Available online at www.sciencedirect.com ScienceDirect Procedia CIRP 15 (2014) 207 – 211 21st CIRP Conference on Life Cycle Engineering An Evaluation Method Based on Mechanical Parts Structural Characteristics for Proactive Remanufacturing Xuan Zhoua,*, Qingdi Kea, Shouxu Songa, Ming Liua a School of Mechanical and Automotive Engineerin, Hefei University of Technology, No.193 Tunxi Road, Hefei, 230009, China * Corresponding author Tel.: +86-15256028667; fax: +00-86-0551-62901775.E-mail address:1991zhouxuan@163.com Abstract Currently, due to the uncertainty of operation loading and service time, sometimes the mechanical parts are difficultly or hardly to be remanufactured On the otherwise, it is also wasteful to remanufacture these parts too early In remanufacturing, a large number of inspections and evaluations of failure condition in the parts have to be done, which are uneconomical and inefficient In this paper, the concept of proactive remanufacturing is given, with considering remanufacturability in the initial design stage of parts Analyzing the performance deteriorating law, one main characteristic of proactive remanufacturing is the best timing point to be remanufactured Informed by modular design theory, structural characteristics are extracted, and the mapping relationship of design parameters and remanufacturability of parts is established Moreover, the proactive remanufacturing factor is hierarchically and qualitatively expressed as a comprehensive index to measure parts overall remanufacturability, which can implement the design parameters feedback to adjust the best timing point to avoid one-sided optimization of design parameters Finally, an engine crankshaft is given as an instance to validate this method © Published byPublished Elsevier by B.V This is an open access article under the CC BY-NC-ND license © 2014 2014 The Authors Elsevier B.V (http://creativecommons.org/licenses/by-nc-nd/3.0/) Selection and peer-review under responsibility of the International Scientific Committee of the 21st CIRP Conference on Life Cycle Selection and responsibility theTerje International Engineering in peer-review the person of under the Conference Chair of Prof K Lien Scientific Committee of the 21st CIRP Conference on Life Cycle Engineering in the person of the Conference Chair Prof Terje K Lien Keywords: Uncertainty; Remanufacturability; Proactive Remanufacturing; Structural Characteristic Introduction Remanufacturing engineering is a series of technical measures or engineering activities made to restore the retired electromechanical products, with considering the whole life cycle design and management of electromechanical products, aimed at achieving the performance improvement of electromechanical products, taking high-quality, high efficiency, energy-saving, material-saving and environmental protection as principles, and taking advanced technology and industrialization production as means[1] Domestic and overseas engineering applications show that both performance and quality of remanufacturing products can reach and even above the originals’, meanwhile the cost is only one third of the new one, with saving 60% energy, and 70% materials, and decreasing the negative impacts on the environment [2] However, not all of the retired electromechanical products can be remanufactured The precondition of remanufacturing is that the parts keep a good status of remanufacturability at the end of life cycle Zhang Guoqing et al developed an assessment model for remanufacturability based on the assimilability assessing model, consisting of two modular constructions: technological module and economical module [3] Zhang Zongxiang et al analyzed the influential factors of the remanufactureability on the basis of characteristics of product, and determine the hierarchical and structural relationships between each index and the calculation formula of each index [4] Zeng Shoujin et al established a micro assessment model, a macro assessment model and a comprehensive assessment model of green remanufacturing for waste electromechanical products by analyzing TOERE, energy sources, time and service ability factors[5] Due to the uncertainty of service time and performance of used products, it is usually to remanufacture the “over-used” product which means higher cost or even can't be remanufactured On the other hand, it will be “previous 2212-8271 © 2014 Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/) Selection and peer-review under responsibility of the International Scientific Committee of the 21st CIRP Conference on Life Cycle Engineering in the person of the Conference Chair Prof Terje K Lien doi:10.1016/j.procir.2014.06.095 208 Xuan Zhou et al / Procedia CIRP 15 (2014) 207 – 211 remanufacturing” which means a huge waste [6] The current main solution is to conduct inspection and testing, which is uneconomical and inefficient Whether the product could be remanufactured and the remanufacturing performance is good, it depends deeply on the design stage [7-9] To meet this issue, the concept of proactive remanufacturing is presented in this paper It is to take remanufacturability as an important product performance into account in the initial design stage From the perspective of modular design, structural characteristics are extracted to represent the overall parts structures, based on which the relationship of design parameters and mapping remanufacturability of parts is established And then, through the hierarchical and qualitative analysis, the proactive remanufacturing factor is introduced as a comprehensive index to measure parts overall remanufacturability As a result, the proactive remanufacturing can be conducted in an appropriate time to obtain the maximum economic benefit, with ignoring the uncertainty of used products The concept of proactive remanufacturing and the best timing point Nowadays, the process of products remanufacturing normally consists of four key stages [10]: Disassembly/Cleaning, Inspection/Grading, Reprocessing, and Reassembly/Testing, as shown in Fig.1 Due to the uncertainty in performance status of remanufacturing blank, inspection and grading of every unit is an essential and massive work before which meanwhile limits the remanufacturing, remanufacturing industrialization Used products being longest as principles There are three important characteristics of proactive remanufacturing [11]: x Proactive Instead of conducting remanufacturing after products being retired, the timing is determined in advance, through comprehensive decision method When reached the time, the product should be remanufactured actively x Batched Proactive remanufacturing reduced the uncertainty of blanks As a result, the products can be remanufactured in batches, which made a great increase in efficiency x Objective The performance of products with the same design scheme and batch will decrease Then the timing exists objectively to achieve comprehensive optimum of indexes in product life cycle 2.2 The best timing point Determined by the performance deteriorating law of parts, there exists the best timing point, T0, at which conducting remanufacturing is most appropriate in both technologically and economically, as shown in Fig.2 Performance D’(t) Remanufacture H(t) D Disassembly/Cleaning t=T0 Inspection/Grading Reprocessing Reassembly/Testing Remanufactured products Time Fig Performance deteriorating curve of parts (Before and after remanufacturing) Illustrational, D refers to the design performance; D’(t) refers to the generated performance damage after service time t After conducting remanufacturing at time t, the performance recovery capacity is H(t), then figure out the total performance of new life cycle is D-D’(t)+H(t) Pi is selected as the index to measure the remanufacturability of some structural characteristic, and then Pi is defined by [12], Di - D 'i (t ) H i (t ) D 'i (t ) Fig Key process of products remanufacturing Pi 2.1 Proactive remanufacturing (1) where, i=1, 2, , n When t=T0, it is the most appropriate time to conduct remanufacturing in both technologically and economically Assumed that the given service life of parts is Tg, from the perspective of proactive remanufacturing and optimization, there should be T0=Tg The given service life, Tg is determined by the design requirements, which cannot be changed usually Proactive remanufacturing is a series of engineering activities made to implement the remanufacture of products actively at some point during the service time, aimed at guaranteeing products’ function and performance of the original design, and taking high-quality, high efficiency, energy and material saving, environmental protection and the total service time 209 Xuan Zhou et al / Procedia CIRP 15 (2014) 207 – 211 Thus, T0 should be variable to get approach to Tg By changing design parameters, T0 can be adjusted Structural Characteristics and the proactive remanufacturing factor The remanufacturability, design information, service performance and failure modes are interrelated In this paper, from the perspective of modular design [13-15], the overall parts structures can be represented by several structural characteristics (Si) Thus, the change of T0, namely the change of remanufacturability at the end of life cycle can be achieved by changing design parameters of structural characteristics 3.1 Structural characteristics Parts Database, Design Database, Statistical Database, Failure Statistics, Empirical Analysis, Bench Test, Analog Simulation, ĂĂ Modularization Model Characteristic Extraction Parts S1 S2 Sn ωi Pi ωi Pi ωi Pi According to the failure statistics, empirical evaluation and theoretical analysis, Si can be selected from the weak or unstable structures, which are prone to functional failure For example, as to shaft components, since structural strength is deeply affected by journal and fatigue failure are prone to occur in shaft shoulder and transition fillet because of stress concentration Si can be selected from the journal, shaft shoulder and transition fillet (3) where, i=1, 2, , n ωi can be figured out with the method, Fuzzy Analytical Hierarchy Process (FAHP) [17] fAR is a comprehensive index to measure parts overall remanufacturability When fAR>1, it refers to that the part has a good status of remanufacturability at the end of life cycle, and can be remanufactured The larger fAR is, the better the overall remanufacturability is Apparently, the flow chart of evaluation method based on structural characteristics can be described, as shown in Fig.3 Functional Requirements Design Parameters Feedback Tg Approach to T0 Design Information Model fAR Comprehensive Index 3.2 The proactive remanufacturing factor Fig Flow chart of evaluation method based on structural characteristics Generally, according to theory of “Buckets effect”, the overall performance is determined by the length of the shortest board [16] In order to improve parts performance, the design parameters of weak structures, namely the short board is the object to be optimized However, from the overall perspective, due to different structures being closely interrelated, the interaction effects between different structures may cover or distort the main effect of single structure, resulting in that the one-sided pursuit of optimization of each single structure may not achieve the expected overall improvement of performance Due to the influence degree of Si on overall performance are different, directive comparison of Pi is of no use By reference to the fuzzy comprehensive evaluation, a comprehensive index, the proactive remanufacturing factor (fAR) is proposed in this paper to measure parts overall remanufacturability Assumed that there are n structural characteristics, then after t, the proactive remanufacturing factor (fAR) is defined by: It's important to note that fAR is mostly aimed at single component For products with several components need to be remanufactured, the life time of different components should be matched With the evaluation method proposed above, the best timing point T0 of different components should be adjusted in cooperative relationship, such as being equal or multiple, to achieve the overall optimization More researches will be done about this problem f AR F ^S1 S2 Sn ` F P1 P2 Pn f AR F P1 P2 Pn > P1 P2 The crankshaft is a core part of automobile engine; the crankshaft remanufacturing has great research significance and economic benefits In this paper, the crankshaft of a sixcylinder engine is taken as the research object to validate the effectiveness and feasibility of the method above 4.1 Determination of Si and ωi The main failure modes of crankshaft are fatigue fracture, wear and bending-torsion deformation If the crankshaft is fatigue fractured or having potential cracks after testing, it cannot be remanufactured Then, the crankshaft will generally be material recycled through melting treatment Besides, it is supposed that the wear on the crankshaft can be completely repaired under current technology With the aid of Heavy Engine Remanufacturing Company, n an abundant Statistic Database about crankshaft is obtained Zi Pi After failure statistics, empirical evaluation and theoretical i analysis, eight structural characteristics as selected They are, respectively, S1- Diameter of journals, S2- Aperture of oil hole, S3- Radius of transition fillet, S4-Tortuosity of journals, (2) For achieving the quantitative comparison of remanufacturability, the weighting factor (ωi) is introduced to conduct the equalization processing of each structural characteristic And then, the influence degree of part,ωi•Pi are equal and comparable Thus, fAR can be described by: ê Z1 ôZ ằ Pn @ ô ằ ô ằ ô ằ ơZn ¼ Case study ¦ 210 Xuan Zhou et al / Procedia CIRP 15 (2014) 207 – 211 The relative weighting comparisons and ωio of structural characteristics are shown in Table And then, conducting normalization processing of ωio above, ωi is figured out, as shown in Table S5-Cylindricity of journals, S6-Circular run-out of journals, S7Parallelism between journals and S8-Axial clearance According to Fuzzy Analytical Hierarchy Process, after multiple comparisons, listing the comparison matrix, calculation, and then quantization of comparison, the original weight (ωio) of each structural characteristic is figured out Table Relative weighting compositions and ωi of structural characteristics Si Journal Oil hole Fillet Tortuosity Cylindricity Circular run-out Parallelism Axial clearance ωio Journal 3/4 1/2 4 1.62239 Oil hole 4/3 3/4 4 2 1.83400 Fillet 4/3 4 4 2.46549 Tortuosity 1/4 1/2 1/4 1 0.70710 Cylindricity 1/4 1/4 1/4 1 1 1/2 0.54525 Circular run-out 1/4 1/4 1/4 1 1 1/2 0.54525 Parallelism 1/4 1/2 1/4 1/2 1 1/2 0.54525 Axial clearance 1/2 1/2 2 1.09050 ωi 0.1734 0.1960 0.2635 0.0756 0.0583 0.0583 0.0583 0.1166 4.2 Determination of Pi Pi is an index used to measure the remanufacturability at the end of life cycle, the selection of Pi is universal According to different requirements, the appropriate indexes are selected As to engine crankshaft, since the main failure modes of crankshaft are fatigue and wear, fatigue life and wear loss can be chosen as the performance indexes It is supposed that the wear on the crankshaft can be completely repaired under the current technology Therefore, the fatigue failure of crankshaft is considered merely in this paper; further, selecting fatigue strength representing Pi from the perspective of structural strength Combining fatigue analysis by FE-SAFE with the Statistic Database provided by Heavy Engine Remanufacturing Company, Pi is obtained, as shown in Table Table Pi of structural characteristics Si Pi Journal 1.322 Oil hole 1.618 Fillet 1.878 Tortuosity 0.832 Cylindricity 0.593 Circular run-out 0.352 Parallelism 0.687 Axial clearance 0.609 Calculating the proactive remanufacturing factor, fAR: f AR F P1 P2 P8 > P1 P2 ê Z1 ôZ ằ P8 @ « » « » « » ơZ8 ẳ =0.1734ì1.322+0.1960ì1.618+0.2635ì1.878+ 0.0756ì0.832+0.0583ì0.593+0.0583ì0.352+ 0.0583ì0.687+0.1166ì0.609 =1.2703 Ư Apparently, fAR>1, it refers to that this crankshaft has a good status of remanufacturability at the end of life, and can be remanufactured Further, by changing the design parameters of structural characteristics, the best timing point, T0 gets approach to Tg Conclusions (1)Through proactive remanufacturing, the uncertainty in performance status of retired electromechanical products can be largely reduced, and it helps to avoid remanufacture the “over-used” product and “previous remanufacturing” as well Based on structural characteristics of parts, the proactive remanufacturing factor, fAR is presented to measure parts overall remanufacturability (2)Through structural characteristics, the mapping relationships of design parameters and remanufacturability of products is established, which provide a way to get T0 approached to Tg As a result, the proactive remanufacturing can be conducted in an appropriate time to obtain the maximum economic benefit (3)This design method can be applied in different parts, and the selection of remanufacturability index is diverse according to different requirements However, this design method still needs further improvement, especially on the extraction and calculation of index, and the determination of Pi (4)With this method proposed, retired products can keep similar remanufacturability at the end of life cycle, which avoids the inefficient inspection of blanks and provides feasibility to realize industrialization (5) In this paper, fAR is mostly aimed at single component For products with several components need to be remanufactured, further researches on life matching of Zi Pi different components are required i Acknowledgements This research is supported by National Basic Research Program of China (973 Program, 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maximum economic benefit (3)This design method can be applied in different parts, and the selection of remanufacturability... Engine Remanufacturing Company, n an abundant Statistic Database about crankshaft is obtained Zi Pi After failure statistics, empirical evaluation and theoretical i analysis, eight structural characteristics