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College of Automation，Chongqing University，Chongqing 400044，P.R.China

（Received 10 July 2019；revised 13 March 2020；accepted 15 March 2020）

Abstract: An increase in public environmental awareness and pressures from the government’s determination to deal with environmental problems force manufacturers to implement green manufacturing （GM）. However，since managers and stakeholders lack understanding of GM and its complexity，the manufacturing enterprise，especially the small and medium ones，are constantly facing the problems of how to make a reasonable decision for an environmental problem，and the adopted approaches have no clear payoffs. The customized design，flexible production，and diversified services in customized production make the problems more challenging. In order to solve this problem，this paper proposes a framework for the implementation of GM in customized products manufacturing enterprises（CPME）. A three-layer framework，i.e.，the goal layer，the product life-cycle layer and the supporting layer，is designed to provide a methodology to help implement GM. In this model，the GM practice processes are divided into four stages from the life-cycle perspective，i.e. design，production，use，and disposal. The preliminary practice of GM in an electrical product manufacturing company is carried out，and the implementation effect shows that the system framework is helpful to make a comprehensive understanding of GM and to improve the operability of GM practices.The integrated product model is an effective way to integrate the life cycle data.

Key words：green manufacturing；implementation；system framework；customized production

0 Introduction

Green manufacturing（GM）has been praised in recent years for its significant benefits in social，environmental， and financial aspects. With the growing environmental awareness and a series of en⁃vironmental laws，regulations，and standards，the manufacturing companies are enforced to perform GM. However，for the manufacturing companies，especially small and medium ones，a strong obstacle is lack of understanding of GM.

Recently，implementation models and methods have become important due to the complexity of GM. Allen et al.［1］studied the implementation strat⁃egy，methods and driving force of GM，and prac⁃ticed at leading firms in Europe，Japan and the Unit⁃ed States. They believed that a framework is an identified priority. Juan and Enrique［2］proposed a strategic framework，and divided the GM practices into four aspects：The analysis of business needs，the strategy，process control，and the results angli⁃cizing.Tan et al.［3］proposed a decision-making mod⁃el for GM，in which the objects of quality，cost and environmental impact were considered together.Deif［4］presented a system model for the new green manufacturing paradigm. Reich et al.［5］defined the specific using cases，and the developed frameworks of GM were suited. Abhijeet et al.［6］developed a structural relationship among different factors for the successful implementation of GM. Shankar et al.［7］proposed a framework to achieve GM in an In⁃dian context. United Nations Environment Pro⁃gramme［8］introduced more GM practices and de⁃scribed the strategies，methods，operating model，and application tools. These studies have played an important role in guiding and promoting GM practic⁃es and also laid the foundation for deepening the study. However，there are barely enough system guidelines to present a whole understanding and to guarantee the successful implementation of GM in customized products manufacturing enterprises（CPME）. With the rapid development of manufac⁃turing technology and information techonology（IT），the customized production（CP）has become a dominant type of production［9］.

The goal of CP is to provide sufficient diversi⁃ty，individuality，good enough quality，and accept⁃able prices. Generally speaking，the special needs for CPME to implement GM are as follows.

（1）During the early design phases，only func⁃tional requirements and product concepts are avail⁃able. The range of candidate product scheme is usu⁃ally large. Both designers and consumers often con⁃fuse a“greener”product design scheme with many selections. Therefore，the green design method needs to be improved.

（2）At the stage of manufacturing，the irratio⁃nal operational plans often exist in order to im⁃prove production flexibility. Meanwhile，the re⁃source utilization is not optimized. Therefore，the reasonable scheduling and the optimization of pro⁃duction processes are necessary to improve re⁃source utilization and reduce the negative impact on the environment.

（3）At the stage of application，the diversifica⁃tion and personalization of products complicate the maintenance. Therefore，the maintenance staff want to know more information about the product in order to improve maintenance efficiency.

1 Implementation System Frame⁃work

1.1 System framework

The issue of implementing GM is to build a GM system. The framework describes the common features of the GM system. The prototype can help people recognize and analyze the essence of the GM system，design or adapt the GM system. The role of a system framework is to provide reference and guidance for practicing GM in CPME. To address these special needs of CPME，this paper proposes a framework for the implementation of GM in（Fig. 1）. This framework includes three layers，i.e.，the goal layer，the product life-cycle layer and the support layer. In this model，the GM practicing processes are divided into four stages from the lifecycle perspective.，i.e. design，production，use and disposal.

Fig.1 A system framework for the implementation of GM in CPME

（1）Goal layer

The goal layer attempts to highlight the imple⁃mentation objectives and decision-making objec⁃tives. Implementation objectives provide an over⁃view of the development goals of the enterprise and the goals of each specific implementation aspect. De⁃cision-making objectives consider the target function and decision variables.

（2）Product life cycle layer

The product life cycle layer mainly describes the product life cycle processes，which mainly has two functions. Firstly，it is to divide implementation aspects，decompose the implementation tasks，and clarify the technology and methods. Secondly，it can be used to analyze and evaluate resource con⁃sumption and environmental impact on the whole life cycle stages，and to identify the serious prob⁃lems and the implementation of focus clearly. The product life cycle processes in this model include four stages，which are design，manufacturing，use，and disposal［10］. The life cycle information is inte⁃grated by a product model.

（3）Support layer

The support layer provides basic support for the entire GM operation which includes the informa⁃tion system and network，etc. It describes the tech⁃nical structure of implementing GM，the organiza⁃tional structure of enterprises，industry standards，laws and regulations，market and information sys⁃tems，etc.

1.2 Practice strategy

The practice strategy clarifies the principles and methods to carry out the GM，which is the core and key to guide GM practice. In 2001，the commis⁃sion of the European Union presented a strategy，called integrated product policy（IPP），for strength⁃ening and refocusing product-related environmental policies，which aims at promoting the development of a market for greener products and，ultimately，stimulating public discussion on this topic［11］. In IPP，the manufacturing enterprises are required to improve the environmental performance of products in the five aspects，waste management，develop⁃ment of energy-saving products，green product inno⁃vation，environmental responsibility，and environ⁃mental information exchange，and three principles，market-oriented， product information integrating and life-cycle perspective of GM practice［12］.

According to the previous analysis，a GM prac⁃tice strategy is proposed，as shown in Table 1，The operability is improved by dividing the complex implementation problem into four aspects from the life-cycle perspective. These four aspects are linked by the integrated product model. The integrated product model integrates the whole life cycle infor⁃mation.

Table 1 A green manufacturing strategy

1.3 Integrated product model

The integrated product model is essentially a description of the product data structure. Besides the basic information，it integrates the environmental impact information of constituent parts and the pro⁃cess information in different stages of the life cycle.For example，Part1 is a part of the product. Then we can not only get basic information，such as mate⁃rial，weight，structure of Part 1，but also obtain the process data，equipment information，environmen⁃tal impact indicators，and assembly/disassembly in⁃formation. The integrated product model can be di⁃vided into the following three layers.

（1）Core layer

The core layer contains basic information that is generally generated in the product concept design stage according to customer demand. Once generat⁃ed，it is seldom modified. Only if the customer de⁃mands are changed，it will change. Therefore，it has relatively static stability. This basic information includes manufacturing objectives，customer needs，overall parameters，and performance［13］.

（2）Extension layer

The extension layer includes the information of the product in different life cycle stages. Its specific contents are retrieved dynamically by searching the related information of the different stages according to the product scheme. For example，the extension layer includes the related information of product modules，components，materials in the detailed de⁃sign stage，the related information of manufacturing resources，process data and assembly methods in the production stage，the related information of de⁃bugging，installation and maintenance in the mainte⁃nance stage，the related information of demolition methods，disassembly sequence，and parts repro⁃cessing in the waste products reprocessing stage.

（3）Environmental data layer

Environmental data represent the resource con⁃sumption and environmental impact values of prod⁃uct composition components and process in the ex⁃tended layer，such as the amount of non-renewable resources，energy consumption，carbon emissions，and wastes［14］. It is the basis for analyzing and evalu⁃ating the environmental impact of various life stages of the product.

2 Case Study

We take an electrical product manufacturing company as an example to clarify the application pro⁃cess of the system framework. The products of this company are high⁃and⁃low voltage electrical switcha⁃gears. This product is mainly customized for engi⁃neering. Two urgent problems need to be solved：The first is that the surface treatment on the cabinet is producing serious environmental pollution；the other is that the plate waste is serious in cabinet body production because the workers cute the plate by experience.Therefore，we carried out the applica⁃tion analysis and preliminary practice of GM in this enterprise.

2.1 Life cycle analysis of electrical switchgears

An electrical switchgear is the power center and the power distribution unit which is used to con⁃trol and monitor power lines and electrical equip⁃ment. The life cycle process of electrical switch⁃gears is shown in Fig.2.

Fig.2 Life cycle process of switchgears

2.2 Switchgear body integrated information model

The core of the proposed implementation mod⁃el is an integrated product information model.Therefore，building an integrated product informa⁃tion model is the key to the implementation. Accord⁃ing to the design and manufacturing processes，the switchgear body integrated information model is es⁃tablished as shown in Fig.3. It is described by the EXPRESS language（the description fragment is shown in Fig.4）.

2.3 Improvement on cabinet production

2.3.1 Material optimization support system for cabinet production

The main parts of the cabinet are skeleton，shell，and partitions，and the material is rod or plate.In the existing production process，the workers cut the plate by experience.Therefore，the material utili⁃zation rate is lower and the wastes are more. To solve these problems，the material optimization sup⁃port system for cabinet production was developed.This system not only improves the efficiency of the workers’cutting but also reduces material loss and saves resources.

Fig.3 The cabinet integrated information model

Fig.4 EXPRES description of the information model

2.3.2 Process improvement in cabinet produc⁃tion

The cabinet surface is treated to enhance and improve the surface properties. The treatment pro⁃cesses produce more wastes and cause serious envi⁃ronmental pollution. The major pollutants，national emission standards and experience value of emis⁃sions are shown in Table 2. Using the evaluation method proposed in Ref.［15］，the environmental impact of the treatment process is analyzed.

Table 2 The main emissions of the electroplating process

Suppose that the density function of emission（fi(x)） subjects to the uniform distribution on[ai，bi]，then the density function of zinc isf1(x)=，and the quantization value is 8.5. Similarly，the quantitative value of other emis⁃sions can be drawn. Thus，we can create the envi⁃ronmental impact matrix of the cabinet electroplat⁃ing process of electrical switchgears. It is shown in Table 3，whereEIrepresents the value of environ⁃mental effect.

Table 3 The environmental impact analysis matrix

3 Conclusions

This paper presents a framework to help CPME implement GM. This framework is a sys⁃tematic and structural method to support managers and stakeholders to understand GM. It can improve the operability of GM practices by integrating life cy⁃cle information and the decomposition of the imple⁃menting problems. The integrated product model is essentially a description of the product life cycle da⁃ta. It can support the GM practice for each imple⁃menting stage by indexing related information of dif⁃ferent life cycle stages. This paper also presents the applicability of this framework through the prelimi⁃nary practice of GM in an electrical product manu⁃facturing company.

From the practice，this paper gains the follow⁃ing insights：

（1）The material optimization support system can help the enterprise to improve cutting efficiency and to reduce the loss. This can increase enterpris⁃es’acceptance of implementing GM.

（2）An environmental impact assessment of the production process can clarify the main environmen⁃tal impact categories and help manager to make sci⁃entific decisions.

Some limitations of this paper are：（1）The framework has been implemented only in one manu⁃facturing enterprise，and（2）the implementation ef⁃fect evaluation is still qualitative. Future works in⁃clude：（1）to validate the applicability of this frame⁃work to more manufacturing enterprise，（2）to de⁃velop more quantitative methods，and（3）to en⁃hance the practicability of this framework.