it is indeed possible to represent their own interests. On the other hand, such “uncontrolled codetermina- tion” hardly touches the major lines of the management planning and remains restricted to a mere individual interest perspective. In addition, by no means do all groups in the technical offices have the same chances to participate. The workers councils, finally, do not seem at the moment to have established an adequate course for their policy when representing the problems of the technicians. Their activities are, with few exceptions, characterized by an uncertain and mainly wary attitude towards the introduction of CAD. The “participation” in the introduction process remains, as a rule, limited to a more or less passive acceptance of information given out by the management about the planned measures. The direct influence of the workers councils on the realization of the employment concepts and the organization of the work thus remains very limited in the case of CAD-as in the occurrence of other forms of technology. V. PERSONNEL CUTS AND DESKILLING? A WARNING AGAINST “SIMPLE” THEORIES The effect of the technological and organizational changes on the professional qualifications of the blue-collar and white- collar employees as well as the amount of endangerment for workplaces and the resulting “rate of dismissal” is tradition- ally the focal point of interest in the debates carried out by the public and industrial sociology. The loss of jobs through technology is now at least conceivable in the case of employees in the designing departments. This is certainly a new situation for technical employees. However, until now in the wake of the introduction of computers in the technical offices only those jobs that where occupied by “marginal” employees - usually women (typists, helpers) were done away with. The actual specialists have been spared until now; even more, the growth of this group has, in some cases, clearly overcompensated the loss of jobs in other sectors of production planning and preparation. In fact, the number of draftsmen - in other words, the professional group most affected by the employment of CAD at the moment - increased slightly once again in the 1980. It is also questionable whether - at least in the near future -jobs will be lost in development and design offices as a result of the employment of technology. On the other hand, as far as the presumable direction the changes in the required qualifications will take in the sector employing technicians as a result of the increasing use of CAD is concerned, relatively clear and oversimplified as- sumptions were made at an early date. If one ignores the opinion of those engineers who are themselves involved and interested in the technical development in question and with hardly an exception have predicted that work in designing offices will become even “more creative” because of being freed of “routine jobs” and thus will result in generally higher qualifications thanks to CAD (cf., e.g., 7, p. 26 ff.), the pessimistic prognoses have definitely outweighed the optimis- tic ones in the wake of the popularity of Bravermanns theory 8 on the “degradation of work.” It was in particular Cooley 9 who soon pointed out the dangers connected with CAD, saying that as a result the technical offices would also be afflicted by Taylorism, which would naturally lead to a drastic deskilling process in the offices. In this case, it was first and foremost the directly affected and politically motivated trade unionist who spoke up and wanted to awaken his audience through his message and move them to take action because of the negative brisance contained in that message. Our discussion to this point should have made it clear enough that firms can employ CAD in very different ways. It is impossible to speak of a uniform development of skills for entire professional groups or even all employees working in design, something not a few observers seem to presume. Instead, the way in which the requirement structures for the individual types of task (designer, detail designer, draftsman) change depends decidedly on the above-described organization concepts existing in the firms and not primarily on the particular characteristics of the new technology. Without a doubt, however, a few general characteristics of CAD technology do exist that directly affect the required skills and give them, at least, new contours. Thus, before we turn to the specific changes in the working conditions of the various occupational groups concerned, we would like to make a few The number of draftsmen in the whole West German metal industry, which along with mechanical engineering includes the automobile and electronic industries, has increased by 2400 from 1980 to 1986. The total number then was 57 800 (of which 27 OOO were women) 6, p. 271. Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. MANSIZE AND WOLF: DESIGN WORK IN CHANGE remarks on the “organizationally neutral” effects of CAD with a view to the skills that are demanded. A number of elementary prerequisites respecting the work behavior of the entire design staff grow out of the fact that the design work is basically “abstract work.” The processing of real objects is not the focal point of the work, but rather the creation and presentation of new products that do not exist materially as of yet, will be produced later, and in the production of which the designers and male and female draftsmen are not directly involved. Nonetheless, however, these products are the dominant subject of their work. Thus, the existing temporal, spatial, and material “gap” between the worker and the object of his work must be “bridged” or reconciled: reconciled in such a way that the worker can cope cognitively with the “gap.” In order to do this, as is well known, special forms have been developed to reconcile this gap; the mental production process in (mechanical) design takes place in the abstract world of engineering draftsmanship with the help of an extensive, analog geometrical presentation of the product. It is these specific forms of “reconciliation” between the worker and the object he is working on that are directly affected by the employment of CAD. To put it briefly, the relationship of the (altered) abstract presentation to the subject of the work (work object) changes when working with CAD, as well as the instrumental execution of this presentation. This has consequences regarding the cognitive demands on the staff. The studies made by Wingert et al. lo and Muggli and Zinkl ll did supply primary findings and incentives on which further analysis can be based. They “translate” the above outlined subject essentially into two concrete ways of posing the problem; the demands on the spatial powers of the imagination and the entire complex of “dealing with the new technology” and the qualifications necessary to do this. Accordingly, there is a great demand on the spatial powers of the CAD users imagination: in the first place because of the smaller picture on the screen in comparison with the much larger drawing on the drawing board and the resulting limited possibilities of grasping the total picture at any given time of the object being designed and, thereby, a precise idea of the proportion. This is true in the case of the currently common two-dimensional CAD systems. Three-dimensional systems, which today still hardly find any productive use in mechanical engineering, will indeed - as Muggli and Zinkl suspect - make the presentation of the product “more graphic”; however, the process of “working on” the product model by means of the computer leads to a drastic change in the conventional methods of working, which likewise implies an increase in the necessary spatial powers of the imagination. Regarding the second problem, the studies to hand have observed a shift from such “manual” skills as are necessary in order to produce a clean, exact technical drawing to the “technical know-how” 289 that is required to operate the system 11, p. 1071. Such a paraphrase remains, however, much too superficial and unclear. With interactive graphic CAD programs, the micro- structure of the design activities changes as Wingert et al. have worked out. Their use means a switch from the relatively unmediated activities at the drawing board and on paper that are directly perceived by and connected with the senses to a state of being “confined” within the command structures of the program system. These “commands” must be “em- ployed” consciously and deliberately; they intervene, as it were, between the intention and result of the activity. The system allows, at the same time, design steps very similar to those carried out before, but now they have to be done differently: by “applying” given commands. Wingert et al. have called this the mediatization of the design work. It is this point that CAD experts, as well as CAD users, refer to when they say that design work has become “more abstract.” VI. CHANGES IN THE DIVISION OF LABOR AND NEW FORMS OF STRESS The dynamics in the areas of work, qualification, and stress structures has, in addition to the new technology, other, even more important sources: the sales and product strategies, as well as the connected variations of different concepts of the use of technology and organization found in the firms. The latter tie the ensuing work functions to particular jobs or types of activities with corresponding skill and load profiles. The general development of the working conditions for the technicians is thus in the end greatly dependent on the firms concepts of use and the resulting specific use of the technical possibilities. The employment of CAD affects the functions of design and drafting. What is meant here is the determination of the dominating characteristics of the object that is to be con- structed; its presentation in the form of a design to scale; and, based on this, the establishment of the details of these elementary characteristics (using, if necessary, once again a detail design to make it more graphic); and, finally, putting together “readable” documents suitable for the needs of the production process (drawings, lists of items) that can serve as information for the final production of the products. The “middle” function of determining the details of the already existing design, in other words the precise and final establish- ment of diverse parameters at a level in which the product is broken down into its various components, will now - accord- ing to our empirical findings-fall largely in the realm of CAD. Tasks that would traditionally take place prior to or following this “middle function” are so restructured that it is hardly possible to build up an independent area of work on the basis of the remaining “rest in-between” these task - that of the detail designer. The widespread three-tiered division of the design staff into designers, detail designers, and draftsmen is thus questioned. The possibilities arising from the employ- The development in electrodesign was quite different. In this case, the subject of the work has always been to show how abstract functions are tied together. This is demonstrated bv means of svmbols (e.g. circuit olans). As a merit of-CAD indicate that the “middle” function, has been carried out by the detail designer until now, could be I result, the switch to CAD should be “easier” to managein some respects in Dassed on to the desiener or draftsman. makine the detail ” ” designer dispensable. this field of design (and should be easier for the empliyees as well).- It is symptomatic that the usual practice found among CAD users is t o have the interim results of their work orinted out as large-scale drawings and Diverging trends become apparent On which Of Y - to use these drawings to support their powers of imagination. the concepts of use described above are found in the surveyed Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. 290 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT, VOL. 36, NO. 4, NOVEMBER 1989 Main Work Places Designer Detail Deslgner Male / Female Draftsmen CASE A “Startlng CAD lmplementatlon at the bottom CASE C “Startlng CAD Implamentauon from above * Detail designing no longer constitutes an independent job. Fig. 2. CAD implementation and its effects on the structure of jobs in the field of design. firm. This can once again be demonstrated on the basis of the chosen examples from among the firms. In firm C, in which the designers already develop their plans and designs directly on the CAD screen, they also in the meantime carry out many of the earlier “detailing functions.” As the new medium has, as it is, on the basis of its more or less standardized geometric elements, a high degree of exactness and precision in its presentation, only a small amount of additional effort on the part of the designer is needed in order to establish the design parameters well enough and exactly enough so that additional detail work in the old sense is hardly necessary anymore. The draftsman is left with the task of “extracting” details for the detail drawings from the draft and supplying them with the information necessary for production. Their new task at the CAD workstation remains, thus, regarded from the viewpoint of extent and type of job that is to be done, quite similar to the earlier “conventional” task. Another development seems to be unfolding in firm A, where CAD was first used, in contrast, to develop production drawings, and this will remain the main focal point for the time being. In this case, therefore, the detailing function is part of the task of developing production drawings. Otherwise it could result in considerable “double work” for the detail designer and CAD draftsman because the latter has in any case to convert the instructions for the detail and compilation drawings into CAD geometry, regardless of how precise his instructions already are. In contrast to firm C, the final draft and detail work are growing together, above all because the development and design stages are still largely ignored when CAD is used. In such a constellation it is still possible, on the one hand, for the draftsmen working with CAD to enlarge the spectrum of their activities and raise them in quality and, on the other hand, for this work to be taken over by the former detail designer, for whom this would signify a kind of demotion. Accordingly, it is possible to formulate the follow- ing hypothesis on the correlations between concepts of CAD use and the resulting task structures: the intermediate design function of detailing is subject to a kind of “magnetic force” when CAD is introduced that can take several directions according to the firms particular concept of use. If CAD is introduced “from above” (design), then the force also works upward and ensures that there will be a relative preservation of the area of work carried out by the draftsman. If, on the other hand, the starting point begins “from below,” which was the case in the majority of the firms we investigated, then the force works in the other direction-in other words, downward towards the development of the drawing and possibly, as a result, the draftmen may have the chance to take over more demanding elements of the work. This discussion is summa- rized in Fig. 2. We have consciously spoken of the emerging trends. At the level in which CAD is generally employed at the moment it is possible to find them; however, they do not cause any drastic and radical changes in the work situation. The individual tasks still have to, in any case, be characterized as forms of skilled work. For this reason, the aspect of qualifications does not dominate in the concerned technicians perception of the changes. For them, rather, the dimension of stress is clearly in the foreground, and that indeed is seen as a clearly negative sign. The dominating way CAD is employed - represented by firm A - is marked by two characteristics: 1) “hybrid work,” i.e., the CAD users continue to also carry out design tasks “conventionally” on the drawing board; and 2) personnel scheduling, i.e., “timetables” for the CAD workstations in order to guarantee their uninterrupted use. This has two important consequences for the users stress burden. On the one hand, it results in frequent situations that require Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. MANSKE AND WOLF: DESIGN WORK IN CHANGE adjustment and getting used to the new work situation in which a high degree of concentration is necessary. On the other hand, the rigid limitation of the time available for use makes relatively precise planning a must and forces the users to carry out the work as fast as possible at the terminal, an aspect that can lead to a general psychological and cognitive overtaxation. In firm C, on the other hand, such moments of stress, induced by the organization of the work, are done away with to a large extent. There is no longer any “hybrid” work and each worker has his “own” screen. Instead, in the foreground we find forms of stress that can be traced back directly to the “medium” employed in the work, CAD itself. CAD seems to have a kind of “magnetic effect” that, irrespective o f the explicit or implicit demands made by the firm on the individual workers regarding their work at the terminal, results just the same in a spontaneous intensification of the work (cf., e.g., 121). The more the work at the CAD workstation takes on the shape of more or less routine work, the more this form of stress becomes oppressive. It is obvious that the circumstance of having ones “own” screen at ones own disposal, if there is no strict control of the rate of utilization, can lead to the employees at least being able to individually regulate and temporarily alleviate to some extent the stress effects resulting from working with CAD. The CAD users working in the firms classified here as including the organizational type “service team” are, in contrast, continually and directly exposed to this type of stress. In addition to the above-mentioned aspects of the working conditions, which differ in their characteristics according to the type of utilization exercised, there are also general aspects in the development of the way the work is organized that are likewise not determined by technology. Thus, there is a tendency in almost all of the firms to take advantage of existing flextime regulations so that they can stealthily introduce shift work at the CAD workstations where it did not exist before. Since, as a rule, there is a consensus among management, workers councils, and CAD users that this capital-intensive equipment should be used as extensively as possible, the firms can usually employ this tactic under the premise of allowing the user to regulate the working hours at his own discretion. This procedure furthers the acceptance of the new regulations governing the working hours and can eventually even be expanded by the firm until an efficient double-shift utilization has been established. Thus, without the firms having to pay the usual bonus for shift work common in the production sector, design work can become shift work - with all the well-known negative health and social effects. Another common characteristic of the variation in the structuring of the organization is, as has already been pointed out, the widely found gap between CAD utilization and CAD development. One has to ask what this type of separation will mean for the work of skilled designers in the long run, especially as the programming is becoming continually more 29 1 development to a certain narrowing of the contents of the designers work. In some of these firms, they are thinking o f improving initial designs, which are used by the single-piece and custom manufacturers to define the product as precisely as possible together with the customer (and his own design), by means of a qualitative strengthening of the employment and integration of CAD so that they would be in a position to really carry out this task prperly. The “actual” designing of the product could then, under certain circumstances, be cut back to the level of specifying the already more or less defined order, defined on the basis of CAD data banks. Although the designers would retain their technical skills, their work will be confined to a segment of those job functions that had until now been characteristic of their broad range of skills. VII. SUMMARY 1) The crucial areas in which qualified patterns of work are found in design are also found to a large extent when CAD is used, at least according to a first, superficial glance. The new tasks that result from the visible changes in the product - independent of whether CAD is employed or not-are combined to form new jobs with relatively high qualification requirements and added to the already existing jobs in the field of design (e.g., “software designer”). Less frequently found types of jobs such as that of the mere drawer and data typist disappear, or clearly lose their quantitative weight. 2) If one looks more closely, there are important shifts in the seemingly preserved crucial area of the qualified jobs. The work of the detail designer loses, as a result of the above- mentioned precision of the design drawings made with the help of CAD, the capability of constituting its own work sector. It is true that the job does not disappear entirely, but it is likely that the remaining functions will be passed on to designers or draftsmen. 3) In addition to the modified, reproduced crucial areas of work in design that are concerned with the product as their subject, there are also additional technical experts whose central task lies in the implementation and continual modifica- tion and further development of the CAD systems. By means of application programs, they could in the future have an indirect influence on the way the designers and draftsmen do their work. Furthermore, there is a tendency to assign standardizing and systematizing tasks to these experts. 4) Recruiting patterns and personnel structures are gradu- ally changing. University graduates (mechanical and electrical engineers) coming from outside the firms, i.e., “intruders,” are given good positions and are gaining importance both in new areas in design and among the staff of CAD experts. On the other hand, it would appear as if the traditional design career ladders are losing their significance. There is an increasing development of new fields of work which the “empiricists” in the firms cannot simply grow into because intensive. It could result in the work of the designers also becoming more schematized, and the leeway they have for solving the design problems could be restricted by the CAD programs themselves. ln connection with another rationalization strategy that can be observed in the case of single-piece work and customizing this could lead in a further Here, too, it is clear how important it is to differentiate according to the type of firm or production. In the case of the series producers, the problem hardly plays any role that forces the single-piece Producers and those producing custom work to produce a design that they present when they are making an offer; as a result, the same applies to the briefly sketched lines of rationalization. Authorized licensed use limited to: GUILIN UNIVERSITY OF ELECTRONIC TECHNOLOGY. Downloaded on March 05,2010 at 00:18:17 EST from IEEE Xplore. Restrictions apply. 292 IEEE TRANSACTIONS ON ENGINEERING MANAGEMENT, VOL. 36, NO. 4, NOVEM

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