International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 9, September 2017, pp. 167 172, Article ID: IJMET_08_09_017 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=9 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication Scopus Indexed EARLY COST ESTIMATION OF HAND PRESSURE MOP USING DESIGN FOR MANUFACTURE AND ASSEMBLY (DFMA) Gokul kumar K and Naiju C D SMEC, VIT University, Vellore, India ABSTRACT Design for manufacture and assembly, DFMA, is a set of tools or applications, when incorporated on a particular product helps reduce the number of parts,bring about a change in the material used, and even the process/operation used. This indirectly helps in the overall cost reduction of the product and hence improve the productivity on the whole. DFMA is usually used during the initial design stages of a product, so that if any changes can be brought about in the product to help improve its efficiency and cost, simultaneously, it can be done in the beginning itself. This helps the designer plan out his entire schedule for production of the product depending on its work volume. DFMA is a combination of two basic principles, namely, Design for Manufacture (DFM) and Design for Assembly (DFA). Design for manufacture helps to ease out the manufacturing processes used in the production cycle of a product, whereas, Design for assembly helps ease out the assembly line once done with the production stage. Improper design decisions are responsible for higher manufacturing cost for a product. Thus it is important to include DFMA by combining principles of both DFM and DFA principle early in the design process. This paper presents a case study of the manufacturing and assembly cost s estimation during the design stages of a hand pressure mob, with the help of a DFMA tool. Keywords: DFMA, Design for manufacture, Design for assembly, Product Design. Cite this Article: Gokul kumar K and Naiju C D, Early Cost Estimation of Hand Pressure Mop Using Design for Manufacture and Assembly (DFMA), International Journal of Mechanical Engineering and Technology 8(9), 2017, pp. 167 172. http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=9 1. INTRODUCTION According to P. Dewhurst et al [1] design for efficient manufacture will consist of two steps, i.e. identification of the appropriate materials, manufacturing process for component parts of a new product design and the detailed design of individual components consistent with the capabilities and limitation of the material combinations, conventional DFA is not usually sufficed for complex assemblies as it omits the sequence of choice and partitioning of subassemblies. Assembly sequence analysis is used as a basis for complex assembly DFA. ASA can expose all assembly issues and also pin point DFA redesign candidates [2]. In the http://www.iaeme.com/ijmet/index.asp 167 editor@iaeme.com
Gokul kumar K and Naiju C D development of a product, the design part is seen to be the least expensive among other stages. DFMA for CAD and CAM systems have helped improve these attempts immensely [3]. Design for manufacture (DFM) is mainly about integrating the manufacturing aspects during the design phase. Designing hybrid modular products can increase sales in a competitive market and those designs are taken as 3-D puzzles and best manufacturing process are used to evaluate the further information [4]. Balancing, in the assembly line design is one topic that has been drawing the attention of the researchers. Various algorithms have been designed for analysis of single, multi and mixed assembly lines. The DFMA methodology starts with selection of a suitable assembly line selection. The end result of all these operations is detailed design of manufacturing assembly line [5]. DFMA methodology has two main aims, them being: First, to guide the designer with defining the requirements of design and second to help the designer evaluate both the technical and economic viability.[6]. In the manufacturing of a product choosing the right process is a key parameter. Most often, this choice is based on previous experiences. A systematic process to select the manufacturing process in the making of a product, must be approached. The method also helps decide shaping of two diverse components [7]. Food processing is a function that requires acute and strategized assembly operations, considering that, DFMA can be integrated into mechanical conveyor systems to help reduce costing levels [8]. Application of Design for Manufacturing (DFM) and Design for Assembly (DFA) methodologies can be beneficial to industries involved in the design and development of products. Improper design decisions are responsible for higher manufacturing cost for a product. [9]. 2. HAND PRESSURE MOP: A CASE STUDY A mop is an implement made of absorbent material fastened to a handle and used especially for cleaning floors. It is a mass or bundle of coarse strings or yarn, etc., or a piece of cloth, sponge, or other absorbent material, attached to a pole or stick. It is used to soak up liquid, for cleaning floors and other surfaces, to mop up dust, or for other cleaning purposes.a mop with the function of dewatering the yarns by twisting in a single direction via an up-and-down linear motion is used for the DFMA analysis. It comprises of the following parts with respect to its assembly- An internal rod, an external rod having a bottom portion in a telescopic connection with a top portion of the internal rod, an engaging element positioned within the opening at the top of the internal rod along with a driving element formed in an elongated shape and positioned within the external rod in such a way that the driving element is moved up and down synchronically with the external rod. An actuating element positioned within the engaging element for accommodating the driving element, the engaging element being driven in a single direction when the actuating element is rotated by the driving element. Consists of a disc body secured to the bottom having mop yarns. The CAD model of the hand mop is given below in fig 1. The locking mechanism mounted on the external rod for locking the internal rod and the external rod in place or for unlocking them in a telescopic state consist of a process where the actuating element is rotated by a linear motion of the driving element. http://www.iaeme.com/ijmet/index.asp 168 editor@iaeme.com
Early Cost Estimation of Hand Pressure Mop Using Design for Manufacture and Assembly (DFMA) Figure 1 CAD Model of Mop Part CAD Model Part CAD Model Part CAD Model Bucket External cap Threaded sleeve Basket External clamp driving element External rod Disc Actuating element Connector Part of engaging element Internal clamp Table 1 Parts and CAD Models of Mop http://www.iaeme.com/ijmet/index.asp 169 editor@iaeme.com
Gokul kumar K and Naiju C D 3. DFMA CONCURRENT COSTING To maintain their market position, leading manufacturers focus on improving products while lowering costs in the design-to-production cycle. Optimizing product design for manufacturing is a proven way to accomplish this goal. New Design for Manufacture (DFM) software from Boothroyd Dewhurst Inc., makes the task easy by allowing fast and accurate cost estimating at the design-concept stage. Table 2 gives us the detailed existing costs of the main parts of the hand mop. Table 3 gives us the summary of the costs of the same parts after it has been analysed and redesigned with respect to DFMA software guidelines. Table 2 Existing Concurrent Costing Using DFMA Part Cost per part ($) Part Cost per part ($) Basket 20.39 Driving element 10.37 Bucket 7.75 External clamp 0.85 Cap of extension rod 0.83 External lock 0.81 Connector pin 0.09 External rod 6.92 connector 0.48 Internal rod 4.8 Disc 4.20 Twist spring cap 0.28 Table 3 Final Concurrent Costing After DFMA Analysis Part Cost per part ($) Part Cost per part ($) Basket 11.05 Driving element 10.37 Bucket 4.74 External clamp 0.85 Cap of extension rod 0.74 External lock 0.81 Connector pin 0.09 External rod 6.92 connector 0.48 Internal rod 4.8 Disc 4.20 Twist spring cap 0.28 Table 4 DFA Summary Before DFMA Analysis Product life volume 10000 Number of entries (including repeats) 16 Number of different entries 16 Theoretical minimum number of turns 3 DFA Index 8.8 Total weight (lbs) 7.62 Total assembly labour time 99.55 Total cost for manufacture 58.74 Total assembly labour cost ($) 0.98 Other operations cost per product ($) 0.00 Total manufacturing piece part cost ($) 55.82 Total cost per product without tooling ($) 56.8 Fixture cost per product ($) 0 Manufacturing tooling cost per product ($) 2.92 Total cost per product ($) 59.71 http://www.iaeme.com/ijmet/index.asp 170 editor@iaeme.com
Early Cost Estimation of Hand Pressure Mop Using Design for Manufacture and Assembly (DFMA) Table 5 DFA Summary After DFMA Analysis Product life volume 10000 Number of entries (including repeats) 16 Number of different entries 16 Theoretical min no. of turns 0 DFA Index 0.0 Total weight (lbs) 7.16 Total assembly labour time 65.70 Total cost for manufacture 46,41 Total assembly labour cost ($) 0.64 Other operations cost per product ($) 0.00 Total manufacturing piece part cost ($) 43.38 Total cost per product without tooling ($) 44.02 Fixture cost per product ($) 0 Manufacturing tooling cost per product ($) 3.04 Total cost per product ($) 47.05 An overall summary of the entire product with respect to its part costs are given in table 4 before it has been analysed upon. Table 5 gives us the summary of the part costs of the product after the DFMA analysis has been conducted on the product. 4. CONCLUSIONS: On applying the design guidelines for manufacturing and assembly of a product, we can conclude that the cost of Hand pressure mop has been reduced from $59.71 to $47.05, which turns out to be approximately 20% reduction in the overall cost of the product. The redesigning of the product included: Alteration in the main raw material used for the casing of the mop, i.e., from Acrylonitrile butadiene styrene (ABS) to Polypropylene (PP). This change, helped ease the process of manufacturing. As it turns out, the cost of polypropylene is lesser than that of ABS hence reducing the overall cost of the product. Apart from that, the manufacturing process used was altered from the existing injection moulding process to structural moulding process for the bucket part of the mop as it helped reduce the cost. ACKNOWLEDGEMENTS The authors wish to acknowledge the School of Mechanical Engineering (SMEC) and Product Design Laboratory, VIT University for supporting and for carrying out the study. REFERENCES: [1] P. Dewhurst, G. Boothroyd: Early Cost Estimation in Product Design, Journal of Manufacturing Systems, Vol. 26, No. 7 (1994), p. 505-520. [2] Thomas L, Stephen J. R,Daniel.E. W: A Design-specific approach to design for assembly for complex mechanical assemblies, International Symposium on Assembly and Task Planning, Vol. 12,(1997),p.152-157. [3] R, Curran, G Gomis, S, Castage, J Butterfield, T Edgar, C Higgins and C McKeever: Integrated Digital Design For Manufacture For Reduced Life Cycle Cost, Int. J. Production Economics, Vol.109,(2007),p. 27-41. [4] Olivier. K, Pascal. M, Jean-Yves. H: A new DFM approach to combine machining and additive manufacturing, Computers in Industry, Vol. 62,(1992),p. 634-692. http://www.iaeme.com/ijmet/index.asp 171 editor@iaeme.com
Gokul kumar K and Naiju C D [5] Asar Khan, Andrew, J. Day: A Knowledge Based Design Methodology For Manufacturing Assembly Lines, Computers and Industrial Engineering, Vol.41,(2002), p. 441-467. [6] A. M. Lovatt, H. R. Shercliff: Manufacturing process selection in engineering design, Materials and Design, Vol.19,(1998),p. 217-230. [7] A. M. K. Esawi, M. F. Ashby: Development And Use Of A Software Tool For Selecting Manufacturing Process At Early Stages Of Design, Journal of Integrated Design and Process Science, Vol. 4,(1998), p. 27-43. [8] S. H. Masood, B. Abbas, E. Shayan, A. Kara: An investigation into desing and manufacturing of mechanical conveyor systems for food processing, International Jounral for Advanced manufacturing Technology, Vol. 25.,(2005), p 551-559. [9] C. D. Naiju, K. Annamalai, M. Mohan Prashanth, S. Karthik: Early Cost Estimate of Product during Design Stage using Design for Manufacturing and Assembly (DFMA) Principles,Vol.622-623,No.(2013),p.540-544. [10] Geetika Batra, Kuntal Barua, An Optimization of Effort and Cost Estimation by Code Reusability Concept, International Journal Of Computer Engineering & Technology (IJCET), Volume 4, Issue 5, September October (2013), pp. 251-257 [11] Parul Gandhi and Pradeep Kumar Bhatia, Evaluating Impact of Component Reusability with New Hierarchical Cost Estimation Model, International Journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 2, July- September (2012), pp. 526-532 http://www.iaeme.com/ijmet/index.asp 172 editor@iaeme.com